Lycoming XR-7755, 1946

Early 1946. Blackwood compiled a Lycoming XR-7755-1, -3, -5, -7 Contractual Data summary:
Contract No. W33-038 ac-564 (1943) – $1,571,575.00 – Partially finished parts for three engines; three rough forging sets, castings and bearings; single- and three-cylinder engine testing; component testing.
Contract No. W33-038 ac-564 (1944) – $2,080,000.00 – In addition to 1943 amount: Complete two engines and one spare set; provide additional single- and three-cylinder testing as well as XR-7755 testing; parts for two-speed dual-rotation reduction gearing.
Supplement No. 7 (1946) – $893,931.00 – Additional single-, three-cylinder and XR-7755 engine testing; reduction gear assembly and test.
Initiated Contract Change – (no price change) – Development and testing curtailment except as required to complete 50-hr Flight Approval Test (AAF Spec XR0-28398A) on an XR-7755-1 or XR-7755-3.

Performance	shp	sfc	Physical Characteristics
Takeoff	5,000	0.70	Length = 121.35"
Military at 35,000 ft	5,000	0.70	Width = 60.50"
Maximum Continuous at 35,000 ft	4,000	0.42	Depth = 60.50"
Shaft Horsepower at Minimum sfc	2,000	0.37	Height = 66.50"
			Dry Weight = 6,050 lb
			Fuel Grade = 115/145

Design Features: The XR-7755-3 and -7 engines are flight engines are designed to have two-speed dual-rotation gearing. Reduction ratios are 2.83:1 and 4.06:1. This is a 36-cylinder liquid-cooled radial composed of four rows of nine cylinders each. The XR-7755-3 had a pressure carburetor while the XR-7755-7 had fuel injection. Cylinders were 6.375" bore x 6.750" stroke; compression ratio was 8.5:1.

Objectives and Applications: An engine of low specific fuel consumption and adequate power for long-range aircraft. No specific airplane application.

Status: The engine was in development. Two experimental engines and spare parts had been built. A 50-hr development test at 4,000 bhp had been accomplished.

In Report No. 962, detonation limited imep is 260 at 2,800 rpm and 271 at 2,600 rpm.

The PPL advocated development of a float-operated device to prevent engine lubricating oil aeration. [RG342 RD2311. XR-7755.]

15, 16 Jan 1946. Blackwood's hand-written pencil notes give an account of his visit to Lycoming. A Lycoming labor strike had suspended all XR-7755 part machining and assembly work. Work proceeded on the new building and XR-7755 testing. The 1-cylinder head was being set up for valve gear tests that would examine fatigue. In addition, a smaller supercharger impeller was being tested. The reduction gear setup was also being tested, along with the engine mounts.

Blackwood clarified several contract deliverables and schedule issues:

Data had been received but the report itself had not.
According to Lycoming Project Report No. 231 dated 20 Dec 1945, 1-cylinder reports had been shipped but MatCmd had not yet received them.
The design reports for Items 4 and 12-6 were in the works.
Lycoming was nearly ready to start work on Item 12-5; the propeller shaft would be available in about one month.
Crankcase, crankshaft, connecting rods and two cylinder blocks had be assembled on the 36-cylinder engine power section. All but two part sets for the remaining cylinder blocks were available and the last two would be available by the time the others had been installed. The accessory and supercharger sections were assembled and ready for run-in on the supercharger test rig prior to assembly onto the engine. The nose section was not yet assembled but two part sets were available and would require less than one week to assemble. No major assembly difficulties had been encountered, and except for the strike, the engine would have been ready to run by 1 Feb 1946.
Lycoming reported that the strike was still delaying the 36-cylinder engine's first run; second and third engines would be assembled in two to three weeks and running in five weeks after the strike ended.
Eight to nine draftsmen were working on the two-speed shift control to lighten and improve it.
Blackwood requested two-speed reduction gear test procedure and acceleration measurement details, along with provisions for measuring torque during operation.
Blackwood asked about the single-throw vibration test status. Lycoming stated that the knuckle pins used were softer than specified and that equivalent simulated manifold pressure was limited to 50 inHgA; the correct pins would have better fatigue life.
Why did the No. 4 cylinder bank have its coolant outlet on the exhaust side while all others were "vented properly"?
The cost report was 2-3 months late.

[Penciled notes by J.G. Blackwood. RG 342 RD2311 XR-7755, 1943-1948: 503-602 Conf and Tel Notes.]

14, 15 Jan 1946. Blackwood's subsequent memorandum report on the trip repeats some of the information in his notes but also adds more information. The labor strike that had started around 15 January had completely suspended all parts machining, parts testing, and assembling the first XR-7755. The Engineering group was still in operation as was construction on the new facility. Hence, work completion estimates were from the time the strike ended.

The first XR-7755 crankcase, crankshaft, connecting rods and two cylinder blocks had been assembled. All but two remaining blocks were expected to be available by the time the others were installed. The accessory case and supercharger section were completely assembled and to be mounted on the supercharger test rig for running prior to assembly on the engine. The setup for running-in the accessory section was expected to require about 1.5 days. The nose section had not been assembled, but all parts except two were ready for assembly and the two parts would require less than a week to assemble. No major assembly difficulties had been encountered and Lycoming projected completion in about two to three weeks. The first engine would have a direct propeller drive and would be run on the propeller test stand with a cut down propeller club.

In view of this parts status, Lycoming expected second engine buildup to begin in about four weeks. It would use the 1:1 reduction gear. The 0.56 reduction gear parts were the same as some used in the final dual-rotation reduction gear. All of these were scheduled to be through the machine shop in approximately five months. Therefore, the first engine suitable for dynamometer running with the 0.56 reduction gear, would not be available for five months. At about that time parts to start the dual-rotation nose-to-nose endurance test would be available.

Blackwood examined some of the special test setups:

A cylinder head and valve mechanism was being set up for endurance testing of the new cam shifting mechanism.
The connecting rod fatigue test setup had been in operation with limited loads. Modifications supporting full loads were being made.
The small-impeller coolant pump had been tested and had sufficient capacity for the engine.
The two-speed reduction gear shift mechanism setup featured one shaft fastened to an air-cooled engine that acted as a driving member; the other two-speed shaft was fastened to a flywheel on which was mounted a Prony brake. With this setup the two members could be accelerated or decelerated as the two-speed shift was performed. Functionality could be observed under simulated operating conditions or even under conditions much worse than any that would ever be encountered in flight. This rig had operated very successfully and about 500 shifts on the same part set had been accomplished.
A test fixture on which the engine mount, mounting housing and crankcase would be mounted included a hydraulic jack that would be used to load the mounting members. This fixture would also be used for mounting the crankcase and crankshaft to perform a crankshaft spin test.
The crankshaft fatigue test machine was idle awaiting the crankshaft test pieces that were still in the machine shop. Lycoming thought this test would resume in about a week.
Because the first-engine rear section was on the supercharger test rig, no supercharger testing was then occurring. Data from recent supercharger tests was being analyzed in order to plan a further testing program.

After the post-V-J-Day work stoppage, construction on the new facility had resumed during the first week January. Some interior installation work had been ongoing for a longer period. Practically all equipment was available for building completion. The dynamometers were being cribbed up in preparation for sliding them onto the test beds. The large dynamometer equipment and piping installation remained to be finished. Lycoming personnel estimated completion in May 1946. Most small single-cylinder dynamometers were in place.

The drafting room was at work detailing the two-speed reduction gear shift control, which was intended to make automatic and fool-proof the steps involved in ratio shifts so that once a decision to shift was made all that was required was reducing the throttle. The drafting room was also revising various parts to make them lighter and more refined.

Blackwood requested that Lycoming cost reports be submitted to the ATSC on a more current basis. [24 Jan 1946 Memorandum Report TSEPP-5-504-3252. Contract W-33-038 ac-564 on Development of the XR-7755 Engine, P350314.]

18 Mar 1946. Blackwood noted that the Lycoming workers' contract was pretty well settled, but wage rate was NOT settled. [Penciled notes by J.G. Blackwood. RG 342 RD2311 XR-7755, 1943-1948: 503-602 Conf and Tel Notes.]

20 Apr 1946. Posthauer at Wright Field reported that wage disagreement resulted in failure of Lycoming workers to sign the latest contract proposal; next discussions were scheduled for 25 and 26 Apr 1946. [Penciled notes by J.G. Blackwood. RG 342 RD2311 XR-7755, 1943-1948: 503-602 Conf and Tel Notes.]

25, 26 April 1946. Blackwood visited Lycoming and reported that the labor strike, which started on 15 Jan 1946, ended on 9 Apr 1946, and that appreciable progress was again being made on the project. The first 36-cylinder engine was being fitted with camshaft shift indicators, and the only remaining work prior to assembly on the test stand was to install the accessory case and nose assemblies. The accessory case was being run-in separately and one part for the nose was to being completed on 26 April. The accessory case was mounted on the supercharger test rig and was on test. A five-hour run-in and eight hours of endurance testing at takeoff conditions had been accomplished:

Since then, a total of 15 hours endurance running had been accomplished. The only unsatisfactory conditions were a light scoring of the supercharger thrust washer and a leaky power takeoff drive seal.

Buildup of the second 36-cylinder engine was estimated to be about four months away. The parts status for it was as follows: crankcase = 90%; cylinder heads = 50%; accessory section = 90%. Machining for this engine's 0.56 reduction gear had been subcontracted and was promised in six weeks. The crankcase and crankshaft for this engine were to be used for spin tests prior to engine assembly. Major third-engine parts were progressing well also. Engine installation on the propeller test stand was to begin on 8 May 1946, and testing was to start on 23 May, with a six-hour run-in schedule up to 4,000 hp.

The two-speed dual-rotation reduction gear units had been subcontracted to improve delivery and relieve some of the Lycoming machine shop load. It was estimated that six months would be required to complete two units and four additional months would be required for the nose-to-nose endurance testing. When this testing ended, the first two-speed dual-rotation unit could be assembled on a 36-cylinder engine; this was the same version that was to be used for flight engines. The two-speed shifting parts had undergone 500 endurance cycles mostly at a rate-of-speed-change of 400 to 500 rpm/second. This was representative of similar studies done on the Lycoming XH-2470. However, in an attempt to aggravate the shifting problem, 10 shifts were made at 1,100 rpm/sec from low to high propeller and at 1,900 rpm/sec from high to low. Also, 85 normal shifts were made in a 25 minute period. No shifts were missed in any of this testing and the parts were in good condition. The only additional anticipated modifications was a slight chamfer on the low and high speed engagement gears to eliminate the very slight wear at that point.

One single-cylinder test engine was engaged in performance running and another on endurance. The latter was running tests on the latest cylinder design, but the most important thing on test were the McQuay-Norris piston rings. Lycoming's first choice had been Wilkening piston rings, which had the most test time. However, Wilkening had been uninterested in supplying larger quantities, which necessitated the crash program to qualify a second source. Lycoming was trying to bring other piston ring vendors into the program. A 150-hr endurance test pattered after the qualification test schedule of Specification AN9502b was to be started on a single-cylinder test engine in two to three weeks as soon as the 36-cylinder shiftable camshaft was available.

Blackwood pointed out to Lycoming, and Lycoming agreed, that fuel injection was almost a necessity for this engine. Single-cylinder tests had exhibited the knock limit and fuel economy superiority of fuel injection over carburetion; this would be even more pronounced in the 36-cylinder engine. The Bosch injectors had performed intermittently, failing to produce repeatable spray patterns, and the experimental equipment had not been of aircraft quality. Six Ex-Cell-O injectors were on order, promised in two to four weeks, and would be tested when they arrived. A new 36-cylinder intake manifold layout eliminated backfire screens and provided for port injection.

Design studies of the oil pressure pump inlet, outlet and housing. A larger, straighter inlet passage, more accessible inlet location and cleaner design had resulted from review of the original design. A one-piece crankcase with bolted-in diaphragms was also being studied.

Lycoming had planned on using a modified wooden test club of its own design to absorb power on the first direct-drive development engine. However, this club had developed a crack in its hub and was deemed unsafe for all but very low speed running. Lycoming requested that the ATSC try to find a club capable of absorbing 5,000 hp at 2,600 rpm; one had been located and would be loaned to Lycoming. In the mean time, Lycoming had ordered a club from Sensenich, but its long delivery schedule would probably delay testing. The metal club for use with the No. 70 shaft on the 0.56 reduction gear had been received. Lycoming had information that Curtiss was furnishing the 60L-80 dual-rotation unit without the front propeller being controllable, which countered what the ATSC had told Lycoming earlier. This feature was essential to Lycoming's plans of conducting preliminary shift control tests on the two-speed drive.

Blackwood, in an undated hand-written note had projected remotely controllable test propellers by 1 Sep 1945 and remotely-controlled dual-rotation props by June 1946. At that time, Vonderkeit was checking on a remotely-controlled No. 70 test club from Curtiss, but was dubious over an August 1945 delivery date. Vonderheit had a No. 60-80 club, the aft propeller was adjustable, the fore prop was remotely controllable. Shaw, from McGee's office related that a No. 60-80 flight propeller was under development, but not high priority; delivery was promised for February 1947. [Penciled notes by J.G. Blackwood. RG 342 RD2311 XR-7755, 1943-1948: 503-602 Conf and Tel Notes.]

The ATSC was looking into the test propeller disconnect.

The new laboratory status was as follows:

One 3,650 hp dynamometer was about 75% complete and was expected around the end of May. The other three were promised for the end of June.
The 7,400 hp dynamometer interconnecting shaft was promised for the week of 1 May 1946. This would connect the 5,000 hp and 3,400 hp dynamometers in series. Since the dynamometers were in place, the bedplates would be grouted once the interconnecting shaft was installed. Instrumentation for this test stand was being installed, and a 15 Jul 1946 operational date was anticipated. The Lycoming BX engine would be used for checkout.
The single-throw crankshaft test apparatus for imposing bending steady torque and vibration torque was running in the new laboratory. The coolant pump test setup was operational and would also be used to test oil pressure and scavenge pumps. Lycoming would next concentrate on the master rod-link rod strap test fixture. The fatigue test machine for the fatigue room was promised for 15 May 1946. The carburetor and fuel injection room was complete except for slight modification and final equipment location. The stresscoat room was complete and soon to be operational. The ignition room had no equipment installed. The vibration room was complete, equipment was installed and power was being run. The general contractor was almost finished with the building, its main equipment, power and piping installations. All electrical circuits were to be energized during the week of 1 May.

The older building in which test fixtures, tear-down and build-up rooms, and offices were located was being reworked to accommodate office space. At the same time, single-cylinder testing was ongoing, making the transition period difficult.</ol> [24 May 1946 Memorandum Report TSEPP-503-3269. Contract W-33-038 ac-564 on Development of the XR-7755 Engine, P350441.]

(Note: the following disorganized stream-of-consciousness collection of conference talking points and notes covering eight years will hopefully gain organization as additional information is uncovered by this writing process.)

9 May 1946. Telephone conversation with Lycoming's Carpenter. The 36-cylinder engine was put on the stand on 8 May 1946 and setup was ongoing. Lycoming estimated it would be ready to fire in 7 to 10 days. Crankshaft test pieces had been at 2,000,000 cycles and a crack had appeared at the root of a short spline tooth. The test was being run at takeoff equivalent conditions. Another identical piece was immediately run to determine the safe power limit; takeoff power may be temporarily limited to 4,000 hp. Lycoming was considering several alternative joint configurations, including four smaller bolts, one large bolt, and modified teeth.

In the preparation for an undated Routing and Record sheet to the Propeller Laboratory. Blackwood referenced Lycoming Technical Report No. 1002 (title not stated) and asked that the Propeller Laboratory study the report and provide comments on the procedure and feasibility of the proposed two-speed propeller drive shifting mechanism. Lycoming was proceeding with this propeller drive scheme, which was planned for the first test two-speed stand engine, a dual-rotation drive with a test club; this was 10 months away. MatCmd had determined that the Lycoming shift scheme was adequate for the task at hand. A 26 Jul 1946 letter to Lycoming stated t hat a dual-rotation propeller with rear propeller adjustment and front propeller remote control was available. In a 28 Feb 1946 letter, MatCmd stated that the injection program was a necessity. Lycoming was contracting parts to available vendors in order to assure quicker delivery. In Report No. 961, Lycoming proposed the use of a low-tension ignition system, a substitution to which Lycoming agreed. Lycoming report Nos. 237, 259 and 961 concerned failed camshaft bearing caps. Stress coat investigation was to proceed. Lycoming was working up rolled-thread strength tests, presumably for the crankshaft bolts, and also researching graphite coated pistons from J.J. Wills, ALCOA and Cleveland.

Some potential future programs were discussed, including water and dimethylamine injection to boost takeoff rating and for better cruise economy; apparently the theory was that the combination would allow more spark advance and higher cruise power.

Lycoming Report No. 962 explored the use of higher bmep, potentially 260 psi at 2,800 rpm and 271 psi at 2,600 rpm. The accessory case had been run in for 5 hrs at full speed; there was apparently minor trouble with thrust bearings and seals. Bosch was to have a speed-density control available soon. The XR-7755 was to be on the test stand by 9 May 1946 and on test by 23 May. After about 6 hrs running, it was to be removed from the stand and torn down for inspection.

Lycoming estimated the two-speed gearbox would be ready in 6 months, with 4 more required for tests to complete the item. Spin tests were to be run on second crankcase and crankshaft prior to use on the second engine, which was expected in 8 months instead of 3. There was a choice of using parts for a second 4-cylinder engine but more probably on the second 36-cylinder engine.

The ongoing two-speed shift tests of over 600 hrs had been severe, with part of the testing done at accelerations three times greater than normal, all in an attempt to miss a shift and expose parts to enhanced endurance testing. The mechanism had survived well, with only a bit of chamfering on the balk ring and driving gears.

17 May 1946. The XR-7755 was first started after initially experiencing carburetor and ignition trouble. Ran for 1 hr up to 1,200 rpm. [Penciled notes by J.G. Blackwood. RG 342 RD2311 XR-7755, 1943-1948: 503-602 Conf and Tel Notes.]

6 Jun 1946. Blackwood visited Lycoming and observed the first XR-7755 operating on the propeller test stand. The engine had accumulated about 4.5 hrs running at up to 1,300 rpm with a wooden test club. An undrilled camshaft bearing oil passage had caused its failure with no other damage. Minor ignition and carburetor difficulties had been encountered and remedied. Blackwood observed for 35 minutes and declared the run quite satisfactory. The open exhaust stacks showed fairly even flames and distribution at 1,300 rpm, but excessive idle richness was observed, but largely corrected by an idle adjustment. The engine produced approximately 1,500 hp at 1,300 rpm and 26 inHgA manifold pressure. The engine was scheduled to continue a run-in schedule through 2,200 rpm and 4,000 hp, but this would be delayed until another propeller was received. The one in use was cracked, which resulted in the 1,300 rpm limit. A propeller shipped from Wright Field on 22 May 1946 was delayed by a rail strike and had not been located despite efforts by both Lycoming and Wright Field.

At some point after the first XR-7755 ran and during the building of the second XR-7755, Lycoming simplified the nomenclature; the "first XR-7755" became "#101" and the "second XR-7755" became "#102". From this point forward, the revised nomenclature that will be used.

One single-cylinder engine was in operation after having recently accomplished a 100-hr endurance test using a maximum equivalent rating of 5,000 hp and two 100-hr tests using a maximum equivalent ration of 6,000 hp. These tests were run on the same set of McQuay-Norris piston rings, which were in satisfactory condition after these tests. This was gratifying since Lycoming had been forced to install McQuay-Norris rings on the 36-cylinder engine with very limited test background after Wilkening, the original ring vendor, failed to supply rings. A spark plug test program was planned in an effort to choose better plugs than the Champion CR-341 plugs that have tended to foul in the 36-cylinder at the rich, low speed running that been accomplished.

Lycoming had presented a proposal for a compounded XR-7755 to the ATSC on 6 Jun 1944.

The new building was still progressing. The first single-cylinder engine test setup was expected to be completed in a week. The other three were to be completed within a month. Multi-cylinder dynamometer instrumentation had been completed and its stand was to be complete by the end of July. The coolant pump test setup was in operation. The connecting rod test fixture had been operated and inspected; it was to be built up using new parts to increase the rod loads to rated values. A multi-cylinder head had been set up and was to be endurance tested and studied in operation. The crankshaft test fixture was not in operation but had recently tested a single-throw piece with four clamp bolts smaller than had been used before to increase the face spline area (since ample bolt load was available.) This piece passed a 10-million cycle test at 90,000 lb/in bending torque, 120,000 lb/in static torque and 40,000 lb/in vibratory torque. It then developed a crack at 2-million cycles and 50,000 lb/in vibratory torque. This is an improvement over the former standard test piece. Another test piece incorporating a single large bolt is ready except for special wrenches required to tighten that bolt to the required elongation.

Blackwood opined that "Lycoming should be complimented for the thoroughness and planning which have gone into this development to permit initial XR-7755 engine assembly and initial running with such an unusually small amount of difficulty. It is felt that this in itself is quite an accomplishment regardless of development problems which may be expected to arise as the engine accumulates test time." [11 Jun 1946 Memorandum Report TSEPP-503-3270. Contract W-33-038-AC-564 On Development of the XR-7755 Engine, P350446.]

25 Jun 1946. Jack Carpenter of Lycoming telephoned Blackwood to notify him that #101 had been running at 2,100 rpm, the equivalent of 3,100 hp, for about 1 hr. The test team next planned to run it at 2,200 rpm, the equivalent of 3,500 hp. Total time running was then between 8 and 10 hrs. General Electric was cooperating on a compounding study.

1 Jul 1946. Fred Jones of Lycoming telephoned Blackwood to inform him that the two-speed control tests were complete and the unit was being torn down. [Penciled notes by J.G. Blackwood. RG 342 RD2311 XR-7755, 1943-1948: 503-602 Conf and Tel Notes.]

10, 11 Jul 1946. Blackwood visited Lycoming and examined parts of #101, which had been disassembled after its 15-hr run-in period.

All major parts had passed magnaflux inspection and the engine was in generally good condition except for the following:
1. Two Row B knuckle pins were severely scored and others throughout the engine showed initial distress; a general lack of knuckle pin lubrication was indicated. A test setup was being prepared to measure oil pressure at the pins. The crankshaft oil squirt holes were to be reduced in size so that a greater oil supply was available for the knuckle pins.
2. As a result of particles from the knuckle pins, Row B pistons were slightly scored, but not enough to damage the cylinder barrels.
3. A light spot was on the bottom of each connecting rod piston pin bushing was noted, but it was not discernable to touch.
4. The master rod bearing backs had become loose enough to wear of an appreciable amount of silver plating.
5. Magnaflux indicated slight cracks at the corners of two master rod end seal teeth, which mated with the master rod bearing ends to prevent rotation.
The piston skirts were unusually clean, even for the low power running accomplished. This, in conjunction with the previously reported spark plug fouling, confirmed that reducing the crankshaft squirt hole size was appropriate.
The engine was to be rebuilt during the next four to six weeks, incorporating changes, after which testing would resume.
Although parts were being machined for the second and third engines, it would be two or three months before the second engine was ready to run.
The first engine had been running with direct propeller drive. The 0.56 reduction gears were expected at the end of September 1946. If the dynamometer was operational before the reduction gear was ready, limited running up to 2,000 rpm was being considered. The two complete two-speed dual-rotation reduction gears were expected in late September also, but nose-to-nose endurance testing was scheduled for them prior to their use on an engine.
The ATSC had commented on Lycoming Report No. 1002, which proposed a reduction gear speed shifting control scheme consisting of an "H" type throttle control, something the ATSC thought undesirable, especially for multi-engine aircraft. In general, mechanical trip devices on throttle quadrants were not desirable; instead, the ATSC favored a control requiring only initial positioning with the remainder of the shift sequence occurring automatically. Lycoming engineers pointed out that the "H" type throttle and mechanical trip devices were merely illustrative of the fundamental shift problem and were never intended for use on the final article.
Lycoming's early test on Bosch fuel injection systems had identified defects in the pumps and nozzles that had been referred to Bosch for correction; the corrections had not been forthcoming despite Bosch's stated intent to participate in the project. Blackwood observed that fuel injection delays would be detrimental to the project; Lycoming suggested and ATSC agreed that ATSC send a representative to Bosch to determine its intent regarding the program.

A 1-cylinder engine to be used for a 150-hr test patterned after the qualification test schedule was ready and would be run in the new laboratory when one of the stands became available. The test schedule involved the following ratings:

Single-Cylinder 150-hr Test Schedule
Rating	imep (psi)	isfc (lb/hp/hr)	rpm	Estimated Equivalent, 36-Cylinder bhp	bsfc
Takeoff and Military	264	0.58	2,800	6,000	0.70
Normal	251	0.52	2,400	5,000	0.61
High Cruise	155	0.35	2,200	3,000	0.39
Medium Cruise	143	0.333	1,600	2,000	0.37
Low Cruise	90	0.34	1,300	1,000	0.39

The supercharger section used to check the effect of a new diffuser on pulsation points had experienced a bearing failure whose cause had not been fully determined. It had been repaired and had a satisfactory run during Blackwood's visit.
The new laboratory status was as follows:
1. The first 1-cylinder dynamometer was to be started during the week of 15 Jul 1946. The remaining 1-, 3- and 4-cylinder stands were to be available at approximate two week intervals.
2. The 36-cylinder dynamometer was to be ready in August 1946.
3. The stresscoat room was operational and preliminary tests had started. The rocker arm shaft bearings were being tested first since cracking had been encountered during 1-cylinder tests.
4. Crankpin spline tests were ongoing. An error in strain gage calculation had resulted in all previous tests occurring at excessive loads. Revised data indicated the pins should be good for 10 million cycles at takeoff power. Further tests were to establish endurance limits more accurately.
5. The crankcase with the crankshaft had been tested statically with a torsion load on the crankshaft instrumented with strain gages, but results were not yet available.
6. A mounting ring and the above crankcase were being set up for spin tests and knuckle pin pressure tests. This data would permit modifications to correct the knuckle pin distress found after the first run.
7. An oil pressure pump was on test to determine its capacity and performance.
8. A master rod with one link rod loaded to simulate takeoff power but at 2,100 rpm had been run. Check runs were to be made at takeoff load and 2,600 rpm and then endurance running at 3,000 rpm.
9. The valve gear setup for studying camshaft shift action and valve operation was ready to operate.

[16 Aug 1946 Memorandum Report TSEPP-503-3280. Contract No. W-33-038 ac-564 on Development of the XR-7755 Engine, P350500.]

7 Aug 1946. The knuckle pin grooves and flats had been altered to make them more durable, and the new version was testing well. A new engine build was scheduled in about a week, as soon as a full set of the new knuckle pins could be built. Apparently someone wanted an engine demonstration; Lycoming thought that could be accomplished during the first week of October 1946.

Consolidated had analyzed its needs for heavy bomber Curtiss propellers: the 6-blade version would need to be 20 feet in diameter, the 8-blade version 18 feet in diameter.

The Lycoming BX had been mounted in a test stand on 1 October; Lycoming had requested 500 gallons of ethylene glycol.

Mid-August 1946. In what appears to be talking points for a telephone conference, Blackwood listed the following {words in parentheses are apparently answers}:

Discuss supercharger failure.
What were the exact modifications for this test? {Diffuser to move point of pulsation – no results yet. Spark plug tests results and discuss.}
Have Lycoming put 36-cylinder run times at the end of each report; Call 2 Item 1 – 15:12 hrs. Also further breakdown on runs at 258 imep.
Is the fuel feed via spray bar or spinner? {Spray bar, provisions for spinner.}
Fuel injection – Bosch seems uninterested in aircraft work; Lycoming should contact Bosch and get an understanding. In the mean time, suggest establishing another source: Bendix, Chandler-Evans, Ex-Cell-O, Caterpillar.
Carpenter – status of Curve No. 4217, hp vs spc vs speed in Report No. X-647. {Single tests being run to supplement}.
Control work with whom and status (Bosch).
Source of AN-F-33R (Grade 115/145) fuel. {Standard Oil of Indiana, 300,000 gal/yr.}
Item 12-5 Status {Test scheduled.}
Get estimated 36-cylinder performance curves for present test club for estimating powers.
Status of 2nd engine buildup, parts for 3rd. {Several months.}
Inspection results for 1st engine? {Last of September.}
When 0.56 gears? Also two-speed nose-to-nose test parts? {About the same time.}
Are there any actual engine photographs and actual weights? {Yes, values not specified.}
Status of new facilities.
Discuss control of two-speed shift.

Need propeller 1 Feb 1947.
Contemplate nose-to-nose test January 1947, 4 months for the test.
Cylinder for 150-hr run will be run soon in new lab. Comment on Lycoming's test schedule.
Request fuel directly from Standard Oil of Indiana; 5,000 gal on hand.}

[Penciled notes by J.G. Blackwood. RG 342 RD2311 XR-7755, 1943-1948: 503-602 Conf and Tel Notes.]

20 Aug 1946. Blackwood/Lycoming telcon.
John Carpenter reported that the new pins had been delayed 10 days because the silver plating failed the black light inspection at Mallory. The new pins passed the ALCOA fatigue test. Bendix had visited to propose a new single 36-cylinder injector. Bosch was expected to supply nozzles that week. Hamilton Standard advised that a propeller for the two-sped dual-rotation test was available, but final ordering was delayed until after a Hamilton Standard/Propeller Laboratory conference that was to occur 20-21 Aug 1946. There had been no requirements change on propeller speeds, gear ratios and usage methods. Subassembly buildup for the 2nd engine had begun.

Posthauer asked about the compound proposal status and was told MatCmd expected its release in September 1946. Posthauer was advised to envision an modified compound program through first phases as well as a normal continuation; also advised to reexamine quotes since the ones submitted were higher than previous 1-cylinder running.

Earle Ryder inquired about ethylene glycol and was advised that Middletown Depot had been advised to ship same. Requested changes to the proposed change order revising Item 12-5 test conditions; he was rewriting it to include 12° instead of 15° spark advance; 264 imep instead of 258; Normal rpm = 2,500; "tests run hereafter" can cover at time of test on those not already covered; limit the testing to 1-cylinder engine since 3- and 4-cylinder engines would not be concerned with maximum output. [Penciled notes by J.G. Blackwood. RG 342 RD2311 XR-7755, 1943-1948: 503-602 Conf and Tel Notes.]

10 Sep 1946. Posthauer and Carpenter of Lycoming, and Col R.J. Minty, Col R.L. Wassel, Col R.J. O'Keefe, A.L. Berger and J.G. Blackwood of the Air Materiel Command (AMC) met to discuss future XR-7755 developments. Posthauer announced that if there were no objections by the AMC Lycoming was planning a general gathering in Williamsport of Army, military aircraft contractors and airlines in 31 Oct 1946. The XR-7755 was to be exhibited, probably running on the test stand, and the new building incorporating test facilities would be in operation. The hope was to arouse interest in application of the engine. No one objected, the gathering occurred, and and article on the XR-7755 appeared in the December 1946 issue of Aero Digest magazine.

In connection with compounding the XR-7755, Lycoming's previous proposal of 6 Jun 1946 was reviewed. Lycoming was instructed to submit a new proposal covering essentially the material in paragraphs 2-a, b, c, d and f, as modified by f-1 or its previous proposal. This covered single-cylinder performance running to study potential gains made by compounding, endurance tests with back pressure on a 4-cylinder bank (instead of the previously-suggested single cylinder), engineering design and detail of the compounded XR-7755, and new parts and controls required for the compounded engine and tests of these parts. Lycoming was to submit a more detailed proposal than before, especially in reference to the parts and testing.

Lycoming had made a preliminary study with General Electric that revealed the most appealing arrangement involved using exhaust gases to drive a turbine that was geared back to the crankshaft through the engine supercharger drive shaft. The exhaust gases then passed to a turbosupercharger that maintained sea-level air pressure at the engine's air inlet at altitude. Tentative sketches showed two feedback turbines and two two-stage turbosuperchargers, but one feedback turbine and two single-stage turbosuperchargers will also be studied. AMC emphasized that it would prefer Lycoming to provide the entire compounded engine including all turbos, since components were so interrelated. However, if necessary, the turbosuperchargers could be provided by the Army. Each of the two compound units was expected to weigh about 350 lb.

In a separate discussion among Posthauer, Ryder and Blackwood, the following items were discussed:

Bosch was still working to perfect XR-7755 injection equipment, but because of delivery delays and to avoid potential unsatisfactory performance of a single source, a second source was sought. The AMC sought initial design studies and Lycoming thought the cost would not be large and that sufficient funds were probably available without additional contractual action. Bendix representatives had already visited Lycoming and proposed a single 36-cylinder injector instead of the present three 12-cylinder units. This would help simplify the engine rear, especially with respect to compounding.
Preliminary extension shaft/two-speed dual-rotation reduction gear studies were discussed.
Contract Item 8 covered special tests on various components and the amount originally estimated was almost depleted. Lycoming was tasked to determine the Item 8 status and advise whether additional funds were required.
Hamilton Standard had contacted Lycoming about using its dual-rotation propeller in the two-speed dual-rotation reduction gear test stand engine, which was forecast to be on test by January or February 1947. A propeller suitable for 4,000 hp in the low reduction gear (takeoff) ratio was promised , which would permit shift change tests. A suitable 5,000 hp propeller might not be available for one or two months, but a Curtiss test club was available for this application.

[20 Sep 1946 Memorandum Report TSEPP-504-3285. Conference on Development of the XR-7755 Engine on Contract No. W-33-038 ac-564, P350520.]

19 Sep 1946. Earle Ryder of Lycoming informed Blackwood that a test on the 4-cylinder engine at 70-80 inHgA manifold pressure plus some backpressure, the equivalent of 6,000 hp, required too much air. The supercharger required too much power and was no good for 70-80 inHgA. The 3-cylinder engine was being assembled and mounted on its test stand. The 36-cylinder engine was almost finished and was expected to be on its stand by 1 Oct 1946. The first phase of crankshaft joint vibration tests at 6,000 hp equivalent was done and the second phase was under way. A test setup on the big dynamometer was well along and expected to be complete in about 10 days; it was being checked with the Lycoming BX engine. [Penciled notes by J.G. Blackwood. RG 342 RD2311 XR-7755, 1943-1948: 503-602 Conf and Tel Notes.]

9, 10 Oct 1946. Engine #101, which had completed initial runs, been torn down and rebuilt, was running on the propeller stand at the time of Blackwood's visit. It had completed 30 min at 1,900 rpm, 40 min at 2,000 rpm, 40 min at 2,100 rpm, 40 min at 2,200 rpm, and 30 min at 2,300 rpm at which time it was producing an estimated 3,730 hp. After completing this schedule the bottom cylinder bank was removed to inspect the engine interior. Nothing unusual was noted, the cylinder bank was being replaced and a short run-in follow, after which it would be run for 5 min at 2,600 rpm at an estimated 5,000 hp; a further inspection was then to be made.

In reply to the 25 Sep 1946 AMC letter about the plans for the XR-7755 program, Lycoming had prepared a cost summary for each fiscal year. However, the yearly cost was not based on the engines produced each year, but rather on a total number of engines to be built by 1950, with some parts releases at an early date in order to obtain raw materials as soon as possible. This presented a more integrated total program and would provides engines at a lower cost than contracting for one or two engines each year. A contract phasing scheme would be necessary with Lycoming's proposed program.

Lycoming also questioned the engine flight requirements, to which AMC estimated for planning purposes four engines for one airplane, two spares and two parts sets around 1949. Lycoming expected to us an additional 500 hrs of 36-cylinder development running in addition to the approximate 1,000 hrs already set up on the contract; this was deemed a small number of hours prior to a 1950 type test, and AMC was exploring how to increase the hours run. As of 9 Oct 1946 there were three engines and one spares set on contract, so the most immediate step to improve the situation was to permit Lycoming to build a fourth engine and another spare parts set. This would keep the dynamometer and propeller test cells in operation a greater percentage of the time.

During Lycoming's visit to Wright Field on 10 Sep 1946, AMC suggested that design studies of a second fuel injection system source be initiated. Since that time, Lycoming and Bendix had met and negotiations were proceeding for Bendix to accomplish studies and design only for a system for the XR-7755. A 36-cylinder injection system was planned which would incorporate a throttle body as a complete unit. This would require a new drive not then available in the XR-7755 design. Lycoming suggested this new unit could be designed into the proposed compounded XR-7755, but AMC wanted it to be available as a second source for the existing engine.

Lycoming had received three Bosch fuel injection pumps and nozzles from Bosch as well as Ex-Cell-O. These components were to be tested on the 1-cylinder engine in the new laboratory as soon as possible. One fuel-injected engine, the XR-7755-5, was on order, and this engine would probably have direct cylinder injection. However, Lycoming had done some 1-cylinder work with port injection and had released two 4-cylinder manifolds for port injection tests. Ex-Cell-O nozzles for port injection were on hand.

The status of Contract Item 8 was discussed; this Item covered special XR-7755 component tests, which were proving very useful in checking and improving component performance and endurance more rapidly and less expensively than could be done on the 36-cylinder engine. The money expended on Item 8 has almost reached $389,500.00 initially estimated for Item 8 and the question was raised as to whether additional funds should be obligated in order to permit continuation of Item 8, which was not entirely completed. A contract review by the Wright Field Contracting Office had established that limitations on Lycoming were not set by Item estimates but by the total contract amount, which was not to be exceeded. Lycoming was also contractually limited on test hours for certain Items, but this was not applicable to Item 8. Hence, Lycoming was permitted to continue the work of Item 8 without additional funds being set up at that time. Certain items had been completed at costs below those estimated; these compensated for Item 8 estimate overruns and no contract adjustment were required until the total money expended approached the contract total.

Tests in the new laboratory had the following status:

A 1-cylinder engine had run 109 hrs of a 150-hr qualification test schedule.
A 3-cylinder engine using one section of the 36-cylinder crankcase was making initial runs on a new stand. This engine would serve to test multi-cylinder parts that could not be tested on the 1- and 4-cylinder engines.
The main oil pressure and torquemeter pumps were on test.
A single-throw crankshaft test piece has passed magnaflux inspection after its last 10 million cycles at the equivalent of 6,000 hp on the 36-cylinder engine. This unit was being prepared for another 10 million cycle test with vibratory torque at 60-65,000 in-lb, an increase of 10-15,000 in-lb over the previous test. Lycoming planned to continue increasing the vibratory torque value until failure occurred in order to determine the crankshaft spline joint limitations.
A 36-cylinder crankcase had been mounted on a stresscoated mount housing to which a 6-g load was applied. This determined the points of mount housing maximum stress, and strain gages wer placed at these points. A repeat test should reveal stress measurement at the highest load points.
A fuel injection distribution test setup was being prepared, which would provide the usual burette arrangement for checking the quantities of fuel injected from a nozzle set over a definite time period.
Connecting rod fatigue tests had been satisfactorily completed and the apparatus was being modified for link pin lubrication studies.
Tests were about resume on a special cylinder head that facilitated camshaft shifting tests.
A General Motors Corporation fatigue machine was being set up for use with various engine components; the first would probably be the knuckle pins at a 6,000 hp equivalent load.
A new wooden supercharger test housing had been made and was waiting for the matching discharge elbows after which it was to be placed on the supercharger test stand to determine if air distribution had improved over the previous design.
Subassemblies for the second engine were being assembled, but a complete parts set was still not available. Engine parts were expected "soon", and parts for the two-speed reduction gear units as well as for the 0.56 development test reduction gear units were expected about 1 Dec 1946.

[16 Oct 1946 Memorandum Report TSEPP-503-3291. Development of the XR-7755 Engine, P350618.]

12 Oct 1946. Lycoming's Posthauer, in reply to AMC's 25 Sep 1946 letter, sent a letter estimating the costs to produce five complete engines and five disassembled engines by the end of FY 1950.

Lycoming had sufficient space and machine tools for the above with the exception of the following machine tools, which were requested from Government surplus stock, or sufficient funds from the Government to purchase said machine tools, which Lycoming estimated to cost $225,000.00

The engines to be supplied were Lycoming XR-7755-3 equipped with fuel injection. In order to meet the completion dates, it was necessary that an extra engine be provided to Lycoming for development tests; this was to cost and additional $380,000.00 plus a $15,200 (4%) fixed fee. Because of the program's nature, Lycoming found it impossible to show the number of engines that could be supplied in any one year, and because of the experimental nature of the program and the need to secure and machine parts, it would take almost all of the time period to produce 1 or 10 engines.

Item (a) included 1,000 hrs endurance testing to prepare it for an official type test to be run at Wright Field. During the first two Item (b) periods, long lead time items would be ordered and parts requiring less time, along with parts held up for design completion, would be ordered during the last two periods. Item (c) tooling would be complete during the first two periods.

Lycoming urged the AMC to consider engines for flight purposes, especially if aircraft use was contemplated during the next 3 or 4 years. [12 Oct 1946 Letter, Lycoming to AMC. RG 342 RD2311 XR-7755, 1943-1948: 503-602 Conf and Tel Notes.]

	1 Jan 1947 30 Jun 1947	1 Jul 1947 30 Jun 1948	1 Jul 1948 30 Jun 1949	1 Jul 1949 30 Jun 1950
(a) Development Test		$223,000.00	$145,000.00
(b) Engine Parts	$100,000.00	$1,330,000.00	$1,590,000.00	$718,000.00
(c) Tools, Dies, Patterns, etc.	$25,000.00	$165,000.00
(d) Assembly Tools		$20,000.00
Total Cost	$125,000.00	$1,515,000.00	$1,813,000.00	$863,000.00
Grand Total for the Entire Period = $4,916,000.00; a fixed fee of $196,640 (4%) should be added

Machine Tools Requested by Lycoming
from Government Surplus Stock
No Reqd	Description
1	24" Involute Gear Checker
2	10" x 48" External Grinders
2	Fellows 615 Gear Shapers
1	Detroit Gear GG-19 Grinder (new type dresser)
1	Bridgeport 1202 Mill
2	28" x 60" Cincinnati Hydrotel Mill with 360° tracer
1	4" Radial Drill
1	Pratt & Whitney #3 Jig Borer
1	4" Bar Boring Mill
2	Heald 174 Internal Grinder (31083)
3	20" x 60" Engine Lathes

14 Oct 1946. Blackwood appears to be writing instructions to a subordinate (Jack) having him write up 500 hrs 1-cylinder performance studies. Also, build another engine (XR-7755-7). Set up balance on Call to be used as required as program progresses. Then can choose Calls and wording of particular program when better defined. Using government-furnished gas turbines, design feedback requirements and establish exhaust gas pressure and temperature conditions leaving the feedback turbine at normal power, 5,000 hp and 45,000 ft). Also arrange studies of the whole system but keep in mind the turbines will be worked out by the government and General Electric. [Penciled notes by J.G. Blackwood. RG 342 RD2311 XR-7755, 1943-1948 = 503-602 Conf and Tel Notes.]

15 Nov 1946. Lycoming's Carpenter reported that two XR-7755 cam drive bevel drive gear bearings had failed and that nine bevel driven gear bearings had failed. The others were in perfect condition. On the supercharger front, the new version had improved the flat spots in its performance. [Penciled notes by J.G. Blackwood. RG 342 RD2311 XR-7755, 1943-1948 = 503-602 Conf and Tel Notes.]

1 Dec 1946. Using available data, Blackwood prepared a summary of hours run during 1946. [RG 342 RD2311. XR-7755, 503-602 Current]

**Cumulative Hours Run on Cylinders of the Multi-XR-7755 Design, May – July 1946**
Compile Date (1946) Report No, Date (1946)	10 May 72, 7 May	23 May 73, 14 May	28 May 74, 21 May	3 Jun 75, 31 May	5 Jun 76, 3 Jun	15 Jun 77, 11 Jun	78	9 Jul 79, 29 Jul	80	14 Jul 81, 16 Jul	14 Jul 82, 15 Jul	30Jul 83, 23 Jul
Contract Item 1	976.2	976.2	976.2	976.2	976.2	976.2	976.2	976.2	976.2	976.2	976.2	976.2
Item 2
Item 3	456.4	456.4	456.4	456.4	456.4	456.4	456.4	456.4	456.4	456.4	456.4	456.4
Item 4
Item 12-1	122.3	122.3	122.3	122.3	122.3	122.3	122.3	122.3	122.3	122.3	122.3	122.3
Item 12-2	1998.7	1998.7	1998.7	1998.7	1998.7	1998.7	1998.7	1998.7	1998.7	1998.7	1998.7	1998.7
Item 12-3	532.9	532.9	532.9	532.9	532.9	532.9	532.9	532.9	532.9	532.9	532.9	532.9
Item 12-4	1000.0	1000.0	1000.0	1000.0	1000.0	1000.0	1000.0	1000.0	1000.0	1000.0	1000.0	1000.0
Total, Items 1 thru 12-4	5086.5	5086.5	5086.5	5086.5	5086.5	5086.5	5086.5	5086.5	5086.5	5086.5	5086.5	5086.5
Call 3, Item 1	500.2			2.0	2.5	4.0	4.0	15.2	15.2	15.2	15.2	15.2
Call 3, Item 2
Call 4, Item 1	500.0										500.0
Call 5, Item 1	200.0										200.0
Total, Calls 3, 4, 5	1200.2	1200.2	1200.2	1200.2	1200.2	1200.2	1200.2	1200.2	1200.2	1200.2	1200.2	1200.2
Call 1, Item 5	256.6	256.6	256.6	256.6	256.6	256.6	256.6	256.6	256.6	256.6	256.6	256.6
Supp. 7, Item 1	598.8	620.9	665.8	665.8	665.8	665.8	665.8	665.8	665.8	665.8	665.8
Supp. 7, Item 2	287.0	316.4	331.7	331.7	405.1	424.0	444.9	556.3	579.6	619.8	619.8	650.9
Call 2, Item 1											15.2	15.2
Call 2, Item 2											7.6
Call 2, Item 5
Multi Total				2.0	2.5	4.0	4.0	15.2			22.8	15.2
Single Total	7429.1	7480.6	7540.8	7540.8	7614.2	7633.1	7654.0	7765.4	7788.7	7828.9	7828.9	7194.2

**Cumulative Hours Run on Cylinders of the Multi-XR-7755 Design, August – November 1946**
Compile Date (1946) Report No, Date (1946)	1 Aug 84, 30 Jul	15 Aug 85, 13 Aug	86	27 Aug 87, 29 Aug	3 Sep 88, 27 Aug	89	90, 10 Sep	91, 17 Sep	92, 24 Sep	3 Oct 93, 10 Oct	14 Oct 94, 8 Oct	22 Oct 95	96	31 Oct 97, 29 Oct	7 Nov 98, 5 Nov	18 Nov 99, 12 Nov
Contract Item 1	976.2	976.2	976.2	976.2	976.2	976.2	976.2	976.2	976.2	976.2	976.2	976.2	976.2	976.2	976.2	976.2
Item 2
Item 3	456.4	456.4	456.4	456.4	456.4	456.4	456.4	456.4	456.4	456.4	456.4	456.4	456.4	456.4	456.4	456.4
Item 4
Item 12-1	122.3	122.3	122.3	122.3	122.3	122.3	122.3	122.3	122.3	122.3	122.3	122.3	122.3	122.3	122.3	122.3
Item 12-2	1998.7	1998.7	1998.7	1998.7	1998.7	1998.7	1998.7	1998.7	1998.7	1998.7	1998.7	1998.7	1998.7	1998.7	1998.7	1998.7
Item 12-3	532.9	532.9	532.9	532.9	532.9	532.9	532.9	532.9	532.9	532.9	532.9	532.9	532.9	532.9	532.9	532.9
Item 12-4	1000.0	1000.0	1000.0	1000.0	1000.0	1000.0	1000.0	1000.0	1000.0	1000.0	1000.0	1000.0	1000.0	1000.0	1000.0	1000.0
Total, Items 1 thru 12-4	5086.5	5086.5	5086.5	5086.5	5086.5	5086.5	5086.5	5086.5	5086.5	5086.5	5086.5	5086.5	5086.5	5086.5	5086.5	5086.5
Call 3, Item 1	15.2	15.2	15.2	15.2	15.2	15.2	15.2	15.2	15.2	15.2	15.2	15.2	15.2	15.2	15.2	15.2
Call 3, Item 2												7.6	7.6	9.0	16.1	17.3
Call 4, Item 1
Call 5, Item 1
Total, Calls 3, 4, 5	1200.2	1200.2	1200.2	1200.2	1200.2	1200.2	1200.2	1200.2	1200.2	1200.2	1200.2	1200.2	1200.2	1200.2	1200.2	1200.2
Call 1, Item 5	256.6	256.6	256.6	256.6	256.6	256.6	256.6	256.6	256.6	256.6	256.6	256.6	256.6	299.1	299.1	299.1
Supp. 7, Item 1		665.8		665.8	665.8	665.8	665.8	665.8	665.8	665.8	665.8	666.1	666.1	670.3	673.1	678.5
Supp. 7, Item 2	665.6	798.7		798.7	808.2	827.9	804.9	804.9	804.9	804.9	804.9	804.9	804.9	806.8	840.6	882.8
Call 2, Item 1
Call 2, Item 2
Call 2, Item 5
Multi Total	15.2	15.2		15.2	15.2	15.2	15.2	15.2	15.2	15.2	15.2	22.8	22.8	24.2	31.3	32.5
Single Total	7208.9	8007.8	6543.3	8007.8	8017.3	8037.0	8014.0	8014.0	8014.0	8014.0	8014.0	8014.3	8014.3	8062.9	8099.5	8147.1

1 Nov 1945 – 3 Dec 1946. The PPL prepared and distributed partial lists of Lycoming Verification Test Reports.

While we do not now have these reports, Blackwood's penciled notes while examining them reports provide enlightening critique:

Report Title	Lycoming Report No.	Report Date	Work Started	Work Complete
Reports Delivered During December 1944
50-Hour Endurance Test of BX-3350 Engine Using XR-7755-1 Cylinder Block Construction	835	20 Nov 1944	7 Sep 1944	21 Sep 1944
Reports Delivered During April 1945
Investigation of the Peroformace of the XR-7755 Cylinder with Various Valve Timings, Compression Ratios and Spark Timings	849	15 Jan 1945	20 Jul 1944	10 Oct 1944
The Effects of Exhaust Back Pressure on the Detonation Limited Performance of an XH-2470 Type Cylinder at 2,000 rpm	852	31 Jan 1945	12 Mar 1944	28 Mar 1944
Calibration of an XH-2470 Type Cylinder	855	13 Feb 1945	24 Jan 1944	13 Feb 1944
Performance of the XR-7755 Engine Cylinder with Cruise Cams R-5414-Y (Intake) and R-5343-Y (Exhaust)	856	13 Feb 1945	29 Nov 1944	4 Dec 1944
Development of Supercharger Inlet Passage for the XR-7755 Engine	857	14 Feb 1945	1 Jun 1944	12 Dec 1944
Technique of Making Detonation Limited Power Curves on the XR-7755 Engine Cylinder	862	15 Mar 1945	18 Dec 1944	14 Jan 1945
Inspections of 50-Hour Bench Endurance Test of American Bosch Multi-Cylinder Fuel Injection Equipment	864	30 Mar 1945	17 Jan 1945	3 Mar 1945
Reports Delivered During July 1945
100 Hour Endurance Test of Standard XR-7755 Single-Cylinder Engine	886	1 Jun 1945	8 Jan 1945	23 Jan 1945
100 Hour Endurance Test of Standard XR-7755 Single-Cylinder Engine	887	4 Jun 1945	29 Jan 1945	15 Feb 1945
Report of 150 Hour Model Test of Lycoming O-435-11 Engine No. 101-17 at a rating of 190 BHP at 2,550 rpm	895	30 Jun 1945	25 May 1945	9 Jun 1945
Reports Delivered During September 1945
Investigation of Pressures in a 5.25" x 4.75" Cylinder with 8.5:1 Compression Ratio Using a M.I.T. Type Otice Pressure Indicator	891	24 Aug 1945	10 Oct 1944	14 Dec 1944
100 Hour Endurance Test of XR_7755 Full-Scale Single-Cylinder Engine (SC-215B)	901	27 Jul 1945	21 May 1945	5 Jun 1945
Measurement of Cylinder Pressures in the X-6 Type Cylinder at 8.5:1 Compression Ratio	902	30 Jul 1945	22 Nov 1944	19 Jan 1945
Peak Pressure and Pressure Indicator Cards for the XR_7755 Engine Cylinder Assembly (B-5410-Y Assy)	904	23 Aug 1945	25 May 1945	7 Jun 1945
Performance Tests of the XR-7755-1 Supercharger	906	6 Aug 1945	5 May 1945	6 Jun 1945
Investigation of Takeoff Performance Characteristics of XR_7755 Engine Cylinder Head Assemblies R-5166-F, Rev. E and R-5355-7, Rev D	907	14 Aug 1945	5 Mar 1945	18 May 1945
100 Hour Endurance Test of Standard XR-7755 Single-Cylinder Engine	910	6 Aug 1945	8 Jun 1945	21 Jun 1945
Determination of the Optimum Spark Advance for Cruise Operation of the XR-77555 Cylinder Assembly (R-5410-Y) with AN-F-28R Fuel at 8.5:1 Compression Ratio	911	8 Aug 1945	11 Jun 1945	5 Jul 1945
Investigation of the Performance of the XR-7755 Cylinder Assembly (R-5410-Y) with AN-F-33 Fuel at 8.5:1 Compression Ratio	912	9 Aug 1945	18 Jun 1945	11 Jul 1945
Preliminary Bench Performance Test of the American Bosch Fuel INjection System for the Lycoming XR-7755 Engine	916	22 Aug 1945	5 May 1945	6 Jul 1945
Report of the 150 Hour Model Test of Lycoming O-435-11 Engine No 252-17 at a Rating of 190 BHP at 2,550 rpm, 3rd Test	917	28 Aug 1945	19 Jul 1945	1 Aug 1945
Reports Delivered During October 1945
100 Hour Endurance Test of XR-7755 Full-Scale Single-Cylinder Engine (SC-215B)	913	5 Sep 1945	17 Jun 1945	13 Jul 1945
Simplex Oil Seal for Dual Rotation Propeller Shafts	920	28 Sep 1945
Preliminary Bench Performance Test of American Bosch Single Cylinder Type APE1Z Fuel Injection Equipmement	923	27 Sep 1945	11 Jul 1945	5 Sep 1945
Dynamometer Calibration of the Ex-Cell-O Model EX-2030 Gasoline Injection Pump on an O-435 Engine	924	2 Oct 1945	26 Dec 1944	9 Jul 1945
Air Flow Distribution Test of Model XR-775-1 Sueprcharger	927	12 Oct 1945	25 Jul 1945	29 Aug 194
[RG 342 RD3844. Lycoming XR-7755 Verification Tests.]

Reports Delivered During May 1946
Item 12-6 Stress Analysis of XR-7755-1 Rear Accessory Section	1005	13 May 1946
Item 12-7 Stress Analysis of Two-Speed Dual-Rotation Reduction Gear Unit for Lycoming XR-7755-3 Engine	1006	21 May 1946
Reports Delivered During July 1946
100-Hour Endurance Test of Standard XR-7755 Single Cylinder Engine (SC-215B No. 6)	1013	13 Jun 1946	28 Dec 1945	18 Apr 1946
Preliminary Endurance Test of XR-7755 Engine Accessory Housing Assembly - Supercharger Drive, Part No. 81408	1017	20 Jun 1946	18 Apr 1946	29 Apr 1946
Developmant and Endurance Investigation of XR_7755 Two-Speed Propeller Drive Shift Mechanism	1019	25 Jun 1946	24 Oct 1945	15 Apr 1946
Reports Delivered During August 1946
Preliminary Carburetor Checks and Mixture Settings on the First Multi-Cylinder XR-7755 Engine	1020	17 Jul 1946	8 Nov 1945	26 Jun 1946
100-Hour Endurance Test of XR-7755 Full Scale Single Cylinder Engine (SC-215B No. 6)	1021	8 Jul 1946	23 Apr 1946	17 May 1956
Effect of Inlet Air Temperature on Knock-Limited Takeoff Power Using Port Injection on the XR-7755 Cylinder Assembly (R-5410-Y)	1025	18 Jul 1946	17 May 1946	21 Jun 1946
Reports Delivered During September 1946
Supplement II. Determination of the Optimum Spark Timing for the XR-7755 Cylinder Assembly (R-5410-Y) Using Port Fuel Injection	1023	17 Sep 1946
Item 8. Performance Tests of the XR-7755 Supercharger Using an 18 Vane Diffuser, Part NO. 81560	1029	3 Sep 1946
Item 8. Performance of XR-7755 Coolant Pump No. 81208 with Small Impeller Assembly Part No. F-7171-Y and Intermediate Impeller Assebly Part No. F-7170-Y	1030	6 Sep 1946
Item 12-2. Disassembly Inspection of XR-7755 Multi-Cylinder Engine Following 6 Hour Run-in and Preliminary Operation	1032	3 Sep 1946
Item 12-2. Preliminary Operation of the XR-7755 Multi-Cylinder Engine, 1:1 Propeller Drive	1033	3 Sep 1946
Item 8. Air Flow Distribution of the XR-7755 Supercharger Using an 18 Vane Difuser, Part No. 81560	1036	30 Sep 1946
Supplement II. Determination of the Comparative Performance of Several Types of Spark Plugs for Use in the XR-7755 Engine	1038	27 Sep 1946
Item 8. Investigation of the Oil Pressure to the Conneting Rod Link Pins of the Lycoming XR-7755 Multi-Cyllinder Engine	1039	26 Sep 1946
Reports Delivered During November 1946
Item 8. Fatigue Test of Master Rod for XR-7755 Engine	1051	22 Oct 1946	20 Jun 1946	4 Sep 1946
[RG 342 RD3775. XR-7755 Verification Test - Lycoming]

No. 849 reported performance that met Contract Item 1 except at 1,000 rpm; an alternate condition of 102 imep at 1,300 rpm met the 0.34 isfc was acceptable, although it probably gives higher bsfc. These tests were based on air temperature from Curve # 4999.

No. 889 was submitted as completing Item 1. These tests were based on the higher manifold temperatures of Report No. X-691.
Page 2 – Only the takeoff and high cruise performance requirements of the contract were met.
Page 5 – Omission of curve and page numbers.
Page 9, paragraph 31 – Better economy may not be achieved at increased speed due to higher friction.
Page 14 – Fuel/air ratio curves? Curve No ___, Page ___ (intake air temperature).
Page 15 – Middle curve data at 150°F. Intake air temperature?
General – What about requirements of Item 1? Need airflow and fuel/air ratio curves for Reports 849 and 889, along with performance or calibration curves prior to endurance, such as on Report 892 page 17.

No. 890.
Page 4 – 7.13:1 compression ratio.
Page 5 – Intake air temperature based on old low-temperature curve #4999; should be on curve #6478 established March 1945.
Page 23 – Are these data indicated? Specific air consumption high compared to bsfc of Report No. 892. — 0.40 – 0.43 isfc from 10 – 15 and 20 – 25 hrs. There should be a calibration including fuel/air ratio to show condition to be maintained for best cruise economy and best takeoff power.

No. 892.
Page 17 – Fuel/air ratio also on pages 18 and 19.
Page 20 – Items should be plotted on an indicated basis, like Report No. 890.
Page 21 – Fuel/air ratio between hours 30 and 35 is too high, although this does not reflect on the bsfc plot. This is also true between hours 90 and 95. Different manifold temperature curves were followed (high on takeoff, 90°F at cruise) to meet sfc requirements. These should be met with the latest temperature curves of X-691.

No. 897. Low intake temperatures. Include fuel/air ratio and calibration to show best economy and best power points.

No. 899.
Page 5 – Old temperature used for intake manifold temperature. Need a calibration curvew to show that endurance values used are best economy.
Page 23 – Item 12-3 isfc requirements are not met for cruise. (Modify contract wording to specify best economy and best power for this item?)
No. 907. Pertains to takeoff power testing using cylinder head PNs R-5166-Y Rev E. and R-5355-Y Rev. D.
Page 5 – Manifold fuel injection nozzle 12" from cylinder; it would have to be in head port on the multi-cylinder engine.
Page 6 – Manifold and intake port change cross sectional area as well as swirl; these affect velocity.
Pages 15, 16, 20, 21, 31 to 42 – Single-cylinder or multi predicted bhp values? What is the single-cylinder value?

3 Dec 1946. Blackwood and Ahern met with Lycoming's Carpenter, Riddell, Hoffman and Heinery. Carpenter reported that #101 was to be rebuilt next week, #102 was to be available in January 1947, and that the reduction gear would be completed between 15 and 30 Dec 1946. One note says "…bearing failure and knuckle pin…," but does not elaborate.

The original Bosch fuel injection system design was of the mass airflow type, but Bosch had decided the equipment cost for the one Lycoming system was not warranted; the new design was a speed-density scheme, the details of which were not specified. <https://www.enginehistory.org/Accessories/HxFuelSys/FuelSysHx09.shtml> The first 1-cylinder unit was being assembled, but satisfactory nozzles were still in the future. The AMC had been hoping for a direct cylinder injection system, but Lycoming was building manifolds for port injection. AMC criticized the port injection for several reasons: 1) Backfires were possible at low-speed, low-airflow operation; 2) Backflow due to valve overlap was possible, but the two-position camshaft helped. Lycoming would be trying both in about a month. A 1-cylinder engine had achieved an 0.37 lb/hp/hr sfc using both port and direct injection, but the effect on volumetric efficiency was not yet known. The nozzle opened at 500 psi on both port and direct injection. Blackwood's notes contain an interesting cryptic phrase, "use glass manifold," with no explanation.

Marshall from Bendix reported that the layout for a 36-cylinder pump was done. This was initially intended to be integral with a mass-air-flow-sensing throttle body, but more recent thinking found it advantageous to separate the two so that the pump could be rear-mounted and driven from the accessory section. AMC envisioned three pump drives at the engine rear all running at 1/2 crankshaft speed; the Bosch system would use all three for its three 12-cylinder pumps, while the Bendix would use the center drive only. AMC still wanted two injection system sources, but was not adamant that they be identical so long as changing between the two required minimal changes. Lycoming was to proceed with the Bendix design and to get quotes from Bendix for the physical articles.

The XR-7755 then had a straight spline on the spark advance shift driven by oil pressure. A later spark advance mechanism was to use a spiral spline linked to the camshaft shift. [Penciled notes by J.G. Blackwood. RG 342 RD2311 XR-7755, 1943-1948 = 503-602 Conf and Tel Notes.]

Indicated Specific Fuel Consumption using AN-F-28R Fuel
imep	rpm	Contract isfc	Report 849 isfc	Report 889 isfc	Report 912 isfc
231	2,600	0.59	0.51	0.59	0.59
141	1,600	0.333	0.33	0.35	0.341
124	1,800		0.34
116	1,000	0.344
102	1,300		0.34
89	1,300		0.345	0.336

Best Economy Using AN-F-33 Fuel
Rating	rpm	bhp	bmep (psi)	bsfc (lb/hp/hr)	Mech Eff (%)
Takeoff	2,600	5,760	222.5	0.600	85
Military	2,600	5,760	222.5	0.600	85
Normal	2,300			87
High Cruise	2,200	3,100	144	0.367	90
Cruise	1,600	2,115	135	0.363	90
Low Cruise	1,300	1,075	84.5	0.363	89
Power at Guaranteed bsfc + Free of Detonation Using AN-F-33 Fuel
Takeoff	2,600	5,670	222.5	0.600	85
Military	2,600	5,670	222.5	0.600	85
Normal	2,300			87
High Cruise	2,200	3,680	171	0.400	90
Cruise	1,600	2,255	144	0.367	90
Low Cruise	1,300	1,527 120	0.386	89
Specific Fuel Consumption Using AN-F-28 Fuel
Takeoff	2,600	5,000	196	0.799	85
Military	2,600	5,000	196	0.690	85
Normal	2,300	4,000	178	0.600	87
High Cruise	2.200	3,000	139	0.400	90
Cruise	1,600	2,000	127	0.370	90
Low Cruise	1,000	1,000	102	0.390	88

18 Dec 1946. Lycoming's Carpenter reported the XR-7755 was operating at 2,600 rpm and 38 inHgA producing 4,300 hp; estimated bsfc was 0.575 and fuel/air ratio was 0.087:1. The lower cylinder bank had been pulled and everything looked satisfactory and the engine was back together. A 50-hr endurance test was to begin on 18 or 19 December. The remaining parts for the second engine were to be available during the following week. [Penciled notes by J.G. Blackwood. RG 342 RD2311 XR-7755, 1943-1948 = 503-602 Conf and Tel Notes.]

26 Dec 1946. A few pages of Blackwood's notes appear to have been taken during a telephone call. They indicate that after 11 hrs endurance running an engine inspection had revealed metal pieces in the oil sump. One piston pin was seized to the link rod, but was free in the master rod. The surface of another link rod had defects in the silver plating at the knuckle pin. There was room in the connecting rod for a 0.030" wall piston pin bushing and knuckle pins were available from Mallory in 48 hrs. A further note, "Check R-2800 Service Manual" probably referred to P&WA instructions on re-plating knuckle pins. Lycoming planned to try silver-lead-indium first, and would also probably make a new rod set with bushings.Blackwood included a sketch of the master rod, link rod and link pin in cross section. More notes concern P&WA master rod, link rod and link pin part numbers and rework instructions. A further page of notes concerns R-4360 connecting rod design, component rework procedure and dimensions.

The 3-cylinder engine was running with a new-design link pin retainer, which was working well. The same part had been used on XR-7755 #102. The third parts set was 70% or more complete. The 0.56 reduction gear would be ready in a week and could go onto #101. The torquemeter in #101 was experiencing excess oil leakage and was being revised. [Penciled notes by J.G. Blackwood. RG 342 RD2311 XR-7755, 1943-1948 = 503-602 Conf and Tel Notes.]

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