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Cranks and Cases
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dpennings



Joined: 10 Dec 2016
Posts: 48

PostPosted: Mon Dec 14, 2020 14:43    Post subject: Reply with quote

in case you're intrested, here you can find an alternative to the Hirth joint when you scrall down to the pictures:

https://depatisnet.dpma.de/DepatisNet/depatisnet?window=1&space=menu&content=treffer&action=pdf&docid=DE102019003501A1&Cl=5&Bi=1&Ab=&De=2&Dr=7&Pts=&Pa=&We=&Sr=&Eam=&Cor=&Aa=&so=asc&sf=vn&firstdoc=1&NrFaxPages=14&pdfpage=1&xxxfull=1
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rwahlgren



Joined: 15 Aug 2003
Posts: 324

PostPosted: Mon Dec 14, 2020 16:50    Post subject: Reply with quote

No pictures seen on this link. It says error page with hyper text or ?
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dpennings



Joined: 10 Dec 2016
Posts: 48

PostPosted: Tue Dec 15, 2020 05:27    Post subject: Reply with quote

OK, let's try it with google:

https://patents.google.com/patent/DE102019003501A1/en?oq=DE102019003501A1

it might be a little bit weeker when it comes to high torque, but much easier to machine and works very well...
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rwahlgren



Joined: 15 Aug 2003
Posts: 324

PostPosted: Tue Dec 15, 2020 12:59    Post subject: Reply with quote

Easy to machine? Not with the tolerances required for those steel balls or what ever they called them. If those radius holes are too deep then the joint is loose. If they are not deep enough then the joint has a gap.
Plus machining a true spherical hole would be very difficult.
If a ball nose end mill is used, you need to see how they are ground, also the central surface speed is close to nothing, in other words they barely cut at the center of the tool.
They could be EDM cut I suppose, all hole have to be exact or else there will be some that will be loose. I don't think EDM was available in the 40's?
Back in the days of radial engines that system would be far too costly to do, with such tolerance variables.
That's how I see those pictures.
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dpennings



Joined: 10 Dec 2016
Posts: 48

PostPosted: Tue Dec 15, 2020 13:39    Post subject: Reply with quote

I agree on you that it wouldn’t have been suitable for machining technic of the 1940 th, but with today machinery it is no problem at all, because you can mill them all in one clamping position. Neither the surface nor the geometry has to be perfect, the balls are pressing their seat so that the dimples looks polished after the screw is tightened up (the balls are made for ball bearings).

We built an engine with that and never had an issue with that solution, nothing comes loose and the FEM results were also positive.
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rwahlgren



Joined: 15 Aug 2003
Posts: 324

PostPosted: Tue Dec 15, 2020 16:47    Post subject: Reply with quote

To sum it up. What Pratt & Whitney did was the better option, like Kim said.
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dpennings



Joined: 10 Dec 2016
Posts: 48

PostPosted: Wed Dec 16, 2020 04:57    Post subject: Reply with quote

depends, you can't use the P&W solution for Boxer engines with a S-shaped crank shaft because you need to mashine it from the side. When using a divided crank shaft in Boxer engines, S-shape crank shafts are always prefered because of lower cylinder offset and thus lower mass forces, weight and engine length.

The mill has to do very comlex movement for the Gleason Joint compared to the Hirth Joint, not a problem today, but shurly in the 1940 th.

Also, you need higher bolt forces compared to the Hirth or our solution because of flatter angles on the contact surfaces. There must be reasons why the Hirth joint was still in use after the war whereas the Gleason face type seamed to have vanished with the P&W engines.
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rwahlgren



Joined: 15 Aug 2003
Posts: 324

PostPosted: Wed Dec 16, 2020 10:49    Post subject: Reply with quote

"The mill has to do very comlex movement for the Gleason Joint compared to the Hirth Joint, not a problem today, but shurly in the 1940 th. "

The above is what dpennings posted.

And that is the reason it is called a Gleason Joint.
They made the special gear machines to do it.
One of many in the video below.
https://www.youtube.com/watch?v=gj2szHk0OCU

Some history of Gleason.
https://en.wikipedia.org/wiki/Gleason_Corporation
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dpennings



Joined: 10 Dec 2016
Posts: 48

PostPosted: Wed Dec 16, 2020 12:11    Post subject: Reply with quote

I found a lot about their gearing, but nothing more about their joint. I don't see, how you can machine the joint with the machine you referred to, it must be something else.

The Hirth joint is still in use for many non engine applications and can still be found on crank shafts, but only on the front side (Audi, here it is forged, not milled). I couldn't find any other example for the Gleason joint other than the P&W engines.
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rwahlgren



Joined: 15 Aug 2003
Posts: 324

PostPosted: Wed Dec 16, 2020 15:55    Post subject: Reply with quote

dpennings wrote:
I found a lot about their gearing, but nothing more about their joint. I don't see, how you can machine the joint with the machine you referred to, it must be something else.

The Hirth joint is still in use for many non engine applications and can still be found on crank shafts, but only on the front side (Audi, here it is forged, not milled). I couldn't find any other example for the Gleason joint other than the P&W engines.


The video was just one of their machines, to show what they (Gleason) are capable of. No a hypoid gear machine would not be for that application. They made one special for that application (P&W) I'm sure.


This sorta fits into the discussion.
https://www.geartechnology.com/issues/0585x/Tifco.pdf
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rwahlgren



Joined: 15 Aug 2003
Posts: 324

PostPosted: Sun Jan 24, 2021 18:59    Post subject: Reply with quote

Back to Crankcases. The article on this site mentions that the BMW801 used a CAST steel crankcase that was fully machined. Why didn't they forge it?
The cast steel crankcase is still many times stronger than a forged aluminum crankcase, only problem would be inclusions, and porosity, that could lead to cracks and failures. But then all materials can suffer from that.
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kmccutcheon



Joined: 13 Jul 2003
Posts: 298
Location: Huntsville, Alabama USA

PostPosted: Mon Jan 25, 2021 19:14    Post subject: Reply with quote

Quote:
Why didn't they forge it?


Probably because the huge drop hammers necessary to forge such large pieces were in short supply.
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Kimble D. McCutcheon
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dpennings



Joined: 10 Dec 2016
Posts: 48

PostPosted: Tue Jan 26, 2021 07:00    Post subject: Reply with quote

I think, that's true

https://en.wikipedia.org/wiki/Heavy_Press_Program
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kmccutcheon



Joined: 13 Jul 2003
Posts: 298
Location: Huntsville, Alabama USA

PostPosted: Tue Jan 26, 2021 10:38    Post subject: Reply with quote

Quote:
The article on this site mentions that the BMW801 used a CAST steel crankcase that was fully machined.


I've never seen it documented, but they may have been centrifugally cast, which would have given much better material properties than traditional gravity casting. Ford found that its centrifugally cast cylinder barrels were better in all respect than P&W's forged barrels.
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Kimble D. McCutcheon
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wallan



Joined: 13 Jul 2003
Posts: 252
Location: UK

PostPosted: Wed Jan 27, 2021 02:17    Post subject: Reply with quote

BMW 801 cylinders were made from a disc, (slug; looks like a big ice hockey puck) of steel. These were heated and a ram pushed through it into a die to produce what looked like a tankard/beer stein without a handle. A hole was punched through the bottom and the inside pressed out to form a cylinder. This was then placed in a jig, rotated and a tool comprising of discs was pressed against it, to raise, (form) the fins and base, much like high quality threads are raised on fasteners.(better grain structure) I have a .pdf of how they are made. I will post it, later.
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