enginehistory.org Forum Index enginehistory.org
Aircraft Engine Historical Society Members' Bulletin Board
 
 FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups 
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in 

Oil viscosity effect on engine output

 
Post new topic   Reply to topic    enginehistory.org Forum Index -> Technical Discussion
View previous topic :: View next topic  
Author Message
mabbott



Joined: 29 Mar 2010
Posts: 14
Location: Sydney, Australia

PostPosted: Thu Apr 28, 2011 22:26    Post subject: Oil viscosity effect on engine output Reply with quote

interested to know more about the impact of Oil viscosity on aircraft engine output.

The context is; what limits are imposed on the engines output (rpm) due to engine temp (is it a physical limitation due to the oil or is there more to it)?
Back to top
View user's profile Send private message
jschauer



Joined: 19 May 2004
Posts: 93
Location: Justin, Texas

PostPosted: Fri Apr 29, 2011 07:41    Post subject: Reply with quote

Most U.S. designed radial engines are limited to 1,200 rpm until 40C degree oil temp is reached.
Back to top
View user's profile Send private message
mabbott



Joined: 29 Mar 2010
Posts: 14
Location: Sydney, Australia

PostPosted: Sun May 01, 2011 15:28    Post subject: Reply with quote

Thanks jschauer, I should clarify further - were there physical limitations ie. the engine can't be operated over say 1,200 rpm because it can't or could you push the engine over the 1,200 rpm mark but risk engine damage?
Back to top
View user's profile Send private message
rwahlgren



Joined: 15 Aug 2003
Posts: 324

PostPosted: Mon Jun 27, 2011 19:28    Post subject: Reply with quote

It is not that the engine does not have the power to overcome the viscus friction from the thicker lubricant. Its is more that the lubricant does not flow as well when cold and thick as it does when at operating temperature. Remember oil in the average "Large" radial engine is equivalent to SAE 60 and yes it is not a multiviscosity oil, like your 5W-30 you may use in your car, this is very thick oil especialy at temperatures below 40 degrees ambient. Not only is it more difficult to pump it through the smaller passages when cold it also does not so easily fly off the rotating and reciprocating parts either, nor does it like to be tossed up inside the crankcase to lubricate wrist pins, nor scrape off the cylinder walls very fast or find its way back to the scavange pumps, let alone sift through the suction screens to get there. So there is lots more than first thought as to the why it should be restricted in speed till the lube oil warms up.
Back to top
View user's profile Send private message
kmccutcheon



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

PostPosted: Tue Jun 28, 2011 04:40    Post subject: Reply with quote

I have always heard to keep the rpms low until the oil is warm to protect the propeller thrust bearing. It is located in the nose case and is serviced by small oil passages. If run loaded at high speed before lubrication becomes reliable it can be damaged.
_________________
Kimble D. McCutcheon
Back to top
View user's profile Send private message Visit poster's website
Display posts from previous:   
Post new topic   Reply to topic    enginehistory.org Forum Index -> Technical Discussion All times are GMT - 6 Hours
Page 1 of 1

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum


Powered by phpBB © 2001, 2005 phpBB Group