Mailing List flyrotary@lancaironline.net Message #22247
From: Ed Anderson <eanderson@carolina.rr.com>
Subject: Re: [FlyRotary] Re: Seized 13b
Date: Sat, 21 May 2005 15:34:44 -0400
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
 E. Hanover 
Lynn, I understand what you are talking about with respect to the bearings. Ed Anderson said there was some problem (not really identified as to what) that would cause the engine to run for as long as 20 seconds with no oil pressure! I know if you or I had an engine that wasn't showing oil pressure in 5 seconds we would be tearing it down to find out what was wrong. Ed said this was happening almost every time he started it, even when hot/warm. the engine should be primed at that point with oil pressure instantly, so something was very screwed up. He had run it for some time like that so the bearings were taking a beating at every engine start. The engine had to be pretty tough to hold up as long as it did. Your jointer example probably didn't run up to 2K rpm on start up every time either. A very small film will work for some time, but higher surface speeds require more lubrication at all times. Or perhaps I should clarify, they require the oil pressure to "float" the bearing. In a close fitted plain bearing wery little oil runs through at a given time. It depends on the design clearance.
Bill Jepson
 
 
 
Wait Bill, I am not certain if you are referring to MY oil system or what I reported on from Andy on HIS oil system{:>).
 
My personal opinion is that Andy's use of a rubber hose on the suction side for the oil pickup was destined for problems - either an air leak or the hose partially collapsing from the heat and suction - but, that is just my opinion.
 
I think my view is identical to yours, Bill,  regarding delay in oil pressure build up, towit in my original message:
 
Now, I for one would consider it a problem if I couldn't  get oil pressure within 1-2 seconds  of firing up the engine (regardless of orientation) , I would cringe thinking of metal on metal rubbing, heating, eroding, etc.  I couldn't stand it and would have to fix it. 
 
I did identify some of the things that could cause  a problem in any oil pickup including the ordinary pick up if you are not careful
 
 But that applies  to the pickups in the auto orientation as well.  If you have a leak (didn't use a gasket, sealant, hole in the pickup tube, stuff stuck on your screen, etc) on the suction side, you are going to have trouble getting oil pressure quickly. 
 
 
  I have fortunately never had any oil problems (if you don't count the time I did not get the key situated properly on the oil pump shaft {:>)) and certainly would not tolerate a 20 +second lag in oil pressure.  But, I do pay careful attention that my metal plate is sealed as well as bolted to the oil pickup opening.  My metal tubes actually extends approx 1/2" into the oil pickup hole.
 
Ed A
 
 
 
 
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