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Engine basics => Engine set up tips => Topic started by: Richard Logston on September 20, 2015, 03:07:00 PM
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I have this O&R 19 side port engine that I am thinking about trying to run on ignition. While looking it over and mounting a prop I noticed that the crank shaft splines will not allow the prop to seat against the drive washer, if I were to force the prop on while tightening the nut the splines would crush into the back of the prop. I have removed the shaft to see if the thrust bearing or spacer was missing. The bearing is there, however it appears that maybe the back part of the bearing is missing. What I have is the center bearing cage with the balls and the cup part over that, there is no cup part on the back side against the crank counter balance. This may sound confusing but don't know a better way to explain it. I figure anyone who has experience with this engine may have run into this problem before. Richard
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This article 'may' help as it generalizes about O&R engine bearings (page 11) -
http://www.antiquemodeler.org/sam_new/news_letters/assets/Thermaleer-1996-11n046.pdf
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Thanks Chris, According to the article it appears I am missing the rear cup part of the bearing. Richard
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Don't know if this helps or not. This is my .23 side port which I would think is about the same and may use the same parts. I pulled the splined thrust washer away from the timer housing for the picture. I need to do a little work on this one. When I tighten a prop on the thrust washer rubs lightly on the timer housing causing just enough friction that the engine won't start. The washer is cupped back a little. I think a whack with the ball peen hammer should fix it.
Dave
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Now the washers removed.
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If I remember right the Ohlsson's only had one race and then the balls ran directly on the crank.
I usually remove those thrust bearings and replace them with a thin bushing of brass or bronze. Sometimes you can find a washer or two that can be modified for the purpose. The reason for replacing them is that they love to come apart in some engines with bad results. Super Cyclones are notorious for destroying piston and cylinders when the parts go through the engine. Most of the later Ohlsson's had caged brass rollers as a rear crankshaft bearing. Those are no problem. I can not tell any degredation in performance after replacing with bushings. I have probably done about 20 of them.
What happens is the thin races in some of those thrust bearings get a groove worn in them from the balls and then they and come apart. I believe the later Atwood Super Champions have thicker races and don't seem to have the problem.
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Thanks all who responded. Very informative reply's! I notice the article referred to by Chris states the crank shaft ball bearing is made up of three parts, two cupped washers, one on each side of the center bearings cage. Jim, you say the bearings only have one cup washer with the bearing running against the crank, which is the way mine is. The idea of replacing the ball bearing with brass washer sounds like a good idea. My first model airplane engine was an O&R 19 side port sparky as a Christmas present. I spent most of the day just holding it in awe. I was a few days later before I could run it since I had to buy a coil, condenser, white gas and 70wt oil. I picked this engine up at a swap meet. It looks almost new and has good compression. I need to come up with a mount adaptor also. By the way my thrust washer is not concaved so it must be some other reason the shaft seems to long and wont allow the prop to fit without the shaft spines crushing the prop. Richard
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The smaller Ohlsson engines do have a 3-piece thrust bearing. The caged balls are faced by hardened steel races. I have never heard of these failing. If the crank splines dig into the prop, it will not harm anything. Use a wood prop, a 9-6 on the O&R 19.
Floyd
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Richard, I have a 23 sideport that is the same way. The splines stick out past the drive washer. I usually ream out just a little of the back side of the prop to clear it. Ohlssons do seem to hold up pretty well. I have three of them. A 60 front intake, a 60 sideport, and the 23. I fly the 23 on a 60" Lanzo Bomber with a radio, and the 60 sideport on an 80" playboy Sr. Lots of hours on both and they still run fine.
It may be that someone took out one of the races on both of our engines as Floyd says they should have both. But, mine was never run when I got it and it had one flat race like yours. My 60 had two cupped races like Floyd says. The very thin flat races like used in the Super Cykes are the ones that fail. I know of at least 4 engines ruined by them. I have a freind that I told this to and he pulled his apart to find it was just about to fail. He replaced it like I do. I have never heard of an Ohlsson failing, but that does not mean they can't. I probably go overboard on some things as I did loose a good running Super Cyke because of the bearing.
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This is a picture showing the splines protruding beyond the drive washer. Richard
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That looks to be a little farther than mine. It could be spaced back a little by adding a shim to the thrust bearing or just making a thicker bushing than the bearing that is in it. As long as the shaft does not hit the back of the case it should be good when you have a prop mounted I would think.
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Well, while we are on the subject of O&R engines, might as well cover this topic also. I have an O&R 23 FR that has not run very well and is hard to needle. After reading the post by Chris Wilson referring to O&R engines in the Thermaleer news letter dated from1996. It talk about filling a notch with solder, smoothing out with file and emery cloth. This prevents leakage in this area. I have posted a picture of this crank showing the notch I think the article is referring to. I understand not all engines had this notch. I'm thinking they must have used cranks notched for spark engines until stock was used up. Am I right in thinking I have an engine with the notch they are referring to.
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Looks like it Richard. I have not seen one like that before. If I remember right the ones I have do not have that cut on them. I have a 29 glow that I believe has an ignition crank in it though.
I just checked another front housing and shaft for I believe a 23 sideport and it does have the double cupped ball races on the thrust bearing. They also look to be a lot heaftier than the Super Cykes. I have two spare shafts and neither one have the undercut, but they are both sideport shafts which would stand to reason. I think the undercut shafts must have been only on front intake models.
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I forgot to mention the the O&R 23 FR shaft has a three pcs bearing, two cup shaped washers around the bearing cage. So I'm pretty sure the O&R 19 is missing one cupped part of the bearing accounting for the shaft to extend to far past the thrust washer. Richard