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Engine basics => Engine set up tips => Topic started by: Steve Helmick on August 25, 2014, 07:57:34 PM
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Just today got pics from Old Harley Guy (who no longer has any mo'sickles) of his .46LA that split the bottom end of the rod. He said it was new this year, never crashed, no reason for it to puke. But it's pretty much trashed, with damaged piston and cylinder. I was just wondering if anybody else has had this happen, because I have not seen or read about this sort of thing happening. There's a 2 year warranty, which should cover it. Let's hope this is a rare deal! y1 Steve
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thats a new one,, I have pealed the chrome on the liner,, never broken any parts and trust me,, my LA 46s have been given every oppurtunity to break stuff
Old Harley guy,, Mike Fitzgerald?
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Define 'split' Steve - did it emanate from an oil hole, bronze bush pushed in too tight perhaps?
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Mark...Yup, the other Fitzgerald!
Chris...Well, it split across the lower end of the hoop...parallel to the crankpin, in line with the rod centerline.
Picture showed no sign of a bushing, as I recall. I would guess that too much press would be a good explaination for the problem. Since the hole in the rod would be reamed, my guess is that the bushing was o/s from the CNC lathe that probably made them. Likely was the last bushing turned before the insert was changed. I'd think those things would go through some sort of high-tech semi-automatic gauge, but I don't know much about what the current technology is. Wouldn't expect a micrometer to be applied to each bushing, anyway. Maybe some sort of go/no go gauge?
Maybe Mike will post the picture, because I didn't save it. Like y'all, I was totally shocked when Mike said it was a .46LA. I was kinda expecting it was a Chinese Super Tigre G.51, because he runs those also. D>K Steve
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I'm curious is he runs the world renown NW LA-46 set-up, that being relitively low rpm on a big 'ol 12.25x3.75 prop? Not being critical here, just it seems to me that that set-up may put more stress on the engine than a smaller prop running at a higher RPM. 8)
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I'm curious is he runs the world renown NW LA-46 set-up, that being relitively low rpm on a big 'ol 12.25x3.75 prop? Not being critical here, just it seems to me that that set-up may put more stress on the engine than a smaller prop running at a higher RPM. 8)
I fly all my 46 LAs on that setup,, its not really low rpm,, I launch at 9800 typically,,
NEVER had this hapen though like I said,, my one 15$ ebay special motor did peal the liner,, after about 350 or 400 flights
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That is relatively high RPM-myth busted. When I tried that prop on the one I am running, did not run it that high. Maybe a second experiment is in order. 8)
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That is relatively high RPM-myth busted. When I tried that prop on the one I am running, did not run it that high. Maybe a second experiment is in order. 8)
The engine is designed to run 14000 rpm all day long. 9800 isn't very fast compared to that.
Brett
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I would guess more than likely a fuel problem.
MM
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We are talking about the relatively unstressed 'lower' end of the rod here and as such stress shouldn't really cause this.
My bet is on a metallurgical fault that has been brought to light by the large inertial load.
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The engine is designed to run 14000 rpm all day long. 9800 isn't very fast compared to that.
Brett
Unless lubrication fails, engines rarely break because of high rpm, more often due to too much load.
L
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I would not be surprised if it wasn't the only one, probably due to o/s rod bushing. Or, maybe the hole was drilled but not reamed? Mucho press, anyway.
This just in! "Hey Steve...I sent that engine with the thrown rod back to Tower...They sent me a new engine... :0) Mike"
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Here's the picture. Pretty complete rod failure, IMO. Where's that bushing? LL~ Steve
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dude! that's a neat failure. it's great tower warrantied the engine. must have been a descent pop!
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Point of interest Steve,
Several of my Magnum .53s have the same bushing elongate & knock like an old Dodge.
John
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What sort of fuel & oil, John? ??? Steve
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I have seen this happen before on R/C pattern engines. It was caused by the bearing being fit to tight on the shaft and galling the bearing from heat. They tend to go down hill from there. We use to take new YS 60's and open up the bushing a bit. That seemt to take care of the problem. We were running 12-9 and 12-10 props that does put a pretty good load on the bottom end.
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It is a contentious point that bushings are of value in a model engine due to the amount of support material around the rod eye that it removes - add oil holes and it could be "tear along the dotted line."
Oil holes on an overhung crank are a mistake in my opinion.
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More info from Mike. The fuel used was PowerMaster GMA 5% x 22% 50/50 castor/synthetic. That's certainly good enough, it easily meets the manufacturer's suggestions. H^^ Steve
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Hi Steve, I have used all synthetic for 15 years add a dash of castor in all my engines, the Magnum .53s are the only ones that knock,,
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John point of reference,, the Magnum in my Avenger uses GMA 10 - 22 ( 10 castor and 11 synth,,)
I have never heard mine knock,,
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I hope yours holds together Marc, most of mine knock even when I used GMA 10% never had another engine knock & for those who know me know I have run many brands of engines more than most. Only the Magnum .53s have knocked for me but none have blown.
On one of them I replaced the rod & opened the oil hole when I had it apart.
Marc , how can yours know you never run them ,,, at least that's what you told me... LL~
Will I see you in Salem tomorrow?