RocketCityJim · Sep 28, 2000 03:13 PM
#0 sourceLen,
Or any other engine guru out there. Is there an easy way to determine if a crankshaft is bent????? Just wondering!
Rocket City Jim
Crankshafts
Stuka Stunt Main Forum · 9 of 9 known posts recovered
>Len,
>
>Or any other engine guru out
>there. Is there an
>easy way to determine if
>a crankshaft is bent?????
>Just wondering!
>
>Rocket City Jim
>
>Or any other engine guru out
>there. Is there an
>easy way to determine if
>a crankshaft is bent?????
>Just wondering!
>
>Rocket City Jim
Well, if the threaded end is coming out of the wrong side of the engine, you have got a good clue. You can put it on a lathe and use a runout gauge, but, as a simple test, if it is a plain bearing engine, take the engine apart, clean and oil the shaft, and put it back. Then put a prop on it and spin it. If the prop is straight and there is no binding, you should be OK. If the prop wobbles, the threaded end is bent. If the shaft binds in the case, you have another problem. Usually it is the threaded end that bends--the weak link, you know. For a ball bearing supported shaft you can oil it and try the prop spin as above. That will test for bent front end. If there is binding, however, you won't know if it is the shaft or the bearings, although, in this case, it is usually the bearings (or both).
Leonard Neumann
LAST EDITED ON Sep-28-00 AT 04:17 PM (EST)
Also if there is slight binding on the BB version ,there is a likelyhood that the crankcase is warped and the bearings are no longer parallel or concentric. You can get this condition and not bend the shaft.
Bigiron
Steve Helmick · Oct 24, 2000 10:02 PM
#3 sourceHere's something that SHOULD work pretty well. Mount your engine on a test stand...good & rigid. You could actually do this on a
Black & Decker Workmate or similar, 'cause you don't have to run the engine. Take the backplate off, prop, prop driver, etc. Get a buddy with an electric drill with a pencil chucked up, eraser out. Stick the eraser down the shaft hole and have your buddy spin 'er up. Hold the end of your thumbnail against the round part of the shaft as far forward as possible. If you feel a pulsing, it is bent. That's as close to a "dial indicator" as we
have without spending money. If there is a "center" in the end of the prop stud, put a pen, pencil or scribe in the center and if it vibrates, it also indicates a bent crank. Steve
Black & Decker Workmate or similar, 'cause you don't have to run the engine. Take the backplate off, prop, prop driver, etc. Get a buddy with an electric drill with a pencil chucked up, eraser out. Stick the eraser down the shaft hole and have your buddy spin 'er up. Hold the end of your thumbnail against the round part of the shaft as far forward as possible. If you feel a pulsing, it is bent. That's as close to a "dial indicator" as we
have without spending money. If there is a "center" in the end of the prop stud, put a pen, pencil or scribe in the center and if it vibrates, it also indicates a bent crank. Steve
LAST EDITED ON Oct-26-00 AT 00:34 AM (EST)
LAST EDITED ON Oct-26-00 AT 00:27 AM (EST)
LAST EDITED ON Oct-26-00 AT 00:25 AM (EST)
Well, the obvious thing is, if you can't tell if it's bent, put it on a sturdy test stand and run it. If it vibrates (meaning a lot more than usual), it's bent. I've done this with engines that I just couldn't tell by other methods if the darn thing was bent or not. Just a little (much less than a degree) will show up. Might trash the bearings this way, but if it's bent, they are getting changed out anyway.
Not necessarily recommended. Do at you're own risk (this is the discalimer part)
I just sent a PA.61 to Randy Smith for a bent crank. But in this case, it was pretty obvious. I could see the thrust washer wobbling just turning the prop. We think UPS lost the engine though. And the hits just keep on coming!
Randy
Randy,
If that's the P.A. I think it is I'm sure not surpried the crank is bent! Did you know you can put a trace on UPS shipments throught thier web site? It will show where it went & when & give you an ETA. Sorry to hear you're having rotten luck on top of rotten luck :/ That sure was a nice paint job on that SV. See ya in the spring.
Nils
If that's the P.A. I think it is I'm sure not surpried the crank is bent! Did you know you can put a trace on UPS shipments throught thier web site? It will show where it went & when & give you an ETA. Sorry to hear you're having rotten luck on top of rotten luck :/ That sure was a nice paint job on that SV. See ya in the spring.
Nils
Nils,
I did the trace. UPS claims they delivered it to Smith. smith says he didn't get it.
Beats me.
Randy
Now, back to you're regularly scheduled topic.
Steve Helmick · Oct 26, 2000 10:38 PM
#8 sourceRandy, chances are pretty good that UPS is right. I had the same thing happen with a stainless boat prop that is worth more than your PA. It turned out they found it in the shop, it just hadn't been logged in per SOP, as it came at lunch time or something. It
will show up! At least it's not April! Steve
will show up! At least it's not April! Steve
There are inexpensive Chinese made dial indicators we have used for 10-20$. THis is the best way to check shaft runout.
Production Tool Supply, Grainger, MSC, etc. usually have inexpensive indicator lines.
We use them for throw-aways for checking large robot positioning repeatability. every once in awhile, there is an OOPS! and the dial indicator gets SMASHED!