Warbird Man

My Feedback: (95)

I picked up an engine that got a little shipping damage (bent fins)
So I decided to get a dial indicator and check the crank shaft. I'm getting a variation of .003.
Is that considered bent or is that tolerable?

Cyberwolf

My Feedback: (4)

What kind of engine and just where is the run out? The actual crankshaft or the hub bolt.

Warbird Man

My Feedback: (95)

Zenoha G-62 rear shaft @ end.

I think front (hub side) ok, I haven't been able to remove front hub to check it. The two bolts are on extremely tight.
Shipping damage was on rear side.

Would like to put a spring starter on it

CK1

My Feedback: (60)

.003 runout at the crank itself would be the maximum I would want on any engine . Anything over .002 is usualy considered out of spec.
If you plan on using the spring starter both ends of the crank need to be true. If you are capable of making your own engine repairs the crank in a G62 is not difficult to replace after you get the hub loose and the inner race of the spring starter off the crankshaft. Parts are easily found at Daves discount motors
http://www.davesmotors.com/Products/G62PU-Engine-Parts

skillet92

I might run it first before I would do anything. Kinda hard to believe that while shipping a crank got bent. If they bend that easy we would have more problems. I have almost a dozen 20cc up to 60cc twin and the only crank I ever bent was on a g38 that went nose in from a good height. And I fly plenty of warbirds that have had nose overs with no bent cranks. Just my 2 cents.

earlwb

In my opinion you are OK the .003 inch wobble is likely well within their specs for the engine. The non-prop driving side of the engine doesn't get the attention that the other prop-driving side of the engine gets.

The utility engine designs tend to allow for quite a variation in tolerances so the .003 inch thus that wobble may be perfectly fine for it. A more precise engine design may have more tight tolerances, but even then the .003 may be OK too. I would test run the engine and see how it does. One problem is the gasoline engines tend to all vibrate more anyway so that .003 wobble may be fine in anycase.  Oh yeah, made using "less exacting tolerances" is the phrase they tend to say about them. Plus if it is not the propeller shaft side of the engine, then they usually don't care much, if any, about additional wobble there. The propeller shaft side of the engine with the flywheel and magneto needs more tight or exacting tolerances as a tiny wobble there can really magnify the vibrations and reduce power more.

Many of the low end trimmer engines, etc., use a pressed steel and or stamped steel crankshaft and can be pretty liberal on their tolerances for what is Ok and not Ok as to measurements.

Now then the better made for RC high performance gasoline engines are made to much more exacting tolerances as that yields more performance, etc.  But most of them went with cantilever crankshafts supported on only one side and dropped having a full length crankshaft.

Cyberwolf

My Feedback: (4)

A G-62 crank is in 3 pieces and it may not have been fully dialed in from the factory, I have seen that before. Dropping the engine just almost can't bend the crank as a rule they don't bend anyway, but a prop strike can twist one out of line and cause it to run out.
.003 will make a spinner wobble and a prop not track true, but the good news is they can be fixed W/O allot of hassle or money.
Another feature I like about the G-62 is that fact you can end for end the crankshaft if ever anything happens to the one end and go again as long as it is aligned .

Warbird Man

My Feedback: (95)

Thanks for all the info.
I'm getting .003 on the rear shaft and alittle more that .003 on the prop end. I think I'll change it out.