Bent Shaft Question

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  #1  
Old 04-20-05, 05:39 AM
djilles
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Bent Shaft Question

I received a freebie generic pushmower with a Briggs & Stratton 5.0 h.p. verticle shaft engine. It was built in 2000 and is a Quantum. Upon inspection, I found that it has a bent shaft. The bend is between the bottom of the motor and the blade mount. This maybe a stupid question, but can I pull out the shaft and straighten it. I was thinking I could either heat it and bend/hammer it straight or have a tool n die buddy bend it straight. If I was able to accomplish this, and assuming that it was perfectly straight, would it still be safe? Or would the shaft be weakened to the point of being a danger? Thanks for the opportunity to post.
 
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Old 04-20-05, 10:40 AM
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My opinion as well as that of all the major engine manufacturers is that this is a dangerous repair. If you were to put this under the scope before attempting to straighten, you will see it is fractured. Once straightened, the fracture will more than double. Post back with the model, type and code numbers, of the engine, and i'll provide a replacement price for you.
 
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Old 04-20-05, 02:58 PM
djilles
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Model Info

Model: 12F702 Type: 0606-02 Code: 95041256

Thanks for your help.
 
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Old 04-21-05, 01:54 AM
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Ahh! This has a side PTO drive shaft, which means the crank is expensive. Briggs part # 694442, $77.50 list.
 
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Old 04-21-05, 02:00 AM
djilles
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Ouch

That's a bit much. Thanks for your help.
 
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Old 04-21-05, 02:24 AM
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My Dad knows a guy that straightens mower shafts on an arbor press, but I don't think I want a 21" piece of sharpened steel rotating at over 3000 RPM less than 30" from my feet on a weakened shaft......... all I can think of is what happens to a paper clip that is bent a few times.
 
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Old 04-23-05, 01:58 AM
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I must admit that I have straightened a bent shaft. I pulled the motor off the mower and clamped the engine in a vice. I found the high spot on the shaft and beat the #$%& out of it with a heavy rubber mallet (yes the engine was still totally assembled). I got the shaft straightened to within .003". I re-assembled the mower and it ran pretty smoothly. Then I threw it in the garbage. I just wanted to see if I could get it to work. I think it would have lasted a season, but I was pretty sure the crank had some microscopic cracks and my pounding didn't do much good for the crank bearing.
 
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Old 04-23-05, 10:22 PM
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Some people say it's fine to do, others say don't. The manufacturers say don't. Personally, I don't reccomend it, but I also have never seen one broken because of straightening. I've straightened a few but it's not a common practice around my shop.
 
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Old 04-25-05, 05:32 AM
djilles
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Conclusion

I decided to scrap the engine vs. taking any risks. Although, I did disassemble the entire engine to get some experience with the small engine breed.

BTW, I didn't have a fly-wheel puller and didn't want to invest in one, so I cut a piece of 2x4, secured a bolt thru the center, then placed two c-clamps on it for removal of the fly-wheel. It took a few tries, but it worked o.k. for anyone who doesn't have a puller.

I appreciate everyones feedback.
 
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Old 04-25-05, 09:11 PM
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Good call.
 
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