Lawnmowr heaven?

Well I finally did it...I managed to bend the driveshaft of my push lawnmower after rolling over a tree stump. The mower has two choices...to be bent back in shape or off to the dump. It has served me well for ten years. I found the 5 HP Tecumse Motor in an estate sale (new in box) and built the rest from what I could find in my Brother in laws barn...frame, wheels etc... It still runs after hitting the tree stump, but vibrates a lot. Is there any cold work process that would bring it back to straight or semistraight?...I am thinking sledge hammer....again this is a throw away lawn mower. I'm a welder by trade and am aftraid to use heat on the shaft for fear of annealing it...thoughts?...am I hooped and I have a boat anchor going to lawnmower heaven?...or should I just "runner" till the crank bearings give way.. Thanks...Jim

Reply to
Jim
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I would try to attach a safe counterweight securely.

i
Reply to
Ignoramus6365

You can probably bend it back (since it's a throwaway) by removing the blade, then slipping a long length of pipe over the shaft, brace the motor/deck securely, and push down on the pipe to straighten the shaft. This should bend it where it exits the motor. Running it while bent will just tear up the seal on the bottom end and you'll lose the oil, then the motor. I wouldn't beat on it with a sledge, but bending it with a pipe lever is a kinder, genteler method. Of course, keep checking as you progress until nearly perfect. HTH Ken.

Reply to
Ken Sterling

This is a common topic of heated discussion on alt.home.repair. From personal experience I can tell you that it is possible (but not guaranteed) to straighten the crankshaft. Some mower shops have a special fixture for this which supports, bends, and measures. I have straightened several with a dial indicator and a long pipe, sometimes aided by a heavy hammer. Straightening is no problem but holding the engine can be tough. I currently have a 3.5HP Tecumseh whose shaft has been straightened 3 times over about 5 years and is still running good.

That said, it is still possible to break the shaft or damage the bearing. Some engines have cast iron crankshafts which would probably break.

Don Young

Reply to
Don Young

A BFH will do the job. That's what I did with mine 5 years ago and still running. Only removed the blade and use a dial indicator

Reply to
Ralph Henrichs

My dad repaired mowers after retirement from Pontiac Motors. He made a crank straightener by attaching a heavy angle iron with a 3/4" tapped hole for a "pusher" bolt underneath an old cast aluminum mower deck. Mount your motor on the deck, put a piece of brass between the bolt and the high spot of the crank, turn bolt to bend crank. Worked great.

Reply to
syoung

The shaft is unlikely to be heat treated in the first place. Cold bend it back into line and get on with the lawn.

Cheers Trevor Jones

Reply to
Trevor Jones

Driveshaft??

Or crankshaft on the engine?

If it bends back, have at. I'd not use heat on the crankshaft as I'd expect to end up with a Z bend in it rather than straight. Best results would be to rip it out and do it on a press.

Cheers Trevor Jones

Reply to
Trevor Jones

Are you absolutely sure the crank is bent? I'd check the blade first, or have you already replaced that? If you have not changed the blade for a known-good one, there's no way I'd start bending things on the engine. It could be bent, but you couldn't tell. Some of these engines will run without a blade, others made specifically for mower use don't have enough flywheel weight to start. If you can start it without the blade, then you can get some idea whether the crank is bent. If you have access to a dial indicator and mount, you could indicate the shaft to see how much bend there is.

Jon

Reply to
Jon Elson

Tecumseh shafts DO bend - and more easily than the blade. I now have a "belt drive" mower - if the blade gets hold of a hunk of rebat, lanscape timber, ow whatever it just bends the mower spindle - a lot cheaper than an engine crankshaft.

Reply to
clare at snyder.on.ca

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