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Bent Driveshafts?


maxtorman1234

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I got looking at my driveshafts on a couple tractors when running, and I've noticed that 2 wobble pretty bad. I know both ends are bolted tight. What would cause the driveshafts to bend? I know that my 716H has never had any attachments on it except the deck, but I have no idea what my 416H was used for. Does anybody else have this problem? I don't hear about too many driveshafts bending, so I think it must just be a coincidence almost all of mine are bent.
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I have a friend that the fiber disc broke and it bent the drive shaft on his.Maybe sometime or another this might of happen and they just put it back together.Just a idea.Tony
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Graham, it's pretty tough to make these shafts without a little bow and I don't know how critical Simplicity would treat this. However I do know that much of a bow at engine speed would make for a lot of stress on the BVG input shaft and bearings. So I'd straighten or replace it if it was off much. Frankly I'm surprised they hold up as well as they do.
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I have broken a few disc's and bent a few drive shafts. I bought one new one and straightened the others. The new ones are not perfect. I straightened the bent ones by rolling on a flat surface and marking the high spot then placing the shaft on some steel blocks one on each side of the high spot with the high spot up hitting it with a hammer. After you have it fairly straight make sure the ears are parallel to each other. Then you can put the shaft in some V blocks and check with a dial indicator and marking the high spots and taping accordingly until with in a couple of thousands of straight. If I remember right the new shaft was out over 10 thousands. Finally check the ears for parallel.
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My A-C 916H was formerly owned by my school district, before I bought through a surplus auction. Needless to say the tractor has alot of hours on it. Last winter while replacing the blown 16HP Kohler K341 in it with a brand new 16HP Kohler Magnum, I noticed that the allen screw on the BGB end of the driveshaft worked itself loose. It looks like the tractor was used a long time like this, because the keyway on the BGB has been widened out. I tightened the key up. I now have 14 hours on the new engine and I checked the allen screw. It worked itself loose again, but the driveshaft appears to be staying on.
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My fiber disc had the holes elongated and this caused the shaft to wobble. You have to remove the shaft to check this. I have also had the input shaft yoke set screw work loose and it was worn internally enough to cause a bad wobble. I heard a bad metallic clcking noise when it was running and I thought I had broken the BGB gear teeth, it was the worn yoke clanging around. Grasp the BGB end of the shaft and see if any movement is noticable you should have just a very small bit of play.
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I figured it might be hard to straighten them, but I was also thinking that if they bend so easy, i might try to use 7/8" hard steel and weld the ends on.
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Graham, I don't think I would worry to much about small bends or wabbles unless there is a noticeable vibration.Straighten them as much as you can.Shim the fiber discs so that there is no warpage once everything is lined up and you should be alright.
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