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Help with Rag Joints in drive shaft

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#1 glgrumpy OFFLINE  


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Posted March 22, 2015 - 08:53 PM

Some know I have two new Speedex tractors, both same 1622 model with Briggs and hydro drive. Took one apart to work on  engine. Found the shaft adapter thing on hydro side had been loose and running amok for awhile. Keyway shot and set-screw hole messed up in the adapter, and hole in shaft messed up also, but keyway is good.


  SO, today took apart second tractor to get adaptor. All was good once off. Clean keyway, TWO set screws in it. One was above the key, other about  90* from it. Other broken one had only ONE set-screw opposite of the key side. The better adapter seems it will have setscrew hit the shaft in a clear spot. Should I drill a shallow divet there for it?  Other shaft has a shallow hole where it was. It's kinda close to mushed hole from old screw, so don't want to drill much, or maybe better not at all?


Now to rag part. Found the center shaft part was about 1/2" shorter than the one I'm working on, find that odd as same model tractor. It had a thicker 2-layer rag joint on one end, and a single one on other. The tractor I'm working on was already apart there and not sure what it had for joints. SO, going to use the longer shaft as it was in tractor, and wondering if there is even any reason to keep joints in any order on the thickness question?   I'm hoping all this lines up when bolted in. I realize there is some movement allowed on the fiber joints, but how much is too much? Should it be a straight looking flat joint, relaxed when not running to be right? I'm thinking the adapters on each shaft cannot be moved in/out and are pretty much set. SO, any space between the shaft adapters have to be where I make it thicker or thinner to fit?  The middle shaft and adapter ends are real short, about 8 to 10" kinda guessing here, didn't measure. That one is shorter if I should need it, but am going with the longe one for my try-out.  Any Guidance here for what I am working with?  Only other joint like this I worked on was a Cub Cadet, and it was only one end, think other end was allowed to move maybe? can't recall.

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#2 classic OFFLINE  

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Posted March 22, 2015 - 11:10 PM

It wouldn't be good to have rag joints under stress when bolted in place. If they are under stress when installed, they will flex with every revolution of the driveshaft. Tighten down the driveshaft with the engine mounting bolts loose, then rotate the engine. Tighten the engine bolts last when you see that the rag joints aren't stressed.
We use Paraflex Elements at work to couple large electric motors to heavy fans and gear drives.The element looks similar to a wheel barrow tire and is made out of rubber. There are clamping hubs on the motor shaft and fan shaft that hold the element in place. The element will slip and burn up if the motor or the fan stop abruptly. If the element hubs are out of alignment when installed, it causes the element to flex, overheat, crack, and fail prematurely. There are acceptable tolerances for misalignment, but I like to have everything dead nuts. I've seen these rubber elements fail due to misalignment.

Edited by classic, March 22, 2015 - 11:11 PM.

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