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Jinma Feed Roller Shaft Mod Question

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metastable
Join Date: Apr 2004
Posts: 78 North Plains, OR
TractorPoint Premium Member -- 5 Tractors = Very Frequent Poster

2005-06-04          111946


The main weakness of the Jinma JM6 wood chipper is the feed roller drive shaft--this has been discussed here before. Last week, the universal joint nearest the gear box sheared off during normal use. I got new parts from tractors4you.com and put them in. No more than 30 minutes went by, and the new joint sheared off. So, I started looking for the real source of the problem, and discovered that these joints are poorly designed, and bind during normal operation. Nothing else is binding or catching. Here is what I am thinking: The square stock on the feed roller is 1/2"--the same as a 1/2" socket drive. Why not remove the spring clips and joints from the existing drive shaft and weld a 1/2" impact wrench universal joint to each end of the shaft? The modification would be extremely easy, and those joints don't bind. Anyone see a problem with this? Any recommendations for a brand of universal joint that can be welded and can handle the torque?

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Jinma Feed Roller Shaft Mod Question

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kwschumm
Join Date: Feb 2003
Posts: 5764 NW Oregon
TractorPoint Premium Member -- 5 Tractors = Very Frequent Poster  View my Photos  Pics

2005-06-04          111948


I believe the big problem is that the female square end can cock and cause the male end to round off and eventually shear. The female square end of the driveshaft has two holes in it that can be tapped for set screws. That should keep it from sliding back and cocking. It looks like it was designed for this but for some reason they didn't bother.

I've also heard that an automotive steering shaft, which already has universal joints on each end, could be adapted fairly easily by a guy who can weld. ....

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Jinma Feed Roller Shaft Mod Question

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metastable
Join Date: Apr 2004
Posts: 78 North Plains, OR
TractorPoint Premium Member -- 5 Tractors = Very Frequent Poster

2005-06-13          112326


Modification done. Removed the male knuckles from each end of the shaft, and tig welded a 1/2" impact wrench u-joint to each end. Had to cut 3/4" from the telescopic part of the shaft for overall length. Using larger u-joints might put too much stress on the gearbox--would rather shear the shaft. I also loosened the belt to slip when bound up. $14 total. Ran for several hours without incident. ....


Link:   U-Joints

 
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Jinma Feed Roller Shaft Mod Question

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kwschumm
Join Date: Feb 2003
Posts: 5764 NW Oregon
TractorPoint Premium Member -- 5 Tractors = Very Frequent Poster  View my Photos  Pics

2005-06-13          112329


That's a good idea. You're right, those gearboxes look sort of puny for the job they do. Hope it holds up. One of these days I have to learn to weld. ....

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Jinma Feed Roller Shaft Mod Question

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vtorange
Join Date: Dec 2003
Posts: 1 Midwestern Vermont
TractorPoint Premium Member -- 5 Tractors = Very Frequent Poster

2005-10-25          118402


How about a few pictures of the completed mod. I would be interested in how and where the u-joints were mounted to the shafts.
Thanks
Al ....

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Jinma Feed Roller Shaft Mod Question

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metastable
Join Date: Apr 2004
Posts: 78 North Plains, OR
TractorPoint Premium Member -- 5 Tractors = Very Frequent Poster

2005-10-31          118714


I would post some pics, but I have no way of doing that. If I find a digital camera, I'll get a few posted.

Basically, just center the male end of the U-joints into the socket of the drive shaft. Weld it in place. Do this on both ends. This will leave the female ends of the U-joints open to slip over the square shafts on the chipper.

When done, you'll dind that the shaft is about 3/4" too long. Just use a cutting wheel to shorten it a bit.

I found that the pin in the U-joints I listed were soft. They will eventually shear. THIS IS OK! Just replace them with a 1/4"x1.25" bolt and nylon lock nut (direct replacement). If you use a relatively soft bolt, it will act as a shear pin, and is easy/cheap to replace compared to the Jinma knuckles. I would discourage using a grade-8 bolt since something else will break before the bolt does.

....

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Jinma Feed Roller Shaft Mod Question

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CharlieNH
Join Date: Nov 2007
Posts: 4 Lincoln MA and Madison NH
TractorPoint Premium Member -- 5 Tractors = Very Frequent Poster

2007-11-13          148175


I was wondering how the universal joints from the impact sockets have held up over time. I like the idea of using the pin as a shear pin in the system. Have any pictures ever been posted on this?
Thanks. ....

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