Chipper Jinma Chipper Self Destruct

[Smalljobs]

The new flywheel is here but the flywheel is bolted to a flange on the end of the main shaft and the heads are on the back side. The knife replacement port allows access to these bolt heads with a box wrench so there is no issue in removing the flywheel. Installing the new one should be straightforward but it's impossible to get a torque wrench on the bolts. Even if I enlarged the access port, the main shaft pillow blocks are in the way.

I'm thinking about welding a socket on the end of the box wrench to make a torque wrench cheater or multiplier bar. Has anybody replaced one of these?

The obvious way is to remove the multi-belt pulley, the main shaft, both pillow blocks, etc., allowing removal of the entire shaft and flywheel as one unit. Then it would be easy to remount and torque the flywheel. This would be a time consuming job; however, on the other hand the consequence of not doing it correctly is self destruction.

Will use new bolts, red Loctite, and torque wrench.

 

[ericm979]

Would a crows foot help?


If you make an extension and keep it (or the crows foot) at 90 degrees to the torque wrench you don't need to do math to get the true torque value.

 

[Smalljobs]

Eric,
Thanks. A box wrench is the most compact and secure way to grab the nut. BUT.....you're right, a crow foot just might work and just give the offset I need to gain access with a torque wrench. I think I'll check dimensions of 18 mm crow foot (feet?), make a cardboard model, and go from there. Thanks!!!!

I ordered a couple of shallow 18 mm sockets and maybe I could make or weld a crow foot of some sort right on to the socket or right next to a box wrench. By doing it via your way or something similar, I can avoid that long torque wrench multiplier bar.

 

[Smalljobs]

The chipper is now back and running again with around 3 hours of time on it. Rather than post a lot of pictures, here's how we resolved it:

It was almost impossible to separate the flywheel from the main shaft, so the machine was stripped down to only the main frame with upper and lower shafts still attached. The multi belt drive pulley and pillow blocks were frozen to the main shaft as well. Even with heating the flywheel hub to cherry red, the flywheel could not be removed.

As a last resort, a torch was used to cut approximately an 8" X 8" hole on the panel where the flywheel shaft passes through. This allowed the entire shaft, two pillow blocks and multi belt pulley to be removed as a unit. A hydraulic press was used to separate all the parts. The hole was then welded back together, ground flat, and repainted.

The machine needed a new flywheel which came with new knives. The flywheel mounting flange was found to be cupped or dished outward by around .004 and there was a lot of metal movement at the mounting holes. I replaced the shaft and pillow block bearings, too.

This was a close decision to repair it or scrap it in favor of a new machine.

 

[Gordon Gould]

Sounds like it is as good as new now with that level of repair. :thumbsup:

gg

 

[5030]

Had one and sold it last year. Got what I paid for it new actually. I won't use the import hold down bolts, I use Fastenal high strength countersunk hold down bolts and insert nuts instead. Never had an issue with mine and I happen to sharpen chipper knives on the side for commercial tree outfits so my knives were always razor sharp. I also adjusted the included angle on mine from the aggressive 29.5 degrees to a flatter 25 degrees.

Looking at that knife, I'd say it was bad heat treat. They have to be through hardened but then stress relieved of they will fracture. You can actually 'normalize them' yourself in your wife's oven (if it's electric). Normalization of through hardened steel takes about 450 degrees for an hour or so with a gradual cool down to ambient.

 

[grsthegreat]

Weird... ive been using mine for about 14 years without any issues. Have both resharpened and replaced knives snd anvil. Always torque bolts.

Hope it stays that way. I have very little bad things to say about the chipper. I use it at least 2 dozen times per season running about 4 hours per session. So its not like a commercial operation to say the least. If i ran it continually you better believe i would not be using a Chinese machine

 

[Smalljobs]

I had no problems with this for years. A final post mortem and thinking about the root cause is that the anvil or knife or both cracked from hole to hole along the length...from a small stone last summer I think. As the crack progressed the anvil final separated and ran into the knives flying by and eventually tore off both of them. Flying debris took a chunk off the back of the flywheel.

I use new flathead bolts, 10.9, from McMaster-Carr along with 10.9 flanged locking nuts, with red Loctite, all torqued evenly and incrementally.

One needs heavy tools to repair one of these. Fortunately I have an engine hoist, impact wrench, two torque wrenches, feeler gages, and 1/2" drive sockets.

Total out of pocket cost was around $1,000 plus around 40 hours of my time. The $ outlay could have been reduced somewhat if I sent the main shaft out for "truing up" but I was concerned enough to buy a new one when you think of all the labor to repair it. The outside acetylene work, welding it back together, and hydraulic press work was a fair $385. I could have saved a little by doing the welding myself but there was no way easy way to remove everything without a torch and press.

 

[grsthegreat]

they are a bear to work on thats for sure. not too much wiggle room in them. my knives are starting to get dull...i just hope to make it thru the rest of my chipping season without swapping them out. thats a real pain in the butt to do.

 

[5030]

In my unbiased opinion, the one thing I never liked about the Jinma chippers, was the in feed mechanism with the crude spring loaded driveshaft and the single serrated roller. Very crude and not very reliable, I see outfits like Woodmax have improved on the design quite a bit, Must have instructed their Chinese builders to modify them....

Other than that, not really a bad unit, especially when powered with a 90 horse tractor. I installed a Weasler slip clutch on the one I had in as much as I was inputting about 3 times the recommended PTO power recommended. Never had an issue but I did slip the clutch once in a while. with a big knot.