Slip Clutch or Shearpin Yoke

[WayneB]

I have a single row potato digger and a few days ago I went out to see just how well it would work. Last for about four to five feet and the track was not aligned properly and all of a sudden it moved / shifted to one side jammed up the track and broke the drive chain.

The bearing actually moved about 1/2" when the track locked up and the shaft was bent about the same amount.

With further inspection I realized there was more damage than just the chain. The shaft coming out of the gearbox was actually bent.

We were able to take the gear box apart (remove the shaft and gears) and removed the shaft. Using about 5 ton of pressure in the press we were able to straighten the shaft and then reassembly the unit.

(there are four bolts that hold the gearbox onto the frame and then two bolts that hold the bearing on the out side near the sprocket) The two blue straps have been replaced with chains that permit adjusting the lift of the rear of the digger.

Although it seems to be turning smoothly now my major fear is that it could have done major damage to the tractor PTO end of the business which would have been many more dollars to fix.

There are some complications with the installation mainly the distance from the PTO out put of the tractor to the input on the gearbox. This is really short and somewhat of a major angle as well. I am concerned about spacing that would accept a slip clutch.

I am also worried that maybe a slip clutch might not be the best way to go as if the track sould do the same thing again I would rather have a shearpin shearbolt in the yoke of the PTO shaft that would break under too much pressure. This would stop the motion of the machine and not damage the gearbox, or the PTO drive on the tractor.

Not sure which way to go an open for any suggestions, that is for sure. A bit afraid to just hook everything up and head back out without some sort of protection.

Wayne

 

[sweettractors]

I can provide a driveshaft with slipclutch built in (like on a roto tiller) This would be more compact that a add-on clutch. 1 3/8 inch 6 spline to 1 3/8 inch 6 spline. Ken Sweet

 

[BeezFun]

I think the problem is that the top link appears to be fixed. If the rear wheels are on the ground and you try to lower the front edge of the picker into the ground, the support elements connected to the top link have to bend to accomodate that motion (or something has to bend, in this case the support elements appear to be the weakest part of the setup). Once they start to bend it would distort the top of the implement to the side. For something like this I would think you'd want a hydraulic top link that you could put in float mode, or a chain instead of a top link that would allow you to lift the front edge up, but would allow it to drop without forcing the top frame to bend. I would guess all the other damage was due to the implement being forced to flex.

It's probably still a good idea to add some kind of shear pin or slip clutch, but I don't think it would have helped in this case.

 

[leonz]

I have a single row potato digger and a few days ago I went out to see just how well it would work. Last for about four to five feet and the track was not aligned properly and all of a sudden it moved / shifted to one side jammed up the track and broke the drive chain.

The bearing actually moved about 1/2" when the track locked up and the shaft was bent about the same amount.

With further inspection I realized there was more damage than just the chain. The shaft coming out of the gearbox was actually bent.

We were able to take the gear box apart (remove the shaft and gears) and removed the shaft. Using about 5 ton of pressure in the press we were able to straighten the shaft and then reassembly the unit.

(there are four bolts that hold the gearbox onto the frame and then two bolts that hold the bearing on the out side near the sprocket) The two blue straps have been replaced with chains that permit adjusting the lift of the rear of the digger.

Although it seems to be turning smoothly now my major fear is that it could have done major damage to the tractor PTO end of the business which would have been many more dollars to fix.

There are some complications with the installation mainly the distance from the PTO out put of the tractor to the input on the gearbox. This is really short and somewhat of a major angle as well. I am concerned about spacing that would accept a slip clutch.

I am also worried that maybe a slip clutch might not be the best way to go as if the track sould do the same thing again I would rather have a shearpin shearbolt in the yoke of the PTO shaft that would break under too much pressure. This would stop the motion of the machine and not damage the gearbox, or the PTO drive on the tractor.

Not sure which way to go an open for any suggestions, that is for sure. A bit afraid to just hook everything up and head back out without some sort of protection.

Wayne

Were you in a creeper gear when digging?


The chains you installed to the top link point need to be replaced with thicker steel straps 3/8 - 1/2 by 3 inch strap iron should be
bolted to the top link and the walls of the digger.



Buy the slip clutch from Ken- just be sure to measure the distance between the tracors PTO stub where the locking pin groove is to the locking pin groove on the digger with the digger fully elevated.

1. you need either an adjustable top link or the hydraulic top link to adjust the digger as already mentioned due to the wanderlust issues of the potato digger and meeting resistance while digging as discussed earlier.

2. about the lower links on your three point hitch- are the turnbuckles tight?



My other concern is simply this- is this digger ment for hilled potatoes rather than flat land potatos? the design looks like it was ment for ridge tilled/hilled potatoes which would explain the problems when sucking in below grade.

You may end up welding a pair of fluted coulters on stub shafts tot he front of the digger sidewalls to cut in and allow the teeth to suck in the row with the cuts created by the coulters.

You may end up building a ridge till system for potatoes building hills in the fall and splitting them in half to meet the other half of the next rows dirt to make the new hill after dropping the seed potatoes and burying them at the same time.

It may just pay to replace and upgrade your older 3 point hitch with a new top link and adjustable right link with the crank and the anti-sway chains.

You need a stronger mounting system on the digging and or plan on changing the tillage method using a hiller furrower tool bar to plant potato's which would be near the ground surface when planted the chains may not stop it from swaying.

 

[WayneB]

Thank you for the quick responses and good advice.

1.) Back wheels have been replaced with wheels that actually rotate, so when on the ground they will turn to the right or left and not bend like the wheel did in the last picture. (That my stupidity because I moved the tractor in the yard known the wheels were on the ground, should have thought that through)

2.) The metal (blue) straps have been replaced with link chain plus a swing rotating arm so the front of the digger will pitch down properly and the chains can pick up the rear of the digger when moving from one place to another.

3.) The upper link of the digger I have added a flex piece so that it permits the chains to swing and the rear of the digger to pitch when digging. All of the potatoes are hilled so I think the angle and depth of the front is okay?

This the the linkage that bent during the jam up of the drive chain. I will contact Ken and discuss the slipclutch requirement further and also open to a shearbolt yoke approach. I have that on my woods snowblower and it seems to work fine for that application?

The shaft is approximately 13 inches long the bolts holding the bearing slipped during the jam and permited the shaft to bend. There was no damage to the gears in the gearbox so all the damage was right at the shaft.

 

[patrick_g]

Opinions are like... Oh well, here's mine... A shear pin strong enough to get the job done will transmit a greater shock load to the tractor's PTO before relieving than a slip clutch. A slip clutch, in my opinion, is the better choice if a few bucks is not an overriding concern.

I have shear bolts in my PHD and a slip clutch on my 6 ft brush hog. The shear bolts are a royal pain and do incremental damager to the "protected" parts. The slip clutch has been doing fine for at least 7 years of hard abuse while I seem to use the 6 ft brush hog for a angle grinder to level the ground, bust rocks, and such (along with a little mowing and taking down trees up to 5 in in diameter.

Brush hog is rated for 85 HP. Tractor is rated for 39 HP.

Pat

 

[sweettractors]

Some sort of front gauge wheels in front would prevent the suction. Ken Sweet