1. "If pushing in reverse and the shear pin gives. The unit will want to rotate suddenly. Will that rotation catch
any other parts? or jam it into the back of tractor?"
The top link's mid section would slide together.. then stop at a point.. the end result being a shorter top
link. The implement would jump some.. but stop before jamming into the back of the tractor. Causing less
damage then a collapsed hitch might cause. Thankyou Tyler"
I think you have that backwards. When pushing in reverse with the tractor/blade, if you hit something & the shear pin goes, the blade will want to tuck down/ under, & the top link will extend. This sets up an uncomfortable position where lifting the 3pt up will not lift the blade - for a while anyhow. so the operator can only push the clutch in to save himself. The 3-point lower arms will rotate up, and I'm not sure where the geomotry will put all the parts if the driver doesn't get that clutch in in time. The blade could actually rotate under the tractor, should the top link limiter also fail in a double-shock load.
Generally tractors have more traction & speed in forward directions than backwards, so forward operations put more strain on the top link. But the whole 3-point is weaker when we use it in reverse, so the shear pin would need to be weak enough to go on the lower rear-ward tension, but not break under normal heavier forwards loads. But some of the worst shock loads could be going over bumps, which is again in the pull-apart mode - which should be weaker... Going to be a balancing act to make that work.
2. You greatly compromise the safety of any pto-powered implement if the upper arm can shorten rapidly. You greatly increase the chance of damaging your tractor pto & shaft if the upper arm can extend rapidly.
3. We sometimes use our tractors for man-lifts, 3pt forklift masts, backhoes, and other difficult, demading, and over-the-limit safety uses. In any of these cases, you want that upper link as solid & dependable as possible. A little 4" 'slam' from the broken shear pin could dump a 700lb load on the tractor seat, an operator on the backhoe seat into the rollbar, etc. You would have some liability issues with these applications - no more so than a hydraulic top link I know, but still something to think about. We live in that type of society.
I hang 1000lb sprayer on the back of a cat 1 tractor. When I hit a furrow, i broke a regular top link once. Will your shear pin take the load? If it does, will it protect the 3-point when I'm blading? What i'm saying is we really, really stress that top link. can you offer protection but allow me to use it to it's fullest need at the same time?
I'm not against your idea - I'm just brainstorming on issues to deal with. /forums/images/graemlins/smile.gif Good luck with the thoughts. /forums/images/graemlins/smile.gif
--->Paul