Stump shredder project

[wiscwhip]

The idea is that these will fail before I bend one of the pins should it come to that.

I know my swing cylinder is capable of lifting the tractor and then some. It could rip the swivel bearings off as easily as the lift block broke were it pushed into something immobile. That's precisely why I didn't machine these out of big blocks of steel. The mounts are my wear parts. They just need to hold the cutter head from twisting and jumping.

I was thinking more along the lines of some billet aluminum, very strong, but not "steel" strong.

 

[foggy]

My neck is really pissed at me tonight after wrestling the bushing blocks in (all 450# is offset from the center line). I've got foot spasms and hand spasms going and I finished up about 5 hours ago.

I've got a Parker 1/2" ball valve to slow my sweep with ($15 at Axman :D ), but I need a male/male nipple to install it.

Axeman surplus. Forgot about that place. Spent allot of time in that store years back when I worked for other people. :D Bought a few fascinating things there as well as a few items that I never did find a use for.

 

[dipper]

I might have missed it but I wanna see some shredded stumps!!!!!!

 

[kabic]

I might have missed it but I wanna see some shredded stumps!!!!!!

You missed it, post 109.

The stump that caused the bushing to be replaced.

 

[Jim Timber]

"Billet" is a semi-finished raw material. As soon as you cut a chunk off the raw bar you have a billet. My pivots are billet, my pins are billet, my gear box mount is billet, my cutting wheel is billet. Get the picture? Billet is a useless marketing term.

Aluminum is a bad material for the bushing blocks. It's more ductile, and has a fatigue threshold - where steel doesn't. If I were to make these in aluminum, I might as well use steel because of the wall thickness I'd need to have equal strength. Plus the weight savings isn't desireable.

Headed to town shortly, we'll be grinding this afternoon. :)

 

[foggy]

^ I'm glad you pointed out that "billet" term. Sounds good.....but it's a misnomer to me. At the aluminum extrusion plant....we used to pour melted, alloyed aluminum into 12" x 20 foot "logs"....via a vertical log water quenching method. We'd then pre-heat the logs in a furnace....and then, we'd hot shear our extrusion billets to needed lengths and extrude those billets into custom shapes of bars, angles, plates and tubes, etc. Many folks say billet....but they mean bar-stock. ;)

Got to thinking about your cylinders. Wonder is a cross-over relief valve, or some type of "pressure limiter" may pay some dividends for you.....if you have more problems. Anxious for round two. :D

 

[wiscwhip]

I guess I was thinking solid machined aluminum blocks(call them whatever you like) with pressed in bushings, as opposed to fabricated tubing where you would have to worry about wall thickness? It would be far stronger than a casting. I think with the way it is set up now, those bolts will break before the parts you fabricated, so you likely will be ok.

 

[Jim Timber]

I've got a regulator in the valve for the grinder. I may drop it down yet. 2500psi makes 24,000# push force on my swing cylinder. I'd need to go to 500# to be safe.

Those are 1/2" grade 8 bolts. ;)

 

[foggy]

I guess I was thinking solid machined aluminum blocks(call them whatever you like) with pressed in bushings, as opposed to fabricated tubing where you would have to worry about wall thickness? It would be far stronger than a casting. I think with the way it is set up now, those bolts will break before the parts you fabricated, so you likely will be ok.

Seems to me there was a comedian that used to say something along those lines: "You can call me bar-stock.....you can call me solids.....but you don't hasta call me billets." ;)

 

[wiscwhip]

Ah, no worries then. The size was very deceiving in the photos, they almost looked like 1/4" or 5/16"

 

[Jim Timber]

The outer arm is 2x6, the inner is 2.5x2.5".

 

[Jim Timber]

Well it lasted longer. :D

I did about 9 stumps and was working my way down the hill from the garden and got into digging a hole.

Turns out my mounting bracket on the pivot arm let go, then the tubing ripped off the inner mount...

The whole thing is headed home for redesign.

Worked good while it lasted!

 

[foggy]

Shoot. Too bad on the troubles. I suppose that's what new product development is all about tho. ;) Hard to hit it right....straight out of the gate.

Is this the point where I say: "I told you so".....or is it too early for that? ;) :confused:

That is one wicked looking grinder. :)

 

[rocksnstumps]

I believe the old adage is "When in doubt, make it stout"

 

[wiscwhip]

I still think some 7050 solid aluminum bar would be a good choice. I don't think a couple small pieces would break the bank either. Easy enough to drill out for the screws and bushing hole.

 

[foggy]

I still think some 7050 solid aluminum bar would be a good choice. I don't think a couple small pieces would break the bank either. Easy enough to drill out for the screws and bushing hole.

I think I'd use some billet. ;)

 

[rocksnstumps]

Just go with a chunk of 4140 steel and see where else needs a little tweaking.....

 

[wiscwhip]

Just go with a chunk of 4140 steel and see where else needs a little tweaking.....

:eek: Might not be a bad idea...or it might cause a catastrophic failure of some more expensive parts?

 

[rocksnstumps]

:eek: Might not be a bad idea...or it might cause a catastrophic failure of some more expensive parts?

Just trying to help with his R&D timeline.......wasn't talking about his wallet:confused:

 

[foggy]

The protection should NOT be the structural members of the design. Rather a relief valve or shear bolt or other means should be the weak link in the chain.