BH77 - has anyone considered converting mechanical thumb to hydraulic?

[briandantz]

Hey bumperm, check this out. Saw your mod and couldn't help myself. Almost done, just need to paint and wire.

 

[bumperm]

Brian,

Looks good!

I should tell you that after using mine for awhile, clearing brush and small saplings, where the bucket is moved sideways to bend the sapling over so the bucket and thumb can grab it, I moved the solenoid valve to the "inside" position (looking down at yours, your valve is at 3 O'Clock - I moved mine to 6 O'Clock). The solenoid itself can be loosened and rotated so the terminals are also more protected (mine are now at 12 O'Clock). Since doing this, no further bending or damage to plumbing.

You are gonna love it, the improvement over a manual thumb is nothing short of astonishing! I use my 12" bucket and thumb to pluck out large sagebrush and other large rooted brush with surgical precision and little or no collateral damage. Works great for picking up logs for sawing to manageable lengths and more.

 

[briandantz]

Hey Bumperm,
Today, I installed braided hose guard on the new hoses. Installed a selector on the side of the valve console and wired back to tractor fuse block. I added a fuse holder with blown fuse indication and fed it from the "key lock" fuse so the power is off when the key is off. disconnect at back of tractor is currently "wire nuts". need to pick up power plug tomorrow. All wiring is 16/2 SO cord neoprene jacket with braid cover where i couldn't hide it in an existing braid cover.
1) I also moved my upper "tee" down to the top of the curl cylinder like you had (pulled the pin, blocked the cylinder out, backed out the JIC/NPT 90 and replaced with a JIC/NPT/JIC tee, and reassembled).
2) Originally, I installed a street tee and JIC 90 farther upstream before the boom/dipper pivot. i had three hoses going over the pivot instead of just the two.
3) I agree on the solenoid. i have a guard in the works. already had a close call not unlike what you described.

Noticed a little leak by on the solenoid when digging (curling) real hard. Thumb gradually works its way down from the stored position. (Hydraforce does state a leak rate so i can't *****)

I will post more photos when everything is all prettied up (and painted). I did some substantial mods to the cylinder, but even with the machining and welding, I test ran this in seven hours. (pre-purchased hoses from NAPA and fittings from DHH. Cylinder and solenoid from Ebay)

Thanks for your detailed build and design tips in your post. Makes it too easy.

 

[dfkrug]

Noticed a little leak by on the solenoid when digging (curling) real hard. Thumb gradually works its way down
from the stored position. (Hydraforce does state a leak rate so i can't *****)

That's interesting. Maybe there is some debris in the valve's spool? I get no such internal leaks with more
than 100 hr of use.

DO post your final pix. There a numerous ways to mount the valve, and control it.

 

[bumperm]

In storage I do, Seems like the "normal" leakage through the spool valve. It also feels like there's a little air in the thumb cylinder that never quite get's purged out. Doesn't affect operation.

 

[briandantz]

hello guys,
came home today and the thumb was down resting on the bucket. pretty sure i left it tucked away.
couple things going on at once.

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1) got some wet fittings - re-torque and dry off

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2) picked up on the thumb with my hand and i got an inch of travel on it... got some air too. air sucks..

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3) fittings that leak fluid slightly will draw air slightly if the cylinder is being pulled on (say, with the weight of a thumb

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hanging on them for a day) air sucks ya know...

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4) known slight leak by of the hydraforce SOV

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5) maybe cylinder has a little leak by also.

So much to think about. And all of this is petty stuff because its still works freaking great and i don't have to jump off the machine and move the pin anymore.

 

[briandantz]

Hi dfkrug,

you used a couple different SOV's in the past, which one did you settle on?

here's the leakage info from Hydraforce
Internal Leakage: 82 ml/minute (5 cu. in./minute) max. at 207 bar (3000 psi) from Port 2 to 1

leak rate seems high... when you are dead heading your curl cylinder with the thumb turned off, the SOV has to block 2350 PSI. (relief valve on Kubota)

 

[dfkrug]

Hi dfkrug,

you used a couple different SOV's in the past, which one did you settle on?

The last 3 solenoid valves I have bought have been HydraForce, including
both that I have used for this application.

I will get some leakdown of the valve overnight, but no apparent leakage in
use. i.e. when the bkt is pushing against the thumb with the valve OFF.

Air in any cyl will self-purge quickly by operating them fully open and closed,
assuming all else is OK.

 

[briandantz]

when i noticed the leak by was when i was helping my neighbor remove a large stump. i was essentially stalling the curl pulling on large roots and pulling on a stump (SOV was off) . (nothing like trial by fire for a brand new mod!).
the curl circuit is so long now with two cylinders and extra hose. i have to take a few minutes and burp the rest of the air out of it.

thanks for the feedback. i will post some pics after i paint.

 

[dfkrug]

It is certainly possible to exceed the 3000psi max spec of the HydraForce SV if
the geometry of the thumb/bkt combo exerts too much force. Then, you may
see more internal leakage of the spool and unintended thumb movement.

I was careful to avoid that problem in my design.