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Old 07-26-2008, 08:47 PM   #10 (permalink)
dfkrug
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Join Date: Feb 2004
Location: NorCal
Posts: 2,406
Default Re: Custom hydraulic backhoe thumb

Thx, MJN & RED

Quote:
Originally Posted by RedDirt
1. What is a cost estimate for the solenoid-spool valve?
I quoted about $40 back in post #2, but allow me to expand: I live near
a big metro area that should have plenty of places to buy hydraulic stuff.
Other than hoses and fittings, I have had only poor experiences at retail
bricks&mortar places. Consequently, after Prince closed its direct sales
site, I have been relegated to Surplus Center and Ebay for valves and
cylinders. If I need something specific from a catalog, I can rarely get
a distributor to call me back. I keep PDF catalogs from numerous valve
suppliers (Parker, Eaton, Sterling, etc) and most carried what I needed.
After a month of waiting, I got a Hydraforce disti in Oregon to send me
a couple of their SV08-24-6T-N-12DS valves. This is a 12 volt 3000psi
4.5GPM unit with dual spade connectors.

Quote:
Originally Posted by RedDirt
2. When the thumb and bucket operate together do you have a noticeable slowing of the bucket speed compared to when the thumb is in a fixed position (and the bucket is getting the full flow of the pump)? It would seem the bucket would move at about half speed when moving the thumb (if the thumb and bucket cylinders were about the same size).
Yes, operating both cyls at once does slow down the movement of either
cylinder, but they are moving the thumb and bkt toward each other, so
the effect is not readily apparent. My hoe moves plenty fast anyway, since
my Kioti tractor delivers 8.3GPM max. I run at about 2000RPM engine
speed. I also deliberately made my welded-on fitting on the custom cylinder
somewhat restrictive. In actual use, the bkt and thumb experience different
forces when they meet a rock or dirt or whatever. The hyd fluid takes the
path of least resistance and pressure is always the same in each cylinder.
So what you see in operation is usually either the bkt or thumb moving by
itself until it touches something, then the other element moves. The orifice
restriction DOES provide some dynamic pressure differences in the cyls,
but hopefully you get the idea.
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Kubota B21 rebuild
1 cy FEL bucket
custom b/h thumb
custom b/h subframe
Diesel fuel dispenser
Bucket dentistry
custom hydraulic b/h thumb
adapting a 4-in-1 bkt to my Kioti
JD 4300 rebuild (new!)
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