On Mon, 24 Jan 2005 19:08:07 -0800, Larry Jaques
wrote:

On Mon, 24 Jan 2005 15:36:42 -0500, the inscrutable "Shawn"
shawn_75ATcomcastDOTnet spake:


"Eric R Snow" wrote in message
. ..
I need to make a thumb for the 580CK Case tractor backhoe.
The bucket on the front of the machine will keep the same angle as it
is raised and lowered. So, for example, if the operator tilts the
bucket to a ten degree angle with one lever it will keep that angle as
the bucket is raised or lowered with the other lever. I want to plumb
the thumb to work the same way. It appears to me that it may be
valving that makes the front bucket behave this way. Anybody know how
this is done?
Thanks,
Eric R Snow

If this is the machine I am thinking of, there is a level compensating slave
cylinder on the right side of the machine. This adds or subtracts fluid
from the bucket tilt cylinder as appropriate. The hoses to this cylinder
don't go back to the valve body, just across the bucket tilt lines. It is a
fairly common method to accomplish this action.

You mean the bucket/thumb stay the same in relation to the ground,
rather than the arm, during the raising/lowering/extension/retraction?
That'd be cool, expensive, and a bitch to fix.
On the front of the tractor the bucket keeps it's angle the same in
relation to the ground. What I want is for the thumb to follow the
backhoe bucket. So when it grabs something the bucket can be curled
without either dropping the load or being prevented from curling
further. One way I thought of is to use an accumulator connected to
the thumb that is pressurised less than the pressure that the bucket
cylinders. That way the bucket could put pressure against the thumb.
The accumulator would just fill with oil as the bucket curled against
the thumb. But that idea seems expenzive and inelegant. There has to
be a better way. Maybe Northern can tell me how to do what I want.
ERS