Hydraulic Winch Circuit design

[Tentman]

Hello Folks

I'm wondering why we don't see many post drivers/knocker/bangers with a hydraulic motor to raise the hammer, the two main systems I see are the long stroke hydraulic ram coupled to a dumb purchase at 4-6:1 and the "nodding donkey" where a short stroke ram drives an arm with a 1:2 dump purchase.

I'd like to drive the "winch" which raises the hammer with a hydraulic motor - the hammer is about 350 lbs/160kgs.

How would one design a circuit that:

- winds in but doesn't self destruct if the operator over-winds (some sort of relief ??)

- holds at any point (and doesn't self destruct if the operator attempts to stop the hammer while its falling - another relief?)

- free spools with minimal drag.

If anyone can suggest the hydraulic components to build such a circuit (assuming its possible) I'd be very grateful.

Thanks
Foster

PS Go easy on me if its an obvious answer, hydraulics are something of a mystery to me so I need to job everything out!!

 

[ozzie tractor]

the free spool with minimal drag is a bit tricky. a hydraulic motor being spun by a falling weight turns into a very effective pump. now pumps need oil or they die really quickly so the only real option is to when dropping, dump the exhaust oil back to the intake on the motor. this part of the circuit needs to have big flow capabilities. work out how fast your hammer will drop and how fast the motor would turn from that. then multiply that rpm by the capacity of the motor and you will see how much oil flow you will get. even set up like this, you will have some drag because your moving oil so it naturally has some resistance. the test of it is simple. main relief on the lift and a in circuit (port) relief on the lower. you can get valves with both of these built in.

 

[dfkrug]

I agree with OZZIE: your system RV and a work-port RV with meet your 2 top needs. You will have
to use a spool valve not intended for motors, since that kind will open work port to the tank when
the lever is in neutral. A simple tandem-center spool valve will work. It is OK not to use a
motor valve (open-center) if you are not turning a high-mass object and/or have work-port RVs.

As for free-wheeling, the only practical way to have that feature is to use a mechanical disconnect
from the motor. That's how a conventional electric winch works. You can use a dog-type clutch.
IMO, of course.