# Hydraulic questions

• posted

A friend of mine owns a company that installs re-bar for concrete pours. He has acquired two machines called re-bar benders that also have a shear on them. The one machine is missing a hyd. pump, and the other machine, the pump has no numbers on it anywhere. They look to be homemade. How can we tell what pump and valve body to use, he wants to buy two new pumps and valve bodies. The pump is fairly small, two bolt

3/4" shaft, I think the inlet is 1" and the outlet is 1/2", looks like the center of the pump is alum. and the ends look like cast iron. There are two cyl. on this machine, one for the bending one for the shear. Any help would be great. Thank you, Craig
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Well, work out the volume needed to move the cylinders from one end to anohter. Now, work out the needed force, and the cylinders area, to get pressure. Now, you have pressure, and flow, all you need to specify a pump.

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Grainger's catalog has a tutorial on basic hydraulic design.

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I can figure out the area of the cylinders, how do I know (or, where do I find out) how much force is needed to shear 1" rebar, and to bend it? Would The Machinists Handbook have this? One machine has a 10HP B&S motor, the other has a electric motor,

1750RPM. The bending cyl. is about (working from memory, didnt measure) 24"stroke with a piston dia. of maybe 1.5", the shear cyl. is about 12" stroke & 2" or more dia. This may be what ever was available. I have not seen the thing work. The resivoir is somewhere around 8,10 gals, give or take. I dont know the cycle time of shear, or to bend 90 deg. Thanks for your help, Craig
• posted

On 04 Apr 2005 18:02:15 GMT, Ian Stirling wrote something ......and in reply I say!:

Not quite. You need to know hoe _lomg_ it should take for the cylinder to run full course. Volume only gives you a reservoir size.

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