Homade backhoe hydraulics question

chvojka · Jun 23, 2009

I am going to build a mini-backhoe for my john deere 110. It is a 8hp cast kohler. Is that engine big enough for my plan? also what size pump do I need to run the cylinders? And what size cylinders would work best for this set up.
The smaller diameter the better to try and keep limb weight down.

All info is good.
Joe

yankeerider · Jun 24, 2009

Sure, you can do that. Look at 11 gpm 2 stage log splitter pumps. They require only about 5 hp and develop 3000 psi. Plenty big enough for a hoe appropriate for a 110.

chvojka · Jun 24, 2009

That is exactly what I have been looking at. Good to know it will actually work.

Thanks

JoelD · Jun 25, 2009

You need about 3-5 gpm anything more and it'll be too fast to operate smoothly, look at surplus center. You'll take the volume at rpm X and convert to volume at the rpm you are looking to spin at in order to be sure you get one with big enough displacement.

Figure out the RPM you'll spin the pump at. I'm not thinking your gonna want to spin the Kholer at 3500 rpm for hours at a time.

Check out cadplans, their model 628 will be close (a little big) to what you are planning on doing.

Either way, you'll need to make small enough that the weight will not over burden your 110.

Do you have a loader? If not, you'll need to weight the front of the tractor a bunch. A backhoe is a bunch more usefull in my opinion with a loader, you may want to consider a loader first.

Joel

PILOON · Jun 25, 2009

I own a Cricket Toehoe and it sports a 5 hp and a 3GPM pump. Works just fine with that combo. Cyls are 2" and has all the power to lift the whole unit off of the ground if the bucket is jammed between rocks.
In fact I once pulled the whole stick clean off of the vertical bushing and needed to re-weld it. (factory weld was single pass mig with inadaquate penetration)

J_J · Jun 25, 2009

chvojka,

If you have 8 HP, then you can run a .3 cu in pump at 3000 psi, and put out 4 GPM's

8 HP
.3 cu in pump
3000 psi
4 GPM

Should work out quite well. Don't use two stage log splitter pump.

https://www.surpluscenter.com/sort.asp?UID=2009062506263182&catname=hydraulic&keyword=HPSR

If your engine turns counter clockwise, then you need a clockwise turn pump if connected shaft to shaft, with a coupling like this.

https://www.surpluscenter.com/sort.asp?UID=2009062506263182&catname=hydraulic&keyword=HOPM

As far as cylinders, depends on the material thickness you use for the frame and tubing. A lot of people like to go thin and cheap, but don't do it. Min of 1/4 wall square tube, 3/8 plate on frame, etc. Cylinders from 2 in to 3 in will work. 3/8 plate on the ends, and joints. Sleeves for the the rotating joints, min of 1 in pins.

yankeerider · Jun 26, 2009

JoelD and JJ make an excellent point about gpms and high speed of movement I hadn't considered. I've seen a few videos of small hoes and they all seemed to move too fast for comfort.

Were you planning to mount the pump atop the engine like the 112H models had? Or was it gonna be located elsewhere and activated by the PTO?

chvojka · Jun 26, 2009

My 110 has a horizontal shaft. The shaft comes out the right front side (when sitting on it) and has a pully on it for the mower deck. I can pull off the pully and have plenty of room to mount a pump direct drive. It runs CCW so I'll have to Get a CCW pump.

J_J · Jun 26, 2009

No, you need a cw turning pump. All motors ,pump, etc rotation is by looking at the shaft end. So if you want the pump to turn correctly, hooked up directly, with a Lovejoy connection, and pump mount. Pump should be cw rotation.If hooked up correctly, the engine will be turning ccw, and the pump will be turning cw. Remember looking mat the shaft end.

You can run a pump any direction if you mount it for the intended purpose, using pulley arrangement, facing the pump, off set, or side by side. Take a pen and draw it out and I think you will see. I posted the same thing in post #6 above.

https://www.surpluscenter.com/item.asp?UID=2009062614150202&item=9-7146-B&catname=hydraulic

This pump has a straight shaft.