Building a homemade Skid Steer need help with some of the hydraulic problems

[thayn69]

I am building a home made mini skid steer and it is nearly complete but i am having problems with the drive system. I am running a pump from surplus center part number is 9-7686 and i am attempting to use motors that are scavenged but i have 2 that match their part number's are Te0065fp130aaaa I am running 17.25" diamater tires and have a gear reduction of 2:1 in the chain drive. the engine is a 20 horse Kawasaki and i have a 20 Gal reservoir. The pump is driven on a 5/8" belt but the pump is turning 1800 rpm it is supposed to operate from 600-3600 rpm. when the skid steer is in the air the tires spin about 150 rpm. any info is greatly appreciated.


(Surplus Center)Pump 0.43 cu in HYDROSTATIC KANZAKI DUP-7A TANDEM PUMP
(google link not sure what page to use) https://www.google.com/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=Te0065fp130aaaa

 

[MossRoad]

First, welcome to TBN! :thumbsup:

Second, what problems are you having with the drive system. You've described the drive system, but you don't specifically state what the problems are.

Your engine is turning a pump.
The pump turns motors.
The motors turn chains.
The chains turn wheels.
The wheels are turning....
So what's the problem?

 

[Arc weld]

I think you'll have problems with belt drive hydro pumps. There's a bunch of engineering that goes into designing a hydrostatic drive.

 

[MossRoad]

I think you'll have problems with belt drive hydro pumps. There's a bunch of engineering that goes into designing a hydrostatic drive.

Then Bobcat made a huge mistake when they switched to belt driven hydraulic pumps 20 years ago....

 

[MossRoad]

Here's a link touting belt driven hydraulics as superior....
Serviceability

 

[Stonehaller]

Since you do not really state what your problem is, I will just ramble a little about your configuration to see if I can pass on anything to help you.

Your pump is rated 0.43 cu. in. per rev max. The hydraulic motor looks to about 4 cu. in per rev, so max hydraulic motor RPM is about 1800 * 0.43 / 4 = 194 RPM. If your wheels are turning 150 RPM with 2:1 reduction, then the motors must be spinning 300 RPM. Could be the motors are actually less than 4 cu in per rev or you are running faster than 1800 RPM or a combination of both.

With 17.25 diameter tires at 150 RPM, that is about 7.7 miles per hour. Depending on how small your skid steer is, you may not want to go any faster.

Your 20 HP engine is probably rated 20 HP at 3600 RPM. At 1800 RPM it probably has just under 10 HP. Your motors are probably only rated 2000 psi and you should have cross over reliefs for each motor to protect them. 2000 psi at 6 GPM is about 7 HP so you should have plenty of power to run the motors at their rated load which depending on the size of your skid steer may or may not be enough power to the wheels adequately.

You will need another pump for implement hydraulics. If you feel you are going to be marginal on power, run your engine faster and use a lower ratio to drive the wheels.