Hydrostatic drive on articulating loader

[robirot]

Hi

I‘m planning on building an articulated loader myself (from scratch).

I want it to have 4wd hydrostatic drive.

So my first thought was to just take a pipe, put a gear onto it, thread it though 2-4 ball bearings and drive it using a hydraulic engine via a chain.
Should be quite easy to build, but would mean that it would have 2 permanent locked axles, which shouldn’t be to much of a problem, since it is meant mainly for off-road use, but once you are on concrete, it would be a dumb idea or put a lot of stress on the axle and rubber on the ground.

So the next idea was to go the CadTrak route, 4 drive motors. Could go the same way as above, but use 4 short axles or the CadTrack way with the engine mounted straight onto the wheel/axle, which sound quite interesting and would solve a couple other problems.

I don’t have the CadTrack plans, so can maybe someone tell me how it is done there, or if my plan would work.
Atm I thought about making the drive train like that:
On one side mount a wheel hub to the axle, thread it through 2 Ballbearings (welded to the frame, to take up the weight and to guide the axle) and mount the hydraulic engine with a keyway to the other side, to drive the axle.

Any major flaws in the design (or maybe non unederstandable what i mean and i should make a drawing)?

 

[ptsg]

From my understanding of your post, you're basically avoiding getting two diffs and have a solid axle with the hydraulic motor powering it directly. In my opinion, don't skip the differentials, specially on an articulated loader. I tried to skip the diffs on my homemade backhoe, and quickly found out how much of a flop it was. Had to redesign most of the drivetrain part of it.

Definitely go with a diff on the front and another at the back. Something with a limited slip diff or a lockable diff would be great too. Or go with 4 hydraulic motors, one per wheel.

There are thousands of videos of homemade loaders on YouTube, mostly Russian ones, but you can get an idea of how they build those.

Here is a good one, where you can see how they built the drivetrain:

 

[4570Man]

Most commercial loaders will have a transmission more similar to an automatic vehicle transmission except it doesn’t automatically shift vs a HST transmission.

 

[robirot]

Well, expected that with the fixed axle.

Then it propably will be a 4 hydraulic motors setup, getting the axles will be harder and expensive and also it saves the problems with the drive shaft at the articulating joint.

So 4 half axles and direct driven using a keyway coupling or better gears and chains?

Since the loader needs to be able to handle ~3000 lbs (on a mast), what would be a good diameter for the axle, 70 mm solid?

 

[MossRoad]

If you go with 1 hydraulic motor at each corner, there's a few things you might not know.

I think all units with a wheel motor at each corner is articulated.

1 pump with 4 motors works great. I have this exact setup on my PowerTrac. However, there is no range selector. The gearing is a compromise based on the output of the variable volume pump and the displacement of the wheel motors. Larger displacement will give more power with less top end speed. Smaller displacement will give more top end speed with less power. Mine goes 0-8mph, which is great for yard work, mowing, FEL use, etc... however, it's too slow to take on the road any distance, and it's not powerful enough to pull stumps, a plow in the dirt, several rippers in soil, so consider that.

They make variable speed pumps with high and lo ranges, but my guess is they will start getting pricey.

Then you have to decide how you want to hook up the wheel motors to the pump. If you put them all in series, you won't be able to turn because hydraulic motors in series prevent the other one's in the line from going different speeds.

If you put them all in parallel, if one spins, you're probably stuck.

Again, referring to my unit as reference, the left front and right rear are one circuit in series. The right front and left rear are another circuit in series. Then those two circuits are connected in parallel to each other. If the left front spins, the right rear will stop it from spinning. If both left tires spin, both right tires will stop them from spinning. As long as the opposite corner tires have different traction, you'll never get stuck.

With this setup, when sitting still, and you turn the steering wheel to the left, the left front and rear tires roll TOWARDS each other while the right front and rear tires roll AWAY from each other. Think about that. It's necessary in an articulated machine. Anytime you turn, the left front and right rear are rolling at the same speed and direction while the right front and left rear are rolling at a different speed in their same direction.

If you want to use differentials on front and back, you could drive them each with a hydraulic motor and skip the driveshafts.

Or you could connect the differentials with driveshafts and drive a transmission with a hydraulic pump to get ranges.

All kinds of stuff.

 

[robirot]

Speed is not a problem, 8 mph is fine, 15 would be max. After all it stays an forklift/loader not an road vehicle.

Yes doing two diagonal circuts is a good idea, As of now k thought about a 4 pump setup, with all driven individual, but hoses between the circuts, to switch from individual drive to all driven parallel (basically a hydraulic version of a diff lock).

Also found this video:

wich would be easy to construct, but actually it is quite hard to find the parts to connect the keyway to wheel (in that vid @2:44) propably i just miss the propper name for it. looks like an quite easy way to build this.

Edit: it is wheel flange

 

[Patrick Herd]

If you go for 4x hydraulic motors there's a couple of funky things that can be done depending on how much you want to spend on valving and plumbing:
For motors in parallel you can use flow dividers to get around loss of traction issues Flow Dividers OT200 | Brevini Fluid Power

https://www.mobilehydraulictips.com/what-is-a-flow-divider/

The other one I would consider is setting up valving such that you can switch the motors from 4x in series, to 2x series sets of 2x parallel, and or 4x in parallel. Crude way of achieving four speeds from the same pump and drive motor RPM.

 

[4570Man]

You could just buy a used loader for cheaper than what it would cost you to build anything half way decent.

 

[robirot]

Well a used loader in a comparable cost class, would run at about 10k$ and propably be 20 years old and beat up from farm work. A younger one i. good condition will be about 25k$. Also where would be the fun in that anyway?

 

[4570Man]

Well a used loader in a comparable cost class, would run at about 10k$ and propably be 20 years old and beat up from farm work. A younger one i. good condition will be about 25k$. Also where would be the fun in that anyway?

I’m not trying to be a Debbie downer but what do you think can be built for less than $10k? Just buying tires and wheels will use half the budget. And if you buy a 10-20k loader you’ve still got a 10-20k loader. A homemade machine won’t hold much value. If you want to build a loader for a hobby that’s one thing but if you think you can build something better for less money than you’ve got something else coming.