Hydrostatic Drive Design

larkinja

Ok, I'll see what I can find. Thanks!

larkinja

Is there a way do do this with fluid? Maybe a a valve that allows the fluid to free flow through the motor? I haven't had to much luck finding any application that would use something like a free sprinning joint. At least something that is strong enough to handle the torque and abuse. I'll still keep looking though.

Let me know if it is possible.

Jason

RonL

You will need to make one or two changes maybe, but look at the inside of an automatic transmission torque converter, the stator clutch is a slip design that freewheels in one direction and locks up in the other direction, they transfer a lot of torque.

Ron

larkinja

That's a good idea. I can check into that and see if there is a way to make it work. I think I have an extra one laying around.

drankin

Ok, here is a rudimentary schematic that we can begin to build on. It just shows the hydrostatic pump unit and drive motors in parallel. That will change as we add flow dividers and the rear wheel drive "hi-speed" mode.

It's been a few years since I've worked on hydrostats but I know we can oversize the make-up pump that's attached to the main pump to accomodate pilot operated controls for footpedals and joysticks as well as auxillary hyraulics for a winch or some other function we might come up with.

Attached Files

BUGGY HYDRAULICS 17JAN10.pdf (12.0 KB, 87 views)

larkinja

Excellent. I do have a question. We have been talking about a free-wheeling design, but how do we do reverse then?

I took a look at the schematic. I will have to go and find a chart to understand the symbols, but I have a pretty good idea of the concept.

larkinja

How hard would it be to design it around a free flowing neutral instead of a mechanical free spinning idea? I think I figured out a way it may work, but it will be kind of bulky. It seems like reverse would be easier then, but I could be wrong.

drankin

Ideally, we would be able to free-wheel if a wheel began to spin due to turning or just flow discrepencies. Then we could switch off free-wheel in order to lock all drive motors to the wheels for reverse function. If we can't do this I'll have to add more hydraulic circuitry to protect the motors. Not a big deal, it would just be better for long term wear on the motors.

larkinja

I think there are going to be difficulties doing it mechanically. The torque converter idea is good, but the rpm difference may pose an issue. The speed at which it "locks" may never be reached as the rpm of the shaft coming off the motor is lower than what a torque converter is designed for.

drankin

There are low-speed-high-torgue (LSHT) rotary piston motors that have a free-wheel function available, but they are much more expensive (x10 probably) than the gear motors you wanted to use. We'll just go with hydraulic free-wheel.

larkinja

OK, sounds good. What else do you need from me?

drankin

About $3500 as a retainer. :) j/k

Just patience. I don't have a lot of time to put into this but I'll be adding to it every day to every other day or so.

You should be looking at mounting the motor and making sure we have room behind it for the shaft couplings, bell housing, and hydrostat pump.

Do you have a picture of the frame you can put up?

larkinja

:) Gotcha. No Problem. At this point I am just need to figure out what size pump, motors, etc.. and like you said figure out how much space I am going to need.

I'm not sure if I have any current pictures, but I will be out there working on it Thursday, and I will get some and put them up.

And again, I REALLY appreciate everything. Any don't worry, I will be patient.

I'm not sure what I can do in return. I own a sign company, so if you ever need any signs, decals, banners, etc... let me know.

Again, thanks.

turbo

I just read through this thread. Wish you had posted a few months back because an old friend of mine that died recently built an all-hydrostatic drive vehicle about 30 years ago. It was a tube-framed buggy with big wheels and all-wheel drive. He made it so that he could go fly-fishing in places that normally you'd have to walk to, wade through mud, ford streams, etc. Clever guy. He made custom gold jewelry using the lost-wax method, crafted some of the nicest hunting knives I've ever handled, and retrofitted Winchester lever-action carbines and rifles to shoot common handgun ammunition. It would have been a good excuse to get back in touch with the old genius and see what problems he ran into when making his buggy.

larkinja

Sounds like quite a guy!

turbo

Very smart. He was about the first guy around to learn the ins and outs of VHF antenna sensitivity and directionality, and apply it in this very hilly rural area to help people get TV back in the '50s. He had a very successful TV antenna business when I was a kid, and he kept enough stock on hand to demonstrate on-site what they could expect with antenna A vs antenna B or C. Hell of a businessman.

His buggy was not fast IIR, but it could get him into places that Jeeps could not go, and he had a hydrostatic-drive winch to haul himself out if he got mired. The buggy was a two-seater with an over-head pipe rack to carry a canoe. He and his son had good times with that, I'm sure.

He was a very clever and artistic guy. One time when I dropped in he was carving a red wax positive model of a ring for a very prominent man in town. The guy's daughter had commissioned the ring to reflect her father's activities in the Masons, the Shriners, the Rotary, Lions Club, and other social organizations. I never saw the finished project, but it must have brought a smile to the old guy's face when he got it. The mold looked a bit busy, but well-organized. Val's work was top-notch.

larkinja

Wow, that is very cool. You just don't meet people like that very often. I imagine for him, similar to me, its not about having the buggy, its about building it. There is something very satisfying about building something with you own hands, and the challenges it poses that makes it fun. Especially when it is something some people say can't or shouldn't be done. For me its also about learning new things. Short of the hydraulics on my plow truck, and a couple repairs on a bobcat, I don't know that much about hydraulics, so something challenging like this is a reward in itself. There are many things on my list to build, and each time I do one, I gain more knowledge and experience. My son is 6, and he is now starting to take interest in these projects, and I hope it evolves into a father/son activity that can last a lifetime and make memories. I remember one of my best friends in school did things like this with his father, and I remember thinking that I wish I had something like that with my Dad.