Hydrostatic ATV

[kdlklm]

Gotcha.

Keep in mind though that even 15 mph is going to be stretching it. In that Power Trac clip, they made it clear that they had no "attachments" available for it....such as a blade mount/three point/etc. Sounds (to me) like they made all the compromises they could in order for it to attain an "ATV-competitive" top speed, (and 14-16 mph isn't really competitive anyway), and sort of abandoned the notion that it's suitable for real work.

On another forum I frequent, one of the topics frequently discussed are issues with lawn and garden tractors. Breakdowns and lack of reliability are common discussions. The overwhelming majority of "issues" are experienced by the operators that are continuously asking too much of the machines. A good rule of thumb, is to consider what attachments the tractor manufacturer offers for a particular model. Lots of these guys buy a tractor and then build their own trailer, (that's too big), to pull around behind it, or they hook up to a large spike aerator, (and then add a bunch of weight to the tractor for traction), and try to drag it around. They can go right to the manufacturer's website or sales brochure and see that all that's listed for accessories for their model is a light-duty yard cart, and somehow that doesn't register.

In Power Trac's situation, I think the fact that they don't offer attachments is very telling. It certainly "looks like" it could be a real workhorse, but....

I definitely see your point, but I am looking at 10 to 15 hp more. Which should give me more torque at speeds of 15 mph, I also plan on having a high and low range. It's just a matter of figuring out which pumps and motors to accomplish what I want.

 

[kdlklm]

Search for the Ventrac series 300 they have done something also like you want.

that is the first time I've ever seen that machine, I like it. But it doesn't meet my needs. It's only rated for 400 pounds, which a power chair user is in the 600 pound range. And I also need to be able to use a joystick to drive. I don't think I'd want the motor in front of me like that. But it looks good.

 

[kdlklm]

I'm looking for some input on opinions about what would be the best articulating joint. I wanted to be able to go left and right but also be able to rotate. It needs to be as compact as possible and relatively maintenance free. There's many ways that it can be done but what do you think is the best.

 

[Iplayfarmer]

I'm looking for some input on opinions about what would be the best articulating joint. I wanted to be able to go left and right but also be able to rotate. It needs to be as compact as possible and relatively maintenance free. There's many ways that it can be done but what do you think is the best.

A simple U-joint would work if you were okay with up and down movement as well. You could do something as simple as a trailer ball and hitch.

If you want to exclude up and down movement, it complicates things; but only a bit.

 

[David Devuono]

You need to look at how the transfercase\transmission in a Unimog attaches to the front and rear axle. That joint (similiar to a Birfield Joint in Solid Axle Toyota and Suzuki Samurai. If it was not for the Panhard Rod on a Unimog Axle, it would move sideways as well as up and down. This joint is the only thing supporting fore and aft movement on the Unimog axles and contains the single U-Joint. Unlike normal vehicles that have two U-joints on a drive shaft. Anyway in this picture I am holding the outer socket that bolts to the transmission front output shaft, and you can see the ball that is part of the torque tube that locates the front axle. Lots of jeepers are trashing Unimogs just for the front portal axles and you might be surprised to find a cheap front torque tube in the USA. It I was you, I would take the easy route and just build a strong Joint for Left and Right steering and then Pivot the front axle like a farm tractor. That way you have steering and some articulation?

 

[evo803]

This is what I did to solve the problem. I have hydro axles that are belt driven so the centerline of pivoting had to incorporate a jackshaft for the drive belts. You need to be precise or else the belt length will change to much for a tensioner to compensate for when turning and twisting. My links were made from cat 1 toplinks.

 

[kdlklm]

here is a blueprint of what I've been working on. The unique circumstance this machine s that it can't have a front axle, because the front-end needs to be able to lower down. The machine is for a wheelchair user. I've got a close-up of the articulating joint, I'm not quite finished yet, I need to add something so that it can only rotate a certain amount. It goes left and right and allows the joint to rotate in the center.

 

[kdlklm]

I added a overhang plate, to allow the hitch the only rotate a certain amount. This should prevent it from rotating too much when turning on uneven ground. I plan on using 1.75 inch shaft pins so it should be plenty strong enough. It will take quite a lot of weight, a person in a power wheelchair is anywhere from 500 to 600 pounds. the steel plate is all quarter inch. And all the bearings are very heavy duty and large. The hydraulic ram mounts have to be added yet for the articulating steering. But I have to sort out the hydraulics yet.

 

[evo803]

Depending on weight distribution over the axles and the balance point will decide how much added stress will be on that center joint. There will be a significant amount of force and the front piece of that articulation joint that is u-shaped looks vulnerable. I would bend this out of 1/2" plate IMHO.

To limit rotation I would incorporate stops onto the rear portion of the pivot so it stops the u-shaped piece from rotating more than 10-15 degrees.

Could you post some more design photos?

 

[kdlklm]

those are good suggestions, and I incorporated it into the new photos. I added bolts to the top to make the rotation adjustable. I also beefed up some of the steel. Let me know what you think.