Need Help

[Greg_Phillips]

I am working on drawing up plans for a miniture Cat tracked tractor. I am planing on using two hydro motors, one on either side to drive the track on that side. I would really like to turn this thing with a steering wheel, and I think I have figured out part of it but I need some help with the rest. I think I will end up using a steering wheel attached to some type of bell crank with rods on either side going back to the control ports on the motors, so that when the wheel is turned one way the rod on that side would push back, slowing that track down, while the rod on the other side would pull foward, speeding that track up. This would cause the machine to turn in the direction the steering wheel was turned.

Where I am having trouble is how can I set the system up so the drive direction/speed lever and the steering system can both have access to the motors?

Anyone got any idea?

Thanks

 

[diyDave]

Why not set up 2 standard valves/levers, then attach a wheel linkage, which will control turning and track counter-rotation, and set it up so the farther forward you push the steering wheel, the faster you go, or pull it back to slow down or reverse-kinda like a pilot's control yoke. Look up C.F. Struck co on google- they make small crawlers, but they just use 2 levers, on standard valve banks.

 

[kennyd]

Just my opinion here, But I think you are trying to re-invent the wheel so to speek, levers have been used to operate tracked equipment for nearly 100 years now. If there was a effective way to use a steering wheel, you would see it in the marketplace.

 

[Soundguy]

I agree with Kenny... lever's on bdz's is pretty standard... you could joystick it.. but that gets intricate.

Your steering wheel option would not give you reverse without some very fance diverter valving taking place..

Soundguy

 

[SnowRidge]

You haven't said what kind of pump(s) you are going to use to drive this thing. If you are going to use variable volume pumps, then you could use a wheel on a sliding yoke, somewhat like an aircraft. Pushing the the wheel forward would increase the ground speed, while pulling it back would decrease it. Pull it back from center rest would put it in reverse.

Turning the wheel clockwise would bias the mechanism in favor of forward motion for the left track and and rearward or slower forward motion for the right track, depending on the position of the sliding yoke. Turning the wheel counterclockwise would would do the opposite.

With the yoke at its fore and aft center, turning the wheel would cause the tracks to be driven in different directions.

With the wheel/yoke both centered, the machine would be stationary. For safety, everything would have to be spring loaded to the center position

You would have to engineer a somewhat complicate sliding mechanism to accomplish all this. The mechanism would be connected via links to the swash plates of the two variable volume pumps.

I have no doubt that this could be made to work. I have considerable doubt that it would be worth the effort. Two levers linked to the swash plates would be oh so much simpler. Using fixed volume pumps and lever connected valves would be simpler still.

 

[diyDave]

KennyD- there was a tracked tractor that had a steering wheel. It was back in the early thirties Monarch tractors had them, and when Allis Chalmers bought them, they used the same system for a few years, it just never caught on. I think the wheel controlled steering, and brakes came on when you turned the wheel harder. Someone will correct me if I am wrong on this, but its interesting history.

 

[Wayne County Hose]

You could do it with an orbitrol valve feeding the motors. I would seek the input of someone who really knows hydraulics. I could probably figure it out with some research and time, but that would make my brain hurt.

 

[6sunset6]

Not thast I have the answer but I have an observation. Have you seen those fork lifts that are piggy backed on the back of delivery trucks for pallatized delieveries? I drove one for a while once. They are all Hydraulic and have a steering wheel left and right turns the back wheel and push foward and pull back on the wheek for go foward or back. Then there is a joy stick for the fork lift . I think no brake pedal just center the steering wheel but I don't remember that . I think someone told me it was spun off aircraft something. Maybe you can find a valve at the Surplus place.

 

[AndyinIowa]

What you are wanting to do is referred to as 'differential steering'. Caterpillar Challenger tractors (ag tractors) use a steering wheel to control differential flow for steering.

Its not easy to tune at all. The neutral return mechanism and tolerances in the system, plus design criteria (do you want the steering wheel to provide 100% counter-rotate, or only 40% differential steer?) really will bog down the project.

Good luck! I'm not trying to discourage - only to make sure you know what kind of project you are tackling...


AndyinIowa