Custom UTV

[aczlan]

Not sure what to think about that suspension. Very unusual. Can you please explain it's purpose? I'm assuming you are using it to adjust ride height?

The object (per earlier parts of the thread) is to make a "box" on the front where he can drive a wheelchair into and run the machine from there so as to access areas where a powered wheelchair cannot go.

The suspension will allow the front to "kneel" and make a gently sloping ramp to drive the wheelchair into.

Aaron Z

 

[aczlan]

I've come up with an idea for a suspension system, for my machine's front-end. It's a little crude yet, but I'm looking for little bit of feedback before I refine it more. I've attached a few photos, and also did a video animation of how it works. Let me know what you think.

I see 4 possible issues:
1. When you hit a bump, will the arm drop enough to bottom out? How about when you have it "kneeling" will it hit the ground?
2. Will the shock/lift assembly bend when you hit rough terrain?
3. How big are the rods on your lift cylinders? Will they bend at full extension?
4. Could you run the hydraulic lines in a different fashion? If you snag the lower line for the lift cylinder on a branch and break it off, you will be stuck.

IMO, you would have a simpler design with the ram and the shock(s) on the same side of the pivot as the tire.
Perhaps something like this:


If you are going to be very far off of the pavement by yourself, I might also add a backup electric actuator on each side to lift the front up in case you blow a line somewhere. Below is one way that it could be done. No suspension, but it would get you back without needing to wait for help:


Aaron Z

 

[whodat90]

How about instead of trying to get the suspension to do all the work, use a center section similar to a drop-bed trailer?
http://www.practicalmachinist.com/v...er-rental-san-fernando-valley-ca-img_9883.jpg

 

[kdlklm]

How about instead of trying to get the suspension to do all the work, use a center section similar to a drop-bed trailer?
http://www.practicalmachinist.com/v...er-rental-san-fernando-valley-ca-img_9883.jpg

that was one of my original designs, to use the lowering floor instead of a kneeling system. The more I think about it, the more I am inclined to go back to that design. the only problem I have with that is the shaft that supports the motor mount.

 

[PapaPerk]

The object (per earlier parts of the thread) is to make a "box" on the front where he can drive a wheelchair into and run the machine from there so as to access areas where a powered wheelchair cannot go.

The suspension will allow the front to "kneel" and make a gently sloping ramp to drive the wheelchair into.

Aaron Z

Ahhh I see. :thumbsup:

Here's my thoughts.... I would use a Firestone airbag and small shock absorber. That would be simpler and more durable.

If I was designing such a rig, I would make the front of the unit a fold down ramp that the operator could simply drive or push the wheel chair up. Then the ramp would flip back up. Similar to a WWII infantry landing craft.

Of course these are just my opinions! :thumbsup:

 

[PapaPerk]

Another option is to use the ramp idea coupled with tilting the bed (where wheel chair sits). This will provide a smooth transition and would be easy to implement with one hydro cylinder. :thumbsup:

 

[whodat90]

Since you're using hydro motors, you can just put them wherever it's convenient and chain drive down to the drive wheels. Imagine the trailer I posted, but it's back is your front. Motors go on it's front, chain drive down to the wheels. Alternately, since they're hydro, there's no particular reason you couldn't hang them above the wheels facing out, and chain drive down, unless they're way too long.

Another option is to simply go with the ramp idea, but have a grabber in the UTV that reaches out and pulls the chair inside. Then, so long as you don't fall out the angle is somewhat irrelevant. Think of a flatbed tow truck and it's winch.

 

[kdlklm]

here are a few updated photos of where things are at now. I'm looking at going with an air ride suspension that also will work as a kneeling system. I spoke with Ride Tech and they told me that their system would work perfectly for this. So we are looking at using 7000 series shock absorber with a 6.9 inch stroke. Air ride is a little pricey, but it will kill two birds with one stone. And from everything I've researched it's very reliable and should last me a long time. Let me know what you think of this.

 

[PapaPerk]

here are a few updated photos of where things are at now. I'm looking at going with an air ride suspension that also will work as a kneeling system. I spoke with Ride Tech and they told me that their system would work perfectly for this. So we are looking at using 7000 series shock absorber with a 6.9 inch stroke. Air ride is a little pricey, but it will kill two birds with one stone. And from everything I've researched it's very reliable and should last me a long time. Let me know what you think of this.

Can you post a bottom view? Curious how the swing arms are attached to chassis.

 

[kdlklm]

right now, I just have them attached to the back. I'm not sure that's going to be my final design yet.

 

[aczlan]

Looks great.

Aaron Z

 

[PapaPerk]

right now, I just have them attached to the back. I'm not sure that's going to be my final design yet.

Thanks for the pic. I see you have a pivot at the rear. What support the wheels from moving outward? Is there another link I'm missing somewhere?

 

[kdlklm]

I haven't come up with the design yet they keep the wheels from going in and out. But I am open for suggestions.

 

[PapaPerk]

I've attached a sketch I found on Google of what I would use. This a swing arm concept from a motorcycle. The key is how it attaches to securely support the wheels. You would not use the drive shaft system.

With this design you could run a frame member from one side of the vehicle to other to secure the swing arms. This would make a very rugged suspension. Attaching the suspension just to the side will not be strong enough.

Of course just my opinions! :thumbsup:

 

[PapaPerk]

This robot from Carnegie Mellon has a similar suspension... worth checking out. Lots of videos on YouTube, etc. Here's link with a short clip, pics and description.

Carnegie Mellon's National Robotics Engineering Center Unveils Futuristic Unmanned Ground Combat Vehicles

 

[PapaPerk]

Watch this video too. This is a small version. At the end they take off the swing arm for service. Good detail shot.

Mini Crusher Video

 

[kdlklm]

That is really cool, if I only had their budget. It appears that the Mini Crusher doesn't use any kind of swing arm. It just puts a suspension really tight to the tire. The air suspension that I'm going to use will require close to 5 inches of space. So it doesn't really give me much choice but to put the shock either in front or behind the wheel. The machine is getting wider than what I like already. If I move the wheels out another 4 inches, it will be too wide.

I'm just trying to get my head around that swing arm system. How I could attached to what I've got. I'm not quite sure what you mean when you say that I could go from one side to the other. Where would you suggest I put it.

 

[westcliffe01]

I think you need a pair of panhard rods that run perpendicular to the axis of the vehicle to stabilize the long swing arms. The Panhard rod for left hand side swing arm attaches on RHS of chassis and the one for the RHS radius arm attaches on the LHS of the chassis. If you do it right, the rods would be horizontal at nominal weight so that any lateral deflection is spread out evenly.

A vehicle with a rigid rear axle only needs one, but you have independent suspension so to keep it working best you need 2. It also means that there has to be some compliance at the pivot position for the radius arm, otherwise that end of it would be subject to huge stresses. Usually using 2 flanged PU bushings works for that.

panhard bar

 

[BHD]

just a thought may not work and then again it may,

just use the cylinder, and put next to the cylinder an accumulator,
If you let fluid out of the cylinder circuit you lower, if you add you raise and the accumulator is charged such that it will act as a spring,

And all the accumulator need to be is a Hydraulic type cylinder, with a moving piston to separate the nitrogen charge from the fluid, if one wanted to one could add a spring in the accumulator and not depend on the nitrogen charge entirely,

you would need a flow divider or separate circuits on each wheel or you my have balance issues,

but with the system one could level the unit for the wheel chair rider, if the ground is sloped as well, and if separate circuits it could be leveled side to side some what like a hill side combine is,

~~~~~~~~~~~~~
the other Idea is just a put a leaf type spring on the arm for the spring and use the cylinder to raise and lower,
~~~~~~~~~~~~~

My sister had a handicap van that would kneel for the wheel chair ram, and all it was a cable on the axle and a electric driven kneel actuator unit that would pull on the cable/chain and compress the spring on that rear of the van, and just compress the spring, and then one would release it and it would raise up and the cable just floated as the suspension worked, (It malfunctioned when she was visiting me one time and to get her home I had to disconnect the cable),

 

[kdlklm]

I think you need a pair of panhard rods that run perpendicular to the axis of the vehicle to stabilize the long swing arms. The Panhard rod for left hand side swing arm attaches on RHS of chassis and the one for the RHS radius arm attaches on the LHS of the chassis. If you do it right, the rods would be horizontal at nominal weight so that any lateral deflection is spread out evenly.

A vehicle with a rigid rear axle only needs one, but you have independent suspension so to keep it working best you need 2. It also means that there has to be some compliance at the pivot position for the radius arm, otherwise that end of it would be subject to huge stresses. Usually using 2 flanged PU bushings works for that.

panhard bar

would that not affect my ground clearance, I want to keep the middle as open as possible. One thing I have looked at is a single-sided swing arm that are used on motorcycles. I could build something like that.