Easy OmniTrack
 

Well I was board so I made an OmniTrack in Alibre Designs. It uses square aluminum tubing as the frame. Then i drilled some wholes in it and welded a few connector pieces on it, put in the shaft, bushings, and roller and here it is. The roller isn't perfect, I know, so try to focus on the shape of it.


I'm an extreme "I want to make something" state.

Re: Easy OmniTrack
 

Do you have a design for the drive sprocket?

Re: Easy OmniTrack
 

I'm thinking right now that I'll either make a custom drive shaft using hex stock or do the track as double wide and integrate an aluminum chain in there somehow. I'm leaning towards the hex stock idea. I think I'll will it with the roller imprints on it so its grabs the rollers as it turns. It'll be pretty tricky. Looking at it, If I used two wheels with high traction matierial on it and then put high traction matierial on the link's frame, it would work pretty well. The only problem would be alignment would need to be near perfect. I'll cad one up real quick in a bit.

Re: Easy OmniTrack
 

use a cylinder that the tracks will wrap around at each end and then make a spherical hole around it for the balls, and then just bore a hole in the center. You can use anyway to drive it, because it will just be like attaching a sprocket, spur gear or whatever to a normal wheel.

Re: Easy OmniTrack
 

Just a quick question... is there an actual application you can think of for this? It seems to me to be heavier than normal track, and have less traction. It would help turning, I suppose, but at the expense of pushing forse, which is usually the purpose of a track. Is there something I'm missing here?

Re: Easy OmniTrack
 

Heres a way to drive it.

The reason this is being made is because it offers all the advantages of tank treads and the advantage of holonomic drive (put them on 45's to each other). It doesnt have the disadvantages such as hard to turn and being easily pushed. The only disadvatage I can think of is that its more difficult to turn tank tread.

Re: Easy OmniTrack
 

Omnitrack is like omnidrive right? Move in all directions but with tracks. I dont know how that would work but good luck... I think.

Re: Easy OmniTrack
 

I had a simalar idea after competition this year after our omni wheels proved flimsy (I still have some parts)
I would really like to see this work, but my team cant afford to try :(
to drive, I would suspend the track betweeen two chains or belts
It would be much smoother insted of trying to drive a "square wheel"
it would also need support in the middle (difficult with indevidual links)
I would use sliders maybe delrin or something tough (and replaceable)

Hopefully next years game warrants using something like this

Re: Easy OmniTrack
 

Ok, so I got a little inspired. (Modeled in Rhino 3d)

Re: Easy OmniTrack
 

Now thats just creative. :ahh:

Re: Easy OmniTrack
 

For anyone having trouble visualizing what it would look like, I made this-


I love Rhino3D

You can fill in the guts yourself.

Re: Easy OmniTrack
 

These Omnitracks(i preffer the mecanums tho) seem like an awesome idea but i feel that the use of them will be difficult, look at the cost of mecanum wheels to produce. People are talking about over 1000 dollars to machine. Then there is the weight issue for these, and how big will the drive wheels need to be, in this case i think that it will prove much more effective to go with standard mecanum wheels then these treads(but of course someone will likely prove me wrong now)

Re: Easy OmniTrack
 

hey, never said they were effective, cost especially. I just think they're freakin' cool.

Re: Easy OmniTrack
 

One thing I learned this year is that there are tons of teams that can build really effective robots that can complete the task extremely well. I doubt that a lot of other teams (including us) will ever get quite that good at designing robots, so it is better to just build a unique robot that will be noticed for it's creativeness.

I'd really like to see a robot with those mecanum tracks, it would be out of this world!

Re: Easy OmniTrack
 

Clearance between the rollers and belt is only 1/8", but someone could maybe use these to make a less expensive(?) version:


angled roller belts from Interlox

Re: Easy OmniTrack
 

The similarity between both our designs is amazing. Great minds think alike?

http://www.chiefdelphi.com/forums/sh...ad.php?t=46501

Re: Easy OmniTrack
 

Why not just set the two sets of tracks perpendicular to each other? It would be heavy but it would be able to push like a regular tank drive and maneuver like a holonomic.

Re: Easy OmniTrack
 

What is the advantage over traditional omni wheels?

This doesn't provide any more traction than those...

Re: Easy OmniTrack
 

Well wouldn't it provide more traction than omni wheels for the same reason tradtional treads provide more traction than regular wheels?

Re: Easy OmniTrack
 

Yes, it would -- if that reason existed. To a good first approximation, however, treads do not provide more traction than wheels.

Re: Easy OmniTrack
 

The way I always thought of making omni tracks simply threading a cable through a bunch of round rollers.
It's not a track exactly, but it's similar

Re: Easy OmniTrack
 

The issue then becomes on designing a wheel system that will drive it. Threads used toothes pulleys, but a cable would be harder. And yes, your idea is a lot simpler.

Re: Easy OmniTrack
 

Imagine a paddle-wheel with a V-shaped slot in the center of each paddle, with the V opening outward from the axis of the wheel. The cable would then be slung over the wheel so that the cable rests in the innermost point of the V. Each roller (they would probably have to have a diamond-shaped cross-section), with the cable threaded through them, would rest between paddles as the wheel turns.

Re: Easy OmniTrack
 

That was more or less the way I was planning on doing it

Re: Easy OmniTrack
 

Well I know from my basic physics class that surface area doesn't come into account when calculating friction force, but thats in an idealized environment, with no "chattering" and in which the surfaces are sliding past each other, not applying torque in the sense that we're talking about. But I thought that in the real world, surface area did play a role in how effectively a vehicle translated spinning wheels or treads into movement. If thats not true, then why do race cars have extra wide towers, and road bikes extra thin ones?

Re: Easy OmniTrack
 

read this post http://www.chiefdelphi.com/forums/sh...8&postcount=13

Re: Easy OmniTrack
 

Traction is a tricky subject. It seems to contradict itself all over the place.

In FIRST, the good brecoflex tracks can have a 1.5-1.6 coefficient of friction on the field (from a brecoflex catalog I saw a while back). The better tread a lot of teams use has a debated 1.2-1.3 cof (wedgetop/roughtop - variation comes from diferent materials and different test). I bet if the wheels had the same tread the belts did, they would have a 1.5-1.6 cof as well.

What I said above is fact, from experimentation (except the final guess). I still am not even close to understanding it completely.


On another note, these tracks would be better at climbing than traditional omnis.

Re: Easy OmniTrack
 

I'm confused on the whole traction thing. I've been shown the math on why surface area shouldn't influence traction, but here's why I disagree:

I built a kitbot with 4 andymark kit wheels, all powered from two BB gearboxes. It pushed a decent amount of stuff in our shop. Then I pulled the wheels off, and doubled up the andymarks. Now I had two wheels per shaft, effectively doubling the surface area on the ground. This bot pushed more, and could shove me across the ground when I was fully resisting. The other setup, with single wheels, could not shove me.

I have yet to take physics (that's next year for me), but I'm still basically familiar with the issue... Anyone care to hep me out here?

Re: Easy OmniTrack
 

Trust your experiment. Math does not control the world--it only attempts to describe it.

The friction equations in first year physics are basically only engineering approximations, and do not hold for sufficiently roughened surfaces, nor for surfaces of materials with unusual, non-linear properties--like rubber.

If you want to use the first year physics equations, then you can think of it like this--rubber has a non-linear "coefficient of friction." For most rubber material in most traction situations, the apparent (in other words, the experimental) coefficient of friction is higher when the rubber is more lightly loaded (less weight per area of the contact surface) than when it is more heavily loaded.

For a robot built to a maximum weight limit, more rubber surface on the ground means less pounds per square inch on the rubber surface, giving a higher apparent coefficient of friction and more grip for a given robot weight. So treads, or doubled wheels, have more grip than lower-surface-area alternatives using the same material.

Carlo Bertocchini, who built the combat robot Biohazard (and was on a winning FRC team if I remember right) answered this question several years ago (near the bottom of the linked page)

http://www.robotbooks.com/robot-materials.htm

Re: Easy OmniTrack
 

WOW! =O i've been working with this idea for a few years. Unfortunatly my CAD files were on a USB stick that was stolen at school. Heres what I have http://www.putfile.com/pic.php?img=6046594 it's in Solidworks(i'm not verry good at solidworks), i just installed Inventor 2008 the other day so i'll try and model it in there, it'll look alot nicer.

I think we need to discuss this, It's applications in FIRST are vast. And people are looking at torque more then menuverability, I think the instant directional changes will be more valuable then the ammount of torque the treads can put out, which happens to be only limited by the output of your gearbox =). Just so everyone knows, the treads should be placed in a Box formation, 1 on each side of the box, or in an H formation, this allows for multiple axis of stability and movement. I'd love to get into an AIM chatroom with you guys, my SN is Phillysteak527.

Re: Easy OmniTrack
 

I've been doing some thinking on this idea, and Here's what my brain has come up with:

Without any idlers along the main bulk of the Omnitrack, the weight and grounded traction area (pardon my incorrect terminology, I'm very tired) is only the two drive sprockets. In any track system, the presence of many idlers is what gives it the advantage over a standard wheeled system. However, the track would give it the ability to climb over stairs, assuming the links could hold up to that force.

So this design wouldn't really aid in the pushing ability, it would more of make an omni system that can climb stairs, which hasn't really been seen before in FIRST, unless I'm mistaken.

Re: Easy OmniTrack
 

I never really saw a reason for this. It would only help and moni get up stairs or a ramp if you hit it prefectly cause otherwise the tracks would lift and you would have a point contact anyway.

I also didn't see the traction advantage since well... You guys seem to have that one covered. I could see it if you were rolling across a very soft sureface like pluch carpet cause there would be more rollers to grab the carpet but still seems like a lot of work for not much gain.

After three years of doing omnis I will safely tell you that they DON'T go up ramps, stairs, or any major feature in the ground. Minor ones are easy enough to roll over but if its more than half the heght of your roller then you have a problem. I also have found that you won't be pushing your opponents around the field, this does not mean that you can't play defense but you won't win a pushing war, or macht, or even scuffle :p .

However, I can see why you would want to do them from a cool standpoint. When people first started talking about these a year ago I got into it and modeled an omni track and went a little overboard and also did a mecanum track (My comp hated me for that one). Sadly however my old comp died and I lost the models.

Re: Easy OmniTrack
 

Perhaps I'm misinterpreting your use of "omnis," but if we're talking about using omniwheels on a robot, I'd argue that none of what you've written above is true.

Re: Easy OmniTrack
 

not omnis when used in the terms of a standard drive train. they can and are very useful and powerful for that application but in the case of a holonomic what I have written is indeed true from experience.

I'm sorry for not being clear on that. i just always saw the application of the omni treads for a holonomic and so didn't think to clarify. Also when I said that it can't roll over anything that isn't half the height of the rollers I was exagerating there too.

sorry

Re: Easy OmniTrack
 

I have been working with omni drive systems for years. I first come up with the design in 2002 but in 2004 we built one and wone a Xerox creativity award at Great Lakes. Visit our webb site for pictures and tech tips @ www.team1322.org . Per your Idea about tank track omni drive, your idea is a good one and thier are different ways to make it work but the key is when you install the two tracks for your drive you can add two more at 90 degrees. Doing this it will look like a four sided drive. When you drive the different motors it will allow you to go side ways forward, back, angles and rotate. Thus you have a omni directional system. With the number of wheels you will have good traction and can become a pusher robot. the only problem is keepng down the weight. We used omni wheel drives with the motors in the wheels.
http://team1322.org/robotics_04-05.htm

Re: Easy OmniTrack
 

I have been working on a design also that will incorporate 3 different driving selections: 4 wheel steer (swivel steer), crab bot steer, and normal 2 wheel forward backward steer. I have been working hard, and this post I am pretty sure has inspired me and put me over the edge. I will post my drawings as soon as they are done, but I think so far that these are extremely intelligent designs, and I can see them working very well in the future.

Re: Easy OmniTrack
 

I do find it intersting on the differnt ideas for omni drive wheels or track. In 2004 we used omni drive wheels and was able to climb the stairs of that game. The wheel segments acted like teath to grab the steps to climb. I also came up with a omni track design, My idea was to design the track like beads on a pearl necklace and the drive sprockets looked like paddle wheels with each V shaped paddle would come down between the beads and the weight would be on the axle thus alowing for the rollers to turn free. The steel axles would have enlaged ends that would snap into the holes of the Plastic balls. You than can Paint rubber (avalable at Granger) on the wheels for traction. This does not sound that heavy but a lot of work. check our web site for all the wheels we Painted. http://team1322.org/robotics_04-05.htm also check the tech tips for our omni wheel designs