pic: Omnitrack Summer Project?

[Gabe]

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[sanddrag]

You're right. Making that one piece does seem like a job that could be done with a customextrusion. Sheet metal seems like a no-go if you ask me. You might be able to get the part lasercut or water-jetted out of thick plate, but it will have a draft angle, whigh might be okay though. Maybe you could put in some radiuses and have it CNC routed out of some good quality ply or some other good quality wood? Post on cnczone.com in the RFQ forum and people will jump at you with offers of how to make it and what it will cost.

I'm just curious, what is the problem with having it be two pieces of C channel as it is right now?

[Peter Matteson]

Why not band saw 2 different C-channels and rivet them together? That would basically do the same thing if you can get something close enough.

Also I would suggest solid aluminum rivets if you have the capability.

Edit: Missed that Sanddrag asked the same question.

[Raul]

Originally Posted by Dzdconfusd

Why not band saw 2 different C-channels and rivet them together? That would basically do the same thing if you can get something close enough.

Also I would suggest solid aluminum rivets if you have the capability.

Edit: Missed that Sanddrag asked the same question.

Riveting the two C-channels together will be a weak link (no oun intended) in the design. Rivets are not meant to hold much axial force - for that you need screws. Even steel rivets will come loose as the tracks will see lots of forces in the axial direction of the rivets.

[Greg Needel]

First i would like to say i love this concept and see how it would be really beneficial. I do have a question about implementation though. How do you anticipate driving them?...the only thing i can come up with is a custom pitch sprocket that fits in between the links, but i am not sure that that will be reliable.

[Andy Baker]

There are some good points brought up here.

Riveting the two pieces together is not good.

Custom extrusions are expensive... however, there are MANY types of extrusions out there these days. This profile looks like something similar to what I see every morning when I open my shower door. Also, Paletti has an extrusion that is somewhat similar, SP106, but the roller size would need to change (and that would be a tragedy, I must say!). My advice regarding extrusions would be to keep looking. Someone may have a standard profile that may work for you.

Greg brought up a good point regarding how to drive this thing, and this point may re-define how your rollers are mounted. This would make your extrusion profile different, possibly.

I suggest starting the design with standard attachment chain and build up from there. If you can design a roller frame that can mount between attachment chain flanges, maybe one on each side of the chain, then you would have a double-wide omni track. If you can get this design to be based on a 35 pitch attachment chain, then you can use standard sprockets and drive transmission components.

Good luck, and please keep us posted of your results.

Andy B.

[Greg Perkins]

Wow, just looking at this design has got me thinking, thanks for the idea! Anyway, what I propose you do, is design your "sprocket" out of hex stock or custom octagonal stock. Use them as your "wheels" to drive them, then design your tracks with less links so they contact the flats on the sprockets. I did a really crude sketch, but there's the concept, seems (IMHO) the easiest way to drive it.

[Greg Needel]

Originally Posted by Greg Perkins

Wow, just looking at this design has got me thinking, thanks for the idea! Anyway, what I propose you do, is design your "sprocket" out of hex stock or custom octagonal stock. Use them as your "wheels" to drive them, then design your tracks with less links so they contact the flats on the sprockets. I did a really crude sketch, but there's the concept, seems (IMHO) the easiest way to drive it.

Greg,

It is a good thought but remember that with your design the roller is the only thing that would be touching the drive. I guess if you inset the roller profile into the drive hex then it could work i just see long time issues with using the rollers as the driving feature in this assembly.

[Qbranch]

Hey if you need any help with machining, I can give you some advice at the least. Just send me a PM if you need any help.

I do CNC as well as manual machining.

-Q

[Greg Perkins]

I see what your sayin Greg, and trust me I know what you mean. I got some ideas up my sleeve, and when I get some time on my lunch break I'll actually start doing some CAD. It'll take some engineering, but you would have yourself something revoloutionary. Keep innovating!

[Bill_Hancoc]

I had an idea smiler to this a few weeks ago for a crab drive tank system. It involved 4 little individual triangular tread drives that could pivot on a dolly type system and then would be able to turn parallel to each other. The individual tread drives would be about 6-7 in long on the bottom and be based off a slightly modified 30-60-90 triangle. I wanted it to be fast along with really powerfull via a shifting gearbox but after calculating the speeds needed for a 1.5 in tread pully it would have been very hard to go fast since it would have reuired a really high rpm higher than the small CIM is i remember.

[RogerR]

Originally Posted by Bill_Hancoc

I had an idea smiler to this a few weeks ago for a crab drive tank system. It involved 4 little individual triangular tread drives that could pivot on a dolly type system and then would be able to turn parallel to each other. The individual tread drives would be about 6-7 in long on the bottom and be based off a slightly modified 30-60-90 triangle. I wanted it to be fast along with really powerfull via a shifting gearbox but after calculating the speeds needed for a 1.5 in tread pully it would have been very hard to go fast since it would have reuired a really high rpm higher than the small CIM is i remember.

in 2001 used belts instead of wheels to help them climb the midfield barrier. after a bit of searching, i found a pic here (thanks 229).

based on my calculations, to travel at 15 ft/s with a 1.5" driving pulley, you'd need almost a 2.5:1 gear reduction, which could be done in a single stage.

i think the biggest problem to overcome with your design would be turning the modules themselves; 6-7 in of high friction material would create a pretty good resistive moment.

this design is obviously do-able, there's just a few problems to solve; but then, how much fun would all this be without any problems?

[Simon Strauss]

I'm thinking that this would work better if the 4 treads were positioned like traditional wheels would be and the rollers at either 30deg or 45deg so that it would function just as mecanum wheels but with the advantages of treads.

[Greg Perkins]

Originally Posted by nycpunk

I'm thinking that this would work better if the 4 treads were positioned like traditional wheels would be and the rollers at either 30deg or 45deg so that it would function just as mecanum wheels but with the advantages of treads.

I assume you mean Omni wheels. And no, this won't behave like tank treads, it's a whole different animal. You've got to take into account being pushed, your coefficient of friction, and the need of the design. Is it doable, yes...is it practical, don't know. Do some research, and let us all know please!

[Gabe]

You all have gone through my same thought process. I will address every point, since you all understand what the idea is:

The links are made from 2 different C-channels and each riveted with two 1/8" aluminum pop rivets. The problem is that this is very weak and time-consuming. I have not considered screws, and I will try it. What size: 4-40 or 6-32? Nylon insert locknuts, or tapped holes?

To drive the tracks I am hand filing 2 drive sprockets out of 1/8" aluminum sheet, distanced apart using standoffs. This sprocket engages the ends of the 3/16" steel pins.

I was thinking about the standard attachment chain, but its would be much heavier if I used 2 chains. However, I might scrounge around and find some other material that would work for small rollers traction rollers to be used on just one chain.

Many people have suggested using waterjets or CNC mills. Why does a waterjet or CNC mill seem right for this project? Do you fabricate a bar with the correct profile, or do you cut individual links?

I do have a mill: my 14" Nicholson mill file. Ha, ha! Yes, do file my own #25 and #35 sprockets out of aluminum, and yes, i Am CrAzY. No need to buy those IFI sprockets!

Sorry about that. Just a random fit of insanity.