pic: Omnitrack Summer Project?

[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.

[Cody Carey]

Why not CNC punch them out? I am fairly certain that you can
punch 1/4 aluminum, and it would be alot more consistant/pretty.

Also... Why omnitracks? Won't a 4-6 wheel omnidrive perform just as well as a two track two wheel design?

[Tristan Lall]

Extrusion requires a difficult setup and expensive tooling; it's only cheap in huge volumes. But what about graphite permanent mould casting? If you can get a local casting shop to sponsor you, it wouldn't take much to make a few hundred links.

Basically, you'd need to mill out the mould into two graphite halves with sprues, vents and risers as necessary (usually CNC—a casting shop will be able to do this easily), and it's just a matter of mounting it to a standard fixture (which opens and closes the halves) before you're ready to pour metal (e.g. 390 aluminum).

[devicenull]

So, assuming you are going with a standard tank setup, whats to stop someone from going on the side of you, and pushing you straight across the field?

Doesn't look like it would offer much resistance to that.

[thoughtful]

Originally Posted by devicenull

So, assuming you are going with a standard tank setup, whats to stop someone from going on the side of you, and pushing you straight across the field?

Doesn't look like it would offer much resistance to that.

He explained it in his first post. If you can imagine, there are four treads, at each edge of the robot. So if someone pushes you from the side, the front/back treads should resist somewhat, in theory the system, if made, should be better at torque that the OMNI wheel drives.



Just a suggestion, instead of having 4 treads, why not have 2 treads on each side, and one in the middle(which intersects the turning center). This way if you need to implement the drive on a robot that herds or uses its back or front for other things, you will be able to fairly easily use the same concept. On a side note, this will make the robot more vulnerable to pushing.*Just a random thought*

[Jizvonius]

I think that Andy brought up a good point about using standard chain attachments with links mounted to them. I have been thinking about doing this for a little while, but haven't found the time. Maybe you can puts this to good use before I can.

Connecting links with mounting flanges can be found at McMaster on the last page of roller chain.


If you can get something similar to the part shown in the attached pic stamped out of plate to hold the rollers, I think that it will work when mounted to the chain. By properly sizing these parts, you may be able to make the chain lock in one direction giving the omnitrack rigidity between support rollers, but the ability to collapse around drive sprockets.



This is of course just concept, and needs tweaking.