Team 3489 Category 5 Presents Storm Drive

[BBray_T1296]

You should be careful with worm gears in your drivetrain. If you slam into a wall (or other robot) at full speed, there could be a tremendous axial force applied directly to your worms.
Also you may be unable to push the robot around in your shop/etc

[HumblePie]

Originally Posted by BBray_T1296

You should be careful with worm gears in your drivetrain. If you slam into a wall (or other robot) at full speed, there could be a tremendous axial force applied directly to your worms.
Also you may be unable to push the robot around in your shop/etc

Actually, it turns out that, once broken in, these gearboxes can be back-driven with some effort. We don't want to make a habit of it, but it's possible. The spider couplings also help with some of the shock load. We disassembled 1 gearbox after 2 (often rigorous) regionals and a few demo events, and the gears showed no visible damage.

[wilsonmw04]

Originally Posted by Andrew Schreiber

Not really. Having the traction wheels on the outside makes you more stable when they are down. You are less likely to be spun (longer moment) and, have a bigger contact patch to keep your CG inside and prevent tipping. You don't need to worry about either of these with omni wheels due to them being slippy by design. (It's real hard to tip an omni bot due to them just sliding away and their habit of preserving their inertia, and spinning them is almost always easier no matter their contact patch)


Basically, there's design benefits to having your traction wheels on the outside. I can't come up with any obvious ones to having your omnis on the outside.

Come by our pits sometime. My kids would like to show you the advantages of a small traction wheelbase octocanum.

[Andrew Schreiber]

Originally Posted by wilsonmw04

Come by our pits sometime. My kids would like to show you the advantages of a small traction wheelbase octocanum.

Or you could tell me and save me a trip... I'll ignore that I said nothing about mecanum wheels.

[Abhishek R]

Originally Posted by Andrew Schreiber

Basically, there's design benefits to having your traction wheels on the outside. I can't come up with any obvious ones to having your omnis on the outside.

Originally Posted by wilsonmw04

Come by our pits sometime. My kids would like to show you the advantages of a small traction wheelbase octocanum.

Both have their advantages and disadvantages. It really depends on your end goal. Putting the traction wheels in the center gives you more turning ability with more control over where the robot ends up (no drift due to omni wheels). You would probably be using the omni's to escape a t-bone or something like that.

On the flip side, putting the traction wheels on the outside means you are primarily using the omni's most of the time. I believe this is what most teams who use butterfly do, because of the reasons Andrew Schreiber said - you have a longer wheelbase for stability when you're pushing or being pushed, and are less likely to be spun around.

[HumblePie]

Originally Posted by Abhishek R

Wow. This is really cool. Do you have any video of it in action?

Hope this works.........

http://youtu.be/arKL5XCXGfU?list=UUZ...8THLwUgtdjtgdg


You may notice a lot of "power slide" maneuvering with the 4 omnis. What you probably won't notice is much audio, and yes it was on. The team decided to go with 4 omnis rather than 2+2 omni/traction, which would have made the driving dynamics very different. The 4 omnis did make it much easier to place the robot on the field (by pushing it sideways) since the gearboxes were hard to backdrive, at least early on. The chassis has since been converted to 2+2 for demo events, and the chassis can be maneuvered in any direction now that the gearboxes are broken in.

[wilsonmw04]

Originally Posted by HumblePie

Hope this works.........

http://youtu.be/arKL5XCXGfU?list=UUZ...8THLwUgtdjtgdg

Looks nice. Have you tested it on carpet? One thing I noticed is that it is so quiet!

[Abhishek R]

Originally Posted by HumblePie

Hope this works.........

http://youtu.be/arKL5XCXGfU?list=UUZ...8THLwUgtdjtgdg


You may notice a lot of "power slide" maneuvering with the 4 omnis. What you probably won't notice is much audio, and yes it was on. The team decided to go with 4 omnis rather than 2+2 omni/traction, which would have made the driving dynamics very different. The 4 omnis did make it much easier to place the robot on the field (by pushing it sideways) since the gearboxes were hard to backdrive, at least early on. The chassis has since been converted to 2+2 for demo events, and the chassis can be maneuvered in any direction now that the gearboxes are broken in.

This is great. Omni wheels are a lot of fun once you get the hang of them.

[HumblePie]

Originally Posted by wilsonmw04

Looks nice. Have you tested it on carpet? One thing I noticed is that it is so quiet!

We've used it in 2 regionals this year, so absolutely. The carpet provides better traction and stability than on the polished concrete.

[Electronica1]

Originally Posted by Abhishek R

Both have their advantages and disadvantages. It really depends on your end goal. Putting the traction wheels in the center gives you more turning ability with more control over where the robot ends up (no drift due to omni wheels). You would probably be using the omni's to escape a t-bone or something like that.

On the flip side, putting the traction wheels on the outside means you are primarily using the omni's most of the time. I believe this is what most teams who use butterfly do, because of the reasons Andrew Schreiber said - you have a longer wheelbase for stability when you're pushing or being pushed, and are less likely to be spun around.

I am just going to put it out there. When your traction wheel and omni wheel are this close together, wouldn't it make more sense to put packaging of the system over the traction wheel base? Especially for the drive this thread is about, moving the traction wheels to the outside could net you about an extra inch at most of traction wheel base. While moving the traction wheel out would appear to make it more difficult to package.



Also, do you have any video of the drive at competition weight. It would give us a much better idea of this drives capabilities.

[EricDrost]

Originally Posted by Electronica1

When your traction wheel and omni wheel are this close together, wouldn't it make more sense to put packaging of the system over the traction wheel base?

From my experience, many drive train modifications/features provide only marginal gains, but when you look at the sum of all the little details, you will see a noticeable improvement.

Successful sports teams often use this principle of "aggregation of marginal gains", it works just as well in the FRC world.

[zinthorne]

Looks sweet. I would like to see the worm drive gearbox in action, it looks interesting.

[asid61]

Very cool looking! Do you have and specs in CAD for the individual module weight?
The use of a worm gearbox plus the cim mounting... such a beatiful combination.