Drive Train Prototype

[Chris is me]

Originally Posted by Ether

Ah. Looks like they've been re-designed. The roller mounting tabs look a lot sturdier. It looks like the rollers still rub against the mounting tabs though. That's a bit disappointing.


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I think that's an intended feature of the wheel; you can tighten and loosen the rollers to get varying degrees of forwards versus sideways traction.

[Ether]

Originally Posted by Chris is me

I think that's an intended feature of the wheel; you can tighten and loosen the rollers to get varying degrees of forwards versus sideways traction.

So it's not a bug, it's a feature? :-)

Seriously though, even if you loosen the rollers, they are always end-loaded when the wheel is being driven. This creates substantial friction. Roller bearing friction increases traction in the fwd/rev direction, but decreases traction and force in the strafe direction. For many applications (like Breakaway?) this may be a good trade-off.

I like the look of the new steel end-plates. The mounting tabs look quite a bit more rugged. The aluminum tabs on the 8" AM mecs bend very easily - even to the point of locking up the roller.

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[jamie_1930]

Originally Posted by GarrettF2395

Darn it! You guys beat me to it.
I've been playing around with this idea in my head for awhile now, though it's great to see someone actually build it.

Great work, make sure to run some good tests on it and let us know what you find!

That's pretty much what what I was going to say. I had already started CADing this and was trying to think of some other methods to switch it than pneumatic cylinders, but nonetheless I love it, keep up the good work guys.

[Alan Anderson]

Originally Posted by Ether

Seriously though, even if you loosen the rollers, they are always end-loaded when the wheel is being driven. This creates substantial friction.

I don't understand. Are you stating that as a deficiency of this specific wheel design, or of mecanum wheels in general?

[rutzman]

Originally Posted by GarrettF2395

Darn it! You guys beat me to it.
I've been playing around with this idea in my head for awhile now, though it's great to see someone actually build it.
Ok question time.
Is there a reason as to why you decided to have the mechanums on the outside instead of the inside?
Did you guys play around with any other configuration ideas, such as having all 8 of the wheels on the ground at once?

Great work, make sure to run some good tests on it and let us know what you find!

While I can't speak for the OP, when I CADed up an idea almost identical to this after Atlanta I put the traction wheels on the inside to allow for easier turning in that configuration.

[AdamHeard]

Originally Posted by 548swimmer

For Overdrive we had a robot with eight wheels that could switch between two sets of four. The chassis sitting in our shop weighs under 40 lbs, though barely.

I'm not sure what you're referring to, but when my team quotes drivetrain weight we talk EVERYTHING; wheels, electronics board, battery mount, chain, bolts, etc...

If you hit 40lbs with that standard, I'm highly impressed.

[electron]

Originally Posted by GarrettF2395

Darn it! You guys beat me to it.
I've been playing around with this idea in my head for awhile now, though it's great to see someone actually build it.
Great work, make sure to run some good tests on it and let us know what you find!

I must say that I too have been toying around with this idea in my head. impressive work, though. I hope you guys get to use it in next years game

[Bjenks548]

As far as the 40lb one from the robostangs:

I haven't weighed it myself but heres a picture of it. Imagine changing the larger wheel for a mecanum and mirror those wheels in the front. http://www.chiefdelphi.com/media/photos/27459

[548swimmer]

Originally Posted by AdamHeard

I'm not sure what you're referring to, but when my team quotes drivetrain weight we talk EVERYTHING; wheels, electronics board, battery mount, chain, bolts, etc...

If you hit 40lbs with that standard, I'm highly impressed.

It's about 40 lbs with all the wheels, the old IFI control system, battery MOUNT but no battery, and all the pneumatics.

[Andy Baker]

Way to go Nitesh and WBI - this is a cool design! I hope you bring this to IRI so we can check it out.

Originally Posted by Ether

I like the look of the new steel end-plates. The mounting tabs look quite a bit more rugged. The aluminum tabs on the 8" AM mecs bend very easily - even to the point of locking up the roller.



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The bodies of these wheels are actually old and an inferior version of the current version. The plates used on this jump design are from 2008. These tabs were significantly less rugged, since the steel wall thickness was only 0.04" instead of the current thickness of 0.05".

I find that the 8" Mecanum tabs are quite sturdy.

Andy B.

[nitbaj]

Originally Posted by Hawiian Cadder

how much does that weigh?

I currently weighs around 90 pounds with everything on it. It's pretty ridiculous, but we didn't really worry about weight when designing it this time around. The frame members are pretty much all 80/20 and we didn't put lightening holes in any of the other plates, so I imagine the weight could drop quite a bit. Weight will probably be one of the next big considerations in this design.

Originally Posted by GarrettF2395

Is there a reason as to why you decided to have the mechanums on the outside instead of the inside?
Did you guys play around with any other configuration ideas, such as having all 8 of the wheels on the ground at once?

We put the mecanum wheels on the outside because we thought those would be the primary driving wheels, and then the traction wheels would be used in a pushing match or a similar situation. And if a robot with a relatively high center of gravity is moving quickly on mecanum and switching directions, it is much more stable to have the wheels on the outside.

We thought about different things you could do with all 8 wheels on the ground, but it seems like you don't gain a lot with that because you lose both your traction and maneuverability.

Originally Posted by Alan Anderson

Does it spin in place well? It looks like the mecanum wheels might need to be swapped.

We haven't had any problems with the mecanum drive spinning or strafing. I believe our wheels are on in the correct orientation. Unfortunately, we've already made the mistake of putting them in the wrong spot once this year, so we wouldn't want to mess up again .

Thanks for all the compliments, and if you have any other questions or comments, please post them.

[sdcantrell56]

Originally Posted by nitbaj

We haven't had any problems with the mecanum drive spinning or strafing. I believe our wheels are on in the correct orientation. Unfortunately, we've already made the mistake of putting them in the wrong spot once this year, so we wouldn't want to mess up again .

Thanks for all the compliments, and if you have any other questions or comments, please post them.

The wheels are definitely not in the correct orientation. When viewed from the top the rollers of the 4 wheels should form an X.

[Ether]

Originally Posted by sdcantrell56

The wheels are definitely not in the correct orientation. When viewed from the top or bottom the rollers of the 4 wheels should form an X.

When viewed from the top they should form an X.

When viewed from the bottom they should form an O.

see this post:
http://www.chiefdelphi.com/forums/sh...4&postcount=18


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[Aren Siekmeier]

Originally Posted by nitbaj

We put the mecanum wheels on the outside because we thought those would be the primary driving wheels, and then the traction wheels would be used in a pushing match or a similar situation. And if a robot with a relatively high center of gravity is moving quickly on mecanum and switching directions, it is much more stable to have the wheels on the outside.

Also, tank turning with the traction wheels will be easier with a shorter wheel base because you will get less tread rub.

[Thelilpluck461]

There is only one Solenoid on it, and two accumulators. If you look at the start of the video it is mounted just north of the power switch.