Re: Drive Train Prototype
 

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.

Re: Drive Train Prototype
 

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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Re: Drive Train Prototype
 

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.

Re: Drive Train Prototype
 

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

Re: Drive Train Prototype
 

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.

Re: Drive Train Prototype
 

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.

Re: Drive Train Prototype
 

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 :)

Re: Drive Train Prototype
 

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

Re: Drive Train Prototype
 

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

Re: Drive Train Prototype
 

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

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.

Re: Drive Train Prototype
 

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.

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.

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 :p .

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

Re: Drive Train Prototype
 

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

Re: Drive Train Prototype
 

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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Re: Drive Train Prototype
 

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

Re: Drive Train Prototype
 

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.