pic: Team 935 Chassis Teaser

[railerobotics]

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[Thermal]

1/4" alu huh? Interesting choice i'd say, I don't think too many chassis are made out of alu that thick. How heavy is it?

[EricH]

How are those mecanums working out as turning aids?

[gyaniv]

What benefit do you get from the mechanum wheels if you have another 2 plaction wheels with wedgetop tread on them at each side?... won't it be better if you put 2 omni wheels instead?

[Nuttyman54]

Originally Posted by gyaniv

What benefit do you get from the mechanum wheels if you have another 2 plaction wheels with wedgetop tread on them at each side?... won't it be better if you put 2 omni wheels instead?

It's hard to tell exactly, but judging by the frame, the center two wheels are raised up slightly, so that on normal flat ground they're running straight mecanum, but when they go over the bump the traction wheels are there to help out.

[Lil' Lavery]

Originally Posted by Nuttyman54

It's hard to tell exactly, but judging by the frame, the center two wheels are raised up slightly, so that on normal flat ground they're running straight mecanum, but when they go over the bump the traction wheels are there to help out.

That was my take on it as well. They have a mecanum drive that is built to transverse the bump. And given the short distance between the wheels, they can do it with an awfully low ground clearance (and drive system in general), which can help with their CG.

Nice work.

[gyaniv]

You might be right... Though it doesn't seems so because the holes in the chassis for the bearings looks like they are in one line, and that both wheels are 8"... but hard to judge from this pic...
I heard of some times having trouble getting over the bump with regular mecanum wheel, since their robot slipped because the wheels didn't have enough traction.. so If it is what they did then it's a great idea, though even one wheel will be enough to help the mecanum climb over the ramp.
I would love to see a team "Reforging" a mecanum wheel and putting wedgetop tread on the small wheels

[Lil' Lavery]

Originally Posted by gyaniv

You might be right... Though it doesn't seems so because the holes in the chassis for the bearings looks like they are in one line, and that both wheels are 8"... but hard to judge from this pic...
I heard of some times having trouble getting over the bump with regular mecanum wheel, since their robot slipped because the wheels didn't have enough traction.. so If it is what they did then it's a great idea, though even one wheel will be enough to help the mecanum climb over the ramp.
I would love to see a team "Reforging" a mecanum wheel and putting wedgetop tread on the small wheels

Look at the center support struts on each side of the bearings. You can see that the middle two are higher than the end two. The middle two wheels are raised.

[abeD]

They are definitely not in line, looks between .25 and .5 inch raised middle wheels. If you look closely at the bearing then follow the horizontal line you will see it.


edit: beaten to it...

[IndySam]

looks sweet!

Are you guys planning on shims for bumper supports so those screws and bearings are inside the frame perimeter?

[keericks]

Originally Posted by gyaniv

You might be right... Though it doesn't seems so because the holes in the chassis for the bearings looks like they are in one line, and that both wheels are 8"... but hard to judge from this pic...
I heard of some times having trouble getting over the bump with regular mecanum wheel, since their robot slipped because the wheels didn't have enough traction.. so If it is what they did then it's a great idea, though even one wheel will be enough to help the mecanum climb over the ramp.
I would love to see a team "Reforging" a mecanum wheel and putting wedgetop tread on the small wheels

Actually, if you look closer, the centerline (CL) for the bearings are not in a line. Look at the horizonal "web" frame structure going through the mec wheel bearing CL ... now follow it over to the first traction wheel. Notice the jog in the frame structure upward, and that new web centerline passes through the two center traction wheels, confirming the earlier post of high centered traction wheels for bump assist. Cool design.

[KC1AJT]

if you look at the second plaction wheel there is a shadow under it, that is exactly what they are doing

[waialua359]

Originally Posted by Nuttyman54

It's hard to tell exactly, but judging by the frame, the center two wheels are raised up slightly, so that on normal flat ground they're running straight mecanum, but when they go over the bump the traction wheels are there to help out.

My guess is that they are not running straight mecanum on a flat surface.
The plaction wheels with treads are more than 8". Compare them side by side even with AM 8" omniwheels and they are definitely not the same height.
We ran the same setup with omniwheels on the end and they dont even touch the ground.
Correct me if I'm wrong, but is 935 doing this to get all 4 wheels on the ground, with a better turning ability?

[coldfusion1279]

Wow, cool looking, that's for sure.

If the traction wheels are for getting over the bump only, I would suggest re-testing without the wheels and maybe save some weight. If they are for pushing, that is a different story.

My question is, after all that machining, why didn't you weld the frame? Oxidation?

[sgreco]

It's worth it participating in FIRST just to see what 935's frame looks like...That is absolutely awesome...Really nice job!