05-02-2010 16:41

Thermal

Re: pic: Team 935 Chassis Teaser

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?

05-02-2010 16:43

EricH

Re: pic: Team 935 Chassis Teaser

How are those mecanums working out as turning aids?

05-02-2010 16:45

gyaniv

Re: pic: Team 935 Chassis Teaser

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?

05-02-2010 16:47

Nuttyman54

Re: pic: Team 935 Chassis Teaser

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.

05-02-2010 16:52

Lil' Lavery

Re: pic: Team 935 Chassis Teaser

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.

05-02-2010 16:58

gyaniv

Re: pic: Team 935 Chassis Teaser

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

05-02-2010 17:00

Lil' Lavery

Re: pic: Team 935 Chassis Teaser

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.

05-02-2010 17:02

abeD

Re: pic: Team 935 Chassis Teaser

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...

05-02-2010 17:05

IndySam

Re: pic: Team 935 Chassis Teaser

looks sweet!

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

05-02-2010 17:06

keericks

Re: pic: Team 935 Chassis Teaser

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.

05-02-2010 17:07

KC1AJT

Re: pic: Team 935 Chassis Teaser

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

05-02-2010 17:08

waialua359

Re: pic: Team 935 Chassis Teaser

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?

05-02-2010 17:48

coldfusion1279

Re: pic: Team 935 Chassis Teaser

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?

05-02-2010 20:56

sgreco

Re: pic: Team 935 Chassis Teaser

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

05-02-2010 21:05

Alex Cormier

Re: pic: Team 935 Chassis Teaser

Sorry... I just have to.

Those middle wheels are not "plaction" wheels. They are IFI traction wheels. AndyMark sells the plaction wheel and are black plastic.

05-02-2010 21:55

waialua359

Re: pic: Team 935 Chassis Teaser

Yes they are!
I'm getting old.

05-02-2010 22:53

J_Beth

Re: pic: Team 935 Chassis Teaser

I'll be honest.. fellas, the chassis is looking great. But.. I could've used a little more cowbell. The last time i checked we don't have a whole lot of robots that feature the cowbell.

05-02-2010 23:13

KC1AJT

Re: pic: Team 935 Chassis Teaser

agreed

06-02-2010 09:19

johnr

Re: pic: Team 935 Chassis Teaser

It's a shame that you can't just put your bumpers on this year and call it a day. Looking at all the screw holes at bumper height i would imagine you guys are just going to add a flat piece of stock over them to expand your frame perimeter.

06-02-2010 12:10

whcirobotics

Re: pic: Team 935 Chassis Teaser

Interesting choice! Very facinating to see 1/4

06-02-2010 14:33

Techgirl675

Re: pic: Team 935 Chassis Teaser

Looks a bit on the heavy side, but should work great!

06-02-2010 15:06

Joe Johnson

Re: pic: Team 935 Chassis Teaser

I am going to be a bit controversial and say that while the chassis is a work of art in many ways, I wouldn't trade it for the chassis that our team is building with little more than hand tools, standard C sections from McMaster and about 2 hours of mill time poking in a few critically placed (and large diameter) holes.

Every team has it's own strengths and weaknesses. Teams should play to their strengths but I fear that some teams use certain technologies on their robot mostly because they have access to it (e.g. a CNC mill) rather than because it it the best technology to use.

A contrarian view presented for your consideration. Please believe me that it is not intended to in a mean spirit and that no offense is intended.

Joe J.

06-02-2010 15:16

Akash Rastogi

Re: pic: Team 935 Chassis Teaser

I love this point of view, mostly because it is similar to my view on the matter. I have friends on other teams who love using their CNC equipment even when they probably don't need to to cut weight or make a part quickly/precisely. I also have friends on other teams who have amazing facilities, but limit themselves to what they actually want to get machined.
We are similar to the latter example. We have pretty great resources and fabrication available, but its usually just used for very crucial components that must be machined in a way we can't do on our manuals. During the design process, we also try to avoid heavy machining or CNCing parts while drawing the parts in CAD.
An example of our machining resources - http://kozakproducts.com/facilities.html http://www.gpsheetmetal.com/index.html

I may open a new thread for this type of discussion. Or, Dr. Joe, if you would like to start one I would be interested in reading what others have to say.

The frame you guys have looks really sick. I look forward to seeing how our mentored team 2395 does with/against you at OKC regional!

08-02-2010 15:24

Maxzillian

Re: pic: Team 935 Chassis Teaser

I really couldn't agree more. There's two sides to the view, for certain. On one hand it leans students to be more creative and flexible by working within the realms of the materials provided and does a great job of teaching them how to be resourceful in making components work with each other with what can sometimes be considered a minimalistic, but effective approach.

On the other hand, having an abundance of resources allows the students to broaden the scope of the project and be more creative by allowing them to design custom components from a clean sheet and use modern practices in creating their robot; both exposing them to the design aspect of engineering and the practical aspect of manufacturing (all though this is by no means the limit of the scope of FIRST).

I believe both are very valuable skills for students to learn, but it seems to be rare to have both under the same umbrella.

Our program certainly leans towards the latter of the two approaches I mentioned. It's certainly not a bad thing, but I admit I would like to see the students "squirm" and try to be more resourceful in meeting their goals.

I think resourcefulness is a skill rarely taught in education after high school, but can often be more valuable than learning modern practices.