09-02-2004 21:47

abeD

Re: pic: Team 710 Drive module

Here's one of our drive modules for this year its got two wheels and both are connected by chain...that's all i'll say for now oh and one on each corner of our robot

09-02-2004 22:01

Jay H 237

Re: pic: Team 710 Drive module

Is it 4 wheel drive or 8 wheel? What I'm asking is will the lawnmower tires and the skyways be touching the ground at once or will the assembly pivot so you could have only the lawnmower or skyways? I imagine you chose the lawnmower wheels to have more grip for climbing.

Or maybe you're planning on mowing the lawn with your robot after competition? A robotic lawnmower!

09-02-2004 22:02

abeD

Re: pic: Team 710 Drive module

Right now its 6wheel drive, 2 of the assemblies only have one wheel in them, and yes the assembly pivots



edit: originally we planned for 8 wheels but took out a 7th and 8th wheel due to weight (our biggest enemy this year)

09-02-2004 22:02

Joe3

Re: pic: Team 710 Drive module

My guess would be that those modules themselves actually rotate. Put down the slick wheels for turning, the beefy ones for pushing, and rotating them climbs the step too. We considered something similar to this, but decided against it for weight reasons.

10-02-2004 13:55

Greg Perkins

Re: pic: Team 710 Drive module

you could mill a TON of weight out of that aluminum plate, maybe on all 4 you could remove a lot of it and be able to put all 8 original wheels back in. just a suggestion

10-02-2004 14:59

abeD

Re: pic: Team 710 Drive module

Ya we thought about takin out some pieces. Those two-wheel module weigh about 6.7 lbs and the other ones weigh only 6, only problem is we don't have much time to take and mill out some weight and the structural integrity of those is really important

04-03-2004 00:15

Dan Richardson

Re: pic: Team 710 Drive module

The loss of structural integrity compared to the weight gained is not worth it.. WE milled out 1 fork panel.. ( more like speed wholes.. but they were big ones :- ) and we lost less than .1 lbs

I don't disagree we could use some weight. But when it comes down to it.. its not really a ton

It was barely noticeable

04-03-2004 00:20

Madison

Re: pic: Team 710 Drive module

You could remove a considerable amount of mass from each of those plates while doing relatively little to change the structural integrity of the design.

Think about bridges, for example. Trusses support immense load, yet they're largely open space. Cutting a similar pattern of triangles into plates such as yours is often an effective way of reducing weight while maintaining strength.

04-03-2004 00:29

sanddrag

Re: pic: Team 710 Drive module

We replaced a 3/16 solid plate with 1/8 lasercut and sides bent down and it is 2 lbs lighter. It is still just as strong. We replaced another 3/16 solid plate with a 1/8 solid plate with sides bent down and saved 1.25 lbs there. We replaced the 1/2" di steel hook with a 3/8" di steel hook and saved about 2 lbs there. We replaced the .125 sheet metal pivoting arm with one made from .063 and there is only one place where it flexes where we just added a little .063 thick brace. Saved abotu 2 lbs on that. We chopped down our window motor/arm mounts and cut the $^#% out of the 3/16 mounting plates and saved about another 2 lbs there. We removed the van door motor mount completely and lightened the U-pillow block and saved about .5 lb there.

We also lightened everything we could from the start (axles, gears, sprockets, shaft collars) Without the hanger, our robot is basically the same as last year's, except about 35 lbs lighter. I'd say we did a good job with lightening. You will see strategically placed cutouts and bends and a well chosen material thickness, not a whole bunch of speed holes.

A lot of times in FIRST the strength of a component is largely underestimated and the forces applied to that component are largely underestimated. Sure it is cool to have a robot built like a tank but when it is 130lbs and all it does is drive, that is not cool.

You don't always need thick material to get the job done. Throw in a couple bends and it makes it a lot stronger.

Our battery/compressor tray is only .040 thick but it doesn't flex because it has bends.

Over the off-season, each team should really assess the strength of each component and try re-making it out of a thinner material or with more cutouts.

04-03-2004 00:32

Greg Needel

Re: pic: Team 710 Drive module

it's amazing how simalar those are to ours.....

04-03-2004 00:33

sanddrag

Re: pic: Team 710 Drive module

linky no worky

EDIT: Picture link above fixed now.

04-03-2004 00:34

abeD

Re: pic: Team 710 Drive module

From what i have seen you guys 73, us 710, and 258 have a similar design with the "gurney" style drive.

04-03-2004 00:35

Greg Needel

Re: pic: Team 710 Drive module

fixed

04-03-2004 00:44

Dan Richardson

Re: pic: Team 710 Drive module

Well except for the fact that have a considerable amount of spacers running through the centers where these designs would be cut out. And we did run into problem withs spherical our cuts weakening the system. Infact the forks we milled where the only ones we had problems with

I was not saying that it couldn't be done.

I was saying that the difference in the weight made is basically nothing. its 3/16th alluminum and we could cut out a max of about 1x2 inches. Weighing only a few grams. ( to be exact its about 0.0360 lbs per piece )

If it had been better designed in the beggining when those parts were designed it could have been designed with the cut outs inplace. But with our current system it can not be done with enough effectiveness to cause reason to do it. But again, the extra work done on it, and the weight gained we felt were too minute to deal with under our certain time restraints.

THanks for the advice tho keep it coming

Dan

ps. see our bot in action ( sorry for bad editing job, I'll be re-editing this weekend hopefully ) View Us

Our forks in action

Us hanging because of our lifting system

04-03-2004 00:54

abeD

Re: pic: Team 710 Drive module

Heres a lower resolution vid (5MB as compared to 25MB)

Low Res 710 Video

ps .avi's soon to come if this one doesn't work (people have told me that it won't work on their computer.)

04-03-2004 01:03

Greg Needel

Re: pic: Team 710 Drive module

that is very cool....we only use ours on the back of our robot and have an omni wheel bar that comes down and suppports the front...i really like the automation of the system...what are you using for the feedback... limit switches?

i like it and look forward to seeing this bot inaction

04-03-2004 01:09

abeD

Re: pic: Team 710 Drive module

Thanks!

We use banner sensors, one in front of each wheel. The way it is set up is that when one of the sensors gets over teh step it pulls either the front or the back up. The driver controls if the banner sensors are activated or not with the trigger button on the joystick. I think you can see the banners in one of our posted pics. One thing we have to do at comp is reset the banners to the hdpe on the step. Works well for the most part and takes one thing out of the driver's hands (not that me and dan couldnt do it )

04-03-2004 01:10

FotoPlasma

Re: pic: Team 710 Drive module

Greg, as abeD said earlier, we're doing the same type of drivetrain. We are going to be using limit switches for feedback. We considered using other kinds of proximity sensors, but due to time and money constraints, we chose to go with the limit switches we had lying around the lab.

How about you guys?

04-03-2004 01:14

abeD

Re: pic: Team 710 Drive module

look here you can see the banner in front of the back wheel.

04-03-2004 01:21

Greg Needel

Re: pic: Team 710 Drive module

we have a banner sensor on each weel that counts wheel speed.....as for climbing we either have nothing or we are using limit switches...i belive when the robot was shipped we had no automated way of getting up the stairs but i was promised it was being worked on, and since i have been on spring break i have no idea what progress has been made. i know that we are using a banner to determine height of our arms and with a linear pot controling the height of the arms....the nice thing about this is that we have clicks (for lack of a better word) at specific heights (stationary goal, mobile goal, hanging) so that the driver doesn;t have to guess and can just snap to the height.....i do think that automating the climbing with this type of drive is essential and we will have it by cleveland....anyway i am going to bed cause i am driving to trenton tomorrow morning for the NJ regional.....good job guys and good night