18-05-2008 20:32

Andrew Bates

Re: pic: Omni Robot

This is a really cool design nice work. It looks like the frame is made of Lexan or is that just a product of the rendering?

Also whats the green thing in the middle?

18-05-2008 20:49

vivek16

Re: pic: Omni Robot

It is a cool design. It would be pretty darn expensive though. Victors are 150 dollars atleast and the omni's are not cheap. It would be pretty nifty to see this thing in action

-Vivek

18-05-2008 21:41

hillale

Re: pic: Omni Robot

looks like the green thing in the middle might be a battery cell pack.

18-05-2008 21:49

bear24rw

Re: pic: Omni Robot

It is made out of 3/16 lexan, the green thing is a 10 D-cell 12v 10AH battery pack.. ill give more details later i gotta go finish my term paper lol

18-05-2008 21:55

robomaxx

Re: pic: Omni Robot

If this robot does not have to be FIRST legal, then why not use HB-25's instead of victors. They work just as well, but are only 50 dollars.

18-05-2008 22:01

Akash Rastogi

Re: pic: Omni Robot

HB-25 Link provided for aforementioned speed controller. (We have enough Vic's)

Nice design. It looks like it'd be fun to drive. I think we have plenty of Victors in the shop.

18-05-2008 22:02

lukevanoort

Re: pic: Omni Robot

Depending on the motors used, using HB-25 speed controllers could be an expensive mistake, since HB-25s have about 37% less continuous current capacity than Victor 884s.

18-05-2008 22:10

Kyle Love

Re: pic: Omni Robot

Lexan can also allow for a good amount of "flex" in the frame, which can be good with this style of drive, along with mecanum also.

18-05-2008 22:39

Mike Nawrot

Re: pic: Omni Robot

Yes, victors are expensive, but when can get them for free because you have so many around the shop, they're the best way to go. That's why he has the blue 60 mm fans on there. The ones he found don't have fans. I'll leave the rest of the explaining up to Max. Haha.

18-05-2008 23:02

Tim Baird

Re: pic: Omni Robot

Yeah, make sure to use a healthy supply of cross-bracing in between each layer to minimize that flex. A Lexan chassis is very feasible, you just have to make a good, sturdy design and then follow through in manufacturing. Goodluck!

18-05-2008 23:02

bear24rw

Re: pic: Omni Robot

also the fact that they wont fit in between the bottom two plates if they have the stock fans on there.. but yeah we already have the victors so thats no problem, the biggest problem is where to get the lexan water jetted lol

19-05-2008 00:11

Nikhil Bajaj

Re: pic: Omni Robot

This mostly depends on the gear ratio they're using. With omnis, you have less traction due to friction in general due to the rubber used typically being more slick than traction wheels, so it'll be easier to spin out rather than stall on carpet. If the robot is geared for 25 feet per second you could run into problems with this (that number is an example, I don't know the exact threshold off-hand but you could use JVN's drivetrain calculator and the coefficients of friction off of AndyMark's site to estimate it. Or do what I do and forget every time so I draw the same free body diagram each time and solve the same equation.)

Since it is an omni-directional drive system, it should be relatively easy to get out of a situation where you are stalling motors.

That said, lukevanoort has a good point, when using the HB-25s using some 30A breakers is a very good idea to protect your investment. Remember the breakers for the Victors, too, I'd say.

By the way, how fast is this thing supposed to go?

19-05-2008 16:00

shock190

Re: pic: Omni Robot

If you cant get waterjetting done easily, something like this could be done relatively well with a bandsaw and jigsaw and a wonder file. It would just take longer and not quite as smooth, but it would work.

19-05-2008 17:41

Laaba 80

Re: pic: Omni Robot

Our team builds our entire robot out of polycarbonate. It builds a good chassis, and it looks cool.
Also, make sure you have a way to stop the wheels from spinning. I was the driver this year and we had an omni bot like your design. Trust me, it is really hard to drive, especially if you have no way of stopping the wheels.
Joey

21-05-2008 08:22

ajlapp

Re: pic: Omni Robot

you have one too many wheels.......

but it definitely looks cool.

Team 857 Kiwi Bot

21-05-2008 11:20

Foster

Re: pic: Omni Robot

Breakers are always good, but based on the picture the overall stall/current load should be pretty light. The weight of the proposed robot should be low.

I'd put the braking jumper switch on the Victors to the on position.

21-05-2008 14:54

Alex.Norton

Re: pic: Omni Robot

If your actually looking at this type of drive train for the season I would definitely suggest building this to do some software developments because while it may seem uncontrollable when you first build it they can be made very stable.

Don't take the first spin on it and dismiss it right away. They are hard to get to be easy to drive but the process is rewarding and you will get a fast, fun bot to drive. It takes more than the breaking jumper on the victor.

22-05-2008 18:24

JasJ002

Re: pic: Omni Robot

very impressive.

23-05-2008 07:17

Foster

Re: pic: Omni Robot

I use code written by Arthur Dutra that was posted here as the basis for an omni control system. It works well out of the box. Can you post your code, since it sounds like you've put lots of work into it?

23-05-2008 18:43

Alex.Norton

Re: pic: Omni Robot

If your interested in looking at our code, PM me with your email and i'll send it to you. Keep in mind that we used the 2007 gyro to stabilize the robot and our machine had a tractor style suspension to keep all four wheels in contact with the ground at all times.

In terms of the suspension I can't entirely say if it absolutely necessary but we included one in all three omni bots that we built. We also used a gyro in all three bots and I can guarantee that it will be uncontrollable if you don't use one of the two, and very possibly both. All of our machine were very easy to drive once the correct constants for the control loop had been found.

25-05-2008 15:43

GBIT

Re: pic: Omni Robot

You took the words right out of my mouth....

25-05-2008 16:18

EEliteDefender

Re: pic: Omni Robot

team 1714 used a omni drive and it worked its was a fun system to drive good luck

29-05-2008 11:26

T3_1565

Re: pic: Omni Robot

yeah it looks really cool!! make sure you don't get thrown off the first few times driving it! it is hard to drive at first, but it is the most fun drivetrain I have ever driven!!! I love the lexan frame too! Whats the thickness of the lexan?? (I may of missed it if it were said somewhere.. sorry)