15-04-2007 21:38

Re: pic: 1683 Concept 8 Wheel Drive

I like it! One suggestion though. For something like that, you may want to go with a welded aluminum 1x1 or 2x1 frame, which will save a massive amount of weight. However, if you don't have access to a welder, it provides either a good time to learn, or a bit of an issue (I'd prefer the lack of welding to be a good opportunity to learn to weld).

Other than that, looks good!

15-04-2007 21:43

MrForbes

Re: pic: 1683 Concept 8 Wheel Drive

I agree....and also you might want to think about bumper mounting as an integral part of the frame design. Consider making the end crossmembers taller and higher up, and flush with the ends of the drive assemblies.

15-04-2007 22:19

Sam N.

Re: pic: 1683 Concept 8 Wheel Drive

Team 1351 had an eight wheel chassis for the 2006 competition. We had 1x1 aluminum tube welded to the ends of the drive assemblies flush with the rear of the robot. The front of the robot was modified with a concavity for ball-pickup. the square tube provided free metal for bumper mounts (steel triangle brackets).

I also suggest putting a lightening pattern into your 1/4 inch plate. That can save a lot of weight, and if you have bumpers, you don't have to worry too much about structural stability.

15-04-2007 22:19

sdcantrell56

Re: pic: 1683 Concept 8 Wheel Drive

I was thinking that 8020 would provide for more mounting options. I have been debating with myself about 8020 versus welded and even I am not yet sure. We used a welded frame this year that proved to be indestructible so we do like welded frames it was just slightly hard to mount some things. The other thing about welding everything is that I would like to be able to remove the drive modules from the frame if necessary which will require bolts. I will try to make a second version using welded aluminum. Also I have not yet considered mounting points yet as I do not know yet what the basic frame will look like. Thanks for all of the suggestions.

15-04-2007 22:28

POLISH703

Re: pic: 1683 Concept 8 Wheel Drive

I think it needs more wheels ... But rather then that it looks pretty good. Nice Job. I do agree that you should make the front and back cross beams flush with the very front.

15-04-2007 22:38

MrForbes

Re: pic: 1683 Concept 8 Wheel Drive

There are other ways to mount things besides using 80/20. If you use a channel section across the front and rear ends, you have a built in mounting and reinforcement panel for the bumpers, as well as a top flange for mounting whatever "stuff" needs to go on top of the chassis. It might not be as easy to use as 80/20, but it also might be stronger in the ways it needs to be if you use something else.

example: 25's robot (and I was quite surprised to see it, as we have the same exact thing on the 1726 robot! pultruded fiberglass C channel)

But you do have to consider what materials and equipment and techniques you have available to construct your robot.

15-04-2007 22:59

Cartwright

Re: pic: 1683 Concept 8 Wheel Drive

How maneuverable is a eight-wheeled robot? This is my first year, and our robot was six-wheeled with a bit of a rock in it giving great maneuverability, but what gives an eight-wheeled drive an advantage?

15-04-2007 23:02

Re: pic: 1683 Concept 8 Wheel Drive

Mounting to a welded frame is very easy, as you're CADing the whole thing out in advance. You really have a ton of ways you can mount: Bolt,s rivets, JB weld or other heavy duty metal glue, and even zip ties.

As for maneuverability, it all depends on the gearbox, and how you arrange your wheels on the frame.

15-04-2007 23:54

sdcantrell56

Re: pic: 1683 Concept 8 Wheel Drive

8 wheel drive can be very maneuverable if the middle 4 wheels are dropped. For instance I have them dropped 1/8" which is the same drop that we have on our 6 wheel drive robots creating a rocking effect and eliminating scrub steer. Polish I do agree we could always have more wheels. Actually my brother is pushing for 10 wheels so that one can be lowered in the center. I did see your robot at the championship and that takes it to the max. I wish we could do something like that however I don't know how much more it would help us and we do not know how to properly tolerance for a gear drive like that. I also forgot my whole reasoning for having the braces offset into the frame. If you notice the front and back of the side plates are angled to provide clearance for climbing any ramp. In order to put channel on the front I would have to get rid of the slope unless there is some other way that I am missing

16-04-2007 00:22

MrForbes

Re: pic: 1683 Concept 8 Wheel Drive

You might want to consider making the drivetrain side plates taller, so they extend past the top of the wheels, then it would be a bit easier to mount the front and rear end pieces up high enough that they are in the bumper zone (over 2.5" off the floor). Although with the small diameter wheels, this might not work too well.

Using 6" wheels, axle near the bottom of the side plates, and 4" tall side plates, seems to work out well for using bumpers, also it keeps the wheels from being in the way of whatever gets mounted to the top of the chassis.

16-04-2007 00:27

sdcantrell56

Re: pic: 1683 Concept 8 Wheel Drive

I actually have made a new version that incorporates the transmission into the side plate to help with mounting. As for using bigger wheels, I am trying to use as small as possible wheels because of the weight savings of the actual wheels as well as smaller sprockets to achieve the same rpm. Additionally if we are going to be custom making the wheels the smaller size costs less in raw material, as well as the smaller side plates cost less

16-04-2007 00:43

MrForbes

Re: pic: 1683 Concept 8 Wheel Drive

Something you might want to consider is that if there is to be weight on the robot, you want it as low as possible....so having a heavy chassis and heavy wheels may be a good thing, not a bad thing. It forces you to keep weight off the top of the robot--the result is that your robot will spend it's life upright, on it's wheels, rather than falling over and laying immobile on it's side.

16-04-2007 01:21

sdcantrell56

Re: pic: 1683 Concept 8 Wheel Drive

I know that low weight is good however, as is this frame is not going to be overly light considering that there are 8 wheels and all of the chain and such associated with that. This year our drivetrain weighed 75 lbs and we are trying to cut that down considerably without losing too much strength. With our current drivetrain we were never out-pushed so I am using that as a basis to work off of. Also I think it is better to be underweight and be able to strap on ballast than be too heavy and forced to cut weight. I have posted a new version of this drivetrain http://www.chiefdelphi.com/media/photos/28328

16-04-2007 11:06

sdcantrell56

Re: pic: 1683 Concept 8 Wheel Drive

Here is an even more updated one I made the plates one inch taller and moved the braces flush with the front and back. I still have not decided what other braces to have on the inner frame. http://www.chiefdelphi.com/media/photos/28331?

16-04-2007 14:17

POLISH703

Re: pic: 1683 Concept 8 Wheel Drive

Quote:

Originally Posted by sdcantrell56 8 wheel drive can be very maneuverable if the middle 4 wheels are dropped. For instance I have them dropped 1/8" which is the same drop that we have on our 6 wheel drive robots creating a rocking effect and eliminating scrub steer. Polish I do agree we could always have more wheels. Actually my brother is pushing for 10 wheels so that one can be lowered in the center. I did see your robot at the championship and that takes it to the max. I wish we could do something like that however I don't know how much more it would help us and we do not know how to properly tolerance for a gear drive like that. I also forgot my whole reasoning for having the braces offset into the frame. If you notice the front and back of the side plates are angled to provide clearance for climbing any ramp. In order to put channel on the front I would have to get rid of the slope unless there is some other way that I am missing

16-04-2007 14:22

sdcantrell56

Re: pic: 1683 Concept 8 Wheel Drive

That arc idea sounds interesting however with only 8 wheels I think setting them on an arc would be the same as lowering the 4 middle wheels. Also about integrating the transmission into the side plates, I posted some pictures of what im talking about and they would also come off with 4 bolts. I greatly appreciate your ideas though as I really love your robot.