I’m the newbie, and since I’m the only non-college person on the team that can use inventor, I’ve been assigned to create a six wheel drive. I was wondering where I could maybe get the different parts to the wheel assemblies+dimensions, as well as some different wheel designs, dimensions, and if you could even post any ipt files for me to analyze, that would be great. Sorry I’m asking so much, I just got a big load put on my back.
Thanks in advance!
Take some time to browse the images in CDmedia. Especially search for 6 wheel drives, and check out the West Coast drives for the most minimalist approaches to this. Once you’re familiar with what is out there, model every part yourself. Taking shortcuts will get you through a build season, but doing it right can get you a job.
Alright, I found the Cdmedia, where can I find West Coast Drives, inside CDMedia?
Thanks!
Hello,
Check these websites out! They have a lot of parts already designed in inventor, which you can use.
http://www.firstcadlibrary.com/
http://www.3dcontentcentral.com/parts/browse/Robotic-Accessories/User-Library/140/185/185/Models.aspx?title=FIRST+Robotics&isredirect=true&level=10
These will help you get started with designing an actual robot.
If you have any questions, just pm me and I’ll be glad to help!
Thanks,
Adam
WOW! Those two links were exactly what I needed. I’ll post what I make shortly. Thank both of you guys so much!
The simplest 6 wheel drive to build is two traction wheels in the middle and omnis on the corners. No issues turning at all, but it can be pushed in a circle if its hit just right. we loved the maneuverability that this drive offered us this year.
Love to see what you come up with.
And before you start assuming that you have to make it out of metal…
also search the CD media photos for “wood” and “plywood”.
Or fibreglass (particularly what 842 does with it.)
Jason
This! Very this! I’ve been trying to convince a few team members to try a bamboo robot for a few years now…
How well does the fiberglass hold up? I have used it for other applications and it doesn’t see to be robust enough for FIRST, but then again neither does balsa, and I have seen those bots.
McMaster has CAD files of almost everything they sell, so if you find a bearing, bolt, sprocket, or widget that you like in their catalog, go ahead and download it!
Fiberglass holds up extremely well in a FIRST setting. Im not sure of any team who has used plain balsa for there robot. We use baltic birch plywood and it is incredibly strong and easy to work with
Pulturded fiberglass is beastly for FIRST. Main problem is it weighs a lot, but you can be shockingly liberal with lightening and it will still hold strong. 2791 used it this year to make a bumper frame for roughly 7 pounds. It’s great because you can machine them in any school wood shop, and pultruded fiberglass already has some convenient flanges for structure. 1726 has used it for a cantilevered dead axle 6wd before and it seemed to work for them; their bases are a little heavy but they don’t tip! I might make some pultruded fiberglass CAD now…
In many applications you may prefer bent aluminium though. We replaced a lot of square fiberglass tubing with kitbot c-channel and saved a lot of weight.
This post raised a very good point. The trend seems to be to make your base as lightweight as possible. The upsides to this are obvious but the major downside is that it may mean your CG is higher in the air. This doesn’t mean you want a 90lb drive train but is just meant as a warning to check where your CG will be. A good drive train is only useful when it has wheels on the ground.
Where does 1771 source its baltic birch? Is it a local supplier or is it online? Ive been wanting to price it out to see if some projects would be cheaper using wood. (Plus, they would look nice imho)
It is definitely cheaper than aluminum. We buy it from a local lumber yard and I believe its about $30 for a 5’x5’ sheet of 12mm ply. Be sure to get true baltic birch as there is some birch ply that uses softwood for the filler layers.
I hope you’re machining that wet…the dust is terrible for people and machine equipment.
We avoid breathing the stuff and end up replacing the blades and hole saws frequently. “Fiberglass burn” is a common ailment on the team 
Here’s what I’ve come up with, a 6 wheel drive, the two middle wheels are powered, the wheel on each corner is an omni wheel, even though this is just 1 side, you can see where I’m going with it.
You’ve all helped me so much already, so any comments/criticism/corrections/suggestions are welcomed!
Nice job, looks like your getting the idea. Your wheels may not actually the same size (6 in?) so you may need to offset the traction wheel by a bit.
How are your shafts powered? the omnies will be chained to the traction, right? Also how is the middle axle powered, keyway? I would suggest hex shafts like this one http://www.andymark.biz/am-0520.html No idea if it fits your gearbox, but I am certain you could find one on andymark.biz if those are toughboxes on the drivetrain.
This is definitely a good start. In addition to whats already been said, I have a couple more suggestions:
you should really try to push the omni wheels as far out as possible without compromising strength. This will improve stability front to back.
flip the plates or add fillets on the bottom as well. In my opinion its always better to have the bottom of the plate filleted to help it not catch on something.
If using material that thin definitely add flanges to the top and bottom to make it stiff enough.
Avoiding this is not good enough. PLEASE use a face mask and obviously goggles while cutting through fiberglass. Glass dust is not Good Eats.