-6WD center drop .125in
-inside rails 2.5in by .75in tubes
-outside rails same tubes but cut in half on table saw
-6in Baltic birch plywood wheels
-base plate 6mm Baltic birch plywood
-AM SS 5.78fs on high gear and 14.76fs on low
-uses #25 or #35 sprockets and chain
Feedback would be great cause it seems like this is the last version before manufacturing. So if any improvements can be made to the design it has to be as soon as possible.
The wheels are 24mm wide. Baltic birch plywood only comes in metric so we take 2 sheets of 12mm spread wood glue on them and sandwich together under a couple of batteries. Then drill a hole and turn them round on a lath. Really easy and is usually done by second day of build.
I have a question I’ve wondering about for a while.
It seems like lately I’ve seen a lot of CAD models for drivetrains including wood as material for them, and I was just wondering what the advantages are to this as opposed to using aluminum or some other material?
Is it cost or weight savings that is the main advantage? If someone could shed some light on the topic I’d appreciate it a lot.
Depends on who you’re asking… We realized last year that baltic birch plywood is an amazing material to build robots with because it is very easy to machine and also available locally (meaning we don’t have to wait around for materials, which has always killed our build in the past). From our experience the weight has been about the same with our wood frames compared to our other frames, but that wasn’t our deciding factor when choosing to use wood.
I like the use of wood wheels in this rendering, that’s something that we had been pondering for a while when we were in our drivetrain brainstorming frenzy last year. We never came up with a design that was fast and easy enough to build to make us choose custom wheels over more expensive store bought wheels, though. We are generally pretty lazy…
One other note on the design: I would think that bumper mounting would be easier if the side rails were oriented to make the outside edge of the robot flat (instead of having those flanges). Of course, if the bumper rules follow the trends of past few years then predicting bumper mounting criteria is but the dream of a madman.
I guess wood vs aluminum wheels or body really depends on team resources and what were used to. Our team has a local metal supermarket so we use aluminum for the body and mill using a Bridgeport digital readout mill. At school our tech department has an open CNC which technically could be used on aluminum and when we tried one summer it worked but took for ever and we decided it was not worth the time or effort. Wooden wheels are super easy to make and we’ve never thrown a tread or cracked a wheel according to our mentor. We’ve always made the wheels on a lath but this year since I’ve learned to CNC I’m going to try and make it on that so to cut our manufacturing time in half.
The flange on the outside is to space the bumper from the bolt heads holding the wheel shafts and Bosch extrusion
I’d be a bit worried about the front. I recall many teams having problems with bumper rules this year. And then there is the possibility of getting hit in a bad spot and bending one of the front forks.
One final question. How much clearance space do you have for the chain?
I’d make the front parts a bit wider or at least put a couple of angle supports in there. A couple of triangles or braces go a long ways in preventing bends.