We’re trying to move away from 4in direct drive drivetrains for next year, so I created this demo frame. any suggestions for how to improve it? the longest c channel size we have is 12.5 in, which is what I used here.
also, other than one ones listed in the catalogue of drive gearings, are there any gearing options you would recommend that don’t use the blue cartridge motors (we don’t have many of those), particularly setups without a center traction wheel?
There really aren’t many viable gearings outside that catalogue unless you have a compound ratio. As for recommendations, I would say use a c-channel instead of that rail piece you have in the back, attach the middle c-channel underneath the sides, not in the middle of them. Also use standoffs on the edges of the sides instead of a screw.
Other than that just make sure you use screw joints and I would use aluminum, not steel. Also use nylocks, rarely use keeps nuts, otherwise they could fall off in a match or in hard to reach places. Good luck!
for the 1st recommendation, I know that’s better, but… we kinda can’t (same issue I mentioned before, 12.5 in is the longest c-channel we have, and I thought this would be the next best thing). we also don’t have much aluminum so I’d rather use it for other components; at least the steel will lower the cg when it’s on the drivetrain. also, can you explain what you mean by using standoffs instead of a screw on the sides?
At the front and back ends of your drivetrain you have a screw holding the two sides together.
I’m not sure if that’s for a screw joints based on the bearings but to provide more stability, you can attach the two halves of your sides (the metal surrounding the wheels) with two standoffs per side.
Those are screw joints. Given that this drivetrain is already pretty short, I’m not sure how many options are available that would fit standoffs as well (I’m planning to use this as sort of a “template” for future teams to base their drivetrains off of, so ideally it works with as many different options as possible). Thanks for the suggestion though!
firstly I believe you are using steel, although yes, your drive base is supposed to be strong, its really does not need to be that strong to use steel, and it will add a ton of weight to your bot.
We don’t have much aluminum. I think I will ask our mentor to buy longer aluminum c-channel though since it seems like we’ll need it.
update- I found some options for 4in wheels that seem viable, and are pretty easy to build as well. These aren’t in the drivetrain catalogue (technically the 1st one is, but its set up way worse), so I thought I’d post them here.
Your second design will not work; you need an odd number of gears in between.
Each gear spins in the opposite direction of its neighbors
You’re right, I forgot about that. It should still work though, it’ll just be shorter with one less gear.
If you’re not doing complex autonomous routines you could consider using sprockets and chain. Just make sure the chain isn’t exposed and breakage shouldn’t be an issue. Every year several of my sister teams, and even my team my freshman year, successfully compete with chain drivetrains.
You would have to find a way to cram another gear in the drivetrain and make a gear differential. There are a lot of ways to do this, most of which involve stacking c channel to fit more gears above the drivetrain.
That depends. Unless your drivetrain is completely solid and you could throw it against a wall without it shifting, a chain drive will definitely break a lot. One of my sister teams had a chain drive and it broke almost every match. Especially at high speeds, chain can bunch up and snap. Gears are better in most circumstances, I’d say.
I know some options use a single raised gear (I wouldn’t create a whole row, that’s unnecessary complicated for a gearing that isn’t that great anyways), but I’m not sure how teams make them work. I’d think you would run into gear slipping issues, but clearly there is some way to avoid this.
Not a differential, it’s a ratio. Good idea, though
Yeah. It was just a visual. I would never make that drivetrain either.
Why don’t you use smaller size wheels?
One gear ratio one of my sister teams uses is a 84 to 60 280 rpm drive on 4 inch wheels. It is a little faster than direct drive, and 84 tooth gears and 60 tooth gears are pretty common. It isn’t as fast as a lot of the drivetrains used by advanced teams, but it is faster than direct 200. It also works well with 6 wheel drive. I don’t know if it would fit on your frame, though.
We don’t have many smaller wheels, so some teams will have to use the 4in ones
