Tank Treads?

[reversed_rocker]

We were thinking of making tank treads to drive our tshirt cannon as an off season project, does anyone have any experience with this? We just wanted to see different ideas and how they worked for other teams

[AndyB]

The problem you may encounter is turning ability. It would be smart to take this into consideration when designing your chassis.

If this Tshirt cannon bot will be driven outdoors on the grass and dirt of a football field, you'll probably want something more than the belting you may have seen used on FRC robots. I'd recommend snowblower treads. I know 171 used them on their 2002 robot and they worked perfectly fine.

You'll want to make sure the belts are well tensioned and take lateral slip into account (making sure they don't jump their pulleys).

[swamp_child]

Take a look at some old 180 bots, they've been using tank treads for a long time.

[R.C.]

Originally Posted by swamp_child

Take a look at some old 180 bots, they've been using tank treads for a long time.

Or aim or pm one of the members and i'm sure they would love to help you out.

[artdutra04]

Originally Posted by reversed_rocker

We were thinking of making tank treads to drive our tshirt cannon as an off season project, does anyone have any experience with this? We just wanted to see different ideas and how they worked for other teams

Do you want to drive it offroad, or just want to have tank treads for the cool factor? I ask, because whether or not you want to drive it offroad will affect a lot of design considerations. (Dirt, rocks, water, mud and temperature fluctuations would now be design considerations, and the surface friction is much higher)

If you are sticking to mostly indoor or asphalt/concrete surfaces, something along the lines of Brecoflex belts may be a good idea. The one downside is that they are expensive.

For our offroad promotional air cannon robot, we used a kid sled-size snowmobile tread cut down the middle. We had to use some kind of tread with "teeth", as one of the design goals here was to use something that can drive through snow. The advantage (and problem) with using snowmobile treads is that they are very stiff; meaning you will lose a lot of mechanical power just making them spin. On the other hand, they are impossible to detrack without disassembling the bogies. To power these treads, we designed custom six-tooth sheet metal and Delrin sprockets because the only stock ones available are four-tooth sprockets. These are insanely small, and require an unbelievably high amount of tension to wrap the snowmobile tread around something this small. This would rule out all but an ICE for powering the drive train without breaking the budget

Combine these treads with having lead acid 12v 18Ah batteries onboard (11.1v 10Ah LiPo batteries are ~$300 versus about $40 for 12v 18Ah Lead-Acid), an air compressor for shooting, and quite a large onboard sound system (this draws a lot of power - about 160 Watts - being constantly on!). Added up, this results in a drivable maximum range of about 200 yards, or about an hour of just playing music while firing off a few shots every now and then.

[Billfred]

If you're looking at off-road ability, you might also consider wheels. 1293 modified their 2005 robot--based off the kitbot of the day--to accept the pneumatic wheels from the 2004 kit of parts to allow it to run under power in parades. (Well, except when that set screw backed out with in the Irmo Okra Strut Parade--with the bubble blower and extra batteries added, that was probably close to 200 pounds to push.) It wasn't hard to do, and was plenty capable of running on grass, bricks, asphalt, and most anything else that was roughly level.

Of course, treads have their own appeal...but I'd at least consider wheels as an alternative.

[Beener]

How about something like this.

[Billfred]

That can't be something that anyone affiliated with 148 put together--the shape around the air tank only appears to have eight sides.