Crazy drivetrain idea

[lukevanoort]

Do you guys (and gals) think its possible to use rotary actuators in a drivetrain? Maybe with a rachet system to keep it from draining the drivetrain. It could be used like a nitrous switch to boost up the power temporairly. It would be excellent for a burst of torque when accelerating or in a pushing match. Then again, I could be completly wrong, since I do nothing with pneumatics.

[greencactus3]

i htink the tanks we are allowed to store air in wont hold enough air to actually be useful. another motor would probably be a more efficient way to do it. to actually have a burst of torque, you'd need a lot of air. and one small jerk isnt gonna help at all except freak out your driver. but an interesting idea. a simpler (although not lightweight way) would be to have a large/heavy flywheel spinning and just keeping that stored energy till you need it when it engages a clutch and you suddenly have a lot more power.... for a bit. depending on how much rotational inertia you store.

[Bcahn836]

And for something like that to be run for and period of time would require the compressor to run constantly which would drain the battery quicker.

[lukevanoort]

Well it wouldn't have to last long. 587 is a defensive team, and we're thinking about a three speed six motor drivetrain. That'll probably happen in '07 though. A three second burst of torque would greatly help. We might not even need to recharge the tanks and do it as a one shot.

[greencactus3]

Originally Posted by lukevanoort

Well it wouldn't have to last long. 587 is a defensive team, and we're thinking about a three speed six motor drivetrain. That'll probably happen in '07 though. A three second burst of torque would greatly help. We might not even need to recharge the tanks and do it as a one shot.

i kinda have the feeling you arent gonna get 3 seconds if you want a burst of torque...

[Cory]

Originally Posted by lukevanoort

Well it wouldn't have to last long. 587 is a defensive team, and we're thinking about a three speed six motor drivetrain. That'll probably happen in '07 though. A three second burst of torque would greatly help. We might not even need to recharge the tanks and do it as a one shot.

Don't bother.

With a 3 speed, 6 motor drivetrain, you'll break traction long before you have a chance to approach your maximum torque output.

[Elgin Clock]

Ya know. I love these threads that say "crazy something or other idea" cause they always give me a crazy idea for a robot design..

This thread has not broken that trend.

Thanks a lot. hehehe.

[Tristan Lall]

The rotary actuators from last year were the Bimba PT-017090, which have a torque rating of 10.2 inch pounds at 60 psi. (See here, page 3, for calculations.) By contrast, the CIM motor is rated at 21.8 inch pounds, at stall (or half of that at maximum power).

The trouble is, neither of those represents enough torque to drive the robot. Of course, we trade speed for torque by gearing the CIMs down so that one rotation of the motor causes only a fraction of a rotation of the wheel—but if we do the same to the rotary actuator, its 90° travel will become problematic! That is, 90° at the rotary actuator might easily become less than 10° at the wheels, depending on how much gearing is necessary to multiply the torque so that you output a useful amount. So you have a useful boost in torque over a very small distance. Depending on the speed of this rotation, you'll very likely end up with much less than 3 seconds of boost; probably more like 0.3.

If you wanted to leave the rotary actuator as-is, and not gear it, that might work, but the additional torque would be negligible, compared to what it takes to drive the robot. You would, however, retain the 90° travel.

You also have the added problem of disengaging the rotary actuator before the motors drive it into the hard stops, destroying the rack and/or pinion.

There's one (worthless) bonus to this: you'll have lots of air left in the tanks, because the actuator itself is rather small.

So, in general, I'm with Cory et. al; give a 2- or 3-speed a shot, with four to six motors, if you're absolutely set on building a defensive robot. Theoretically, Blizzard 5 (Woburn's 2004 six-motor, 2-speed robot) would have broken the wheels loose at 22% power in low gear, or 95% power in high gear, while pushing a nearly-immovable object at its limit of traction; this sort of performance should meet your needs. On the other hand, consider not limiting yourselves to defence—maybe the start of the 2006 season would be a better time to decide on a strategy.