pic: 35 MPH Prototype



This is the prototype we at Sparky 384 made using the 2 speed AndyMark Transmissions. The math said that it would go 45 MPH, but we only got it to around 35 MPH :frowning:

James! You know 6.5 isn’t street legal! Bad robot! Bad! Let’s hope our resource officer dosn’t find out abou this… :ahh: :stuck_out_tongue:

How did you measure/calculate/verify the actual speed. Also, it must have been kind of scary with that caster wheel huh? Also, what is the big tank for?

Shifting without a compressor ?! (reason for tank maybe)

I would be guessing that the big tank is the compressor for pneumatics. I can be wrong…

What was the output ratio from transmission output to wheel?

I calculated the theoretical top speed using the rpm and gear ratios in the transmissions. The big black tank is for the pneumatics to change gears. The tank is so big that we only filled it once for all the time we were playing with it. We didn’t officially clock it at 35 MPH, but we were guestimating. And as for the caster in front, at the beginning it was centered. That thing bounced around so much I couldn’t control it. But it was FUN!
The gear ratio in the transmission is 4.17:1 which is about 1247 rpm. Then it goes 1:1 from the transmission to the 12" wheel.

If the cims are turning 4379 then output at that ratio is 929.7 rpm, with a 12in tire, 48.68fps which is 33.1 mph (fps * .68) gets you mph. If you are getting more than 4379 out of the cims even faster. Way cool

The motor specs sheet I have been using has the CIM’s going at 5200 rpm. That’s what i’ve been basing my calculations on.

Whatever you do, don’t show that design to Swampthing :ahh: . Next thing you know, they’ll come up with a robot that goes 40+ miles/hour reliably. As if their robot wasn’t fast enough…

That is approximately the CIM motors free speed. The motors are operating under load, so the actual output RPM is going to be something far lower than that. Additionally, if you’re using the FIRST provided circuit breakers, the motors will draw more than 40A under load at a speed considerably lower than 5200 RPM, were they ever to go that fast.

If your robot were traveling 35 MPH, it’d be able to cross a football field in six seconds. Can it?

o man i thought the black tank was for the Nirtous Oxide…darnet that would have been cool :smiley:

We did have trouble tripping the breakers. The first time we tried it out we only had one CIM per gearbox, but we added two more. The road we tested on had a slight hill, so if we started off in first gear and shifted into second it did fine. As for the football field in 6 seconds, it would be close. I need to find a radar gun somewhere.
I admit that it isn’t practical and we wont use this setup on our robot next year (most likely), but it sure is fun.

Is it FIRST legal? I am assuming not because of the air tank you used.

Electric motors…nitrous oxide? They would get more power out of putting NOS stickers on their bot than actually putting a nitrous tank on it. Because all the NOS tank would do would be weigh down the bot :rolleyes:.

This looks like something I would want to do in the summer in my free time. Yay for using math calculations to figure out speed :stuck_out_tongue: We used the long equations mentioned so we could gear our robot for ~12-15 Ft/S this season :wink: But heck, 35 MPH is insane.

try a bigger battery, like 24 volts. That may change some stuff. Also you may want to impliment a cooling system if you haven’t already.

Hey some of our team members decided it would be funny to put NOS stickers on our robot, so we have NOS.

Really James, don’t let the resource officer find out about that,the speed limit on that road is 25 mph. You could get a ticket. Just think if you were given a speeding ticket for breaking the speed limit with a robot!

Or they could just open a large dump valve to spray the nitrous backwards, kinda like using a fire extinguisher to create propulsion, I mean, with a full tank, it’ll be some high compression there.

Or use it to fuel a rocket engine! Just a matter of heating the stuff right.

That would be cool, a 35mph bomb/rocket :eek:

Cooling system? With it being as open as it is and running at 30+ MPH, I think they should get enough air flow to sufficiently cool everything.