I am interested to find out what most teams cruizin speed/gear ratio is. I thnk this would be helpful to most other teams trying to build a transmission. Thanks in advance for the responce.
We top off at about 14 feet per second with a gear ratio of 4-1(to get more complicated it’s, 60:24:12)
Our robot cruises at about 7 fps. I don’t know the gear ratio. This was our fastest bot. Others can match @ top speed.
p.s. what is up with the name stealing? j/k
We have a theoretical top speed of 9.4 fps. We run on drills and Chias. The Chias are geared down to match the speed of the drills (in low gear), then the drills are geared down 12/32 to the 12.5" diameter wheels.
Team 188 has a low speed of 4 fps and top speed of 17 fps.
We ran a test witha mostly full battery and we are at about 11 fps
Our robot’s original top speed was 15 fps.
It’s now down to around 9.5 fps.
Cory
high gear 15 forward 300 RPM
low gear 9-9.5 forward 231 RPM
well…I have run a mile in 4:30:)
our bot goes 11.9 ft. per second on high gear… and 3.4 feet per sec…
here are some specifications of the tranny…
**Gear Ratio: **
**High Gear = Output/Input **
59.1 drill
17.5 atwood
Low Gear = Output/Input
206.8 drill
61.1 atwood
*Torque(tranny)=Torque(motors)Gear Ratio * Efficiency of Gearbox
T(in lb) 3172 low gear
T(in lb) 906 high gear
our robot (cims and drills), goes 9.5 ft/s…i believe the ratio is 4:1…
Yeah we tried doing some theoretical calculations, but thoes we wrong. Holonomic was unpredictable to say the least.
Are you sure you did your torque calculations right?
3172 inch-lbs is as much torque as some cars have. I don’t think your bot has as much torque as a car (That would be pretty cool though, wouldn’t it :))
Cory
the torque title says “efficiency of the gearbox” the calculation was done right… it was checked by 3 engineers… so the transmission itself has torque of 3172… but i dont believe our robot has that much torque… if we did then we would be pushing around almost every single bot… 
dont know the gear ratio but we make it from one side of the feild to the other in 6 seconds of less
Isn’t the ratio useless without knowing the wheel diameter?
The calculation does appear to be correct, just go to http://www.usfirst.org/robotics/2004/specsheets.htm and try the calculations yourself.
Our top speed this year was about 8 ft/sec. However, we were a little underpowered with only the two bosch motors for drive.
Actually, Blizzard 5 (that’s our robot…) outputs 500.6 lb-ft (6007 lb-in) at the drive wheels in low, and 116.4 lb-ft (1397 lb-in) in high–though that’s before factoring in the estimated 86% efficiency–so let’s call it 5166 and 1201 lb-in, respectively. Given that it’s using the Fisher-Price motors in addition to the Bosch and CIM motors used by mechman108’s robot, and given that its torque was calculated using a similar method, it looks about right. (Also note that these are stall torque ratings–the robot would most definitely not like being stalled for very long. 670 A will do that to you.)
A car’s torque rating is measured at the crankshaft–but with a multi-motor drivetrain in a robot, there’s no equivalent. So we measure torque at the drive wheels. The true test of car vs. robot involves factoring in whatever gear ratios exist in the car’s transmission and differential, and comparing those figures.
Incidentally, like Steve said, we do 3.8 ft/s in low, and 16.5 ft/s in high (with 8.5" diameter wheels).
Both these torque ratings are impractical because they are torques at stall and when 2 CIMs and 2 Drills stall the current draw is over 450A with each drawing 100A so it would be a very short time before several fuses blow. Add two FPs and getting to stall torque is even less possible. It would be more appropriate to list the torque at realistic currents like 40A per motor. Torque is basically proportional current so that is about 1/3 the torque listed for each of those robots. Supposing they could be at stall for more than a very short time, something would surely give to lower the torque very quickly, be it wheels slipping or the finger of the poor kid who got to close to the chain.
The fact that these are ratings at stall is another reason that they are incomparable with cars because internal combustion engines usually have max torque at higher speeds (at their highest speed?).
Edit:
interesting little calculation: 500.6lb/ft on 12 inch wheels yields a force of 1001.2 lb per side. This would require wheels with a coefficient of friction of (1001.2)*2/130 = 15.4 to harness that power. The highest CoF i have seen in any context is like 3 or 4