Robot Drive problem

I’ve been having some problems getting my new design to work

I’m using 2 motors, one on each side, with a 60:12 ratio powering the vexplorer wheels, dont have 4 of the all purpose or knobby.

I send power to it and the motors engage, but it doesnt turn the wheels hardly at all. I lift the robot up and try, and they start spinning normally

Any idea what the problem is?

here’s a video
Explore Jut Jut

the gear ratio is too high. the motors can’t generate enough torque to push the robot. try lowering the gear ratio

yes octane is correct

try a 1:3 or 1:2 gear ratio

im assuming there might be a screeching noise coming from the motors?

for more info on gear ratios read the inventors guide (if you dont have the starter kit (vex red) then you can download it from this site_)

would the 60:12 ratio work if i put 4 motors on?

i did this with my school robot and we had the 60:12 ratio, although with 2 motors it quit moving after the first minute of each match…

That would indicate Motors Over-Heating…

60:12 is 5:1.

You could try adding another Motor to each “side”, that would help out with the steep Gear Ratio.

thats what i meant

I’d like to point out tht it’s the other way around
Gear ratios are expressed as torque:speed
So it’s ideal to hav a higher gear ratio if the robot doesn’t have enough torque

no, gear ratios go like this: when you say a higher gear ratio, that means an increase in speed:decrease in torque. lower means a gear ratio that has a reduction, generating more torque, less speed.

oh yeah and one more thing…
i tried this a long time ago (about a year) and i had a 1:7 gear ratio(84 to 12) and drove it with 4 motors. i used the all purpose tires. it drove pretty fast, and for a good amount (about 10 minutes continuously) and the motors got very warm. i just don’t understand how my vex could do it and yours couldn’t. maybe i got lucky

adding another motor on each side should work, but I would also give the 24:12 gear ratio a try.

ratios r just like fractions
which means tht it’ll be the increase in torque (since we’re only talking in positive terms)
the greater the a value (torque), the greater the ratio
the smaller the b value (speed), the greater the ratio
thus, greater the speed, the lower the ratio

try lookin at the vex manual
Section 3, Page 5 of the Vex Manual (Motion Section)

a 24:12 ratio? wait…i never knew there was a 24 tooth gear for vex?

Just the 24t wormwheel, which won’t mesh with the 12t gear.

  • Dean

yep, 24 to 12 doesn’t mesh as 24 is slanted to fit worm gear…

the 12 tooth commonly comes loose doing 60 to 12 along with not enough torque to move.

yet still I attempt to do 84 to 12 :smiley:

maybe the metal 12-tooth will not slip as much; I think the teeth on the metal 12 will be pointed unlike the current rounded plastic 12 teeth.

think of it as a bicycle. when you go up hills, they say to put it in a lower gear(so it is easier, which is like a reduction.) when you want speed, put it in a higher gear (more speed, is harder to turn pedals). so a higher gear is harder for the motors to turn the wheels, making it faster, and lower makes more torque, slower speed.

Sorry, I was thinking of the 36 tooth gear, which might work for what you are trying to do. As previously stated, the 24 tooth worm wheel would be useless for that…

EDIT: it’s technically 12:84, but that’s not important.

This isn’t necessarily related, but I got 84:12 to work fine for me here, maybe this will help you

However, the bicycle gear shift’s numbers are based on the reciprocals of the gear ratios in order from 1~however many choices u hav
Thus a “lower” gear on a bicycle is technically higher gearing (gear and gearing r 2 different terms)

ok, so as soon as i can get a programming kit or Y-cables ill try the 4 motor configuration. thanks

and Royhdu,

all you’ve contributed to this thread is saying that we’re wrong about ratios. Please stop posting in this thread unless you have something useful to say.

Did you verify that what Royhdu was saying is incorrect?

Royhdu is trying to be helpful by providing Correct Terminology, so that we all can converse intelligently with other “engineers” about Gear Ratios. It is ALL about Education…