One motor rd4b

Do you guys thing one v5 motor will hold up a rd4b with a cap intake, or would two motors be better?

It depends. You could do it quite easily I believe but the gear ratio you choose will play a big role.

2 will always be better, but with good bracing 1 will suffice

Also, i see that Md tag

this is also assuming that you use a gear ratio that can lift what you need

Ok thanks! if was thinking a torque motor with a 1:5

Maryland for the win!

1:5 torque would work perfectly with a 1m V5 DR4B. just make sure you brace properly

Yeah. As @NightsRosario said, you could totally go with a 1:5 ratio with one V5 motor(assuming this is 200rpm). You might even be able to go with a 1:3 ratio if your build quality is good enough and if the cap intake is light.

We had a three motor dr4b last year- little bit different but the concept is the same. Basically just stick the motor in the middle of a universal axle powering the dr4b and you’ll go up straight just fine.

you really don’t have to do that. with enough bracing just powering one side would suffice

I built a 1 motor dr4b that works with a torque 393. It doesn’t work with the high speed V5 though so I have to wait until vex ships the gears for motors.

Likely because the stall torque for the V5 isn’t that much higher than for the 393, nowhere close to the power output ratio that can be achieved. So running the 393 at 120 rpm v. running the V5 at 200 rpm more than makes up for the lower stall torque. With the set-up I think you’re describing, the 393 would require more than 30% more torque than the V5 to stall it. So you’re probably in that reasonably large region beyond what the 200 rpm V5 can handle and yet not straining the torque 393. Changing the V5 to 100 rpm should allow it to handle the lift noticeably better than the 393. Then the V5 would require 50% more torque to stall it than the torque 393 does.


I know that high torque V5 motors are 6:1 gear ratio what is the gear ratio in high torque 393’s?

The 100 RPM V5 gears are a 36:1 reduction, 200 RPM are 18:1 and the 600 RPM are 6:1. The “high torque” option is 36:1.

The gear reductions on the 393s are similar. I cannot remember where I heard it, but I’m pretty sure that the free RPM of the 393 motor is about 3,600, just like the V5 motor, which would mean the 100 RPM gears are 36:1.

I haven’t seen the free speed for the 393, so I can’t speak to that. But the available output speeds for the 393 are 120 rpm, 160 rpm, and 240 rpm. So if you’re right about that 3600 rpm, then they would be 30:1, 22.5:1, and 15:1.

The V5s have a noticeably bigger spread, which I expect we’ll find more useful. For example, using 600 rpm you only need one pair of external gears to reach 4200 rpm as opposed to the compound gears needed for a 393, even if it’s turbo.

Always thought the output speed of 393 (as shipped) is 100 rpm (and not 120 rpm)?

Hmm… I was going by this:

Seems VEX is disagreeing with itself. :frowning:

Lol. The vex virus strikes again.

Unless they have changed the specs for the newer 393, else I am quite sure it is 100 rpm. Coz all along the high speed gear is 1.6 times the speed, and turbo is 2.4 tImes the speed. Only possible if the initial speed is 100 rpm.

Ya the 120 figure comes from actual tests under no load. The motor has so much torque it is able to spin all the way up to 120 rpm. Tests with 393s actually show a variance in no load free speed from 105-120 rpm iirc. The tiniest amount of load drops it down to 100 rather quickly so motors dont always ship able to spin at 120 rpm.

The higher gear ratios spin fast enough that they have load from the metal gears that they only reach 100% not the equivalent 120% of their “top” speed.

That explains the difference!
Makes a lot of sense now.

But maybe vex should be more specific when putting down numbers.