RD4B Gearing

Our team is building a RD4B lift with 2 motors, and we were wondering what the most efficient gearing would be. Obviously, we want both speed and reliability. Would you recommend a 1:5 ratio with torque motors, or a 1:7 with speed?

I haven’t tried a two DR4B lift with two motors, but I do know that 1:7 is very slow. I am using 1:5 ratio. It is fast, but like I said I haven’t tried it so, it may not be reliable.

@fruitarian I might be misinterpreting your answer, but I meant to ask specifically if a higher external gear ratio externally (1:7 w/ speed motors) or a higher internal gear ratio eternally (1:5 w/ torque motors) is better.

Two speed motors on a DR4B, might not be a very good idea, because the motors will burn out in maybe a couple days or weeks.

don’t use speeds! they are exetremely weak, even in a 1:7 ratio

i have a 2 motor 1:7 torque 2 tower double reverse 4 bar. Make sure to add a lot elastics. Mine goes pretty fast and 13 cones high

Depends on build quality and dedication. I’ve made a 1:5 speed with 2 motors that worked very well. Many teams have done the same thing (albeit, probably with more motors). Just make sure the build quality is good and you have a decent amount of elastics and you are fine.

still, a 1:3 ratio with normal motors, is about as fast as 1:5 with speed, but stronger.

please tell me this is a joke

thats not how gear ratios work, a 1:3 ratio has 3x the torque of a normal motor, so lets say a you get a total of 6 power. while going slightly faster than a 1:5 ratio, with speed motors that puts you at 1.4:5 X2 so you end up with 7.1428 power, slower than a 1:3 ratio, but with more power. I personally have used as little as 2 motor turbos in a 1:5 orientation, but with very little weight on the lift. This thread is full of misconceptions, such as not using speed motors. Speed motors are only slightly weaker than torque motors and should be used (as long as your not lifting the mobile goal). However this all depends on your build quality, and if you have poor build quality your going to have a rough time getting faster and better. Plus, you should always use rubber bands to make your lift essentially weigh zero, so your motors are only pushing around the weight of the cone+the metal on the rd4b.

nope, its true. try it! it is slightly stronger. not by much, but still…

no, this is false in every way shape and form, mathematically even with 100% efficiency (Not possible btw) cannot POSSIBLY be any stronger. You need to fact check before you go misleading teams into wondering why their gear ratio inst working and why their motors aren’t working.

thats odd. I tested it last year, I was expirementing with gear ratios. maybe one of my motors was acting up?

think about it, you must of had something like that, because theres 0% chance that that is stronger at all.
thats how gear ratios work, the more speed you put out, the less torque you have. Meaning the faster you are the weaker you are.

yeah, your right… It doesn’t make any scence, so It must’ve been. my mistake.

Yes, this is the ratio is recommended, because the cones only weigh 180 grams, which is extremely light.

this has been proven false by my earlier math

generally, while in this scenario there i generally no difference, i would go with a 1:5 with speed motors, as they work well, and if you have good build quality and balance your lift with elastics, you should be fine. But, if your doing something like a 1:3 to 1:3 compounded with speed motors, this is when you should change, because those extra gears add alot of friction, while changing out the internals on a motor doesn’t remove or add any friction

You don’t need to “experiment” with gear ratios. You can literally calculate the gear ratio and see which is faster, look at the reduction ratio for speed motors, torque motors (which you can classify as 1:1), and turbo motors.


Common external gear numbers used are 1, 3, 5, and 7. These are based off of the 12, 36, 60, and 84 tooth gears, but all simplify to 1, 3, 5, and 7.
Internally (inside the motor) we have three options. Torque gears (come standard), High Speed, and Turbo. Think of torque as 1, high speed as 1.6 times faster, and turbo as 2.4 times faster.

You can calculate the torque or speed of any vex part now, as torque is inversely proportionate to speed. For example, a 12 tooth gear driving a 36 tooth gear results in 3 times the torque output, but 1/3 the speed. The same applies when using high speed, the output is 1.6 times faster, but has 0.625 times the torque.

Edited for a typo.

Lol I’d love to see a 1:3 ratio for a 2 motor lift.

Pretty sure 21S had two motors on 1:3 at Poway, but I’d have to double check. @spurflys @spurflies