X-Drive for Spin Up, and Gear Ratios?

Hi, what does everyone think about using x-drive for this years VEX VRC Spin-Up game? We’re new to VRC, but we think x drive could work due to its manoeuvrability and sqrt2x speed, and we’ve had experience in building different drivebases, although that was IQ. So do you think we can pull it off for this season, or at least CAD it out and give it a try? Or should we stick to the usual H-drive or tank drive for spin up? I know that strafing can be useful for discsIn terms of gear ratios we were also thinking 4m x drive 233rpm (100rpm cartridge on an external 7:3 geared up ratio) on each 4’ omni wheel. Please let us know if this is a good gear ratio but also when/if the motors will burn out, as our driver can handle high speeds. Thanks. Btw we aren’t 21549E anymore (that was our iq reg.) , but our VRC team number hasnt been decided yet, and i dont think i can change the username lol

Or you could use 600RPM 3:7 ratio with 3.25" omnis.

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Keep In mind the xdrive Has less torque by the same factor also I would gear a 600rpm down 3:7 for 257rpm if ur using 4inch omnis. Or gear a 200rpm up 60:84 for 280 rpm


PM a moderator and they would be happy to change it for you :slight_smile:


Personally I wouldn’t use it, I’m building tank rn because more power and less pushing.

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if you have an x drive, its easier to get pushed around, and you have less torque overall. teams will make x drives work for spin up, but you need building experience to make a high quality (aka functioning) X-Drive, and you need an experienced driver in order to take advantage of strafing. if you dont use your strafing very much, there isn’t much point in going X-Drive

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I think a 280rpm might be good with 3.25 omnis, and i’ve seen a few 257rpm 3.25 omnis too yes, but my only concern was that the gear ratio would probably have to be vertical to maintain weight balance, raising the mechs on the robot onto a platform? Which led me to think about 200rpm direct drive with 4’ omnis…

Thanks! I’ll definitely keep that in mind and tell the driver. He’s been driving for 2 years now but we’ll take advantage of the strafing.

Yep, I’ll do that. Thanks!

Edit: Actually I’ll have to wait for our VRC team number to be decided, thanks!

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I thought that x drive would be better for strafing and manoeuvrability, and maybe torque/power wouldn’t be the meta of this game, although yes you would need some pushing power of course.

Use a 200 rpm X-drive on 4 inch wheels imo, because X drives are sqrt(2) times faster and output 1/sqrt(2) less force. So, a 200 rpm drive would translate to the same speed and force of around a 280 rpm drive.


Hi, thanks for sharing your thoughts. I think this is probably a good idea, as that would equate to 4.94 ft/s (minus a bit because of weight/acceleration). Would that be fast and powerful enough for a competitive robot?

Yes, many teams last year and the year before ran 280 rpm.

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Sorry, would that be 280rpm in terms of tank drive, ie 200rpm on each 4’ wheel x-drive as Roboter said?

280rpm tank drives were pretty common.

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Yes. 280 rpm on 4" wheels in an x-drive will be way too fast.


Yes, a 200 rpm X drive will have the speed and torque of a 280 rpm X Drive. As for speed comparisons, I would suggest you refer to the table below (all are tank drive calculations).


If you want to convert from tank to the speeds and forces of holonomic drives, refer to the table below (Omni is X Drive).


I’m confused. Wouldn’t an X-drive be slower than a tank drive with the same rpm and wheel size? With an offset of 45° wouldn’t they have to travel sqrt(2) times the distance, therefore making it sqrt(2) times slower?


Here’s a great explanation on why X drives are faster:


Basically, the idea is that the X drive’s net speed is higher because it is going forward while strafing, so it’s net displacement over time is higher (someone correct me if I’m wrong).


Thank you! That cleared it up.