VEX V5 Dragster

Hello, for my engineering class, we are making racing dragsters. We have two green motors and 3D-printed parts are allowed. There are no turns in the course, only a straight drag race. What is the ideal way to do this with gears? Should my group do a ratio that works for both acceleration and speed or is it possible to make a gearbox?

Welcome to the forums!

I think ideally for a drag race you would do an “all speed; no torque” gear ratio. A great resource would be “Catalogue of Drive Gearings

Obviously this is geared towards competition robots and many of these designs utilize blue motors, but I think you could make it work. For speed, I think it would be extremely helpful to maximize your speed (which you can calculate in in/sec) through a) reducing friction (bearing flats), b) finding a gear ratio geared towards speed, and c) ensuring that your dragster is as light as possible.

I hope this helps!

The electric motors should provide great performance but a gearbox may earn you points for creativity. There are a number of threads on transmissions here: Search results for 'transmission' - VEX Forum

I would add that you would want the robot to be as light and aerodynamic as possible. Use that 3d printer instead of big metal parts. Gear up those motors and use smaller wheels, preferably traction, not omni. I hope you do well in your race!

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dont use omni wheels and make use of 3d printer

lot of good stuff on this thread

I would recommend using the motors exclusively for speed. If it is allowed, I would use rubber bands connected to the drivetrain as an initial acceleration when the race starts. It will be a obe use per race, but on a short track, it can provide a massive advantage.

An interesting fact I heard from a friend, though have not confirmed the truth of, is
“Drag race engines are only designed to work for 6 seconds”
which makes a lot of sense, because they do not have to have any functionality beyond those 6 seconds, so using that, you might be able to design something that instead of a typical design will be specifically designed to do one thing very well.

if only one part of the dragster needs to cross the finish line, then make a string launher to shoot at finish line

Good tip on the rubber bands if you can use them.

Also:

  1. carefully inspect bearings
  2. polish your bearings and shafts
  3. if permitted, machine down the wheels so they are lighter weight
  4. cut down rotational mass (see #3) as much as possible
  5. could do a 2 speed transmission with auto shifting gearbox after X time/distance covered
  6. this project SCREAMS for the need to gather, compare, graph motor amps, rpm, etc… you want to shift to gear #2 when you see motor load drop off (this means max rpm has been reached, or close to it)
  7. get rid of weight everywhere you can. this means sanding, grinding, etc structural parts so they are as light as possible