What Drive are you using For spin up

VEX V5 General Discussion
1

I made the polls wrong so the first one isn’t supposed to be an option its supposed to be the title :frowning:

  • RPMS
  • 100-200
  • 200-300
  • 300-400
  • 500-600
  • 601+
0 voters
  • Number of motors
  • 2
  • 4
  • 6
  • 8
  • Other Please elaborate
0 voters
  • Drive type
  • 2.75 inch tank
  • 2.75 inch x-drive
  • 3.25 omni tank
  • 3.25 omni x-drive
  • 4inch omni tank
  • 4inch omni X-drive
  • 2 inch mecanums
  • 4inch mecanums
  • Other Please elaborate
0 voters

Thought this would be fun to talk about thanks

5 Likes
2

I feel like I should explain what I am doing:

x-drive either 4 or 3.25 wheels. I said 4 because the speed from then drive is comparable to 3.25 wheels at 360 which is very nice. Because its an x drive that means 4 motors, but I do think at some point in the season I would like to make an asterisk drive maybe just for fun?

4 Likes
3

thinkin’ outside the box for this one…

7 Likes
4

I think rpm isn’t the best question if you are asking about drive trains, because x drives will have faster speeds for lower rpms, and small wheel sizes will reduce speeds. I think a fps/ips poll, a motor count poll, and a holonomic capability poll would be most fitting.

1 Like
5

I did rpms and wheel size because people use higher rpms on small wheels to co.pensate e t. Also X drives do t have as much rorque so I concept they are faster but in reality they are not as fast

6

Rpms and wheel size directly correlate, resulting in speed. I like your polls, but there is no way to tell how fast people will actually be driving. The 601+ rpm people might be using 2 inch mecanums, and the 100-200 rpm people might be using 4" mecanums in an X drive, or even 5" wheels. The output speed and forwards pushing power (motor count, X or tank) is what I’m interested in.

4 Likes
8

lol a 6m asterisk drive at the moment

9

4" omnis are actually 4.125", btw

10

Don’t you have to multiply the diameter of the wheels by pi for circumference?

2 Likes
11

Wow you are so right I messed up big time there. It should be exactly the same without it since every wheel would be multiplied by π so that doesn’t matter. I just can’t call it inches per minute anymore. I’ll change it to diameter by velocity or something. Dbv

1 Like
12

Revised version of the poll for terminology issues:

Let’s do this proportionally in a simple way that everyone can do easily: velocity by diameter (vbd). Multiply the rpm of your drive by the size of your wheel.

For example
280rpm × 4in wheels = 1120vbd

If you’re using an x - drive all you have to do is multiply your result by √2 because that’s how the math works on that (you can look up information about that if you’re interested).

A direct drive 4in x drive on green cartridges would be
200 × 4 × √2 = 1131vbd

There are more official ways of doing this but let’s try this out.

  • 200-500 vbd NOT RPM - READ
  • 501-800 vbd
  • 801-1100 vbd
  • 1101-1400 vbd
  • 1401-1700 vbd
  • 1701-2000 vbd
  • 2001-2300 vbd
  • 2301-2600 vbd
  • 2601-2900 vbd
  • 2901+ vbd
0 voters
5 Likes
13

Early season, till November or December I’m just planning to use a 200 rpm direct-drive, 3.25 inch, 45deg x-drive. That’ll let me focus on intake, indexer, and flywheel for that time period.

919.23 VBD (equivalent to a 229 rpm 4" tank drive)

1 Like
14

I like the idea of using a unit that equates to drive velocity… but you could also just use drive velocity: in/s or cm/s

5 Likes
15

I personally like the VBD idea better because 800 VBD (4" 200rpm tank) is a lot better looking than 2513.27 in/min or 41.887 in/s. Pi is annoying (for x-drive sqrt 2 is annoying anyway sadly)

3 Likes
16

I really hope this notion does not catch on.

Converting 800 >random unit name here< to 42"/sec requires very little effort and results in a number you can visualize in design. If I see 42"/sec I can easily imagine a bot that crosses the field in about 3 seconds.

The only way 800 >random unit name here< does that is if I memorize the conversion to actual drive velocity.

8 Likes
17

For those who don’t know how to calculate ft/second, here’s an RPM calculator.

And here’s a new poll:

Drivetrain Velocity? (feet per second)
  • 0.87 or less
  • 0.87 - 2.18 ft/s
  • 2.18 - 4.8 ft/s
  • 4.8 - 7.42 ft.s
  • 7.42 - 8.73 ft/s
  • 8.73 - 10 ft/s
  • 10 - 11.34 ft/s
  • 11.34 - 12.65 ft/s
  • 12.65+ ft/s
0 voters
2 Likes
18

Thanks for the ft/sec list. Just want to point out that 600 rpm 2.75 drive base (which I think is the fastest used in TiP) is 7.20 ft/sec. Not sure that the high end of your list is practical.

Edit: I made a sheet that can be used to find VRC drive velocities. Make a copy to have control of the drop down lists. Be aware that some gear ratios and wheel sizes are impractical or impossible to build.

2 Likes
19

You can calculate drive speed in inches per second by multiplying the wheel diameter by 3.14, dividing it by 60, and multiplying it by the drive rpm. To convert this to ft. per second, simply divide the whole thing by 12.
I’m doing 4 motor drive at 360 rpm on 3.35 tank omnis. The drive speed is 5.1 ft/sec.

1 Like
20

So i have a question, how do you calculate the rpm?

21

you multiply the motor rpm by the number of teeth in the driving gear, and divide it by the number of teeth on the driven gear.

2 Likes