So I’ve been looking around at the Robot in Three Days website and other sites trying to find an approximate rpm to run our collector. Does anyone know the rpm and or gear ratios they are using? I can’t tell by looking and their cad didn’t tell me much about the internal gearbox ratios.
Do the CADed gearboxes not have gears in them?
We finally got one spinning last night, wild guess around 1000 rpm. CIM and AM single stage gear box, with roughly 1:2 chain reduction.
seems to do the job. Further testing and refinement needed…
What gear box is it specifically?
Why not test prototypes yourselves? Just curious. Personally, I would think you’d find more accurate and applicable data.
this one…kit unit from the year before last year
I don’t think RPM is really what you want – the surface speed of the roller will determine how fast the collector sucks up the ball. 100 RPM on a 1" roller is very different than 100 RPM on a 100" roller. To convert RPM to ft/s of the roller surface, RPM/602pi*(radius in feet). I’m not exactly sure what ours spins at, but this is a great opportunity for critical thinking. Does it really make sense to have your collector spin at 20 ft/s? Do you expect to move the ball 20 ft in a second? If your roller starts slipping on the ball, you may pop it as some teams already have!
We’re aiming for around 1000 RPM with 5" wheels, then we’ll see how well it works and adjust from there. For our planned motor, we have 4:1, 8:1, 16:1 and 64:1 gearboxes on hand, plus a few sprockets to adjust the ratio between those numbers. There’s nothing wrong with making a few attempts to see what works and what doesn’t! And when you need to figure something out quickly, you can always prototype with a drill
We just put up a cad walk through of our intake roller system, it was running around 200 rpm.
Use your inner engineer and experiment yourself
You’ll have more fun (maybe a few more headaches) that way
A typical rule of thumb is to gear your intakes for a little bit higher of a surface speed than what your drivetrain is geared for. For example if you have geared your drivetrain for 10ft/s, aim for 11-12ft/s surface speed of your rollers. If you can’t do the math yourself JVN’s mechanical design calculator has an intake section that’s really useful.
There’s a logical reason for this rule of thumb. OP, take a guess?
Hint: it was explained in one of the videos.