I was looking into drivetrains and came across the 450 rpm drive and was wondering if I did it with 4 motors would the motors overheat quickly, the 450 rpm is motor in tensive so i’m worried that it might overheat, I would test this but i can only test it at school which is over a month away. Any thoughts?
This depends on what size wheels. with 2.75" wheels you could probably get away with it, depends how gameplay will be this season (I’ve been ootl, I don’t know that much about this season yet). You will probably have some slight issues with overheating but probably nothing crazy. 3.25" wheels is pushing it even for 6 motors, and I wouldn’t do it on 4" wheels with 6, or maybe even 8 motors.
Thanks for the relplies anyone else have any-other thoughts?
Why are you running 4 motor drive? 6 motor drive is an easy choice this year (imo)
I dont have access to pneumatics but if i did i would have ran 6 motor
General rule of thumb is that for every 11 Watts of power you add, you should add 10-15 in/sec to your speed range. So for. 4m drive you should run 40-60 in/sec.
Formula for speed is
RPM x 3.14 x wheel diameter(in) / 60 = speed (in/sec)
Do some algebra and you get
Wheel diameter (in) = speed (in/sec) x 60 / (RPM x 3.14)
Simply to get
Wheel diameter (in) = speed (in/sec) x 0.0425
Now plug in values of 40 and 60 in/second to find reasonable wheel sizes.
I find a maximum wheel diameter of 2.55 in/s and a minimum of 1.70 in/ sec.
In conclusion, if you want to run 450, use 2 inch wheels. However, word of warning, the 48 tooth gears used to achieve 450 rpm are about 1.9 inches in diameter so depending on robot weight and number of wheels, you may find your gears sinking into the tiles (bad).
would much change if i used 2.75 in wheels? Would the gears be more prone to sinking into the tiles @9MotorGang
They would have no chance of sinking in the tiles.
Your increasing wheel size, not decreasing wheel size.
(A lot of top teams run 450 on 2.75 btw so there aren’t gonna be any issues with the gear ratio itself)
Ok, thanks for the reply sorry if my questions are stupid but I am very new to gear ratios, I think the only thing I need to worry about is motor overheating which shouldn’t be too bad
Yes. You would be outside the speed range I recommended. You would have less torque than 600 direct on 2.75 inch wheels and would almost certainly have overheating issues and slow acceleration unless your robot was very light (which is unlikely given that you are building g other mechanisms requiring 4 motors)
The reason the gears can sink into the tiles is because 2 inch wheels are only slightly larger 48 tooth gears. After having the chance to compare 2in wheels and 48 tooth gears I would almost grantee they will sink at least somewhat.
4m drive doesn’t have as many effective ratios as 6m drive and I would not recommend it. However, if you are going to use 4 motor drive I would recommend ditching the preconceived notion of using 450 rpm for 4m drive. I would recommend doing some research of drivebases teams ran in change up and tower takeover (the most recent games where 4 motor drive was meta). There are many acceptable ratios on 4m drive such as 257 on 4 in, and 333 on 3.25 to name a few.
Would 360 rpm 3.25 work or even 360 2.75
Also i would run 6 motor but teacher wont give us pneumatics
It not even possible on 4" unless you do some wild cantilever thing
I would recommend doing what I described in the first post. Calculate the linear speed.
I still think you could manage 6 motor drive with no pneumatics. I would recommend looking at designs from prior seasons without pneumatics as teams were able to do some very impressive motor sharing thing.
If you dont want to use 6 motors for drive, but you still want some torque, you can run a 5 motor drive. Look at 9364C Haunted robot design. They gear down 5.5 watt motors using a 3:1 ratio. I still wouldnt recommend running less than 6 motors on 450 rpm. There are still some competitive speeds for this year like 400 rpm, or 360. Look into them. Personally, 5 motor, 400 rpm drive is a solid pick.
I wouldn’t recommend running a 5 motor drive. It’s so complicated for no reason. 6 motor drive, 1m intake, and 1m for whatever custom mech you come up with is going to be the simplest and most competitive option (anything under 6 motors really isn’t competitive anymore, I don’t like it but that’s just how the games have been)
Hey @9MotorGang, could you explain to me why this is a rule of thumb? Would help my team in determining whether we want a 4M or 6M drive. Thanks!
While I’m not 9motpr gang that’s the general
Rule because it balances the speed to torque making it balanced
I really don’t understand how you could need more than 2 motors for your other mechanisms…
Me personally I would do 6 motor but my teacher won’t let us till mid season but you honestly should if no one is telling u otherwise