Do you all think that a 500rpm drivetrain with 2.75" Wheels is going to be Fast, Slow, or Mid. (Compared to a normal Drivetrain)
- Fast
- Mid / Default
- Slow
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voters
this is a pretty generaly good scale:
<55 slow,
55<speed < 65 mid
65 < speed < 75 faster than average (slightley)
75<speed<86 Fast
<86 is blistering fast.
i think most ppl will sit in the 75 to 86 range this season. kinda like OU. but the 65 to 75 rage with a good driver will keep up
whast more important than your drive speed is your driving practice. also if im not mistaken your gonna have to chain something to get 500 rpm on 2.75 or your gonna have to do some wierd gearing cuz the only ration i can think of that does this speed gear wise is 600rpm geared dwon 60:72, and you cant put a 72 gear on a 2.75 wheel.
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Sorry, I am confused.
What do the numbers refer to?
Yes I am using sprockets (I know that they have some downsides). But it is legal to cut out plastic gears (so if sprockets are too weak I can use the plastic).
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What @TimmyOsborne is referring to is Inches Per Second. Teams need to pay attention to the speed of the robot instead of the RPM of the motors.
Inches per wheel rotation - distance traveled per a single rotation
2.75 wheel x 3.14 [Pi] = 8.6 inches per rotation.
Revolutions per second (RPS) - the speed of the motor per second.
A 200 RPM motor / 60 seconds = 3.3 revolutions per second.
Results
A 4.0 inch wheel, using a 200 RPM motor is (200 / 60) x (4 x 3.14) = 41.9 inches per second. At this speed a robot would cross a field in 3 seconds. Bigger wheel, slower motor.
The values that @TimmyOsborne is providing give you a rough estimate for robot speed. Note that the higher the IPS the hotter motors get and the faster your go through batteries. Other factors to consider is the robot weight and how much torque (pushing power) a robot has to compete against other teams. 60 - 70 IPS seems to be the sweet spot for both speed and strength with six motors.
To answer your question, 2.75 wheels spinning at 480 RPM is 69 IPS.
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the sprokets themselves wont be weak. the chain that transfers the power is prone to breaking. if you make use of chaing guardes and carful placment thne you prolly wont have to many usses. but with the updated plastic your never gonna be able ot make gears that are sufficent.
Unrelated question but…
Do teams really run >86 in/sec? I thought ~75 was pretty much the limit in most cases.
over 86ips is baiscially un heard of in HS although it has happend a couple of times. in OU some of the descore bots ran 102ips. but they were like sub 10 pound bots and 8m drive and uncontrollable.
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86 is pretty much the max at 600 rpm on 2.75s
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Now that you mention it, I do remember playing a match with a really fast 8 motor drive… they pushed half of the triballs out of our goal while trying to score. We lost that match.
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