Minibot weight?

[nick_sheets]

Hey teams,

we were wondering what weight do you have to have the minibot at in order to drive it via direct drive rollers at .375 od?

ours is currently overweight in this area.

thanks!

[ajlapp]

we're running around 2.4 lbs.

[pfreivald]

Battery + motors + as little else as you can possibly manage.

Another consideration besides weight is normal force against the pole -- enough to get good traction but not so much that it adds much torque. This is a CRITICAL consideration, if our fooling around (erm, I mean, prototyping) means anything...

[1708xMr.Roboto]

Team 1708's Mini Bot is running around 2.4 pounds w/ Battery.

[IKE]

Originally Posted by nick_sheets

Hey teams,

we were wondering what weight do you have to have the minibot at in order to drive it via direct drive rollers at .375 od?

ours is currently overweight in this area.

thanks!

What weight are you at?

The way to calculate the weight is to try to roughly balance the peak power torque with your wheel diameter.

To do this take the peak power torque (you can use the search function and find the thread for the dyno data). Make sure you include both motors. Multiply by an efficiency factor of 0.8-0.9 (this is a guess but should be utilized to keep on the positive side of the power curve). This is the resultant torque. Then divide this by the radius of the roller, and you have the max weight condition for that size roller to still achieve peak power. Note the motors can provide more torque than this at lower speeds, but you will be on the stall side of the power curve (dangerous). If you stay on the positive side of the power curve, your minibot will be less weight sensitive, but also not fully optimized.