26-01-2014 17:16

apples000

Re: pic: Average 2014 Chassis

Quote:

Originally Posted by Richard Wallace -- 3 CIMs per side -- 28"W x 27.5"L -- Grayhill encoders -- Four AM 4" Performance Wheels with Nitrile Roughtop -- Two VexPro 4" Dual Omniwheels -- #25 Chain on 34 tooth sprockets with simple roller tensioner -- AM gears replaced by VexPro gears to reduce weight and friction

26-01-2014 17:24

Richard Wallace

Re: pic: Average 2014 Chassis

We measured about 17 Amperes free current using the stock AM gears, and about 10 Amperes free current after replacing with VexPro gears. Gears were well greased for both tests, and the results were repeatable.

AM steel gears appear rougher, while VexPro 7075 gears have smoother finish. Also, VexPro gears are AGMA 11 -- closer tolerances, better fit.

The free current really tells the story, though. Lower friction, less power wasted.

26-01-2014 17:47

JamesCH95

Re: pic: Average 2014 Chassis

I believe the VexPro gears are coated with some Teflon/ceramic mixture that reduces friction. In addition to the reasons mentioned above.

26-01-2014 18:19

Ian Curtis

Re: pic: Average 2014 Chassis

Quote:

Originally Posted by Richard Wallace We measured about 17 Amperes free current using the stock AM gears, and about 10 Amperes free current after replacing with VexPro gears. Gears were well greased for both tests, and the results were repeatable. AM steel gears appear rougher, while VexPro 7075 gears have smoother finish. Also, VexPro gears are AGMA 11 -- closer tolerances, better fit. The free current really tells the story, though. Lower friction, less power wasted.

26-01-2014 18:20

xForceDee

Re: pic: Average 2014 Chassis

Is the center wheel dropped? If so, what was the thought process for using omni's? Last year, my team did the same thing sort of against my wishes because I didn't see the purpose. It seems to me that as long as you power every wheel and only 4 can physically be on the ground, then turning will never be an issue. Despite that question though, looks like a great drive train. Nice job guys!

26-01-2014 18:33

Richard Wallace

Re: pic: Average 2014 Chassis

Quote:

Originally Posted by Ian Curtis Wow! That is a big difference. For those of us that don't know much about gears/wear-in/etc. would the AndyMark gears improve over time as the surface finish improves? I think I remember someone (971?) ran their gearboxes on a test stand prior to mounting them on their robot and found it wasn't really worth it. A 50% reduction in free current sounds like something that would be worth it though.

26-01-2014 18:34

apples000

Re: pic: Average 2014 Chassis

Quote:

Originally Posted by Richard Wallace We measured about 17 Amperes free current using the stock AM gears, and about 10 Amperes free current after replacing with VexPro gears. Gears were well greased for both tests, and the results were repeatable. AM steel gears appear rougher, while VexPro 7075 gears have smoother finish. Also, VexPro gears are AGMA 11 -- closer tolerances, better fit. The free current really tells the story, though. Lower friction, less power wasted.

26-01-2014 18:38

Richard Wallace

Re: pic: Average 2014 Chassis

Quote:

Originally Posted by xForceDee Is the center wheel dropped?