15-07-2016 01:08

ollien

Re: pic: Streamlined Basketball Drive

Wow this looks neat! My only concern is the CIM motors on the bottom. How will you wire them without the wires being crushed or the insulation melting from the heat of the motors?

15-07-2016 01:13

asid61

Re: pic: Streamlined Basketball Drive

I like the form factor a lot, but I'm seconding Ollien's comment. Expanding it out by 3/4" or so would fix the problem.
The use of 1 wheel for 2 balls is very clever, but you might want to spring load the casters to keep contact with the wheels as they wear down. The issue of "drilling" into the ball with an un-moving wheel is still there, but maybe if you used thinner wheels and something like a metallic ball you might have better luck.

EDIT: What's the FPS and weight?

15-07-2016 03:34

cad321

Re: pic: Streamlined Basketball Drive

I agree with the comment above about the wire spacing, however while were there, on the model posted to grabcad, it appears that the cims themselves are actually interfering with each other. The small round protrusion on the backs of the cims (~1in diameter) are going into the other cims by about 1/8in.

17-07-2016 20:19

Brandon Zalinsky

Re: pic: Streamlined Basketball Drive

It's like the decagon wheel, single billet chassis robot... but actually buildable. Props, looks pretty $@#$@#$@#$@# neat.

20-07-2016 20:00

dirtbikerxz

Re: pic: Streamlined Basketball Drive

if someone actually builds this, i will hold you in awe forever

20-07-2016 22:29

GeeTwo

Re: pic: Streamlined Basketball Drive

The weight of the robot (excepting the basketballs) is supported by the downward-facing ball casters. Basketballs are typically pressurized to 8psi, so assuming the robot weighs 100 lb, you would need to apply that force over 3+ square inches on each ball. As the casters are not that large, the basketball would significantly deform at this point to bear the load, interfering with the drive-ability (though obviating the need for springs). Deformation would get worse under acceleration. I would consider stiffer balls, perhaps like asid61's suggestion of metal (or rubber over metal) ones, or at least larger load-bearing ball casters.

Edit: This would be even cooler as a kiwi; I think the forces would add up properly for rotation and translation, though less efficiently at the ball-carpet interface.

In either case, It appears that the inverse kinematic equations are to drive each wheel as though it were an omni, but in the opposite direction. Negative Killough/Mecanum for four-ball, negative kiwi for three-ball.

26-07-2016 14:41

Lireal

Re: pic: Streamlined Basketball Drive

Could basketballs be replaced by a metalsphere, with some kind of coating for traction? Would a sphere like this work: http://www.kingmetals.com/Catalog/Ca...Id= 204&NSM=Y

If not, how thick would 8-10 in diameter steel spheres need to be to support the weight of a ~100 lb robot?

26-07-2016 18:51

BotDesigner

Re: pic: Streamlined Basketball Drive

I think that would be a better way to go. As GeeTwo pointed out, the deformation in the basketballs is going to cause major problems with the driving.

I think the best way to "coat" the basketballs would be to cut some type of grippy material into hexagons and pentagons and glue them on like the ones on a soccer ball.

As for the strength of those steel spheres, I have no idea; you probably have to do some force calculations. They are most likely strong enough; I have played with some garden decoration spheres and they would appear to be able to support this.

26-07-2016 20:38

GeeTwo

Re: pic: Streamlined Basketball Drive

While gluing a dozen pentagons and a score of hexagons could possibly work, I was thinking of spraying pickup truck bed-liner or similar material onto a metallic spherical shell.

27-07-2016 13:17

Andrew Schreiber

Re: pic: Streamlined Basketball Drive

https://www.chiefdelphi.com/forums/s...12&postcount=9

27-07-2016 14:53

Lireal

Re: pic: Streamlined Basketball Drive

How would you do the calculations to determine if a hollow metal sphere is strong enough to support the weight of the robot?

19-09-2016 16:51

Evan Scholl

Re: pic: Streamlined Basketball Drive

I would put omnis instead of whatever wheels you currently have in because the friction is really going to deteorate both the ball(and also the omnis) whilst also causing slow movement

19-09-2016 23:31

snoman

Re: pic: Streamlined Basketball Drive

Very fun idea has anyone ever seen this https://jet.com/product/detail/7e5dc8f5b3d64f6a8b02b06bea7bfcbc?jcmp=pla:ggl:gen_ animals_pet_supplies_a3et_supplies_dog_supplies_ dog_toys_a3_other:naLA_345535620_23673114300_pla-161677456140:na:na:na:2&code=PLA15&ds_c=gen_animal s_pet_supplies_a3&ds_cid=&ds_ag=pet_supplies_dog_s upplies_dog_toys_a3_other&product_id=7e5dc8f5b3d64 f6a8b02b06bea7bfcbc&product_partition_id=161677456 140&gclid=CjwKEAjwmf6-BRDi9fSN7Ijt1wUSJAASawcjr2S_o9T_d31eUk7-anxGmf88CDruJ-5qN8eIl4WO0xoC8prw_wcB&gclsrc=aw.ds