14-11-2014 00:00

glennword

Re: pic: Lightweight (relatively) 2 CIM Shifting Swerve Drive

How did you do the serpentine calculations? Gates IQ?

14-11-2014 01:28

asid61

Re: pic: Lightweight (relatively) 2 CIM Shifting Swerve Drive

Looks good. Why do you have two encoders? Is one for rotation?
Is the shifting shaft custom or vex?
What pitch is the belt?
Also, out of curiosity: is the gear running on a bearing or is it just bolted to the wheel? I designed mine with a bearing in the gear for safety, but is it necessary?
Is the wheel running on bearings or just on an aluminum hollow axle?

14-11-2014 02:20

Bryce2471

Re: pic: Lightweight (relatively) 2 CIM Shifting Swerve Drive

No, I just did an approximation with the center of the belt backing. It does't need to be perfect. If the belt length was off by up to a half inch in either direction the tensioner would adjust.
Yes, one measures wheel orientation, and the other measures travel speed.

It's vex, but it's shortened on both ends.

HTD 5mm

I doubt that a bearing in the gear is necessary. With a dead axle that's well
supported, bearings on either side of the wheel, and a gear that's close to the wheel, you shouldn't have any trouble just bolting the gear to the wheel.

The drive wheel is running on two ball bearings on an aluminum hallow axle.

14-11-2014 03:16

asid61

Re: pic: Lightweight (relatively) 2 CIM Shifting Swerve Drive

Can you put one bearing in the gear and one in the opposite side of the wheel? You still get the support that way, as well as alignment. And you still only use two bearings.

14-11-2014 07:57

Al Skierkiewicz

Re: pic: Lightweight (relatively) 2 CIM Shifting Swerve Drive

Nice Job!

14-11-2014 12:28

hrench

Re: pic: Lightweight (relatively) 2 CIM Shifting Swerve Drive

really amazing. Now all you need is to be allowed eight CIMS on the bot. and a refrigerated main breaker.

14-11-2014 13:51

Bryce2471

Re: pic: Lightweight (relatively) 2 CIM Shifting Swerve Drive

you could do that, although it's not the optimal solution in my mind because the bolts would be loaded in shear by the weight of the robot.
Thank you!
this accually only uses 1 CIM and 1 mini CIM. The breaker would most likely be okay, assuming that auto-shifting code was used.

14-11-2014 22:04

asid61

Re: pic: Lightweight (relatively) 2 CIM Shifting Swerve Drive

Good to consider.
What miter gears are in there? Are they the vex ones?
And I assume those pulleys are aluminum... just a random thought.

14-11-2014 23:26

Bryce2471

Re: pic: Lightweight (relatively) 2 CIM Shifting Swerve Drive

They are 20 tooth 20 pitch steel gears from SDP/SI.
Yes they are aluminum pulleys from B&B man.

15-11-2014 00:04

asid61

Re: pic: Lightweight (relatively) 2 CIM Shifting Swerve Drive

Ok, good. It just seemed like they would be heavy for this design due to their solidity.

15-11-2014 16:43

Bryce2471

Re: pic: Lightweight (relatively) 2 CIM Shifting Swerve Drive

What are you referring to as being solid? Are you talking about the aluminum pulleys or the steel miter gears?

Also, what roller bearing did you use as an idler? I just put a solid steel stand-in to fill the space.

15-11-2014 22:12

asid61

Re: pic: Lightweight (relatively) 2 CIM Shifting Swerve Drive

The pulley is solid aluminum, unlightened. The miter gears I would highly recommend against shorening the hub (widening the bore it fine) due to the strange geometry making it hard to machine.

For the bearing, I used these:
http://www.bocabearings.com/bearing-...2-SR1634ZZ3PS2

16-11-2014 01:09

Bryce2471

Re: pic: Lightweight (relatively) 2 CIM Shifting Swerve Drive

Thanks for the resource! I've never used them.
Although, I was wondering about the bearing that you used to tension the lower belt, not the 0.75" bearing for the shifter. lol

16-11-2014 05:00

asid61

Re: pic: Lightweight (relatively) 2 CIM Shifting Swerve Drive

Oh. For the lower belt, I just used a steel sleeve around a slightly longer aluminum sleeve. The aluminum sleeve had a 10-32 screw go through and clamp to the top plate. Then the steel sleeve was still free spinning, but constrained in place.
You could just use a 1/4" or 5/16" aluminum sleeve and use a 1/4" or 5/16" bearing from McMaster or Boca Bearings. I know 192 used Boca last year for their gearbox gears, but personally I haven't used them.

16-11-2014 13:43

Bryce2471

Re: pic: Lightweight (relatively) 2 CIM Shifting Swerve Drive

Thanks for the good info! I'll do some looking around for a needle bearing that will do the job. If I don't find one that fits the bill, I'll probably resort to a brass or IGUS bushing.

18-11-2014 01:08

asid61

Re: pic: Lightweight (relatively) 2 CIM Shifting Swerve Drive

Bronze over brass. Brass does not have the same bearing qualities as bronze.

18-11-2014 02:07

Bryce2471

Re: pic: Lightweight (relatively) 2 CIM Shifting Swerve Drive

I'm going to use a 0.3125" ID 0.5" OD 0.5625" width needle bearings from SDP-SI. They're only like $5, so why not.

18-11-2014 02:20

Tyler2517

Re: pic: Lightweight (relatively) 2 CIM Shifting Swerve Drive

Make sure the shaft has a surface hardness that can use it with out destroying the bearings/the shaft.

19-11-2014 18:31

Gregor

Re: pic: Lightweight (relatively) 2 CIM Shifting Swerve Drive

Love the out of the box design.

What are the ratios, it looks like it has a tiny spread?

19-11-2014 19:01

Bryce2471

Re: pic: Lightweight (relatively) 2 CIM Shifting Swerve Drive

It's free-ish speeds are posted in this thread:
http://www.chiefdelphi.com/media/photos/40954?
it's ratios are 2.85to one in high, and 5.13 to one in low. It's running a 2.75" wheel. The speak is small enough to use autoshifting code, but I wouldn't call it tiny.