pic: Custom 3 CIM 2 Speed Gearbox

[Bryce Paputa]

[cdm-description=photo]40658[/cdm-description]

[R.C.]

What spread are you using?

I take it this is designed to mount into a non WCD style drive? I bet you could probably flip the motors around and hang this over your wheels if you use a 24:60. Also I think your weight calculations are off. To be almost 2 lbs lighter than the DS Standard 3 CIM you'd have to weigh: ~2.8 - 2 = .8 lbs

http://puu.sh/8Zy3d/55951f0c15.png

and your probably around the same weight due the fact the internals + motor weight is about the same. Weight of 3 CIM DS Standard (Non WCD)

http://puu.sh/8ZxQA/bb0bb3d496.png

EDIT: *Are you comparing weight to the 3 CIM WCD with PTO?*

[Bryce Paputa]

The spread is 3.64. It is for a sheet metal, non WCD chassis. I considered putting the motors over the wheels, but I decided that the CG benefits of lowering 17 pounds around 4 inches would be more beneficial. My weight estimate only says 10.999 lbs, but I was comparing it to the 12.94 value from http://www.wcproducts.net/wcp-shifter-3cim/ (Standard, non-WCD, with 3 14t motor pinions, motors and 1 pneumatic cylinder). I think mine has one or two fewer gears and is thinner, but .2 lbs can probably account for that. I wonder how they got 12.94 lbs?

[Jared]

Looks cool! I like the layout.

What spread are you using?

I take it this is designed to mount into a non WCD style drive? I bet you could probably flip the motors around and hang this over your wheels if you use a 24:60.

But then he'd loose the reduction with the chains.

I'm not sure that it will be a problem, but the pinion gear on the middle CIM is going to have twice the load the others would have. I know that some teams with a similar layout have the idler gear between a CIM and the next stage of reduction, as opposed to between two CIMs.

[R.C.]

The spread is 3.64. It is for a sheet metal, non WCD chassis. I considered putting the motors over the wheels, but I decided that the CG benefits of lowering 17 pounds around 4 inches would be more beneficial. My weight estimate only says 10.999 lbs, but I was comparing it to the 12.94 value from http://www.wcproducts.net/wcp-shifter-3cim/ (Standard, non-WCD, with 3 14t motor pinions, motors and 1 pneumatic cylinder). I think mine has one or two fewer gears and is thinner, but .2 lbs can probably account for that. I wonder how they got 12.94 lbs?

Makes sense. I normally value space savings vs CG. I've been a bit envious of 125 (http://puu.sh/8ZC9R/40d21d24e5.jpg)'s setup this past year.

The "builder" on the site doesn't work so hot, its mainly an approximation for shipping. We'll be fixing that value in the coming months with a site update.

[R.C.]

Looks cool! I like the layout.

But then he'd loose the reduction with the chains.


For this setup it wouldn't really matter as you can just get a larger reduction in the chain setup. It would be a much larger deal if the OP decided to direct drive a wheel.

[Bryce Paputa]

My FEA gave the middle pinion a safety factor between 3 and 5, but it will be something that we inspect regularly. We're designing a drivetrain that should generally avoid pushing matches, so I'm not too worried about it, and if it does break, we'll have weeks to fix it unlike in the build season. I think 254 may have done something similar last year (2013) in their gearbox with a dual loaded pinion, but I'm not certain if they did or if it worked well.

[Knufire]

If I remember correctly, 254's 2014 gearbox had a similar layout with the motor pinions.

[tim-tim]

If I remember correctly, 254's 2014 gearbox had a similar layout with the motor pinions.

Here is an image of 254's [unpopulated] gearbox.
https://farm3.staticflickr.com/2899/13993659880_6b7830cac4_c.jpg