pic: Custom 3 CIM 2 Speed Gearbox
 

Re: pic: Custom 3 CIM 2 Speed Gearbox
 

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?*

Re: pic: Custom 3 CIM 2 Speed Gearbox
 

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?

Re: pic: Custom 3 CIM 2 Speed Gearbox
 

Looks cool! I like the layout.

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.

Re: pic: Custom 3 CIM 2 Speed Gearbox
 

Makes sense. I normally value space savings vs CG. I've been a bit envious of 125'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.

Re: pic: Custom 3 CIM 2 Speed Gearbox
 

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.

Re: pic: Custom 3 CIM 2 Speed Gearbox
 

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.

Re: pic: Custom 3 CIM 2 Speed Gearbox
 

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

Re: pic: Custom 3 CIM 2 Speed Gearbox
 

Here is an image of 254's [unpopulated] gearbox.