Single CIM 2 Speed Gearbox?

Technical Technical Discussion
#1

So, I’m planning on building on octocanum drive in the off season as a side-project, and I was planning on using a single CIM for each of the modules, as is usually done for octocanum. I was wondering if it would be possible to do my gear shifting through a gearbox instead of gearing the chains/belts differently in the module.

The problem is, I haven’t seen any single-cim 2 speed shifters and I’d like to avoid the 2-cim shifters for the sake of weight… does anybody know of a 2-speed shifter that is designed for 1 CIM?

#2

There doesn’t seem to be any gearboxes like that readily available, it looks like if you really need a 1 cim gearbox you will have to design it yourself.

Honestly it seems like the weight savings from 1 CIM gearboxes over 2 CIM gearboxes is minimal and 2 CIM shifters allow you to add more motors to your drivetrain in the future.

#3

I don’t quite see the point, maybe you can explain your reasoning. Why would you want to add a piston to shift within the gearbox when you need a piston to switch between the wheels anyway? It seems like more complexity, weight, manufacturing work, and programming coordination, and I don’t see the benefit.

#4

An option that would give you two speeds is to have the traction wheel geared differently then the mecanum wheel since only one set of wheels is in contact with the ground at a time. In other word, do you primary reduction to the mecanum wheels, then do a chain or belt reduction between the mecanum and the traction wheel in each pair.

#5

For Aerial Assault, DiscoBots used high traction wheels with a smaller diameter to get greater pushing power and did not need to use a shifting gearbox. They also used a CIM and a mini-CIM on each corner. The high-traction wheel and the mecanum wheels were chained together and ran at the same RPM.

#6

An option that would give you two speeds is to have the traction wheel geared differently then the mecanum wheel since only one set of wheels is in contact with the ground at a time

I’m assuming the original point of shifting at the gearbox end is to give the option of changing between high and low speeds at both the mecanum and traction stages.