I’m going to jump on the 775pro train here. This is an adapter to convert two 775 series motors into a CIM-style input with a similar free speed to a CIM motor. I was inspired by FRC 88’s Double 775Pro DoubleBack CIM-SIM-CIM-ile. The difference is that this is designed to be used with the TB Mini and KOP chassis instead of a VexPro 3CIM Ball Shifter. Because of that, it is not a flipped gearbox (i.e. the motor output shafts face the gearbox output shaft). It is also a bit smaller and lighter than 88’s gearbox by using a dead-axle 60t idler instead of a live-axle 80t idler.
Yeah it’s the housing for a TB Mini (i.e. the gearbox in a KoP chassis). I would have shown the whole chassis in the render, but it would have took a while to render and killed my computer.
I would love to get any other feedback anyone might have to offer. I think this could be a good alternative to teams that want to keep the KoP chassis but want the extra power of 6 CIMs.
I love this idea! In fact, I think I’m gonna steal it. I’ll try and work on a similar design and see what I come up with. Since this is assumedly going to be printed, do you have any specifications on material or anything?
Also, I checked out your GrabCAD. You’ve only posted the assembly instead of doing a Pack and Go, so when I open the assembly, I get a bearing and a few bolts.
Honestly, the students on my team have more experience with the actual printing aspect of 3D printing than I do, so I would trust their judgement on material selection better than mine.* With my limited knowledge, I would say it would probably be printed from PLA because ABS can warp and change the C-C distances for the gears (and I think we do most our printing in PLA). I made the wall thicknesses based off the approximate strength of other 3D printed designs I’ve seen (without thinking about material), but if we find that something is too thin with a given material there are very few places where walls can’t be thickened without making major changes to the design.
I uploaded the pack and go so you can now download and view the full assembly.
*I modeled this myself, separate from my team. My personal opinion is that I don’t mind them starting with my designs as long as I explain why I chose to do everything how I did it. As we would iterate, I would expect them to change the design to improve it and make it their own. One of the major ways they would change it would be to use their better knowledge of 3D printing techniques to fix any problems they see in the design.
Nice. My only comment is that if you are not going to have the motors double back on the gearbox then you can eliminate the idler gear and go directly to a gear that drives the “CIM Shaft.”
I have uploaded the CAD of our robot, Jet Fuel, to my GrabCAD account (here). I recommend using something closer to that design if you are going to do a 4 775Pro drive.
Also, you should probably follow me on GrabCAD if you want to see fun and useful FIRST related CAD as I upload them rather than waiting for me to get around to linking to them on ChiefDelphi.
I’m not quite sure how you would do this and still end up with the right gear ratio without using gears from other sources. I thought about forgoing the idler, but I couldn’t make it work with a 40:12 final gear ratio (to approximately match free speeds with a CIM). The C-C distance of two 775pros next to each other is about 45mm. The C-C for a 12t 32dp gear mated with a 40t gear mated with another 12t gear is at most 41mm. Unless I’m making a mistake with my math somewhere, it simply wouldn’t fit. That’s why I had to use a 60t idler.
