Modular Drive System

[DavisDad]

Originally Posted by MrBasse

...as these modules as pictured wouldn't be up to the task of FRC in my opinion.

MrBasse,

Could you say what about the design you think is weak?

Thanks

[MrBasse]

Originally Posted by DavisDad

MrBasse,

Could you say what about the design you think is weak?

Thanks

I don't think the design itself is weak, simply that the current version posted would be up for quite a task. I have no clue as to speed, but I would be concerned with the gearboxes (we have found planetariums to be a tad fragile) in a pushing match. An open frame with little structure to tie the front end together would have me concerned as well for impact, but I think with the scale of your frame rigidity shouldn't be much of an issue. Again, these are simply in the prototype you have proposed. I haven't a clue what this could delvelop into when built for FRC. I am excited to see what it could become, as a modular approach is something we have been contemplating for our entire history in FRC.

Beyond that, it's a tiny little thing! Sure does make the battery look massive! (I know it is a prototype!)

[DavisDad]

I guess my post is unclear. The prototype is the FTC team. We're scaling up for FRC. The FRC battery was used to add weight to simulate future game components. The open frame was min structure for testing drive performance

[MrBasse]

Originally Posted by DavisDad

I guess my post is unclear. The prototype is the FTC team. We're scaling up for FRC. The FRC battery was used to add weight to simulate future game components. The open frame was min structure for testing drive performance

No you are good with your clarity. But only having smaller scale design to base my opinion on, I simply pointed out my concerns. I think this has great promise and am excited to see what the FRC scale version is capable of.

[DavisDad]

[magnets]

Originally Posted by DavisDad

This is cool, but I'm worried about the thrust loads the shaft on the CIM will receive. It's been a while since I've taken a CIM motor apart, but I'm pretty sure you don't want to be loading the shaft like that. If you placed some spacers on the CIM shaft so that any downward load on the shaft would be transferred to the plate the CIM is mounted on, you'd probably be better off.

[DavisDad]

Originally Posted by magnets

This is cool, but I'm worried about the thrust loads the shaft on the CIM will receive. It's been a while since I've taken a CIM motor apart, but I'm pretty sure you don't want to be loading the shaft like that. If you placed some spacers on the CIM shaft so that any downward load on the shaft would be transferred to the plate the CIM is mounted on, you'd probably be better off.

Hey Magnets,

Yea, there are still some loose ends on the design. I need to check the thrust load specs for "deep groove" ball bearings. If they can handle the loads, the gear will butt against the inner race; otherwise we'll have to use thrust bearings. I didn't fix the gap between pinion and bearing yet.

[DavisDad]

Had to move planetary gear set outside wheel...

[geomapguy]

This might be useful for you guys...

http://www.andymark.com/product-p/am-2622.htm

[DavisDad]

Originally Posted by geomapguy

This might be useful for you guys...

http://www.andymark.com/product-p/am-2622.htm

Hey geomapguy,

Thanks for the AM suggestion. I looked at that, but want to optimize for FRC space and function. And, I'm learing about gearing; this is my first time building a gearbox. We may end up using a COT as the designs so far are more complex than I'd hoped. I haven't received the Matex planetary gear set (pic & link below) and need to determine the shafting requirements for alignment and loading.

Also, to use the CIM with the AM planetary set, you have to trim the motor shaft 1/4". Is modifying the shaft FRC legal?
.

PN: 75-5MLD

The 5:1 ratio units I ordered cost $73 ea

[DavisDad]

Progress update:

I've got 3 designs roughed out:

1. Planetary 5:1 reducer located in the Mecanum hub. I was excited about this when I found this video: e-Bike Hub Motor I immediately thought of the Sturmey-Archer 3-speed bikes of my youth. I got an old unit from my local bike shop's junk bin and thought I had a cheap source for the planetary set. The design I've sketched requires pretty complicated shafting and I'm doubtful about putting the planetary at the end of the gear train (shock stresses). the current design requires disassembly of the Mecanum to access the planetary set Also, I envision an oil dip system for lubrication and expect this to be a problem in the hub.
2. Move the planetary set outside hub but on wheel axis. This has the same issues with gear tooth stresses.
3. Move the planetary set to motor shaft and integrate into one gearbox with the 3:1 bevel gear set. AM has a COT setup for this, as geomapguy pointed out: AM COT
   

I haven't totally given up on the gear-hub idea. I'm waiting for the Matex set to arrive. When I get it in my hands and get a better feel of mounting/shafting requirements, I'll know better how to proceed...

[geomapguy]

Originally Posted by DavisDad

Is modifying the shaft FRC legal?

Yeah it's legal.

Modifying the shaft and removing the window motor locking pins are the only legal modifications you can make to a motor.

[cgmv123]

Originally Posted by DavisDad

Is modifying the shaft FRC legal?

Originally Posted by geomapguy

Yeah it's legal.

Modifying the shaft and removing the window motor locking pins are the only legal modifications you can make to a motor.

Obligatory disclaimer that the relevant rules can change for the upcoming season.

[DavisDad]

Thanks geomapguy and cgmv123 for your replies.

I think we'll go this route; planetary in-line w/ motor and 90 deg bevel set to wheel. This is much simpler than the previous designs.

[DavisDad]

My son and I made these movies (links below) to show Mecanum with speed control. This is the FTC teams prototype; not FRC. This is the design from which we're scaling up.