This is a quick gearbox I dreamed up using a lot of the Vexpro Face Bearing Gussets (8). The idea was to make it so that folks without the capability of making CNC milled parts could design their own gearbox with swappable gears to change ratios as needed.
This is a 2 stage reduction with no shifting, though will some work and extra VersaFrame you can make some pretty wild stuff.
You will notice that I stacked at least 2 faceplates in all places to make sure there was robust support for the bearings. Hardware is not shown. This is a little more expensive since the 0.750 diameter mounting boss of the CIM is not supported. Instead the CIMs have the Vex 8mm to 1/2 Hex part that is supported by a hex bearing.
You can keep extending this concept to add COTS shifter shafts from WCP or a 3rd CIM. Go nuts!
Disclaimer: I think this could be robust enough to last for a season, but please use caution. The most worrisome thing is that the CIM mounting bosses (0.750 diameter) are not mounted in anything and instead the motor drive shaft is constained. I could not find a flanged bearing with 1.125 OD and 0.750 ID, though I bet there is a needle bearing out there like this somewhere.
Feedback welcome!
-matto-
P.S. To Vex: If you want to make a second version of the face plate with different spacing (96 teeth perhaps) or a three hole version or a thicker version (.125 perhaps?) - I think even crazier designs are possible.
You can only attach certain formats, and even then only up to 2MB. Uploading to Drive or GrabCAD first helps. I recommend the latter because it has infinite file storage and revision control for free.
Looks pretty neat. What gusset does this use again? What size gears can you use?
Pretty clever! I’m hoping vexpro will come out with a transmission that attaches to a 1x2 tube in a similar fashion in the future. They have lots of cool gearboxes, but they don’t seem to bolt on to tubular frames very easily.
Versaframe face gusset. Here’s a drawing. Hole spacing is for 84 total teeth.
I knew one of the many gearbox designers would know how to help. Added link to the STEP above.
It is the .090 sheet metal Vex Face Bearing Gusset. It is sized for 84 Tooth 20 DP gears (C-C is 2.103). Vex Drawing is here.
Basically you get two gear reduction pairs of any two hex bore 20 DP gears that add to 84 teeth. The largest reduction is 66:18 (3.67).
It may not be as reuseable as other gearboxes and does take some assembly work, but is an entry level way to get into custom gearbox design. I think you could stack two 6" pieces of VersaFrame and make a standalone gearbox if you want.
I haven’t priced it (depends on your gear choices and if you go as crazy as I did with extra supporting gussets). My quick calc says as shown it is $50 plus the cost of the 5 gears (~$50), plus the mounting hardware, collars and shaft pieces. Not as cheap as the Vex Double Reduction at $60, but not bad for a custom gearbox with no CNC required IMO.
The largest reduction could even be 70:14 if you use 3/8" hex bore gears.
If there was a way to easily align these across a tube, like some kind of C-channel acting as a square, you could just make a gearbox with oversized holes made with a step drill and a piece of versaframe.
The original design used 8mm to 1/2 adapters and was supported by a hex bearing and therefore required a hex bore gear. As Adam pointed out, using a bushing is a better idea and allows you to use CIM gears.
If you want a less aggressive first stage, you can still use the adapter and a hex bore gear.
It looks like the two pieces VersaFrame still need to be precision machined for the gears to mesh well. Am I wrong? If not, how is this any different from any other custom gearbox?
EDIT: How are the CIMs attached to the top piece of VersaFrame? There are holes through the gusset plates, but I don’t see anything through the VF itself. Is the plan just to mount the CIMs to the gussets?
EDIT 2: Is there any reason why the first reduction has to also sum to 84 teeth, or can that be any gear ratio provided you use the right C2C distance?
Interesting idea. Have you done any price comparisons between using your method and using clamping gearboxes*?
*See the “gearing options” portion at the bottom of the page.
All the machining required on the versa frame for this can be done with a drill press or hand drill and a dremel. You can match drill all the gusset holes. Any slotting required for clearance for the first reduction gear can be done with a dremel, cutting wheel, and some patience. All the piloting is handled by the gussets and bearings, so no precision machining is required.
A total of 84 teeth (20DP) is the “right” C2C distance for the 2.103" spacing used by Vex for the gussets.
That’s even more disturbing than what I thought I was looking at earlier, which was disturbing enough. What’s the point of doing a VersaFrame “gearbox” with exposed gears if you have to cut out that many rectangular holes to allow gears to reach outside of the tube? For me at least, the answer is emphatically none.
I have seen what you are talking about. This drawing shows how clever Vex was when making the plastic bearing blocks and clamping gearbox.
My issue is that we used the plastic bearing blocks on our simple 2015 drivetrain and the blocks cracked a lot. To the point that we reinforced them with .125 sheet metal because we were tired of changing them. And that was for a game with no contact. We ran a Vex Double Reduction Gearbox, with its output into one of the plastic bearing blocks and then did a 54:30 reduction via the two pressed together blocks. I was not a fan, hence the desire for more durable metal parts. YMMV.
On the same topic I wish Vex & WCP would slightly modify the VersaBlock such that it has a small flat side and the same 84T spacing as shown above. It would be a small modification, but would make VersaBlocks even better (though still expensive).
