Originally Posted by aldaeron (Post 1515929)

Trying to attach the STEP file and cannot seem to find the attach button I am looking for. Help please?

Originally Posted by aldaeron (Post 1515928)

Originally Posted by asid61 (Post 1515960)

What gusset does this use again? What size gears can you use?

Originally Posted by asid61 (Post 1515960)

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.

Originally Posted by asid61 (Post 1515960)

Looks pretty neat. What gusset does this use again? What size gears can you use?

Originally Posted by AdamHeard (Post 1515965)

1.125" OD x .75" ID bushings are available on mcmaster. I'm assuming the goal is to pilot the CIM in a 1.125" bore?

Originally Posted by aldaeron (Post 1515967)

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).

Originally Posted by aldaeron (Post 1515967)

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.

-matto-

Originally Posted by asid61 (Post 1515975)

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.

Originally Posted by s_forbes (Post 1515971)

If you are going from a CIM, you can have a 12/72 reduction, or even an 11/72 reduction using vexpro's 11 tooth pinion gear (link).

Originally Posted by Ari423 (Post 1515992)

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?

Originally Posted by Ari423 (Post 1515992)

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?

Originally Posted by Lil' Lavery (Post 1516013)

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.

Originally Posted by Lil' Lavery (Post 1516013)

A total of 84 teeth (20DP) is the "right" C2C distance for the 2.103" spacing used by Vex for the gussets.

Originally Posted by Ari423 (Post 1515992)

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?

Originally Posted by GeeTwo (Post 1516025)

There is no "top piece of VersaFrame" - the assembly above the single tube of VF is apparently composed of Bearing Gussets riveted together.

Originally Posted by GeeTwo (Post 1516025)

There is no "top piece of VersaFrame" - the assembly above the single tube of VF is apparently composed of Bearing Gussets riveted together.

Originally Posted by Lil' Lavery (Post 1516052)

There are gussets bolted to another portion of 2x1" versa channel.

Originally Posted by Han Solo, in Star Wars IV: A New Hope, upon recognizing the Death Star as not being a moon

I think you're right.

Originally Posted by Lil' Lavery (Post 1516013)

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.

Originally Posted by GeeTwo (Post 1516063)

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.

Originally Posted by aldaeron (Post 1516076)

I never said this was a particularly efficient way of making a gearbox. It does involve a lot of cutting and drilling and clamping. If you want easy, buy something off the shelf - there is a lot of good stuff out there. I have a lot of younger students who LOVE clamping and drilling with the drill press.

The intention is for teams without access to a CNC to be able to make "custom" gearboxes. This is primarily an idea for my team - we used to have access to a CNC mill via a local makerspace, but it went out of business. Students used to enjoy designing and fabricating the gearboxes themselves. By "custom" I mean that the students can design the gearbox and select from more gear ratios than what Vexpro, AM and WCP offer as COTS. And if they make a mistake or are unhappy with the first iterations, the gears can be swapped.