pic: Vex Face Bearing Gusset Gearbox [Archive]

asid61

02-01-2016, 19:13

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

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?

AdamHeard

02-01-2016, 19:26

[cdm-description=photo]42599[/cdm-description]

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?

s_forbes

02-01-2016, 19:29

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.

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

Versaframe face gusset. Here's a drawing (http://content.vexrobotics.com/vexpro/pdf/217-4183-Drawing-20141111.PDF). Hole spacing is for 84 total teeth.

aldaeron

02-01-2016, 19:33

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.

I knew one of the many gearbox designers would know how to help. Added link to the STEP above.

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

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 (http://content.vexrobotics.com/vexpro/pdf/217-4183-Drawing-20141111.PDF).

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-

aldaeron

02-01-2016, 19:35

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?

This is what happens when late night designing with "holiday cheer"

Should have thought of that!

s_forbes

02-01-2016, 19:39

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).

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 (http://content.vexrobotics.com/vexpro/pdf/VEXpro-Gears-CIM-Drawing-20141002.PDF)).

Oblarg

02-01-2016, 19:41

I really like the easy chain access with this design. Clever.

asid61

02-01-2016, 19:44

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 (http://content.vexrobotics.com/vexpro/pdf/217-4183-Drawing-20141111.PDF).

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-

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.

aldaeron

02-01-2016, 19:47

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.

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 (http://content.vexrobotics.com/vexpro/pdf/VEXpro-Gears-CIM-Drawing-20141002.PDF)).

The original design used 8mm to 1/2 adapters (http://www.vexrobotics.com/vexpro/hardware/217-3255.html) 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.

Ari423

02-01-2016, 20:09

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?

Lil' Lavery

02-01-2016, 20:55

Interesting idea. Have you done any price comparisons between using your method and using clamping gearboxes* (http://www.vexrobotics.com/vexpro/motion/gearboxes/217-4156.html)?

*See the "gearing options" portion at the bottom of the page.

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?
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.

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

Ari423

02-01-2016, 21:29

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.

I didn't realize you could use the gussets as a guide to drill the other holes. That's a smart idea!

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

I didn't see the double plates in there; I thought they were all single plates. Never mind then.

Overall, I really like this design! I might just suggest it to my team.

GeeTwo

02-01-2016, 21:31

Ari423

02-01-2016, 22:02

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

Are you sure? That look a lot like gussets bolted onto VersaFrame with holes drilled into it on the 3D model.

EDIT: still not sure how the CIMs are being attached to the gussets and VersaFrame

Lil' Lavery

02-01-2016, 23:36

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

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

GeeTwo

03-01-2016, 00:12

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

I think you're right.

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.

aldaeron

03-01-2016, 00:55

Interesting idea. Have you done any price comparisons between using your method and using clamping gearboxes* (http://www.vexrobotics.com/vexpro/motion/gearboxes/217-4156.html)?

*See the "gearing options" portion at the bottom of the page.

I have seen what you are talking about. This drawing (http://content.vexrobotics.com/vexpro/pdf/217-Clamping-Gearboxes-VersaFrame-Drawing-20141016.PDF) 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).

aldaeron

03-01-2016, 01:05

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 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.

GeeTwo

03-01-2016, 01:22

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.
As always, your mileage may vary.