Securing gears on shafts

[Joe G.]

seconded on the collars. A round bore collar would also probably work okay.

[R.C.]

We use McMaster.com, go to their site and type in "aluminum collar". Click on About aluminum collar and there you go, the best method, we used 20 aluminum collars this year on our robot for multiple purposes.

[vivek16]

eclips would probably be a good solution. I haven't used them before. I still don't think I have enough clearance for the locking collars.

What do you think about gorilla glue? It is a gearbox so there should be no side load on the gears. Wouldn't a few dabs of gorilla glue work?

thanks, Vivek

[Joe G.]

For most purposes, a decent Epoxy will hold better than gorilla glue. In either case, if you choose to do so, make sure all parts are completely grease-free before application.

you could also use a small roll pin, if you have the machining capabilities to do so (which you probably do, if you are custom making a gearbox) as the Tough box did this year.


How much clearance do you have?

If there is not enough clearance between the gears for shaft collars, but more than 1/16 of an inch, small spacers (cut from tube stock, or from the IGUS bag) have worked well for us in the past, with either shaft collars where there is more clearance, or the gearbox walls to hold all the parts together.

[vivek16]

By clearance I mean a gear from another shaft in the gearbox comes too close to the hex shaft which would need a collar/spacer. Sorry if that doesn't make sense. It makes sense to me but I have the gearbox memorized.

After talking to Chris lyddiatt from 1114, I've decided to go with roll pins. Although, more ideas would be appreciated if teams have found any creative ways to secure gears.

thanks, Vivek

[Joe G.]

Oh, I thought you meant that two gears on the same shaft needed to be very close together.

Roll pins should work fine.

[thatmorman]

set collars work very nice, but they are heavy. one solution that is a little more cheap is zip ties. it doesn't necessarily look nice, and its not the most affective, but it works in most situations...

[Dick Linn]

Snap rings would be good. You could also just use tubular spacer sleeves or thrust washers, depending on your setup. (One year the kit of parts contained a right-angle gearbox and required sleeves to locate the pinion over the larger helical gear.)

[,4lex S.]

I don't know if it has been mentioned already (possibly by a different name) but I have often seen circlips function well to keep things on shafts in place. Nylon spacers also work alright (assuming they don't grind on anything). If you have the space, a custom shaft can often be designed to have a high spot that secures the side of one or two gears too. I like circlips though because they are easily removable and take up little space on a shaft.

[vivek16]

How do you machine the groove needed for a circlip(snap ring, e-clip, etc)? Do you need a special lathe bit or will a triangular insert dealie suffice?

thanks, Vivek

[Aren_Hill]

Special bit is a requirement sad to say

[dlavery]

You don't need to resort to expensive insert systems for a basic operation like this. Grinding a cutting tool to cut a retaining ring groove is a fundamental lathe skill that you will want to practice. Based on the size of the retaining ring you are using, determine the groove width and depth. These standard dimensions can be found in Machinery's Handbook (if you don't have a copy, get one; it is possibly the most useful reference manual you will get in a long time). For certain size shafts, you can also look up the dimensions here.

Once you know the groove width, use a bench grinder to grind a piece of HSS tooling to the width of the groove. You basically want to grind the HSS to the shape of a parting (cut-off) tool, but shorter (there is a nice tutorial showing how to grind a parting tool here). The length of the cutting portion of the tool does not need to be significantly longer than the maximum depth of the groove. Grind in a 7-10 degree rake to the top of the tool, and appropriate relief angles to the sides and face (so only the tip of the tool actually cuts and contacts the sides of the groove). Mount the tool bit in a holder, and you are good to go.

Unlike carbide inserts, HSS tool blanks go for about a dollar each if you are a careful shopper.

-dave


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[AndyB]

We used PVC with an ID that was slightly larger than our shaft diameter as spacers for our wheels. I don't see why you couldn't use them on gears. If you have the machining capability, I would use roll pins.

[Cory]

Originally Posted by vivek16

How do you machine the groove needed for a circlip(snap ring, e-clip, etc)? Do you need a special lathe bit or will a triangular insert dealie suffice?

thanks, Vivek

You can grind a toolbit, or buy a thinbit style toolholder, and then a 0.030 grooving insert.

They're not cheap. I had to go buy some from our local distributor during build this year, since we needed them ASAP and couldn't wait to purchase them online. Each insert was about $12.

The holder is probably $40-80 as well.

[vivek16]

Originally Posted by Cory

You can grind a toolbit, or buy a thinbit style toolholder, and then a 0.030 grooving insert.

They're not cheap. I had to go buy some from our local distributor during build this year, since we needed them ASAP and couldn't wait to purchase them online. Each insert was about $12.

The holder is probably $40-80 as well.

Ok, thanks. Good news is that our sponsors let us use their machine shop to build in so they just might have the holder or insert.

thanks, Vivek