Securing gears on shafts

[Dan Petrovic]

What you might want to look into in the future are keyless hubs (or that's what we called them).

They are kind of expensive and they can get pretty heavy, but we didn't have a single key for all of the round shafts we had this year.

We lifted trackballs with our arm with no slippage. Some of these keyless hubs are rated for absurd amounts of torque (for our application). Somewhere in the neighborhood of 700 foot-pounds, I think.

http://www.globalspec.com/FeaturedPr...54/0?deframe=1

It's kind of hard to explain, but there are two parts to each hub. An outer part and an inner part (the inner part is connected to the flange you see on the right-most surface. Each flange has a barrel sort of section with slots in it. The inner barrel has a taper on the outside of it, and the outer barrel has a taper on the inside.

The holes in the left flange are tapped, so when you tighten the bolts the flanges are pressed together. When the flanges are pressed together, the inner barrel is pressed farther into the outer barrel, causing the inner barrel to be squeezed inwards, clamping onto the shaft. The outer barrel "blooms" outwards, clamping onto the inside of whatever you're trying to get to spin with the shaft.

One thing to remember: You have to have very tolerances for this too work. If the hole in the gear (or whatever) is a tiny bit too large, then the hub wont clamp onto the gear. If the shaft is a tiny bit too small (I'm talking ten thousandths of an inch), then the hub wont clamp onto the shaft.

These things are very easy to use and if you do it properly, you wont have to worry them slipping.

[DonRotolo]

Originally Posted by dlavery

Grinding a cutting tool to cut a retaining ring groove is a fundamental lathe skill that you will want to practice.

This is a point worth repeating. Just because you can buy pre-made lathe tools doesn't mean you cannot make your own. In fact, there are times when making your own provides a far superior result. Making your own lathe tools is not at all difficult, as long as you follow some basic rules, and having that skill will serve you very well throughout your life.

Pre-made tools are best used when you need something that will last a long time, such as for a production run or an operation you'll repeat many times (like cutting screw threads). For short sample runs - and in FIRST, is there anything else? - unless you happen to have the right tool, grind your own.

FIRST is here to help you learn these skills. Go at it!

Over the years I have forgotten the details of most tools, but I DO know where to look them up, and that's just as good. I have a good tool grinding attachment for my grinding wheel, allowing for decent precision, and with just a little understanding of the principles, you can eyeball something if necessary. Pre-made tools in my shop are limited to 3 carbide jobbies and a parting tool.

Remember, you can use an e-clip even in a square shaft* - it's the groove that needs to be round, not the outside of the shaft. (*not recommended, but possible anyway)

Don

.

[M. Mellott]

Our team is a big fan of E-clips (OK, me personally). Work great for as thick as the are. However, if you just need to space out two gears in a gearbox, Delrin spacers would be better--no need to cut into the shaft.

[IKE]

Originally Posted by dlavery

You don't need to resort to expensive..
-dave
.

You just dispelled my NASA stereotype that your post would have started with:
Install the piece of billet into the 7 axis CNC....

Like Dave and others have said, learning to make your own tools is a great experience.

[Dick Linn]

A machinist recently gave me a small box of old high speed steel bits. There must be 30 of them, many ground into some very oddball shapes. One can only wonder exactly what turning/boring operation they were intended for.

[Andy Baker]

Originally Posted by M. Mellott

Our team is a big fan of E-clips (OK, me personally).

I agree... you will be seeing more of these on AndyMark products.

Andy B.

[Dick Linn]

We used to call them @#$%$-clips, because @#$%$ was what you said when one sprung off the carb linkage and fell down into the engine intake manifold.

[JVN]

Originally Posted by Dick Linn

We used to call them @#$%$-clips, because @#$%$ was what you said when one sprung off the carb linkage and fell down into the engine intake manifold.

I've heard people refer to them as "Jesus Clips", because when you remove them, sometimes "only Jesus can find them again."

[Dick Linn]

John, that was what I was meaning, just being PC. Nothing worse than having one of those falling into the intake manifold when you're working on a carb, or disappearing when you don't have a spare.

[Dan Petrovic]

Originally Posted by JVN

I've heard people refer to them as "Jesus Clips", because when you remove them, sometimes "only Jesus can find them again."

Yep, or that's what you yell when they go flying.

[Tim Baird]

Originally Posted by tdlrali

It's probably a good idea to locktite the setscrew, just to be sure

If you are going to Loctite it (which I recommend) try to use the blue variety. It'll hold, but you can get it off later in the heat of battle without working too hard. The red will just cause unnecessary frustration.

Speaking of being "in the heat of battle", I'm a huge fan of pinning gears, hubs, etc to shafts. If you're trying to install one and someone says "you have 30 seconds to be on the field", a drill bit and a quick 'snap' can work wonders, if anything to get you through one more match.

[IKE]

"LOCTITE THREADLOCKER 222 LOW STRENGTH PURPLE, 6 ML. TUBE (38653)

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Low strength threadlocker. Designed for precision metal fasteners under 19mm. Protects threads from rust and corrosion. Removable with hand tools.

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Nobody ever seems to use Purple. Not sure why. Grant Imahara recommends it in his Battlebots book Kicking Bot.

[vivek16]

Originally Posted by Tim Baird

If you are going to Loctite it (which I recommend) try to use the blue variety. It'll hold, but you can get it off later in the heat of battle without working too hard. The red will just cause unnecessary frustration.

Speaking of being "in the heat of battle", I'm a huge fan of pinning gears, hubs, etc to shafts. If you're trying to install one and someone says "you have 30 seconds to be on the field", a drill bit and a quick 'snap' can work wonders, if anything to get you through one more match.

Speaking of that, get a bunch of 3/32" bits. they're only 52 cents here: http://www.buydrillbits.com/products...?c=JL-USA-FRAC

Just invest in 40 of them. they're only twice the price of spring pins.

I am slightly kidding but it does seem like a good idea in a hurry
It would probably be better to use a spring pin.

-Vivek

[Dick Linn]

You can get a 10-pack of 3/32" bits at Harbor Freight for $1.49, not that there very good ones. http://www.harborfreight.com/cpi/cta...emnumber=93077

One think I find useful around the shop is to have some drill rod in various sizes. In smaller sizes, it is very inexpensive. You can get a 3 ft. length of 3/32" drill rod for about a buck. Larger sizes can be used for axles, etc.

http://www.use-enco.com/CGI/INPDFF?PMPAGE=789&PMCTLG=00

[Stephen Kowski]

I'm sure someone has probably mentioned this and I missed, but that's ok I'll jump on this dog pile nonetheless....

A very reliable method that has worked in the past for me is using pins in the hubs....buy a standard sized steel pin (one size should work for many, many applications so this is a one time investment you can use again and again)

this can be done pretty easily with a vice and a standard table top drill press

So for example if I had a quarter inch pin I would buy a bit two steps down on your handy ansi size charts (in this case a C drill bit will work; .2420) drill the .2420 hole through the hub (perpendicular to the shaft, not through the face of the gear) and then drill through the shaft where you want the hub to sit

repeat the same process with these new drilled holes, but this time use a reamer that is only one step down from 1/4" (in this case a D reamer; .2460)

now slide your gear on your shaft start the pin in the hole on the hub and use a press (or if you dont have access to a press, a hammer will work, notice I said it would work but may not be ideal) to force the pin down through the hub and shaft, stop once you are all the way through the hub

this is a very good connection; if it something you will be changing often I wouldn't try it, but if you just want something that you want to be permanent and you don't want to even think about it breakin/coming loose

Oh and if something somehow shears (has yet to happen to me)....knock/drill back out the pin and just go to a larger pin size using the same method.....

gl