Securing gears on shafts
 

Hello,

I was wondering if there were any ways to secure gears on shafts. I don't mean along the axis of rotation (that is easily solved by hex/keyway broaching gears or carefully welding). How would I keep a gear from sliding along a hex shaft if it was already broached to the correct size?

I have thought of tack welding, roll pins, spacers, and set screws in the place of roll pins.

I ruled out tack welding because it would be nice to be able to reuse the gears in a case of emergency, and I don't have the clearance in some parts for spacers.

I am probably going to resort to using set screws but I was wondering how some other teams secured their gears on shafts.

thank you, Vivek

Re: Securing gears on shafts
 

Get gears with hubs. Drill a hole in the hub, tap it, and setscrew the gear to the shaft. It's probably a good idea to locktite the setscrew, just to be sure :)

Re: Securing gears on shafts
 

unfortunately, I already got gears without hubs. I was wondering if there was anything like an e-clip for hex shaft?

thanks, Vivek

Re: Securing gears on shafts
 

You could still machine a snap ring or e-clip/retaining ring groove on a hex shaft.

You could also try one of those push-on style self locking rings.




Lastly, they sell clamping collars with hex bores which may work.

Re: Securing gears on shafts
 

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

Re: Securing gears on shafts
 

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.

Re: Securing gears on shafts
 

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

Re: Securing gears on shafts
 

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.

Re: Securing gears on shafts
 

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

Re: Securing gears on shafts
 

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

Roll pins should work fine.

Re: Securing gears on shafts
 

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...

Re: Securing gears on shafts
 

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.)

Re: Securing gears on shafts
 

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.

Re: Securing gears on shafts
 

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

Re: Securing gears on shafts
 

Special bit is a requirement sad to say

Re: Securing gears on shafts
 

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.

Re: Securing gears on shafts
 

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

Re: Securing gears on shafts
 

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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Re: Securing gears on shafts
 

I'd like to try these some time. They can securely lock a gear/sprocket/whatever to a shaft. preventing both slippage and side to side movement.

The best part? No machining or accuracy required :D the trantorques will expand to fill over-sized holes.

Re: Securing gears on shafts
 

He has already told us that a clearance issue exists (like in the AM toughboxes). The larger gear of gear cluster A (arbitrary name) is too close to the shaft of the large gear of gear cluster B for any spacer or collar to be added (The small gear of cluster B is on the same shaft as A). Please correct me if I am wrong, but this is what I am imagining.

A roll pin like in the AM gearbox is the least labor intensive solution I can imagine that doesn't have the possibility to move. I have used the press on retaining clips like Travis suggested, but they have the possibility of drifting (You could still use them, just be prepared to verify the alignment often). Snap rings would also work very well, have a lower profile than roll pins, and look better. They do require machining that is a tad more difficult, but still is a pretty simple machining operation.

Re: Securing gears on shafts
 

Yep, that's exactly right. I'm using AM gears and that is exactly the clearance problem I'm having. Thanks for clarifying.

It seems like roll pins would be the best way for me since they are cheap and we have a local grainger warehouse that supplies them.

thanks, Vivek

P.S. I had no clue how e-clips worked before this thread. Thanks for the information.

Re: Securing gears on shafts
 

If you are not looking for something super precision, you can kind of fudge a ring groove, I have done it before.

E-clips are nice for assembling after the fact (meaning while you are assembling everything at once), I was taught that if you can use a snap ring, use it, they tend to be stronger in the side to side load your talking about.

Re: Securing gears on shafts
 

Hmm. Since I am using hex shaft, wouldn't fudging a hole be more effective than on round shaft?

My side to side load should be very minimal. I will look at getting Eclips as well as roll pins.

Roll pins wouldn't require a lathe but e clips might be better.

thanks, Vivek

Re: Securing gears on shafts
 

Five piece set of HSS blanks for $2.99, including a cutoff bit:

http://www.harborfreight.com/cpi/cta...emnumber=40641

If you have to fudge a retaining clip groove (like using a hacksaw blade ground to proper width), I'd try to use a full external retaining ring and not an e-clip.

Re: Securing gears on shafts
 

If you have a good fit between the gear and the shaft you can use Loctite #609 (green). I have been using it on my gearboxes since 2004 with zero failures. Clean both parts with acetone and glue.

Re: Securing gears on shafts
 

We don't have a machine shop handy most of the time.... so I'd just grab a hacksaw, notch each edge of the hex shaft with it, and use a circlip or an e-ring in the notches.

To make it "round", you can chuck the shaft up in a drill press, start it spinning, and hold the hacksaw against it lightly by hand so your notches are in line.

Re: Securing gears on shafts
 

I got the sideplates milled out and attached the gears to the shafts yesterday using roll pins (spring pins). A few of them are too long and keep binding against other gears so I plan on grinding them down. Otherwise, they were very easy to use.

If anyone else plans to use roll pins, I would definitely recommend getting a roll pin punch like this one: http://www.grainger.com/Grainger/items/1Q760

It makes insertion a million times easier and prevents the tip of the rollpin from spreading out from the hammer. I had someone gently hold the pin with a needle nose pliers and put the punch on the pin and hit it with a hammer. It went in without any problems whatsoever each time. Without the punch I ended up bending a few pins.

thanks, Vivek

EDIT: thanks for all the information on e-clips, I will definitely use them in some of my other projects. I bet we could save a pound or two by replacing shaft collars with them!

Re: Securing gears on shafts
 

Please, NEVER EVER do this. This is a very unsafe practice. First off, the bearings in the quill of a drill press are not designed for side loads. There is a significant probability you will damage the machine if you do operations like this. But more important, there is a real probability that the hack saw blade will shatter and spray pieces of blade back in your face. Hack saw blades are not designed for repeated shock loads (like they would get when striking the edges of a turning hex shaft). they are brittle and being held under tension. As the blade repeatedly strikes the edges of the turning hex shaft at a relatively high frequency, there is a very good chance the blade will fracture and fail. And in these conditions, the failure can cause the blade to come apart in multiple pieces which may be thrown back at you or across the room at someone else.

If you need to make notches in a hex shaft, please do it safely and properly. If you don't have access to a lathe and need to do it manually, grip the shaft in a vice and cut the notches with a hack saw by hand. Cut the first one, rotate the shaft in the vice, and cut the next one, etc. It won't take that long.

-dave



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Re: Securing gears on shafts
 

On the subject of shaft collars, the Aluminum ones are very light and relatively inexpensive. The well made (USA) one-piece ones are only about $3. each. They fit much better than the cheap solid steel collars if the shaft is decent.

http://www1.mscdirect.com/CGI/NNPDFF?PMPAGE=3807

Re: Securing gears on shafts
 

Doh. I stand corrected. I guess I've done a little bit too much farmyard / garage engineering in my time :o

Re: Securing gears on shafts
 

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.

Re: Securing gears on shafts
 

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

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Re: Securing gears on shafts
 

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.

Re: Securing gears on shafts
 

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.

Re: Securing gears on shafts
 

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.

Re: Securing gears on shafts
 

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

Andy B.

Re: Securing gears on shafts
 

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. :D

Re: Securing gears on shafts
 

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

Re: Securing gears on shafts
 

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.

Re: Securing gears on shafts
 

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

Re: Securing gears on shafts
 

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. ;)

Re: Securing gears on shafts
 

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

E-mail this product to a friend





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

Applications: Set screws, adjustment screws, calibration screws, meters, gauges. "


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

Re: Securing gears on shafts
 

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. :D

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

Re: Securing gears on shafts
 

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

Re: Securing gears on shafts
 

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

Re: Securing gears on shafts
 

Unfortunately, no hub in this case...

Re: Securing gears on shafts
 

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.

Re: Securing gears on shafts
 

Yeah, I saw it on your drive train. It looked a lot lighter than shaft collars.

I didn't personally have the clearance for spacers but I'll consider putting enough clearance in for future gearboxes. I found roll pins the easiest way. A few washers here and there helped space things.

-Vivek