Retaining rings and e-clips

In the past my team has used clamping collars to hold space shafts correctly and hold gears and sprockets together. However, these are heavy, burdensome to take off, and difficult to justify.

Has anyone used e-clips or retaining rings on their shafts to hold things in place? Any comments on their use, as far as ease of assembly, replacement, etc? I would think that they’d be the way to go if you have access to a lathe.

Yes, there’s always a set screw that can hold a gear or sprocket physically in place (or loctite, choose your poison), but i’m more looking for a way to get shaft alignment correct (i.e. a gear is 1.253" from bushing, etc.)

Gui i would reccommend you to test out a design with them, before using e-clips into use. I recently took apart a DEC Printserver/Printer. This had more e-clips and retaining rings in it then i could ever think of. Where most of the pullys and gears with-in the printer were, there were retaining rings holding them in place. I would say that they would work for your idea, i just dont know when a robot is smashing around, how well they would stay in place. I know they work in a static situation, but when momentum transfers is placed in the situation, i think you might find the problem of them shifting or falling out.

We used e-clips to hold the Chiaphua cluster gear in place in 2002. That worked pretty well. We had to ditch that drive system due to other points of failure though.

Something simpler (but not always the best choice - depends on your situation) would be to use aluminum spacers to take up space between components and keep them from moving axially relative to each other. This works great for assembly/disassembly. And you can easily add/subtract spacer width to make precise stackups. Doesn’t help you fix anything axially to the shaft though.


I think that there were some im the FIRST gearbox last year, maybe I am wrong. I know that they are used to hold the wheels on for powerwheels, and if you have ever taken them apart you would also know that means they hold the wheels and motors on. There are aluminum shaft collars, and even nylon and ABS plasic ones, so if you want to sue them for simplicity, then there are lighter alternatives than to using steel ones. Also to make it easier to pull them off just keep a few T handle allen wrenches in the correct size, then more than one person can pull them off, and there are a number of styles, the easiest to put on and off if you can is the 2 piece clamp on style. Look in McMaster there are a number of different styles and materials.

E-clips work OK for some things but they are really dependent on the correct size cut in the shaft (both depth and width). Retaining clips are used all the time for holding bearings in place. If you use them, have plenty of spares and always wear eye protection, they take off at high velocity if you slip and you will never find them when you need them.

Do not use the clips that FIRST provided. Unless I was putting them on wrong (and that very well may be the situation) they had a tendancy to mar the drive shafts. Also as the people pointed out above they did get misaligned from competition use.

However, these are heavy, burdensome to take off, and difficult to justify.

Which shaftcollars have you used? I have seen ones that seem incredibly simple to take apart. All you had to do was to take a screwdriver to them. (Note to self: Mcmaster is not the place to look for cheap robot parts)

e-clips don’t usually have the same retaining force as snap rings.

If you plan to use snap rings, get a special tool (available at auto parts suppliers) for removal and installation.

Don’t use either snap rings or e-clips when large axial forces are expected (as in a worm&gear drive).

Spacers are an excellent and potentially high precision method for retaining gears in place.

An alternative to snap rings, if you don’t mind the imprecision, is cotter pins (including hairpin cotter pins). You just need to drill the hole in the shaft through which they will fit. You might also find that a clevis pin and a cotter pin can serve as both axle and retainer.

If you put a shoulder on your shafts, you might accomplish your retaining needs by making an access plate. A super-simplification of the access plate is to put a threaded hole really close to where you want to retain things and then use the head of a screw (or a washer) to hold the parts together.

See attached picture, but we used 11 clip rings/e-clips on our transmission. Clip rings on the ends and e-clips in the middle of the shafts. We have used spacers in the past (like Ken suggests) and some spacers could have replaced several e-clips. We chose to use the clips. We never failed an e-clip/snap ring. And Al is correct, those things go flying when you take them off. We had hundreds of spares (very inexpensive).


One interesting thing about E-clips and Retaining rings is that they should be oriented on the shaft groove relative to the direction that you are
retaining the gear or collar. Take a close look at the clip or retaining ring and you will find that due to the stamping process that made them, the edge will have a radius on one side and a sharp edge on the other. Orient the clip so the sharp side is on the opposite side of the thing you are retaining on the shaft. Otherwise the groove may not be deep enough on some clips to hold in all cases and it will pop off sideways by spreading open! This happened to me once and I was nearly shot with my own motorcycle front fork parts landing from a jump.