Hex Shaft Encoder Housing Mounting

We are trying to figure out how to mount the new hex shaft encoder housings. It seems like a shaft collar is needed to keep whatever is adjacent on the hex shaft (wheel, sprocket, spacer) from pushing against the housing and damaging it. We usually use screws and washers on the end of the hex shaft but this solution does not look like it will work with these housings. Snap rings also seem difficult since most recommend turning down the shaft end to prevent deformity of the ring and hence removing the hex. Has anyone experimented with these and found a solution other than shaft collars?

For the REV through bore encoder. Using washers and a end shaft bolt is going to be fine. The encoder itself has internal bearings to support the hex so you don’t have to worry about pushing against it, as it will support itself.

Adding a small plastic
Hex spacer between the washer and encoder will make sure that the load is going to the bearings and not the face plastic.


If you happen to be using 3/8" hex output shaft from your gearbox, I’m wondering whether you could use these 3/8" to 1/2" hex adapters or these versahex adapters through the REV through bore encoder. It seems like it would work just fine and then any clamping loads will go through the adapters rather than clamping the encoder hex piece.

…or you could use what’s in the box from REV.


I assumed that the insert that is included in the box would attach to the encoder and not slide axially through the bore.

What I was trying to do was create a spacer that could you could use to create a clamping stackup for the wheel, sprocket, gear or whatever is clamped to the shaft and that the encoder could just slide on (axially) so that none of the clamping load was being transmitted into the encoder. I’m guessing the encoder can handle the clamping load, but if you get the spacing wrong between the encoder and the gearbox or bearing in the structure that you are mounting the encoder to, you could axially load the encoder one way or the other which could cause it to bind. I’m not sure how much endplay the encoder has and how tolerant it is of being loaded axially (which was the OPs original question).

The through bore encoder will handle normal clamping loads just fine. If you are doing anything excessive, what you are talking about above will work and any sort of adapter you make our buy will work with it.

One thing to remember is that this is a sensor and does have wires coming out of it. Putting it somewhere in your system where the shaft is just spinning will probably be of benefit. Sticking it as part of your sprocket/wheel stackup will probably work, but is less of an ideal sensor placement from a design perspective.

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What is the best way to mount the Rev through bore encoder to the AM14U4 KoP chassis (with TB mini gearbox)?

I can think of a couple of options, but I am not sure if these are the best ways.

  1. Using a Long Hex output shaft for the TB mini gearbox.
    I believe this should make it possible to mount the through bore encoder, but it is not clear whether the encoder will go in behind the motors or in between drivetrain rails.
  2. Changing the front or back axles to 0.5" hex from 3/8" round bolt given in the kit.
    This also involves changing the bearings and pulley and adding collar clamps in the end, so it may be more expensive.

Any suggestions are appreciated!

If you installed the long hex output shaft into an otherwise-stock AM14U4, it would poke out the external (bumpers) side. The AM14U4 does have a little space between the vertical plate and the end of the flange, but while I haven’t measured it I suspect you’ll need some additional material to pad out your frame perimeter (assuming such a concept exists in 2020) to ensure it clears and has protection. You may also need to trim the output shaft.

Yeah my team used the long shaft and you have to cut it down cuz it protrudes outside the outer plate

Thanks for the suggestion. I did not think of putting it on bumper side of the outside plate. I just looked at the AM14U4 outside plate CAD, and the flange width is shown as 0.75". It should be sufficient to mount the through bore encoder.

We have a guide coming out on how to do this, but one of the insert adapters that is included is for the 1/4 round protrusion o the back of the kit gearbox. You knock the small plastic part on and then mount the encoder. It fits between the motors and can be mounted by drilling one hole in the plastic case or by using a dollop of hot glue on the tabs.

It was specifically designed with this application in mind and you shouldn’t have to buy the longer shaft from AM.

On a side note if you did by the longer shaft there is plenty of space under the outside flange of the kit chassis for it.


Great! Thank you for the information!

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