I’m very happy to have discovered simpleFOC–I have a feeling it’s a much more appropriate way to do the kinds of rotation I’m interested in. But there’s something basic I can’t figure out: how does one attach the AMT103-V encoder to a hollow shaft gimbal motor like https://www.robotshop.com/en/ipower-gbm4108h-120t-gimbal-motor.html?
The side with the leads coming out is the stator. The other side is the rotor. The central hollow shaft moves with the rotor. You need to find a way of attaching the stator to the encoder and coupling the inner hollow shaft with the encoder.
The inner shaft is 8mm which is common - it is easy to pick up a spindle this size - your AMT103 might also come with an 8mm sleeve. Does it?
I guess you’ll need to work out how to fix spindle to rotor (glue, 3d printed part?) and how to fix encoder to stator (3d printed shim?)
You could even 3d print the spindle, I guess.
Yes, the AMT103 does come with an 8mm sleeve if I’ve read its datasheet correctly. But attaching a spindle to the rotor is the part I don’t get. I thought maybe there might be a set-screw hub with the same 12mm hole pattern but I haven’t found one. It’s interesting that you suggest glue and 3D printing. Is it common to have to create custom drive adaptors for BLDC motors? (I’m an electronics and programming guy if you couldn’t tell 
)
What load is your motor driving? Will the load be attached to a spindle (e.g. a gear) or are you going to attach load directly to stator?
How you attach the load might influence your decisions for spindle/coupling.
I bought a 3d printer a year ago, i think a lot of us print our own shims and test stands for motors.
Literally just some mylar decoration, almost no load at all, and so it can be attached in so many different ways because there’s nothing critical about it. Another user on this site claimed that hollow shaft motors made it easier to mount the encoder, so I am looking forward to see what he/she meant. Regardless, it’s good to know that 3D printing can be good enough for parts that take some stress. My 3D printed parts, not so much, but I’m inexperienced.
Let me pick your brain once more. Take a look at this motor. To me, it looks like the stator is on the bottom and the rotor is on the top, like the previous motor, but that the rotor has a shaft that descends through the stator and is accessible from the bottom. Does that seem right to you?
Hey @jlo,
The amt103s are very easy to mount if you have a 3d printer I agree. But you don’t actually need one for making a shaft. You can just use a long screw (M4 for example ) with few washers and nuts.
The great thing about the amt103 is that it’s robust and if you do 'ot center it perfectly it will still work. 
So this can be a good starting point.
Oh I see! I was worried that something like a screw with washers and nuts would cause friction with the stator, but I gather that isn’t a problem (or is easy to solve). Also good to know that the AMT103 is so forgiving.
Yup! Nice find on that motor. Looks like a practical shape, and 14.5Ohm resistance… should work very well with SimpleFOC.
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