Re: Integrating Encoder Into Gearbox
 

According to the product page (link's broken) the maximum TIR allowed is 0.006", so there's a bit more breathing room than that. Still not much though. I think the 0.0003" is the encoder shaft relative to the encoder, otherwise anything less than an ABEC-5 bearing could be out of tolerances.

Re: Integrating Encoder Into Gearbox
 

971 Encoder Mount Example Here

It's a pretty simple operation in the lathe - just drill undersize and then ream (as suggested by Austin). The doc you linked just establishes that the encoder shafts are made 2 to 6 tenths undersize, just means that you can probably get away with a 0.2500" reamer if that's all you have on hand.

You want a mount that prevents the encoder from rotating, and doesn't create any angular or parallel misalignment. The bent lexan design will allow the encoder to "float" a bit, which solves the parallel/angular problem.

Re: Integrating Encoder Into Gearbox
 

There seems to be an assumption that a basic lathe comes from the factory, and continuously maintains perfect alignment between the tail stock ram axis and the spindle axis; to allow perfectly on-center holes to be drilled.

The reality is it takes a somewhat experienced machinist with a test bar and a dial indicator to adjust the tail stock to be aligned perfectly laterally and vertically. The average FRC lathe is use is likely only accurate to 0.01 inch on-center.

Drilling center holes to the stated -0.0000/+0.0006 on center tolerance would be a non-trivial challenge for many FRC teams. To do it consistently you would need to use a collet holder in the spindle.

Re: Integrating Encoder Into Gearbox
 

Did the same thing on all my test robots.
Works adequately and allows me to use a wider range of encoders.
Less picky than encoders with the encoding wheel on the assembly shaft as well.

Re: Integrating Encoder Into Gearbox
 

You're confusing the shaft diameter tolerance with TIR. The H1 encoder has a maximum TIR of 0.006", and the shaft itself is between 2 and 6 tenths undersize (-0.0002 to -0.0006).

So the shaft diameter has a tight tolerance, but the encoder might have up to 6 thou of runout, an order of a magnitude larger than the shaft diameter tolerance.

In any case - using a reamer would give you a nice clearance fit, and then use a set screw/retaining compound/whatever to hold.

If your lathe is poorly setup, and doesn't drill holes on center:

1) Fix that
2) It doesn't matter - since the 1/32" piece of lexan holding the encoder will happily flex/float if the encoder has any axial/parallel misalignment. Same idea as using a helical beam coupler/flexible coupling that can deal with axial/parallel/radial misalignment.

Re: Integrating Encoder Into Gearbox
 

Thank you everyone for your replies! I really like the robustness of this design in addition to to how it doesn't require much sacrifice in terms of material in the load bearing part of the shaft. I used some 1 inch leg .75 inch tall 1/16" thick Z 6061 to support it and I think this will work very well thanks again!

https://drive.google.com/open?id=0B6...VpFZ05IY0lNLUE

Re: Integrating Encoder Into Gearbox
 

Many on the forum may think we are crazy, but for 2 years now we have been using the CUI AMT 10X series encoders set to max cpr. We have mounted them to Andymark, vex pro and custom gear boxes. The kit comes with every thing needed to mount them to several different shaft diameters. yes, the bottom housing is fragile if you want to disassemble the encoder. Digikey sells replacements. I was in a rush and had to replace 2. They have been rock solid.

Re: Integrating Encoder Into Gearbox
 

I would go for plastic instead due to the flexibility and ease of fabrication. 6061 doesn't bend well either, so you'll need to have a large radius on it or risk cracking.

Re: Integrating Encoder Into Gearbox
 

To add to that, we like lexan/plastic because you avoid putting much stress on the encoder.

Re: Integrating Encoder Into Gearbox
 

He was referring to the extrusion profile that you can buy, not bending your own sheet. You can use really thin aluminum to get the same flex as the plastic but the plastic is so much easier to work with.

Re: Integrating Encoder Into Gearbox
 

Adding onto that, we sheared the shafts off two encoders last year because we used 1/8" aluminum mounts bolted on with 10-32 screws. When push came to shove, the encoders lost. :o

I didn't know you could buy aluminum like that, that's pretty neat!

Re: Integrating Encoder Into Gearbox
 

If you measured the current runout of your own lathe you might be surprised. Most will be over the 0.006 value which was my point.

If your drilled off center; your applying a bending load into the resolver shaft every rotation with direct mounting. At 100 rpm your going to be challenging a floating mount, and getting higher loads in the resolver bearings.

This is the reason many of us prefer alternate non-direct mounting. For close mounting a no contact magnetic rotation sensor would make far more sense.

Re: Integrating Encoder Into Gearbox
 

We have two lathes, one that is so terrible it cannot make straight cuts of any depth (and I mean any depth) and another smaller one that belongs to a teacher. The teacher one was just bought this year and has runout of well under 0.001" with the stock 3-jaw, which I bored out slightly for accuracy. The larger one, for all it's junk, has only .003" TIR on the 3-jaw. I've gotten the tailstock inline with it once before to within 0.001", but the machine didn't hold up very well over time. I've never experienced a failure with plastic encoder mounts regardless of mounting, just because they are so flexible. I'm all for magnetic encoders, but as far as the COTS options go they are pricey compared to AMTs or similar.
If our lathe can do it, any lathe can do it. :P Seriously though, getting stuff within 0.006" is not difficult if you check it every once in a while. Grinding the chuck jaws and using a good indicator help immensely.

Re: Integrating Encoder Into Gearbox
 

Assuming you're talking about tailstock alignment now? This is one of those "fixing the wrong problem" situations. Just align your tailstock, it's really not that hard. Alternately, get a tiny boring bar and solve the problem in a different way.

Sounds like it works perfectly well for 971. I've always used helical beam couplers, or through bore encoders, no issue with either.

Re: Integrating Encoder Into Gearbox
 

If you mount everything tighyly, and try to make the assembly as simple as possible it should work just fine.

Are you trying to mount the encoders inside of the gearbox or on the outside?