I had this crazy idea - Lets build a shock dyno with Linuxcnc

So now have this clear in my head. Here is a couple of photos of a shaper and a CAD design for one courtesy of my mate Chris..

This one uses a bolt in a slot as Andy proposed, nice and easy.


And here is Chris's CAD design in OnShape using bevel gears to adjust the stroke with some parts supressed.


And the little servo I have that is looking for something to do... Aussie 20c piece for size reference.


This is very cool to watch the animation running.

Remembering this was a crazy idea and is getting crazier, I was even wondering if you couldn't run a linear stage and get power to it via a slip ring www.aliexpress.com/item/32847470025.html...0.0.0.444d2e0etaJER7
This one has 12 wires so 2 wires to each stepper terminal for current handling would allow 4 wires for home and limit switches (but you'd really only need a single shared home/limit switch.

This one is metal and rated to 1000 RPM but I found some other plastic 6 wire ones with thicker rated for up to 800 RPM

Andy, you are crazier than I am!
There were some 6 wire ones with thicker wires (5 amps they said), good for 800 rpm. I'll look a bit more. Simple is good but a couple of zigbees maybe? Just send Gcode to a Grbl controller.

Next thing you'll want to be using an AC servo with mutiplexed step and direction signals somehow.

BUt if the stepper was under Linuxcnc control, life would be easier as it could be calibrated as if it was just another axis.

I think I've found a 6 wire 12 AWG one rated for 500 RPM. RPM is OK (800 would be better). The wires are big enough for the steppers and leaves 2 wires for a home switch. I think that is the way forward. I've got well over $1.5k in the motor and VFD so I have to use it now.

Do you think a NEMA 17 would have enough holding torque or would I need a NEMA 23?

Andy thanks. Took me ages to workout what you had done. After I dug in to your assembly I found a taper flange.

Here is what the side profile of my flange looks like



So welding a 16mm plate (with a hole in it) flush with the top face of the flange would be nice as there would be a groove for the weld.
The wide part of the flange is 20mm thick so it will protrude on the rear (motor side) 4mm and there is a 12mm parallel section to press your bearing assembly too. I think it needs to carry an encoder for the motor too so it might be a big bevel gear.

Pretty sure I could source them from Ronson Gears heare in Aus.

There will be about 35mm of room behind the flange so there is plenty of room.