[WIP] 6DOF on hoverboard motors and SFU gearboxes

Hi, I'm finally making my dream come true and started building my own 6DOF sim for flying DCS and MSFS.


It's frame is inspired by FullMotionDynamics compact platform from 2013


And gearboxes are inspired by DofReality's SFU gearbox upgrade







So... THE FRAME:
This was the biggest concern holding me back from starting, because I couldn't imagine how I will make this.
I can't weld, I don't have any place to weld, and letting it for someone to do will be too expensive of course.
I considered making it from T-slot aluminium profiles, but it would be too expensive and heavy. All those brackets and bolts loosening with time... nah.

So I bought a TIG welder and started learning how to weld
TIG doesn't really spark, and arc is so small and precise I could weld this in my basement with paint fume extractor.

The frame will look like this, made of 32mm and 38mm stainless steel tubing. I'm practicing my welds and while they may not be pretty, they will surely hold.

A grinder and paint makes me the welder I ain't!




MOTORS:
Recently I've built my own FFB stick and rudder using FFBeast firmware and hoverboard motors, and then thought - those motors have parameters perfect for motion rig. But they are built weird, with wires going through the shaft, and motor drum being not very suitable for attaching any shafts to it (in the stick the gearing is different, and motors don't even make full rotation so I left phase wires twisting like that, this however would not work in rig, where actuator's motor need to make few full rotations)







Then I found a youtube channel from a guy who modified this motor to look like popular outrunner to use it in DD wheel:

So I designed simpler backplates for motos and ordered them on PCBWay. Original ones from CNCDan's video would came out too expensive - too many machining operations.




Then I cut the motor drum on a lathe, drilled 6 additional holes, bored out original front plate, and put large additional bearing into it.




Motor's stator needs to be held by something so I printed these brackets from PA6-GF. Long screws will go through whole motor lenght to hold it to the mounting plate.



Then I made custom steel shaft on a lathe and put everything together with some aluminium brackets to mount the AMT CUI 10-E2 encoders. So this is how it looks assembled:




Motors came out very cheap. I bought 6 used identical ones with 25mm magnets for around $75USD.

GEARBOXES:

Hoverboard motors have around 16KV, and they will be running on 48V. That's around 700RPM with load (probably)
I need gear ratio something like 30:1. Planetary gearboxes, even from Aliexpress were still too expensive for me, and they could have too much backlash and cause problems later. I considered belt drives like in my FFB stick, but I would then need to print gears, since large ones are expensive too. Not to mention possibility of teeth skipping.
And I don't want linear actuators because it takes just too much space and I have small room.
Then I found that DofReality made it's P6 rig with new clever gearboxes that utilize ball screw, but changes their linear movement to rotational. Short SFU ballscrews can be bought cheaply on Aliexpress, so I bought one kit with bearings and started experimenting.







And this is finished actuator. It has gear ratio around 28:1, total range around 31cm. Arm lenght to mounting point - 21cm. Speed without load is around 600-700mm/s

The driver running this will be Makerbase ODrive 3.6. One for 2 motors, so 3 of them for whole rig.
I measured force one actuator can apply and on 20A current limit set on ODrive it was 94kg. NICE. Total amount of power it pulled was 183W, measured on plug-in power meter.



Now the electronics box.
3 ODrives arranged in a triangle in the middle of all actuators. I printed something like this (I will cut aluminium heatsink/mounting plate for brake resistors later):







And put LED strips inside because it started to look like Iron Man's arc reactor.






Overall the cost for whole rig with motors, electronics, power supplys and TIG welder will be around $3000USD.
That's all for today. I'm now modding the rest of hoverboard motors and making actuator frames.