Showroom 6DOF Motion Platform á la Knaufinator

Hello Folks, I've been so inspired by all of the cool designs and extraordinary talented people here that I feel that I have to build a platform for myself! It will use the excellent looking control system devised by Knaufinator:
https://www.xsimulator.net/community/threads/compact-ac-servo-6dof-rotary-stewart-platform.14769/

My focus will be on the mechanical design to make an aluminium version that can be bolted together. Also for use with VR (HTC Vive) Please feel free to make suggestions or point out mistakes I will aim to keep you updated with the evolution of the design and my calculations as I go

Also a big thank you to all of the people that very generously share their knowledge on here!

This is my design so far. My intention is to use the plate at the top for mounting the seat and aluminium profiles beams for the wheel and pedals. Wiring to pass through the central hole.

Photo showing one of my kids helping with my analogue method to calculate my CoG for seat positioning

Meanwhile, in spreadsheet world, it sounds like I need to be able to get some good speed (250mm/s) for this to work well with VR having found this useful reddit contribution from @noorbeast :
https://old.reddit.com/r/virtualrea...otion_systemsplatforms_vr_latency_and_nausea/
Does anyone have any experience with speeds and washout acceleration or jerk? This seems to be the biggest contribution to the amount of movement needed. If I use 250mm/s and washout of -0.12m/s² then the platform needs something like 250mm of movement. Acceleration doesn't seem to be such a big deal.

It's been a busy few months so I have some build photos to update the project. Starting with the servo driver Housing. The frame is made from 20mm box section steel with steel strips with threaded holes to mount the servo drivers and power distribution.

So after a few screwups, I managed to figure a way to get the ribbon cables nice and tidy, even though they're round the back you never see them!
The controller housing is complete now and includes cooling, an emergency stop and a glass front.

And the platform has progressed:


You can see that some of my welds are getting quite good...

and some are not!


For every good weld, I probably ground out and rewelded about 6 but it's coming together nicely now.

Also, I realise that the design has changed a lot since my first ideas. Machining parts costs about 2-3x fabricated (welded) frames and they're heavier. So I had to change my plans.

These are the rods that support the platform after I welded them up (it's improving but I moved them all to only show the good sides )

And with the rod-ends fitted. These are QA1 PCY rod-ends, which have a HUGE angularity - when the platform is running, I'll post a review on the durability.


I've been painting them tonight so I have some time to post these updates while they are drying and my garage stinks of paint fumes...

Seatbelts were from EBay - these were brand new but had expired their use by date so were super cheap


The frame is complete and ready to prepare for painting:


Some details showing the cones that connect to the tops of the rods and the seatbelt mountings.


This is the mounting plate for a vive tracker. I wanted it to be attached to a rigid part of the structure so I added this 'sting' up the back. I think it can be useful for running all of the wires to controllers and headset.

Rod-end attachment detail. These are 1/2" bolts.

It's taking me a long time to build the platform but I wanted to test the motors and all of my wiring so I built a lightweight wooden version. This is the first time I had it working correctly, it was an exciting stage to get to!


And then with the help of my children I tested it with Simtools and PCars2


Also a big thank you to everyone who posts on here and keeps my inspiration going when the project gets on top of me

I've made some good progress lately. The base is fabricated from laser-cut steel parts that are welded together to make the motor mount pairs:


Then these are welded onto the base plate, which is ½" steel:


Some of the welds are even good enough to show :


And the base plate sits on the base frame, which has wheels so I can move it around:

Emergency stop circuit is now wired up. It uses XLR instrument cables so can be easily extended.

Seat/platform is now complete for now. I'd like to add pedals and steering wheel but that's going to have to wait until I can afford them. Priority is to get the system working and tested.

I also started the assembly of the base:


Hall Effect sensor brackets are made from stainless steel:

One of the fiddliest bits was fastening the gearboxes into the base. I need to keep the fastener heads low to clear the lever arms so I wanted the 'nut' to be on the inside. I tried a few different types of nut but there was no access to hold the nut while tightening it - I blame the designer
In the end I used corner anchor nuts:

These were superglued in place, which was just enough to hold them while the thread engaged, then after the bond broke the shape meant they were prevented from rotating while I did the nuts up. The anti-rotation worked in both directions so they can be undone easily as well. I was happy with this solution after a lot of head scratching!

I used ½"UNF screws in the Ø6.5mm holes, which allowed a bit of wiggle room.

These are the gearboxes: https://www.aliexpress.com/item/32967571001.html
These type of anchor nuts: https://www.ebay.co.uk/itm/NOS-1-4-...Nut-MK3001-B4-qty-10-N-1-MS21074/184034726659

well done on the fabrication work! looking forward to seeing this ready!

Thanks Ian - it's been a very steep learning curve. I can't wait either!

Lever arms were the bit I found most difficult in terms of having a cheap, reliable design that was accurate enough for what I wanted. I was quoted £300 to machine a single aluminium arm that would have a close fit on the gearbox shaft and also clamped to the key. I'll post separately about that design because it might spark some ideas but for me it was too expensive.
After a lot of thinking, I came up with a relatively cheap solution that I think satisfies the requirements, using a keyless locking bush:

https://www.transdev.co.uk/hardware...es/translock-standard-keyless-locking-bushes/

There were two main parts to mounting the lever arms:
- modifying the gearbox output shaft
- making the arms

The locking bushes use a double cone arrangement to clamp onto the shaft. I thought the loads might be high enough to deform the keyway if it didn't have a key in it:

Standard key size is 6x6mm so I ground the keys to 3.5mm thickness with this setup so that the slot would be supported but the key wouldn't stick out too far and stop the locking bush going on:

It was a bit sketchy but it worked!

I also drilled an tapped an M3 hole through the key to help me remove it: