Adding motion to the simulator seemed like a really fun thing to do. Commercial systems are hugely expensive but I'd seen a few DIY projects online which looked like they would cost maybe $1 to $2k or about the same as a race weekend. So started thinking about designing my own actuators for a platform similar to the ones used in flight simulators etc. These can control motion with 6 degrees of freedom (6DOF) by allowing the platform to move up & down, left & right, forward & backwards, and also rotate along the axes of those directions too (yaw, pitch & roll).
I got to the stage of ordering servo motors and other parts and then came across opensfx.com which is an open source design for a DIY motion platform using their SFX-100 linear actuators which was ready to build, complete with all hardware and software and they even gave shopping lists for all the bits. It wasn't quite the full 6DOF platform I was thinking of but it was more compact, much faster to get going and videos I'd seen looked really impressive.
I modified the SFX-100 actuator design to use the motors I had bought and changed several other parts so that more compact, lower cost and more easily available 80mm profile could be used. I've now built the full system and have it working well with my sim rig. It pretty much worked first time (see EMI notes below) and was really funny to drive the first few goes with a VR headset. I was surprised at how quiet it is too as the first actuator I built made a fair amount of noise when tested on the bench. I saved about £200 overall on the parts by using the smaller profile and 80ST motors. Motors and all mechanical parts came from one very helpful supplier in China.
In keeping with the open source ethos of the original project I'm making the design freely available. I’ve christened this version SFX-80 for the obvious reason.
Parts list for one actuator:
- 80ST-M02430 servo motor 220V 750W with AASD controller. Ask for shielded leads to reduce problems with EMI.
- 1605 Ball screw 250mm long machined for FK12 ball screw support. Ball nut is 30mm diameter by 45mm long. Ball nut must not have flange!
- FK12 ball screw support bearing.
- Precision hollow shaft 30mm diameter, 20mm bore, 270mm long with bevelled ends
- LMEK30UU (30*47*68mm) linear bearing
- Coupler 19mm to 10mm. Coupler diameter 40mm by 55mm long.
- Aluminium profile 80×80 section by 190mm long.
- 5 x 5 mm square steel keyway cut into 20mm length for the ball nut
- 27mm ID x 3.5mm cross-section Nitrile O-ring for bump stop
- M6 x 100mm Stainless Allen bolts for motor mount (4 required)
- M5 x 65mm Stainless Allen bolts for internal piston (4 required)
- M8 x 30mm, M8 x 35mm Stainless Allen bolts for top and bottom mounts (4 of each required)
- M6 x 30mm Stainless Allen bolts for linear bearing (4 required)
- M5 x 25mm Stainless Allen bolts for FK12 (4 required) heads need machining down to fit FK12 or could use M4 x 25mm
- M8 Form B Stainless washers (8 required for top and bottom mounts)
- M6 Stainless washers (4 required for linear bearings)
- M5 nyloc nuts and washers for the piston assembly with washers (4 required)
The holes in the profile need to be threaded using an 8mm tap. The top and bottom mounts need threading with 5 and 6mm taps. You’ll have stronger wrists after doing a set of 4 actuators 🙂
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