Showroom Smitty's Rotary Servo 6DOF build (Complete!)

Hello everyone!

I built a pc for VR MSFS about a year ago, and started to look for motion platforms over the summer. I've been lurking here since then, gathering ideas and whatnot, and started designing a 6DOF rig. My background- I am a mechanical engineer with almost 20 years of servo-based machine design.

The best part, there is not going to be just one! Two friends of mine are also building my design so we are ordering parts in triples and will be welding and building together. We each have a bit different preferences on what sims it will be used for- Me primarily VR MSFS with plane and helicopter controls, and one friend will be mostly planes, and the other will be primarily for car racing with higher end Fanatec peripherals and a big wide screen.

After many redesigns, I finally have something worthy of a build thread!




So far most materials and parts have been ordered for the base. I am using 750W AC servos and 50:1 low backlash gearboxes, run by a Thanos controller thru FlyPT Mover. I plan on using OVRMC to get the motion compensation for my Pimax 8KX, if that fails i'll resort to a mounted tracker or controller.

The servo crank arms are 200mm long, (with extra holes for 180mm and 160 in case of some miscalculation)! Links are 550mm, arranges on roughly a 900mm circle. The bare upper frame will weigh about 60 lb. Motion limits should be about +/-150mm on linear XYZ, +/- 20deg roll and pitch, and +/-10deg yaw.



Right now we are waiting for base sheetmetal to get started with welding, and have a quote out for the upper frame tube cutting and bending. Some nice features will enable quick changeover from plane to car setups. The pedal plate will slide in on 80/20 rails, and we will have multiple plates for screwing down the pedal set permanently to that, and then just slide in and clamp gas/brake/clutch or rudder pedals. The steering wheel bracket will be able to rotate 120deg toward the front to get it out of the way for a floor-mounted flight stick.



Here are some pics of how the design progressed since August:

So as the build progresses I will post pics and updates. I look forward to everyone's feedback!

-smitty

The model looks awesome. Looking forward to see the build

Good idea!! You've spent some time modeling this, great!

- The round tube bending/welding could be very difficult, though.
- You should leave some space next to the clutch pedal ("dead pedal") to lie your foot while not clutching as in a real car.
- How will you climb into it? handbrake, stick, gearbox... maybe a guard-rail opposite side of the seat to grab it?

We're having the raw steel plate & tube cut & bent by job shops, so that wont be an issue. Plus one of my friends on the build runs a machine shop so there wont be much we can't do!

Good idea on the dead-pedal. The 8020 there should make having a plate fairly easy.

& good eye on being able to get in the thing!! I have been looking at the whole assembly in VR, at actual size, which really helps see things like that. Thinking of a step like this from the more 'open' side:
the flight stick is made of 20mm extrusion and just slides straight up out of the way. I'm using it now on my 'motionless' flight chair:

Got all the motors/gearboxes wired up. I think i have all the right settings but they seem to be moving slow, and not the full angle specified in mover. more investigations needed......


Printed up some test arms, and a long 1/4" bolt provides a homing stop. Here's the STL if you're interested:
https://www.thingiverse.com/thing:5170204

You did set the actuator type as rotary type, right? Can you show the settings in the AMC LCD menu? to make sure you have proper settings..

Thanks for looking! Here's my settings. Also, Pn098 is set to 20, to match the 500p/rev. Gearboxes are 50:1. motor is 80ST-M02430. individual settings shown are identical for each, but since hardstop is cw/ccw for every other servo it splits them up.


Looking at these again, is setting Degrees redundant? I am telling this 98 and then telling flypt 98...
i dont know what buttons speed does.

Here is my design geometry. I have a hard-stop for homing (currently have Pn024 set to 8 so i dont bend off the temprary screws) and park pos/spd is 1/1 (forgot that pic).


Here's what i expected (red) vs. what it's doing (green)


And here's how i was conducting the test in flypt: (just moving Heave, ignore "world z", just for loop test)


Also the servos seemed to lag behind the flypt graphic by quite a bit.

You have to set the degrees from 98 to 180... must match the degrees of FlyPT.

How much degrees you get using the UP/DOWN buttons? Also the button speed can be adjusted if the manual buttons move the motors too slow.

Ok, i set the degrees to 180. Definitely getting closer, but still off..

Does the 'Range' entry in flypt need to also be 180? I don't want it to go that far.



So that seems to be ok.? But once i connect to FlyPT it doesnt seem to do what i want. First, the "middle" position is way off. I have no idea how it's arriving at this number.



Second, the full-heave range still does not match up (but its lots closer than before, when i had degrees at 98)



** Important question - Am I correct in making a hard-stop for finding servo home? Will that arrangement prevent some motion positions? The base plate is in queue in the shop; need to know whether to cancel some laser cuts on it for the hardstop positions.

I see others using sensors, i thought i could avoid that hassle. But large combined moves go way past my -49 lowest heave, right through the stops, and FlyPT doesn't flag it as impossible:



So thats where i am now.. once i can trust the angle measurements then i can start to worry about the slower speeds that it's doing.

@smitty , been busy, but from a fast read:

You can set the range to 180 and then add actuator filtering (in the rig module) to limit them to the range you want.
Something like CROP(VALUE;-100,170) that limits it to a range from -100 to 170.

Edit:
Remember range is half of the travel.
Range=180 means you can go up to +180º and down to -180º
Travel = 2*Range

been a while since last post, but good news! got base parts in! time to start welding

Hey @smitty

I like the thorough, well thought-through approach. It looks like you are always planning a couple of steps ahead before starting work on a section. A pleasure to read!

Also, the fact that you are building this as a group of three friends sounds super fun and will allow you to spread the unavoidable hardships of such an undertaking evenly among the three of you.

Keep us posted on how it goes and share some videos when the time comes, will you.

Cheers,... Dirty

Finally got into the shop to start welding! Haven’t used a MIG in a while but was quick to relearn. This was all we could do today, got to get some of the legs and little pieces cut for the rest of the base.

Been busy making some of the base components, so not too many exciting pics, except for this one! The main upper frame tubes showed up!
Also got a really cool seat belt. Apparently it’s used on a military MRAP, it’s a 4-point and has inertial retracts, but also has a little lever for locking the retracts completely. The NSN is 2540-01-557-6664 if you’re interested and at least 2 companies make them.

Another day of welding!!

Going back to the shop tomorrow evening, probably will be cutting tube for the links & welding threaded bungs on

More progress! We painted the frames in true Polish Firing Squad fashion, which was deemed funny by my 3rd friend, who had come out to show us that he finished some of the tube bung welds... Unfortunately i had to point out he welded 2 left-hand bungs to one tube </facepalm> so he had to cut them off and redo them!

Far from it! We still have to start the upper section, and we're waiting on some laser cut & bent sheetmetal for it. We're working on some more bits tomorrow, finishing up the push rods. I think I'll be bringing a base weldment home soon, since a fully assembled one will be reaaally heavy to move to my basement.

Got in the weld-on pieces for the upper frame. Started work on the foot plate holder. We have 2 foot plates each so itll be easy to slide out the plate from the 40mm extrusion, for switching from car to plane pedals