High angle & Displacement 6DOF

[DoctorD]

Hi again X-Simmers

Well, it looks like I've gotten the bug... ...again.
Haven't even finished my first simulator and I'm on to the next. This time a 6DOF with big ambitions:
300kg rated platform capacity
+/-35 degrees pitch roll and yaw
+/- 250mm heave, surge and sway (500mm total travel in each displacement axis)
...and FAST!!!

To do this I'm gonna need BIG motors and STRONG gearboxes.
After some pretty solid research and design (massive thanks to Thanos/TronicGR), my shopping list was as follows:
6x 1.5kW induction motors (1400-1800 RPM)
6x 2kW programmable VFD's
6x 400Nm (or greater) rated gearboxes at around 1:50-70 ratio (24-30 rpm at the output)
Big torque arms from the gearbox (I'm going for 300mm lever arms)

I've also adopted a design that allows for modification to the platform geometry and load characteristics. This means I can keep it light and have some really wild motion with just a VR setup, but also load it up somewhere in the vicinity of 800-900kg at the expense of some travel and angular displacement.

Thankfully the internet has been kind and I've managed to source most of the big gear at some pretty crazy prices (I REALLY love eBay and Aliexpress!).

So far I've used Autodesk Inventor and AutoCAD for geometrical design, whilst Fly-Elise's 'Motion Platform Designer' is great to determine just how much I can get away with power & torque wise whilst sticking to the design scope.

EDIT: Current design image and photo of progress

PaintedForTesting.jpg (116.53 KiB) Viewed 26423 times

PlatformScreen.jpg (61.08 KiB) Viewed 27110 times

BluePitched2.jpg (114.55 KiB) Viewed 29671 times

Here's a quick pic of the preliminary design...

Prelim.jpg (135.86 KiB) Viewed 30207 times

Be well guys,
DoctorD

[Riton]

Big !!

[DoctorD]

Getting excited as things start to arrive in the post...

6x 2Hp 3-Phase motors - Brand new surplus stock from eBay ($80 each)
...and yes, the output shafts are very long. But nothing an angle grinder can't fix

Motors.jpg (184.33 KiB) Viewed 30037 times

6x 1.5kW single phase -> three phase VFD's (Delta brand) ($200 each)

VFDs.jpg (204.47 KiB) Viewed 30037 times

6x 300W braking resistors to help slow the motors down for fast oscillations ($30 each)

Resistors.jpg (204.72 KiB) Viewed 30037 times

The gearboxes are being made in China at the moment (60:1, 450Nm, dual output shaft) ($150 each)

Gearbox.jpg (78.2 KiB) Viewed 30037 times

I am also getting some custom pieces made in China:
6x Torque arms ($40 each)
- 304 Stainless steel
- Variable length (100mm, 150mm, 200mm and 250mm connection points)
- 25mm thick, 340mm long, 75mm wide
EDIT: Torque Arm thickness and width changed slightly (24mm and 72mm respectively)

Torque Arm.jpeg (63.44 KiB) Viewed 30037 times

12x High misalignment inserts ($4 each)
- 303 Stainless steel
- To go inside my upper M20 rod end bearings to allow for +/-40 degree rotation (needed to give the platform pitch & roll I want)

BearingInsert.jpg (30.98 KiB) Viewed 30037 times

I've also got a ton of little bits n pieces arriving (electrical gear, fasteners/joints, etc.) all thanks to aliexpress. Can't recommend enough.

The next big thing I'm excited about is my 220Amp welder (Combo MIG, TIG, ARC). Should be in tomorrow...
Can't wait to put that 3 day welding course to some good use.

[DoctorD]

I might also mention this little gift from the gods...

My Oculus Rift DK2 finally arrived!!!

DK2.JPG (108.96 KiB) Viewed 30036 times

[Stevant1]

Hey Doc,

This all looks great. I'm going with triple monitors myself since I already have a chair setup, but the DK2 is on my list. I had a DK1 but the resolution was not working for me. I see they have made some great strides in the tracking and the resolution. Keep me posted as I might be following you with that concept.

Looking good, keep us posted!

Stevant

[Riton]

why not use simple rings for ball joint spacers?

[DoctorD]

Thanks for the feedback Riton,

I went with the contoured misalignment spacer to maintain as much material in the piece as possible. I'm pretty much mimicking the same design as used in the car manufacturing industry (just google "high misalignment bushings" and you'll get an eyefull of what's used commonly).

At $4 a piece it's pretty crazy not to go for something as robust as this. Especially when I might be throwing hundreds of kilos on the platform with nearly 80 degrees of rotation in pitch and roll (+/-40 degrees from the horizontal). I'm imagining some pretty 'healthy' forces at play when at full speed.

The best feature of these inserts is that I am able to maximise the amount of material in the sharp edge of the piece (directly adjacent to the flat/cylindrical section). This means there is maximum ability to restrain lateral forces reative to the rod end bearing central axis, and minimal chance of shear failure in the sharp flange.

Here's a picture of them at the manufacturer to see just how fine the edge needed to be at the flange. That kind of machining is certainly beyond my abilities

[DoctorD]

...the beauty of having the bushes made to within 0.1 of a millimetre means that I can acheive platform angles like the one shown below (whilst still having the mechanical ability to add a significant amount of other rotations and displacements to the platform whilst maintaning the 40 degree pitch depicted in the image).

HighAngularDisplacement.jpg (85.55 KiB) Viewed 29941 times

[Riton]

ok, thank you, I did not know I'll get in France if I find.
apparently it is all done.
actually it is not very expensive.
very nice project!
I like the concept.
the motors supports are adjustable?

[Stevant1]

Hi Doc,

Here are the one's I am using with a similar flange. I agree with your thought process in regard to the amount of material at the end of the flange for strength, yet thin enough towards the ball for clearance and maximum angle.