Showroom Aluminium 3DOF (with Heave) Build Log

LATEST VIDEO OF RIG:


Hello again everyone,

Those of you who may have been following my old thread probably noticed some early sketches of a 3DOF simulator I'd been toying with. Well, here it is. Rather than posting updates slowly, this time I decided to wait until I had a working rig before posting my thread. I'll be posting the build process after this for those who are interested. I've been working on this for about 6 months or so, but I've still got a long way to go before I'm happy with it.

My old rig was a learning experience, but I really wasn't happy with how it turned out. It was too heavy, too big, and it would tip over if I didn't put weights on the back. The build quality was also about what you'd expect from someone's first real fabrication project.

With that in mind, I started drawing up plans for a new simulator. I wanted an extra DOF, but I wanted to keep the overall footprint of the sim a bit more compact, so I opted to add heave instead of traction loss (for now). Since I already had two PGSAW 25:1 gearmotors, I wanted to see if I could make a heave design work with the faster gearboxes (I don't think I've seen another build of this style that doesn't use the high ratio gearmotors). I also wanted the option of being able to switch between seat-mover and full-frame configurations for different simulations.

The final design ended up coming to this:



The wheel and pedal frames are detachable, making switching between the configurations as simple as undoing a couple of bolts.

Since I was using the smaller motors, I came up with an adjustable spring assist module that would help take some of the static load off of the motors when they're at rest:



I think I ended up underestimating how much torque the 25:1 boxes output. I'm using 1.2in levers for now, and it'll throw me up and down without breaking a sweat. Overall I'm pretty pleased! But there's still a long way to go.

PREVIOUS RIG THREAD:
https://www.xsimulator.net/community/threads/2dof-build-log-thread.7559/

Great job! Nice work on the heave module!
When you get a chance, add some pics of the heave module please!

I guess that's as good a place to start as any! Here's a pic of the finished product under the rig:


The pretension on the springs can be adjusted by turning the large nuts on the baseplate. The whole platform slides up and down on the 4 linear rails on the corners.

The two plates were made out of half-inch aluminium plate:






(not the best surface finish in the world, the endmill I was using was kind of dull and I think I didn't tighten the collet enough).

I also needed to make some stands to hold the linear bearings high enough to give the clearance I needed for movement, those are just some bored out pieces of round stock with holes tapped in either end to fit the screws that fasten them to the plate. The linear bearing slides attach to the top plate with the standard chinese bearing mounts (I plan on replacing the heavy steel bearing slides with carbon fiber ones and matching bushings later on).



Next I needed to make the guide rods for the springs, those are just some aluminium bar stock turned down to 0.5" diameter, with 3/8 threads on one end to mount to the top plate. The springs slide up and down over the guides, which keeps them from losing their form:


Next I made the adjustable platform where the springs will sit:
This just consists of a nut and a hollow threaded piece.



The hollow threaded piece allows the spring guide to pass through it, and the threads allow it to be moved up and down relative to the base platform. Doing this effectively allows me more or less spring assist, based on how compressed the springs are at the neutral position.

Finally, I re-welded my U-joint, then mounted it on top of the platform:

Awesome, look great!

Amazing centerpiece to a very well made rig, its a great showcase of skill.

Thank you very much!

Continuing on with the build log:

I also wasn't really happy with the CTC lever arrangement on my old sim. I wanted to play around with different lever lengths, but because the arm was just welded to a central shaft, that wasn't really an option. I also wasn't really happy with the fact that the motor shaft was hollow, since it limited the force I could clamp onto it with. To get around all of this, I designed a threaded insert that would be pressed into the central shaft of the motor, and that would allow different levers to be easily attached to it. The levers would bolt to the insert, and be held in place with a key.

I started with some steel round stock and turned the profile of the shaft down to size:


Threads were then turned onto either end of the shaft, and keyways were milled into the the side that would hold the lever:


Next the motors were taken apart, and the central shafts were removed:


The shafts needed to be bored out slightly to ensure a good fit:


Once that was done, the inserts were pressed into the motor shafts, and the shafts were put back into the gearboxes (the gears were cleaned and a fresh coat of lithium grease was applied before they were sealed up):

By far the most time consuming part was the actual frame itself. The whole frame is made up of about 60 pieces of 1.5"x1.5"x0.120" 6061 Al square tubing. Since I can never leave well enough alone, many of the cuts have odd or compound angles as well, and to add more adjustability, slots were added instead of bolt holes where applicable:

Finally some last miscellaneous mechanical bits:

I decided to make threaded inserts (kinda like weld nuts I guess?) for the ends of the connecting rods. That way my balljoints could simply be threaded in or out, and I could fine-tune the length without having to worry about precisely cutting my tubing:


The rods mount to the top frame through similar inserts (but this one's just a through hole, no threads). The relief cut into the face is just to help make positioning for welding to my tubing easier:


Next, the motor mounts. These are pieces of 0.5" aluminium plate that were plasma cut and then sanded to size. They've got a slight relief milled into the face to ensure that the motor is actually being clamped, and that the tube isn't just being crushed by the bolt pressure:


Aside from the CTC levers (don't actually have any pictures of those yet sadly), that about sums up all of the mechanical stuff that's been completed to date.


As for the electrical side, I'm using the same setup as my previous rig, along with the custom interface PCB that hooks up my MMs to my arduino. I'm using 2 650W LED power supplies from ebay. One is driving the rear motors, and the other is driving the front motor. I plan on adding traction loss to this rig at some point, so the fourth motor would also be powered from that second supply.



I've gotta put all of that into an electrical enclosure still.

As far as things that are left to do for the rig:

• Proper mounts for the wheel/pedals/shifter (you might've noticed my pedals are just held on with C-clamps right now)
• A proper electrical enclosure
• Longer CTC levers
• A set of castor wheels on Jacks to allow for easy transportation
• Proper cable routing
• Sanding and maybe painting the frame (if anyone has any good advice on how to "finish" aluminium I'm all ears)
• An automatic weight calibration system for the heave module

And larger things I plan on working on in the more distant future:

• Traction Loss
• Buttkickers
• A seatbelt/belt tensioner setup
• A custom handbrake and sequential shifter

That's basically everything I've got so far. I have some pics I haven't posted, and if anyone wants details on anything feel free to ask! I've also god CAD models of most of the parts on the rig, so if you want any of those I'd be happy to post them.

Great Sim, and a lot work involved to build such an excellent unit.
Anodized would looks great...

Hadn't considered anodizing it, I'll have to look into it. Thanks!

Very nice job. It seems you spend a lot of time building your sim !
Can you return the pedals to fix it on the upper frame to make a full mobile ?
Which one do you prefere ? seat mover or full frame ?

Yup, I've made a separate attachment so that I can easily convert from seat-mover to full frame. I haven't had the chance to try this one out in full-frame mode yet, but my previous simulator was a full frame. As far as personal preference, I think I like the seat-mover slightly better. I had a lot of problems with the frame mover throwing my feet up and down, which really broke immersion for me.

Ok Thank you,
I don't know yet which one I will build, at the beginning I wanted to build a full mobile but you are not the first one who prefere a seat mover (for car simulation). I may build one like yours so I can use the seat mover for races and convert it to a full mobile for plane simulation (wich may be smoother).

I've made another video that I think better demonstrates what the sim can do. It feels much better after taking the time to properly tune my axis assignments/profiles.



On another note, I had a strange failure from one of my hall effect pots the other day. The shaft bound up and made the pot slip, which caused my motor to drive the connecting rod full strength into the nut that holds the CTC lever on. It destroyed my MM and put a 30 degree bend into the connecting rod (thankfully I had spares of both). Oddly enough the sensor itself is still working fine after some fiddling/re-greasing. I guess some dust or dirt got lodged in there and the friction was too much.

@Tim McGuire - there are Hall effect pots available that are total non-contact. No binding or galling ever. You mount the magnet on the shaft and put the sensor on a fixed plate in the proper position. Not sure if it’s of interest but Littlefuse makes sensors that are $16 each (https://www.digikey.com/product-detail/en/littelfuse-inc/55300-00-02-A/HE608-ND/3929578) but haven’t tried them to know how well they work. The ones I used were Honeywell. They are more rugged and have integrated connectors that have turned out to be very handy as I’ve refined/changed/fixed things, but they cost more at just under $50 each.

On your sim, that spring plate assembly rocks! I love that you are doing a 3 dof with heave on pgsaw motors and have that nice of response! Very nice!

Great rig. Looks very smooth and quiet.

I would reverse the lateral and longitudinal motion on that rig. In the video it pushed you in the back when you brake, and vice versa. In reality the force would be opposite. Acceleration would push you in the back and braking would leave you hanging in the belts.

Interestingly had the same fail of my 180 degree hall pot and was able to fix doing the same fiddling.

Not sure how you can discern that from the video, clearly when he brakes the rear leavers lift, the correct response under braking.

If I were using something like a G-seat, you're correct that I'd want the seat back to "push" into me as I accelerate. But the conventional approach for small range of motion simulators is to have the seat "tilt back" as the user accelerates. The change body position, as well as being tossed back into the chair are what replicates the feeling the acceleration, not the pressure from the movement.