Wooden 2 DOF Sim with integrated G-Seat, Fans, and Vibration

With this and the next posts I will provide some more details.

At first about the electronics part:

In my first approach I had my 3 JRK 12v12 boards and the PSU mounted on a little wooden plate behind the seat, as shown in this picture:


The first problem with this was that other essential parts, like the needed USB hub and the multi socket were lying loosely around the rig.
The second problem was that there was no room for new parts, like a 4th JRK board, a second power adapter for the steering wheel, etc.

Now here is my second approach: It is a kind of drawer that I can slide inside a box below the seat and that holds all required electronic parts.
This is the drawer:

And this is the box below the seat:


The electric connections between the electronics drawer and the rig is done via two 6-wire and one 8-wire power connector that can easily be plugged in and out. The connector cables are long enough for operating the rig wih the drawer outside (for maintenance purposes) as well as inside.


On the outside, the drawer has a switchable power socket that powers the multi socket inside. Switching the power socket on starts the PSU and the fans. The second switch below forwards the power from the PSU to the JRK boards. For this purpose the PSU has 2 connectors. Separating them keeps the PSU fans on, but no power is provided to the JRKs.
And finally I added a USB plug to the outside of the drawer, which goes to the USB hub inside.

In this way, connecting the rig is limited to just plugging in a single power cable plus a single USB cable. After usage, I unplug these and roll the rig into a corner of the room.

This is another thing I did: I mounted 6 rolls below the rig, so that I can easily move it around.

And here are some more photos, which will be all for today:

Rear view:


Front view:


Oh yes, and this is something that I added after my first test run last Friday: a set of bungee cords.


Before adding these cords, the motors were not able to bring the seat back to an upright position after a full-angle roll.
The cords do completely solve this issue.

So that's it for today. I am really happy that I can fly again and in this way have some breaks between the next building steps, which will be:

• making "heave" work (mostly done: 4th JRK already in place, connected to the "heave" motor that is mounted on the moving seat, and properly configured within the JRK config utility)
  
• adding my vibration motors and fans for air stream again
• mounting the steering wheel again. Well, still need to find a good way for where and how exactly to mount it.

My rig grows bigger and bigger. Last week I mounted the front part with the steering wheel and the three fans, and with this add-on the length of my rig grew from 140 cm to 165 cm. Now it becomes difficult to park it in a corner of my room, and so I am thinking of how to reduce the length.

My idea is to replace the shoulder mount by a foot mount. In this way I could move the seat with the underlying electronics box to the back of the base plate, reducing the overall length by about 35 cm.

Thing is that I am using the 200W motors from motiondynamics with the default 25:1 gear box, and their torque does not seem to be sufficient for a foot mount.
And since I actually don't want to spend 400 € for two new gear boxes, I plan to use these sprockets for building a 1:4 chain gear.


I already widened the hole of the smaller sprocket from 8 mm to 1/2 inch, so that it fits onto the motor axis. Next I will drill a hole into the big sprocket for holding the rod joint. This hole will have a distance of about 4.5 cm from the axis.

Motors and gear will be mounted at the front and connected to the seat base below the throttle & stick components. I hope that this mechanism will have enough torque for driving the rig.

Hi @MarkusB , good to see your having fun building your sim. Having used chain drives myself for driving a surge and traction loss table in my old sim, don't forget about chain bounce - also safety guards .

Thanks for the hint, @SeatTime. I will keep this in mind.
Yes, it is fun building the sim. But at the moment I would also like driving it, which I currently only do in my mind.

Yesterday I finished building the two 4:1 chain gears that I mentioned in my last post. The purpose is to increase the torque of my 2DOF motors, so that they become suitable for a foot mount. In this way I will be able to reduce the size of my rig, so that it hopefully fits into its „parking lot“ in the corner of the room.

Here are some details about the gear system:

I am using a 3/8 inch chain and sprockets. The small sprocket on the motor axis has 10 teeth and the large one 39. The small one originally had an 8 mm hole which I widened to ½ inch, so that it fits onto the motor axis. (I am using the 25:1 hollow shaft gear box, and my axis is a ½ inch threaded rod.)

The large sprocket has a 16 mm hole. For whatever reason this is not a standard size for the inner diameter of ball bearings. Instead, the standard diameter of ball bearings is 17 mm, which in turn is not a common size for threaded rods. I am sure that there is a higher logic behind this standardization, but I did not take the time to check this out.


However, luckily I found brass sleeves on ebay, which have an inner diameter of 16 mm and an outer diameter of 17 mm.

After sawing it open, it matches perfectly onto the 16 mm axis and at the same time into the 17 mm ball bearing.


The following pictures show how I mounted the larger sprocket. As usual, I used 18 mm multiplex birch plywood and strong metal angles.


And here is how I mounted the motor:

At first I screwed two metal bars with 8 mm screws onto the base plate. The holes inside the bars are threaded, so that the screws are absolutely tight.

Then I put a rubber layer onto the plate, which I cut from an anti-slide pad that you typically have in a car trunk.

I pushed 6 mm threaded rods through two of the three mounting holes of the gear box, and positioned the motor onto the base plate in a way that the rods reach over the metal bars.

I added a second rubber layer and on top another metal bar (this one without threaded holes). This second bar is pressed against the rods with 8 mm nuts.


The idea behind this construction is that the motor is adjustable while the nuts are loose, so that I can tension the chain by simply moving the motor away from the large sprocket. And after tightening the nuts, the motor is absolutely fix. The rubber layers are meant for providing a good grip between the 6 mm rods and the metal bars, so that they do not move even when there is force on the chain.

On the following picture you see the joint for the rod that will connect the sprocket with the seat plate of the rig. The „lever“ length is 4.5 cm.


Finally I mounted the pot. As with my original 2 DOF construction (see above) I connected it to the axis via two module 1 sprockets. In this way I can easily disconnect the pot from the axis by moving the pot angle, e. g. in order to adjust the motor position.

First I had concerns with connecting the pot to the axis of the larger sprocket, because I thought that this axis would have more backlash than the motor axis due to the chain in between. But luckily the backlash is exactly the same, and it is still limited to the inevitable backlash of the gear box.

I can’t wait to finish the construction and get my rig moving again, especially because of the eagerly awaited SimTools 2 version which I want to test. And then I promise to finally create a video.

In the meantime I mounted the motors with their new chain gear onto my rig and did some PID adaptations and testing.
It is working great. Torque is absolutely sufficient.

The only thing I had to work on was improving the mechanism for tensioning the chain. The way I described in my last post was ways to weak, considering the force that it working here.

My new solution is this:

I am using two 4mm steel stripes (see red arrows) and put them between the motor gear box and the wooden parts that are holding the big chain wheel.
2 8mm threaded rods go through the steel stripes, and on each one sits a nut (see yellow arrows),
With these nuts, I am pressing the motor away from the big chain wheel and in this way I am tensioning the chain.

Now the tension is not releasing over time anymore.

Here are some pictures of how the motors are mounted and connected with the seat base.

Third DOF Added!

It's done: Now I have a working Heave DOF on my rig!

I started with it back in October last year:
https://www.xsimulator.net/communit...ation-for-oculus-rift.7684/page-3#post-116125
It is a combination of seat flaps (similar to a G Seat) plus fabric belts that move along the back of the seat.

About the flaps: -My first approach was to move them with steel cables, as you can see here:

This did not work, because the cables were loosening over the time.

For this reason, I replaced the cables with a construction of steel rods:



The pot is connected in the usual way:


Now about the belt system:
When I was flying some time ago, I recognized that during take-off I felt the fabric of the seat back move against my back.
Positive heave force: I am pressed into the seat, which (1) increases the pressure against my bottom and (2) moves the seat back against by back in upwards direction.
Negative heave force: I am lifted up from the seat, which (1) decreases the pressure against my bottom and (2) moves the seat back against by back in downwards direction.

Well, the force on my bottom is done with the flaps.
And the movement of the seat back against my back is now donw with my belt system:

The belts go around the parts of the former pancake roll, where I fixed them.


From there they go around a rod and then up along the outside of the seat, through the harness holes, ...

.. down on the inside of the seat and finally back to the pancake roll.


A movie will follow.

Improved Vibration

I did some experiments with adding vibration to my rig a long time ago by simply putting 2 vibration motors onto the seat base.
Here is my old post where I explained it:
https://www.xsimulator.net/communit...ation-for-oculus-rift.7684/page-3#post-114278

I really liked the method, but only these two single points of vibrations needed to be improved.
And this is what I did:

I bought a complete massage pad for car seats with 5 motors inside, two in the base part and 3 in the back part. And then I did some modifications, because the size of the mat was too large for fitting into my racing seat.

At first I separated base and back part, carefully making sure to keep the cables long enough:

Then I needed to get rid of the outer parts of the mat and get access to all remaining cables.

Here is the mat after the modifications:

Now it fits:


As before, I wired the vibration motors in parallel with the fans. The connection to my PC is done with a JRK 12v12 board, in which I did an assymetric motor setup. (I only need the motors to spin in one direction.)

And I added two switches for separately enabling or disabling the fans and the vibration motors. In this way I can decide whether I want to only use the fans or only the vibration or both.

Here are two videos of my heave mechanism I described in one of the previous posts today.

The first one shows the flaps befoure mounting the seat.


And now with the seat mounted.

As you see, I have connected the back part of the vibration mat to the moving belts.


OK, that's all for now. Guess I will now enter the rig and do some testing.

Good old Obi Wan would have said: "Never underestimate the power of the (Heave) Force!"


The weak spot was here: I just drilled an 8mm hole into an 1/2 inch rod, and that's where it broke.


So I had to re-do some parts of the heave mechanics, and this time I reinforced the rod with a long nut where I had to drill the hole.


And I mounted a ball bearing on each side, because each heave flap has to lift half of my 90 kg.


Hope that it will last longer now.

Looks maybe like the first 8mm hole wasn't exactly centered, rendering one side weaker than the other, and as a result it let go. I like seeing how guys work around small quirks like this, the Ingenious idea's on the site are sometimes very inspiring.

keep it up Markus.

Thanks, @Nick Moxley !

Yes, you are correct: the hole was not centered. And I must confess that I still did not find out how to reliably drill a centered hole into a rod. Maybe it is my limited equipment, maybe it is a lack of skills. Well, probably a combination of both.

Did some basic tests of the flaps yesterday, and they work (again).

One improvement is still pending: At the moment I have connected some supporting bungee cords to the flaps, because the single 25:1 motor is not able to lift my weight.
Now I plan to replace these cords with springs that I want to install between the flaps and the seat base.
There is not much room there, so that I plan to use torsion springs. Up to now I don't have any experiences with springs. Guess I need to do some research first.

To drill a nice hole in a Threaded shaft, Ideally you need a nice flat landing pad to drill into, So a Small Dremel cut off wheel will make quick work of the threads and give you a nice flat surface to be able to accurately punch a hole in the center.

Damn, look what happened to my seat:


I thought that after implementing the heave flaps my rig would be complete and I could finally enjoy flying around. But then I discovered that these flaps are such a great improvement that I also want to have a second pair of them in my back for simulating the "surge" force.

So I did not think for long, cut away the seat fabric, and removed the springs.

Luckily I once ordered 4 of the MotionDynamics motors, although I originally only needed 2 of them. Now I will use my last one for adding "surge" flaps. Also these ones will be moved synchronously with a single motor, so that they will not provide sway forces. Guess I don't need it. (And as I said, I only have one motor left.

The main reason for this last(?) improvement is that I am not lucky with having the pitch angle and the surge force simulated by a common axis. The problem is that when the plane is decending, I have a negative pitch angle, but a positive surge force. And with a simple 2 DOF rig, pitch and surge are compensating each other, which does not feel right.

My plan is to change this by separating pitch and surge from each other.

So after this new (and until 3 hours ago unexpected) building phase, I will have a simplified G-Seat on top of a 2 DOF rig. "Simplified", because the pairs of flaps can only move together.

And then I need to think of how to re-connect my fans and vibration motors, because the surge flaps will need the JRK board that is currently used for the fans/vibration. Well, maybe I will try the Arduino approach that @SilentChill has explained. We will see.

Lol and here i thought you cut up a Fiberglass Bucket seat...Lol then i realized Its a Metal frame. That makes Oh so much more sense.

Yes, a metal frame with a fabric cover. Maybe fiberglass would have stopped me. Well, probably not if I think about it.

Tonight I made some progress with the 'surge' flaps. The principle is the same as with the 'heave' flaps. Here are some pictures:


Now I am waiting for the joints that will connect the flaps with the motor axis. I ordered them today and hope to get them before the weekend.

The flap module has a weight of 7.6 kg, and I guess that it will considerably change the center of gravity of my rig when I mount it to the back of the seat.
So I will probably have to move the pivot point. That will be some piece of work that I am not eager to do.

Make your pivot adjustable so no matter how much weight you add on the rear, you'll be able to counteract it with the pivot.