[In Progress] Low-cost 2DOF W/ Wheelchair Motors

I have started designing, and ordering parts for my low-cost 2DOF motion rig that will become my base platform for future upgrades/updates.

This thread will outline the build process as well as the parts used for the project. I will be leveraging Fusion360 for the designs, and a 3D printer for most of the parts/pieces.

Parts List:

Ordered:

• 2x Jazzy Wheel Chair Motors (12-24VDC) - $55
• 1x 24VDC 25A (600watt) Switching Power Supply - $37
• 2x BTS7960 High Power Motor Drivers - $16
  
• 1x Racing Sim Stand (good starting point for a very small price) - $42
• 1x STM32 Bluepill Microcontroller (Faster Uno Alternative w/ > Analog Accuracy) - Free from Drawer

Researching:

• Steel for Framing
• Extruded Aluminum for Framing
• Universal Joint
• Motor Lever Arms
• Tie Rod Connector Arms
• Racing Seat
• 10k Potentiometers

Here is the wheel and pedal set up in real life:



Modeled the stand in Fusion360 and threw in some extruded aluminum that will attach to it to mount the seat. Also found a model that is close enough to the Thrustmaster I have and threw that in as well.



More updates to come...

Hi Simracer 12,
Looks like a good starting point! I would start researching about COG and keeping that above your uni joint. This will give your motors more power to move you rather than keeping you upright.

What is the rated torque of your motors?

In terms of steel and uni joints, pots etc, im not sure what country you're building this is in, in terms of helping you find cheap places to buy it all?

There are plenty of projects on here that will give you more ideas and tell you any problems they had along the way (including mine )

Hey Chris,

I don't have an exact spec on the motors right now besides this from the eBay ad:
"Rpms are ROUGHLY 120rpm at 24vdc / 60rpm at 12vdc."

Once they come in I can do some more investigating and testing.

As for the COG, you are right and that will play a large role here. I am actually going to try and design my own 3D printed uni-joint with some cheap ball bearings and see how well that works out.


I am buying from Eastern USA and have been looking at Ebay, Aliexpress, and Amazon mostly. I am open to more ideas.

I just bought 5x 10kohm pots for $2.73 from Aliexpress.

The 3D printed uni joint sounds really cool and cant wait to see how that works out!!!!

However i am slightly concerned that it wont be able to handle the mass or it will deform enough to bind. (I could be wrong)
Might be worth looking at some automotive stores that have cheap as uni joints. I found one for my sim for less than $15.
I am from Australia so i cant help much on where to get materials from. Ebay and Aliexpress is where i got most of my stuff. In Australia we have steel supplies that will cut your steel to the lengths you want, along with bolt stores. Both are a lot cheaper than most places.

Do you have any initial designs as of yet? Would recommend that so everyone can see anything that may work or may not / masses / torque you may need Just to save you some time later on

Purchased:

• 10x 608RS bearings for the 3D printed U-Joint for $7.37
• 1x 24VDC 25A (500Watt) Power Supply for $36.90

As for the framing, I am looking at a website called metal supermarkets that seems to be able to deliver cut pieces of material for a reasonable price. Has anyone had any experience with them?

I am thinking the base of the sim will be made out of welded steel square tubing that is 1.25" x 1.25" x 0.065". This will hold the motors and electrical components. I am deciding between aluminum extrusion and aluminum square tubing for the top portion of the sim that will hold the seat and driver.

I am working on simulations for the 3D printed U-Joint as well as printing a prototype version so I will keep everyone updated on that part of the project.

The motor drivers just came in the mail, but the wheelchair motors seem to have gotten lost in shipping. They were least seen about 30 miles from my home, but know the delivery company has no ideas where they are... I am sure they will show up soon.

As for the simulations, the weakest point seems to be around the bearings which I guess makes some sense, but to me is seems as if this will not cause an issue in practice, any thoughts here?



This is as far as I have gotten as I have been traveling for work:

A few more items have arrived:

• Power Supply
• Racing Seat
• VR Headset

I am still waiting on the motors, unfortunately they are still hung up in shipping.

I received the chair and created a quick and dirty wooden base for it so that I could try it out and get a rough positioning for it to put into the model. Once the model is updated (waiting on a few more parts to confirm locations) then the framing material can get ordered and the build should take off from there!





The seat is a cheap $150 one from ebay! I am happy with it so far, looks good, feels good, and was cheap.

Small update:

The motors and power supply finally showed up. I was able to throw a quick model together with the motors and some tie rod ends;


Need to do some more testing with the motors as there is a lack of info on the motors, all they have written on them is: 24VDC MAX 3A 180Watt 28:1 H Class TYPE: MOT1706086-L

More to come...

Really excited to see your 3D printed joint and if it will fullfill the robustness requirements. If not... I bought a one like this and it works absolutly well U-Joint

BR
Chris

Finally received my potentiometers. I am finalizing my steel square tube order for the framing and then things should start to come together pretty quickly (hopefully)!

More interesting updates to come! Thanks for staying updated.

The idea of using wheelchair motors seemed great to me, you have also found them very cheap.

Can you indicate the exact engine model?

edit: OK MOT1706086, where can i buy?

I got mine on Ebay. Check this link out for something similar: https://www.ebay.com/itm/Jazzy-Whee...150090?hash=item33f8a8e40a:g:8FsAAOSw0kFaxWcR

Made some more progress and ordered the extruded aluminum for the frame from McMaster. This cost about $125. I also bought some aluminum angle to make into 90 degree brackets for the extruded as well for about $11. I found some T-Nuts and bolts for about $15 as well and started to get everything framed out;







So far the 3D printed U-Joint is doing well with holding me up! I will be working on getting the motors mounted as well as the control circuitry. Then it will be time for software. As for the software, can anyone point me in the right direction here? I am looking to run this rig with Assetto Corsa for the most part.

Thank you

I have 2x BTS7960 which I guess would be the "IBT2" option, correct? (https://www.xsimulator.net/communit...3dof-motor-driver-and-windows-utilities.4957/)

Wiring and programming wise I should be fine with setting everything up. My PID tuning is a bit weak, but I am sure I can get it dialed in. As for the simtools software, where can I download that from? It looks like it says it is free if you create a build post, which I assume is basically exactly what I am doing here?

Thanks!

As you guys have seen from my thread I am very big on using 3D printed parts for as much as I can. Really this is just a personal challenge that helps me become better at design, prototyping, and testing. I have gone through a few iterations of a few of the parts as they have cracked during load testing. At this point I am very happy with the motor mounting as well as the tie rod mounting. The only thing I need to work on is the 3D printed tie rods as they have a decent amount of play in them. The mechanical set up is almost completed at this point so the next step is to do as @noorbeast suggested and use the SMC3 code and the unlicensed sim tools for some initial testing and debugging.




This project is moving a bit slower than expected due to how busy I am at work, but also the other projects I am working on in parallel; Touch Screen Digital Dashboard for my car, Microspot Robotic Dog, Desktop Palletizing Robot.

I got the SMC3 code set up and working so I was able to start doing some movement tests... AND almost as expected the amount of yaw play in the 3D printed U joint started to show through..

At this point I am not sure if I am going to give up on the 3D printed U joint and just go with a metal one, or mess around with some more prints and potentially a anti-yaw mechanism. The ideas would be I could still use the 3D printed U joint as it can handle the load quite well, but another mechanism will stop any unwanted yaw from occurring by locking the moving platform to a another post in the back;




I expect this concept to work, although the joints are not working out correctly in Fusion. Perhaps I am missing something obvious and there is a flaw to this mechanism.. If anyone sees an issue please let me know! Please note a spring loaded screw would need to be used to account for the pitch of the moving platform. I drew in arrows to show the degrees of freedom. Z movement from a slider plate inside of the extruded aluminum channel, X movement (front to back) from a spring loaded connection, roll and pitch movement comes from the tie rod's ball.

Not sure why I cannot embed the video into the post, but here is a link;
https://photos.app.goo.gl/SA8hhAcTEZjV661a6

@noorbeast Not sure I am following how the Panhard rods would be implemented. Do you have an examples?

Which angles on the heim joints are you concerned about? In the render the angles are definitely abit off, but it practice I haven't seen this happen.

As for the video you are 100% correct. I am running through a singularity which is not good, but it created alot of torque on the top frame which I was using to visualize the yaw play in the system. In practice the "resting" position of the level will be parallel to the ground.