Showroom 3 DOF racing sim

Unfortunately, I haven't finished the frame yet for the pedals and FFB wheel. I have been waiting to finish the rest of the frame before I get Simtools. Once I get that and run it, I'll know if the motor drivers will be able to output enough current relaibly for the weight when it's running. If not, I'll have to add some gas struts to offset the weight the motors have to move.

It's tough for me to get time lately to work on this between my job and two young children but I'm slowly chipping away at it when I can. The attached picture is where I'm at right now. The tube steel where the pedals go will be shorter of course, just have to figure that out when they're mounted.

Thanks for your reply! Yep there are more important things in life . No worries but please keep us updated. It's looking awesome already, looking forward to see the end result.

How are you getting away with such low wattage motors? I’m new to all the motion sim racing but everywhere I research says that you need something in the 700 W range, 80nM or more torque for each motor. which makes it really hard to find on eBay and you have to special order off of Alibaba.

It is a 300W 12VDC motor with a working speed of 3000 rpm and a 50:1 gear reduction off the worm gearbox. Using ideal calculations without losses, the torque off the motor is 0.96 Nm where the torque is the power to the angular velocity. To calculate the torque then provided to the output shaft of the gearbox, it is the motors torque times the reduction which is 48 Nm. However, if you consider the efficiency of the gearbox (which I don't know) it is much less. If we conservatively say 60%, then that makes the torque off the output shaft 28.8 Nm. This torque 70mm out off the attached lifting lever arm, generates a force of 411.4 N (force equals torque over radius). Converting that static force to a mass (F=ma) equals to 41.9 kg or just over 92 pounds. Multiply that by three motors and you have 276 pounds of static lifting force (or so I hope lol). Again, I don't know the efficiency of the gearbox so it's rough estimate.

Now, with the materials I've chosen to work with, I may need to add some gas struts on the frame to help take some of the load. Hopefully, I will know soon as I've been slowly chipping away getting to test it out.

Little update:

I've got most the frame done now (with the exception of the mount for the shifter and hamdbrake).

Once that is done, I can clean it up a bit better and paint it. Then I can test it out with simtools. I also need to wire up my mini contactor I'll set up with a momentary start to create a latching circuit with an emergency stop in series. I can do that later on though. Just gotta keep looking for time for when I can work on this project, I'll get there one day

Got the handbrake and gearshift mounted with a cut up piece of aluminum from the base of an old server rack I demoed for work. I'll likely cut out a triangular section from the back to get rid of that sharp edge and make it look a bit more asthetic as well. In the process of doing all this, I dropped my drill and broke the gear off my potentionmeter bracket. I've done this like 3 or 4 times now and need to redesign. Unfortunately, until I fix that I can't test with Simtools . I have an idea though that should be more robust, just have to redesign in CAD and 3D print it. Hopefully I will get to that in the next couple of days.

Ok! I've got my potentiometer brackets redesigned where the drive gear is directly attached to the output shaft of the motor.

In doing so I had to shorten the bracket and just flip the driven gear around (should've done this in the first place). There is no movement at all whereas the previous design there could be some movement in the drive gear because it was attached to a flex coupling.

I also have wired up my latching start circuit using a mini contactor. I mounted the start/E-stop on the right corner of the frame so the it was within arms reach but still out of the way. I wish it was more obscured though.

This is a diagram of the circuit I used:

I opened up the 20amp power strip I have and cut the line and neutral wires to then terminate to the mini contactor and come back to the protection circuit (listed as single phase motor in the diagram).

Here is the power strip:

It has a switch for each outlet in case I need to turn two off and troubleshoot one motor.

Now I think I can finally test with SimTools! Only problem is that it's late and I can't test now. Late at night after the children have gone to bed is usually the time I can get to work on the project. Soooo, let's hope that I can get some time this weekend between the birthday parties and having the replace the tie rods on my wife's car lol.

In any case, I have purchased a license for simtools and started reading through the manual and installed a couple of plug-ins. Really excited for the next time I get to this because I'll get to see it move with some load on the motors and can get an idea on how I can tune it and whether I need to add some gas struts to help with the weight.

Well I went to test and ran into a couple of problems (one of which I believe I fixed). Having flipped my potentiometer around, I inadvertently also flipped the feedback values and when I started SMC3 to make sure everything looked OK, and was at least moving, the control arm for motor 1 went to a maximum position of "up" because the values it received was saying that the control are was in fact moving away (down) from setpoint. This caused the control arm to collide with the potentiometer bracket and the motor housing. The housing stopped the control arm but not before cracking my potentiometer bracket . After a lot of troubleshooting on a easy fix (like trying to flip polarities), I came across the line of code for the motor feedbacks"Feedback1 = analogRead(FeedbackPin1);" and subtracted the value of 1023("Feedback1 =1023- analogRead(FeedbackPin1);"). That has now made the motors try to reach the setpoint in SMC3.

I was still having the problems I posted back on 11/30/25 where on motors 1 and 2, the target (sent) is higher than the target (received). I decided to ignore and move forward with the SimTools setup and got stuck there. I have install SimTools version 3 as it was available when I purchased the license and the notes basically stated a better user interface and ease of use. However, when going through both the quick start guide and the user manual, I can't get my interface to configure. This is my current attempt:


I have installed the "serial" plug-in for the interface (I'm using an arduino) and the "generic 3D rotating" for the axis plug-in. When entering and saving the configuration above, I get no movement out of any motor when clicking "test settings". I am stuck and need some help . Appreciate anyone's assistance and time.

So I got past the interface connection by using the settings in the picture below:

Now when I test the settings I can get motion out of each motor.

Back to my issue I had in November of 2025. I have copied and pasted my post from then as I am experiencing the same problem:

Target issue:
Next, when running any motion to motors 1 and 2, the target (sent) is higher than the target (received) seen in my arrow #1.

This results in a much smaller movement than what motor 3 gets as the sent and received target are the same (seen in screenshot below).

Why aren't motors 1 and 2 moving to reach the target when 3 has no problem??? The only thing I had edited in the code is originally setting the mode for the IBT-2 drivers and then recently (yesterday night) subtracting the steps from the potentiometer feedback because I flipped them around.

Load issue:
You can see in the screenshot above for motor 1 my arrow #2 point at the PWM spike and the feedback (potentiometer) lag where I pressed down on the top of the frame to load the motor with some of my body weight and it completely stalls and emits a noise from the motor until the load is released. Is this because I haven't tuned the SMC3 settings properly? Because I don't have the correct bits per second being sent to the arduino? Or is it an issue with my motor IBT-2 drivers? I have wired 2 in parallel to halve the current load each driver experiences.

I have also noticed, now having SimTools and doing the initial configuration for the motion profile, the drivers for motors 1 and 2 are getting hot whereas motor 3 is only warm. My motor 3 is the rear center only providing pitch and heave. I feel like the SMC3 settings aren't right for my motors and the motor 3 PWM settings in SMC3 utilities only allow for either 4kHz or 31 kHz. The lower I go on the PWM the loader the motors are from the magnetostriction (had to look this up lol). I am trying to ascertain whether I have a configuration issue or a hardware issue...

In Live for Speed
I know I haven't resolved the issues above but I wanted to see something happen in a game so I launched Live for Speed and when using the configuration below I basically had no movement from the motors. Motor 3 (rear center for mostly pitch) was moving slightly but there was mostly just frequency noise from the motors like the were trying but nothing really happened. I was not sitting in the seat, so only the weight of the rig (seat, frame, wheel, pedals, etc.) was loading the motors.

I am using only one arduino for the three motors. Do you have an idea of why the movement of the output isn't meeting the target setpoint? Or what parameter affects that?

I don't recall when changing the Fpwm that the tracking also changed as well. From what I recall it would never reach setpoint for either motor 1 or 2 and only produced small movement. Nonetheless, this evening I will try it and see if I was just overlooking that was happening. Also, I have ordered another arduino so that only 2 motors will be assigned on each controller.

I can definitely (and just have) buy some ferrite cores but do you have a suggestion for wire management? I suppose I could twist my power wires from the PSU and motor but can't think of what else to do. I already am using shielded cable for the potentiometer's and have the drain only terminated at the ground on my terminal blocks.

Ok, yeah I feel like I have those separated, though proximity wise they could be considered close. I have ordered some ferrite cores like you suggested and will clamp plenty around the PSU power output, potentiometer input to the arduino, and around the motor wires after twisting them together. I also saw that it could help to clamp some on the USB cable between the arduino and PC at each end. I'm sure that'll help but not sure it'll get me to a more "usable" state where I have things as the moment. Aside from tuning, I am now concerned that the drivers (IBT-2) I'm using are not sufficient.

I know I dont have the most powerful motors at 300W, but based off my rough math I think I should be good on my weight and the weight of the rig. I have also ordered some cheap ~67 pound gas struts (quantity of 3) to basically offset my body weight to see how that helps. I still think the tuning is off but I'm learning as I go and am trying to drill down on where my deficiency is to get it to a running state to tune.

Thanks again for you help, I know how tough it can be helping remotely on issues you dont have all the details and aren't doing so in real time.

I seem to have made some positive progress (which is good because I was starting to get a little discouraged ). The three biggest changes I made were reducing the CTC of the levers from 70 mm to 50 mm, tying the grounds to a common point (more on this below) and adding gas struts to the front two motors (motors 1 & 2).

CTC Reduction
I 3D printed a jig that had extruded holes that lined up with the existing 70mm and 85 mm (<-- how naive I was lol) holes so that I could use a center punch to drill the new hole at 50 mm.


Gas Struts
The struts were added to the front two motors (1 & 2 that take care of the roll). I initially purchased ones rated at 67 pounds and installed it on the rear motor 1 that controls the pitch. These things are cheap and were purchased on amazon and I could barely compress the thing with all my weight and strength. I wasn't sure if they were defective or the rating was based of the "effective" force once installed at the prescribe geometry. In any case since I had it, I figured I would give it a try; it ended up slightly bending the frame and the 11 gage sheet metal it was attached to. When that failed I moved the CTC to 50 mm and the pitch seemed to move with confidence and the motor and IBT-2 drivers didn't get too warm. Feeling a bit more confident I moved onto the other two motors. Unfortunately, motors 1 & 2 didn't perform well at all and the motors and drivers were getting fairly hot. I tried different tune settings in SMC3 with no improvement.

I still wanted to counteract some of the weight and help on the backlash transition, so I ordered from a different "supplier" and ones rated at 45 pounds. These were much easier to move with some effort and also seemed to move "quick" enough. I installed these on the front two motors and they helped significantly! Each could move while I was in the seat without stalling using both the sine wave and the simulated motion.

I was still concerned though about how different motors 1 & 2 movement setpoint were from motor 3 and tried to research here and elsewhere online to get ideas to troubleshoot. I couldn't find anything online that showed me a laid out method to test these motor drivers but while they were running in SMC3, I metered the outputs and they modulated between positive and negative voltages and each heatsink was getting warm so I figured they are working in some capacity. I did note though that while using the sine wave in SMC3 that the output voltage from the IBT-2's never got higher than 4 VDC. However, I also still can't get the target received (dark blue) to meet the sent (light blue) for motors 1 & 2 even though with the same settings on motor 3 (except for the Fpwm) it reached it just fine. So I though maybe the output voltage isn't closer to the 12 VDC because of that???

Note in the screenshots below motors 1 & 2 can't move (green line: potentiometer) while sitting and no gas struts installed:


These screenshots are with my full weight and the gas struts installed on motors 1 & 2:


On each of these I ran the sine wave without my weight to begin and then sat in the seat roughly midway in the screenshot. You can see the pwm increase when I do and the green line showing the motors lag to reach setpoint. I believe this is mostly due to the backlash in the worm gear when it changes directions. When I played around with these using the motion setting, the smaller movements couldn't be felt as the backlash took to movement instead (could audible be heard).

I am still curious as to why the target isn't reaching setpoint for motors 1 & 2. I tried messing with the "max limit" and "clip input" but the didn't effect things at all. Is this perhaps something the SMC3 code in the arduino is limiting? @noorbeast I see that there is axis limiting in SimTools but I can't see where I could increase the limits/range of motion per axis. Am I missing something or is that what is done on the Min/Max tuning for each game? Just wondering if I can ignore this perceived problem in SMC3 utilities.

Common Ground
While researching online and here in the forums to help me with the problems above, I realized that the noise I was experiencing in the screenshots from my previous posts was in fact due to not having a common ground! I felt so stupid about this because I service low voltage building automation as my occupation and know better about this. I even had an issue at a customer site (like 8 years ago though) where some HVAC controls weren't behaving properly because of this. Typically, the equipment I work with is all engineered so as to mitigate this problem but no site is ever the same.

When I was installing and wiring everything on this motion sim, I was focused only on each motor and power supply as its own group. After realizing this mistake and wiring all the control grounds to a common point, my noise in SMC3 went away (seen in the screenshots above) and the audible noise emitting from the motors was quieter too as a result of the pwm being smoother.

Other notes
My potentiometer bracket is better but I still am not happy about it. I can still some small flexing at times when the motor moves. It may be because it's 3D printed or just my design in general but I am going to revisit it.

Sometimes, when working around the wiring, I move the enable wiring on the HP power supplies and the pin jumpers I made seem to have some play in them and if nudged the right way, they cut the 12 VDC power to the IBT-2's. Will also revisit this in the future.

Once I feel like I can get this thing working, I still need to paint the frame for the pedals, FFB wheel, etc....