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2 Axis Active Belt Tensioner

Discussion in 'DIY Motion Simulator Projects' started by mars, Apr 26, 2020.

  1. mars

    mars New Member Gold Contributor

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    Hi All,

    I am starting on a project to use Simtools to control left and right belts using 60Kg-cm RC servos and an Arduino Uno. Simtools makes the electronic part quite simple. I have built the attached "proof of concept" model with micro RC servos and used the free version of Simtools to get it up and running with LFS. I am now designing the physical aspect of the project using 3D modeling. My plan is to use 2020 extruded aluminum and PVC to create a system that has rollers at the top to allow the belts to pull up and rollers at the bottom for the servos to spin to generate the belt tension.

    One question I have that someone who has built a similar system might be able to answer - how much length of belt movement do I need to get an accurate portrayal of the forces in the car? I have a standard racing seat with no motion.

    I plan to use a drum to roll the belts up at the bottom of the system and there are (2) variables:

    1) servo motion angle (180º or 270º)
    2) drum radius

    I am pretty sure I want to use 270º servos as this will allow me to use a smaller drum for the same length of motion. The advantage of the smaller drum is more torque applied to the belts. I guess the only disadvantage of the 270º servos would be their speed. Any advice here would be very helpful.

    One idea I have is to start with a certain radius drum based on a specific pull length but have the option to increase or descries the drum size if I need more or less length of motion. If I could get close to the proper belt length pull to start based on input from others that have used a similar system I would appreciate it!

    Thanks and I will post 3D model images as I complete them,

    Mars

    IMG_6573.jpg
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  3. mars

    mars New Member Gold Contributor

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    Some more background on my current setup. I have built a simple box that my seat sits on that I can move around relatively easily because I don't have a dedicated space for my rig. I have a system of turnbuckles that connect my seat box to my pedal box so I can move them around when needed. Because of this I want the belt mechanisms to be attached to the chair itself so I can:

    1) Move the system easily with my seat
    2) Keep the belt size the same even when I change the seat angle - I use the seat to fly DCS(upright) and drive iRacing (reclined). If the belts are attached to the back of the seat the belt tension will always be the same.

    My plan is to use off-the-shelf 2020 aluminum and PVC for the mechanisms. In doing some simple 3D modeling I discovered that each belt mechanism will be too wide to sit side by side. The current design is to put one slightly higher than the other as shown below.

    One thought - if I can make the 2" PVC caps shorter by cutting them and still get positive connection between the caps and the pipe I might be able to put the two mechanisms back to back and attach the inside ends to opposite sides of the center 2020 post. I will have to get some parts and take accurate dimensions from my chair.

    Any thoughts or advice greatly appreciated!

    Thanks,

    Mars

    2020 & PVC mechanism:
    Screen Shot 2020-04-26 at 10.39.18 AM.png

    (2) Mechanisms staggered on rear of seat:
    Screen Shot 2020-04-26 at 10.37.23 AM.png
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  4. EduardoMoreira

    EduardoMoreira New Member

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    My Motion Simulator:
    2DOF, DC motor, Arduino, Motion platform
    In my setup i use rods. The response time with the rods appeared to me to be faster than the system like yours. Besides that with the rods I can use the 180 degree servos.

    Attached Files:

  5. mars

    mars New Member Gold Contributor

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    Thank You Eduardo!

    If I understand your system correctly the yellow and black rods swing with the servo arms. How long are the rods, how much motion do you get at the end of the rods (length of throw), and what size servos are you using? When the servos move, how many degrees do they swing through? Is the full 180º available?

    My biggest unknown at this point is what length of belt I need to be able to pull in and let out to get a good effect from the system. If I am understanding your system it looks like you might be getting way more length of motion than I was assuming I will need...

    Thanks in advance for your continued help!

    Mars
  6. mars

    mars New Member Gold Contributor

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    As a follow-up : If I need more than about 4.5" (11.25cm) of belt movement I think I will switch to a rod system more like yours. The mechanism might be more susceptible to damage when I move my seat but it makes sense to use a system that works well!

    Thanks,

    Mars
  7. EduardoMoreira

    EduardoMoreira New Member

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    My Motion Simulator:
    2DOF, DC motor, Arduino, Motion platform
    Yes the yellow and black rods are swing with the servo arms. The rods are 26 cm. The angle of movement of the servos will depend on the size of the rod. In my case it does not exceed 70 degrees. Below is the link to a test I did. I use 60kg servos. You also have to be careful to make a smooth roll system on the top of the seat so as not to lose yield. I used a set of bearings. Yhe photos I have here are from when I was assembling the system, the belt was not yet adjusted.

    YouTube video:

    Attached Files:

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  8. mars

    mars New Member Gold Contributor

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    Thanks Again Eduardo.

    Some follow-on questions if you have time...

    1) If your servo arms are 26cm long and swing through 70º your belt movement should be ±30cm. In your video it looks like you are getting more like 5-7cm. Is this because the motion in the video is smaller due to the type of test you are doing? When you are using the system what do you estimate the maximum belt pull length you need to get a good feeling from the belts?

    2) Do you have a spring in your system that gives if the servos get to stall? It seems like some systems have a spring and others do not and I am trying to decide whether I need one or not.

    3) How are you powering your servos? I am thinking I will get a 7.5V power supply.

    I plan to use 60kg servos as you have. I also plan to build a simple roller system at the top to keep friction to a minimum.

    Thanks!

    Mars
  9. EduardoMoreira

    EduardoMoreira New Member

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    My Motion Simulator:
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    Mars that's the intensity I use. The human body is not malleable like the pillow. What looks a little like a pillow is not the same on the body. The feeling of tightness is very good, but if I want I can still increase it, because the intensity of the effect is 74%. Regarding the stall, in the regulation that I'm using the servo makes a maximum force of 42kg, which avoids the stall. I use the maximum voltage allowed by my servos, 7.4V
  10. mars

    mars New Member Gold Contributor

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    Thanks Eduardo - your video and photos are very helpful. I think I will continue down the path of using rollers and plan for a belt tension length of ±5-7cm. I can imagine if the belts start off "snug" then this amount of pull will feel quite realistic and plenty strong to relay the feel of the car through the belts. If my system ends up feeling too slow I will switch over to a system with arms like yours. The only reason I will continue with the drums is that it seems that it will be easier to move my seat without damaging the system if it has rollers vs. arms. This is a requirement that is unique to my rig as I do not have a permanent home for my rig...

    How do you regulate the force of your servos? I plan to use my Arduino Uno for the signal and a 7.4V power source for the servo power. Is there an easy way to regulate the servo force?

    Thanks and I will continue to post updates here as I move forward.

    Mars
  11. EduardoMoreira

    EduardoMoreira New Member

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    My Motion Simulator:
    2DOF, DC motor, Arduino, Motion platform
    Mars when you are not playing, you can manually move the rods so that they are very close to your seat, preventing anyone from bumping into them. The amount of movement of the rods you can adjust in the simtools

    Attached Files:

    Last edited: Apr 28, 2020
  12. mars

    mars New Member Gold Contributor

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    Thanks for the photo. I have my 2020 and PVC arriving next week so I can begin to build the mechanisms. I will aim for 5-7cm of belt pull as a starting point. I think I will use 180º servos as they should be able to give me up to 9cm if needed. I think my system will be a bit slower than yours but I should be able to get the full 9cm of belt pull in ±0.4s based on the servo specs. I think this should be fast enough...

    Mars
  13. mars

    mars New Member Gold Contributor

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    Progress! I have costructed the top rollers from 2020, PVC, and skateboard bearings. Now I need to attach it to my seat and build the lower roller mechanisms.

    IMG_6684.jpeg

    IMG_6685.jpeg

    IMG_6686.jpeg

    IMG_6687.jpeg
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  14. RENZOREY18

    RENZOREY18 Member

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    Hello this project interests me a lot I am in a 2 dof project that I am almost finished that you can go to see my profile, tomorrow or the day after I will upload more advance of it I want to do something about yours simulate the forces when braking in a car and I had thought to place two motors with one arm and a spring at the end, the spring hold the seat belt and when moving the arm that simulates the tension of a car braking I do not know if I explain
  15. mars

    mars New Member Gold Contributor

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    Hi Renzorey18,

    I am trying to make a 2 axis belt tensioner using a roller attached to the servo to pull the belts. I think it will work but my design is untested. Others have made it work so I am hopeful.

    Eduardo posted photos and a video if his system here as an alternative and it is very similar to what you describe so it is possible.

    I will post more progress photos soon. My servos and belts arrive this week so I should have some results within a week. I will keep you posted.

    thanks for the interest,

    mars
  16. mars

    mars New Member Gold Contributor

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    More progress!

    my intent was to make all of the mechanisms with readily available parts as I do not have a 3D printer. The frames are 2020 aluminum extrusion and the rollers are made from PVC and ABS pipe.

    here is the frame for the large rollers that will be actuated by the servos:
    11AB28CC-B7F2-4BCB-BA5B-231814FF81BF.jpeg

    4D9531AD-19D1-4E62-8960-9741E443A1AF.jpeg
    The servo horn will be screwed to the end of the ABS roller and fixed to the 2020 frame with a plate and zip ties.

    and here are my top rollers attached to the back of my racing seat:
    A5AD5607-E045-4327-A34C-69C420976F9C.jpeg

    15D884C6-FDEF-4383-85B4-104ED036F1D2.jpeg
    I am looking forward to getting my servos and belts this week!

    Mars
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  17. RENZOREY18

    RENZOREY18 Member

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    Hello mars
    I liked the result of your project, it would be great to show how you have done it step by step if possible.
    my question is how will you make it work with simtools. or what software will you use?
  18. mars

    mars New Member Gold Contributor

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    Hi Renzorey18,

    I will use SimTools with an Arduino Uno flashed with the utility to drive RC servos available here on simulator.net:

    https://www.xsimulator.net/community/marketplace/rc-model-code-for-arduino-uno-2dof-expandable.89/

    Once I get everything up and running I will use the iRacing and DCS plug-ins for SimTools. I imagine there will be some fine-tuning of the profile in SimTools for both surge and sway. My hope is that the belt feedback in VR will give a little bit of the sensation of g-forces on the body from both braking and cornering in a car and acceleration in an aircraft. Obviously this is no substitute for a motion rig...

    I can answer any questions you might have about the construction of my system. It is still a work in progress...

    Thanks,

    Mars
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  19. RENZOREY18

    RENZOREY18 Member

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    Great, I'll be watching your project to see the end result. See if I dare to do one myself, I have 2 wiper motors and I think it would be good to do one I really like its design

    Thank you !!
  20. mars

    mars New Member Gold Contributor

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    With wiper motors you should be able to generate a lot more tension than I will with RC servos. I will post progress here as I make it.

    Thanks,

    Mars
  21. mars

    mars New Member Gold Contributor

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    Servos arrived but I still need my 2020 metal plates to permanently secure them to the frame. I used zip ties for testing and everything seems to work well.

    Here are the lower rollers with the servos temporarily installed:
    IMG_6700.jpeg IMG_6698.jpeg

    Now to mount the frame to my seat and attach the belts.

    Mars
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