DC Motors for 6dof?

I have been thinking about building a 6dof compact Stewart platform using these 400w motors https://simukit.com/moteurs/8-moteur-400w.html.

I haven't finalised my design yet and am still working my way through Wannabe Flyers build thread and ZigZag49's build. https://www.xsimulator.net/community/threads/6dof-dc-24v-smolka-zigzag49.7490/

The platform needs to be able to carry 200kg, and knowing nothing about motors can anyone tell me if 6 of these 400w motors (rated at 57nm) would be sufficient or capable?

57NM, Arm 100 mm, about 58 kg of force, 6 motor can get about 350 kg thrust, great.

Thanks.

Arm up to 150mm. About 38kg, 6 motors on the 230kg thrust.

Hi Fluke hi xiatian; xiatian would you care to provide the maths calculations for the figures you provided!

Regards Jerry

you will still need dampers to handle the loads created when the rig moves. i doubt your calculations factor in momentum. levered 6 dof on 12v will probably need help from dampers. this is why most are switching from levered 6dof to actuators.

They are 24v 400w worm gear motors running at 50rpm giving 57nm per motor. I don't want to use actuators as I plan on a compact build.

You may get lucky and not need them. it depends on how aggressive you plan on getting with your profile and which titles you play. 200kg is a lot of weight especially when already moving in the opposite direction.

Hello there: Jweey Atrick

57 nm / 0.15 (m) = 380 (Newtons)
380 / 9.80665 = 38.74kg
6 (Axis) x 38.74 kg = 232.44 kg

57nm/100mm=570/9.80665=58.1x6=348.6kg
57nm/150mm=380/9,80665=38.74x6=232.44

those numbers are for a static start.....

Hi and thank you xiatian, for your assistance.
I will try to remember these calcs for my rig, if I don't die before hand!
Regards Jerry.

Hi Bruce, thanks for your input, and good to know these are "static start" figures calculated.

Regards Jerry.

Each motor has 400W power. The response speed of the seat should be no problem,

Heat can become a problem with youre math!

Sorry, perhaps I was wrong, may have overlooked a number of other factors.

I think 400W is electrical input power, axle output is close to 300W as worm gears have not so good efficiency. Because 57Nm @ 50rpm equals 298W.

So you have 6 x 298W = 1790W of power. And P = F x v, Power = Force x velocity. It means you can trade force for velocity by lengthening moment arm and vice versa, but its a trade-off always.

How much speed do you need, 0,5m/s should be enough? What is the available force then? P = F x v -> F = P / v = 1790W / 0,5m/s =3580N = 365kg of lifting force.

3580N / 6 = 597N for one motor, 57Nm / 597N = 0,095m moment arm. True speed and movement range with that moment arm? Circumference of circle radius 0,095m = 0,6m. If using 90 degrees sweep 0,66m / 4 = 0.15m along circle, about 0,135m in straight line. And 50rpm = 1,2sec for one round so 0,3 sec for 90 degrees which equals 0,15m. -> 0,15m / 0,3s = 0,5m/s speed so it adds up. That is of course circular speed, linear speed 0,135m / 0,3s = 0,45m/s but linear speed decreases and available force increases as moment arm rotates away from 90 degree angle. P still equals F x v because both change...

How about acceleration? a = F / m, acceleration = Force / mass.
200kg is coming down 0,5m/s and wants to go up 0,5m/s. Earth's gravity acceleration = 9,81m/s^2. F = ma = 200kg x 9,81m/s^2 = 1960N of force needed just to stay level. 3580N - 1960N = 1620N left for acceleration.
a = 1620N / 200kg = 8,1 m/s^2. So you gain 8,1m/s speed for every second passed, and speed difference down/up is 1,0m/s. -> 1,0m/s / 8.1 m/s^2 = 0,123s to make that speed change.

There are some theoretical calculations for you, errors and overlookings are guaranteed.
Is there too much strain on motors, generating heat and other problems? Someone with more practical experience can talk about that better than me.

and this math still doesnt consider the weight moving at speed and the forces it takes to reverse and get same speed in the other direction. it will work with dampers but as you explained heat will be the biggest problem. Something to consider. A 6dof does not distribute the weight evenly. meaning that the calculated forces above are distrubuted equally between motors. this doesnt happen in real life. unless you only use heave and then I still doubt it is evenly distributed.