6dof new project, question about motors

Hi, I'm thinking about make a new project. I want to make a 6dof sim, and I'm looking for a cheap motor, that fit the minimum requeriments for this project.

I've found a very cheap motors (about 40€/ud) with this specs.

Rated voltage: 24 V DC
Idling speed: 48 rpm
Rated torque: 16 Nm

I've the specs table too:



I think that the motor has about 200w (216w 16 Nm 9A 24V in the table), but I'm not sure.

I don't know if that motors are enough for a 6dof project, but I think that it's possible.

What do you think?

Can I start my project with 6 of that motors or I need to find a better ones? Which one? Why?

Thanks in advance and sorry for my poor english

Best regards
Dualin


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Look. It's easy to calculate.
16 Nm = 1.6 Kgm (approximately). It mean if motor's lever is 10 cm (0.1m), the max weight for one motor will be 16 kg (1.6 Kgm/0.1m). And max weight for six motors will be 16*6 = 96 Kg.
You can increase this value twice if reduce lever's length to 5 cm (max movement distance = 10 cm), but I think it's very small for 6-dof project.

Enough it or not enough you can answer by yourself.

Regards,
Ale

Thanks Ale for your fast answer. I've made the same calculations, with this result:
Max weight of the driver: 100 kg.
Weight of the cockpit, chassis, monitor, wheel, etc... 50 kg.
Then I can put a max length of the lever of 6,5 cm. it's that length enough???
And, for example, one day uses the sim a person of 120 kg. what will happen, the sim won't work or simply the speed will be reduced??

As I can see in the table, if i use the torque of 16 Nm, the speed will be btw 35-45 rpm, it's enough?? Which it's the recommend minimum of the speed???


Thanks
Dualin



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Hi, Dualin.

I urge you (and everyone) is critical of the advices (even mine). Always try to form your own opinion based on your experience.

Our "easy calculations" gave us (approximately) the MAX possible weights for this motors. I think it will be better if platform+gamer weight will 25% lower.
And I think that 6.5*2 = 13 sm may be enough, and 35-45 rpm may be enough for AVIA-sim and not enough for CAR-sim.

But I recommend to you find on YOUTUBE 6-dof videos and try to estimate real movement speed and distance.

Regards,
Ale

I've got the impression, the curve above is for 12 V. Can you doble-ckeck?

Hi, I think that the curve above is for 24v. Why do you think that it's for 12v?

Regards
Dualin


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Hi @dualin
I was trying to replicate your curves and calculate the efficiency curve and power output, stall torque, stall current, etc. And replicating your curves is only possible if I calculate with 12 V.
However, the voltage only slightly influences the max torque of a motor; increasing the voltage mainly reduces the max current (by 2x).

You probably want to try the Fly Elise Motion Platform Designer Software to do some basic calculations for your motors.
The basic data required for motor selection are:
• required torque M → ? Nm
• required spee n → ? RPM
• supply voltage U → 24 V in your case
• max current I → ? A

For the power the motor has to deliver calculate POUT = M * n * π /30 /1000
Select now a motor that has a nominal power output 2x the value you calculated.
(Because a typical efficiency of ~50% you will need a motor that consumes about 4x your calculated POUT!)
The required speed [n] has to be higher than half the no-load speed [n0] and the load torque [M] has to be less than half the stall torque [MH]

Based on my calculation the stall torque will be about 60 Nm → you can load your motor with up to 30 Nm @ 24 RPM

@prilad already has given you a rough estimate for the performance you can expect. I have my doubts that these motors will be enough for a decent Stewart platform.

Thanks a lot, I'll try that software and I'll look for better motors.

What kind of motors do you think that is the best for a 6dof sim?. Winch (powerfull and noisy), scooter motors (powerfull but speed very high, need a gear). Other type? I'm looking for a good and cheap motor, jeje.

Best regards
Dualin


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Just too add most 6dof units use speeds around 14 - 35rpm for motor control the only ones that do a decent movement is when they drive it with lineer actuators capable of reaching the magical 1000mm/s speeds where true G forces will be felt.

Hell I use 180 - 160 rpm on dc motors and that computes to about 700mm/s and this is just nice to be running in a race sim, vibration can be that wild you have problems focusing your eyes.

Has anyone considered using gearing to increase the avail torque from the motor.
and yes @value1 stall current for the motors is what i work in, its fairly important, as in this is the torque range that happens when you sim changes direction or holds in weight position. if the motors wont produce enough the desired movement is very poor.

Sorry my 2 cents.

Thanks eaorobbie, what motors are you using? What motors give you 160-180 rpm with good torque?
I'm thinking to use scooter motors that have 400-500 w of power and 400 rpm, but I don't know the value of the torque, but that motors can be used with a 4:1 gear to reduce the speed and go up the torque.

Regards
Dualin


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Hi, Dualin
There you can find 350W gear motor.
http://www.longwaymotor.com/p_detail.php?cata_code=p-17&id=268
I have two ones like this for my future 2-dof sim

Regards,
Ale

Thanks a lot Ale, and one question more. You said that you have 2 of them. How much money did cost to you? I can't see the price in the web. That motor is very interesting.

Best regards
Dualin


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I found it here.
http://longway.en.alibaba.com/produ...&edm_cta=read_msg&edm_time=realtime&edm_ver=e

And one motor cost approximately $110 without shipping