Motor/Gearbox choice. AC/DC - Size - Permanent magnet?...

Hello,
First post here, and long one at that.
I have been following with great interest this forum for a while.
Lots of interesting posts and many awesome simulators.
I have been wanting to do this for a long time, and I decided that now is the time for me to build one.
Call it my mid-life crisis.

I would like to build a 3dof racing platform.
That is really, a seating platform lifted up by 3 motors in a triangular fashion.
The motors would have a 10cm lever each to allow for vertical and lateral motion.
I am currently looking for motors, and feel like that there are still a few things that I am not clear about.

From my preliminary calculations, if I need to move a platform that is 180Kg, (driver with seat/pedals structure), I will have 60Kg per motor.
If I am trying to have a MAX vertical motion of about 20cm, I need to have levers of 10cm on each motors.
From the 12Oclock position, to the 6Oclock position would give me the 20cm travel I want.
If I calculate correctly, 60Kg at 10cm would be about 60Nm. (Is this correct?)
That is a decent amount of torque.

I have the opportunity to purchase some gearboxes that have a motor frame 56C.
These are pretty big, but would allow for some good motors to be used.
Specs are 1:25 ratio, 0.9HP input max at 1750rpm.
Max output torque is 700Kg/cm. (68Nm)
This should allow for some decent simulation.
Do these specs seem OK for this application?

Now, I need the motors to go with that, hence my questions...
1- Is there an absolute preference to using DC motors to AC motors? why?
2- What should be the typical gearbox output rpm to allow for some fast motion with a 10cm lever arm (20cm max motion on a 180degree gearbox turn)?
3- The gearbox states 0.9HP input max at 1750rpm. Does that mean that the motor output (unloaded) should not exceed 1750rpm?
4- Is 20cm of possible travel sufficient to have a good simulation (where the 3 motors are lifting the platform)
5- Are permanent magnet motors not possible to use? (I find many motors that are cheaper, with permanent magnets)
6- For the design I am looking for, should I really have 4 motors (in each corner) instead of 3? (This would also reduce the load per motor)

I am in touch with motioncontrols in the UK (I am in the US), and I am looking at their ZYT90-199 motor, with a custom gearbox.
They have not come back to me yet, not sure that this combo would meet my requirements at this time.

I hope that someone will be able to answer these questions.
Of course, after that comes the questions of controller, depending on what motors I can pick.

Thank you very much for your help.
I look forward to posting my progress here once I have purchased the first elements.

Arno

wow !!!!i think you made you home work . i wish i could help you . but i new to . and i looking for the same set up as you
regards pat

Arno,
I'm using 1hp AC, 60:1 gearheads, output torque EACH - 117 ft. lbs x 3 - for 3DOF.
"Me thinks" that most builders have looked at platforms period, coupled with AC motors as a "joke" for lack of better terms. If we look at the CKAS, 3/4hp Sew motors/helical gearheads, with an output of 86 ft.bls.
Their degrees of operation was +-4 degrees for a total of 8. IT IS SLOW compared to most of the other types of racing simulators....
However, the thought process here with a bunch of great guys, it to make a platform type sim just "rock".... by changing frequencies with the VFD's, great electronics and software, we, as a team, can make a
wonderful and fast platform type. NO, it will never be as fast as some DC setups, Wiper Motor Setups etc., but as an end result, will give great immersion factor.

Have a blessed one,
Tom

PS - AND another biggie - AC / Platform Sim Type requires: Good strong inverter duty motors, Good strong gearheads, VFD's, - ALL of these ARE VERY EXPENSIVE!

@CTF , Arno, your frame design could be done with 12v motors and 50:1 or 60:1 gearboxes on them, or make up an actuator yourself.
I use 12v motors for safety and easy to set up.