Hi all,
I have been thinking for some time about making a racing motion chassis in the same vain as a D-Box setup with vertically mounted linear actuators, one mounted on each corner of the chassis. But D-Box’s are expensive - or at least they are for me in New Zealand. Also the mechanic in me (was a mechanic earlier on in life) asks the question - “Can we bolt a turbo onto that to make it go faster”. I have a few ideas bouncing around in my head as to how something like this could be DIY built from a mechanical perspective. I’d like to see what is possible with the Granite Devices products as I’d like to support a company that supports us - sim racing enthusiasts.
Now I found a Bosch software that allows for sizing of servo motors for a given ball screw, lifted weight, speed of travel, distance traveled over a period of time. The values I have indicatively entered simply as a starting point are 10mm lead on the ball screw, 150Kg lifted weight, travel speed of 400 mm/s, 150mm travel, and time to travel of 0.5s. It is possible to calculate the inertia values, but they seem to make negligible difference, and the total lifting capacity of 600Kg allows for lots of headroom in any case. The results I got are below:
Average speed: 1800.00 [1/min]
Maximum speed: 2400.00 [1/min]
Effective torque: 2.71 [Nm]
Maximum torque: 3.53 [Nm]
Ext. inertia: 0.0004170 [kgm^2]
If I understand the figures correctly, the maximum torque is through the acceleration period and the effective torque is when traveling at a constant speed once the desired speed of 400 mm/s is reached. The maximum speed is the required RPM of the motor when traveling at the desired speed of 400 mm/s. Keep in mind that these are ballpark figures and equivalent to a D-Box with a turbo bolted on as I believe the D-Box will do 100 mm/s so simply a starting point and perhaps overkill.
Now for the motor and motor drives - this is where I don’t have a good understanding so hoping that people will chime in. MIGE do a 750w motor (MIGE 80ST-M02430 220V 3000RPM 80mm 750W AC Servo Motor) with the following specs:
- Rated Power: 750W
- Rated Voltage: 220V
- Rated Amps: 3A
- Rated Speed: 3000 RPM
- Rated Torque: 2.39 Nm
- Peak Torque: 7.1 Nm
- Voltage Constant (V / 1000RPM): 48V
Am I correct in thinking that the Voltage Constant is the voltage required to keep the motor RPM at 1000 RPM with no load, therefore 144V to keep the motor running at 3000 RPM with no load? If my assumption is correct then while this motor meets the requirements of speed and torque, it would have to be run at higher than 144 volts (I’m guessing ideally the mains voltage of 220V) to actually be able to deliver the required speed and torque with a load. Am I on track so far?
I’m in the process of building a SimuCube, the SimuCube and IONI PR HC are the last two parts I am saving for at this point in time, and from what I know it outputs ~32VAC which is considered “safe” (although I wouldn’t put my hand up to do a touch test). So then I was poking around the GD site and found the BL DC servo motors, which would run off 48V DC and therefore an IONI drive and a 48V PSU like those used with the SimuCube. The 300W BL70 puts out 1Nm - 3Nm of torque with 3000 RPM so its lacking in the torque department. But it looks to go up to a 660W version so those specs might be closer to those required. I had thought about an IONI Cube with 4 x IONI Pro HC installed but I dont think it would have enough current throughput to power 4 motors, and would perhaps have to use 4 x IONI Cube-1x each with its own PSU.
Now having said all of that, I apologise if I have all this wrong. So from here I guess I’m looking for some pointers and to start the discussion to come up with a workable GD motor drive and a motor fit for purpose.
Cheers,
Scott.
