Motion Motor Lifespan

[Infinity]

Had a question concerning the typical lifespan of an electric motor used in DIY motion platforms.

The motors I've seen used so far with the best results are:
- windshield wiper motors
- scooter motors

How long before they burn up?

Any others with good results?

Thanks

[aviaparts]

Hi,

AC or DC motors will last depending on how much you load them. In fact these type of motors are not typically build to allways change of direction. In fact every time the motor goes from right rotation to left or vice versa, it produces a little spark (very little) but it is this spark that causes the motor fo fail in time.

This is the main reason why we use servo motors on our platforms, they are designed for this kind of operation, don't need any extra cooling and have a far better torque.

[Infinity]

Thanks for your reply. So which motion base motor(s) would be best for a home built sim weighing approximately 600 lbs, designed like the one in your photo, balanced with a universal joint. I'd prefer to keep the motors under $100(usd) each. (2dof)

[Roland]

Wear depends also on the choice of gear you make.
Many gearboxes wear-out quickly due to the constant reversal that motion platforms require. The gear therefore needs to be high quality. Gear ratio and the dynamics of your drive will also influence a lot. My drive has about 5~7Hz bandwidth. I'm not sure standard gearing can take that kind of dynamics.
When choosing a DC motor, try if you can find one with 4 carbon brushes iso 2. many industrial DC servo motors use 4 brushes.
Under $100,- will probably only be possible in places like these: http://surpluscenter.com/electric.asp?UID=2009032803172704&catname=electric

In my V-belt driven 3doF system, after two years of regular use, the DC motors don't show any wear yet. (they all are 4 brush types) Only the V-belts that are directly connected to the platform are showing some wear at the center position (where they move over the pulley the most. I could just shift the belts a bit to move the wear area to a place that does not touch the pulley, but I think I just replace them. V-belts are not expensive.

[AndyT]

Used wheelchair motors.
They work great and have plenty of power for what you want.
They are almost always 12v and usually free from the repair shop.

[Infinity]

I've looked into the wheelchair motors, but prefer not to have a chain drive. May come back to that.

So it seems servo is the way to go. Is the gearbox normally built in on these. I see a lot of "servo gear motor." Is that what it means. If not, what specifications (if any) should I look for in a gearbox. I'm concerned about the unintentional reversal that may occur without a worm drive??? Did I say that right?

When looking at different motors, what specifications should I look for such as AC, DC, 12v, 24v, wattage, RPMs, permanent magnet or anything else particular?

[AndyT]

Why do you have to have a chain drive?
you can link it direct if you like. Mount a gear on the motor and put it in direct contact with the linkage.

[Roland]

Concerning choice of motor, gear ratio, rpm, wattage:

You first need to make a good drawing of the platform that you are going to build. Like Andy said, you can choose direct linkage, or linear actuator type of construction. Have a look at Ian's site for some examples.

Then you need to make up your mind how fast you want to make the platform motion:
With the attachpoint of the linkage, this will determine the rpm of your motor/gear system.

The weight & size of the platform will determine the torque that is required, and this translates to motor current, and size of motor.

AC or DC depends on the type of drive that you plan to use. I find permanent magnet DC motors most suitable to build a drive for. Many industrial servo motors are PM DC motors. Generally they have good rpm / torque specs for simple motion platform application.

So a fair deal of planning, drawing and basic calculations are involved if you want to make a good estimation for choice of motor.

Have a look at my 2doF motion pages with platform drive calculations. http://www.simprojects.nl/diy_motion_platform_ii.htm

[Infinity]

Thanks Roland. I've actually been to your site many times. It, with many other sites have prompted these questions. I'm still very ignorant. Could you (or anyone else) recommend a book that discusses in detail the calculations you mentioned in your previous reply.

AndyT, I didn't realize I could do a direct linkage with a scooter motor. Still thinking inside the box. Thanks.

I appreciate all of your inputs. I fell bad like you guys are having to spoon feed me and I don't want that.:???:

[warvet]

I highly recommend Treadmill motors which are awesome for this application.I know because I sell them :) along with treadmills of course :) Here comes the shameless hijack for personal gain ;) if anyone needs any commercial fitness equipment of highest quality at super ridiculous prices, treadmills, ellipticals etc let me know.

Tim

[Roland]

Could you (or anyone else) recommend a book that discusses in detail the calculations you mentioned in your previous reply.
:

Wikipedia gets you quite far. It is all highschool physics, being an electrical engineer, my mechanics knowhow is pretty rusty, so I got most info from wikipedia. I try to keep it simple. measured value within 30% of the calculated value (or visa versa) is good enough for me.

If you have any questions, just ask on the forum or send me a mail.

[Infinity]

Awesome. Thanks for all the help guys.

[AndyT]

Thinking inside the box will get you trapped in a corner. :D