Friday, August 23, 2013

Anton's 75' turntable motor and gearbox replacement

I have not been happy with the noise and operation of the motor/gearbox combination supplied in the Anton's 75' turntable. For some time I have been contemplating replacing the motor/gearbox with a combined 12v DC motor and gearbox available from Jaycar Electronics. In the intervening period I was given a similar motor/gearbox from a friend so I recently pulled the original motor/gearbox out and did a simple replacement. I retained the pulley system and the increased torque available from the new motor overcame the turning hesitation that was sometimes evident with the original motor/gearbox.

The current Jaycar motor/gearbox ($19.95) should be quite OK to use although the hole in the small pulley will need to be enlarged with a 4mm or No.18 or 19 drill as the Jaycar gearbox has a 4.2mm dia. shaft. This motor is 12v DC and runs at 36RPM so when wired in using the original motor wiring including the capacitor across the motor terminals, the trim pot on the existing circuit board can be used to adjust the table turning speed. The existing pulley ration of course means that it should run nice and slow.

As can be seen from the photo below, I simply used a wire twist tie to hold the new motor in place, the wire passing through the original motor mounts. I will replace this of course with something a bit more professional. The original set up has a nylon adjusting screw that pushed the bottom of the motor/gearbox away from the mounting frame thereby tightening drive belt on the small top pulley. I managed to lose the small nylon screw but had a suitable metal replacement (2mm metric bolt I think). The new motor wanted to slip sideways off the tensioning screw so I made a 'saddle' from a piece of brass tube to which I soldered a larger nut, the end of the tensioning screw sitting inside the nut. While the nut can't be seen in the photo a little study will show why it is required. This saddle could be made from a piece brass sheet.


The outcome was a very quiet drive with enough torque to eliminate the turning hesitation (slipping/almost stopping at times when turning) of the original drive.

Here is a video of the drive in action, the video camera is sitting on the baseboard and the drive is under the turntable, you have to listen very carefully to hear anything in the video. The drive does make a little noise in operation but nothing like the high pitched noise of the original.

5 comments:

John Z said...

Hi Ray,
Another option that I would consider is a microwave turntable motor. They should be ideal as they turn at 2 to 6 rpm. Unfortunately most run at mains voltage but there are some that operate at safer voltages (21V AC)like the one I found at http://www.ebay.com/itm/New-microwave-turntable-synchronous-motor-21VAC-21V-AC-/180921507195

Also a bit less expensive than the Jaycar option.

Cheers
John

Ray P said...

Hi John

The good thing about this conversion is that you retain the existing pulleys and it gives nice control and little noise.
As you know I am about to remove the 240v lighting from the layout and replace it with LEDs, I was never comfortable with 240v in the benchwork but as long as it is properly insulated and wired it should be OK.

Ray

Iain Robinson said...

Being completely cack-handed when it comes to making anything work, I am in awe of your skills. I remember making a Meccano turntable from an article in the Railway Modeller about 40 years ago (!)...it didn't work very well :-(

The loco is a delight to my eyes, more accustomed as I am to two-foot gauge locomotives. I also love the skeletal shed scene with some very fascinating locos posed about...and the little dog- perfect!

Ray P said...

Iain

Thanks for the praise but I really should point out that the shed is half finished. I stalled when I decided to put lighting into it with suspended lamp shades using SMD LEDs (made but not installed). I am still working out how to wire it and not have it show. Actually I do know how I will do it, I am just procrastinating about starting it again. Too many other interesting things to do now that I am retired, I must put it back on the list.

Ray P

Ben Noakes said...

Beautiful work, nice and smooth and much slower.