Big ring gear for a DIY turntable

[RAF96]

I have a DIY turntable that uses the central pivot (1/4" stereo jack and socket) to transfer power to the table bed and associated leds that tell me of the bed 'polarity' with respect to the DCC track. I switch this polarity by way of a DPDT switch. That bit works fine.

 

The TT at present is man-draulic in that I have not yet devised a reliable way to power it. I am not too bothered about DCC control and/or indexing and will be happy eyeballing the road stops under control of an (On)-Off-(On) sprung switch.

 

My problem is to motorise it I need a large ring gear or even a pulley to attach to the TT bed driven by a spares box (correctly geared for the TT rotation speed) 12vDC motor/gearbox.

 

Can anyone point me at a retailer of large diameter (approx. 12" diameter or so and probably plastic?) ring gear with associated pinion or do I have to find an old belt driven record player to plunder and adapt.

 

Were I richer and more au-fait with the discipline I would look at a 3-D printed gear.

 

Thanks Rob

[Junctionmad]

Don't see why you want such a big gear , why not Use a gearbox motor and then a more conventional toothed pulley drive to the table

[Free At Last]

I found that a large drive wheel gave a smoother drive and also acted as a reduction gear on an old turntable I made using the spindle from a cycle wheel as the bearing and the 'hole' for the drive wheel.

 

 

[Talltim]

This is a bit small, and you'd have to build a jig (out of Lego?) to centre it. Compatible with a large range of precision moulded gears

Edit: just looked at the prices, maybe not!

[PatB]

Would it be possible to cobble something together using an inside-out toothed belt from, say, an old scanner or printer, stretched around a disc of ply or MDF? You could then drive it using a pulley from the same source as a pinion.

[IWCR]

Spirograph  used  plastic  gears  including  a  large  ring  gear,  probably  only about  5"  OD  though.

 

Pete

[28XX]

Would it be possible to cobble something together using an inside-out toothed belt from, say, an old scanner or printer, stretched around a disc of ply or MDF? You could then drive it using a pulley from the same source as a pinion.

I like this. The wood disc would need to be very accurately cut and centred, or the motor and pinion could be fitted on a hinged mount and sprung against the wood disc to ensure positive mesh and accommodate any eccentricity.

[Junctionmad]

The idea of useing a large gear or pulley is actually daft. , first you'll need very good concentricity , as radius exacerbates that , secondly you need accurate alignment or you'll suffer belt tracking issues. Also direct driving this from a motor is unlikely to offer the reduction ratio needed.

 

Cheap gearbox motors are widely available and then you can use conventional off the shelf toothed drive belts/pulleys. Yes you will have back lash , buts that's the case with any gear system

 

Alternatively you can use direct drive or geared stepper motors for very precise and smooth operation

[PatB]

I like this. The wood disc would need to be very accurately cut and centred, or the motor and pinion could be fitted on a hinged mount and sprung against the wood disc to ensure positive mesh and accommodate any eccentricity.

I can think of a couple of ways to get an accurate circle without a lathe, the simplest probably being a lash up with a pair of dividers and a blade of some kind. It would be a bit laborious though.

 

I almost certainly would go for the sprung motor mount anyway. I think I probably would with a bought in gear too, because however accurate the gear you've still got to mount it.

[tamperman36]

You could try contacting your local council refuge collection service, as most councils collect old/scrap electrical equipment now as it is no longer supposed to be disposed of in normal household waste. You may be able to find an old record player or microwave with a turntable drive.

[DCB]

That 1/4" spindle sounds very small.  Free at Lasts  Bike spindle is a better size for a pivot.   If you want a gear ring most push bikes have one or more , and a drive chain and gears from 28t to 14t or even 12t  Old deraillieur gears have even smaller toothed jockey pulleys and of course spring loaded tensioners.  

Push bikes can be found at Recycling centres, abandoned outside supermarkets and at stations See Pic

[RAF96]

I like the abandoned bike bits ideas and the inside out belt drive which would glue to an embroidery ring. Concentricity would be a challenge but not insurmountable with care.

 

I am stuck (and happy) with the existing 1/4" stereo jack as a pivot and power transfer device so any TT drive mechanism has to be built around this basic feature.

 

I have a Maplins/other make motor gearbox assy that will configure down to 2 RPM on a 2 mm output shaft. Just need a way of making that work with the existing rotationaly dead TT bed.

 

MY original proof of concept rig what for this box to run a friction drive tyre onto the top of the TT mounting disk but this limited rotation to less than 180 deg which at the time was acceptable to purpose - not so now.