Ringfield with screw fixing brushes

[pendeenpete]

I recently received a Flying Scotsman which has the screws fixing the brush holders, I want to fit a decoder. As you know the rear brush must be isolated, Peters Spares have nylon screws to do this, but at £3 plus £5 postage for screws that are not the right thread, these won't be purchased by me. Anyone know the thread size of the original screws?

[Topcat2018]

This is news to me. I have a large collection of tender-driven A1/A3/A4 and as far as I am aware there are only two types of tender (but not being the Pope I'm not infallible):

1. British-made ones where the plastic plate carrying the brush contact strips is held in place by clips on its back side and the brush contact strips are permanently fixed to this by hollow rivets. The brush contact strips are folded in half and you have to bend them back to get at the brush springs and brushes. The left hand (rear) brush contact strip is wired to chassis.
2. Chinese-made ones where the plastic plate carrying the brush contact strips is also held in by clips. The brush contact strips are a single layer and you have to unscrew two self-tapping screws and take off the strips to get at the brushes. These screws do not make direct contact with the chassis, but the left-hand brush contact strip is wired to metal strips that contact the right-hand wheels and the use of nylon screws will make no difference. It's actually superfluous on the Chinese locos as both power connections come from the loco, through the drawbar to the tender, so you can cut this wire.

If your tender does have nylon screws I would be very interested to see a photo.

As regards the thread size, the thread will obviously be metric. M3 would probably be too big and as far as I aware the smallest nylon screw size is M2, so unless Hornby used a custom size, this is the best bet. They are available quite cheaply on Ebay (£1.75 for 10, free postage).

[geordi_q]

@ topcat

The several types of ringfield brush holder fittings

The installation guide for fitting decoders in the support section shows a picture of the The Flying Scotsman the poster is tying to fit to

Gordon

[Going Spare]

There was a period immediately before the transfer of production from the UK to China (1995-1998) when A1/A3 drive units had screw-on brush retaining arms but no tender pick-ups (see Service Sheet 204) so the brush arm retaining screw did make contact with the metal motor housing to complete the electrical circuit.

These locos are likely to have retained imperial threads.

Which model do you have (R-number)?

If you have not purchased any, why do you say the nylon replacement screw is the wrong thread?

[Ruffnut Thorston]

@ Going Spare...

Peter's Spares themselves say that they are not the same thread...wink

"Are you trying to convert Hornby ringfield tender drive units to DCC? If you are and you come across the latter models where the screw connects all the way into the block look no further we have found some nylon screws to replace the metal Hornby one. (Please note they can be screwed into the block & taken out when needed but please take care not to over tighten & snap the screw, they are not the same thread they are just right to force in & nip up tight to fix the carbon brush holder, they will flex as they are nylon when screwing them in) we have used these on loads of Hornby Conversions and can now offer them for sale."

https://www.petersspares.com/peters-spares-ps13-nylon-screws-for-hornby-ringfield-dcc-conversions-pack-of-10.ir

[Topcat2018]

I've got over 40 tender-driven A1/A3/A4s and as I said earlier I've only seen two different types of tender drive. Would love to see some photos of other types.

[Going Spare]

@ Ruffnut Thorston

Thank you - didn't read the small print on Peter's site!

Nonetheless, if you take their statement that they have used them on "loads of" DCC conversions (presumably without any failures), they evidently do the job well enough.

[96RAF]

I have used these nylon screws.

The screws are the wrong thread but can be coaxed into place by tightening, then releasing, as if you were tapping a thread in a hole, but this is reforming the screw to match the hole.

Look on Brian Lamberts web site for how to convert any of the six ring-field variants to DCC.

[pendeenpete]

I'm sure they work, however, if the postage is correct, that means the items are considerably over priced, the type of motor in my Flying Scotsman is referred to as a type 2 Ringfield by Brian Lambert, a photograph is shown on his site.

[Brew Man]

If you can find out what size they actually are, I am sure you'll find them much cheaper of eBay or even hardware shops.

[Topcat2018]

Brian Lambert's site runs to about 16 long............. pages. The actual URL of the page where the photo is located would be more helpful.

[96RAF]

His site does have navigation aids pointing to DCC and Ringfield motors.

https://www.brian-lambert.co.uk/DCC-Page-1.html and scroll down to ringfield.

[Brew Man]

I'm sure it's not difficult to find.

[Rana Temporia]

Someone at work gave me a set of small taps and dies a good few years ago. Invaluable for checking thread sizes on small screws and bolts. They have enabled me to get the right sizes for a multitude of locos that otherwise would still be waiting for parts off scrappers. No idea how much a set is nowadays but if not much I’d get a set of small BA sizes for UK made locos and a set of small metric ones for everything else.

[pendeenpete]

Well, I have found a possible alternative, apparently Kadee do a nylon screw that fits, I've ordered some (12) for £4 including postage. 48 HR delivery! If it works I will let you know if interested. £1.50 is a normal amount for something that weighs the same as a stamp.

Thanks for your interest, good idea about the taps and dies, I will still need to drill into the block somewhere to attach the other wire.

[Topcat2018]

@96RAF Sorry to contradict but this is the drop-down menu from the Page Quick Links under DCC on Brian's website. I don't see ringfield.

There are Page Quick Links under other headings but I still don't see anything relating to ringfield.

[The son of Triangman]

M2.2 fit, you should be able to get M2.5 fit as well. Readily available from most electronics suppliers.

[Topcat2018]

Firstly, correction to my original reply. On my Chinese-made tender it's the right-hand brush contact strip that connects to the contacts that engage with the right-hand tender wheels. The left-hand brush contact strip is connected to chassis via a wire and spade terminal.

Having said that, I'm working in the dark somewhat as I don't have one of the later tenders, but referring to the tender shown on the Peter's Spares website:

1. Obviously the self-tapping screw on the right does not contact the chassis.
2. There is no wire or spade terminal on this tender. The self tapping screw on the left seems very long, presumably so that it does contact the chassis and avoids the the need for the wire and spade terminal.

If this is the case, why not simply use a shorter self tapping screw on the left so it doesn't connect to the chassis? Why a flimsy nylon screw?

[pendeenpete]

Firstly, correction to my original reply. On my Chinese-made tender it's the right-hand brush contact strip that connects to the contacts that engage with the right-hand tender wheels. The left-hand brush contact strip is connected to chassis via a wire and spade terminal.

Having said that, I'm working in the dark somewhat as I don't have one of the later tenders, but referring to the tender shown on the Peter's Spares website:

1. Obviously the self-tapping screw on the right does not contact the chassis.
2. There is no wire or spade terminal on this tender. The self tapping screw on the left seems very long, presumably so that it does contact the chassis and avoids the the need for the wire and spade terminal.

If this is the case, why not simply use a shorter self tapping screw on the left so it doesn't connect to the chassis? Why a flimsy nylon screw?

 

 

[pendeenpete]

Not sure what the problem is using a shorter screw, might be people not wanting to advise that, just in case there is still a possibility of intermittent connection, anyway,with the price of decoders, (and everything else) these days, I have bought the screws,so just got to work out where to attach the wire from the block.

[96RAF]

@TC

those quick links in the drop down menu simply scroll down that page I linked to and the link you want is DCC Installations, then continue to s roll down until you get to ring-fields, else scroll down manually from the top until you get there.

All queries about the website should be addressed to Flashbang on this forum who’s website it is.

[81F]

You are right the Peters spares screws are not exactly right but after some trial and error I have managed to get them to fit. First you shorten them and then try to screw them in. I diid about half a turmn in and a quarter back taking them out every so often to clear the swarf. Be careful though as it is east ro smap the heads off..

Another method was to get some plastic tubing just big enough to screw the Hornby screw in then (assuming none of the screw has cut through to the outside of the tube, drill out the hole in the chassis to accept the now threaded tube and supeglue in place. Only downside to this is it is safest to tahe the plastic cover plate off the motor.

Hope this helps.

[The son of Triangman]

M2.2 or M2.5. 6mm nylon cheesehead screws work fine. I usually buy a bag of 1000

[Ruffnut Thorston]

Service sheets shewing the Ringfield motor version with screw fitted brush retainers...

Example. GWR 2800 Class 2-8-0 loco.

Margate made. 1992.

China made. 2000.

[Topcat2018]

I can't speak for the type of tender shown on the Peter's Spares website as I don't have one, but on the tenders I do have I have found the following:

1. The shaft length of the self-tapping screws is only 5 mm.
2. The thickness of the plastic brush plate plus the brush holder strip is 5.5 mm.
3. There is a hole 10 mm deep in the chassis behind the brush plate. Presumably this does not exist on later chassis.

Conclusion. As I suspected the long screw on later chassis is simply to avoid the need for a wire and spade terminal. If you replace the long screw with a No 2 self tapper having a shaft length of 5 mm it will not contact the chassis. If you are still worried put some thin insulation between the brush plate and the chassis.

I wait to be proved wrong but until then I consider that all this nylon screw business is complete nonsense, a red herring.