Ringfield with screw fixing brushes

[Brew Man]

I don't have a tender drive Ringfield either but I'm wondering, does not the long screw into the chassis have two functions, 1 to hold the brush and 2 to fix the motor securely in place? It's difficult to see from the diagram.

[Going Spare]

The plastic motor faceplate clips to the metal motor housing, the screws just securing the brush retaining arms and, in the case of the lefthand one on some versions, completing the electrical circuit between the brush arm, motor housing, non-insulated wheels and the rail.

Over the years (before tender pick-ups) there were a number of methods for electrically connecting that brush arm with the motor housing. Others have involved a tab on the side of the brush arm being bent through a cut-out in the faceplate to make contact with a spigot protruding from the motor housing or using a bridge wire from the tab to a connection cast in to the top of the motor housing.

[ColinB]

The screws on the ringfield motor you are talking about a probably self tapping screws. They don't make nylon screws in self tapping styles because as someone mentioned the heads "snap off". In true "bodgit" style someone worked out you could force a parallel screw into previously self tapped hole, again a not very good idea. When I converted mine, I tapped out the two holes to take a M2.5 or M3.0 thread and then used similar thread nylon screws from China (you get a whole bag very cheaply). If you use nylon screws for both brush holders then you don't have to worry about mixing them up when you take it apart in the future. On the later ringfields the plastic brush holder where the screws fix is quite thick, so again I tapped it out to m3 and then used very short 4mm long laptop screws, the plastic is thick enough that they won't touch the chassis. You might have to enlarge the slots in the brush holder plates slightly, but a much better solution.

[Topcat2018]

@Brew Man

By "motor" I presume you mean the armature, as the motor magnet is glued or maybe press-fit into the chassis. The plastic brush plate that holds the armature in place is not secured by screws, nor could it be in the earlier tenders that have short screws. The brush plate has hooked lugs moulded on the back that engage with rectangular holes in the chassis.

[ColinB]

Topcat you are sort of right although two screws hold the two brush plates to the chassis, which by doing so acts a secondary means of holding the plate , So yes the plastic clips do hold it on, but so do the screws.

[Topcat2018]

@ColinB

You can't have two metal screws holding the brush plate to the chassis as both brushes would then be shorted to the chassis. As I said earlier I don't have one of the tenders that has the long screw on the rearmost brush strip, but certainly on earlier ones the screws are short and do not attach the brush plate to the chassis. Through I wouldn't recommend it you can lever the brush plate away from the chassis with the screws in situ.

I am 99% certain that the principal reason for the single long screw on the later tender is to make contact with the chassis and avoid the need for the wire lead and female spade terminal that connects to a male lug on top of the chassis in the earlier tenders. Any securing of the brush plate to the chassis is secondary.

[geordi_q]

@ Topcat

I have checked one of my ringfield motor with screw fittings

The pickup connection screw does not make a connection to the motor chasis

so is ' live' therefore the hole must be slighly larger

The other brush connection is earthed by the screw thus when fitting a decoder

it has to be isolated hence the plastic screw removing the earth with the side connection lifted away from the chassis

Gordon

[Topcat2018]

@geordi_q

I feel as if I am beating my head against a brick wall with these replies as everyone seems obsessed with nylon screws. As I said. I do not have one of these tenders so I can't be definitive, but:

1. have you actually taken out the right-hand screw to see how long it is? The only point of having a long screw in the right-hand hole with a big hole in the chassis behind it to avoid contact, is that the manufacturer could use the same length screw in both holes.
2. as I have said repeatedly, irrespective of the screw in the right-hand hole you don't need to use a a plastic screw in the left-hand hole. If a 5 mm (shaft length) No 2 self-tapping screw in the left-hand hole is short enough that it does not contact the chassis on any of my tenders then it should work on the type of tender shown on Peter's Spares.

[ColinB]

Topcat as I stated in my response, on some you can get away with a shorter screw as you state, but on others there is not enough plastic to use the shorter screw. As I said I retapped them with a parallel thread, much better solution than the orignal design also gives you a larger range of screws to use.

[pendeenpete]

As an aside, has anyone drilled into a Ringfield block? I will have to find a way of attaching a wire , someone mentioned using a self tapping screw? Not sure of the properties of the cast block, whether it would survive? Thanks

[Topcat2018]

@ColinB

I guess it makes sense if there isn't enough plastic to take a shorter screw, but I'm surprised as there has already been a self-tapping screw in the hole. all my tenders that don't use long screws have No 2 x 5 mm (shaft length) self tappers and these is no problem with them gripping.

[pendeenpete]

@ColinB

I guess it makes sense if there isn't enough plastic to take a shorter screw, but I'm surprised as there has already been a self-tapping screw in the hole. all my tenders that don't use long screws have No 2 x 5 mm (shaft length) self tappers and these is no problem with them gripping.

Thanks for replying,I am trying to provide an alternative supply from the actual block as I want to fit a DCC chip,as you know the chip requires the brushes to be isolated from the power supply.

[Topcat2018]

@pendeenpete

You should be able to drill into the chassis block. The metal is quite soft and easily filed, so should be drillable. I have a small bench drill that I use for this sort of thing. If you want to attempt it with a hand drill I would advise centre-punching the drilling point and clamping the chassis block in a vice.

[pendeenpete]

@pendeenpete

You should be able to drill into the chassis block. The metal is quite soft and easily filed, so should be drillable. I have a small bench drill that I use for this sort of thing. If you want to attempt it with a hand drill I would advise centre-punching the drilling point and clamping the chassis block in a vice.

Thanks Topcoat, took a deep breath and did it just now, as you say the metal is soft,seems like zinc, my daughter bought this loco,so has sentimental value.

[threelink]

Reference the idea of drilling into mazak or similar to accept self tappers, yes it can be done but it is easy to tear the threads cut by self tapping screws and easy to split the mazak if it is thin in section. I came across this problem when trying to fix an old Triang L1. The con rod screw had torn out of one of the mazak driving wheels and had been replaced by a self tapper in a botched repair attempt. The result was a hole in the driving wheel which someone had attempted, unsuccessfully, to repair by gluing in the self tapper. Not having a suitable replacement wheel to hand I picked out the glue and drilled the wheel to accept a stub of biro ink tube, superglued in and cut off flush with the wheel boss. A genuine Triang crankpin screw easily cut its own thread in the ink tube. This was intended as a temporary quick fix but the loco has performed faultlessly and the con rods have been off and back on again a number of times so it has become permanent. In the unlikely event of the threads in the biro ink tube tearing all I need to do is pull out the damaged tube and glue in a new one (or buy a replacement wheel).

[pendeenpete]

I drilled into the top of the block well away from the magnet etc, screwed the self tapper in carefully, I put in an old bit of pick up with attached wire under the screw, hopefully it will not need to be moved. Tried the loco on DC while I wait for the nylon screws, all ok.

[The son of Triangman]

To save a lot of drill work and thread tapping you could simply put a single M2.5 or two M2.5 nylon washers directly under the screw head of the right hand factory fitted screw.

[Topcat2018]

@ The son of Triangman

Surely it's the left-hand (rearmost) brush retaining strip that needs to be insulated to prevent it contacting chassis via the screw.

I don't think the nylon washer idea would work because:

1. The forks at the top of the brush retaining strip are bent over at the top so you couldn't get a whole washer under them. You would have to cut away about a quarter.
2. There is lateral play in the bush retaining strip so it could contact the shaft of the screw.

I still think the best solution is a short-self tapping screw, so long as it will grip the plastic after the long screw has been taken out. You can get them as short as 4.5 mm. If the screw won't grip try a spot of Loctite.

I would be interested to know what thickness of material there is at the top of the brush plate on different tenders. On all mine it is about 5.5 mm including the thickness of the brush contact strip

[The son of Triangman]

You insulate both screws. It works fine. The faceplate is non-conductive plastic, so without the screws the contacts are insulated, it's only when the long screw fitted in it's hole touches the chassis casting there is an issue. Simply padding the screws out with M2.5 nylon washers from the top solves the issue as there is no contact between chassis and contacts. Providing the screws aren't screwed into the cast chassis it works fine.

[Topcat2018]

@ Son of Triangman

I'm getting more and more puzzled.

Your original idea was to put one or two nylon washers under the head of the long screw so that it would still be in contact with the chassis but not with the metal brush strip. I explained potential problem of lateral movement of the brush strip and contact with the screw shaft.

Your latest idea is to pack out the long screw with lots of washers so that it doesn't contact the chassis.

The long screw shown on Peter's Spares appears to have about 10 threads which makes it roughly 10 mm long. I can't see the thickness of the plastic brush plate on Peter's Spares, but based on the thickness of my plastic brush plates, if you are padding out the original long screws with nylon washers so the screw doesn't touch the chassis I estimate you are going to need around 10 washers. If the brush plate is thinner you will need more washers.

In other people's replies concerns have been expressed that a short screw might not have sufficient grip in the plastic, However, if the threads of the long screw that are actually still engaged with the brush plates have sufficient grip then so would a shorter screw, so you might as well just use a shorter screw, which would be much neater.

[pendeenpete]

Just thought I would update my problematic Ringfield to DCC conversion. Eventually got the Kadee screws from Guagemaster, they do the job, but you do have to screw them a long way in before they take hold. Quite worried at first, but probably being too nervous.

Anyway the Flying Scotsman is now on DCC. Cheers!