'Chipping' and old Hornby loco

[GregusGWR]

This is my first post so I hope this works.

I have some old Hornby locos with the metal frame with magnet and allow holder connecting them with a nut and bolt. The brushes are held to a fibroboard/bakelite board with a copper strip and u shaped wire spring  .

How the heck do you isolate the pickups from the motor? The bogie frame is part of the power pickup system. Old Hymeks, Class 37s and Craven 117 DMUs are powered by these as well as Pullman power cars and Dock shunter.

Any ideas?

Edited September 29, 2018 by GregusGWR

[34theletterbetweenB&D]

Welcome, and these are the simplest in the world in the world to convert.

 

In short, take the wired connection to the brush off the spring. Take the insulator sleeve from this spring, cut in half, and replace on both springs so the brushes are now isolated by the insulating sleeve. Connect decoder red to the pick up strip, black to the tag under the motor securing screw, orange to the brush that had the wired connection, grey to the other brush. Converted. (Wasn't it thoughtful of Triang to make the insulating sleeve many times longer than required?)

[GregusGWR]

Welcome, and these are the simplest in the world in the world to convert.

 

In short, take the wired connection to the brush off the spring. Take the insulator sleeve from this spring, cut in half, and replace on both springs so the brushes are now isolated by the insulating sleeve. Connect decoder red to the pick up strip, black to the tag under the motor securing screw, orange to the brush that had the wired connection, grey to the other brush. Converted. (Wasn't it thoughtful of Triang to make the insulating sleeve many times longer than required?)

Many thanks. I've done something like that and when I put the motor bogie on the rails of the programming track it resets the controller so there is still a short somewhere. I'll get the multimeter to it and check everything. Tomorrow's task. It's 9pm now. Cheers.

[34theletterbetweenB&D]

Having taken a walk to clear the brain fug (got a nasty cold going) I have realised that I jumped to the dead simple XO3/XO4 open frame motor configuration. The power bogie arrangement of this motor type isn't quite so simple, and comes in significant variations. The common factor remains putting insulating sleeve on both ends of the wire spring where they bear on the brushes.

 

But you have to study what other connections are made to the brushes by either or both of the structure or copper coloured pick up strip material too, and eliminate these. The first class 37 power bogie for example is very simple, eliminate a short tag that rolls over the plastic frame, against which one brush bears. I don't know all the arrangements that were used, so hopefully others can advise.

[GoingUnderground]

The ex-Triang motors are ridiculously simple to convert as "34" has described, even the motor bogies. The only downside is that they are relatively current hungry, so a decoder which can only provide 500 milliAmps might burn out. Fortunately there is usually plenty of space to fit a decoder with a higher current rating, and to be safe, look for one with at least 1 Amp output.

 

What you have to watch out for are the Meccano/Hornby Dublo motors, of which some are much harder to convert as one of the carbon brushes is held in a metal sleeve that itself is mounted in the chassis and so that brush cannot easily be isolated from the chassis. It can be done but it means removing the metal brush sleeve from the chassis and drilling out the hole in the chassis to take an insulating sleeve to hold the metal brush holder.

 

Also some of the Rovex/Hornby Railways/Hornby Hobbies "ringfield" motors from the post Triang-Hornby era have a metal screw that forms an "invisible" link between one motor brush and the chassis, but these are easier to convert as the screw can be replaced with a suitable nylon one.

Edited September 30, 2018 by GoingUnderground

[GoingUnderground]

Having taken a walk to clear the brain fug (got a nasty cold going) I have realised that I jumped to the dead simple XO3/XO4 open frame motor configuration. The power bogie arrangement of this motor type isn't quite so simple, and comes in significant variations. The common factor remains putting insulating sleeve on both ends of the wire spring where they bear on the brushes.

 

But you have to study what other connections are made to the brushes by either or both of the structure or copper coloured pick up strip material too, and eliminate these. The first class 37 power bogie for example is very simple, eliminate a short tag that rolls over the plastic frame, against which one brush bears. I don't know all the arrangements that were used, so hopefully others can advise.

The Tri-ang motor bogies had two basic designs:

 

1. The "Bo-Bo" design, dating back to the mid 1950s, as used on the SR 2-NOL lookalike EMU, the Cravens Class 117 DMU, the Blue Pullman, the AL1/Class 81, the dock shunter, the Sydney Suburban "Red Rattler" EMU, and all the Transcontinental diesels and double ended electrics, but excluding the 0-4-0 steeplecab which has the classic XO4 motor, and also excluding the Budd Diesel Railcar which used a variation on the Co-Co motor bogie design, see below. I think initially the Hymek used the Bo-Bo design but I haven't got one on hand or the service sheet to check.These do have a live chassis/frame and have a copper or phosphor bronze strip that touches the motor magnet at one end and the brush spring at the other. Remove that strip, which is easy to do as it's not fixed to the insulation board just held down by the brush spring, and you've isolated the brush spring from the chassis. But you can leave the strip in place if you want and just fit an insulating sleeve to the end of the brush spring without a sleeve just as if it were an XO4 motor. Dead easy, a 1 minute conversion at most.

 

2.The "Co-Co" design, introduced in 1960, which "34" has already covered, was used on the EM2/Class 77, Class 31 and Class 37. The Transcontinental series Budd Diesel Railcar, and later (post 1967?) Hymeks, also use a variation on this design as well even though they do not have a Co-Co wheel arrangement. The bogie chassis/frame is insulated from both rails by the nylon axles on the wheels. Take care with these locos. The ends of the nylon axles wear down, and in a worst case scenario the wheel might momentarily touch the chassis or the "magnadhesion" magnet, making the bogie chassis live. This wouldn't matter, but the screw that holds the brush spring in place and acts as the bogie pivot securing screw is metal and its square head is above the motor magnet. So to be safe, remove the black plastic moulding that fits over the motor magnet and pole pieces and put a thin piece of card or plasticard on top of the magnet and pole pieces to insulate the brush spring screw head from the motor magnet and chassis. As the phosphor bronze track has to be cut away so that it doesn't touch the brush arm (fortunately the track can be unclipped easily from the black plastic housing for trimming and then replaced just as easily), it is a slightly more time consuming conversion, but probably will take no more than 5 minutes.

Edited September 30, 2018 by GoingUnderground

[Crewlisle]

...................What you have to watch out for are the Meccano/Hornby Dublo motors, of which some are much harder to convert as one of the carbon brushes is held in a metal sleeve that itself is mounted in the chassis and so that brush cannot easily be isolated from the chassis. It can be done but it means removing the metal brush sleeve from the chassis and drilling out the hole in the chassis to take an insulating sleeve to hold the metal brush holder.

 

 

I have a Hornby Dublo/Wrenn Duchess.  This loco has a cast chassis, cast body and driven by a powerful, quiet motor in the firebox.  It easily starts six coach expresses on my 1 in 38 approach to the high level terminus without slipping so it was worth the effort to convert it to DCC.  To convert Wrenn or Hornby Dublo locos to DCC both brush holders, which pass through the chassis, have to have a plastic insulating sleeve fitted.  The rear wheels were removed.  This was easy as I had previously fitted the correct size Romford wheels.   After the old brush holders were carefully removed, the armature could just be moved enough to allow the existing brush holders to be drilled out.  This has to be done with a hand drill and very carefully to avoid any damage to the armature.  Keep the motor brushes, end plugs and brush springs.  For the insulated brush holders I used ‘Evergreen Strip Styrene’ No. 226 which has an internal diameter equal to the diameter of the motor brushes and brush springs.  The external diameter is 4.76mm and when drilled to this diameter is a push fit through the chassis.  The insulated brush holders were cut so that one end was about 2 to 3mm from the armature and projected out of the chassis the other end by about the same.  The orange and grey wires from the decoder were each soldered to one of the original brush holder plugs and the brushes, springs and plugs were inserted into the brush holders.  The end of the plugs can be opened out so they are a tight fit to keep the springs and brushes in the holders.  The track supply from the insulated wheels was soldered to the black decoder lead and a hole drilled and tapped 8BA into the chassis to pick up the red supply, ie the supply from the non insulated set of wheels which make the chassis live.  Two things to remember when converting Wrenn or Hornby Dublo locos:

 

1. If you dismantle the two arms of the magnet, it will probably require re-magnetising.  After I had finished and was running the loco I noticed that I had to apply about 75% power to start and then throttle back to control the loco.  I tried various settings on the CVs to improve the starting characteristics without success. I had fitted a ZTC decoder, so I rang ZTC, told them the symptoms and they diagnosed that the magnet required re-magnetising.  The last time I had this done was about 20 years ago but was told by ZTC that they naturally lose their magnetism.  I ordered one of the new NE magnets from Tony Cooper in Accrington and the improvement in performance is excellent.                                                                                                                  
2. To assist the brushes to bed in, carefully file the ends of the brushes to the approximate diameter of the armature.  As they bed in, control and power will improve..

 

Peter

Edited October 1, 2018 by Crewlisle

[JST]

I had my old Wrenn "Dorchester" converted and had the magnet re-magnetised but also the armature rewound. Works a treat!