Author Topic: The Tale of the GWR Railcar .... 2006 to 2015 (or perhaps 2016).  (Read 7063 times)

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Offline John Candy

A long time ago, I acquired on Ebay (from someone who has since become a member of this forum ... G3F was not formed until 2009) an untouched GRS kit for the GWR/AEC diesel railcar.

It sat in the box for a year or more but, in a spurt of enthusiasm, I then made a start on what I thought would be a quick project.
The body castings were cleaned of flash, the cell pack, ESC (Electronize FR8T) and other components were installed under the floor : It was immediately apparent that the floor lacked rigidity and would require reinforcement.

Next the two motor bogies were assembled. The power units are in fact two re-gauged Aristocraft bogies (I was told by Michael Adamson that the kit must be one of the first batch of 10 kits, since later batches were fitted with USA Trains power units) but "clothed" in very nice (whitemetal) highly-detailed castings which were very clean and crisp (obviously from new moulds) and were easily assembled.
The unfortunate thing about them was that they were structurally very weak, a result of the cross-members which secured them to the power units being also of thinnish whitemetal.
No problem with the sideframes (strong and with superb detailing) .... just that the whole structure was let down by the weak cross-beam mountings.
Combined result of the flexing floor and flimsy bogie frames was that the whole project was shelved in favour of other (at the time thought to be simpler!) GRS loco. kits.

Last week (having completed the Sentinel project locos) I resurrected the railcar, with renewed enthusiasm.
The bogie castings were removed from the power units and "beefed-up" with flat steel and brass channel. They are now very rigid and "knock-resistant".
The method was to take some steel flat strip, cut it to the width between the side frames, drill it to accept the existing motor block mounting screws and drill for two further 6BA bolts to secure the steel to the whitemetal cross beam at the outer ends (as well as at the inner motor block mounting points).
I decided that it would be better to leave the soldered whitemetal beams in place, rather than to attempt to replace them by soldering or glueing the steel strip to the sideframes (which would be unlikely to produce a satisfactory result). The result was a very rigid central crossmember.

Next to be tackled were the two cross members at the outer ends of the bogies. These flimsy whitemetal parts had been  bolted through the side frames and rested on small central spigots which project from the motor block. Again I decided it would be better to leave the original castings in place and "beef-up" with metal .... this time I employed brass U-channel.
Again this was cut to fit between the existing side-frame mountings and filed to clear obstructions and I then filled the channels with Isopon P-38 and pressed them onto the whitemetal beams. After leaving for a couple of minutes (before the P-38 sets rock hard) I trimmed away the excess which had oozed out. After 30 minutes, the whole structure was as rigid and strong as you could wish for (and, if necessary, the bogie frames can still be removed in one piece by removing just two screws from each bogie).

Next the flexing floor needed attention and a strip of flat steel was bolted along the entire length of the underside, offset to one side to clear the bogie pivots and the already fitted underfloor components.

Since then I have been concentrating on installing the remainder of the electronics, which has involved a lot of wiring (much of it running the full length of the carriage).
The radio control will use 3 channels : Speed/direction ; two-tone horn and the lighting regulator (which has 4-way setting options for the head lamps and tail lamps).

A few photos follow to illustrate.
More soon.


1) Floor from above with straight row of nuts indicating the location (on underside) of the reinforcing steel strip.

2) Underside of floor showing cell pack, Electronize ESC and other minor components (the "side skirts" of the bodywork will conceal these from view.

3) Underside of power bogie showing steel strip bolted to cross member.

4) Bogies showing end U-channel fitted over the end cross member castings.

5) Power bogie in situ, showing end strengthening channel and restraint chain (to prevent bogie swinging when removed from track with attendant risk to power feed wiring connectors) note also the floor strengthening bar.

6) Another view of bogie showing cable connector linking power feed to bogie as well as chain.

7) View of luggage compartment and No.2 cab with sound and lighting regulator electronics fitted to floor (a lot of wiring still to be connected).

8 ) Underside of roof with speaker and sound card mounted above luggage compartment.

« Last Edit: Dec 07 2016 04:48 by John Candy »
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Offline Geoff Nicholls

that seems to be progressing well. The electrics/electronics is the bit I least like doing, but it does enhance the experience of running the models, so please could you give us a "for Dummies" guide to how you're doing it: which lights, what sound card etc?

Offline John Candy

A brief resume.

The sound card is MyLocosound (made by Peter Lucas/"Moonraker" on this forum) they are available from Peter Spoerer in UK.

The whistle control relay is made as per instructions at

The lighting control is made up of two components:
a) a two-way digital switching device "ARCS2" available from

this feeds into

b) a home-made DPDT relay unit with a 5V regulated output (to LEDs) .

This combo gives four switching combinations governing the head lamps and red tail lamps which can be switched by radio control according to direction of travel or just red lamps if "parked".

In the case of this diesel, I have decided only to permit the "tickover" (stationary) engine sound in addition to the two tone horn: The motors/bogies make enough sound when in motion and the sound card really is not capable of producing the sort of throaty roar made by a pair of AEC-Ricardo engines at full throttle (the engines were derived from those used in London buses of that era).

If you want to use the full range of engine sound, then just two extra wires are required BUT to permit "coasting" you would require another DPDT relay unit as described at

More detailed info in due course but I am too busy at moment to draw circuit diags.


P.S. The comment regarding "coasting" applies only to diesel sound cards and not  steam sound cards, which are now available with a built-in "coasting" function.
My fellow Members, ask not what your Society can do for you, ask what you can do for your Society.

Offline blagdon

John, does your sound card

 i) sound like a pair of 1930's AEC London Bus engines?;

ii) go up through the gears, thus recreating the semi-automatic epicyclic gearbox of the prototype? (for reference listen to No 22 at Didcot).

Ian the Gauge '3' Pirate

Offline John Candy


As I said above, I have limited the sound output to the horn and engine "idle" since the throaty roar of a pair of AEC-Ricardo 8.8 litre engines at full throttle is not within its for changing up through the gears!!

In fact the pair of motor bogies themselves give out quite a nice "growl" under acceleration.

My fellow Members, ask not what your Society can do for you, ask what you can do for your Society.

Offline John Candy

Update on lights and sound.

Regarding the lighting controls, I find that I actually posted details of these several years ago!


Having adjusted the idle speed/volume of the sound card, I decided to link the traction motors to the sound card and was surprised to find that it actually sounds far better than I had expected. On acceleration from stationary, the car speed matches quite nicely to the increase in engine revs.  as it moves away and once speed reaches a certain point, the sound output merges with that of the bogie "diddly-dum" and the hum of  the traction motors. It reminded me of the sound of the two-car Cravens unit which used to shake and rattle  along the Sudbury to Marks Tey branch on my way to the City in the early 1980s!

Haven't tried it yet on a gradient but (since the sound card output is controlled by traction voltage) I am hoping that starting from a standstill (going up grade) will produce realistic engine-revving before the car starts to move.


« Last Edit: Dec 07 2016 04:45 by John Candy »
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Offline John Candy

Railcar light switching circuit.

The two components are a commercially available radio controlled two-way switch (ARCS2 from ) and an auxiliary DPDT relay unit (home-made).

The circuit diagram is below but first there follows a basic description of how it functions.

The ARCS2 has two latching independent on-off outputs which are of negative polarity (it's like having two separate single-pole on-off switches). One output (referred to as "A") controls the negative supply to the relay coil on the auxiliary board, while the other(referred to as "B") controls the negative supply to the (white) headcode LEDs.

Position (1)
"A" and "B" both de-energized : Red LED at #2 cab end "on" (all white LEDs extinguished; railcar status "parked").

Position (2)
"A" de-energized with "B" energized : Red LED at #1 cab end "on" (all white LEDs extinguished; railcar status "parked").

Position (3)
"A" energized with "B" de-energized :  White LEDs at #1 cab end "on"with red LED at #2 cab end "on" (railcar ready to proceed "forwards" i.e. #1 cab leading).

Position (4)
"A" and "B" both energized : White LEDs at #2 cab end "on"with red LED at #1 cab end "on" (railcar ready to proceed in "reverse" i.e. #2 cab leading).

This setup gives 4 lighting combinations but these can be expanded upon by interposing additional switches (radio-controlled or manual) between the output leads for the white lights.

For the purposes of the GWR railcar (which has 3 white lights each end ..... one central above cab and one by each buffer) there are only two codes possible.
1) Stopping passenger : Just the one light above the cab illuminated
2) Express passenger : Just the two lights by the buffers illuminated.

Not wishing to add additional r/c controlled relays (running out of space to fit them!) I have fitted miniature single-pole changeover switches at each end, to select express or local code.

The different radio-controlled codes are selected by moving the transmitter stick either side of the neutral position : Toggling in one direction will switch output "A" on/off, while toggling in opposite direction will switch "B" on/off.

I dare say the above is "as clear as mud" but it does work!


: To clarify use of the 1N914 diode, the cathode (end with the thick coloured ring/band) is connected to the 5V POSITIVE side of the relay coil and the anode to the NEGATIVE (Ground) side.
« Last Edit: Dec 09 2015 07:53 by John Candy »
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Offline John Candy

Heart Transplant (x2) for GWR "Flying Banana"

If you have one of the early GRS GWR railcar kits which were supplied with Aristocraft bogies and have a problem, this may help you.
If you look at the previous photos, you will see I thought the electronics and bogies for this kit had been sorted!
Take nothing for granted with a GRS kit!

I had previously only tested the system for a few seconds running time (on several occasions at stages during construction) but had never had the motors running for any length of time.

Since the previous post, the kit has sat at the back of my bench, awaiting a burst of enthusiasm.
It wasn't so much a burst of enthusiasm, more a case of wanting the damn thing completed and out of the way, so it was dragged to the front and work commenced. First thing was to re-test the electrics.

Cell pack was fully charged at 24V (a 21.5V nominal pack) and the the wheels turned at a moderate speed (on full throttle) but that lasted only around 20 seconds and they quickly slowed and came to a stop.
Checked cell pack (Strikalite 2100mAh) and the reading was still 24V. Started motors again and same thing happened, ran for around 15 seconds then slowed to a halt. Third time, the motors sighed and nothing happened!

I disconnected the parallel configuration and connected the bogies individually to the cell pack (by passing the ESC in case that was at fault) but, again, they ran for a few seconds then stopped.

Tried a spare GRS motor gearbox with the cell pack and it ran at full speed without any problems.
Came to conclusion this must be a faulty motor issue.

The kit I have was an early example with Aristocraft bogies : Michael Adamson told me years ago that the first ten kits had these but the later batches were supplied with USA Trains bogies; he didn't offer an explanation, it may simply have been that Aristocraft bogies were no longer available.

I Googled for problems with Aristocraft motor bogies and it soon became apparent that there was a widespread issue with the motors in some bogies drawing 5+  Amps.

Reason for my problem was obvious.... two bogies drawing massive current from a 2100mAh cell pack.
Result is the electrical equivalent of a boiler running out of steam and having to stop for a "brew up"!
There was no way I could fit a cell pack to cope with currents of that magnitude (SLA cell would be far too big and heavy) so only solution would be new bogies or a motor transplant.

I have often been told that only a single powered bogie is necessary for the GRS railcar kits (they are supplied with two) so looked around for a solution which would avoid scrapping the motor blocks and scratchbuilding fresh bogies. The original motors are Mabuchi and marked  "RS-385PH CA 12 99 20 Hong Kong" and having long shafts at both ends. One end carries a worm which directly drives one axle, the other end carries a coupling to a drive shaft which connects to an enclosed gearbox on the second axle.
I was unable to find a direct replacement for these motors which would fit the into the bogies.

A few years ago I purchased (on Ebay) a pair of new Buehler 24 Volt motors which were said to be for garden railway use but were very cheap and came from Germany without spec sheet. It turned out they were in fact made in the USA ... metal case is stamped "Buehler, Kinston, N.C., USA" so was pleased to see they were a quality product and not Chinese! They went into the spares box for future use.
It so happens that they fit the Aristocraft block but have only a single end shaft but it is the same length as that on the end of the Mabuchi motors which carry the coupling to the gearbox. Plan was to use one motor in each bogie to drive the self-contained gearbox, leaving the worm-driven axle non-powered.

The transplants were not difficult, the only mod to the motors being a need to "sleeve" the shaft which is 2.0mm whereas old motors were 2.3mm. I had some 2.5mm external dia brass tube which was a perfect fit over the motor shaft, so I drilled out the brass gearbox shaft coupling to 2.5mm for half its length, then soldered the length of tube to the motor shaft with a couple of seconds blast from the  butane micro torch (using non-corrosive solder cream and small pliers as a heat sink to protect motor bearings/armature). Some small notches were cut in the bogie block casings to clear the terminals and wiring.

I haven't yet reached the stage where the bogies are mounted on the chassis for test running but powering the bogies on the bench with a 16.8V cell pack gave good results.
More reports as rebuild progresses but hope this fix may save from the scrap heap a few more of the Aristocraft GRS GWR railcar bogies .

In depth details of the problems encountered with the ESC and motors can be found at,2230.msg14305/topicseen.html#msg14305

(Photos of bogie motor swap below)


« Last Edit: Oct 10 2018 12:04 by John Candy »
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Offline John Candy

I have now managed to identify the Buehler motors used in this conversion which I bought from a German supplier in 2015.

They are Buehler (US made) type and are still available...see

On the rolling road, each bogie is drawing 250mA when directly supplied (i.e. not through ESC) from a 16.8V 2100mAh cell pack.

My fellow Members, ask not what your Society can do for you, ask what you can do for your Society.

Offline John Candy

Railcar update.

Now the cell pack and all the electronics have been refitted to the railcar, I decided to test the effectiveness of the two Buehler motors which drive the inner axle of each bogie. I had concerns that, not knowing the specs of the two motors, they may not have enough "grunt" to handle the, now quite heavy, railcar.

I chose the steepest section of my line (approx 1 in 40) and ran the car in both directions. From a standing start (on slightly wet rails) it accelerated to full speed up-grade in less than a yard . The motors held the car "in check" going down grade and stopped from full speed within a yard from cutting power. I estimate "full speed" to equate to around  a scale 60 mph with a 23.5V supply.
Very satisfactory outcome. I now have to fit the interior, the roof and add the minor cosmetic details before sending it into the paintshop.

My fellow Members, ask not what your Society can do for you, ask what you can do for your Society.

Offline hornbeam

Good work John. I think GRS switched to USA trains motor blocks as the Aristrocraft parts were hard to get by and a were not an easy company to deal with.

Offline Doddy

Good work John. I think GRS switched to USA trains motor blocks as the Aristrocraft parts were hard to get by and a were not an easy company to deal with.
Speaking to Micheal at GRS some years ago, it was down to the nylon gearing in the Aristo gearbox and axles that killed the deal. They kept stripping gears and the wheels kept slipping off the tapered axle ends and therefore going out of gauge (G1).

USA gearboxs and wheelsets were more resilient. The USA blocks also made it easier to mount third party bogie sideframes as well providing as a more reliable power pickup from the track.
The effort to build G3 axles into the bogie frames was made much easier and retained the reliability of the USA trains gearbox design.
"You don't know what you don't know"

Offline John Candy

This kit (after umpteen years on the shelf, part built) is now "almost there".

Just needs a clean-up and it will be ready for the paintshop.
A lot of modifications have been made, both mechanical and cosmetic.
The latest are shown in the following photos.

One modified item not shown, since it will not be fitted until the very last (to avoid damage) is the pair of gearbox oil-coolers which fit beneath the ends. The coarse/crude mesh supplied with the kit has been replaced with fine etched brass mesh (by Scalelink). This mesh will also be used for the recessed side panel vents.

My fellow Members, ask not what your Society can do for you, ask what you can do for your Society.

Offline John Candy

For the sake of completeness, here are photos of the underside showing arrangement of components and of the false floor covering the electronics in the luggage compartment.
While the head code marker lamps and red tail lamps are switched by radio control, the space allowed only four permutations of headcode and/or tail lights (white/red at either opposite ends or red only at either end). To overcome this, a small toggle switch is located behind the oil-coolers which switches between "local" (single roof light) and "express" (two lights by the buffers) headcodes.

My fellow Members, ask not what your Society can do for you, ask what you can do for your Society.

Offline Peaky 556

Your resin cast radiator grilles are interesting.  What sort of resolution can you get do you think in terms of slat pitch?
Rgds, Tim