Class 117 dmu
Entry posted by Barry Ten
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If there's a theme to some of my recent RMweb activities - the Blue Pullman, the Patriot, the FFA/FGA container wagons - it's that each was a project started at least ten years ago, and well before Bachmann announced their equivalent RTR model. Another case in point is this Class 117 DMU, which is another prototype that Bachmann have in their pipeline (although, like the container flats, it hasn't yet appeared, so I'm still slightly ahead of the game).
If you've been reading this blog for a while (and if so, thanks) you might well think I'd "done" this model some time ago. And you'd be right, in a sense, in that the 117 was finished, painted and decaled way back. In fact, here's a distinctly rubbish photo from 2010:
Er, so what's new, then? Fairly obviously I've added cream lining, which was done after deciding that the original plain green livery
was just too dull for my tastes, something which I believe also influenced the decision to add lining to the real things. The lining
(Modelmaster) really lifts the model, in my view, a simple change but a worthwhile one.
But I wouldn't have bothered lining the model if I hadn't got it running well, and that was a very protracted saga indeed.
The original model had some cosmetic work done, including Silver Fox resin sides and carved-off front lights to take it back
to as-built condition. I also flush-glazed it using Finecast glazing (not to everyone's taste, I know, but it definitely beats the
nuclear blastproof thickness of the original Lima sides) and until there's a better solution, it does the job for me. The Lima
wheels were replaced with a set of Ultrascales, new pickups were added, and off we went.
But the running was still crap. I've had really good Lima mechanisms - I've got one in a GWR railcar which is superb, and has
been so since it was bought - but the DMU was never very good at smooth stop/starts, not a very desirable quality in a model
that is meant to do a lot of stopping and starting! Since I'd had good results with the Black Beetle bogies in the Blue Pullman,
I decided to swap the Lima power bogie for a suitable black beetle. Let's just say the results were "mixed" - it was certainly
a smooth starter (and stopper) but try as I might, I could not get it to shift the 3-car unit reliably. This was (and is) a puzzler,
as two units will shift the 8-car BP with ease, with lots of adhesion left over. The BP will still drag itself around the layout even
if one of the cars has derailed. So why was one Black Beetle not up to the job with this 3-car DMU? To be honest, I'm still
not entirely sure, but I can only put it down to a tricky set of factors involving wheel diameter, coupling interface and the
thorny problem of weight distribution, which needs to be a bit cleverer in a vehicle with just one power bogie.
However, the other issue is that the Ultrascale wheels were de-railing at every opportunity, and although I've had fine
results with them under other models, there was something about the DMU (and my track) that they didn't like, again
possibly down to wheel diameter. So, in a spirit of pragmatism, I kept the Ultrascale axles (which are necessary to
fit the Lima bogies) and swapped all the wheels for Hornby 14mm units. Bingo, no more derailments. I also performed
a similar swap on the Black Beetle wheels, which was considerably trickier as the original wheels and axles didn't like
being separated. In fact I managed to destroy the BB axles but was able to substitute the Hornby ones, and eventually
get the BB axle gear mounted. The result, as hoped, was an immediate improvement in adhesion, with the 3-car unit
now moving without any tendency to spin its wheels.
Suitably encouraged, I then added a Class 108 DMU sound decoder, and found that the characteristics were fine for
the BB without any tweaking of CVs etc. The BB isn't as loud as the original Lima motor but it's still a little growly and
the sound decoder masks this very nicely, smothering the growl in proper diesel rumbles.
The model still needs the interior painting properly, windscreen wipers, passengers, and I also intend to add working
corridor connectors. As supplied, these DMUs were not gangwayed but they were gradually modified, and whereas I
don't know if it's appropriate to have speed whiskers and gangways on the same unit, mine will.
As for the base model, this DMU was bought as a two-car unit very shortly after the original release, so that would
make it - I think - around 1981 or thereabouts. Does anyone know? The white roof tops were done by me shortly
after getting it, along with the hand-painted headcode numbers, and the model was a firm favorite at the time. I
believe it was bought from the model shop at the Ffestiniog terminus in Porthmadog, where we were holidaying
at the time. It gives me a warm glow to have it back in service.
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