Bachmann DMU, Cravens / class 105

[Metadyneman]

One thing I have noticed over time with Bachmann DMUs is the method of power transfer from bogie to motor can become a bit "iffy". It's all done by contact from the bogie rubbing on a Springy "leaf" of copper protruding slightly downward from the PCB on the chassis which can become dirty and misaligned over time. This can (and has with mine) cause intermittent and jerky running, especially over uneven track. I took the decision a while back to solder the contacts from the bogies with a small length of wire, direct to the anchor rivet for the springy "leaf" thus making a permanent contact without reliance on pressure to keep the electrical continuity going. Worth doing if you start to experience problems.

[Bigmet]

I am still going on these, having managed to acquire two more pairs of these units at less than original retail price. (I really don't see Bachmann selling many at the proposed £150+ RRP, 'enhanced' with a few figures inside, with s/h fairly plentiful.) Decoder fitted them over the weekend and got a surprise, three out of four of the cab front windows detached as the bodies were removed or - grrr! - replaced. Is it the heat? None of the other glazing has detached. Then checked the other three pairs I have, currently running as the 'big formation' of six cars, and whaddya know two of the front windscreens inside the set had fallen in unnoticed. The quantity of adhesive used do appear a little minimal...

But hey, these models far exceed anything I could build and finish and the problem was easy to fix; and they run beautifully, and they recall those happy days when one could have a driver's eye view running up to Town, either to KX or down the drain to Moorgate. (While one's fillings were rattled loose...)

Interesting about the pick up connection, will be kept in mind. This will apply equally to the classes 101, 108 and Derby lightweight (and possibly some of the EMU's) as they share mechanism arrangements. No troubles so far on mine, but I do have each pair through wired for single decoder operation so all 16 wheels are picking up and there are multiple power transfer points over each pair, which should be enough...

[sishades]

Last year I too soldered the contacts directly to the leafy thing. I also took the liberty of permanently attaching the motor car and the immediate coach with micro plugs thus doubling the number of pickups to the motor. Works a treat although I am looking at conducting couplings to replace the plugs.

[Peterm]

Good idea too. You can't beat soldering where possible.

[Bigglesof266]

The quantity of adhesive used do appear a little minimal...

But hey, these models far exceed anything I could build and finish and the problem was easy to fix; and they run beautifully, and they recall those happy days when one could have a driver's eye view running up to Town, either to KX or down the drain to Moorgate. (While one's fillings were rattled loose...)

Concur with your approbation. Wonderful looking models & superb runners. I have several. Never had the pleasure of the real thing other than vide proxy with the DMU era sibling of BTF's "Diesel Train Ride" or accompanying Sir "John Betjeman Goes By Train".

The glue thing is possibly not a bad thing insofar as clear windows are concerned. I think the OM uses rubbish quality superglue in assembly, so I'd rather have to reglue them than receive them with CA affected or fingerprinted windows because of enthusiastically liberal application of superglue. The skylight windows in my (Hornby) lined crimson Gresleys all fell out as they aged. But I'd rather that than the detail disfiguring blobs of superglue on namplates etc included 'free of charge' with several Hornby locos I've bought over the years. e.g. current high detail streamlined Coronation.

[Bigmet]

Good idea too. You can't beat soldering where possible.

Very much so. Since they are out operating at the moment, and with my curiousity piqued by this thread, yesterday evening I had the motor bodies off the oldest of my 105 twins and one of the just acquired twins, put the sets on a dead length of track and measured impedance rail to decoder socket both sides. Negligible in all cases. So I guess I'll wait for trouble before making changes.

Happily no more windscreen fall in incidents popping the bodies off and back on. That relates to my one major gripe with this model's design. Surely Bachmann realise that it would be much easier for owners if an underside removeable panel access to a better decoder socket location was provided, and there's no shortage of acreage between the bogies to provide such a thing. When near everything else about a model is superior, minor deficiencies begin to figure in perceptions - Bachmann's other regretable omission from these models is the close coupling mechanism. But let's be thankful that this mechanically dreadful prototype actually got such a fine model...

[D605Eagle]

You saying about refitting the windows reminded me that I welded a whole new skin on the front end of the two car set at the ELR. The amount of corrosion was scary. It sounds amazing inside the guards section as the exhaust as been rerouted back to its original route through a square tube in there!

[Bufferstop]

the exhaust as been rerouted back to its original route through a square tube in there!

but hopefully without the asbestos lagging which they originally had. The old bubble car that rattled between Leamington and Stratford had had it's pipes rerouted, up either side of the cab window, but the box remained sealed up with hazard warning tape until the unit was withdrawn. AFAIK it still contained an abandoned section of exhaust pipe.

[D605Eagle]

The interior was totally gutted when it was azzie stripped, including that part. A new exhaust box section had to be fabricated when it was restored. I have no idea what material is used to insulate such things now. Glass fibre material?

[Bigmet]

Just acquired the last one of these I needed for representing the end of steam on the KX inner suburban service. Bonus! The last one was the cheapest yet! Who says this is an expensive hobby?

Now I have them all, the planned programme to modify them all to screwlink couplings can go into operation, along with finishing the soldering, through wiring, and decoder installations on the two most recent acquisitions.

[Bigmet]

'The plan' for screwlink coupling came to an abrupt halt last night, because of the obstacle to locating them correctly when mounting them with the necessary spring action. The sprung shank within the vehicle would foul the extremely neat internal wiring. I simply hadn't looked inside in detail up to this point to fully appreciate how significant this obstacle would be.

Think it will have to be Kadees, standard with the rest of the coaching stock, unless sudden inspiration strikes for an alternative method. The set ends can still have cosmetic screwlinks of course, for best appearance. That will also make it easier to tease a friend, by putting an unpowered car either side of an N7 (which has Kadees as it is a passenger loco) to make a fictional push-pull set. Flights of imagination are not his thing at all.

[Bigmet]

Further 'discovery' on these models! I only have one motor unit in each multiple, as the drive will easily drag 12 mk 1 coaches around! (In KX suburban service they usually operated in pairs - four cars - and sometimes as a trio - six cars - and just one motor unit is perfectly adequate.) The plan was to take the motors out of three sets, so that I can have three of the four car formations available, each with one motor unit.

But before completing on that I started restoring my very cheaply obtained 'breaker' - which I think the previous owner crashed from height off a layout! - but was all out of spare unpowered bogies to make it into another unpowered set. However, desperation leading to innovation, I tried running it with the 'motor block' and worm completely removed. Well, that was good, and sufficiently free running to be usable. It only required a slight outward bending of the 'contact tabs' on what had been the powered bogie for it to be positively retained on the vehicle too.

Now that's a lot simpler than what I had prototyped and completed on two, complete substitution of the motor chassis with an unpowered chassis. So the modified and 'to be modified' are all back in the workshop now, original powered chassis being restored to the bodies they were removed from, once the block, motor and worm were removed. Much simpler, why didn't I try this earlier? Means I can have 3 four car sets running and any one can become a six car set as and when required, from three powered sets and four unpowered. Woo hoo! Or perhaps beep-barp as they are diesel?

[Bigmet]

What with being a fast worker (ho ho ho) I have just got around to completing the motor block removal programme for the unpowering and through wiring of the required sets for the scheduled services. I had a 'flash of insight' while this was underway, and realised that I only needed six sets rather than seven, if only I restricted the 'unpowering' to two four car sets each with just one motor and thus one decoder.

So I am all done, 2 permanent four car sets, and 2 two car sets, running on just four decoders, instead of the 12 decoders that 'all unmodified' would require, and a saving of two feet of siding space by only having six sets to be standing out of use during the 'steam only'period in my 'sweep through time' operating scheme.

(That space requirement I see as a real problem with MU's for modellers. A train of loco hauled stock can do for many service workings by changing the loco, or maybe adding or subtracting a vehicle or two - which will be used in yet other loco hauled trains. MU's are relatively inflexible in this respect.)

[SRman]

What with being a fast worker (ho ho ho) I have just got around to completing the motor block removal programme for the unpowering and through wiring of the required sets for the scheduled services. I had a 'flash of insight' while this was underway, and realised that I only needed six sets rather than seven, if only I restricted the 'unpowering' to two four car sets each with just one motor and thus one decoder.

So I am all done, 2 permanent four car sets, and 2 two car sets, running on just four decoders, instead of the 12 decoders that 'all unmodified' would require, and a saving of two feet of siding space by only having six sets to be standing out of use during the 'steam only'period in my 'sweep through time' operating scheme.

(That space requirement I see as a real problem with MU's for modellers. A train of loco hauled stock can do for many service workings by changing the loco, or maybe adding or subtracting a vehicle or two - which will be used in yet other loco hauled trains. MU's are relatively inflexible in this respect.)

DMUs do have some flexibility in formations, with many mixed class sets running over the decades, particularly later in their lives. In particular, the blue square units had quite a good variety of manufacturers and styles, although doing this in model form may not be quite so easy, particularly now that units like Bachmann's class 117 appear to be restricted to coupling within the same units only. I used to run mixed formations of Hornby and Lima units, in the days before DCC and more modern mechanisms. One of the most bizarre formations I have seen in a book on DMUs was a trans-Pennine class 124 (possibly with matching class 123 vehicles mixed in) in blue and grey, with the leading DMS being a blue class 104 vehicle.

[Bigmet]

That's good fun if the option is there, but my layout scenario terminates in 1962, so no mixing of DMU's; the KX suburban service DMU stock was Cravens (105), and nothing else to speak of. The only deviation has been putting a couple of the unpowered trailers one each side of an N7 to make a push-pull set, which of course is a complete fiction, even if it did look very funky.