DMU's/EMU's on first radius curves

[M. Matthews]

Hi all!

I am current constructing a layout of a terminus station and want to keep the era as modern as possible. The layout has a hidden reverse loop which has first radius curves as well as reverse curves.

Can anybody recommended and DMU's/EMU's that might be able to cope with this? Or even any other modern stock.

I'm not bothered about realism or overhang as the stock can't be seen in these areas, more just that the stock won't derail.

Thanks!

[morairamike]

Hi welcome to the forum.

The problems that arise with trains on rad 1 curves are various. You say that you want to run DMU and or EMUs. On my layout I have both, Hornby 2-BIL, Bachmann 2-EPB, MLV and a Dapol class 121. The first three run perfectly on my rad 2 and 3 layout but the 121 derailed on every curve and points. Investigation showed that the bogie at one end was fouling the body which restricted its rotation at the max that was allowed. I noted that the bogie in question had two small moulding flashings overhangs on the inner end that weren't on the other bogie. So I removed them success no more derailments.

Then I thought maybe with a big of fettling these rail cars could negotiate a rad 1. But there is a limit. This is type of propulsion system used.

My EMUs all have one powered bogie so the motor is mounted on to the bogie, so it's possible the rotation could be increased by careful removal of the floor opening corners. But the 121 has a motor mounted in the centre of the carriage that drives both bogies via drive shafts and the limit is the drive shaft to bogie universal joint max angle.

With steam locos you are limited by the ability of the drive wheels to negotiate the curve without jamming the centre wheels against the inside edges. Flangless centre wheels were capable of rad 1 curve negotiation when built locos were built like that but now it's usually only 0-4-0 that can do it.

Others will give different answers. The above are my thoughts and findings.

[M. Matthews]

Thanks for your reply. I understand the difficulty with steam loco's due to the fixed driving wheels but this is not the era I intend on anyway.

Possible models I've been looking at are;

Class 395 (the more detailed one)

Class 466

Class 158/159

4vep

Class 205

Class 170

Do you think your 2-BIL & 2-EPB would make first radius?

Anything else along those lines. I kind of hoped that with their wheel formations, they might just be able to make it round the first radius. I wish I could change to second radius but with the space I have, first radius is already on the edge.

[LCDR]

Modern bogie stock is unlikely to negotiate first radius curves without the risk of derailing or buffer- locking.

The early Triang / Hornby R157/R158 Met Cam DMMU was designed to operate round first radius and I think the 1982 Class 110 RR698 would be OK too.

[Rana Temporia]

As LCDR.mentions the Tri-ang DMU (later made by Hornby) has no problem with 1st radius curves but is shorter than scale length and the prototype of this particular Metro-Cammell DMU only worked in East Anglia and the Manchester areas with a non-standard coupling code and a cowl round the buffer beam unlike the production series versions that had a standard coupling code and lasted into he 2000s. Tri-ang also did a short version of an EMU which I think was a mix of prototypes but is fairly rare as it wasn’t made over a long period of time. If you do get one of these, get the later version with later couplings and wheels, from experience they run much better!

The Hornby 110 DMU has been mentioned. there was often a problem with the motor bogie being too stiff in the chassis, solved by some delicate and very careful filing of the chassis in my case. This should negotiate 1st radius curves. The Hornby Pacer should also manage 1st, radius, mine certainly do.

I’m not sure about the Lima class 101 Met Camm DMU. This was also made by Hornby when they bought the tools. Scale length coaches and most Lima diesels would go round 1st radius with no problems. The Lima class 117 DMU certainly does but is a bit basic compared to todays offerings. Also not sure about the Lima and Dapol Sprinters. Maybe someone else can advise on these?

[STG]

Class 395 (the more detailed one)

Class 466

Class 158/159

4vep

Class 205

Class 170

I've run the 159, 170 and 395 on 2nd radius.

The 395 looked the most realistic - the 158 and 170s have longer carriage lengths so can overhang a lot more.

From my experience, the 170s and 158s do sound slightly pushed when going over just 2nd radius (although that's probably because I've put correct b-to-b on the wheels rather than the factory default).

One issue with the 395s is a lack of traction - they rely on one motor bogie, whereas on the 170s and 158s have all-wheel drive on the motor coach (not sure what the new 158s are like). Many have added weights to the 395s and removed traction tyres for much better results.

I'm pretty sure modern multiple units in general don't have buffers between the coaches, so it will be not buffer locking, but mainly the couplings that might be a hindrance (I had a few issues with the default 158 coupling on the older models, so swapped it out easily)