Class 121 DMU Query

[shed16]

I'm planning my first layout around a branch line set in Era 8 as that's the era both me and my partner grew up in.

I'm considering what locos I'll run (I know squat about trains!), this may be more of a general question than something specific to the 121, but when researching I can see photos of Class 121s running either individually or in 2-4 car arrangements but I can only find models as single cars online.

Something like the Bachman with all the bells and whistles, comes as a single car DMU at ~£250, but if I want to run 4 then that's pretty mental to me. Is it typical to run something like this with one powered loco and then the additional units being dummys with just lights or something?
I can see the Class 117 is similar but comes as a 3 car DMU which works out considerably less.

Am I missing something here or is this "just how it is"?

[RAF96]

I have a Class 108 DMU pair, only one of which is motorised, but both of which have old ESU sound decoders installed on the same address, albeit both are loaded with a rather basic VW microbus profile, until Hornby releases an HM7K DMU profile for me to load and replace the old decoders.

[Mountain Goat]

Class 121's are all single car railcars. Other classes of DMU were run in 2, 3 and 4 car sets. (The few run in 4 car sets were later run as 3 and then as 2 car sets as they aged and their engines would regularly drop out. (Example from a guard who used to work them in the 1980's said they had such little maintenance and were so worn out (The 1980's railway strikes had not a lot to do with pay as the news claimed it was about. It was the unsafe conditions where it was common to see DMU doors tied shut with baling twine with "Door out of use" stickers in daily life in the more rural services of the country such as in West Wales) that if he worked a DMU service off Swansea heading to Pembroke Dock and back as a 2 car set to reduce the units stress on the four engines, it would lose power to one engine by the time it reached the halfway point (Carmarthen), lose another engine at the Dock, and often lose a third engine on the way back around Carmarthen again so they would limp back to Swansea trying to climb up Cockett Bank on the one engine left. These were 4 car sets originally when new and used in other areas. West Wales depots became the well known "Dumping ground" to older stock which other depots had rejected, which is why in the early to mid 1980's, so many railway enthusiasts headed this way! We still had trains of 50+ lose coupled very rusty unfitted coal wagons going past right into the late '80's with the guards van at the rear. All recorded in excellent books like "Western Region in Wales" which captured the atmosphere that had by then already gone a decade or two ago in other areas. (A few of our colliers were still running steam engines in those days as they ran from the coal that they were mining, and their cylinders provided useful torque for shunting heavy trains than an equivalent sized diesel, not to say a diesel did not have its own advantages... But if its fuel was freely available in the area they were being used, it made perfect sense!) Go back just a decade before that to the early 1970's and one mine in Wales was still using a horse for its narrow gauge surface working to tip the spoil).
There were several classes of DMU used on the railway network, but all class 121's and 122's were single cars with a cab at both ends which made them better suited for country branch line use. It would have been wasteful to run them as a 4 car set, but B.R. did do some illogical things!
When the then new Pacers and Sprinters came on the scene to replace the DMU's (Known as "First generation" but were actually the second or third generation of the DMU concept, and the Pacers and Sprinters were known as the "Second generation"), while a 2 car Pacer was an excellent unit for lower density branch line use though a few lines due to extremely sharp curves they could not be used on, an alternative short form of railcar was needed for those areas where the Pacers could not go. British Railways, had already had a fleet of then problematic 155's with some unusual faults such as one or two becoming stranded after someone flushed the chain which made it into the press at the time needing to be solved, so someone had the idea that these could be rebuilt into single car units, and the class 153 was born, which then proved to be very reliable units, though their only real downside apart from their rather compact "Small cab end", that if an engine did overheat or went low on oil so they would automatically cut out, one was stranded. (Those simple engine cut out devices if the temperature go too high or the oil level became too low actually saved many an engines life! I actually wondered why cars didn't have the same as a ceased solid engine would have been prevented, as one can drift to the nearest safe place if the engine cuts out. We did this once on a hill drifting down to a convenient station that I don't think we were sceduled to stop at. The driver checked to find the engine low on water, so we opened up the cabinet below the cab to get the plastic jug (Standard issue and useful!) while I had opened the train doors to let passengers have a bit of fresh air. The driver nipped out to knock on the door of a nearby house (Think it was once a station house?) to ask for some water, and one lady who had got off the train and was dressed in a very expensive looking coat and around her late 50's naturally asked what was going on. I said the train is low on water so the driver is going to get some. "Trains that run on water? In this day and age?" she said! I went to explain that it was for the radiator, and she didn't seem to understand. (She had come from an English city (Think London) so had lived a somewhat sheltered life). I then went to try to explain why the engine needed a radiator and she said "I supposed you are going to tell me that cars have radiators too". I said "Of course they do! If it has a petrol or a diesel engine it has a radiator!" She still wouldn't believe me! She said "My husband's car hasn't got a radiator... I said "Have you ever opened to look at the engine?"
"Oh the garage does that, not my husband"... (Where do these people come from that have lived such sheltered lives? People are amusing! ).
That is one aspect I missed about the railways. Meeting people from different ways of life. Found it surprizing how sheltered some peoples lives were.
At another time a young lady who was either in her late teens or early 20's asked me how do the trains stay on the track as the rails are so narrow? I said "Ah. Drivers have to concentrate to keep them on. Is why they are paid so much!"
On another small branch line terminus station, some teenage ladies got on the train very early, and the driver and I needed to visit the shop to get ourselves something to eat, so we needed to ask them to sit on the benches outside for a little while until we came back. At first they refused to leave so I pointed to the ceiling of the 158 which has metal panels and said the panels opened when the ejector seats operated if someone was left on the train wen we were not there. They actually ran off thet train! We did have them ask on later!

[shed16]

That was a nice read, thanks for the insight. I'll go with a DMU which operated in 3 or 4 car sets i guess. I'm sure I did see some 121s in photos running together but like you say maybe it was BR doing odd things.

[Mountain Goat]

It is likely that they could be run as four class 121's as part of a service where further down the line on that service they would be separated to go off on different services. Many examples. E.G on the Cambrian coast line, two class 158's run as a 4 car as far as Machynllech to be separated, with one 158 heading to Aberystwyth and the other going to Pwllheli.
When I worked on the railways, on certain services we often did this. So it is more than possible for the 4 car set to be split into 4 separate services further down the line.