NZR DREWRY ?TWIN-SET? RAILCAR.

[treetop]

There were 35 of these built, nos. RM100 ? RM134 and first went into service in New Zealand in 1955. The last of them endured until 1978.
I am in the process of scratch building a model of this railcar. It will be RM133.
At 1:24 scale (1 3/4? = 3?-6? gauge) it is 1.35m long.
The wheels/axles are ?off the shelf? at very close to scale size. The chassis is constructed from wood. I have used styrene plastic sheet for the body. 2mm thick for the sides which had windows cut out using a wood-router. The roof and lower sides (tumble home) are from 0.5mm. The vacuum formed ends are from 0.75mm. The two cow catchers, 6 step assemblies and the 21 air vents are also all vacuum formed.
The model is battery powered (10 x D size NICADS) with an RCS controller unit giving forward/reverse/speed control, start/stop of a diesel sound generator (pitch changing with speed) and triggering of a horn. This is a digital storage device loaded with an air horn noise down-loaded from the web. There are two speakers for this, one located behind each cow catcher. Only the appropriate forward facing one is enabled for each direction of travel. One end bogie is powered, via a ?Tamiya? gear train connected to a Decaperm motor above the floor.
I am now using 2.4G radio, having ?given away? 27Mhz and all of its interference problems.

This photo shows the model a while ago also with my Model T railcar, (another subject) and its turn table on my raised track. The other photos are in order of construction.

Styrene held in frame for heating in the oven.

Bogie detail. Note power pick-up wires now not there!

10 x Nicad batteries and Decaperm motor.

Cow catcher teeth fabricated from brass sheet and strip. Then glued into vacuum formed frame.

Vacuum formed vents. Easy way to make a lot of the same thing.

I still have the making of the ?below floor level? detail ahead of me.
I will be happy to try to answer any questions re the above.

 

[Madman]

Very impressive work. It is nice to see models being built of not so common trains.

 

[Tony]

Superb job one of the best scratch built projects ive seen. Do tell more about the vac forming

Tony

 

[ge_rik]

Superb job one of the best scratch built projects ive seen. Do tell more about the vac forming
Tony

Yes - Ditto and ditto. Absolutely brilliant!!

I'd also like to hear about how you went about constructing the Ford Railmotor. I think that's more in my league...........

Rik

 

[jameshilton]

Wow amazing modelling, this looks wonderful. I remember using vacuum forming at school, had never considered it for model making purposes.

 

[whatlep]

What a superb job. I've seen quite a few pictures of those units so I suspect those subtle end curves in all planes were a sore trial to get right - and how right they look on your model!
I am in real awe of those with the talent to achieve such splendid results. Thanks for sharing the photos.

P.S. Noting your location, how are things in your area, now that the media interest has faded in the UK?

 

[JonathanJ]

Very nice.

What did you make the cab plug for Vac forming out of?

J

 

[treetop]

Do tell more about the vac forming

Tony

Vacuum forming.
First I did read a small book on the subject and then gave it a try.
We have a Dyson vacuum cleaner which does have a good suck. This was connected to a wooden box with a hole in its top.

Rubber sealing strip was then placed around the edges. Any leaks will lose valuable vacuum.

The plugs are generally made from MDF, a composite board which we have here in NZ. It is very easy to work with. I have a sanding disk which I use a lot to form curves etc.
The top curves of the end plug were bread and buttered MDF. Other parts were styrene sheet with windows routed out. The light projections are wooden dowels suitably shaped. Parts of the plug are hollow, and I did notice some movement in places when the vacuum was applied. I would give more inside support another time.
The drilled holes are to help with air evacuation in corners etc. I did not use anything to aid separation from the plug, and early versions come off in two pieces. However I was finally able to get them apart in one piece with some careful prising/flexing.

The kitchen oven was set to 200 deg C (390 deg F). The styrene sheet MUST be held securely around ALL sides as it tries to distort terribly around the edges when heated.
I used both a metal frame (Meccano) and sheet wood (styrene stapled on and metal clamps) as supports.
When first put into the oven the styrene pulls tight like a drum, then with time it starts to sag in the middle. Sometime during this sagging period (maybe 1cm or 1/2 inch, experiment!) it is removed and with the vacuum cleaner already turned ON the support is lowered over the plug. This must be done carefully, yet swiftly (plastic starts cooling), to ensure proper positioning. I had a few miss alignments and disasters.

The actual forming process occurs incredibly fast and you very soon know whether you have a successful product.

Thickness of sheet is quite important. Too thin, I first tried 0.5mm for the ends, and the result was springy and useless. The plastic is obviously stretched/thinned to fit around the plug. Too thick, I tried 1mm, and detail/corners are lost. 0.75mm was my final choice. Some webbing, to varying degrees took place between raised portions. I did put some inside strengthening into the ends before their attachment to the rest of the model. I used 1mm for the cow catcher for added strength.

Plastic sheet stapled to underside of wood frame.

Metal clips to hold down sheet.

Make as many as you like/need.

So be prepared to experiment and give it a go!!

PS re earthquakes. We had another 5.3 shake recently. Fortunately, our side of the City has fared
very well compared to some other areas.

 

[JRinTawa]

I've heard this is a model worth seeing, looks rather good what I've seen in the Garden Whistle.
And gee you make that vacuum forming look easy, look forward to seeing the results maybe at the train show in October

 

[Tony]

Thanks for that im really surprised it works with a male plug (It must be hard to get a good seal) I was going to give it a try but was put off by having to make a female plug from the original before etc etc,,,,,,,,,,, in the end i ended up just making both ends from body filler (which gives added weight over driving axles)but i might give it a go for the coach ends then i can make as many as i want
Glad you posted its given me ideas for other rainy day projects
Tony

 

[hornbeam]

Thank you for taking the time to do all these posts. The vac forming tips are something I will think about and use.

 

[mike]

i am in awe off your tallents, love it..

 

[MR SPOCK]

Superb model that mate, and a handsome looking beast ,​

​

 

[simon@mgr]

How to make it look simple, in one easy lesson.
Brilliant, I always thought it was a lot harder.