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Sunday, 14 April 2013

How to make an 'n' gauge LOWMAC - Part 1

In Thornycroft J class Lorry - Part 4 I mentioned the options for sourcing LOWMACs for our fleet of lorries.

I was somewhat inspired by this article written by 'Mike' and decided to have a go at scratchbuilding myself. Mike identified problems replicating the end slope angles and well depth because of interference from the oversize n gauge wheel flanges The standard n gauge coupling assembly also gets in the way. I also overcame both issues but with variation on Mike's build method.

My model is based on the SECR Lowmac Diagram 1681 and there are several good photos of the prototype on Paul Bartlett's website.

Mike gave dimensions of the prototype he modelled (dia. 1686) and also the (compromised) dimensions of the model to accommodate the wheels etc. Interestingly my model is virtually the same size as his.

  • Well Deck: 25mm long (Mike 21mm)
  • Wheelbase: 40mm long (Mike 38mm)
  • Overall body length (without buffers): 55mm (Mike 54mm)
  • Width: 18mm
To get the slope correct and well deep enough I had to make the buffer beam 1 mm taller than it should be.

I considered the Peco 10' wagon chassis as donor wheel/springs/axlebox assemblies but was not convinced it would look like the prototype. All I really needed was the leaf spring and axle box assembly that I would mount on scratchbuilt side frames.

I scanned eBay for suitable donor products and came across an assortment of coach bogies. Now these had potential because there are no solebars. I might be able to build the side frames around the springs and axle box. Auction won and I can say my prognosis was correct. The ideal donor bogies are from the Graham Farish coaches (Mk1 or similar I think) . But we do need two of them because only one coupling per bogie and we need two for the LOWMAC..

It took me two attempts to develop a satisfactory build method and it turned out to be a surprising easy and relatively quick with very few parts and very little bogie butchery involved - just one cut.

Over the next few postings I'll explain the build method should you want to have a go.

First you need to obtain a pair of these - Try eBay:


David

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