Page 19 - May June 2020
P. 19

 Locomotive Scratch Building
Eric Belshaw MMR Part 2
  Sir Vincent Raven’s first design for the North Eastern Railway 3-cylinder Atlantic, 4-4-4 Class V-2
I n the previous article I laid out the I started in the same place and right side crank pins on the driving
passions and talents that where necessary to scratch build for the Achievement Program, some of the
tools and one of my experiences that could have been a scratch build. In this part I will describe the key points in the building of my NER class D 4-4-4 tank.
When I submitted and had my other model judged, I gained confidence in
• working with Plasticard moulding and
forming as well as cutting out
• creating decals
• planning the build
• spraying the model to define the
finished colour and surface condition.
I started in the same place for all of my locomotive builds with some funda- mental research by checking out books and the internet to get the best images I could. I needed a side view to act as my drawing.That came from a book on North Eastern locomotives - ‘Locomotives of the North Eastern Railway’ by K Hoole.
The book provided the other critical dimensions:
• length over buffers
• height above rail level
• width overall.
With these dimensions in feet and inches it was easy to convert them to the milli- metre figures appropriate for the model. A chassis mock-up was made using the remains of an Airfix GWR Class 45XX tank engine, which had the right diame- ter wheels.
I mentioned in Part one the useful tools and machines to accurately make scratch built models.Well I didn’t have any of them then just the listed hand tool and a battery Dremel.
  for all of my locomotives with some fundamental research by checking out books and the internet to get the best images I could.
(Note: avoid doing any scratch building this way if you can.)
The wheel base of this donor engine was not correct and much fabrication was necessary to make it fit the dimensions. The motor mounting and the powered axle were the only remaining elements of the original chassis.After discussions with the AP chairman this chassis was discarded and a new chassis was fabricat- ed from brass to conform with the AP rules on scratch building.
Motorised brass chassis
A few words about the chassis.
I had the rough shape from the original cut up chassis. this defined the fore and aft ‘chassis to body’ interfaces.The mo- tor and drive gearing were different so those interfaces had to be designed into the new construction.
I had dismantled a few proprietary steam locomotives to get a clear picture in my mind for the chassis/wheel interface and I decided on slotted axle locations to maintain the drive wheel quartering. What is drive wheel quartering I hear you ask. It is the angle between the left
wheels of a steam locomotive to allow it to self-start. All the drive wheels on an engine must have exactly the same quar- tering otherwise the wheels will bind. The simplest locomotive where quarter- ing applies is a 4 coupled machine.The more drive wheels you have the greater the need for accurate quartering.
If you separate the wheels from the axle on a drive wheel set then you have lost the quartering.You should make an accurate jig to allow the quartering to be recreated but most people forget (I forgot).
The construction of the new chassis ensured the fabrication of new connect- ing rods as the original components had binding issues that limited free running.
I decided to solder my frame together after I had drilled and slotted the axle holes. I used the slotted holes to bolt the two halves together over spacers that allowed me to solder the front and rear plates and the motor mounting plate in one sitting.These spacers were made of wood and aluminium to avoid erroneous attachments.
(Don’t use plastic, it melts.)
I made and attached keep plates for the drive axles to the front and rear chassis plates.
When you come to manufacture side rods, I found it was easy to make one then make the second one from that. The thinness of the material minimises the errors of squareness when using hand held tools. Similarly, when making frame halves and piston rods, the holes in each component can be copied more easily.
  ROUNDHOUSE - May/June 2020

   17   18   19   20   21