2010. Scorpio Kit GWR 61XX Large Prairie Tank

Entry posted by ROSSPOP May 3, 2016

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The very first 7mm etched brass effort. Snapped up on Ebay complete with Slaters wheels.

Certainly for locomotives , I am a follower of the principles of sprung hornblocks as a means of maintaining good electrical contact with the track, smoother movement through pointwork and track joints between baseboards and more importantly for me at least, springing enhances the `weight and shear presence` of a loco on the track by drastically reducing the wobbles of a fixed chassis. I have been convinced in 4mm modelling and so this was to be an essential element in my 7mm constructions.

I have always been used to the Kean Maygib plastic hornblocks in 4mm, but could`nt get as much precision with regard to movement with the brass bearings in the 7mm version made by Slaters.

I eventually came across these roller bearing hornblocks by HobbyHolidays that enabled me to continue with using a MetalSmiths axle jig to accurately set up coupling rods to hornblocks. Such a simple way to quickly assemble a trouble free working chassis mechanism and ridding the loco building universe from timewasting trying to find that elusive `binding` nightmare of a wonky chassis.

The Scorpio kit was designed as a `beam compensated` chassis, but I`ve never been totally successfull at building one.

Obviously, consideration has to be given to cutting out the hornblock positions. I usually base this around where the kit has got its bearing holes positioned in order to maintain the correct axle height, particularly in rgard to connecting rods and GWR crossheads

The chassis frames provided are accurate and have plenty of rivet detail to be added.

Assembling the cylinder blocks and crossheads was hampered by the way the kit was organised. The crosshead castings are lost wax and poorly cast. They needed a lot of fettling and still looked wrong.

The cylinder wrappers need annealing to make forming to shape more maneagable. The vacuum pump is a solid whitemetal casting but I fabricated a replacement from brass tubing to make it a working pump even though it is tucked up under the loco valence.

You can see the wonky crosshead castings more clearly on this pic. I later disguised things by adding further detailing from the excellent parts from Peter Roles Components.

To keep costs down I opted for a Mashima 1833 motor and fold up gearbox. If set up properly it will produce good performance, particularly with DCC control. Clearance is tight between the crossheads and leading crankpin. I shortened the Slaters bearing and made the coupling rod bearing hole a little thinner.

The basic chassis completed and performing very well.

I invested in a MetalSmith rivetter as there are many pre-etched rivets to form in the superstructure.

No problems with assembling the footplate and valence.

Care to be taken in making sure chassis and footplate are square before soldering the captive nuts in place. The more decerning modeller will not be happy with the cylinder block profile as the angle of the block is too severe.

A fairly easy assembly of the superstructure, there was a poor fit between the saddle and smokebox that needed extra time and thought to solve.

The rear corners and rear top section are lost wax castings of average quality, but a good fit. I always find lost wax more difficult to fettle if not right.

The firebox is at least two millimetres too long and so the cab front plate sits too far into the cab. I did`nt know this at the time, but I had decided on `no heroics` and made the kit as it came.

The roof is designed to be removable to be able to detail the cab and is a fiddle to get to sit correctly.

Detailing parts are a mixture of lost wax and white metal and all need tidying, however, the kit is well provided for. The chimney is probably too small and the safety valve cover leans forward.

Overall, it eventually makes up into an attractive model if you persevere.

I use Phoenix/Precision two part etch primer to ensure that detailing is not buried under too thick a layer of primer. Precision paint was from a fifty mil tin I purchased in the 1970`s !!