Monday, 9 May 2016

Garratt Gives Up Its Secrets

A couple of weeks ago I posted that Himself has taken in a Backwoods NGG16 which a friend had bought second hand, and discovered didn't run very well, to see if he was able to improve matters and I thought you may be interested in reading about what he's found so far.

I'm posting this not to denigrate or humiliate the builder, whoever it was, but because one day it may be that that someone who is struggling to build one of these kits turns to Google for advice and might just benefit from what I've posted here.

It would appear that the person who put together these power bogies was struggling to fit all the valve gear into the available space and thought the solution was to slice the cylinder block assembly and the motion bracket in half so they could be positioned further out.

The effect, however, was the leave the brackets floating free whereas they should be joined together and attached firmly to the frame with a beam running along the top.

You may just be able to see the fault in the picture below.

At the front end they spliced the cylinder block back together with a piece of brass sheet...

But crucially they failed to solder it in place, so as the power unit ran the forces pushed the cylinder blocks upwards.

In the picture below the bogie on the left is as-constructed, the one on the right has been soldered into place.

The different attitude of the cylinders is quite obvious, you will agree.

Himself has found other errors with the assembly of the valve gear, although nothing that will stop it running, but a more serious flaw, and one that would not be fixed without deconstructing the entire bogie - which he is not about to do - is that the builder did not pay careful attention to setting the back-to-back measurements on the driving wheels when he assembled them.

Take a look at the the right hand leading axle and compare it to the other two....

Only when we get the locomotive reassembled and running again will we be able to assess whether this is a fault which will merely hinder silky-smooth operation or scupper any chance of this Garratt ever passing through a set of points.

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