Bachmann Mark II Coach Height Problems




Bachmann first introduced their range of Mark II coaches a few years ago. Since then, the range has been available in a number of liveries including BR Blue/Grey (B/G), BR(SR) green and BR maroon.
I model the early to mid 1980's BR B/G era, but held off purchasing the corresponding Mark II coaches because the livery had been incorrectly rendered. The main problem was that the width of the grey below the large windows was the same width as that above the windows when it should have been wider. The result was that the the models looked 'top heavy' and very peculiar.
In late 2012, Bachmann re-released the Mark II coaches and the Blue/Grey livery was corrected. I duly purchased a BSO, TSO and FO for evaluation.

This article reviews the new models.


Initial Observations

There was something odd about the appearance of the new models from the start: the models had a strange 'squat' appearance and the electrical boxes were hanging down far too much and almost running along the tops of the rails:




First Solution

I actually had two attempts at solving the problems with these models. The first was a bit of a 'goose-chase' as it didn't identify the actual problem properly.
Needless to say, the first attempt remounted the electical boxes so that they didn't hang so low:











Further Investigations

It wasn't until I placed the modified coaches on 'Ashprington Road' that it became obvious that there was still something wrong with them. There was something about them which made them look smaller or lower than other rolling stock.
When I buffered one of the Mark II's against a Mark 1 BG from the same manufacturer, the problem manifested itself instantly:








Upon measurement, the true magnitude of the problem became apparent: the mark II coaches are 1mm too low at one end and nearly 1.5mm too low at the other.
The coaches are clearly mounted far too low on their bogies because the roof tops and buffers do not align with the mark I.
I checked the prototype measurements for both Mark I and II coaches in the Harris and Parkin books and confirmed that both should be the same height.
Not only are the new release Mark II coaches incorrect in height, they are incorrect by different amounts at each end!
It became aparent that the ends where there was a toilet compartment were 1mm too low and where there was no toilet, they were nearly 1.5mm too low. There was evidently an issue relating to the window perspex and/or the mounting lugs internal to the bodies.
The bodies themselves were found to be correct size at each end.
Reviewing the undersides of the coaches confirmed that the chassis is not firmly held within the body and at the non-toilet end of each coach: the chassis was depressed further into the body. This is a really crude construction method!

The following packing was added to resolve the problem on the BSO luggage area end to bring its height up to the same level as its other end:


At the same time, the ends of the body of the BSO were found not to be square, meaning that the gangways do not fully meet and leave a gap:




The gangways appear to be fitted correctly. There is nothing the modeller can do to solve this problem because the body shell is not square. The TSO and FO appeared not to exhibit this problem.


Second Solution

Reference to prototype measurements confirmed that the models are simply mounted too low on their bogies. The solution was therefore to fit packing above the bogies which would need to be different in height at each end to compensate for the difference in height of the coaches at each end.
I chose to use a method of using packing strips, however, in retrospect, a large 'washer' at each end would have achieved the same result - indeed, I believe that if Bachmann were to make a large plastic washer which fixes to the bogies and overlays the coupling mechanism in the same way that the original bogie mounts do (ie extend the existing bogie mounts), this would solve the problem. The washers would need to be different thicknesses at each end. I have not had any problems with the coupling mechanism falling out using the solution I have implemented.







The packing on the toilet end on each coach is 1mm thick plastic card. The packing on non-toilet ends is 1mm thick plastic card plus .2mm thick plastic card.


Results

The first pictures show a Bachmann Mark I with a modified Bachmann Mark II on the right. The second and third pictures show a Hornby Mark IID with the a modified Bachmann Mark II on the right. All coaches in the pictures have had their chassis 'weathered'.






Conclusions

The Bachmann Mark II coaches are really nice models which are spoilt by incorrect mounting on their bogies and a lack of squareness on the ends of the BSO. Unfortunately, the squareness issue cannot be fixed with simple modelling, however, once the height is corrected using a simple packing approach and some weathering applied, the appearance is completely transformed into a superb looking model.


Graham Plowman (1/1/2012)



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