Lima Mk3 Improvements




The Lima Mark 3 coaches first made an appearance in the mid 1980's to supplement their (then) newly introduced HST power cars. At the time, the only alternatives were the Joeff version, which by the late 1980's, was no longer available, and the Hornby 'shorty' version which remained available up until Hornby replaced them with proper scale-length models in the early 2000's.
I always felt that the sloping 'angle' of the front end of the Hornby HST power cars looked 'wrong', so consequently, never purchased the model. I believe this inaccuracy occurred because the models were produced before the prototype was actually built and introduced.

When the Lima HST became available, I commenced buying intermediate coaches, one at a time - that's all a teenager could afford! There was no doubt that the Lima Mk3 coaches were far superior to anything else at the time. And for that reason, I continued running them on successive layouts, including my current 'Ashprington Road' layout.

Ashprington Road created a little bit of a problem because I upgraded the 'standards' I was using and laid it with Peco Code 75 track which is somewhat finer in tolerances than Code 100 which I had used up till that point. The issue was that the Lima Mk3 coaches were fitted with wheels which dated from the 'pizza cutter flange' era, a topic I covered in my article Lima Wheels. 'Pizza Cutter flanges' are so large that they cause models to bump along the rail chairs of Code 75 track.
Back in the early 2000's, I purchased a batch of Gibsons wheels to replace the Lima wheels so that the coaches could run on Ashprington Road. Lima's standard axle length was 24.5mm as opposed to the standard UK/Romford 26mm axle which meant that the Gibson wheels were fitted to 'Lima length' axles. And for many years, this was how my HST set ran.

One aspect I was never happy about was that the MK3 coaches always appeared to 'lean' sideways, one way or the other. The effect of this was that if one looked along the roof of the train, the coaches did not line up and appeared to be leaning side-to-side quite unprototypically. The following images show the problem, but please note that the coaches are slightly pushed over to exegerate the problem beyond their 'natural' out of line:


Some might say 'why bother trying to fix this, go and buy some Hornby Mk3 coaches ?'. If I was starting from scratch, buying intermediate coaches, I would do exactly that, but I have 7 of these things and replacing 7 coaches is not a cheap solution, especially when the Lima models are actually quite good once a few issues are sorted out. Secondly, locating Hornby Mark 3 coaches in 1980's blue and grey is like finding hen's teeth!
So in this article, I undertake a few improvements and fix the leaning coach issue.


Dealing with the Wheels and Axles

The reason for the coaches leaning was because the Gibson 'Lima length' axles are actually too short. This results in side-play in the bearings and due to their connical nature, side-play causes the pin-points to effectively drop out of position, cause the coaches to lean.
The wheels would have to be replaced.

Over the last 15 years, I have revamped several Lima models, particularly class 117 DMUs and a few wagons. On those models, I used my Dremel to grind down Romford axles to fit. During that process, I found that no two Lima bogies are the same and they every axle I ground down was actually a different length. They were effectively purposely cut to fit. In other words, I had found that the manufacturing quality of Lima bogies was so varied, that even their own 24.5mm axle was never a snug fit.
Faced with this issue, I decided that there was no way fitting any 'Lima length' axles was going to work. One option was to buy a batch of Hornby BT10 Mark 3 coach bogies but it became quickly apparent that these could not be obtained and even if they were, they are not a direct fit and every one would have to be modified. This left me with the other option which was to do something about the variations in the Lima bogies and somehow make them good. It just so happened that at the time I was working out how to solve the problem that the regular news email from DCC Concepts arrived in my inbox, advertising a bearing reamer:


A reamer would enable me to open out the axle boxes on every bogie to accept 26mm axles. The variability in manufacturing would be resolved in that some bogies might require more reaming out than others but at the end, they would all consistently take 26mm axles.
A DCC Concepts bearing reamer was duly purchased.
While this was on order, I also ordered replacement wheelsets from Gibsons. These days, they make 12mm wheels with disc pads already moulded in place, so for BT10 bogies, this is perfect.

When the reamer arrived, I decided to try it on an old Lima Mk1 coach bogie in the spares box to a) test how easy the tool was to use b) test my ability to use it and c) test the reliability of fitting some Romford wheels in a reamed out bogie before I tried it on the 'production line' models.
It turns out that Lima BT10 bogies and the MK1 bogies in my spares box are not wide enough to take 26mm axles. Reaming out would result in the axle pin-points busting out through the external axlebox covers. The reamer had virtually no effect (it isn't very sharp) on the awful 1970's nylon-type plastic that Lima made their bogies with. I should have checked this first, but now a rethink is required because using 26mm axles on modified Lima bogies is not a viable option.

This leaves me with the choice of trying to fill the pin point bearings of getting 'Lima axles' which fit. What I discovered was:

  • Gibsons axles have a lot of side play but they are exactly the same a Lima axles in length
  • Lima axles also have a lot of side-play
  • Lima fitted axles to their own models which were too short and Gibsons appear to have just copied them rather than making sure they actually fit

All of this is consistent with previous experience of re-wheeling Lima class 117 DMU trailer coaches: on those, I ground down 26mm axles to fit such that they were 'custom' sized. They were somewhere between 24.5mm and 26mm long.

I think what needs to happen is that someone needs to get hold of some Lima models and actually measure them for fit rather than just copying what Lima said they fitted because what they said they fitted and how they manufactured the models were not the same thing!

Clearly, flogging the 'Lima length axles' donkey is not a way forward. Better to look at ways of replacing non-standard axle lengths altogether.
I have therefore made contact with Simon Kohler to purchase Hornby BT10 bogies so that I can discard the Lima bogies completely. Simon advises that Hornby are currently waiting for delivery of these as spares.

The Gibson wheels have arrived and really look the part. Being 26mm axles, these will be fitted to the Hornby bogies.
Hornby bogies will require modification to fit the Lima coaches, but this is nothing that can't be done in the 'Ashprington Road' workshops!

More to follow.


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Graham Plowman (Created 2/10/2021, Modified 19/10/2021 9:48:45 AM +11:00)



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