DCC Fitting Series: Bachmann Class 25

Last time in the DCC Fitting series I looked at the Bachmann Class 03, and although it was a breeze to fit the chip, the performance left much to be desired. Let’s have a look at what’s next in line:

Class 25 by Bachmann

Bachmann really know how to make a good motor mechanism and on analogue, like the 03, this was one of my top 5 runners. More on that later, let’s start with the fitting process:


Bachmann Class 25 in BR Two Tone Green

How Easy Is It To Fit?

I’m happy to report that like the 03, this too is a doddle to get into… Simply remove the 4 screws shown…


Remove the 4 screws with a micro Phillips screwdriver

Hold the under-frame steady, and the body should come right off.


Body Removed

Bromsgrove Models talk of an 8-pin socket and also adding some insulator tape between the PCB board and the chassis. My edition however seems to be a later version and accepts a 4 function 21-pin decoder, and needed no further modifications. If you’ve got the 8-pin model, follow the link above for some additional advice.


“REV A” should be facing upwards, with the bulk of the components and pins also on the upper side.

The manual that comes with the loco (and the one that comes with the chip) should also help you figure out which way to insert the chip. It’s also made obvious by the PCB board having a helpful chip shaped rectangle printed on it as a clue.

It’s worth pointing out at this stage that it’s always best to test and address your freshly chipped loco before you put it back together (if possible). In the case of some models, like the 25, you might not be able to test the lights at this stage as the accompanying circuitry detaches with the body.


These contacts connect when the body is screwed back together. Be sure not to bend them in the fitting process.

Carefully place the shell back on the under-frame and replace screws. It’s that simple.

Fitting Score: 10/10 I feel there’s not much that could be done to make this easier, it’s a well designed setup that also doesn’t compromise an excellently detailed model in any way.

How Does It Run?

Once again I’ve opted for a Bachmann EZ Command chip (The 21-pin variant has reference no. 36-557), again on the basis it’s a Bachmann chip it should work perfectly with a Bachmann loco. It’s also the default brand I get given when I ask my local model shop for a 21-pin chip without specifying a make.

This time round I’m not disappointed. The loco, already fairly silky smooth on DC, glides effortlessly over the rails without so much as a whisper. The slow speed performance, which lets face it – is one of the best parts of DCC operation, is incredibly impressive.

The lights shines nice and brightly, yet not too much to burn-out the legibility of the headcode.

Is there anything negative to say? Well not really. I mean if I was being super picky, it would be good if there was a cab light, or if you could turn off the tail lights individually but this is more down to the design of the model rather than the installation of the chip.

DCC Chip/Running Score: 10/10 Even though some Forums shy away from the cheaper Bachmann chip, the combo seems to work perfectly. Job done!


Lights On!

Overall Score: 10/10 This was actually the first loco I chipped. So why didn’t I start the series with this post I hear you cry? I didn’t want to come straight out the starting blocks without a bad word to say for the DCC fitting process, especially as I know that the results have differed wildly. If I’d started by saying everything was hunky-dory then perhaps you wouldn’t have come back! The Class 03 was a good starting point as it instantly highlighted both the good (easy fitting) and the bad (cheap chip giving average performance) of DCC conversion. The Class 25 sets the bar high for DCC conversion. So was it all down hill from there?

Other Locos in the DCC Fitting Series

  • Class 03
  • Class 17 (coming soon)
  • Class 47 (coming soon)
  • Class 128 (coming soon)

– Andy Carter

Model Railway Track: Code 75 or 100?

So you’ve picked a scale to model in. It would be reasonable to think that the most important part of railway modelling – i.e. the track and the stock – would be an accurate scaled down version of the real thing. Well you’d be wrong.

Image from modelrailforum.com

OO Gauge suffers from a historical anomaly that means it’s rolling stock is actually too big for the track in runs on. In the early 20th century British model manufacturers had decided to compete with their American counterparts who had just launched O gauge. (Half of O Gauge, 3.5mm to the foot scale or 1:87). However to keep costs down they were still manufacturing models with wind up mechanisms. This method of propulsion was proving hard to fit into 1:87 scale models. The solution was to enlarge the models to 1:76 scale (or 4mm to the foot). Instead of enlarging the track with it – a costly exercise, the British manufacturers simply continued to import the American HO track and built the models’ axle width to cope accordingly. At the time, when manufacturing techniques were cruder than they are today, this inaccuracy was not so noticeable. Unfortunately the mismatch in scale sizes stuck, and is still in use by all the major companies (Hornby, Bachmann, Dapol, Heljan etc) today. The inaccuracy may still be hard to spot with the majority of models, but put a British OO Gauge model next to an American or European HO counterpart on the same track and the difference will certainly be noticeable.

So what can be done?

Some modellers do what the British manufacturers never did and properly enlarge the HO track to it’s true 1:76 scale. This is known as EM Gauge (and an even more accurate scale is P4), although you might often hear it referred to as ‘Fine Scale.’ This is a rather drastic step and almost exclusively requires scratch built track to be constructed by the modeller in question. It also requires all the wheel bases and axle widths to be altered on the models themselves to cope with the enlarged track. The results are certainly remarkable, but this is usually beyond the Novice modeller such as myself.

Track Codes: What’s the difference?

An alternative is to look at improving the rail dimensions without altering the actual gauge. You may have heard people talking about Track Codes – these are alternative varieties of off-the-shelf HO/OO Track with different rail heights. The gauge is exactly the same, but the rail height varies in an attempt to be more accurate. The track you get in any Hornby, Bachmann or Peco starter set is almost definitely Code 100 (sometimes referred to as ‘Set Track’). The ‘100’ simply means that the rail is 0.1 inches high. If this were to be scaled up along side OO Gauge rolling stock, the rail height would be almost 30% higher than it’s real life equivalent. Code 75 track (with a rail height of 0.075 inches) is far more accurate. If you scaled this up it would this time be 3% lower than it’s real life equivalent. It’s still not perfect, but it’s much closer to the mark than Set Track.

Codes 100 and 75 are the most common but there are of course other varieties: Code 83 is used to improve the accuracy of North-American-Image rail heights and Code 60 can be used on UK-Image layouts to mimic 3rd and 4th rail systems.

Do you need to worry about the difference?

Absolutely not. Many great show grade models have used Code 100 track. When ballasted properly you can still achieve a great effect, and it certainly looked good on Langstead Junction… However, Code 75 track will look that tiny bit better still. To help you make up your own mind I’ve got hold of some Code 75 track to do a comparison.

In the following picture the shallower rail height is certainly noticeable on the Code 75 track. The sleepers also look less chunky, and better spaced.

Top: Code 100 Bottom: Code 75

The rail height is really noticeable side on:


Left: Code 100 // Right: Code 75

With stock added, the Code 100 doesn’t look too bad and from this angle the difference is less noticeable:

Left: Code 100 // Right: Code 75

Left: Code 100 // Right: Code 75

The front on comparison isn’t great due to the light, but it’s just about clear that Code 100 looks a touch big from this angle although there’s not much in it.


Left: Code 100 // Right: Code 75

From above the Code 100 sleepers look too chunky, and the rails are noticeably bigger. From this angle Code 75 looks great:

Left: Code 100 // Right: Code 75

Left: Code 100 // Right: Code 75

From some angles Code 75 looks noticeably better, but form others the difference is hard to tell. On the other hand Code 100 is tougher, cheaper and curved radius’s come in pre-formed pieces (or set track to you and me), whereas Code 75 is only available in long strips of Flexi-track and can therefore be more challenging to create authentic looking curved sections.

As with most things in modelling there are pros and cons to each side of the argument. I’ve decided to use Code 75 from Peco for my new project, Woodford Wells, as the majority of the track is fairly straight and easy to shape.

If you want to read more about Track Codes I strongly recommend visiting Model Rail Workshop to read the full study and comparison. This post certainly helped me!

– Andy Carter