Converting a Dapol Sentinel Shunter to Scale 7


Peter Mann


24th April 2020

Reading Time

4 minutes

Before the conversion – a quick explanation of ScaleSeven. The models are exactly the same size as O gauge  – with a scale of 7mm to 1ft . The difference is in both the gauge of the track – which is 33mm between the rails – and a wheel profile which matches closely the real thing. ScaleSeven modellers achieve smooth running on more realistic permanent way. Working to S7 standards is no more difficult than working to any other finescale gauge or standard (eg 2mm FS used on “Copenhagen Fields“, EM used on “Orchard Wharf” and “Minories“, or others like Scalefour and S scale.) and they are all a good step from Ready to Run if you care about the appearance and running qualities of your models. The S7 Group was formed in 1989 with the intention of making life easier for 7mm scale modellers wishing to use track and wheel standards derived from the prototype. This article will appear a forthcoming edition of their Newsletter. To find out more about S7, visit their website, and to find out more about modelling in S7 at the MRC check out our group layout “Bow Junction“.

For several years I had been admiring a fellow modeller’s Sentinel shunter when he brought it to run at our S7 SE meetings.  So when Dapol announced, about two years ago, that they were going to produce an RTR model of a Sentinel shunter, I decided to buy one. I ordered it from Hattons in the Autumn of 2018, and I finally received delivery in December 2019.

I knew that it would have to be converted but I did not give it a lot of thought, but I had a feeling it would not be too difficult because it did not have a chassis that came close to the outside face of the driving wheels, which is the case with the Dapol Pannier .. I had studied the Dapol Pannier in detail with a view to buying one but I realised that it would be difficult to convert.

Returning to the Sentinel, I had it for about 3 months before I did anything while I was thinking how to do the conversion. Then suddenly I realised it may be possible to just push the wheels out. The longest part of the operation was finding the tools for the work.

Ideally you will need the following tools:-

  1. A pair of long nose pliers
  2. A small cross head screw driver
  3. A parallel punch where the diameter of the punch is slightly smaller than the diameter of the axle.
  4. A small vice.
  5. An S7 back to back gauge
  6. Two small slot screwdrivers.

The first task is to remove the brake gear since it is obstructing the retaining cover which keeps the wheels in place.

On the first sentinel I converted I damaged the brake gear in removing it but it helped me realise how to do it properly.

On the second loco I used the Long nose pliers to give a straight pull on the brake shoe. This broke the grip of the glue and the brake shoe came out . I repeated this to the other 3 brake shoes. I was then able to take out the screws retaining the cover plate. I was then able to remove the wheel sets.

I then placed one of the wheel sets across the partly open jaws of the vice. Then using the punch I gently tapped until the axle had moved just under 1mm. I then turned the wheel set round and tapped the axle down the same amount. It is important that each wheel is moved out by about the same amount in order that the gear wheel on the axle will still properly align with the rest of the gear train

I repeated the operation with the second axle. Then using the back to back gauge in the vice I squeezed the wheels down onto the wheels.

The next task was to bend out the pick up tabs on the chassis so that they would reach the back of the wheels in their new position. I used the two small slot screwdrivers to do this

I then reassembled the loco and tested it. After cleaning the track it worked well.

Peter Mann


If you’d like to find out more about joining the MRC- click here to join the Club

Leave a Reply

Thursday Track Nights

We are open on Thursday evenings from 7pm to 9pm at our Keen House clubrooms. Visitors are welcome, please come along and introduce yourself.


Keen House, 4 Calshot Street, London, N1 9DA

Become a member  

Get our newsletter

Sign up to receive all the latest updates direct to your inbox