We are no doubt spoilt by the Bachmann Mk1 as they enable a good looking train to be modelled pretty much out of the box.  However they are not perfect and there’s quite a bit we can do to make them better.  I’m going to start by looking at brakes.  Theres some good books on the subject of Mk1 coaches and the HMRS book by Keith Parkin is considered the first place to look.  However in my copy (the first edition) there’s little info on air and dual brakes although there are later supplements that may cover this. Theres also a new book just come out that covers Mk1 and 2 coaches, I don’t have a copy yet but a review can be read here – MaxStaffordsKennel

Vacuum Brakes

Lets start with vacuum brakes as that is what your mk1 will have (even the NEA does!).  Basically all that’s missing is the dynamo belt (ok not part of the brakes but as it’s in the general area I’ll include it), dynamo safety chain and push rod linkage from the body to the bogie. Theres 2 types of the latter depending on the bogie fitted so we will look at the BR1 bogie first.  Masokits do a handy little etch of linkages and the Dynamo belt that can be used here.

Here you can see the dynamo belt and chain (40 links per inch from A1 models) along with the linkage to the bogie.  On a BR 1 bogie the linkage feeds under the bogie while on a B4, B5 or Commonwealth bogie the linkage feeds above the bogie.  The cross rod has been replaced so that its wider and the linkages made up from the Masokits etch.

Here we see the vacuum brake arrangement for a Commonwealth bogie – you can see how the arrangement is the other way up. This version is far less obvious when the coach is the right way up.

Dual Brakes

As the name suggests, dual brakes are both vacuum and air , the following prototype pictures show the important bits

Dual brake arrangement – the Vacuum cylinder is upper left and the air brake cylinder is center and to the right. Both Cylinders link to the same cross rod.

The air brake cylinder

The Air tank and air distrubutor. This arrangement appears at one end of the coach only.

The model version – The air brake cylinder is from S kits and th vacuum cylinder from a spare Bachmann coach (this is a DC kits underframe)

Please excuse that the body isnt fitted properly yet – The air tank end. The tank itself is from Genesis kits and the distributor from S kits. A few bits of wire make it look like they should do something!

Air Brakes

An air braked mk1 essentially has the vacuum cylinder replaced with an air cylinder like so,

The vee hanger is in the wrong place as supplied and needed moving back towards the center of the coach (this only applies to an air braked Mk1 ) Spare vee hangers are on the masokits etch.

The NEA the right way up!

Finally an odd ball.

These comments are not based on any engineering knowledge of how railway vehicle braking systems work but mearly based on replicating what I see.  However I came across an NBA at Bescot (94528) that had a different air brake arrangement

Its Air braked but more in like with a dual brake conversion – perhaps it was and the vacuum gear has since been removed?

Edit

Thanks  to some helpful feedback from Keith Norgrove the arrangement of the Vacuum cylinder as supplied is correct for some BR1 fitted mk1s only.  BR1 bogies come with both over bogie and under bogie push rods and as supplied the coaches are correct for the under bogie ones.  For the others, Commonwealth and B4 or B5 you need to use the over bogie push rods and swap the vacuum cylinders arround so that they are outside (ie towards the vehicle end) of the Vee Hangers.