The Burrell door lock is a T-head bolt with flat sides on the threaded section. This bolt goes through the door from the back, a handle with a slot then goes on allowing the bolt to be rotated. A second handle with a threaded not then allows the bolt to be pulled up tight.
In the smokebox a beam goes across the diameter of the opening and has a slot in it to allow the bolt head to go through. Then the bolt is rotated and hence the T-head gets a purchase on the beam.
This means the bolt and two handles remain part of the door even when it’s open.
The tricky part of all this is the Burrell is just 1/20th scale. Hence the T-head bolt is made from an 8BA hex head steel bolt.
The door hinge is a simple brass tube cut into 3 pieces and a steel pin through the centre.
This then leaves the hole in the centre for the bolt that pulls the door shut.
The first task was to mill the U-section into the 3/16″ square mild steel beam. This was done using a 3mm slot drill and then finished at 3.5mm wide with an end mill.
Once this was done I then created the 1.5mm wide slot with 2.3mm hole in the centre.
Hopefully the slot in the beam and the T-head on the bolt now make sense.
Viewing the closed door from behind you can see the T-head of the bolt rotated.
The T-head on the bolt is wider than 3.5mm so that it can only rotate a small amount once into the U-section of the beam.
Now for the pair of handles that rotate the bolt and then tighten it. As you can see, these handles were made from 3 parts silver soldered together before they were then cut into 2 separate handles. This just allowed me to initially work more easily and to get a purchase whilst silver soldering.
The image on the left shows the slot that was milled into the end of the brass. I drilled the end 1.5mm diameter before then just widening it into a slot. This then was checked against the flattened thread on the bolt. The other end had the centre tapped 8BA before I then soldered the handles to the brass rod.
I use the Cookson Gold easy flo silver solder paste, an excellent product for parts of this size.
The handles laying on the door after they had been soldered into one part.
Hopefully in this image and the following image you can see that the threaded section of the bolt has been filed flat each side. This allows the handle closest to the door to rotate the bolt and hence the T-head.
Now the Burrell has a door that locks as per the fullsize engine.