Click on image

for video




Model Railway Drop-in


A drop in is a great way of adding additional interest to any layout. Uppin Doon contains drop-ins that allow us to completely change the style of the layout by replacing plug in modules.

A drop in is also the easiest way to build a section of layout containing animations that would otherwise be difficult to build in situ. Drop-ins can also be easily removed for maintenance or may even give access to otherwise inaccessible track in a tunnel.

The drop-in featured here is part of a quarry scene, but as it is set into a hillside it also provides access to the track beneath. The main animation consists of an excavator which has a rotating cab, working jib, and sound effects. The electronics are provided by PMP kits. Please refer to the PMP kit instructions explaining how these kits can be linked together. A video of the excavator in action is available on this website.

Rotating the cab is quite straight forward and this alone will provide an interesting animation.
The drop-in is best made from thin plywood, which will provide a light, and strong base which is easily cut to shape.

The Excavator

The excavator is a Corgi Trackside Ruston Bucyrus 19 Skimmer, but this technique can be applied to most diecast excavators. Diecast models have the advantage of having some weight and the ability to drill holes in the body.


The first task is to separate the base of the excavator from the cab. Some models are held with screws but others may require rivets to be drilled out.
The base of the excavator can now be fixed to the drop-in base using hot glue, epoxy etc.
A 4.5mm hole is then drilled through the base of the excavator, and down through the drop-in base, at the point where the cab turns.
A short piece of 4.0mm brass tube should now be able to pass through this hole and turn smoothly.

Fix the upper end of the tube to the cab pivot point using epoxy. The brass tube should now slide through the hole in the base and the cab should be free to turn.
The opposite end of the brass tube will be attached to the horn of a servo motor, held in place by a suitable bracket.

At this stage it only requires the addition of an EzyPoints kit PMP18, and a switch, and you will have an excavator that will rotate.



The movement of the jib is a little more complicated but also uses an EzyPoints kit.
Drill a hole in the base of the cab to allow a strong thread to be attached to the jib and passed through the drop-in base. The thread is attached to the horn of the servo, this time orientated vertically. An extension to the arm may be needed to gain extra travel.

This section is very much a case of experimenting to obtain the correct length of thread and travel of the servo. Deluxe Materials “Liquid Gravity” has been added to the bucket to add the necessary weight to enable the jib to be lowered
Once again, at this stage the jib can be operated manually via an EzyPoint kit with a switch on the second servo.

Automating the cab and jib

A simple way of automating the cab and jib is to use the event sequencer PMP26. This will enable you to set the time duration for the cab and jib. The advantage of the event sequencer is that no programming is required.

Adding a delay

The event sequencer will continuously operate the cab and jib once it receives a trigger, however, for more realistic operation the addition of the versatile timer PMP20 will allow you to set the duration of the event sequencer trigger and therefore the excavator will only run for specific periods.

Adding sound

Adding sound is the icing on the cake. Although not available as a PMP kit, the WTV020 is a simple sound module described in Davy’s eBook, Part 1 Chapter 10. Any sound module that can accept sound files and has a trigger could be used.

Connecting the PMP kits


In its simplest form this drop in only requires one EzyPoints kit with a switch, to rotate the cab.
Adding the event sequencer enables the addition of the jib, sound, and even more. This excavator has an interior light which comes on as the first event, followed by the sound, jib, rotations. Adding an additional event sequencer could drive further animations on the same drop in. The options are almost endless.
Adding the versatile timer allows you to control the period of running of the entire sequence of events. This is highly recommended as some animations, particularly those with sound, can become irritating if operated continuously.

Keith 22.03.20