This article was first published in the hobby magazine www.modelboats.co.uk and was written by Tony Dalton with help from a myhobbystore plan.
My interest in radio control dates back to the late 1950’s and being a Marconi Apprentice at that time, I built my own radio control set which was just a simple tuned radio frequency device that energised a relay when the transmitter was switched on. However, having built the device I did nothing with it as I was only interested in electronics and girl friends! However, I did sell the device to a close friend of my father who was very impressed when it was demonstrated to him.
I have come to realise that within the Luton & District MBC we have a wealth of knowledge regarding radio control of models and during a discussion with Tom Chapman, one of our senior members, he offered me some old radio parts to play with which included some escapements. After some serious thought I decided that it would be a good idea to build a small boat that operated on a simple escapement control principle, one for the rudder and another for the speed. How would modern day enthusiasts that are used to proportional control be able to cope controlling a model having only two push buttons to play with for steering and forward or reverse? Thus my new project was born.
Step 1: Escapement Operating Principles
Step 2: Design of Control System
Having decided on the type of vessel, I then needed to design a control system that would fit within the hull. I would also need to build the system in order to check that the design would function correctly and be reliable.
The requirements for the control system were that it should to be able to control the model by both modern proportional r/c and be able to change over and used as ‘old’ escapement control. To achieve this, the final control in each scenario would be a servo for the rudder and an electronic speed controller (esc) for the motor. When using the servo and esc in a modern set-up, they would be connected directly to the receiver as usual. However, when they were being used under escapement control, I needed to design some form of interface to go between the escapements and the rudder servo and esc. A block diagram of the proposed system is shown in Photo 2. The intention being obviously that the model could be operated in either form, without dismantling the r/c gear and providing a direct comparison of the two methods of operation.
Referring to the coloured block diagram, the system when under escapement control would work as follows:
Power to the esc (dark grey) is supplied from the main battery #1 via the main fuse (light grey). However, the signal lead is not connected to the esc but is diverted to the electronic switch #1 (dark blue). When this switch is activated by the transmitter it triggers the escapement solenoid #1 (light green), releasing the arm of the escapement which turns 90 degrees, switching one of two micro switches. The micro switches are attached to a programmable RC Pulse PCB (light blue) which causes its pulse width to alter. The output of this PCB is connected to the esc thus causing the esc to change from neutral to a pre-determined speed in a forwards direction. Release the switch and the escapement #1 and micro switch are released resulting in the programmable RC pulse and the esc being re-set to neutral. Activate the switch #1 (dark blue) again and the second micro switch is activated causing the programmable RC Pulse PCB #1 (light blue) to alter its pulse width again and change the esc from neutral to a speed in the reverse direction. Release the switch and the escapement #1 and the micro switch will be released resulting in the programmable RC pulse and the esc being re-set to neutral for a second time. This process may be repeated again and again to control the speed of the vessel.
The other escapement operates in a similar same way, but is activated from the transmitter via the electronic switch #2 (light blue). This controls the operation of escapement #2 which in turn operates the servo via its RC Pulse PCB, however the escapement is not clockwork driven, but uses a small electric motor (red) which is powered by the Aux #2 battery via a regulator and a pulse width modulation (PWM) speed controller.
Electronic switches #3 and #4 are operated by the transmitter to control the lighting, siren and blue flashing light.
The next step was to build all the required parts as described and these were duly completed, wired together on the bench and apart from one or two minor glitches, they all worked correctly – hooray! Photo 3 shows all the individual assemblies (one escapement has not yet had its micro-switch board fitted) and Photo 4 is a view of the complete mounting board and r/c items (which includes the motor) and Photo 5 is a close-up of all the electronics. This complete board fits directly into the hull and only requires the connection of the propeller shaft coupling to the motor and the tiller arm to become fully operational. So, having now built and proved the control system it was time to construct the model.
Step 3: Hull Construction
The next step was to clad the bottom of the hull, below its chine line, commencing at the stern with 1.0mm plywood. A single piece either side of the keel was fitted from the stern for about two thirds of the model’s length, the remainder being diagonally planked, including over the lower bow section which was filled with block balsa wood, Photo 8. With the lower hull planking complete, the propeller shaft and twin rudder tubes were installed and bonded into position, Photo 9 and Photo 10 is a view from underneath.
Next came the deck which was cut to its required profile and clamped to the hull framework. The access hatch was marked out by using the hull framework as a dimensional guide. At this stage, the deck planking was marked onto it using a 2H pencil and steel ruler, followed by a coat of oak coloured stain and two coats of clear varnish before bonding the deck to the hull framework as in Photo 11. Here, the control system platform was inserted into the hull, secured and correct connection of the propshaft and rudders checked. The whole system was again function tested prior to its removal to allow for planking of the hull sides. Photo 12 shows this and not how once again single pieces were used for the large relatively flat areas of hull sides. Everything was then covered in a lightweight fibreglass cloth with a coat of resin to protect the hull.
Once rubbed smooth and any defects made good, the hull had four applications of undercoat, again filling any minor blemishes between applications, then two colour top coats and the hull was almost complete. Deck fittings and the POLICE vinyl logos were then added, Photo 13, as easy as that!
Step 4: Cabin
A control console was designed for the cabin and the required parts prepared, then the frame for the cabin and the console unit were all assembled as in Photo 15. Prior to adding the sides and front window panels, everything was painted with white undercoat, including the insides, to improve the brightness of the proposed internal lighting. The cabin sides were then glued to the internal framework together with the front window sections and then the entire unit was given a coat of white gloss paint.
The roof sections were undercoated in grey (on their outsides) and finished with dark blue gloss paint. Photo 16 shows the cabin and the roof sections complete and awaiting final assembly.
The glazing of the windows was carried out before fitting the front roof section which also allowed the assembly and wiring of the port and starboard navigation lights together with the searchlight. The wiring for these was routed along the central roof spar of the aft cabin and channelled down the back of the rear cabin wall. The rear cabin roof was then fixed into position and the rear hatch cover fitted, which had some slots cut into its rear section for a small speaker for the siren. This completed the basic cabin assembly, Photo 17.
Step 5: Final Wiring
Step 6: Finishing Off
In order to make controlling the vessel be more like the single channel escapement systems the 2.4GHz transmitter controls were modified by adding two push button switches to the front panel for controlling the motor power and the rudder respectively, Photo 20.
Step 7: Sea Trials
Step 8: Conclusion
Step 9: Supplier's Data
20Amp Marine Esc: Mtroniks
Mabuchi RX15 Plus Electric Motor: MFA
Searchlight and ventilators: Reade Models
Navigation light housings)
Brass propeller ) Cornwall Model Boats
Ship’s horn )