The model used for this conversion was a Siku no. 3295, a diecast model of a Scania R620 Topline articulated lorry. I chose this model simply because I wanted to do a artic lorry conversion and the SIKU Scania models have exceptional detail including the Scania griffen emblazened along the cab. It wasn’t a difficult choice given that most alternative are plastic and don’t have functional steering.
After taking the lorry apart for the first time, it quickly became clear that the static Siku model shares a lot if not all components with the Siku Control 32 Scania. The steering arm goes through a plastic component which is shaped like the body of a servo yet serves no purpose other than to guide the steering arm. Clearly the steering servo for the Control 32 version fits into the space occupied by this plastic dud. Another useful feature is that the lights on this model have holes for various LEDs which cuts down on possible drilling mistakes and makes the build much simpler.
Final Design Costs
These are the costs of the components used in the final design.
|Siku Scania R620 Model||1||€50.00||Siku No. 3295|
(€90 including low loader)
|RC Tractor Guy Vehicle Control Board||1||€15.00||RCTG0001 – V4|
|Small Dual Motor Driver Board||1||€8.00||RCTG0002 – V4|
|Motor, Gearbox and Axle Assembly||1||€27.90||From Siku Control R620|
|Digital Photo Key Ring||1||€4.62||Used to show images in cab|
|Hobby King HK-15178 Servo||1||€2.00||Steering servo|
|Hobby King HK-5320 Servo||1||€2.38||Used for fifth wheel|
|LEDs, Switch, Transistors and Resistors||€1.00||Bought in large quantities|
I used a Hobby King Servo HK15178 for the steering simply because they were cheap, I had a few and they worked out well in the tractor builds. It was too large to fit into the hole which houses the SIKU servo so I mounted the servo underneath the cab of the lorry and connected it to the bar which operated the manual steering of the static model. Control of the steering was relatively simple as the shaft running through the cab for the manual steering meant there was many possible mounting points for the steering servo.
Fifth Wheel Coupling
The Siku R620 model comes with a small lever to operate the catch on the fifth wheel coupling. This lever is connected to the coupling via a thin stiff wire running inside the body of the lorry. There was another fake servo under the plate covering the lever mechanism so I removed this and replaced it with a Hobby King 5320 servo. I needed to add a small plate to mount this and while it’s a weak servo and is a little jittery, it has enough power for this application.
In the first version of the R620, I used a single Arduino Pro Mini to control the features of the module with an XBee radio for communication. The whole system was powered from a 7.4 volt battery because I was using an L293D motor driver which had a large voltage drop from to the output of a few volts.
I upgraded a lot of my models to use 3.7 volts if they had a trailer so that every model can easily use the same trailers. They also needed to use NRF24L01 radio modules because they are cheaper and I am building quite a large collection of vehicles, over €20 per XBee was just too much.
I also need to use the TB6612FNG motor driver because the L293D can’t drive the motor from 3.7 volts.
The Scania R620 stopped working at one stage and I never figured out the problem so it sat on a shelf for a long time. After I had a batch of RC Tractor Guy Control Boards V4 manufactured I decided it was time to update it with the new system. The circuit diagram and code below is for the latest version using the RC Tractor Guy V4 control boards.
Mounting the LEDs for the head lights, indicators and brake lights was fairly simple as the holes for the LEDs are already drilled in the body of the lorry. The headlights are drilled for 3mm LEDs and the indicators are drilled for 1.8mm LEDs. I also added 5mm super bright white straw hat LEDs to the front and some 1.8 mm blue LEDs in a V shape in the grill just for aesthetics. Running all the wires was quite difficult so try to minimise the amount of wires you need if you can.
I needed to rethink the wiring of the LEDs for the 3.7 volt system as they were designed for 7.4 volts so the resistors needed to be changed. Also the NRF24L01 requires more Arduino pins than the XBee so I combined some circuits to simplify the model.
In Cab Display
I purchase a small digital key ring which has a small screen to display a number of small images. I saved a few Scania logos so that it might like like the LED displays you see on the back wall of the cab in many artic lorries. I simply uploaded the images to the device, removed its casing and battery and wired it to the power switch on the model. Not when the model powers up an image displays for a time at least although it does time out after a while.
RC Scania R620 Circuit Diagram
Here is the schematic for my Scania R620 in pdf form. This model uses the RC Tractor Guy’s control board version 4 which is a compact version of an Arduino Pro Mini with a built in NRF24L01 radio module. It then uses the RC Tractor Guy’s small motor driver board which has a TB6612FNG motor driver to drives the Siku control 32 motor.
Scania R620 YouTube Playlist
There are many videos showing the functions of the original Scania R620 build on the RC Tractor Guy channel and a few videos of the new design being built. If you want to view the videos related to the RC Scania R620, follow the link below to visit the playlist on the RC Tractor Guy YouTube channel. Don’t for get to subscribe and put the notification bell on so you don’t miss out on newest updates