The model used for this conversion wasÂ 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 share 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 possibleÂ drilling mistakes andÂ makes the build much simpler.
Don’t think this conversion is a walk in the park though, if you want all the LEDs of a real artic lorry you’re going to have to run a lot of wires.
I used aÂ Hobby King Servo HK15178 for the steering simply because they wereÂ cheap, I had a few and theyÂ worked out well in the tractor builds.Â It wasÂ 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.Â Control of the steering wasÂ relatively simple as the shaft running through the cab for the manual steering meant there was many possible mounting pointsÂ for the steering servo.
Main Drive Motor
I used the motor from a Siku Control 32 Scania R620 which I bought on the Modelbau Schulte website so this made installation very simple as I simple had to bolt the motor in place. I tested the motor with the TB6612FNG motor driver and 3.7 volt battery and it works perfectly.Read more...
Fifth Wheel Coupling
The Siku R620 model comes with a small level 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 it have 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 moduleÂ 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 from to the output of a few volts.
I have been upgrading my models to all use 3.7 volts if they have a trailer so that every model can easily use the same trailers. They also need to use NRF24L01 radio modules because the are cheaper and I am building quite a large collection of vhicles, over â‚¬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.
Mounting the LEDs for the head lights, indicatorsÂ and brake lights was fairly simple as the holes for the LEDs are already drilled in the body of the lorry.Â 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.Â Running all the wires was quite difficult so try to minimise the amount of wires you need if you can.
I need to rethink the wiring of the LEDs for the 3.7 volt system as they were designed for 7.4 volts so the resistors need to be changed. Also the NRF24L01 requires more Arduino pins than the XBee so I will need to solve a shortage of pinsÂ too.
RC Scania R620 Circuit Diagram
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 theÂ videos related to the RC Scania R620, follow the link below to visit the playlist onÂ the RC Tractor Guy YouTube channel.
RC Scania R620 Code
The code for the Scania R620 can be found in the RC Tractor Guy Library.