Sariel.pl

Model of modern F1 car inspired by Ferrari 248. Features RWD, steering, suspension, 2-speed transmission and custom stickers.

Datasheet:

Completion date: 12/05/2015
Power: electric (RC unit)
Dimensions: length 73 studs / width 31 studs / height 18 studs (not including antenna)
Weight: 1.709 kg
Suspension: full independent
Propulsion: 2 x RC motor geared 3:89:1 (low gear) / 1.4:1 (high gear) from slower output
Motors: 2 x RC motor, 1 x PF M

I’m no expert on F1 but I wanted to try building a modern F1 car for a while, especially since my experience with the Lego 42000 Grand Prix Racer set left me feeling that perhaps the same thing can be done better and prettier. Since the latest, top-of-the-line F1 cars seem complex beyond my grasp, I took inspiration in Ferrari 248 F1 car from 2006. It was a car driven by  Michael Schumacher and Felipe Massa, it has experienced some serious engine problems at the beginning, but once these got fixed, the 248 has proved to be an excellent car, winning 7 out of the 9 season’s last races. My reason for choosing it, however, was primarily aesthetic, I simply liked the look of it. And since my model was supposed to drive nicely above all, I decided that its look would be less important and that I wouldn’t try to make it a very accurate model of the 248. In the end, the model has 248’s basic dimensions, livery and most of the sponsors on it, but the body shape is somewhat different. I suppose it looks much like 248, but I don’t think it’s accurate enough to pass as a scale model of 248.

It was clear from the beginning that it wouldn’t be a record-breaking model, not with room for single Lego RC unit and two RC motors only. But I wanted it to be agile at least, and I decided to use this opportunity to try making an effective 2-speed transmission. A common and well-known problem with Lego transmissions is that they add extra weight, friction and complexity, so that in the end all benefits of a transmission are lost and the model would drive just as well without it. While working on this model, I’ve dedicated plenty of time to finding simplest construction possible and most efficient gear ratios for a model of this weight, with these wheels. Doing this with F1 car was a good choice because I had good access to the transmission right until the end of the building process, and I was able to make changes to it right until the last moment. The finished transmission was heavily optimized for this particular model and probably wouldn’t work that well for a car whose weight, wheels and propulsion motors are different. It was also built literally around the rear axle due to size constraints (most of the hull was taken by the RC unit), with the rear differential passing through its middle.

I was rather happy with model’s look. It was by no means perfect: the side air intakes could be moved forward a bit, the rear wing was slightly too tall, and the hull should be narrower – but the RC motors located in the side pods wouldn’t allow it. The worst bit was definitely the PF M motor sitting on top of the hull’s center and controlling transmission through exposed gear wheels. I have failed to fit it in one of the side pods, and since I needed the transmission to be reliable and effective, the looks of the model had to be compromised. To make the looks more authentic, I have created 52 individual stickers representing logos of various brands that sponsored Ferrari team over the course of several seasons. I have skipped cigarette and alcohol companies and selected from among others, with Vodafone and Shell being typically primary sponsors of the 248. All the stickers were printed on a white sticker foil, then cut by hand. I managed to get them to match the red color of the Lego pieces pretty closely.

On the technical side, the transmission relied on a single driving ring sitting on a smooth axle joiner, so that it could be shifted between two speeds instantly and smoothly. Shifting could be done while driving at full speed without any problems or slowing down. The transmission was connected to a simple lever moving the rear wing and activating a red light brick at the back. In 1st gear, the rear wing was lowered and the light brick was off, and in the 2nd gear the rear wing was raised and the light brick was on. There was also a steering system using the RC unit’s steering output. It was connected to the steering wheel, and it was using complex spindles in the front wheels that pivoted very nearly to the wheel’s center, and that were steered using reverse Ackermann geometry. I have observed large backlash between inner and outer front wheel when cornering, and the reverse Ackermann geometry was intended to counter it – I wanted it to even out the backlash and keep the wheels aligned when cornering. In the end it’s difficult to reliably show or measure if this has worked as intended, but the model’s steering system proved very responsive, and I have later read in Wikipedia that reverse Ackermann is, in fact, a real-world solution used in some race cars to compensate for the large difference in slip angle between the inner and outer front tires while cornering at high speed.

The model was a pleasure to drive and I was especially happy with how reliable it proved when tested outdoors. It was reasonably fast, slower than many of my other models, but still quite agile for its size and weight. It also looked pleasing to the eye, even though I was initially planning to build it in some unusual colors, e.g. combination of white and two shades of blue, just to make it stand out more from the official Lego F1 sets. But in the end, I suppose it can’t be mistaken for a Lego set.

Work in progress Photos:

Photos:

Video:

Media coverage:

Autoblog (Dutch), Autosaur, Car Throttle, Damn Geeky, Gizmodo, Motorpasion (Spanish), RC Car Action, The Lego Car Blog