Since I was a child I has been a fan of big trucks, and specially of American style trucks(in Spain is strange to see trucks with long noise).
For this MOC I have chosen one of the most charismatic and representative models of these trucks: a Peterbilt 379.
Also I have endeavored to put a version of CAT C15 engine (I'm also a fan of the brand CAT).
This MOC is made in a 1/10.2 scale, giving a final size of 31 studs width, 99 length and 40 high.
Here you can see some pictures taken in Skaerbaek where you can appreciate the size, there are: this Pete, the Crow's Vampire GT(scale 1:10 too...), the Nathaniel's Supercar and my Veyron.
The total weight is 5.5kg, and has been one of the main problems I've had. Front axles deforms and look like the wheels has huge camber angle. This is a esthetic defect which I hate, but it has not solution if I want to keep all functions and therefore the weight of the truck. I will try to fix it comming soon.
The electric system is huge, and it has:
- 2 AA PF battery boxes
- 4 PF IR recievers
- 5 PF XL motors
- 5 PF M motors
- 1 PF switch
- 3 PF large extension wires (50cm)
Probably, the most “wanted” picture for Lego Technic followers:
When did the truck I always wanted to do it complete, including the sleeper, but later I had to discard it because the cost would have been huge.
The hood can be raised, and remove if you want removing only 2 axles.
Also if the hood is open, you can remove the steering wheel and before remove the cabin in one piece just pulling up on it. Under the cabin you can find both AA battery boxes and the 4 IR receivers.
The two huge fuel tanks are used to cover part of the mechanisms of the truck: on the left the mechanism of the gearbox and on the right part of the pneumatic system.
As curious data, only the bodywork weight is more than 1 kg...
CAT C15 Engine
Under the hood you can find a replica of the CAT C15 engine, with its 6-cylinder in line.
The engine doesn't have the sides covered to appreciate that the cylinders are located in the same order as the real engine, with 120 ° intervals between them. Getting those 120 º between cylinders was very complicated but I thought it was necessary to be more faithful to the original.
The engine also has a motor M to rotate it, which is connected directly to a battery. Between the engine and the M motor there are a differential, which is also connected to the drive motors, so that the engine is always at idling, but when you starts the drive motors the C15 accelerate adding both speeds. The rotation speeds grow up from 250 rpm up to 700 rpm aprox.
After almost 10 years without using pneumatics in any of my MOCs, I decided this was the perfect model to use it.
The pneumatic system the truck runs along the complete truck, mainly controlling the suspension and brakes on all axles.
The pneumatic system is composed mainly:
- 2 Small pumps (6L)
- 1 Large pump (for emergencies).
- 2 Air tanks
- 7 Small cylinders
- 8 Large cylinders
- 7 Valves
- 1 Manometer (LEGO part n.64065)
- 22 T connectors
- And about 5 meters of pneumatic tube in 3 colors: blue, black and light gray.
The pneumatic tube color code is this:
- Blue: general system and suspension
- White: Brakes on
- Black: Brakes off
All pneumatic control is located on the right side of the truck inside the fuel tank.
The pneumatic system starts in the air pumps. A M motor is responsible for operating them asynchronously.
The compressor has auto-stop system, it stops approximately at 2 bars pressure, and restart in 1 bar. This compressor control uses a small cylinder, a PF switch and a small spring to counteract the cylinder. To have enough air to the suspension and brakes the truck has two air tanks, they are located inside the chassis and just above the gearbox.
As the real truck it has live axles. Both rear axles are driven without differential between them.
In each axle between the differential and the wheel the axls has gear ratio 12/20 to reduce necessary torque in the differential and protect bevel gears.
The front axles uses the same steering system as the real Pete, of course the steering wheel turns too, also it turns 4 laps, again as the real Pete
The suspension is fully pneumatic in all axes, and it doesn't use any spring to help.
The front axle has 4 big cylinder and each rear axle 2.
The cylinder are controlled by a valve connected to the same axes. So that the truck can maintain the height to the floor regardless of the weight above it. If the weight increases the suspension is compressed and the valve opens getting more air into the cylinders, then the suspension turns to stretch and returns to its normal height and the valve closes.
If the weight is reduced same thing happens, the valve opens and lets out some air until the pistons down to the normal position.
The brakes as the real truck are drum brakes, there are a drum on each side of each axle, all of them controlled by a small pneumatic cylinder.
The control of these pistons are made through two valves, one for the front axle and one for the rear axles.
For normal braking the brakes operate all at the same time, but only while you are keeping push the brakes botton.
But you have also parking brake mode, if you push the brakes botton in the opposite direction only rear brakes works, and they will not disabled if you stop pressing botton. To remove the parking brake you only need use the normal brakes.
- Auxiliar output
Behind the cabin there is an auxiliar pneumatic output(blue connector), where you can connect anything you want. The valve to activate it is located before the rear-right wheel
The transmission is the biggest mechanism of the truck, and it has an approximate size of 25x7x45 studs.
It uses 4 XL motors for drive.
The transmission has 18+2R speeds(this is true, is not a joke...).
The transmission is divided in two parts: the main gearbox with 9+R speeds with automatic clutch(this gearbox is based on the LR Defender), and a transfer case with 2 speed (H and L)
The main gearbox uses a XL motor to shift gears, it has a speed indicator behind the cabin, and speeds ratio are the next:
1 - 1:0.36
2 - 1:0.48
3 - 1:0.6
4 - 1:0.8
5 - 1:1
6 - 1:1.33
7 - 1:1.67
8 - 1:2.22
9 - 1:2.78
The transfer case uses a M motor, and the speeds ratio:
Low (L)- 1:0.9
High (H)- 1:1
Joint both gearboxes the result is this:
1L (1) - 1:0.324
1H (2) - 1:0.36
2L (3) - 1:0.432
2H (4) - 1:0.48
3L (5) - 1:0.54
3H (6) - 1:0.6
4L (7) - 1:0.72
4H (8) - 1:0.8
5L (9) - 1:0.9
5H (10) - 1:1
6L (11) - 1:1.2
6H (12) - 1:1.33
7L (13) - 1: 1.5
7H (14) - 1:1.67
8L (15) - 1:2
8H (16) - 1:2.22
9L (17) - 1:2.5
9H (18) - 1:2.78
Auxiliar electric output
As I said before, the truck has an auxiliar pneumatic output, but also it has an auxiliar electric output too.
There you can connect anything you want, and control it with the remote controller.
To avoid leaving this connetor without any use I have added a fifth wheel(trailer connector).
- Fifth wheel
Note: right now I don't have intention to do a complete trailer.
It is very simple and effective. The kingpin diameter is 1 stud.
The fifth wheel is on the chassis, but it is not part of it. You can remove it removing only 4 pins.
Finally as always, you can see a complete video with all features showed:
And see all pictures here:
I hope you like it!!