[MOC] RC Kenworth W900A (-inspired) truck with flatbed trailer

[lcvisser]

I'd like to present my interpretation of a Kenworth W900A truck with flatbed trailer. The truck started with the idea of participating in a Load Zone competition, but I was a bit (very) late to the party. I also got a bit carried away, so I think it would be a poor contestant. However, the functions are still following those required by the Load Zone rules.

The truck has the following features:

1. 6x4 drive on rear axles
2. Steering with Ackermann geometry for tight turns
3. Opening doors
4. Cabin interior
5. Lot's of details

The truck has 4 remote controlled functions:

1. Drive: PU XL motor
2. Steering: PU L motor
3. Trailer coupling: PU L motor
4. Trailer power: PU L motor

It was a huge puzzle to get everything inside:

The battery box is tucked in the sleeper cabin. Because it's a pain to get it in and out, I hid a pinhole behind the A/C unit to push the on/off button:

The trailer has the following features:

1. Completely flat loading bed
2. Landing legs
3. Parking brake
4. Tandem can be move forward (better load distribution) or backwards (easier manoeuvring) by removing two pins and sliding the tandem unit

The trailer has 2 remote controlled functions, actuated via the fifth-wheel coupling with the truck:

1. Landing legs raise/lowering
2. Parking brake

The fifth-wheel coupling is very simple, but it works very well, because it is form locked:

On the kingpin of the trailer is a gear that rests on the coupling plate, to transfer the power:

I made a small video to show how it works:

There is a differential hidden in the trailer that splits the power to the landing legs and the parking brake. Because both the landing legs and the parking brake have end stops, the differential ensures that first the lower-resistance function is actuated to its end stop and then the other function follows. Typically, the landing legs go first, then the parking brakes.

The parking brakes are a simple rubber connector pushing on the wheels:

The tandem can slide forwards and back by removing the red pins:

When the tandem is forward, you can make much tighter turns, but with the tandem back, the trailer is much easier to back up. In practice, however, it's a bit hard to reach the pins to unlock it, so this is one of those things that seem a nice idea in theory but is never used in practice 

 

Overall I'm very happy with the result, but of course there's room for improvement. I really like this scale with the 49.5 x 14 wheels, so expect more to come.

High-resolution photo's can be found on BrickSafe. Stud.io models of the truck and trailer can be found there as well, although they are not stepped, so I don't know how suitable they are for building. The PyBricks code is on my GitHub page.

Thanks for reading!

[Saruzeufel]

Really good looking model. Nice, how many functions there are for a tuck this small using PU.

I especially love the slightly messy way the trailer lock and trailer power are built.

[lcvisser]

Thanks @Saruzeufel! I started with that trailer power connection, the rest kind of followed from there