The Lego 8285 Tow Truck - MODed

[Dutch_EE]

Hi, I'm new to this forum. My name is Sander Fondse and I'm 23 years old. I'm a Electrical Engineering Master Student at the Technical University in Delft. I've been collecting

Lego Technic since I was 9.

I would like to present to you my version of the 8285 tow truck. I bought it in Germany when I was on holiday there in 2007. I think this

model is beautiful, but it lacks a bit in functionality given it's price. When I read the review of the model at this forum I was inspired to

try and improve it to make it a worthy Technic flagship. It was important to me to keep the look of the original model.

The modification started with the installation of an XL-motor that drives the rear axle via a 8:24 reduction, as well as an M-motor for steering.

I first used a wormgear for this, but that didn't work, as there was too much torque on the gear. I replaced the steering by a direct 8-24

clutchgear and the motor was relocated under the cab. I was able to squeeze in a battery box behind the far side panel. This hid it away nicely.

The receiver was lowered into the cab after I removed the wormgear assembly that drove the back support arms.

After this, I had a working RC truck, but I still wanted more. I therefore decided to remove the complete crane assembly and replace it with a

motorized version. With a M-Motor and a clutchgear a 4 way gearbox is operated. The gear-handels are located behind the 2 rear flaps, as were the

hand-knobs of the original. The M-Motor is controlled with a PF-Switch that is located behind the flap on the driver-side. On the far side the

pneumatic valve of the tow arm found it's place again like in the original model. With the 2 gear-handles the following 4 functions can be

operated :

1 - raising and lowering the crane-arm with a linear actuator

2 - extending the crane-arm

3 - operating the winch with a wormgear

4 - pneumatic pump

The pneumatic pump was necessary, because I found the original hand pump a real eyesore. The air-spring for the towing eyes was the next victim.

I hate air-springs, because they always seem to break after a while. I replaced the air spring with a large cylinder. Afterwards I

remembered that I had removed the wormgear for the back supporting arms. With help of a small cylinder and a crank I made this function pneumatic

as well. These are the 3 pneumatic functions.

a - raising and lowering the tow arm (only origional cylinder)

b - raising and lowering the towing eyes

c - raising and lowering the back support arms

The 2 valves for the functions b and c are on the back of the truck on the far side.

I still found some room for further improvement, so I did some small jobs like

- A detailed engine bay with simulated intake and exhaust

- Working headlights by a PF-switch on the roof

- shortened front half-axles like the suggestion for the crane truck 8258

And finally, I found that the truck didn't have enough traction. To solve this, I build in a differential into the second back axle, making

this a driven axle as well.

This was a summary of one of my most worked on models and one of my all-time favourites. I can off course take more pictures ;)

[RockeTeK]

Sounds great, and looks great aswell! I would like to see a few more pictures, I might try this myself

TUD rocks!

[richthelegodude]

Great work!, I am also an Electrical Engineering student (I got my bachelors and then masters degrees a couple of years ago - I am now a PhD student) - I guess a lot of electronic engineers like technic

[Dutch_EE]

Here are some extra pictures.

First, the underside with the new drive-shafts.

It was a real pain to rebuild the drive-axles to drive both rear axles. Both have a differential. To fit in that second diff, I had to raise the pneumatic cylinder from the tow arm. The XL-Motor for drive is seen, as well as the propshaft that goes to the engine via some U-joints.

The second picture is taken from the de-rigged far-side. Here the batterybox is clearly visible as well as a shifter of the gearbox (red) and the pneumatic valve that operates the tow arm.

Lastly, this third picture shows the insides of the model beneath the linear actuator. There are 3 things visible. On the top left the gear that lengthens and retracts the crane arm is seen. On the top right sits the gear that drives the winch. Also, the pneumatic pump is seen. It took some real thinking to cram it all in. And at the top left the switch of the headlight can be seen.

[legolijntje]

That looks great!

I have the 8285 too and I've thinking about motorize it for a while now. This gives me a bit inspiration, so maybe I'm gonna make my own version soon.

BTW: Can you make a video of it?

[Dutch_EE]

BTW: Can you make a video of it?

Don't ask about the quality. I only have a Kodak C813.

http://s80.photobucket.com/albums/j177/San_fo_se/?action=view&current=101_0270.mp4

The truck driving - The steering still isn't perfect

http://s80.photobucket.com/albums/j177/San_fo_se/?action=view&current=101_0265.mp4

The crane arm going up

http://s80.photobucket.com/albums/j177/San_fo_se/?action=view&current=101_0268.mp4

Extending/retracting the crane arm