Home > Truck Trial, Trucks > Unimog U900

Unimog U900

My third, unsuccessful Trial Truck. Features 4×4 drive, full indepent suspension and R6 piston engine.


Completion date: 31/03/2009
Power: electric (Power Functions)
Dimensions:  length 46 studs / width 25 studs / height 31 studs
Weight: 1.95 kg
Suspension:  full independent
Motors: 1 x PF Medium, 1 x PF XL

An unfortunate result of my attempt to enter 2009 Truck Trial season with a brand new vehicle. It was intended to be small, lightweight and as simple as possible. Therefore I’ve decided to model the shortest version of the legendary Unimog truck being produced at the time.

The truck was built in a traditional way, with layers of bricks and plates reinforced by vertical liftarms. There were no differentials at all and the suspension utilized the 8880 set’s suspension components, replacing the universal joints with knob wheels as the universal joints get damaged in the Truck Trial quite often. The number of motors and electric components was limited to a single battery box and a single IR receiver controlling drive & steering. For the sake of stability both battery box and the drive motor were located low under the chassis, with the battery box moved close to the rear axle in order to compensate for the cabin’s weight. I have initially intended to build the cabin with liftarms and panels, but I didn’t really like the look of it and eventually chose to build a ‘fullbrick’ cab. I have, however, failed to maintain the proportions and the resulting cabin was too tall and placed a bit too high.

The decision about the cabin has dramatically increased truck’s weight – from approx. 1 kg with bare chassis and 1.4 kg with cargo platform to the final 1.95 kg. It had a great impact on the stability and performance of the model. Eventually it turned out that the truck was having serious problems with everything but driving straight ahead. A meticulous analysis revealed that it was because of the bracings keeping the knobs inside the suspension’s rocking levers. While they performed quite well before, now they tended to bend under the truck’s full weight. As a consequence the knob wheels became slightly displaced, and came into contact with other parts of the suspension. It has crippled the truck so severely that I decided to abandon this chassis design entirely, seeing no space for improvements. My first idea was to rebuild the truck from a scratch, but after a careful consideration I have canceled the Unimog project and started to build a 4×4 truck with longer chassis and two differentials. So after all,  this model has never been driven outdoors.


01.jpg 02.jpg 03.jpg 04.jpg 05.jpg 06.jpg 07.jpg 08.jpg 11.gif
Categories: Truck Trial, Trucks Tags:
  1. Sariel
    September 10th, 2011 at 07:19 | #1

    Because it didn’t work.

  2. will
    September 10th, 2011 at 03:05 | #2

    why didn’t you make a video?

  3. Kshomiv
    March 30th, 2011 at 02:39 | #3

    This thing looks beast!

  4. David
    February 6th, 2011 at 21:11 | #4

    yea i kno but i like the chassis and ive made mocs tht suck but i like to work it out thts why i asked

  5. Sariel
    February 2nd, 2011 at 18:09 | #5

    I guess you missed the small fact that it didn’t work well.

  6. David
    January 31st, 2011 at 15:51 | #6

    i like it post instructions bro;-)

  7. Sariel
    December 1st, 2010 at 23:30 | #7

    94 mm tires on 8880 wheels.

  8. will
    December 1st, 2010 at 23:08 | #8

    what wheels and tires are those because it looks like balloon tires on 8880’s wheels

  9. Sariel
    November 25th, 2010 at 20:59 | #9

    And all it takes is to download instruction from here: http://sariel.pl/downloads/

  10. November 25th, 2010 at 17:57 | #10

    how the hell can you get 4WD and steering? i have been working on it for months

  11. Sariel
    September 5th, 2010 at 20:02 | #11

    Yes, I did not.

  12. will
    September 5th, 2010 at 19:50 | #12

    so did you not compete for most of the 2009 truck trial season

  13. kyle
    June 10th, 2010 at 13:45 | #13

    i own the 8880 set and the new 4×4 off roader set and never relised that the whells where the same size untill now and am inspired to built something with them thank you sooooooooooooooooooooooooooooo much

  14. Sariel
    April 2nd, 2010 at 18:52 | #14

    At least $1500, I think.

  15. matthew
    April 2nd, 2010 at 18:45 | #15

    How much would one of these trucks be worth?

  16. MoseMor
    March 3rd, 2010 at 20:01 | #16

    @Sariel Thank you, maybe i will post it on Youtube some day 🙂

  17. Sariel
    March 3rd, 2010 at 15:37 | #17

    I simply make sure that gears are braced in something firm & tight. If they have no place to slip, if they are kept together by something, they won’t slip. You have to place them inside some strong structure.

  18. MoseMor
    March 3rd, 2010 at 15:02 | #18

    I`m building a pretty large truck right now, but because of the weight the gears slips, and the truck gets weak. How do you make your trucks so heavy, without making the gears slip? Nice unimog 🙂

  19. jack w
    December 2nd, 2009 at 12:18 | #19

    ahhhhh! that is exactly what i tried to build about 12 years ago! mine is way less detailed: no suspension, balloon tires with d-cell battery caps as hub caps, a differential for no reason (no motor), manual steering, i just recently put rear steering on it but it is terrible. !!!!

  20. Sariel
    September 5th, 2009 at 21:28 | #20

    The same. It slightly touched the tire.

  21. arnau
    September 5th, 2009 at 20:10 | #21

    I’m building a 4×4 and I’m using the same wheels an tires as you, but when I put the steering link it touches with the tire. how did you put the steering link on your Unimog?

  22. legobuilder
    July 14th, 2009 at 12:26 | #22

    ow ok

  23. Sariel
    July 13th, 2009 at 16:02 | #23

    I’ve seen it, I don’t think it’s really fit for Truck Trial. It has a low ground clearance and an apparently short travel of suspension. Anyway, I already have a prototypical chassis for the Alvis.

  24. legobuilder
    July 13th, 2009 at 15:30 | #24

    Maybe I know a very nice truck trail model the BARC it’s a heavy tank transport amphibios vehicle big enough for trucktrail

  25. Sariel
    April 13th, 2009 at 20:03 | #25

    Easily if there are 3 studs of space between them.

  26. Arnau
    April 13th, 2009 at 19:44 | #26

    I don’t understand how you can fit knob wheels between the two liftarms.

  27. Sariel
    April 9th, 2009 at 16:22 | #27

    Ta belka nie łączy kół. Pod nią jest 16-studowe cięgno które łączy zwrotnice, ale nie jest ono przymocowane do podwozia, tylko wchodzi pod tę belkę w taki sposób, żeby nie przesuwało się na boki. Poza tym jest luźne, więc tylne zawieszenie może pracować.

  28. Brydol
    April 9th, 2009 at 13:39 | #28

    Jeżeli połączyłeś tylne koła sztywną belką, to jak w takim przypadku działają wahacze ?

  29. Julian
    April 6th, 2009 at 00:52 | #29

    I love it

  30. julian
    April 3rd, 2009 at 13:33 | #30

    Awsome it is very realistic in particular the motor between the seats.

  31. Sariel
    April 2nd, 2009 at 22:01 | #31

    Yes, they are 94.8 x 44 R tires. The piston engine had moving pistons made of 3-studs long axles with stop.

  32. djtermoz
    April 2nd, 2009 at 21:30 | #32

    Forget the performance, proportions, etc…

    Love it! Looks decent, definitely like an Unimog. What kind of tires did you use with 8880 wheels? Are those maybe the 94.8 x 44 R balloon tires from the 8297 set? I had no idea there are other (truck) tires that would fit those rims.
    Was that a working engine or just a dummy?

  33. Sariel
    April 2nd, 2009 at 13:27 | #33

    No, I took it apart promptly after taking photos.

  34. legobuilder
    April 2nd, 2009 at 13:21 | #34

    can you make a video?

  35. Sariel
    April 1st, 2009 at 21:41 | #35

    Thanks. I am using a backdrop (a 2x10m paper reel) plus special lamps for photography. White backdrop is excellent for the black models, because of how it reflects in their parts. I just wish I’ll be able to get a decent camera sometime soon.

  36. Murcielago53
    April 1st, 2009 at 21:37 | #36

    at least it looks awesome. Can’t wait for your next 4×4.
    One question about your pictures, are you using a backdrop, or editing software to make them look so clean and professional.

  1. No trackbacks yet.