Cat 990H

January 5th, 2009 Leave a comment Go to comments

Model of a Caterpillar front loader. Features 4×4 drive, suspension, internal electric compressor and two pneumatic circuits, plus a 2-section arm with a progressive geometry.


Completion date: 31/05/2008
Power: electric (Power Functions) / pneumatic (fed from internal electric compressor)
Dimensions:  length 60 studs / width 18 studs / height 27 studs
Weight: 1.56 kg
Suspension: rear – pendular with shock absorbers / front – none
Motors: 3 x PF Medium
Pneumatics: two circuits with manual valves and internal electric compressor

My third front loader, and second Caterpillar model. Although externally very different from my previous Cat R2900G, it is internally pretty close based on it, with a number of improvements. It features the same 4×4 drive, but the rear suspension is shorter, stronger, and fitted with a pair of half-floating shock absorbers that make it stable. Steering system is exactly the same, with the central joint rotated by the horizontal 36-tooth gear, a solution that blends compactness with robustness and precision very well. The compressor is the same too, but here it is driven by a separate motor. It powers two pneumatic circuits, that control two sections of the arm. The arm’s construction is very close to the original, and a particular effort was put to model the bucket-tilting mechanism, quite specific for Caterpillar machines. The arm has a progressive geometry, which means that the bucket slightly tilts forwards as the arm is lowered, and slightly tilts backwards as the arm is raised. The model uses an unique LEGO unitary bucket, whichI was able to buy at a bargain price.

The whole model is more accurate than the previous one, to the point where even the Caterpillar livery is modeled as well as possible without stickers. It has, however, a number of faults: the hull is too tall by 1 stud, the cabin is at least 2 studs too tall, and the rear part is too massive. Additionally, I was unable to model the banisters that cover top part of the original machine, because I had no appropriate parts at the time. Still, it was an extremely playable model.


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  1. Jonas Hansen
    May 18th, 2010 at 15:41 | #1

    Hey Sariel.

    I can see that you use shock absorber in the rear suspension.?

    On a real front loader, there is no shock absorbers used at all.

    The only kind of suspension I know of in a loader is in the seat! 🙂
    And boom-suspension of course ….but to make a replica of that lego is probably almost impossible.

    Kind Regards.
    Jonas Hansen
    Denmark….(The Country of Lego! :D)

  2. Mihály Stépán
    January 10th, 2010 at 20:07 | #2

    I guess so. You mainly benefit from that with off-road vehicles, don’t you?
    Have you ever thought of building a Bobcat, you know, those little four-wheeld beasts that do a wheelie and can turn around in one place? Those are mean little things! 🙂

  3. Sariel
    January 10th, 2010 at 19:09 | #3

    @Mihály Stépán
    It’s always a bit stronger with 4 gears.

  4. Mihály Stépán
    January 10th, 2010 at 18:42 | #4

    Hi! I noticed you use 4 bevel gears inside the differential. There’s nothing holding the 4th one in place other than the two others, right? I guess it’s the common, “old” diff. I tried to jam a 4th gear in it once, but it seemed it wouldn’t go in ‘cuz it’d need to jump over a tooth. Maybe I didn’t try hard enough.. 😛 Is there any reason you used a 4th one?

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