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Tuesday 26 January 2010, by HUN_Lac

See it online

Technical data

Scale (wheels used)
Width 28 studs
Total Weight 2700 grams
Transmission 8x8
Motorization 2 motor(s) - RC

working fake motor
Steering motor

with steering wheel
Onboard Battery Box RC

Hi Everyone!

This is my first 8x8 trial truck, but i think it’s worth to post :). It’s not yet finished, I plan to improve the rear suspension-axle-gearing, and also to make a better outlook (to suit "international" rules in that way).

I have built 3 TT-s during the last 2 years, and then i decided to make something bigger, with similar front axle i used in my hummer "TT".
My main aim was (just as before) to achieve maximum efficiency, decrease the amount of gearing, while making a drivetrain that is strong enough to stall the motors if the "hand of the God" (=me) block the wheels, without anything like this:

Great "spring distance" (not sure that’s the correct expr.) was also between my aims. As it is a TT the low center of gravity is also crucial, so i fixed the place for the RC unit in the middle, and as low as possible (This also makes easier the changing of the batteries)

The key to make the drivetrain strong, was to increase torque as close to the wheels as possible. I started building the truck from the front axle and suspension, which took a lot of time inspite of the fact, that i "stole it" from my Hummer; i had to improve it. On the following picture you can see 3 1:3 gearing in a compact house, and the first attempt for the suspension (which was a 4 link one).

As i finished the first prototype i realized, these links (and pins) are simply too weak to bear the forces from all directions during offroad, so I came up with a bit strange suspension system, which meets my requirements:

Three "Technic Suspension Steering Link 6L" are used. 2 connects with a pin to the axle, and "fixed" horizontally on the other end. The third one connects to another steering link, the other end of it can freely slide on the axle.

One motor drives one side, which helps the motors to work in balance. I mean eg. when the truck meets an obstacle the motors are loaded almost equally, which imo increases overall perfomace. While turning a little speed difference is also possible beetween the two sides, but i agree, it’s rather a truck with closed differential than with open:)...

OK these are just words and pictures, let’s see it working :)

Final ratio is: 1:45, and the outer output of the RC motors is used.

(The sticker on the top comes from the first Malug TT competition, I left it on that panel:))

Abnormal MOD:
I wondered, what happens if i double the amount of motors used for driving, so i simply added 1-1 motors for the sides and decreased the final ratio to 1:15, and i used the inner (faster) output of the motors. I also considered that I use 66 gears, 20 UJ-s, and if i play with it for long hours, i won’t have the gears and UJ-s to change them; so i put some greasing on it. The truck became heavyer : 3250 grams.

Fight against 3 chairs and a little snow action (note that 1 chair is on a smoother surface)


I’m not sure if i have used always the correct expressions, please feel free to correct, and of course to ask and leave comments:).

View online : Brickshelf: TT-4-Raba-H22

Forum posts

  • I also considered that I use 66 gears, 20 UJ-s, and if i play with it for long hours, i won’t have the gears and UJ-s to change them; so i put some greasing on it.

    You loose gears after playing with truck for long hours?

    Anyway great truck, with a very unique and powerfull driveline!

    • Thank you!

      No, I don’t loose any gears by the time. I wanted to mean, that the gears worn out much faster, if there is no greasing. Outside, mainly the lower gears (in position) easily get dirty, (eg. when the wheels spin on the soil) which also make them worn out pretty fast. Then these gears have to be replaced, to get back the original efficiency/performance (so in that way, yes, I loose them:)).

      Anyway I think everybody meets these problems:)

      I said that I don’t loose gears, but I have to admit, that the about 4 of the 8 8z gears (in the hub) are deformed on 1-2 teeth, but they are still useable (even though I used the 8z gears that have the thickest teeth). That’s one of the weakpoints, but it’s not really significant in overall.

    • Hey are you jordan from greece?

      Kind Regards,

      View online : online casino

    • Hello!
      Sorry, im not Jordan from Greece; im from Hungary:)

  • Nice truck.

    Reduce the torque on bevel gear and Increase it as near as possible to the wheel (spur gear) is the good thing to built strong drivetrain ;)

    • Thank you as well!:)

      Yes, you’re right, spur gears are better, but we always have to make compromises. At the front axle I wanted to minimize the distance between the turning center and the wheel, which resulted in this 12:36 gearing. No space left for another spur gear.

      On the rear, its different, I should be able to make some space for it (or more exactly, to change one of the bevel gears to spur gear); that’s one of the thing I want to improve on it.

  • There’s still only one short vid about my Rába (with 4 motors) at the last Malug TT competition, but maybe worth to see:)

    View online :