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Extreme Offraader V4

Thursday 23 August 2012, by Buildingspree12

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Technical data

Scale (wheels used)
Width 25 studs
Total Weight 1200 grams
Transmission 4x4
Motorization 2 motor(s) - NXT

working fake motor
Steering motor

with steering wheel
Onboard Battery Box NXT

After the success of my Extreme Offroader V3 I started on my next Offroader. I decided my next offroader would have full suspension. At the time I did not own enough shock absorbers for a full suspension vehicle so, I purchased ten new medium hardness shock absorbers. I started with a truck that had for shocks per axle, eight shocks in all, four in the front, four in the back. As I built I relised that the chassis were not strong enough to handle the stiffness of the shock absorbers so I took it apart and started again. I used two shocks per axle, four shocks in all, two in the front two in the back. As I conducted driving tests I noticed that when I drove it up hill, it would tip to one side and result in a role over. The problem causing this had to do with the shocks. The problem being very common with pendulum suspension trucks, was easy to fix just by doubling up the shock absorbers on each wheel. To my relief the rebuilt chassis were able deal with the doubled up shock absorbers.

As I was reading on the Brick Truck Trail web site I came across a page that contained tips and tricks for trail truck builders. This article helped me decide on the final gear ratio. One of the tips was “speed dose matter”. You must be thinking “how to dose speed matter in a trail truck”? “shouldn’t the truck be all torque no speed”? Well that is what most people think but let’s say your truck is going up a 50 degree incline, and as you go up your wheels tend to slip as it moves up the slope. If your wheels are not spinning fast enough your truck slides down. So the speed of your wheels must be greater than the sliding back motion caused by gravity. If you gear your truck down to much your wheel speed will be less than the sliding motion from gravity and your truck will be unable to climb the slopes it comes across in a truck trail competition. Your final ratio should be some speed but mostly torque. The correct ratio varies depending on the size and weight of the vehicle. Try different ratios to get the best performance out of your truck. There are many types of suspension to choose from such as independent, floating axle and pendulum. I chose pendulum suspension because it offers lots of flexibility. Full suspension was a challenge and it took me a few hours to get it right. This Truck also turned out to be very small! Only 25 studs wide, and about 35 studs long.

This is my very first full suspension truck and I am very pleased with how it turned out. This truck was a challenge and a very fun build. I had problems with the gears but I soon took care of them by adding bracings. I recently purchased the Lego Technic Unimog. Be expecting new models soon.

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