After built always Truck Trials 4x4 for some reasons, a few months ago I decided to build my first 8x8 for a local competition in Madrid.
I don't like Tatra system, that system works fine but I prefer to use rigid axles. For build the truck I have reused the axles of my previous trial (Little Boy MK2).
Also I have reused the suspension system too, but adding some more rotation points.
As I have reused so many things from my previous trial, only took me 4 days to build it completely.
- 4 XL motors for drive(one per axle)
- 1 M motor for steering
- 1 M motor to move de fake engine
- 2 IR Recievers
The gear ratio in all axles is the same, 9:1(3:1 x 3:1)
Total weight with two lithium batteries is 2.4 kg, and with a 9v battery box 2.45.
The truck is divided in 3 parts: the front axles (with steering), the rear axles and the chassis.
As I said before, the axes are derived from a version of my previous trial, I only changed the position of the motor to top to get closer to each axles.
The axles have ackermann sterring between them. I have done that moving a little the steering arm of the second axle, so it turns a little less than the first axle, getting smaller turning circle, both axle are moved by a single M motor M.
Except by the steering arm both axles are identical.
The two axles joint form a independent suspension system.
They are a derivative of another trial axles. Again part of the gear ratio has moved inside the wheel.
The suspension system is exactly like the front axles.
It is a large rigid structure of 60 studs long without much complication, but it contains all the elements to keep everything in place.
At the top is the cab of the truck, the batteries (in the picture has 2 lithium batteries but with only a normal 9v battery box works well) and receivers.
Also includes a fake V10 engine and a motor M to move it.
On the other side, the two support that stick out under the cab are the points of union with the front axles, are rigidly attached to the chassis.
In the back are the supports for the rear axles. But in this case also contain an extra pivot point for the suspension, along to the longitudinal truck axle. With all these points of turning, the truck can be twisted like a "Lizard".
In the central part appears a third support. It's function is some extrange, when the truck is climbing a steep ramp or making a lot of strength to overcome an obstacle, This system prevents than the first and the third axles stand up, pushed by the second and fourth respectively. As a result you lose a bit of suspension travel but you win grip to go through very steep ramps.
Now a video with all capabilities in action:
You can see some more videos with the truck participating in an electricbricks competition here(I won!!):