4wd Expert Builder

Simple 4 Wheel Drive With Steering

Front View of Chassis Starting in the mid-80's, I began struggling to build a wheel axle that was driven as well as steered. The model you seen to the left is the first design I developed. This came after countless revisions and long hours of building, not to mention years of frustration.

Top View of Chassis This is essentially Expert Builder style as the parts used are all old (found in the LEGO sets of the early 80's). I only wish LEGO had produced a set using this idea. I would have certainly bought it!

View from Underneath I came across the idea unexpectantly. I had just given up trying to build a driven and steerable axle. I was building a truck chassis one day and was going to use the independent rear suspension from the 8860 Auto Chassis.
After building the rear suspension, I set it down on my desk for a moment. Inadvertently, I had rotated it 90 degrees about the wheel axis when I put it on the desk. When I looked back at it, WHAM! The idea hit me so hard I began laughing.
See a catalog scan of the 8860 chassis at this page on www.brickshelf.com.
There it was, staring me in the face- the idea I had been trying to develop for quite a long time. All it needed was a connection to the main frame of the chassis and a set of steering control arms.

Top View of Front Axle The steering connection was the most difficult to develop. The link (with rack gears) connecting the two sides provides the strength to connect the two wheels in parallel and to keep them from pulling open when the model moves forward.
The steering link is kind of "free-floating" as there is no support structure underneath it. It is fixed by friction pins at the ends and spans the distance unsupported. The 8t pinion gear drives the rack.
The picture below shows a good shot of the steering link from underneath. You will see that it is a bulky-looking thing made of 1x and 2x plates with the rack gears on top.

Front view from Underneath The front axle is 18 brick units wide. When 24x43 tires are put on, the inside-to-inside distance between the tires is just over 16 brick units wide. There is an old style Technic differential connected to 2 u-joints. The steering pivot point is in-line with the joint of the u-joint.

Another Front view from Underneath The ground clearance is pretty low, as there is a Technic beam running underneath the u-joint. However, you can still use 24x43 or 20x30 tires (the old style Technic tires).

View of Front Axle From Behind ADVANTAGES:
strong, simple, uses common parts
DISADVANTAGES:
low ground clearance, steering pivot point is a far distance from wheel contact point, no shocks

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Front View of Chassis	Starting in the mid-80's, I began struggling to build a wheel axle that was driven as well as steered. The model you seen to the left is the first design I developed. This came after countless revisions and long hours of building, not to mention years of frustration.
Top View of Chassis	This is essentially Expert Builder style as the parts used are all old (found in the LEGO sets of the early 80's). I only wish LEGO had produced a set using this idea. I would have certainly bought it!
View from Underneath	I came across the idea unexpectantly. I had just given up trying to build a driven and steerable axle. I was building a truck chassis one day and was going to use the independent rear suspension from the 8860 Auto Chassis. After building the rear suspension, I set it down on my desk for a moment. Inadvertently, I had rotated it 90 degrees about the wheel axis when I put it on the desk. When I looked back at it, WHAM! The idea hit me so hard I began laughing. See a catalog scan of the 8860 chassis at this page on www.brickshelf.com. There it was, staring me in the face- the idea I had been trying to develop for quite a long time. All it needed was a connection to the main frame of the chassis and a set of steering control arms.
Top View of Front Axle	The steering connection was the most difficult to develop. The link (with rack gears) connecting the two sides provides the strength to connect the two wheels in parallel and to keep them from pulling open when the model moves forward. The steering link is kind of "free-floating" as there is no support structure underneath it. It is fixed by friction pins at the ends and spans the distance unsupported. The 8t pinion gear drives the rack. The picture below shows a good shot of the steering link from underneath. You will see that it is a bulky-looking thing made of 1x and 2x plates with the rack gears on top.
Front view from Underneath	The front axle is 18 brick units wide. When 24x43 tires are put on, the inside-to-inside distance between the tires is just over 16 brick units wide. There is an old style Technic differential connected to 2 u-joints. The steering pivot point is in-line with the joint of the u-joint.
Another Front view from Underneath	The ground clearance is pretty low, as there is a Technic beam running underneath the u-joint. However, you can still use 24x43 or 20x30 tires (the old style Technic tires).
View of Front Axle From Behind	ADVANTAGES: strong, simple, uses common parts DISADVANTAGES: low ground clearance, steering pivot point is a far distance from wheel contact point, no shocks