Original Year	2000
# of pieces	979
Categories	Other: Other
Dimensions	45(L)x25(W)x17(H) (without sled)
Features	Steering, 5 engines, motor, weight transfer sled
Other Views

8457 Power Puller

Click the image to download the LDraw file of this model.
Model by Owen Dive

Power Pulling or Tractor Pulling is a motorsport in which massive vehicles loosely based on tractors compete to pull a heavy sled as far as possible. The tractor is typically just a welded tube chassis with massive tires at the back, tiny tires at the front, and as many engines as possible. It turns out that Technic actually sponsored such a vehicle at the time, and this set is a scale model of the real thing. The set came with a VHS tape containing some race footage of the real Technic Power Puller. No other Technic set has ever come with a video tape!

The model does a nice job of capturing the major features of the real thing. To this day, these massive tires are known to fans as "Power Puller tires" even though they later appeared in another very different model. The tractor can be configured with either 5 V-4 engines, 3 V-6 engines, or 2 V-8 engines. The 5 engine configuration is most like the real thing, although they are actually V-8's. With 20 engine cylinders, this set holds the record for the most ever. The set is motorized and can actually be used to pull a sled which operates much like the real thing.

The instructions include sections describing how to enhance the model with various "Power Packs" available as Supplemental Sets this year. An additional motor could be added for more power, or a speed computer could be added. The speed computer had different functions depending on where it was installed. If installed to an engine crankshaft it served as a tachometer. If installed to the rear axle, it could measure either speed or distance based on the diameter of the tire. It also had a stopwatch feature. All of these are quite useful functions to have for a racing vehicle.

There has never been another model which is anything like this one which is why it is in the "Other" category. There is nothing to compare it to! It is a huge, fun set with rare parts and a totally unique subject. I highly recommend it.

Features

Steering

Although this model has steerable front wheels, the steering is almost totally useless. Fortunately, real power pullers also have almost useless steering so it is quite accurate! The steering is driven from the driver's position by a cam connected to a very long flex cable. At the front end, the flex cable connects to an engine crankshaft and another cam to produce small lateral motion. The steering tie rods are short flex cables.

As you can see in the animation, the steering wheel doesn't even noticeably turn when the wheels are steering. This is because the flex cable tends to buckle instead of transmitting motion.

Click for an animation of the steering in motion.

Engines

This set has 3 different engine configurations which can be easily swapped.

5x V-4 for a total of 20 cylinders
3x V-6 for a total of 18 cylinders
2x V-8 for a total of 16 cylinders

The engine assemblies are modular and can be easily attached to the chassis with two red pins. The set has only enough parts to make one configuration at a time.

Each engine has transparent cylinder blocks and yellow pistons. There is a chain mounted to the front of each block meant to represent a belt driven supercharger, but the chains don't actually connect to anything.

As can be seen in the computer image, the laterally mounted engines are all geared at the same ratio, but the upper engine does not turn at the same speed. This would not be a very good idea in real life but causes no problems here.

Click for an animation of the engines in motion.

Motor

A 9V motor is attached behind the solid rear axle and connected to the drivetrain with a very clever system. In the computer image, the solid axle is shown in blue. The motor is directly connected to the engine module, but is only connected to the axle through the red gear which is mounted on a pendular arm. The result of this is that when the motor is driven one direction the red gear just slips and only the engines are driven. When the motor is driven in the other direction, then the axle is engaged and the tractor drives forward. It can never drive in reverse. This makes it easy to turn the engines on and watch them go.

The model contains instructions for attaching an additional motor in parallel which results in enough power to actually lift the front wheels off the ground like a real power puller.

Weight Transfer Sled

A real weight transfer sled works by starting a heavy weight over the rear axles and then moving it forward by gearing it to the wheels. As it moves forward, it causes a blade or pan to dig into the ground and increase resistance.

The model version works in a reasonably similar way. The battery box is used as a weight and it starts at the back. A set of gears connected to a bungee cord is used to pull the weight forward. Instead of digging into the ground, a second fixed bungee is used to resist motion and becomes tighter the further forward the weight is slid.

Click for an animation of the sled in motion.

Dude

This set comes with a unique Techic figure wearing a yellow jumpsuit and helmet just like the driver of the real thing. This was the last set to come with a Technic figure.

Wheels and Tires

This set has a wide variety of wheels and tires. The sled uses two sizes of balloon tires. The tractor uses silver Model Team wheels at the front. However, the obvious star of the set is the Power Puller wheels at the back. The wheels are common to the 8458 Silver Champion, but the tires are new. These huge balloon tires are decorated with "Technic Power". Although they later came in one other set, the decoration never appeared again. These tires are very soft and "grippy" and deform significantly under torque like real power puller tires.

Other Views

Side View

Top View

Front View

Back View

Computer Render

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