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Original Year
 1983
# of pieces
 246
Categories
 Cars and Trucks:  Race Cars
Dimensions
 44(L)x14(W)x12(H)
Features
 Steering, Inline 2 cylinder engine,
Differential
Other Views

8847 Dragster
iso revolve
Click the image to download the LDraw file of this model.
Model by Jason Mantor
Set 8847 was released in 1983 and was available only in the USA.  Do they have top fuel drag racing in Europe?  Maybe not, which would explain the discrepancy.  This model features rack and pinion steering, a 2 cylinder reciprocating engine, and a rear differential, as well as a host of nice looking aesthetic features including a large rear spoiler.

This set was the first to use the pulleys as wheels, and the first to use the new tire treads for them.  This is also the first occurrence of white beams, of which there were four 16L in this set.  There are two 2L light gray beams here as well.  Despite light gray being a common Technic color, there had never been light gray beams before.  Even as of 1983, the light gray and white beams came only in one size each.

This is the only drag racer ever released by LEGO® Technic, and is therefore quite unique.  Because of this, and because it was only released in the USA, this is one of the most difficult models to find and purchase on the secondary market.  It was a very happy day when I finally found mine!

Features
Steering
The front wheels can be steered using a pulley wheel in the driver's position.  The wheel drives a set of 16 tooth spur gears.  The second axle drives a rack via a pair of 8 tooth pinion gears.   The steering drive axle is very long and uses a pair of toothed connectors as an end splice. The steering mechanism itself uses control arms and toothed links.

Later versions of this model would change the splice to use a universal joint, and change the 2L beam at the front to a 4L beam.  I have no idea why they did this since the original design works perfectly fine.
 steering
Click for an animation of the steering in motion.
Engine
The two cylinder engine uses the offset axle holes of the 24 tooth gears to make a crankshaft.  Connectors placed end to end and clocked 90 degrees form rods which connect to a pair of specialized 2x2 square pistons.  The "cylinders" are actually square.

The engine also has a number of aesthetic features such as cooling fins (suggesting this engine is air cooled).  There seem to be a conflicting set of exhaust manifolds.  One set emerge almost vertically from a set of hinges, suggesting straight pipes like a real dragster.  The are 8 of them; odd for a 2 cylinder! Another series of 6 (?) curved beams on the bottom appear to be a set of headers.  I guess this thing makes a lot of exhaust.

A chain on the crankshaft also drives an overhead shaft.  This shaft is not connected to anything, but probably represents a cam shaft, though big dragster engines never have overhead cams.

Racing enthusiasts will no doubt add a blower to the engine immediately.
 lift    engine
Click for an animation of the engine in motion.
Differential
The rear axle uses a differential gear.  It incorporates a built in 28 tooth ring gear which can work either as a bevel or a spur, similar to the 24 tooth crown gear.  It is made to house 3 of the new 14 tooth bevel gears.  One is on each axle, and one planet gear in the middle allows the axles to turn at different rates.

 diff
Click for an animation of the differential in motion.

Wheels and Tires
This set uses two of the foam 20x30 tires and wheels on the rear.  The front uses a set of pulleys with the new pulley tires over them.

Steam rollers on the back, pizza cutters on the front.
 Wheels    Wheels
  

Other Views
Side View
side view
 Top View
top view
Back View
back view
Front View
front view
Computer Render
render

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