8455 Backhoe was released in 2003, contains 704 pieces, and features steering via HOG inline 3-cylinder engine driven by rear
differential, and a lot of pneumatics. A total of 10 cylinders powers the outriggers, lifting/tilting of the front bucket, and operation of the rear bucket.
The sets is considered one of the best by AFOLs, and I agree for the most part. More on pros and cons in the conclusion of this review.
The average Bricklink price is about 150 Euros, making it one of the most expensive Technic sets to buy second-hand. I paid about 130 Euro for mine, and it arrived in pristine condition with near-mint instructions and a nice box. Original retail was 80 Euros.
The box itself is nothing too special, the front has a "Pneumatic" logo on it.
The back shows the alternate model, a Wheel Loader, along with the functions of the backhoe.
The set rests on a pair of 81,6 x 38R tires and some 56 x 30's.
Some 9L links helps with the pushrod steering.
The Big Digger bucket was last seen in last years 8069, and 8043
A 4 x 4 x 9 Digger Bucket is used for the back scoop, same as the 8069.
A total of 7 pneumatic switches are present in this set, along with 2 pumps and 10 cylinders.
13 T-pieces connects the maze of pneumatic tubing, which is 601 studs long.
Not a lot of gears, but that really doesn't matter much in this set. An Old style differential drives the engine from the rear axle.
Main model: Backhoe
The build starts with the rear end of the chassis. The pneumatic cylinders for the outriggers are placed on the sides.
The outriggers "feet" are made of thin triangle liftarms. They are attached with frictionless pins, and capable of lifting the finished
Next is the pushrod steering mechanism. The front wheels aren't driven, but attached with frictionless pins.
The rear boom is pivoted by a pneumatic cylinder, hinged on the vertical axle.
The cylinders for retracting/extending the outriggers are connected to a single inlet. This makes them move simultaneously.
The first switch controls the boom's pivot.
The second raises and lowers the first section.
A set of knobwheels and a 12T DB gear transfers motion from the HOG axle to the steering setup.
The last switch in the back controls the rear boom's luffing/scooping mechanism. A set of 40cm tubes runs from it.
Here you can see how the pushrod steering works. The knobwheel is connected to a set of 3L thin liftarms with a "Pin with
The rear wheelarch comes into place before the tubing for the pumps is fitted.
This setup directs airflow from the pumps to the pneumatic switches. The two pumps powers all the functions.
Here it is in place. The four black long hoses are for the rear boom operation.
The pneumatic pumps are a part of the cocpits frame, making it convenient to operate the backhoe. Two pumps providing input makes the machine operate very fast.
The top switch controls the outriggers. All switches has a toggle joint attached which makes them easier to operate.
The differential sits a bit off-center, another pneumatic switch controls the scoop elevation.
The inline 3-cylinder engine uses the Trans-Clear cylinders.
These black hoses will operate the front bucket.
This final knobwheel is the last link in the steering chain.
Here you can see the three knobwheels pushing the links in opposite directions for the steering.
The final pneumatic switch is placed to control the front boom lift.
The cabin is finished. Note that the beam with lights is not connected to the sides.
The right section of the front boom is made of liftarms, and lifted by a pneumatic cylinder. The second cylinder tilts the bucket.
The mechanism for tilting is hinged with a crankshaft, which offsets the motion by a half stud.
Now the front is finished, all that's missing is the scoop.
And wheels, before the rear boom.
The hoses are carefully routed with perpendicular axle connectors.
Now the pneumatic circuit is complete, all that's left is adding the scoop.
The pneumatic system causes these features to be synchronized, so you can lower the bucket while keeping it level to the ground.
Rear arm, and bucket movement. The rear arm swings approx. 165 degrees.
The outriggers are quite powerful, and certainly capable of lifting the rear off the ground about 2 studs.
Secondary model: Wheel loader
This model starts with the drivetrain, which is similar to the main model. The engine setup is also the same; a straight-three.
The steering is the same as the main model.
A gear rack leads to the HOG.
The back end, which usually has a counterweight, is made as a separate element, before it is placed on the chassis.
The wheelhubs are made the same way as the main model, only situated in the back. Front loaders are unable to use the front wheels for turning, since they suffer from too much load for the servos.
Some panels finishes the rear.
A view from the front. Note the yellow bent liftarms in the back. Those acts as handlers for the pneumatic pumps.
The boom support also has the front axle with a differential in it. The engine is quite fast, the final drive ratio with this
configuration totals to 1:5,4. (Thanks Sariel)
The front wheelhubs are made mostly the same way as the main model. They are the last mechanical part to be added before the pneumatic galore starts again.
Ah, this reminds me of 8868, sheer pneumatic madness:-)
The cocpit is made as two separate sides.
The boom is made a a separate unit.
Boom and bucket placed. routing the hoses takes about 5 minutes:S
Placing the final switches finishes the model.
1) raising/lowering boom is notably slower than the main model, since only one cylinder is used per function. Also, the the pumps seems to strain more.
2) bucket tilt
The buckets tilt to an extreme this way, dispersing of any contents.
3) boom extension
4) boom extension 2
Of course, all functions can be run at the same time, since they use different cylinders. You can raise, extend and tilt in one continous motion.
It takes roughly five pushes on the pumps to go from the two extremes.
Forget the 8880, forget the 8460, forget the Unimog! This is as good as it gets. The way it looks and works is unprecedented in any other set I've got my hands on. Eight different functions with just 700 pieces is a great achievement by the Technic team. Don't let the hefty price scary you off. If you can afford it, quickly get one and stop reading right now.
As always, big pictures will be made public @BrickShelf. Any questions or comments are very welcome. Thanks for reading!
Edited by Lost_In_Noise, 17 November 2012 - 10:03 PM.