Pictorial Review: 8421 Mobile Crane

[Lost_In_Noise]

8421 Mobile crane was released as the ultimate Technic flagship in 2005, and is the second-most parts heavy set only surpassed by 8110 Unimog U400. It features 4 extending outriggers, six-wheel steering, and a fake 6-cylinder engine. An electric RC motor operates the crane winch and expansion, and two pneumatic cylinders lifts the boom.

According to Brickset, this baby was 150$ on release, and I gave about 180$ for mine without box. The average used price on BrickLink is 200$. The stickers on mine was worn, but they don't make a big difference when building this set. Yellow is still yellow.

1884 pieces makes for a solid build, stretched over two instruction books, the first one for the chassis, and the second for the crane. Rather than having them named book #1 and #2, they have greyed out the part that's not present in each book. I have not seen this in any other set, and it indicates that you could build whichever module you want first. The instructions are a whooping 212 pages long, containing 126 steps. That makes for an average parts-per-step ratio of 15. In comparison, the 8110 has 618 steps for its 2048 pieces, giving a ratio of 3 pieces

per step. I guess the kids have gotten dumber with time.

I consider myself an experienced Technic builder, but this behemoth took me a solid day to complete. That of course includes taking pictures and so forth, but still... It also took me 4 hours to disassemble for this review:S

Let's take a look at the parts...

The special parts, containing motor, battery box, pneumatic cylinders , pump and switch. There is also some strings with 1 stud on each end, which will be used to extend the boom.

The RC motor is able to drive two axles at the same time.

Okay, let's start building, the chassis is first, comprised of liftarms and pins.

This is the chassis at step 8.

And this at step 14.

The other side. No suprises here.

A little gear rack for the back axle.

Held in place by another double-bent liftarm.

Next is making some wheelbases. These three are going to be placed in turn later on. Four out of five axles are steered in this model.

These gears will control steering and outriggers from the back of the truck.

The middle axle holds the differential which will power the engine. This is the only mobile crane I know of which have a differential.

Here it is in place:

Another gear rack is made to extend the driveshaft and steering rack.

Placed here along with the second steered axle.

two 8T gears are placed to allign the second and fourth axle.

Two double-bent liftarms keeps the axle in place.

Another gear rack to extend the steering to the first axle.

To lock the steering axle in place, this contraption is made.

Two 15L beams is the base for the drivers cabin.

More beams are added to strenghten the body.

These knobwheels are later connected to the outriggers.

The axles for the outriggers are extended to the front side of the truck.

These four are the attaching pins for the Crane superstructure.

This cage will hold the turntable in place.

Next is the outriggers- Two sets are made and placed in front and back.

First outrigger placed. You can see the yellow 3L pins with stop bush that keeps it in place.

The front fender is placed.

Rear set of outriggers are placed, along with an extension of the HOG axle. This is the final lenght of the crane truck.

Rear controls for outriggers and steering placed, here you can see how wide the truck is.

The engine is a standard Technic 6-cylinder V.

It's connected to the driveshaft differential via a 16T clutch gear.

Next is the cocpit.

The colour separation in the instructions are excellent. I was never in doubt during the build as of which color to use where (LBG/DBG).

Nice comfy seats.

Next is the sides, which do not open in this model.

The roof is mainly made of axles and liftarms.

Placed here along with some decorational "Vehicle Grilles".

Finished windshield and lights.

The cabin added to superstructure along with the front lights.

Some decorational bricks along the sides before Wheels are added.

Finished the base, it's quite big.

The crane base requires some reinforcement to cope with all the weight of the crane itself. Some thin liftarms on each side ensures that it will not break.

The changeover catch is connected to a 20T bevel gear.

The driving ring sits on an axle with a 24T, a 16T clutch and a 12T DB gear.

The DGB 5.5L axle with a bevel gear meshes with the 20T bevel to control the changeover catch.

To elevate the boom, two pneumatic cylinders are attached, giving a total stroke of 8 studs. The "Pneumatic Cylinder Bracket" is only seen in this set and the motorized bulldozer, giving an average BL price of 14$ each. Two pneumatic hoses are joined to simultaneously apply pressure to both.

A turntable is placed underneath, and locked with a 15L beam.

The pneumatic switch is placed on the side of the base.

The winch axle has a clutch gear on it to prevent the motor from stalling. It also prevents this crane from lifting anything weighing more than a few grams.

The lower handle controls the changeover catch.

Some worn stickers show what the levers are for.

The motor is placed on the side of the crane.

Some reinforcing beams and bricks.

The base of the turntable consists of beams and "Pin Connector Perpendicular 3L with 4 Pins", and is locked by some 15L beams.

The pneumatic cylinder inlet is fixed on the pump, and then on the superstructure.

The crane has its own cabin.

The primary boom is next.

A "Black Bionicle Bohrok Shoulder" is used to keep the top and bottom from falling apart.

A clutch gear connected to the worm screw prohibits the boom from extending too far.

Here is the gear setup for the boom extension. Note the 32L axle.

Some liftarms ties the back end together.

And then some bricks in the front.

Same setup on the other side. Note the 8T gear above the worm screw.

This rack fixes the 32L axle in place, and a thin triangle liftarm secures the end of the boom.

Two strings with studs are attached on the far side of the secondary boom.

The crane head has two "Black Wheel Spoked 2 x 2 with Pin Hole"s, which will guide the winch line.

Head complete. You can see how the winch line will go through the two perpendicular axle and pin connectors.

The seconday boom is next.

The tertiary boom is placed inside the secondary, and enclosed by another set of technic bricks.

The gear rack for the secondary boom is added.

Seconddary boom is then inserted into the primary, and the studded string is attached to two "Plate 1 x 5 with Smooth Ends, 4 Studs and Center Axle Hole"s.

Two "Black Plate, Modified 2 x 2 with Pin Hole" are placed, and fastened with two yellow 9 beams to keep the boom from prying apart under pressure.

Crane finished, now all that remains is the hook.

The battery box serves as a counterweight in this set.

Mounting the crane on the base completes the model.

Comparison with 8053, 8446, 8067.

I think this is a great model, with lots of functions and parts. At the current price @ BrickLink it's not exactly a bargain, but a considerable better model then the 8053 Mobile Crane. The pneumatic lifting of the boom is original, but doesn't work as well as you'd suspect, as the air leaks lowers the boom over the cause of a few minutes. At least on mine. The 6-wheel steering is really smooth for the size of the model, it almost seems weightless. The inclusion of a fake engine is a nice plus. I'll give it an overall score of 8.5/10.

Thanks for reading/watching pics. If you liked the review, give me some feedback, otherwise, vote on the poll.

Bigger pics @ Brickshelf

Edited September 1, 2012 by Lost_In_Noise

[Alasdair Ryan]

Mine is on my ''breaking table''.

It's a great set and one of the first with a 3 piece boom.

[Rijkvv]

Thanks for the review!

I voted Very Good. It's a great set, and one of the few sets of the last decade that contained some studded parts. Which, in my opinion, is a big advantage. However, despite it being much bigger than 8460, I actually prefer the older crane. The 8480 has better outriggers, but also a gear-driven turntable. For it's size, I think the manual turning was a disappointment.

So, everything said, I think the 8421 is not as good as 8460, but still a great set.

[Lost_In_Noise]

Thanks for the review!

I voted Very Good. It's a great set, and one of the few sets of the last decade that contained some studded parts. Which, in my opinion, is a big advantage. However, despite it being much bigger than 8460, I actually prefer the older crane. The 8480 has better outriggers, but also a gear-driven turntable. For it's size, I think the manual turning was a disappointment.

So, everything said, I think the 8421 is not as good as 8460, but still a great set.

I haven't recieved the 8460 yet, but I expect it to be better than this. It was probably re-released 2 times for a reason.

[SheepEater]

Here, I always use a standard 24T gear instead; this makes the crane able to lift much heavier weight. In addition, I add in pneumatic tubes to close off the circuit (the set already comes with an extra t-piece), to smoothen the descent of the crane arm.

[Lost_In_Noise]

*snip*

Here, I always use a standard 24T gear instead; this makes the crane able to lift much heavier weight. In addition, I add in pneumatic tubes to close off the circuit (the set already comes with an extra t-piece), to smoothen the descent of the crane arm.

I do this too, but for the sake of an exact review, I left it in.

[kieran]

Great Crane, the only issue I have is the string is too thick and keeps catch when wound up. I have been trying other strings to get a better fit. I see you used the original one, is that all the time or just for the review?

[Matt The Tuba Guy]

I will always have fond memories of this set, it was my first flagship, and it was AWESOME! (still is)

In a lot of ways, this is actually kind of similar to the Unimog. it has a body and two attachments (A and B models), it has pneumatics and a motor, and it looks REALLY good.

Definitely one of the best ever Technic sets.

[Lost_In_Noise]

Great Crane, the only issue I have is the string is too thick and keeps catch when wound up. I have been trying other strings to get a better fit. I see you used the original one, is that all the time or just for the review?

I've not replaced the string. If I apply a lot of force to the string, it winds up well enough. I saw another thread for buying bead string to use with lego contraptions, but I didn't buy any. Maybe in the future I will change the string on all my sets.

[sama]

Very, very good and thorough. 8421 needs to be considered to be re-released.

[Jetro]

Mine is on my ''breaking table''.

Is that the one you throw it off when to disassemble sets?

Mina actually accidentally fell out of the attic. It landed 3m down and was still mostly OK: a very sturdy construction!

[Alasdair Ryan]

Is that the one you throw it off when to disassemble sets?

Yeb......

Jurgens Zorex220 is in there too......

[skylinedan]

I guess thats one way to store your LEGO,s, LOL. Mine are a bit more organized, bad part is I spend as much time taking them apart and putting the parts way as I do building them. The addvantage is next time I build something al the parts are right there ready to be used.

Dan

[Alasdair Ryan]

I guess thats one way to store your LEGO,s, LOL. Mine are a bit more organized, bad part is I spend as much time taking them apart and putting the parts way as I do building them. The addvantage is next time I build something al the parts are right there ready to be used.

Dan

That's just the models I have made up that I am slowly taking apart as I need parts .I have many parts sorted into compartment's ........

[Lost_In_Noise]

UPDATE: I made a small montage of the set using Technic figs. This sure has lots of playing features.

It's enough to keep 14 Technic figs occupied. The engine has broken down so they can't lower the boom

[DrJB]

first time I see so many technic figs ... and I only have 2 (power puller and 8450)

[dougstar]

this is a top review!

[davidmull]

And this thread is 3 years old!

[Lost_In_Noise]

I'm still here:)

[zux]

Sorry for bumping an old topic, I thought it would be better to ask here, rather than create new topic.

8421 is indeed a cool model, but has a cracking sticker issue. I would love to get some re-created. Buying overpriced original one is not an option - it would crack and peel again. I'm not looking to acquire aftermarket sticker as well (not worth). So I wonder if anyone has a better sticker scan than the one available on BrickOwl?

[gvo25]

I voted very good, It's the set that brought me out of my 'dark ages'. I only dissassembled it again when the 42009 came out.

[zux]

8421 is indeed a cool model, but has a cracking sticker issue. I would love to get some re-created. Buying overpriced original one is not an option - it would crack and peel again. I'm not looking to acquire aftermarket sticker as well (not worth). So I wonder if anyone has a better sticker scan than the one available on BrickOwl?

Answering my own question, just in case someone would be looking for same in the future. The best (and only) scanned stickers for 8421 set I could find are hosted here (at the the very bottom).