8421 Mobile Crane

[technicfan]

I have recently purchased a 2nd hand 8421 Mobile Crane for a good price with the box which is very hard to get in New Zealand and was wondering if anyone had done a review on it?. A few sites have said that this is the best technic set ever made, what makes this set so good. I have got the 8053 and 8431 crane trucks but what sets this apart from those ones. Also anyone had any problems with it?.

[davidmull]

I'm not sure about reviews but it is a great set,I bought it in December gone and it was misb , I still built it tho and it's a great set but to me not the best,

I would still have to put 8455 before it :)

[Technic Gearhead]

I'm looking forward to some replies on this as well. I bought one MISB this year but haven't built it yet. It wasn't cheap but that's how it goes when you miss out the first time around. It just seemed like too relevant of a set to ignore and it felt great to get one before they are gone.

[Siegfried]

I've got a half finished review... that is I've take some build photos. I can post them if you want.

It's a cool set. The crane function is weak, the arm is too heavy for the pneumatics, but it's still very cool.

[Technic Gearhead]

The crane function is weak, the arm is too heavy for the pneumatics, but it's still very cool.

Hmmm... Might have to retrofit a mechanical linear actuator there. J/k - don't shoot!

Edited February 29, 2012 by Technic Gearhead

[Siegfried]

Hmmm... Might have to retrofit a mechanical linear actuator there. J/k - don't shoot!

To be honest *ducks behind couch* I think this set could be improved with one. I love pneumatics in things like the 8455 Backhoe, but they aren't as good at holding weight without constant pressure.

I would still have to put 8455 before it :)

Yes. This has to be the best Technic set ever. The function density is just amazing.

[Technic Gearhead]

To be honest *ducks behind couch* I think this set could be improved with one. I love pneumatics in things like the 8455 Backhoe, but they aren't as good at holding weight without constant pressure.

Yes. This has to be the best Technic set ever. The function density is just amazing.

Maybe I will experiment with it at some point on the 8421. I already plan to update it with the newer style PF components and some smooth panels here are there. I'll build it to spec the first time around though.

That's also good to know on the 8455 since I'm about to pay dearly for one of those.

Edited February 29, 2012 by Technic Gearhead

[Splat]

There are 16 reviews of various quality over at Brickset (link), and overall it has been rated 4.8 out of 5.

I received this set as a birthday present when it first came out (I was still in my dark ages at the time). When it was released, it was the largest Technic set (# of pieces), and is still the second largest Technic set today (only the 8110 Unimog has more pieces). It has pneumatics, a powerful RC motor and battery box, differential, 2 x 24 tooth clutch gears, worm gears, driving ring and changeover catch, and a total of 53 various gears (if I counted correctly). It has 6 wheel steering which is nice and smooth, the boom has three sections, there is a V6 engine, stabilisers (which don't actually lift the crane off the ground, but do lock in place), the chassis is quite solid, and generally looks good from every angle. It was also a good mix of studded and studless building. Basically, it had most of the mechanisms that were available at the time, all in one set.

There are a few things that I think could have been better though. As mentioned above, the crane can't lift too much weight, and when lowering the boom it tends to fall quite quickly if you're not careful. If you keep the boom up, over time it will slowly fall, but this is more a comment on the pneumatic system rather than the design of this set, although the heavy boom probably doesn't help here. The rotation of the crane is done manually (no gears involved), but it would have been nice if this had some mechanism behind it. I guess the only other think that this set could have included is a pneumatic compressor rather than a manual pump, but I don't think this set really needs it.

Overall, 8421 is still one of my favourite Technic sets.

8455 would have to be my favourite pneumatic set of all time. The only thing that bothered me with that set is the front steering. All the pneumatic functions are great though.

Edited February 29, 2012 by Splat

[davidmull]

There is away to improve the boom falling fast and that's if u connect the other pneumatic tubes that Lego didn't! It does improve things and looks way better too.

[allanp]

Isn't the boom on this crane heavier and longer than the boom on the 8043 excavator, ya know, the one LAs had trouble lifting?

Seriously tho the pneumatics would benifit from adding the hoses to the other ends of the cylinders and the other end of the valve to restrict the airflow a little more. But this is deffinately a case where longer pneumatics would have helped alot.

Edited February 29, 2012 by allanp

[technicfan]

There is away to improve the boom falling fast and that's if u connect the other pneumatic tubes that Lego didn't! It does improve things and looks way better too.

Davidmull can you please put up some pics of what you mean and how it can be fixed. I thought about putting a trailer on the back to sit the arm on and putting a compressor function in the trailer to help with the weight of the arm. Like in the pic:

Edited March 1, 2012 by technicfan

[RohanBeckett]

8455 would have to be my favourite pneumatic set of all time. The only thing that bothered me with that set is the front steering. All the pneumatic functions are great though.

Really?

I actually thought the steering, with the link-arms was quite clever, and made excellent use of the limited space at the front of the model.

It's responsive.. not *too* sloppy (unlike some more recent link-arm steering models).. and provides a nice tight turning circle, which in turn gives a lot of playability.

Just looking at mine now... and it's amazing how close the lower steering gear is (attached to the horizontal steering axle), to one of the drive-gears, next to the diff

It's barely 1 mm away from grinding! Some designer got lucky, when positioning them!

RB

[Splat]

Really?

I actually thought the steering, with the link-arms was quite clever, and made excellent use of the limited space at the front of the model.

It's responsive.. not *too* sloppy (unlike some more recent link-arm steering models).. and provides a nice tight turning circle, which in turn gives a lot of playability.

Just looking at mine now... and it's amazing how close the lower steering gear is (attached to the horizontal steering axle), to one of the drive-gears, next to the diff

It's barely 1 mm away from grinding! Some designer got lucky, when positioning them!

RB

The geometry of the steering is great, and I agree that it is an ingenious use of the space available, but what I don't like about it is that when you press the two pneumatic pumps in the cab, a lot of force is transferred to the front of the vehicle, and the steering arms and surrounding chassis feel like they are working themselves loose. The front wheels are only held on with axle-pins, and those axle-pins also take a lot of the force applied.

I'd have to disagree about the 'sloppiness' of the link-arms though. It's not as bad as some other sets, but I can hold one wheel and move the opposite wheel about 15-20° either way. When playing with it it is mostly unnoticeable, but it's still there.

As I mentioned above, 8455 is my favourite pneumatic set, and one of my favourite Technic sets overall, but the steering just lets it down a little bit and stops it from getting top marks in my opinion.