Frequently Asked Questions (FAQ):

Why are there no Adobe PDF building instructions available for the 8421 XL Mobile Crane?
I developed the 8421 XL mobile crane in 2006 and at that moment the original Technic
® 8421 mobile crane set was still sold by The LEGO Company®. I did not want to publish the building instructions on my website from legal and etic perspective, because The LEGO Company® did NOT publish their own building instructions at that time on their website.
As such, I never made building instructions in Adobe PDF format. So, the only material I have are the MLcad files... and I don't have plans to invest time in generating the Adobe PDF building instructions.

Remark: Another AFOL did made building instructions of the 8421 XL, see the 8421 XL page for more information.


How can I build the 8421 XL Mobile Crane if I have less experience with MLcad and LDview?
It is possible to rebuild the 8421 XL mobile crane, but you have to have some computer knowledge regarding installation of programs, and where these program stores there data (library directory, program directory, etc).
You need two programs (and you should invest some time in them to understand them), the CAD (computer aided design) program MLcad ( and the 3D-viewer LDview (
Important: make sure you have at least LDview version 4.0.1 (7 Febr. 2009), because this version of LDview is able to provide you with a 'step to step' view of each MLcad file.


Why is there no part list (extra parts needed) available for the 8258 Crane Truck modifications?
That's twofold:
1) There are not that many extra parts needed; and most of the parts do exists in other sets you already have.
2) I never took the time to separate the modified 8258 crane truck into the original parts to figure out the extra parts needed.


The 'Special Models' files for download are compressed with WINrar; where can I find the decompression software?
See for a free trail version. Or download freeware decompression software from (Microsoft Windows only).


I'm not able to open your files (Microsoft Excel files, MLcad files or Adobe PDF files). Can you send them per email?
No, due to the size of the files (especially the Adobe PDF building instructions) I can not send them by email.


Regarding the Excel inventories; I can not find the part numbers on Peeron or Bricklink
MLcad uses the Peeron ( part numbers instead of the Bricklink ( part numbers. However, most of the numbers are equal but not all. It seams that Peeron is changing there numbers recently (2009/2010) to catch up with Bricklink. That's why sometimes the 'older' part number is not searchable. Remark: This should nowadays less be a problem, as Bricklink/Peeron(Ldraw) and LEGO
® did synchronize their part numbers.


Can I buy your models (from you, or in shops)?
No, I don't sell my models.... and there are no shops who officially sell my models.


Are there specific original Technic® sets necessary to build your models?
Not particular, but I use some sets as a starting point (i.e. the 8275 remote bulldozer was bought to start the Prinoth Leitwolf project... because it had all the PF elements onboard). Everyone has to figure out by themself if additional Technic
® sets are needed, depending on the Technic® sets you already have.


How do you collect all the extra parts for your models??
Mainly I buy all additional parts from Bricklink (


Where can I get LONG pneumatic hoses (as used in the Dump Truck 10x4)? On Bricklink I can't buy them.
It is difficult to order LONG pneumatic hoses on Bricklink. However, sells LONG pneumatic hoses per metre. Although these hoses are not LEGO® original, they fits excellently on the LEGO® pneumatic parts. And goes easily through the holes of the Tecnic® parts as well. My experiences with these hoses are perfect!


How can I upload your parts inventory (excel) to websites as Peeron and Bricklink?
For some models, Bricklink XML part inventories are created. These XML files must be 'copied-paste' into the upload section on Bricklink.


Where can I find the building instructions of the original Technic® sets, as shown on your 'Photo Gallery'?
Original building instructions can be find (for instance) on:


Which Prinoth Leitwolf model (NT or OT) is superior?
The NT (stands for NEW TRACK system) is superior to OT (stands for OLD TRACK system). And the NT is remote controlled with PF, which is not the case for OT.


Is The LEGO Company® (TLC) aware of your models?
Yes, they are aware of my work and I got the opportunity to test their new track system for the Prinoth Leitwolf model.


What kind of process do you follow to design such professional LEGO® models?
Starting point is to decide which vehicle I like to rebuild in Technic® LEGO®. Next step is to collect photo's from different angles of the real vehicle. Then I try to find technical white papers on the internet regarding functions and dimensions. And after calculate the scale sizes, I start building with the bricks. During this building it is important to be very critical about the result (good is not good enough). Finally, after completion of the model I ask kids of my family and friends to play with it. This phase results in play-ability improvements of the model. If everything is still perfect, I redesign the model in CAD (MLcad); and even then some updates are made.


You must have lots of LEGO® bricks...
Not really, I don't buy every set every year. And, I reuse developed models for new ones. In total I do have ~ 50.000 bricks (estimated guess)


I notice that most of your instructions are not for free anymore; why did you change this and are the selling instructions a 1:1 copy of the 'free versions'?
The reason to move from free to selling instructions is twofold; a) the significant increased downloads requires now-and-then upgrades of my hosting fees, b) I'm under the opinion that a selling fee is reasonable, given the amount of time it takes for me to design models and to create instructions. All instructions I do sell nowadays are reviewed thoroughly and do come with additional information where required based on feedback and/or questions. As well, the renders are made of a higher quality.

Important to mention is that I have categorized my instructions as follows:

a) instructions that are add-ons for official LEGO® sets, they will remain free given the fact that I respect the 'Fair Play Policy' of The LEGO Group. The only exception is the London-Bus as I modified it significantly to make it 'remote controlled'.

b) all other instructions.


Can it be that the towbar (beam 9L) of the 8052 trailer is too long?
Yes, it must be a 7L beam. The PDF instructions and inventory are corrected per 8 July 2011.


I noticed that your video's on YouTube are shared under 'WuppieSoft'?!
Yes, I use WuppieSoft as alter ego of Designer-Han.