Saturday, November 23, 2013

TBs TechChallenge, 2013 - Reverse 42020 (Twin Rotor Helicopter)

Here we're again for the 2013 edition of  the TechREVERSE Challenge, in collaboration with the LEGO Technic product line. This is the fifth edition we do for this contest, this year covering one of the 1H2014 models.

As usual, the challenge will consist in the build reversal of one small LEGO Technic set. Among the several possibilities available I believe we decided for a fair challenge this time and hope you enjoy it.
We believe this model doesn't include any new elements, although if you think otherwise you should ignore eventual new element(s) and leave the respective space empty in your CAD model.

As may have been anticipating the set selection for the current TechREVERSE Challenge issue is the 42020 (Twin Rotor Helicopter).

And then the challenge TBs for you, is exactly this!
Reverse and build your own digital reproduction from the 42020 main model, based on the product pictures available so far.

Based on the successful experiment and results from the previous years, we decided once more to allow submissions made in any of the most common CAD tools in use by the FOLs, to model their LEGO creations (LDraw/MLCadLDD and SR 3D Builder). 

Of course you may need to download and install any of these tools if you have not done it already before. Therefore some previous advices regarding LDraw installation may become handy.
Specially make sure you use the latest parts library available for the tool you're using. Otherwise it may negatively affect the ranking of your participation.

As for every contest, there must be some rules defined that will help us later to determine who's the winner. So please read them carefully.

Challenge Goal:
  • Reverse engineer and reproduce a digital model, from the Challenge proposed LEGO Technic set.
  • The reproduction should be exact (model complete assembly, parts list, colors and elements positioning).

Challenge Participation Rules:
  • Every contestant should submit his participation in the form of one single digital file, compatible with the latest version of one of the tools allowed in this contest (at contestant choice) - LDR, MPD, LXF or L3B.
    Hierarchical organization into sub-models is also allowed, for the tools supporting this.
  • The contestants are allowed to enter one single submission only (always the first one submitted).
  • Each contest submission must include one single model only.
  • Contestants must also include one render image from their model, with a minimum resolution of 800x600 pixels.
    It would be great if you have photo-realistic rendering skills, but not considered as criteria for the purpose of this contest evaluation.
  • Any eventual special elements in the model must be reproduced accordingly (e.g. flexible parts, shock absorbers, etc...). Reproduction should be as close as possible to the original.
  • All the submissions must be sent via e-mail, to the TBs mailbox setup for the purpose of this challenge, with indication of the applicant identification (full name and nickname if applicable), postal* and e-mail addresses.

    TBs TechREVERSE Challenge mailbox: challenge[at]

Classification Criteria:
  • The winning participation will be the first submission sent, that exactly matches the LEGO official model subject of this challenge: model complete assembly, parts color, elements positioning and parts list.
  • If none of the submissions fill all the criteria above, it will be selected the first submitted one, that gets closer to the original, based the total mismatches counted.
  • There are different weights for each type of mismatch as a mean to differentiate the mismatches severity and increase the evaluation fairness.
    Each mismatch will sum a certain number of negative points (penalties) per occurrence, based on the respective mismatch type. The participation with less accounted penalties wins!

    The penalties per mismatch type are:
    5 Points - Missing parts or subparts (so that you do not get tempted to avoid guessing on hidden parts just because it may lead to more mismatches than using wrong, extra or misplaced parts).
    3 Points - Wrong parts or subparts (includes friction/frictionless mismatches).
    3 Points - Extra parts or subparts.
    3 Points - Parts or subparts misplacement (including deviation and/or orientation).
    3 Points - Wrong color used for a part or subpart (if the element is visible in some of the pictures available).
    2 Points - Wrong color used for a part or subpart (if the element is not visible in any of the pictures available).
    1 Point -  Every other eventual situation not covered above (e.g.: wrong spring strength, significant routing deviation from the original on flexible elements, etc.).
  • Classification (penalties sum) may not go through all the mismatches until the last one, once the amount gets too high and difficult to evaluate consistently, that it turns clear the participation won't get among the ones granted with a final prize.

  • All the submissions must be sent to the mailbox above indicated, in the next ten calendar days. Thus before the 3rd of December 2013, 16:00 CET**.
  • The organization reserves the right to extend or shorten the submission period, if there is a reasonable justification (e.g. too few participants, leak of the actual model or building instructions).
  • Final results are expected to be published until February 2014, but it may depend on the amount of submissions to the contest and bandwidth availability for the required verification work.


  • As usual the prizes will be some of the upcoming new LEGO Technic sets, signed by their respective designers. The details about these will be announced timely.

  • In the event of any eventual leak with further official details about this model, during the contest submission period, it may become a justification to close the submissions period anytime earlier.
  • Any eventual issues not foreseen in the contest rules, shall be evaluated and decided by the board of TBs editors.
  • The organization reserves the right to cancel the contest at anytime, if participation quality levels are not getting satisfactory.

Take part of the fun!

*) Your private data won't be published, or used for any other purpose other than this contest.
**) Use the link provided, to find the correspondent local time at your own Time Zone.


Gabriel Leite said...

I can't send you my submission, all of my accounts say that "challenge[at]" is invalid.

Captainowie said...

Gabriel, try replacing "[at]" with "@"

Gabriel Leite said...


Balrog said...

Submitted my entry. This is a cool challenge :D

MajklSpajkl said...

I already submitted yesterday, can't wait for the results!!! It would be great if total ranking of all the participants is released in order to see how well we did.

iPelaaja1 said...

I want to try to build it, but I cant even find the propeller blades in LDD, neither there is white 9M beam... and i suspect atleast one or two other parts are missing too

R0Sch said...

make sure you have the latest Lego Digital Designer version installed or updated with the current parts library (usually it updates automatically when the program starts). Unless there are some new types of parts that will be released with this set, I have found propellers and every part there is to this model in LDD.
Hope this helps. Good luck to all!

iPelaaja1 said...

@R0Sch I have the LDD 4.3.6 (Brick version: 1182). Do I have to get a parts pack or something from somewhere to get the blades, white 9M beams and few other pieces?

Fernando Correia said...


Better you use LDD Extended mode.
Then you could select a part (e.g. beam 9M) and "paint" it whit whatever the color you need/like.

As for the rotor blade, search for '99012' in the same mode.

Algirdas Lašas said...

I've just sent my entry. It was made with LDD and I found all neccessary parts.

Btw, when participations time will end, it would be nice to know how many participants were this year, and also it would be nice if we could download each LDD (or other editor) files to see how each of us has solved various problems :)

Fernando Correia said...


Thanks for entering the contest once more!

And yes, I'll share final amount of participants. 16 so far... We've already beaten the previous record by far!
It looks I'll be in big trouble this year... :)

iPelaaja1 said...

@Fernando Correia
I tried to change my LDD to extended mode in the preferences file, but nothing changed. Well, I dodnt really know how to do some bits anyways, so I'll just make your job easier with one less submission ;) Great job on the blog, I've been following it for a long time, Im huge fan of Lego Technic and Mindstorms. Thanks for putting all the time and effort in the blog so far and hope it will still be around for years to come.

Fernando Correia said...


Thanks for the praise. I hope in future I'll be able to put the same energy in this blog, as I did in the past. Unfortunately that has not been possible in the same extent at the moment.

I've not been using LDD for some time, and probably some changes have happened, or then I don't remember exactly how it was before.
When started it today, it made some updates, and once opening I got the option to create a project in one of three different modes (Digital Designer, MINDSTORMS, Digital Designer Extended).
Although I also remember the Extended mode was set in a configuration file, long ago.

I think this has changed.

M. Redepenning said...

Maybe Milan Reindl can give early help with judging, since he designed the model!

Milan Reindl said...

Or maybe he can submit his own entry ;)Good luck guys. I think there might be just two places that might be a bit tricky otherwise the model is very simple.

Fernando Correia said...



It looks your model is already success.
Got already 26 submissions so far. some from very well renown AFOLs. :)

And it seems there participants have been very creative around those tricky places... :)

It looks I'll have a hard time, deep diving into all these submissions, to come-up with the winners...

Shimon430 said...

1 place was very tricky.. scanned almost every pixel and possible variation.. its not easy but definitely challenging, i wish there were "mini" tech reverse for other models even without prizes that would be awesome!

Algirdas Lašas said...

@Shimon430 - you can challenge yourself (as someone built 42024 using initial pictures). There are a lot of 2014 models:) Actually I've built my own initial model before announcing actual model for this challenge. I expected for this challenge one of two - this helicopter or snowmobile. But because snowmobile has some new parts, so it's much more likely, that it would be helicopter. So I've built it, and next day got confirmation:) Then I've tested some things, done some adjustments... and then rendered it. I hope we'll see other models and their solutions to those tricky problems :)

Shimon430 said...

I wish i had the time to build the model, test it and modify but unfortunately i don't have enough time so i just try imagine everything in my head. so far i only had 1 area that was problematic. it would be interesting to view each participants solutions and way of thinking, this is my favorite challenge and each year i wait for it, Good luck to everyone!

R0Sch said...

When will the results be posted?

Fernando Correia said...

Soon, I hope!...
Sorry for the delay. :P

Gabriel Leite said...

It's been 4 months, are there any predictions for results?

Fernando Correia said...

Believe me I'm very sorry for the huge delay with this! :((

No excuses are good excuses!!!

The amount of entries this year was overwhelming and well above my energy to handle them fast enough.
Above that I was also organizing my LUG annual big event and after a certain point I was totally unable to care about other things than the event itself.
This is now over and after some rest I'm slowly getting able to proceed with the pending stuff...
As you might have seen, this year I even had the need to suspend new posts at TBs... :(

I've analyzed sometime ago, every LDD entry and need to finish the LDraw and SR3D ones.
I really hope to be able to finish this long lasting task soon.

And really need to find new ways to carry this, if I want to repeat this in the future.
One idea that I had was to let the participants to evaluate their own mismatches in a second phase, and then focus on these results to do my own evaluation to short list of the best 10 or so, to check their evaluation and come with an official and uniform count of these to select the most accurate entries.

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