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Leopard 2A4

October 31st, 2010 Leave a comment Go to comments

1/18 model of a German Main Battle Tank, features torsion bars suspension, rotating turret, rotating commander’s cupola, self-levelling main gun, gunner’s gun counter-rotation system, lights and custom stickers.


Completion date: 28/10/2010
Power: electric (Power Functions)
Dimensions: length 70 studs (including main gun’s barrel) / width 26 studs / height 23 studs (not including antennas)
Weight: 3.42 kg
Suspension: torsion bars
Propulsion: 4 x PF XL motor geared 1:1
Top speed: 1.5 kmph
Motors: 4 x PF XL, 2 x PF Medium, 1 x Micromotor

My first dark grey tank with a conventional construction (i.e. with a turret). I broke my ‘no German tanks’ rule, but at least the 2A4 version serves also with Polish army. It’s also the last version of Leopard with it’s original turret, whose distinctive shape (resulting from limitations of then-early modular armour technology) reminds me somewhat of German WW2 tanks. Leopard 2 is the world’s first 3rd generation tank (a brief explanation on tanks generations is available here), resulting from a failed joint German-US Main Battle Tank project (one that gave birth to Abrams M1 too) and introduced in late seventies. It’s a very universal construction with strong focus on mobility, and it has become quite popular, especially within EU. Widely considered as European Abrams’ counterpart, it has seen action e.g. in Kosovo and Afghanistan. The newest version currently in service is 2A6, while a 2A7+ version is under development.

I have started to work on this model in an unprecedented way, that is by buying a 1/35 scale plastic model kit of the Leopard 2A4 (which alone took a couple of months, as models of this versions of this tank at this scale are exceptionally rare, I only found them in Hobby Boss’ catalogue and already out of production) and putting it together for reference. I have obviously used a blueprint for calculating the dimensions too, but the plastic model gave me incomparably better reference, such as details of the portion of the hull that is covered by the turret or the decals compliant with German army’s marking patterns. It also helped me to get the idea of various subtle angles and shapes that were difficult to notice on a blueprint, and provided a clear view of some details that appeared vague on it. I am generally happy with the model’s look which suffered few compromises, except for a single serious one: the two grills on top of the rear hull surface, which should be round. I was forced to place three IR receivers beneath this surface, which made it impossible to accurately model the round shape of these grills – I wish I could do that e.g. like here.

Technically, the model was primarily meant to test a new suspension concept, based on torsion bars – a solution taken straight from the real tanks. Torsion bars suspension uses road wheel mounted on end of short rods, whose other end is set on a flexible element which twists under load, thus allowing the road wheel travel up and down. The simplest application of this solution with Lego pieces was a bit unorthodox: it required regular axles, which have a degree of elasticity, to be twisted.

Just like  in my previous tank model, the 6595 wheels have been used as the road wheels. They were mounted on bent 2×4 liftarms, so that they could rotate and maintain good ground clearance. The other ends of the liftarms were set on 8 studs long axles inserted transversely into the hull’s floor. Both ends of the axles were supported, but the inner ends, in the middle of the hull, were locked so they couldn’t rotate. Thus the axles were firmly braced in the chassis, with one end still free to rotate – the end with the liftarm and road wheel on it. It resulted in axle twisting slightly under load and then twisting back when the load was gone. Contrary to what I was afraid of, no apparent damage to the axles occurred, and this kind of suspension turned out to work excellently and to be extremely space-efficient (all it took was basically a single stud of hull’s height). Moreover, the hardness of this suspension can be easily adjusted by using shorter axles or by changing the locking point on them. In this model, each road wheel was subject to an average load of almost 250 grams and the suspension worked perfectly well with an 8 studs long axle, given 4 studs of space between the liftarm and the axle’s locking point.

The model is driven by an unusual number of four motors, all XL. Each of its four sprocket wheels is driven by a separate motor, and the whole set is powered from two separate battery boxes through two separate IR receivers (set on the same channel), with each battery box powering one left and one right motor. I hoped that the massive torque provided by all these motors together would make the model fast despite its weight, and early version with almost 3:1 gear ratio proved to be very fast. Unfortunately, the performance degraded rapidly with the growing weight, and at 3 kg the motors were unable to move the model at all. I’ve spent almost 2 hours changing the gear ratio to 1:1, viewing it as the most efficient ratio possible and unwilling to experiment with something between 3:1 and 1:1 lest I spent another 2 hours changing it again. It appears that XL motors, despite all their power, become increasingly ineffective when used with accelerating gear ratio. It is also possible that it takes more torque to move heavy tracked vehicle than it does for a wheeled one of the same weight.

Except for the four XL motors and two battery boxes, the hull houses three IR receivers, a single PF Medium motor that rotates the turret and the entire turret rotation mechanism along with a turntable. Placing the turret’s turntable inside the hull had a number of advantages: most importantly, it made the rotation mechanism simpler and more robust, and made the construction of turret’s base much simpler while leaving plenty of free room inside the turret. There are two wires going through the turntable, so it can’t rotate infinitely, and there is a simple liftarm frame the turret is built around. The frame includes a single roller behind the turntable, which keeps the turret’s rear end from touching the hull.

Inside the turret, I wanted to have a self-levelling main gun with remote elevation control. To put these two features together, I have built a module suspended on a transverse axle, which connected the main gun with its counterweight and had a micromotor in between, so that the angle between the main gun and its counterweight could be changed remotely. It worked as expected, joining the two features: changing the angle between the main gun and the counterweight by e.g. 30 degrees would result in the main gun going up (or down) by 15 degrees and the counterweight doing exactly the same, while the whole module kept self-levelling all the time. Two problems prevented me from using this mechanism: firstly, raising and lowering the counterweight required more space inside the turret than was available, and secondly, the micromotor’s wire kept affecting the module’s position, no matter how I arranged the wire. Eventually, I decided to keep the self-levelling feature and to remove the elevation control at all. Tank model with no main gun’s elevation control is certainly at disadvantage, but I thought that since all my tank models had this feature, I can do something different just this once. So, I removed the micromotor from the module, positioned the counterweight as close to the main gun as possible, and added another counterweight below the pivot point to lower the module’s centre of gravity – as it was apparent that the accuracy of self-levelling increases with the centre of gravity being further from the pivot point.

The micromotor which was removed from the self-levelling module served as a propulsion for commander’s cupola. It proved perfectly suited for this purpose, because no gear reduction was needed and the cupola is mounted directly on the motor.

Finally, there is a PF Medium motor in the rear part of the turret. I had a lot of space available in the turret, but all the IR channels were already in use, so I was looking for some additional use of the channel controlling turret’s rotation. Eventually, I have built a copy of turret’s rotation mechanism inside the turret, driven by the aforementioned Medium motor and working in opposite direction. The motor was connected to a switch inside the hull, and the switch was connected to the same IR receiver’s output as the motor rotating the turret. It resulted in a possibility to turn on or off a mechanism that would rotate something on top of the turret against the turret itself, thus keeping it aligned with the hull. The obvious choice was to select gunner’s machinegun as the counter-rotated element. The mechanism worked well, but the difference in resistance met by the motor rotating the whole turret and the motor rotating the machinegun alone resulted in different speeds of rotation, with the machinegun rotating slightly faster than the turret. Thus the machinegun does not really stay aligned with the hull, but slowly rotates in opposite direction that the turret does. It should be noted that since two copies of turret’s rotation mechanism were built, there are actually two turntables in this model: one below the turret and another one inside it.

Despite its few shortcomings, the model met a very positive response, being occasionally called my best tank model yet. I was slightly disappointed by its speed, but delighted at its suspension which worked way beyond my expectations, providing excellent flotation without using a single shock absorber. Personally, I consider this model as a preliminary study for my next tank, the South Korean K2 Black Panther, which will develop some of Leopard’s solutions further and hopefully improve in general wherever possible.


01.jpg 02.jpg 03.jpg 04.jpg 05.jpg 06.jpg 07.jpg 08.jpg 09.jpg 10.jpg 11.jpg 12.jpg dsc06729.jpg dsc06731.jpg dsc06737.jpg dsc06741.jpg dsc06742.jpg dsc06746.jpg dsc06751.jpg dsc06755.jpg dsc06757.jpg dsc06758.jpg dsc06759.jpg dsc06761.jpg dsc06765.jpg dsc06772.jpg dsc06774.jpg dsc06789.jpg dsc06802.jpg dsc06808.jpg dsc06810.jpg dsc06814.jpg dsc06815.jpg dsc06820.jpg dsc06821.jpg dsc06823.jpg dsc06826.jpg dsc06828.jpg dsc06833.jpg dsc06834.jpg dsc06838.jpg dsc06840.jpg dsc06842.jpg dsc06851.jpg dsc06853.jpg dsc06862.jpg

Work In Progress photos:

01.jpg 02.jpg 03.jpg 04.jpg 05.jpg 06.jpg 07.jpg 08.jpg 09.jpg 10.jpg 11.jpg


Media Reference:

Rock’n Tech (Portuguese only), The Brothers Brick

Categories: Military Tags: , , , ,
  1. Sariel
    November 2nd, 2011 at 12:13 | #1
  2. capmalo
    November 2nd, 2011 at 12:01 | #2

    Can you send me more pictures of the interior of the tank and the turret

  3. Sariel
    October 27th, 2011 at 21:29 | #3

    Yes, I even put this number in the description: 6595

  4. robotjoe
    October 27th, 2011 at 20:58 | #4

    Hey, i was wondering what kind of wheels you used, I’ve been looking for them online but i’m not sure they are the right ones. Do you have the element number?

    Thanks =D

  5. Zeus
    October 25th, 2011 at 11:02 | #5

    Now it’s clear :-). I did try it like that, but the axle with stop I was using still had a protruding knob on it. Now I know what part to get.

    Thanks again, m8!


  6. Sariel
    October 25th, 2011 at 08:40 | #6

    The axle rotates, and it doesn’t need to be locked on the other side because it’s this axle: http://www.bricklink.com/catalogItem.asp?P=87083

  7. Zeus
    October 25th, 2011 at 08:19 | #7

    Thanks for your quick reply! Unfortunately I still don’t get it ;-).

    I understand the torsion bar part. What I can’t fathom is how the wheel is attached to the liftarm! I would guess an axle, but then how is the axle fixed to remain in place? Because the liftarm is flush against the hull, it’s not possible to have the axle go through the liftarm and lock it on the other side.

    Sorry if I’m being obtuse, any insights are appreciated :-).


  8. Sariel
    October 24th, 2011 at 23:24 | #8
  9. Zeus
    October 24th, 2011 at 22:19 | #9


    I was wondering: how are the road wheels attached to the 2×4 liftarms? Those liftarms seem to be flush against the hull, so it doesn’t seem like there is some sort of locking piece holding the axle in.

    I’m relatively new at Lego Technics, so maybe it’s simply a part I don’t know :-).



  10. Sariel
    October 23rd, 2011 at 19:39 | #10

    I don’t have parts list nor instruction, sorry.

  11. Bo
    October 23rd, 2011 at 18:11 | #11

    Awesome! Can I get a parts list and/or instructions from you. I can pay if necessary. Thanks.

  12. Sariel
    October 23rd, 2011 at 15:58 | #12

    @El Bastardo
    Brałem z mojego biurka.

  13. El Bastardo
    October 23rd, 2011 at 14:56 | #13

    W jaki sposób dobierałeś elementy do całości??

  14. Sariel
    October 11th, 2011 at 12:26 | #14
  15. El Bastardo
    October 11th, 2011 at 12:14 | #15

    Sariel masz instrukcje albo chociaz wykaz czesci?

  16. LegoFreak
    September 18th, 2011 at 02:11 | #16

    Yeah, understandable, but I don’t find someone with enough wheels =(

  17. Sariel
    September 13th, 2011 at 07:40 | #17

    From a seller who had them at reasonable price?

  18. LegoFreak
    September 13th, 2011 at 01:04 | #18

    Hey, another question, I hope I don’t annoy you 🙂
    where did you get the wheels from, I mean exactly where from at BrickLinks?

  19. LegoFreak
    September 12th, 2011 at 15:34 | #19

    ok, thanks a lot, maybe there will be come up more questions from me the next days, but thanks for the fast answers

  20. Sariel
    September 12th, 2011 at 15:29 | #20

    Bluish, of course. It looks better.

  21. LegoFreak
    September 12th, 2011 at 14:57 | #21

    another question: Did you use “Light bluish grey” or “Light grey” for the most parts of your tank?

  22. Sariel
    September 12th, 2011 at 14:44 | #22

    Sorry, I deleted them after printing.

  23. LegoFreak
    September 12th, 2011 at 14:41 | #23

    do you have pre-printed forms, which you could send me as a data file?

    I would be an honor for me 😉

  24. Sariel
    September 11th, 2011 at 21:23 | #24

    I didn’t get them, I made them.

  25. LegoFreak
    September 11th, 2011 at 20:40 | #25

    Hey, where did you get the stickers from?

  26. Sariel
    September 9th, 2011 at 21:33 | #26

    No, I’m afraid it is not as they don’t exist anymore, and even if they did, I would still not sell them.

  27. mattes
    September 5th, 2011 at 13:36 | #27

    Hello Sariel,
    I know you not really wanna sell your models but in spite of this it is possible to get a model of
    the Leopard 2A4 and the RG-35 ???

  28. Sariel
    August 27th, 2011 at 00:00 | #28

    @Raphael Enevoldsen
    First of all, Lego does not buy designs from outside, ever, and second of all, even if they did, they don’t make anything related to the military theme, ever.

  29. August 26th, 2011 at 23:53 | #29

    This is awesome. Have you tried to sell it to Lego so they can sell it as a kit?

  30. Sariel
    August 21st, 2011 at 15:29 | #30

    Just a bunch of books on tanks.

  31. Watta!
    August 21st, 2011 at 15:18 | #31

    Hey, what books do you use in the movie as ramp.

  32. Sariel
  33. August 4th, 2011 at 12:34 | #33

    Sorry, I didn’t mean chain. Two more questions.

    1Can you tell me the kind of remote controls did you use?

    2How did you connect the micromotor to the batteries?I ask this because the micromotor isn’t power functions .

  34. Sariel
    August 3rd, 2011 at 17:34 | #34

    I didn’t use any chain.

  35. August 3rd, 2011 at 17:25 | #35

    Can you tell me the kind of chain you used to build Leopard (Another perfect creation) please!

  36. Sariel
    July 3rd, 2011 at 18:56 | #36


  37. Icke
    July 3rd, 2011 at 18:05 | #37

    hello sariel,this tank is a masterpiece,respect !!
    my question on you is logic : is it possible to send me an instruction-file ?
    in hope : icke

  38. brice dewitt
    June 29th, 2011 at 16:01 | #38

    wow brilliant i wish i could create something like that i would like to know more about the construction as it would be cool to build one myself

  39. Sariel
    June 25th, 2011 at 15:20 | #39
  40. allu
    June 25th, 2011 at 15:12 | #40

    and what was the pieces you used as counterweights on the main gun

  41. allu
    June 25th, 2011 at 15:10 | #41

    in finland there is no shops with the pieces that i need and in other countries the shipping fees to finland is huge

  42. Sariel
    June 25th, 2011 at 12:41 | #42

    I suggest choosing one that has pieces you need at low price and with low shipping fees. That’s what I do.

  43. allu
    June 25th, 2011 at 12:07 | #43

    what store in bricklink you use?
    i don´t know wich store to buy from=(

  44. allu
    June 24th, 2011 at 18:21 | #44


  45. Sariel
    June 24th, 2011 at 17:43 | #45

    It simply hangs on a transverse axle. Its weight balances it.

  46. allu
    June 24th, 2011 at 17:14 | #46

    im building a leopard too but it has only six roadwheels on one side

  47. allu
    June 24th, 2011 at 16:38 | #47

    that how it levels itself and what is pivot

  48. Sariel
    June 21st, 2011 at 22:39 | #48

    Sure, what seems unclear about it?

  49. allu
    June 21st, 2011 at 22:04 | #49

    could you explain the self leveling main guns machanism a little better?

  50. SGT Jensen
    May 17th, 2011 at 16:09 | #50

    Leopard 2A5 tank commander of the Danish army.
    very very nice job!

  51. technikfreak
    March 8th, 2011 at 20:24 | #51


  52. Sariel
    March 7th, 2011 at 18:22 | #52

    That’s wonderful.

  53. technikfreak
    March 7th, 2011 at 17:48 | #53

    hmm i also bhave built a tank

  54. David
    February 27th, 2011 at 20:44 | #54

    oh ok thanks

  55. Sariel
    February 27th, 2011 at 08:40 | #55
  56. David
    February 27th, 2011 at 01:43 | #56

    um what is torsoin because i dont understand how it works

  57. Sariel
    February 23rd, 2011 at 19:40 | #57

    They connect, you know? Or have you never seen any Lego brick?

  58. technikfreak
    February 23rd, 2011 at 17:45 | #58

    how make you it with the normal bricks on technik bricks ?????

  59. Sariel
    January 4th, 2011 at 19:23 | #59

    Je ne vais pas.

  60. Nico
    January 4th, 2011 at 19:11 | #60

    Aurai tu des instructions de montages?

  61. Nico
    January 2nd, 2011 at 01:44 | #61

    Qui pourrai m’aider a trouver des piece detacher de lego S.V.P il me manque des chenilles comme le lego 8275 et plein dautre piece, et j’adore se que tu fait sariel =D

  62. Sariel
    January 1st, 2011 at 14:18 | #62

    No, thank you.

    January 1st, 2011 at 14:11 | #63


    this is amazing!!! Good work! Can I buy it?? Do you want to sell it??

    Giacomo (Italy)

  64. Sariel
    December 15th, 2010 at 13:23 | #64

    A single battery box doesn’t provide enough power to fully power 2 XL motors, don’t even think of 4. And I didn’t use rechargeable batteries because they provide even less power, and I wanted the tank to be heavy for good traction.

  65. sqiddster
    December 15th, 2010 at 11:11 | #65

    This is great. Too great. Seriously, I am starting to build a tank, and I am worried about copying you too much, because all your ideas and mechanisms are top-notch.

    One question. With the power scheme you are implementing, did you test the tank with only one battery box? Did it not provide enough power? also, why did you not use your two rechargeable battery boxes? (You have two, right?)

  66. Sariel
    December 5th, 2010 at 10:55 | #66

    Thank you. I’m only gearing up when there is an abundant torque to use. Which wasn’t the case here, eventually.

  67. December 5th, 2010 at 03:24 | #67

    Why do you gear the motors up? I have always geared my motors down or leave them how they are to preserve torque. Your creations are amazing. I always use your ideas and mdels to try to construct my own.. although i am not very successful, you are always an inspiration to me.

  68. Sariel
    December 3rd, 2010 at 08:03 | #68

    Dokładnie nie liczyłem ale na pewno powyżej tysiąca.

  69. Mironas10
    December 3rd, 2010 at 07:44 | #69

    najleprzy model ktory ja widzialem. A ile naprzyklad kosztowaly detale dla tego modelu??

  70. Keule
    November 28th, 2010 at 00:09 | #70

    Great Model. I wish i have so many LEGO in one Color….
    If you want, i can send you a video of my Tank… it based on Lego 8275

  71. November 17th, 2010 at 16:11 | #71

    Leopard 2A4 normalnie jak na polu walki , tylko brakuje żołnierzy

  72. victor
    November 11th, 2010 at 19:35 | #72

    COOL but scary

  73. November 10th, 2010 at 22:39 | #73


  74. Sariel
    November 7th, 2010 at 14:02 | #74

    That’s why I don’t keep rotating in the same direction 🙂

  75. November 7th, 2010 at 13:38 | #75

    dont the wires inside the turret get twisted if you keep rotating it in the same direction? hmm coz i had the same problem when building a crane. it could help by puttting an independant battery pack in the turret.

  76. Axel
    November 6th, 2010 at 01:36 | #76

    best tank I´ve ever seen!! he is perfect

  77. horst
    November 5th, 2010 at 17:45 | #77

    i hope you didnt get me wrong: that was no critic

    thats an amazing model!!!!
    its just an idea to get it faster- a bit, and about 150g less weight.

    mine isnt a beauty-like yours 🙁 and im using a gearbox like in 8043- so i need to shift to use all functions…

  78. horst
    November 5th, 2010 at 17:12 | #78

    2800g including Batteries

  79. Sariel
    November 5th, 2010 at 10:15 | #79

    And just how heavy your tank was?

  80. horst
    November 5th, 2010 at 10:04 | #80

    good job,
    did you already try 4 medium engines instead of the 4 xl ? they are much faster and can be geared down for torque. My tank (almost the same size) works well and fast ;-). Also you can use just one batterie box- less weight- more power 🙂 … the engines arent as heavy too

  81. Sariel
    November 4th, 2010 at 09:39 | #81

    I could, but that would limit the number of rotations the turret could do before locking up.

  82. ray
    November 4th, 2010 at 00:23 | #82

    Could you have used the turret’s space to couple the gunner’s and main turret mechanically? That would have solved the alignment issue. Still, another great model.

  83. Sariel
    November 2nd, 2010 at 23:41 | #83

    These are ventilation holes in my bathroom’s door. It has no window and a geyser inside, so this is a safety measure.

  84. an0nymous
    November 2nd, 2010 at 22:33 | #84

    I know this is completely unrelated to lego, but what were those black circley things at 1:33 in the vid?

    And congratulations on another great model! 😀

  85. Sariel
    November 2nd, 2010 at 19:08 | #85

    Counterbalance is done with with these: http://www.bricklink.com/catalogItem.asp?P=73090a
    I felt no need for rubber tracks as the sheer weight of this model provides a decent traction with regular Lego tracks. Also, I think the rubber tracks would ruin model’s look because of how thick they are.

    This is Lucius, who has been with me for almost a year and has already appeared with a number of my constructions.

  86. simontomi
    November 2nd, 2010 at 18:33 | #86

    Ohh, who is the new hamster ? 🙂

  87. Killubear
    November 2nd, 2010 at 17:42 | #87

    Love the new tank, love your work.
    What did you use for the counter balance and pivot weights?
    have you considered making modifications to the treads of your tanks by adding rubber for grip?

  88. Sariel
    November 2nd, 2010 at 11:35 | #88

    6595, as clearly written in description.

  89. Gotte
    November 2nd, 2010 at 11:34 | #89

    What´s the number of those wheels?
    Very nice suspension.

  90. Sariel
    November 2nd, 2010 at 08:06 | #90

    By simply rotating the inner ends of torsion bars.

  91. Justin
    November 2nd, 2010 at 03:26 | #91

    Oh man, That is sick. The little machine gun on the top with the rotating, Mind = Blown.

  92. zackhariah
    November 2nd, 2010 at 01:53 | #92

    i love your tank, and im a big fan of your work

    for the self-leveling gun the farther you put the counter weight form the pivot point the less weight you would need to balance it, then you wouldn’t need to make the main gun thinner.

    for the black panther how do you plan on making the adjustable Suspension?

  93. ben
    November 2nd, 2010 at 01:24 | #93

    the suspension is a beautiful thing indeed, but i still cringe every time i see it start to twist almost all the way. i couldn’t afford to build a tortion bar system like this. i wish i could but i cant…..

  94. legonut
    November 1st, 2010 at 21:58 | #94

    the suspension is so beautiful i want to cry. great job.

  95. matthew
    November 1st, 2010 at 21:51 | #95

    Im not saying you should, but would 4 xl motors make it perform offroad nicely? or would the weight make it slip?

  96. mr J
    November 1st, 2010 at 17:00 | #96

    another stunning model 😀
    really like the torsion suspension, works really well!!
    few well thought out features like the counter rotating machine gun and the capula 🙂
    What is a cupola? is it like a periscope..

  97. Dave Benson
    November 1st, 2010 at 14:42 | #97

    Interesting motor-configuration. I´m in the process of designing a quite massive bulldozer (maybe around 5-6kg) with 4 XL motors, geared down for maximum torque and with custom rubber caterpillars. Though you got me a little worried that 4 XL wouldn´t be enough even for 3,5kg, but I´m not going for topspeed anyway. More of a rockcrawling badass dozer!
    Standard technic link treads gives poor grip on slippery surfaces as you show in the vid. Would maybe be a good idea if you invent your own rubber caterpillars if you build bigger models in the future? It´s quite hard I have discovered, but hardly impossible.

    Anyway, the Leopard turned out very well I think!

  98. Sariel
    November 1st, 2010 at 13:28 | #98

    I could but it wouldn’t look good. This thing shoots: http://sariel.pl/2009/06/rumbler/

  99. allu
    November 1st, 2010 at 13:18 | #99

    that was great but could you build a tank that shoots?

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  1. November 30th, 2010 at 13:35 | #1