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January 23rd, 2009 Leave a comment Go to comments

A simple buggy. Features 2-speed remotely controlled gearbox, live rear axle and lights.


Completion date: 23/11/2008
Power: electric (Power Functions)
Dimensions:  length 47 studs / width 25 studs / height 25 studs
Weight:  1.08 kg
Suspension:  front: independent with shock absorbers / rear: live axle on shock absorbers
Motors: 2 x PF Medium

A simple sandrail (subcategory of buggies), built basically to test my live axle concept. A live axle is an axle that has no fixed attachment to the frame of the vehicle. Instead, it is connected by a system of links and supported by shock absorbers. Live axle suspensions are usually complex, but offer very good stability and excellent performance, comparable to those of a typical independent suspension. And just like the independent suspension, live axle does not let the vehicle’s weight affect the drivetrain, which means that it performs better in heavy vehicles that the pendular suspension does, because the weight doesn’t generate extra friction on the drivetrain components (except wheels, of course).

In Lego, a very complex live axle systems exist, with probably the most extreme example available here. Therefore my goal was rather to create something as simple as possible. I ended up with an axle suspended on 4 links and a driveshaft only – a solution that turned out to blend simplicity with reliability pretty well. It had two minor drawbacks: it was slightly affected by the driveshaft’s torque, just like the pendular suspensions are, and the driveshaft could be theoretically affected by the vehicle’s weight to some extent while maing a turn or climbing certain obstacles. Despite that, this suspension system worked far better that I could expect.

Another noteable feature was the use of the direction sensitive gearbox I have developed earlier. It was braced by liftarms here, and allowed the vehicle to be driven only forwards. It did work as expected, but the liftarmic frame turned out to be somewhat loose, and did not deliver the kind of performance that traditional bricks could.

The model was built with minimal attention to the aesthetic side, I just wanted it to look realistic, not pretty.  Therefore I’ve used rather unusual palette of colours, and did not intend to film the vehicle. The LUGPol community, however, showed much interest in the suspension concept, and persuaded me into filming it, so I’ve eventually published a video titled Live Axle, to emphasize the fact that it was the suspension concept that was important, not the actual car.


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  1. Sariel
    May 15th, 2013 at 09:03 | #1

    Yeah, probably.

  2. TwentyLeggedHen
    May 15th, 2013 at 00:59 | #2

    Just wondering, why did you choose dark grey instead of dark bley for the rear axle? Was it because of the color of the shock absorbers?

  3. Sariel
    July 8th, 2012 at 10:58 | #3

    You can easily build it from photos.

  4. Eric
    July 8th, 2012 at 04:18 | #4

    do you have instructions because i want the rear axle???

  5. liamisamonster
    May 21st, 2012 at 18:32 | #5

    Thankyou, this was a great help

  6. Sariel
    May 21st, 2012 at 00:31 | #6

    These are dark grey short shock absorbers. They have nothing to do with the Offroader set, and they are of medium stiffness when it comes to shock absorbers. Light grey ones are softer, yellow ones are harder.

  7. liamisamonster
    May 20th, 2012 at 23:58 | #7

    are the shock absorbers the same strength as the ones from the 8297 (offroader) or are they the weaker ones from smaller sets(light grey colour)? It seems a bit difficult to determine because of there colour appearing brownish and unfamiliar. It will help alot because i would like to replicate this design in some way and i am unsure whether my shock absorbers will support the model’s arsenal of power functions etc.

  8. Sariel
    October 28th, 2011 at 20:46 | #8

    Adding it is possible but will change nothing. The lateral movement is avoided thanks to how the driveshaft is constructed.

  9. Patrick
    October 28th, 2011 at 19:03 | #9

    Is it beneficial (or even possible at this scale) to add a watt’s linkage or panhard rod? how is lateral movement avoided without such a linkage?

  10. liamisamonster
    October 26th, 2011 at 22:31 | #10

    @Sariel ok thanks

  11. Sariel
    October 26th, 2011 at 12:55 | #11

    There was just no place to put it lower.

  12. liamisamonster
    October 26th, 2011 at 12:44 | #12

    was the battery box put so high on the back for a reason? or is that just a design feature, and well done for simplifying it so well.

  13. allu
    August 26th, 2011 at 20:38 | #13

    i can try

  14. Sariel
    August 26th, 2011 at 20:34 | #14

    Did you try to make a steered axle and suspend it like the live axle? It’s really that simple.

  15. allu
    August 26th, 2011 at 18:12 | #15

    I can make a live axle but I don’t know how to make a steered live axle

  16. allu
    August 26th, 2011 at 17:53 | #16

    I didn’t find a steered live axle

  17. Sariel
    August 26th, 2011 at 15:02 | #17

    There are plenty of steered suspensions in the Ideas category, check it.

  18. allu
    August 26th, 2011 at 14:56 | #18

    I’m working on a monster truck and I need help on the steering

  19. allu
    August 26th, 2011 at 14:54 | #19

    how to make it steered I’m working on a monster truck and I need help

  20. Sariel
    July 7th, 2011 at 13:03 | #20


  21. allu
    July 7th, 2011 at 12:51 | #21

    could you mace it steered

  22. Brian
    October 19th, 2010 at 17:12 | #22

    well i wish u guys with all ur talent would give us that arnt build ur stuff as well this would be an awesome build ,,,

  23. Sariel
    August 25th, 2010 at 20:28 | #23

    No, because absorbers can’t tilt sideways.

  24. will
    August 25th, 2010 at 18:04 | #24

    would it work if i replaced the upper pair of links with shock absorbers

  25. DW
    July 29th, 2010 at 21:07 | #25

    Thank you.

  26. Sariel
    July 29th, 2010 at 18:14 | #26

    Well, if a single M motor drives it, I think you should try something between 3:1 gear reduction and 1:1 ratio. Fresh batteries will help too, of course.

  27. DW
    July 29th, 2010 at 17:40 | #27

    The Buggy is rear wheel drive. It is powered by 2 M Motors, one for steering one for driving. The wheels are “http://www.bricklink.com/catalogItem.asp?P=41896c03”.

  28. Sariel
    July 29th, 2010 at 12:06 | #28

    I have no idea. I don’t know what motor drives it and what size are the drive wheels.

  29. DW
    July 29th, 2010 at 11:48 | #29

    I have made a dune buggy but I don’t know what is better for It, to have off-road capabilities or only speeding. and If it is off-road what gearing should I use. Weight=700 grams.

  30. Sariel
    July 13th, 2010 at 22:39 | #30

    Yes, they are the same length.

  31. will
    July 13th, 2010 at 22:12 | #31

    also are all the links the same length and when are you going to build the monster truck

  32. Sariel
    July 13th, 2010 at 07:58 | #32

    81.6 x 38 R wheels.

  33. will
    July 13th, 2010 at 04:21 | #33

    what size wheels did you use on the rear axle

  34. Sariel
    January 5th, 2010 at 22:00 | #34

    This suspension doesn’t allow that kind of angles on the u-joint.

  35. sqiddster
    January 5th, 2010 at 21:52 | #35

    Hey, very nice suspension there!
    Does the single universal joint usage produce problems? As i’m sure you know, they tend to provide increasingly discontinuous (is that the right word?) motion as their angle increases. Do you notice any ‘jerk’ in the speed?

    Many thanks, sqiddster

  36. Sariel
    January 2nd, 2010 at 19:58 | #36

    The clutch gear slips under a very specific torque. If you want it to slip less, place it close to the motor and put the gear reduction behind it. If you want it to slip more, place it further from the motor and closer to the final output. The trick is simply to manipulate the torque this gear transfers with some gear reduction before or after it. Check the Gears Tutorial if you have problems.

  37. Lukas
    January 2nd, 2010 at 19:38 | #37


    So you suggest moving the clutch at the end of the whole gear box, instead of at the beginning, right behind the motor?

  38. Sariel
    January 2nd, 2010 at 16:26 | #38

    The 3rd motor was supposed to control PF switch on the drive motor, but was not used eventually. There is no clutch in the drivetrain. You can’t make a clutch gear slip less, but you can put an extra gear reduction before it.

  39. Lukas
    January 2nd, 2010 at 16:11 | #39

    You wrote you used 2 medium motors, but in pics you can see 3rd one mounted on top underneath the batter box. What is it for? Also question #2: did you use a clutch gear on driver motor? Is there any tutorial about clutch gear? How to make it slip less (transfer more torque)?

  40. Sariel
    December 27th, 2009 at 17:03 | #40

    Ciekawe, nie miałem pojęcia.

  41. Lukas
    December 27th, 2009 at 03:14 | #41


    tylna os jest skretna i sterowana niezaleznie od przednich kol, poprzez joystick w kabinie kierowcy. Pozwala to na ciasniejsze nawrotki.

  42. Jerzy
    November 14th, 2009 at 20:42 | #42

    Jak to nie widziałeś? Ciągle widuję jakiegoś monster trucka i zauważam że tylna oś (przy tych tak zwanych driftach,w koło) się skręca,ale to również może wynikać z tego że swoją masą tylne koła się lekko skręcają.

  43. Sariel
    October 12th, 2009 at 23:12 | #43

    Hmmm jeszcze nie widziałem monster trucka z obiema osiami skrętnymi.

  44. Jerzy
    October 12th, 2009 at 19:10 | #44

    tylko spróbuj zrobić tak,aby mu dwie osie skręcały

  45. Sariel
    October 12th, 2009 at 17:13 | #45

    A to czas pokaże, na szczęście koła już mam 🙂

  46. Jerzy
    October 12th, 2009 at 17:09 | #46

    no no ładne zawieszenie,ale czy zdołasz zrobić monster trucka?

  47. Sariel
    July 16th, 2009 at 17:30 | #47

    I have specifically listed where I buy the parts from in the FAQ. Why don’t you read it?
    We have Trials in Poland, Czech Republic and I think France and Netherlands too. I know nothing about Trials is US.

  48. LEGO101
    July 16th, 2009 at 17:19 | #48

    where are the truck trials held?

    are there any in america?

  49. crawlerdude
    July 16th, 2009 at 16:58 | #49

    i cant find any of these parts on pick a brick, do you just collect them from sets or do you get them at some other website?

  50. Sariel
    July 16th, 2009 at 00:07 | #50

    Don’t you think I would mention it if I used one? You can really answer your own question if you just think about it for a sec.

  51. crawlerdude
    July 16th, 2009 at 00:05 | #51

    I am extremely sorry for all my questions, but did you use the return to center steering mechanism for this buggy?

  52. Sariel
    July 16th, 2009 at 00:03 | #52

    Listen. You can easily measure the links yourself or from googled images. And you can easily see the type of the shock absorber used on the photos, unless it’s too difficult for you to look at these. I can’t possibly imagine any simplier explanation on how the floating axle works. You just have to read it. I’m really tired of all your questions that can be answered by simply READING or LOOKING at what’s in front of your eyes or by using the Google for like 5 seconds.

  53. crawlerdude
    July 15th, 2009 at 22:50 | #53

    sorry for all the questions but did you use a hard, soft, or normal spring shock absorber

  54. crawlerdude
    July 15th, 2009 at 22:48 | #54

    one more question, do you know the measurement of the links?

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