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Roadrunner Buggy

December 30th, 2008 Leave a comment Go to comments

Small, simple lightweight buggy. Features full suspension and rear axle drive.


Completion date: 20/01/2008
Power: electric (Power Functions)
Dimensions: length 37 studs / width 22 studs / height 26 studs
Weight: 0.86 kg
Suspension: front – independent / rear – dragged axle
Motors: 1 x PF Medium, 1 x PF XL

This project was intended to test what speed can be achieved with a PF XL motor, and additionally I was hoping it could drift a bit. There is a differential with 4 bevel gears in the rear axle (a technique developed by LUGPol user Aro_kal), and the gear ratio accelerates motor’s output speed almost twice. The buggy proved to be fast and manoeuvrable, but a bit too slow and to heavy for drifting (probably in part because of the battery box over the rear axle), unless it was given rear wheels without tires and placed on some tiles instead of a regular floor.


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  1. Sariel
    January 19th, 2013 at 20:47 | #1

    Try Bricklink.

  2. BuggyBuilder
    January 19th, 2013 at 20:37 | #2

    Also, maybe with instructions please?

  3. BuggyBuilder
    January 19th, 2013 at 20:36 | #3

    Can you make another buggy with an xl motor? (I know it’s been long since you did so).
    Otherwise, where can I get an rc motor?

  4. Sariel
    September 9th, 2011 at 21:26 | #4

    Maybe I’ll try it one day, this MOC is long gone.

  5. Dan
    September 5th, 2011 at 05:11 | #5

    might is suggest a forty tooth gear as the driver gear, a 24 tooth gear as a middle gear, and finally an eight tooth gear as the follower gear. This results in ratio of about 1-5.?. This is ideal for speed, and i have already tested it.

  6. Sariel
    April 12th, 2011 at 18:19 | #6

    Well, they come from my brain, where else?

  7. harrison
    April 12th, 2011 at 18:07 | #7

    How do you come up with so many ideas? I’ve started a 8 wheel off-road buggy.(remote controlled) please let me know where your ideas come from,thanx

  8. jake greene
    March 16th, 2011 at 04:55 | #8

    thanks sooo much!

  9. Sariel
  10. Jake greene
    March 15th, 2011 at 08:39 | #10

    Where did you get the rpm counter on the back? I need on really badly! Well I don’t need it but I’d love to get my hands on one! Some one email me where to get one I’m jakerox360@gmail.com plz help! Thx

  11. April 13th, 2010 at 21:12 | #11

    fa veramente schifo, è una vergogna per il LEGO. E’ bruttissimo

  12. Mihály Stépán
    February 13th, 2010 at 21:01 | #12

    And with bigger steering lock.. 😉

  13. Mihály Stépán
    February 13th, 2010 at 20:59 | #13

    Maybe the car could drift if there was minimal load on the rear axle (as you said), and using 20×30 wheels, or 24x… dunno, but those with the hard, rigid tyres. If I had pf stuff, i’d give it a try for sure! 🙂

  14. OlSom
    March 19th, 2009 at 19:13 | #14

    should have tried before asking -.-

  15. Sariel
    March 19th, 2009 at 16:04 | #15

    Friction holds it there, nothing more. The trick is to insert the last 2 gears into the differential at the same moment, meshed together. Try, and you’ll surely work it out.

  16. OlSom
    March 19th, 2009 at 16:01 | #16

    I dont really understand how the differential is working. What holds the 4th bevel gear in position? Could you please explain, as it seems to improve the differential’s durability, and i have broken some (2) bevel gears already with an offroad vehicle, so it would be great to have a stronger one. Thanx

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