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Some Lego spaceships have handles attached, made out of Technic beam and pegs, and attached to the model using Technic bricks, pegs, and axles.

For example, 7644: MX-81 Hypersonic Operations Aircraft has a handle on the top (circled below), and the shuttle in 7690: MB-01 Eagle Command Base has a small handle on the bottom side.

A cropped view of the MX-81 Hypersonic Operations Aircraft. The handled, positioned on the top center, is circled in red.

This handle is great for play, transport, and mounting, and I'd like to incorporate this feature into my own designs. However, I don't know what a safe number of pegs and beams is relative to the weight of the model. To be really useful, it needs to support not just the weight of the model, but a reasonable amount of centrifugal force caused by rapid course adjustments as it flies around my living room. Are there official Lego Group guidelines on this, or has someone done a study of the strength of peg-and-beam constructions?

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1 Answer 1

up vote 21 down vote accepted

Tristan Lostroh did an exhaustive test of both studded beams and stud-less beams with and without connections. Here are his results:

  • Studless beams are better in tension than studded
  • Studded beams are better in transverse than studless
  • Studless beams are stronger in transverse with the pins on the side
  • Connections to other components will fail before the beam (Either connections themselves or the connection area of the beam)(IE the (unstressed) centre of the beam will not fail)
  • Pin connections will probably pull apart before they fail catastrophically
  • The more pins, the stronger the connection
  • In transverse 3 pin overlap, with 2 pins used is almost as strong as 3 pin overlap and 3 pins used
  • Beams in transverse conditions won’t fail (but will bend) if the pivot points match the end of the connection
  • Lego is quite strong for its weight

From the report it looks like two beams linked with 5 pins will break at about 57lb of transverse force.

Edit: Just for the fun of it I calculated this 'real life' scenario. Imagine a kid with 40cm arms spinning around a 2lb Lego ship. To create the 57lb of centrifugal force necessary to break the handle he would have to turn at 252rpm. I don't think any amount of sugar can do that.

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6  
If only I could +2 for the edit - I'll ask my boys to try this evening after trick or treating ;) –  Zhaph - Ben Duguid Oct 31 '11 at 9:00
7  
After calculating it, I pictured my kid spinning like the Tasmanian Devil at 252rpm. I was laughing so hard I had a though time typing the edit. –  pcantin Oct 31 '11 at 10:18
    
A nice display of structural strenght is seen on the Millenium Falcon lego set 10179-1 : brickset.com/detail/?Set=10179-1 –  jfyelle Oct 31 '11 at 16:25

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