Build your own steampunk Lego

[dolittle]

"We're going to show you how to build a south-pointing chariot, an ancient bit of Chinese engineering – out of Lego.

What makes this a neat little piece of steampunk engineering is the fact that if you build it right, the chariot will always point south no matter which direction it travels in, giving you a perpetually correct reference point. And there isn't a single magnet: it's all done with gears. "

Toy-de-force: Build your own steampunk Le

Hope you like it.

Thank,

Noam

[blueShinyApple]

I built one like that two years ago when I was twelve!

[JunkstyleGio]

Cool little gadget.

[DLuders]

Which way is south?

[Big Cam]

I searched the first 3 pages and didn't see this, so enjoy.

Build LEGO compass without any magnets

[smittyfan]

looks interesting....

[allanp]

Looks cool, but why did they add that final stage of gearing down (24t - 40t), would that not make it too slow?

[JunkstyleGio]

Double posting!

The title must be a little confusing

[Alasdair Ryan]

looks interesting....

[The Yellow Brick]

What's wrong ?

[Big Cam]

Double posting!

The title must be a little confusing

Bahh, I knew I should have looked harder, I've requested my thread be merged, thanks.

[Stash2Sixx]

Threads merged.

[rgbrown]

Looks cool, but why did they add that final stage of gearing down (24t - 40t), would that not make it too slow?

No, you need the gearing - this one is a nontrivial exercise.

If v1 and v2 are the speeds that the two wheels are travelling along the ground, then the corresponding rotational speeds of each wheel are

w1 = v1 / r

w2 = v2 / r

where r is the radius of each wheel.

Doing the maths with the differentials, the rotational speed of the crown gear that links the differentials is then given by

wc = 1/4 (w1 - w2) = 1/(4r) (v1 - v2).

The angular speed of the overall chariot is given by

wt = 1/L (v1 - v2)

where L is the distance between the two wheels. So L would have to be four times the radius of one of the wheels for the system to be balanced without additional gearing.

For the depicted chariot, I estimate L to be about 17, and r to be about 3. So the compass wheel needs to be geared down by a ratio 4r/L ~ 12/17 ~ 0.7. The 24:40 gives a gearing down of 0.6 (i.e. the right ballpark). I'm sure if you were to actually measure the distances, you'd find those numbers would be very close.

[rgbrown]

Couldn't resist building one of these for the kids' soldiers and pirates ... this one's been hijacked

http://www.youtube.c...h?v=HE1N58tvg5Y