DIY Bridge

[Mad Mike]

Can you make a bridge to cross a 20 foot gap if all you have are some 8 foot poles?

Just to make it interesting no fixings or cordage allowed.Also no piers or middle supports

Bridge :werd:

Testing Testing

This one has 6 sections (I think) I put up 4 or 5 sections alone (with others watching)
got help from one other for the last bit as it was getting rather heavy.

This was at the last Kent meet went back & took pictures on Friday as we had all left our cameras at home.

Mike

 

[Jodie]

a) How on earth did you achieve that?? I've never seen anything like it.
b) Could you do it if there was an abyss between one side and the other - ie. can
you 'thread' the bridge over from one side to the other so it can reach the other
side 'by itself'?
c) Is there some scaffolding involved that you've removed before taking the photo?

It's a bit clever

 

[Shewie]

Very clever indeed, I`ve read about that before somewhere, I think it`s called the da vinci bridge if I`m not mistaken.

 

[spamel]

The chinese used to make bridges like that constructed completely from bamboo.

 

[Aragorn]

that's cool Mike, what sort of weight do you think it would hold, do the poles have to be that length or could the design be made to work with more shorter poles.

 

[twisted firestarter]

Ooh that's very clever Mike

It looks like the same principle as constructing a reciprocating roof although

I have no idea how you get the bridge to the other side without crossing it?

Does it require people on both sides?

 

[loz.]

Linky - as i cant quite see the detail in the photos,

Excellent to have built this live scale !!!

 

[jojo]

Bet you could use the same idea to make a frame for a shelter, should work just as well??:You_Rock_

 

[Stew]

Pretty cool!

 

[Toadflax]

b) Could you do it if there was an abyss between one side and the other - ie. can
you 'thread' the bridge over from one side to the other so it can reach the other
side 'by itself'?

Though this is a slight aside, I always used to wonder how the Royal Engineers would put a bridge across a gap when they couldn't get to the other side - until I joined them (back in the early '80s). And when you see the answer, it's obvious.

Although this is perhaps over-simplifying, you build a lightweight bridge that is twice as long as the gap you want to cross (or you heap counterweight on your end of the bridge to stop it dropping into the gap) and you then push the bridge out across the gap on rollers placed on your side of the gap. The weight on your end of the bridge stops it falling into the gap. Once the 'nose' has landed on the far side, you take some more rollers across for the far end, build a bit more 'strong bridge' at your end, push it across a bit, dismantle the front of the 'nose' and continue doing this until you have the full strength bridge all the way across the gap.

If you have a look on Wikipedia for medium girder bridge http://en.wikipedia.org/wiki/Medium_Girder_Bridge you will see, among other things, a photo of the lightweight 'launching nose'. The old Bailey Bridge (and its derivative the Heavy Girder Bridge) used a similar method for 'launching' the bridge, but rather than having special components for the 'nose', the lightweight front of the bridge was constructed using standard bridge panels.

If you liked Meccano, you would have loved the army's girder bridges.


Geoff

 

[Mad Mike]

I have posted some photos of my model of the bridge
Here

to answer some questions

No scaffolding was used
You have to enter the ditch/river to construct
I have seen a diagram of building it with thin long planks underneath
the idea it to pull the completed bridge across the ditch
sounds like a good one for the bushmoot

No reason you cannot use this for a roof support

 

[Ben Trout]

We managed to get our Scouts to build one. Cheated a bit and lashed two 'ladder' frames for the ends and not as many sections.

Yours is very impressive, I've seen drawings of them plenty of times but very few photos!

 

[Ben Trout]

S'rry, back again. Just noticed the other gallery pictures. When I run pioneering activities I like to make a model as it gives a much clearer idea to the group what is required. In preparation I built a model with some 300mm by 25-30mm diameter hazel and that was strong enough to stand on. Have you loaded up your model to it starts to creak?

 

[fishfish]

a while ago i saw a self supporting bridge of a similar idea built on telly,i think it was in an asian country,it used over 100 bamboo poles and again no lashings!

 

[match]

I've helped someone build a rope bridge before which was fun -can't find any pics of it, but having looked online it was something very similar to this one:

http://glenn.cockwell.com/scouting/scouting_rope_bridge.html

Only downside is you need to carry a lot of rope, whereas the Da Vinci design can be made from locally sourced materials.

Does anyone else have any plans or designs for temporary/bushcraft bridges?

 

[StormCrow]

Hello,

someone sad something about Chinese.

I know that the Rainbow bridge is built that way. except bigger.

In my physics class we had a bridge contest with little balsa wood bridges and I built that one.

 

[Mad Mike]

Found the link

Here

Looks very good