For those familiar with the traditional Double A-Frame Monkey Bridge design, a couple of noticeable modifications will be apparent from the outset. (Click on the photos for larger views.) Scout Engineering is a fluid undertaking, and frequently variations are necessary. Just as frequently an alteration or change can be deemed a desirable improvement. In the case of this double A-frame design, the consensus of opinion is these modifications are really neat, and I’m sure Adolph Peschke would concur.
Instead of separate shorter ledgers for each pair of adjoining A-frames, connect four legs with one longer ledger. The length can actually be the same as that of the legs, e.g. four 8-foot legs and one 8-foot ledger at the bottom, or for a larger structure, 10 or 12-foot legs and ledger. (A spar longer than the legs does yield more flexibility when lashing together the four legs.)
Ladder rungs! Lashing a couple of cross pieces between the legs of the left A-frame cancels the need to climb on board the bridge using the foot and hand ropes! Same thing of the other side. Crossers use the rungs and have a safe and easy way to get on and off the bridge, AND eliminate the often awkward balancing act on the ropes between the A-frames and the anchors. There’s an added advantage too: no more excess stress and strain on the ropes near the anchors.
The bridges featured in the pioneering area of the 2013 National Jamboree were a modified Double A-Frame Monkey Bridge, a specially designed pre-stressed triple walkway bridge, and two Single A-Frame Bridges that Scouts could put together from a couple of kits we supplied.
Single A-Frame Bridge Building. The kits we supplied for the construction of a Single A-Frame Bridge afforded crews an opportunity to build their own simple crossing bridge. Each group’s success was gauged by how they all could use it to cross the ditch and then all stand on it and pose for a group photo. So the activity wouldn’t be too time consuming, the walkway subassemblies were pre-made. Click here for photos of the crews.
Prestressed Triple Walkway Bridge. The most sophisticated and by far most substantial bridge erected up on Garden Ground Mountain on the occasion of the 2013 National Jamboree was this well-designed prestressed bridge. Without getting technical about compressive forces and tension and stress mechanics, suffice it to say the bridge was impressively well-built and strong. Click here for information and photos.