Tag Archives: pioneering activities for scouts

Single Lock Bridge

CLICK HERE FOR COLOR PHOTOS, COMMENTARY, AND SOME FURTHER GUIDELINES ON BUILDING A SINGLE LOCK BRIDGE.

Single Lock Bridge Photo Scanned from 1967 Field Book
Single Lock Bridge Photo Scanned from 1967 Field Book

Link to: Older Pamphlet InfoThe following text is by Adolph E. Peschke as presented in the 1998 printing of the 1993 edition of the Pioneering Merit Badge Pamphlet:

The single lock bridge shown here is a well-established and basic design. The list of spars shown for this project should build a bridge to span a creek or ravine approximately 4 feet deep and 18 feet from bank to bank.

Trestles. The bridge consists of two trestles and two walkways. Begin by building the two trestles as subassemblies. Adjust the length of the spars for the trestle so that when they are placed in the creek, as shown in Drawing 2, the tops of the ledgers will be about 1 foot above the level of the banks of the creek. This will give a comfortable slant to the walkways.

Drawing 1: Trestle Schematic
Drawing 1: Trestle Schematic

When constructing the two trestles, build only one trestle first. Then as the second trestle is being built, make sure that the legs are narrower at the top and fit between the legs of the first trestle (see Drawing 1).

Walkways. Next, the two walkways are constructed as subassemblies. Each walkway consists of two lateral spars. six cross spars, and two longer cross spars. One of these two longer cross spars is used as an underspar at the end of the walkway that is attached to the transom. The other longer cross spar is used to attach to the stakes. (Refer to Bridge Walkways.)

Interlocking Trestles
Drawing 2: Interlocking Trestles

Assembly. After building the trestles and walkways, take them to the assembly site (the creek or ravine). Place the trestles in the center of the creek so that the tops of the trestles are interlocked (see Drawing 2). Then lift a 3-inch diameter transom spar to fit on top of the interlocked trestle legs.  Now, heel in the bases of the legs in holes 4 to 6 inches deep. As you’re heeling in the legs, level the transom spar so that the walkways don’t slant when they’re added.

Next, the two walkways are put into position (see Drawing 3). Lash the underspars on the walkways to the transom spar with Strop Lashings at three points. Finally, the cross spars at the ends of the walkways are lashed to the stakes.

By lashing the walkways to the transom spar and lashing the ends of the walkways to the stakes, you make a complete walkway unit that will prevent movement and provide a sturdy bridge deck.

Drawing 3: Fully Assembled Single Lock Bridge
Drawing 3: Fully Assembled Single Lock Bridge

List of Materials for a Single Lock Bridge

  • four 3-inch x 6-foot trestle legs
  • four 2-1/2-inch  x 4-foot trestle ledgers
  • one 3-inch x 4-foot trestle transom
  • four 2-inch x 6-foot cross braces
  • four 3-inch x 10-foot walkway lateral spars
  • twelve 2-inch x 3-foot walkway cross spars
  • four 2-inch x 3-1/2-foot walkway cross spars
  • two 2-inch x 10-inch x 10-foot walkway planks
  • four stakes

CLICK HERE FOR COLOR PHOTOS, COMMENTARY, AND SOME FURTHER GUIDELINES ON BUILDING A SINGLE LOCK BRIDGE.

Double A-Frame Monkey Bridge

—> EXPLANATIONS, DETAILED INSTRUCTIONS, AND ILLUSTRATIONS!

—> EXPLANATIONS, DETAILED INSTRUCTIONS, AND ILLUSTRATIONS!

On November 14, at the Chicora District Webeloree, (gathering of 4th and 5th Grade Webelos Scouts), a crew from Troop 888 put up the troop’s eighth Double A-Frame Monkey Bridge. The event was geared mainly towards those Scouts who hadn’t yet had a hands-on experience assembling a bridge. Scouts gathered at 8:30, and the bridge was ready for a test walk by 10:00 a.m. Lending a hand were: Ian Baker, Dominick Bezmen, Geoff Britzke, Will Hall, Jason Hardee, Daniel Mesich, Sam Snodgrass, and Greg Spatholt. The following steps went into building the bridge: Scouts lash together two 8ʼ spars and one 6ʼ spar to form four A-Frames, Two A-Frames are joined together to form each side of the bridge. The Double A-Frames are held up in the proper positions and at the right distance. Two Hand Ropes and one Foot Rope are tied on and anchored at either end. Spanner Ropes are added to the Hand Ropes and Foot Ropes. The Monkey Bridge is tested and adjustments are made as necessary. Scouts supervise Webelos interested in crossing the bridge. The bridge was able to support a 270 pound adult! Lashing and knot-tying savvy are important in any large pioneering project, but teamwork is the key. A 14’ Double Ladder Tower is scheduled for Feb.

—> EXPLANATIONS, DETAILED INSTRUCTIONS, AND ILLUSTRATIONS!

FOur and a half years ago we studied the plans for a Double A-frame Monkey Bridge in the Pioneering Merit Badge Pamphlet. Four and a half years later, we're still using the same pine spars cut from behind the house and putting up bridges on selected camping trips and Scouting events. The lashings and methods we learned are constantly being passed on to new Scouts. The techniques are the same but with some slight improvements. Like a sheer lashing is tied to the tops of the A-frames instead of a square lashing. And after this last bridge, we're now frapping the strop lashings on the bottom when lashing the two A-frames together. This makes them real tight. After four and a half years, the bridges are still as much fun as ever, and with moe advanced teamwork and sharper skills, they're going up a whole lot faster too. Our SPL goes through the ticky process of lashing two A-frames together where the 8 foot spars cross. The A-frames are steadied as the hand rope is attached with a clove hitch on each side. The bridge is tested before the final tightening of the hand and foot ropes. The bridge went up in about an hour and took ten minutes to take down.

—> EXPLANATIONS, DETAILED INSTRUCTIONS, AND ILLUSTRATIONS!

Double A-frame monkey bridge (Our first Built with Laminated Spars) Square Lashing an A-frame corner, joining together the bottoms of two A-frames with round lashings, adjusting the clove hitch on a spanner rope as Scouts wait their turn to cross the bridge, crossing the fully assembled monkey bridge on a camping trip.

—> EXPLANATIONS, DETAILED INSTRUCTIONS, AND ILLUSTRATIONS!