Construction is pretty straightforward. Use a 1/4" drill bit. It helps, once the bit is through the wood, to hold the drill in place and run it in reverse to clean out the hole. Then run a bolt through by hand a couple times to finish cleaning the hole.
Next, put the bridge floor onto the bolts:
There is a bit of a challenge aligning the drill holes exactly with the bolts. We (Daniel and I) accomplished this by first setting the bridge floor exactly in place, then using a hammer against a block of wood that was placed on the bridge floor directly over the rightmost bolt. The block of wood protected the top side of the bridge floor from dents, but the hammer (only one hit) caused the bolt to put minor indent in the bottom of the bridge floor. This indent was our guide for the 1/4" drill bit. Repeat 4 times, cleaning the hole each time, and voila!
We didn't set the levels of the support washers yet. Instead, I started on the supports for the loop end of the bridge. I cut and measured the pieces then started assembly. First, we need a cross joist. I reused a piece of 1/2" plywood from the first staging attempt. This works except plywood is susceptible to splitting, as this photo shows:
Fortunately, the split is minor so replacement was not needed. Next, I set up the bridge beams on top of the floor to figure out best placement. This is needed to calculate where the support tiers below should be placed:
Next, piers are cut based on the measurements taken in the photo above. Then the task is to get everything to hold together in place before attaching them permanently. This photo below shows the support tiers held in place with C-clamps. The beams are resting on top, unattached, and resting on top of them is a small piece of scrap lauan plywood (not the bridge floor, but the same material). In this photo everything is in an approximate position, prior to measuring and adjusting:
In the next step everything is in place and level in all directions:
Now to fix the support piers in place, starting with the support pier near the middle tier tracks (on the right). This is the standard procedure of drilling pilot holes then 1/4" dry wall screws. Access is difficult, so the drill holes are at an angle but still effective. Alas, there was a slight slippage down on the right side of the pier when I was drilling the right screw hole. Rather than redo it with another drill hole I added a single plastic shim under the right end of the joist, and by raising the joist on that side the pier tops were returned to level:
For the other support pier I found it impossible to position a drill for setting up a pilot hole given the crowded surroundings. However, the rest of the structure was, at this point, very rigid. So, I took the C-clamp off, applied wood glue between the pier and the lower joist, then re-clamped and re-leveled. A few hours later it was strong enough to take the clamp off and drill a pilot hole and a single screw.
The next post will pick up with the support on the other side of the bridge.
No comments:
Post a Comment