Saturday, November 16, 2013

An Old Tool Revisited & Snap Bushing Mod

Yesterday’s work session in the shop was brief, but forward progress was made on the RV-12’s fuselage. Early on, a tight fit blind riveting hand tool which takes the place of the AEX wedge was purchased … its initial attempted use was met with little success because of clearance issues at the time … so the tool was thrown back in the tool caddy and more or less forgotten about. While looking in the tool caddy for the ¼” reamer the other day, I ran across the tight fit riveting tool and decided to give it a try once again.
A tool for accessing rivets in tight quarters … provides the same functionality as the AEX wedge, but far easier to align and does not fly off the rivet as the AEX wedge does when the rivet’s mandrel pops.
The F-1212 step ribs previously secured with Clecos were riveted in place yesterday onto the F-1203A bulkhead using the rediscovered riveting tool. Clearance issues were not a factor  this time around, so the tool worked great! … just place a small bend on the rivet’s mandrel as usual, set the tight quarters tool on top of the rivet head, place the rivet puller on top of the tool and set the rivet. One thing I liked about using the tool is after the rivet’s mandrel breaks, there is about ¼” of mandrel in the tool so it does not just fall away like the AEX wedge does. One would be amazed at how much time has been spent searching the shop’s floor for the AEX wedge after it falls away when the rivet’s mandrel breaks.
Tight spot riveting aid in place on a rivet with the rivet puller in position.
With the aid of the tight spot tool, a pop rivet is being set which will permanently attach the F-1212 step rib onto the F-1203A bulkhead assembly.

After all the F-1212 step ribs are riveted onto the F-1203A bulkhead assembly, the F-1202A bulkhead is secured in place on the forward flanges of the F01212 step ribs using Clecos. The F-1202A bulkhead is not riveted in place at this time … the plans instruct the builder to install grommets in various bulkheads and skin components at other locations.
Securing the F-1202A bulkhead onto the forward flanges of the F-1212 step ribs with Clecos.

Following a tip from one of the builders on theRV-12  Forums, the two SB-500-6 snap bushings were filed prior to instillation. Basically, the fuel line which goes into the bushings is just about the same size as the bushing. The issue is major friction … when the bushing is installed into a bulkhead hole, the little fingers on the bushing are compressed inward. The clearance with the fuel line is so tight that the fingers are pushing on the fuel line which creates a bunch of drag, making the fuel line very difficult to install. I cut off a very small piece of the fuel line and could instantly recreate the problem by just slightly flexing the grommet’s locking fingers inward, it was very hard to move the fuel line in the bushing.

The solution is easy, just place the bushings in a vice or clamps and compress the fingers inward and file a some material off. It is not necessary to remove everything just enough to let the fuel line move in the bushing with a little drag.
Photo of the Heyco SB-500-6 snap bushing prior to filing the fingers down.
Photo of the Heyco SB-500-6 snap bushing after filing the fingers down a little.

Filing the two bushings down worked great … after locking the bushings in place, the small piece of fuel line was placed into the bushing’s hole and although there is still a little drag, the fuel line was easily slid fore and aft. This will make the fuel line instillation go much faster to be sure. After the fuel line bushing issue was sorted out, the remaining assortment of various sized bushings were installed per the instructions.