Chuck, here is the STL for my rail adapter.
The components are the top plate made of .25"x1.5" aluminum flat/bar stock, the thicker vertical bar is made from .75"x1.5" aluminum flat/bar stock both pieces are 2.5" long.
The sides are marked A-D
A) is the top where the 1515 would sit, the two countersunk holes are for #10 machine screws, the center hole is the one for the 5/16-18 bolt/machine screw that goes up to the washer that slides inside the 1515 rail (on the D side it is counterbored enough to get whatever length fastener you want). The flanges under side A sit on top the Unitstrut.
B) is the side, dowel E is a .25 steel peg that goes all the way through and the length can be adjusted to fit inside the Unistruts vertical outer sides dowel E has a set screw from side D (forgot to put the set screw in the STL) that locks it in position. The large hole (in this case .375") is for a 1/4" pin that goes through the Unitstrut and the Adapter shoe to lock the rail into the unitstrut, only one of these holes is needed in the shoes (my pin for our Padzilla is a 1/4-20 bolt of the appropriate length with a hole drilled through the end for a spring clip aka hair pin) removing the bolt/pin allows the whole 1515 to slide out of the Unistrut.
C) nothing fancy about side C, the shadow line/cut just below the wide portion is just there to represent the fact that's where the two aluminum pieces meet.
The tools used for this project were:
A Makita 10" Power Miter saw with 10" carbide tooth blade (a finish blade iirc)
Drill Press
#10-24 Taper tap
#10-24 Bottoming tap
#6 or #8 set screw for steel dowel
Tap wrenche or wrenches to match taps
Drill bits to match all taps
Drill bit to counter bore the 5/16-18 socket head cap screw head diameter (Counter bore done AFTER the 5/16" through hole is drilled).
IIRC I attached the top plate to the vertical piece prior to cutting it into individual adapter shoes since the long bar is easier to handle than a bunch of 2.5" long adapter shoes, then cut them apart after all holes were drilled and tapped and the top plate and vertical bar were screwed together. Dowels were cut inserted and set screwed in place as a last step. The shoes should have a small amount of movement in the Unistrut since if they fit too perfectly....well lets say rails get dirty....
The reason the 3/8" hole is larger diameter than the 1/4" retaining pin is that it makes it easier to change especially if the adapter shoes is ever so slightly twisted out of line with the rail for whatever reason. Pulling the 1/4 Pin is all that required to change rails, super easy and very quick, pull pin, slide out one rail, slide in a different rail, replace pin, done, no tools, and all in less than 30 seconds. The whole pad is actually designed to require no tools to operate. If we wanted to put a 25' Unistrut on the pad with tie downs that would require tools as it would have to replace the current 10' Unistrut rail and the pads rail arm would need to be extended ( Padzilla is a Coker style pad made of .083 wall 3x3" Steel tubing.
I made 5 shoes for the 1515 rail which is 12' long (a 4' and a 8') the Unistrut on our pad is 10' since its being used as a receiver rail for the 1515 and 1010. I also made 4 shoes for the clubs 12' 1010 rail the only differnce for those shoes is that the 5/16-18 socket head cap screw hole is a smaller size to fit the proper fasteners for attaching the 1010 rail.
Edits....all parts that are not aluminum are stainless steel.
Hope this helps.
