Porsche Boxter & Cayman "hidden hitch" adapter for utility trailer

thingiverse

Posted are detailed models and dimensions to create a "hidden hitch" mount for Porsche Cayman and Boxters. This is reverse engineered from images posted on the planet-9 site and measurements taken from self-locking ball mounts made by www.etrailer.com. I took precise measurements from 2" hitch components at Home Depot to verify tolerances of the square receiver hole. Having a spare bumper channel on hand allowed me to measure its features. Along the way, I 3D printed a full-size sample in PLA to check fit and clearances before finding a shop to cut this out of a block of 6061 aluminum. For those who have never turned a wrench or touched a hacksaw... ***This design is for steel or aluminum.*** 3D printed plastic is fine for testing fit and concept only! The STL serves CNC users with access to software like CAMWorks that can read features & surfaces from "dumb-solids," while the dimensioned prints serve those who have access to manual milling machines or know how to enter a design into a CNC milling machine controller. **** This is an at-your-own-risk design. Towing a trailer can be hazardous, and you must assume all responsibility for manufacturing, installation, and use of the design. The set of parts created for a single Cayman worked and has been proven road-worthy on many trips to the track, but the installation continues to be inspected before and after every use to ensure it's safe. If you can't assume risk for this design, then don't use it. **** http://www.planet-9.com/reviews/cayman-cosmetic-mods/p285-behind-the-box-solutions-hidden-hitch.html It would have been impossible to realize this without the information provided in the planet-9 posting. Several revisions were necessary to eliminate challenging machining geometries, and the process caused several gut-check moments on cost to machine, feasibility, and safety. Along the way, I found an off-the-shelf less fancy version in steel that uses a more traditional ball adapter currently available at: https://picclick.ca/SporTTows-Stealth-Hidden-Hitch-Porsche-911-272908016681.html#&gid=1&pid=3 Very late in the process, we found a manual for the original design sold by "Behind the Box Solutions" and it included several pages of legalese disclaimers. It's believed that liability and profitability of this design and devices similar are significant issues. In our case, we chose to recreate the no longer available "Behind the Box Solutions" because it was the cleanest design. Buying pre-made would have been preferred, but that wasn't an option. My version is surely different, but it works and installs the same using notes from Planet-9. So if you've gotta have this style adapter, here are some details that will help: * The two mounting bolts are 3/8"-16tpi. * Holes in the models account for the root or tap diameter in the part that goes inside the bumper channel and major diameter of clearance holes required by the outer block. Your machinist should modify hole diameters as needed for the correct etrailer self-locking ball mount. The originals shown in the planet-9 posting are beautiful, but I chose to drop all chamfers and forego anodizing to reduce cost. My models aren't as pretty to look at or handle, but they work... and once installed, it's unlikely a sharp edge will hurt you. We chose an aluminum trailer for weight and corrosion resistance. It is an Ultra-Tow 40"x48" trailer from Northern Freight with many mods to accommodate tire and tool box mounting. If you choose the correct etrailer self-locking ball mount, your trailer will be level when ready to roll. The 12" tires provided with these trailers are not rated for highway speeds, but other Porsche owners with small trailers report they've had no problems at highway speeds. Keeping the trailer and load light likely helps keep these wimpy tires from being a major issue. Be sure to travel with a spare wheel ready to bolt on. **** This is an at-your-own-risk design. Towing a trailer can be hazardous, and you must assume all responsibility for manufacturing, installation, and use of the design. The set of parts created for a single Cayman worked and has been proven road-worthy on several trips to the track, but the installation continues to be inspected before and after every use to ensure it's safe. If you can't assume risk for this design, then don't use it. ****