Excalibur on The Rail
Inspired by John Coker’s ProRail Base design, is this basic launching base consisting of (3) 36″ legs spread in 120° radius, with a rail (1010 or 1515 from 8020) mounted to a tilting mast. The design is quite versatile, and can be constructed from steel or aluminum, with aluminum being the preferred material. This design can easily be scaled up or down. The original design calls for 3″ square aluminum tubing, and I opted for lighter and cheaper 2″ square aluminum tube. Using simple tools and bolted hardware, this pad is only be limited by the costs of material.
Materials:
Material used for the legs and mast were obtained from Speedy Metals, a metal supplier located on the internet. Based on minimum search criteria, Speedy Metals had the best pricing for materials and shipping. The materils used for the mast brace, and the leg brackets were mainly scrap items located in drop-off materials from work. But these parts are also availble in plate from Speedy Metals. Hardware used to bolt all componets are standard zinc coated nuts, bolts and washers of various sizes obtained from local Home Improvement centers such as Lowes and Home Depot. Later improvements for this pad will be total replacement of all hardware with socket head cap screws in stainless steel. The stainless will have a much higher resistance to corrosion, than the zinc coated hardware currently in use.
I do not have specific deminsions and cad details for my adapted version of John Coker’s original design, as John provides very simple design drawings on his ProRail Base page.
The 2″ square tube was cut to order from Speedy Metals. The mast and leg brackest were cut from 3.5″ wide .25″ thick T6061 plate aluminum. Since welding costs would have proven to have been to expensive for a simple launch pad, I opted to machine the brackets as a bolt-on design. Using a small drill press, the leg brackets were drilled to mount the legs in a 120° stance, and the mast brackest to allow the mast to pivot 15″ off of the ground. Additionaly, extra holes were added to the leg brackets to allow the legs to swing out from the closed to open position, and then retained with nut and bolts for extra rigidity.
Pros and Cons:
- Easy to construct
- Light weight design (using aluminum)
- Very sturdy stable design (low cg)
- Handles 1010 and 1515 rails in 10′+ lengths
- 5° of angle adjustment
Cons:
- No Azimuth adjustment (none needed)
- Needs relatively flat surface to rest on
- Will not accept rods.
- Hard on the knees, all igniter work is done on the down low
There is a lack of detail to this post, as all I have done is adapt someone elses work to fit my needs and budget. This pad can be built so much better than I have done, and it has been built better, by fliers in the United Kingdom, and by many clubs up and down the West coast. That is the beauty of John Coker’s design; it is versatile and scalable. It is one of the most stable point-and-shoot launch pad designs I have ever come across.
See you on the field
Johnnie