EMRR's Scratch: Inexpensive Rail Launch Pad

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REV 2.4 - Fri Jun 17 20:14:52 2011

Scratch
Inexpensive Rail Launch Pad

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(by David Logan)

Scratch - Rail Launcher Brief:
An inexpensive solution for a rail pad using the 80/20 rail. Made of a combination of PVC and metal pipe, using nothing but a hack saw, a drill, and a Dremel. This pad should be able to handle any Level 1 flight.

Construction:
Parts list:

Three 5ft lengths of SCH40 PVC pipe (one 10ft and one 5ft would be cheaper).
Two 1 1/4" PVC Tees
Two 1 1/4" to 1" PVC Bushings
One 1 1/4" PVC Cross
Four 1 1/4" elbows 45 degree
One 1" x 8" metal nipple
One 1" metal T
One 1" x 6" metal nipple
Two 3/8 x 2" clevis pins
Two hitch pin clips
One 5/16 turnbuckle set (get the set with eyes at both ends)
Four 1/4-20 x 1" carriage bolts
One box of 1/4-20 washers
One box of 1/4-20 locking nuts
Two flat corner braces
One 1/4-20 wood insert nut
One 1/4-20 x 1 1/2" thumb screw
Two 3/8 x 1/2 x 1 1/2" steel spacers
One 3/8" x 2" hex head bolt with locking nut
PVC Cement

Scratch - Rail Launcher My first order of business was gluing the 1 1/4" to 1" PVC bushings into the PVC cross directly opposite each other. Next, I sanded the inside of the bushings until the 8" metal nipple was able to slide through the cross, keeping the fit snug. Once that was done, the 8" nipple was cut into a 6" section, and a 2 " section. These were then screwed into each end of the metal tee. Now screw the 6" nipple into the side outlet of the tee. It was now time to fit the L brackets to the rail, and shim them to fit length wise on top of the 2" metal pipe. Once it was shimmed to fit, a 3/8" hole was drilled through the 2" section at a 90 degree angle to the side outlet of the tee, and the L bracket rail assembly was attached using the 3/8" x 2" bolt and lock nut. This creates the hinge for the rail. Next I cut a notch into the top of the open end of the 6" nipple, and drilled the holes for the turnbuckle attachment. In each end of the turnbuckle, drive one of the steel spacers into the "eye". These will need to be cut to fit one between the two L brackets, and one inside the 6" nipple at the notched end. Place one end of the turnbuckle assembly between the L brackets at one set of holes, and insert a clevis pin and hitch pin. Place the other end of the turnbuckle into the slot in the 6" nipple and insert the other clevis pin and hitch pin. This completes the hinge and altitude adjustment assembly.

Scratch - Rail Launcher For the base, dry fit all parts first and mark their locations!! Cut four 30" long sections of 1 1/4" PVC pipe to make the legs. Cut six pieces, 2 1/4" long to be used to join the fittings together. Now dry fit all of the pieces together, starting with the cross. Place a tee at each end of the cross (without bushings). At each end of the tees, place an elbow. Insert a leg into each elbow. This is the tricky part. Get the legs at an angle and height you are comfortable with, making sure to keep the cross level, and the ends with bushings vertical. Mark and number all joints so they can be reassembled in the same positions. Now, one at a time, glue all of the pieces together, except the legs. You will have to be careful lining up the parts as the glue sets up very quickly.

Scratch - Rail Launcher The last step is optional. In one side of the cross, drill a hole, and screw in a threaded brass insert being careful not to get it in too far. Now screw in a thumb screw into the insert and this will allow locking the horizontal adjustment into place.

After all of the glue has set, insert the legs. A small slit can be cut length wise into one end of each leg to make installing and removing easier. Now, drop the rail assembly into the cross, and there it is, a sturdy cheap rail pad. Vertical adjustment is done by adjusting the turnbuckle. The whole rail assembly can rotate in the base for horizontal adjustment. and to load a rocket on the rail, just pull one of the pins out, and the rail can be laid down for loading.

Scratch - Rail Launcher For a blast deflector, a rectangular piece of sheet metal, say 6" x 18", can be bent to form a triangle, and held on the rail with rail buttons. This suggestion is courtesy of Matt Stum of railbuttons.com.

GUEST's OPINION:
08/10 - "Both of you are much better designers than I am. This is not something that I would have ever come up with on my own." (M.K.)

GUEST's OPINION:
01/10 - "I have corresponded with David and personally apologized. I want to post this as a public apology. Clearly David's design was independent and conceived before mine. I am amazed at how similar they are. Funny how wheels begin turning in your head as you walk the aisles at Home Depot." (T.J.D.)

GUEST's OPINION:
01/10 - "T.J.D., I am very sorry if I have offended you and you feel that I copied your design. For what it's worth, my pad was built in 2003, the same year I submitted it here and at The Rocketry Forum. For this pad to be going on it's seventh year of use and abuse, it is still working as designed, it just doesn't look as new." (D.L.)

GUEST's OPINION:
07/09 - "T.J.D., you say that you have been using this design for a few years, but you only published information about it for the very first time in 2008. Although the above article is undated, it was put on this site no later than 2006 because that was when I built my version of the pad based on the information in the article. You imply that the author copied your design for this article, yet how could he have done so if you only published your plan for the first time at least two years after his article was posted here? I can't dispute your claim, but looking at the timeline, one could argue that the design that you posted on TRF was perhaps the one that was not original. This could also simply be a case of convergent design: two designers attempting to achieve the same goal using the same basic set of materials and operating completely independent of each other that end up producing strikingly similar designs." (M..K.)

GUEST's OPINION:
07/09 - "Hmmm... This looks strikingly familiar to a great pad I designed and built back in 2005 (Posted in 2008 here.) I guess scratch doesn't mean original(?)." (T.J.D.)

GUEST's OPINION:
10/07 - "I followed Dave Logan's instructions outlined here and built my own version of this plan, except that instead of using a 4 ft. rail, I installed an 8 ft. rail. The extra mass and leverage provided by the longer rail resulted in a slightly wobbly mount. I fixed this by adding two additional corner braces to each side, so that the rail is held by three stacked and bolted-together corner braces on each side. I did have to install longer bolts for the rail, brace and adjuster attachments because of the thicker braces. The beefed-up bracket holds my 8 ft. rail absolutely rock steady now. Dave's design yields a very sturdy, yet easily transported pad that is simple to modify to accommodate longer rails. The quick release feature that drops the rail down for loading is an especially nice touch, and is one of the most attractive features of the pad. The 1.25" Schedule 40 PVC is amazingly rigid and strong, but is still light in weight, which helps to make the pad easy to set up and take down. I did add a rail-mounted blast deflector that I made by folding a large piece of sheet metal into a right triangle, as described at Matt Stum's site. The only potential con would be that the pad might be a bit lightweight for larger, heavier rockets, but then such rockets probably would not be launching from a 1" square rail anyway." (M.K.)