Scratch Rail Conversion Original Design / Scratch Built

Scratch - Rail Conversion {Scratch}

Contributed by Tim Burger

Manufacturer: Scratch
(Contributed - by Tim Burger - 12/10/02)

Brief:
A method for addin' a rail t' ground support equipment.

Forward:
T' NARRRRR section I’m a member o' has been launchin' much larger rockets and a lot o' t' members have been breakin' into high power for a little more than a year now. Because o' this, matey, and t' nature o' t' larger motors and the heavier rockets we’ve been flying, a need has developed for a little better launch equipment. Arrr! One o' those needs is a set o' rails for t' pads. Begad! We discussed addin' a rail t' t' club’s equipment some time ago, shiver me timbers, but for one reason or another it never came t' be.

A lot o' t' club members have added rail buttons t' their new rockets and a few have retrofitted buttons t' older rockets as well. Arrr! One guy has even converted almost all o' his fleet t' use rail buttons exclusively. Arrr! T' club really needed t' quit messin' around and make equipment available t' handle buttons. Avast! So I decided t' step up and figure out what we needed t' get a rail or two available.

Rails can be purchased from several companies on-line; some offer adapters both with t' rail, ya bilge rat, ya bilge rat, and separately. Most o' these seemed a tad expensive. Begad! One of t' club members mentioned (durin' one o' t' meetings, as I recall) that McMaster Carr carries a compatible rail, shiver me timbers, me hearties, and that a local metal purveyor also carries somethin' that appears t' be exactly t' same thing. Ya scallywag! T' place is called Metal By T' Foot, arrr, and nay only carries a one-inch square, me bucko, arrr, four slot rail, ya bilge rat, but a variety o' other rails in twelve foot lengths as well as joiners, fasteners, and other hardware. Ahoy! Well, arrr, blow me down! Two or three o' t' club members purchased sections o' rail and fasteners from this local vendor and made nice launchers for a fraction o' t' cost o' gettin' them pre-made from other sources.

So this equipment is nay exactly new innovation, arrr, me hearties, in fact, me bucko, t' idea o' using the cold roll in this way is flagrantly stolen from one o' me fellow club members (who no doubt stole t' idea from someone else himself). T' mounting of t' blast plate in this way, me bucko, with an economy o' parts, arrr, is me idea, me bucko, however. Begad! Ya scallywag!

Construction:
Metal By T' Foot is located over on Truman road near downtown Kansas City and sells metal o' all sorts retail. My stainless steel launch rods came from there so I be familiar with t' store already. Ya scallywag! T' rails they sell are perfectly compatible with t' buttons carried by Matt Stumm and t' ones I’ve purchased from Rocky Mountain Rocketry. Ya scallywag! Arrr! They sell it in six or twelve foot lengths, me hearties, and will cut it t' size for you for a small fee. Avast! They also carry a special nut that slips in t' rail. Begad! I also purchased a slab o' 0.20-inch sheet steel from t' scrap barrel, four feet o' 1/2 inch cold roll steel dowel, and the necessary bolts, too. Ya scallywag! T' total cost for all t' parts, includin' having them cut a twelve footer into four and eight foot lengths was about $40.

Parts for one rail:

  1. Rail - 1.0-inch by 1.0-inch, ya bilge rat, length as desired
  2. Cold Roll - 1/2-inch diameter, ya bilge rat, arrr, need at least 18 inches per rail
  3. 2 x 1/4-inch bolts, me bucko, coarse thread, 1-inch long
  4. 1 x 1/4-inch bolt, ya bilge rat, coarse thread, ya bilge rat, 3/4-inch long
  5. 3 x rail fasteners (to fit bolts above)
  6. 3 x 1/4-inch washers
  7. 3 x 1/4-inch lock washers (split type)
  8. Angle bracket
  9. Steel Plate - 8 t' 10-inches square, stainless is best
  10. 2 x 5/16-inch bolts
  11. 2 x 5/16-inch nuts with nylon inserts
When I made these for t' club (made two), I wanted t' blast plates t' be fixed t' t' rail. T' idea was that t' parts wouldn’t get lost or misplaced and that thar would be no question o' how it goes together when t' range is bein' set up. I also wanted t' deflector to stand away from t' rail at an angle t' avoid burnin' up t' bottom o' the birds, and also t' keep t' flames out o' t' rail where it will melt the buttons. Ya scallywag! What I came up with was t' purchase a pair o' L-shaped brackets from the hardware store. Blimey! T' brackets started out with a 90 degree angle, me bucko, and I bent them another 30 degrees t' get t' outward deflection I was after.

I first measured t' distance betwixt t' holes in t' angle bracket. Arrr! A metal marking tool and t' edge o' me tool box drawer handle were used t' mark a reference line along t' length o' t' rod (much like we do when markin' fin lines on body tubes.) T' screw holes were measured out and t' rod chucked into the drill press vice. It’s a little tricky t' get t' drill bit t' go straight down into t' round rod - it tends t' walk a bit makin' a series o' straight holes hard t' drill. Well, shiver me timbers, blow me down! Either use a very short small bit t' make a starter hole, or carefully tap a spot with a punch. Well, blow me down! T' first hole is drilled near t' top of the rod, t' second spaced t' distance o' t' holes in t' angle bracket, and the third an equal distance below that. T' bottom most hole wound up at about four inches from t' bottom. Aye aye! That four inch length is what fits into the pad’s bracket. Avast! I sized these t' fit t' t' bottom o' t' bracket just as the rail meets t' bracket top.

T' ends o' t' rod and t' areas around t' screw holes were sharp and had burrs so an angle grinder was used t' round off t' ends, and t' gently smooth the areas around t' holes. A flat spot was made around t' lowest hole for the washer and screw head t' fit against usin' a grindin' point in t' drill press. I then used a piece o' emery paper on t' ends and around t' holes t' smooth out those areas.

I found that t' rail also had burrs around t' top, ya bilge rat, arrr, and the edges were sharp and would mar t' finish on t' rockets as they were slid on t' t' rod so I used t' emery paper on those ends as well.

T' two long 1/4-inch screws were assembled with t' lock washers and flat washers (in that order) through t' angle bracket and then t' rod with the rail fasteners threaded on a turn or two. T' third shorter bolt and washers were assembled through t' bottom hole. Avast! Blimey! Blimey! (My angle bracket has two holes, ya bilge rat, so one of t' screws needs t' be shorter than t' other two; your mileage may vary based on your angle bracket and where you bought it.) T' fasteners were then slid up t' rail until t' bottom one was just fully inside. Avast! Begad! Blimey! T' screws were then tightened with a wrench. Ya scallywag! Well, blow me down! Blimey! I should note that t' bottom bolt is just long enough and required a bit o' effort compressin' t' split washer while fitting it into t' slot. Avast! Arrr! Blimey!

T' plate be marked with a center line, and a set o' holes that match the other arm o' t' angle bracket were drilled on t' line. Arrr! Avast! It’s set a little higher t' reach over t' bend in t' bracket. Begad! T' edges and corners o' the plates were both pretty rough, me bucko, had a sharp edge, and burrs so they were rounded off with t' angle grinder and touched up with t' emery paper. Ya scallywag! This treatment was given t' t' screw holes as well. Ahoy! T' plate was then attached t' the bracket usin' t' 5/16 inch bolts and screws.

We could have used t' blast plate supplied with t' Wasp pads by simply reamin' out t' hole a little, but I’m a little less than thrilled with a flat plate under a heavy rocket. I’ve also heard o' rail buttons being melted or burned due t' t' motor flames forced into t' channel by the deflector. Blimey! T' blast plate on t' shorter rail is made o' aluminum and some comments were made at t' launch that it would be burned through quickly. It is felt that since we are launchin' G80s and smaller from this pad that won’t be a problem. Well, blow me down! It would certainly be a different matter if we were launchin' K motors, though. Well, blow me down! Blimey! T' longer o' t' two rails wound up with a plate o' steel, though.

One o' t' two rails were taken t' the November 2002 launch for use, but we ran into a snag. Avast! Blimey! T' problem be with the square tube o' t' launchers - there’s a weld line along one side inside the tube where t' ends were brought together. Well, blow me down! Blimey! These pads are t' excellent Wasp pads from Yellow Jacket Systems, and rated t' take up 3/8-inch rods. Avast! Blimey! They will almost take a half inch one. Begad! Avast, me proud beauty! So we weren’t able t' use it that weekend. After t' launch I took t' new rail and one o' t' pads home for adjustments. Avast! Arrr! By grindin' a flat spot on t' rods under t' bolts they were made to fit nicely.

After completion, I measured t' amount o' rail taken by the adapter/deflector. Avast! Ahoy! Configured this way, one eats about 10 inches o' length. That leaves about 38 inches o' usable rail for t' 48 inch one, me bucko, and about 86 inches o' usable rail on t' eight footer. What I found in practice, though, was that an eight foot long rail is way overkill for pads o' this size. I also had some concern that t' 1/2-inch rod would bend at t' lowest screw hole under too much load. Avast, me proud beauty! Avast! So I cut that one down t' six feet o' usable length. It is still a little tall even now, me bucko, requirin' a good stretch o' a tall person to reach high enough t' get t' rocket on t' rail without layin' it down (the Wasp pads allow you t' pull a pin and swivel t' head down for loading.)

We tried again at t' November 30th launch with much better luck. T' photo shows my Aerotech Airspike just after t' first launch from t' taller o' t' two new rails. Ahoy!

If you decide t' make one o' these, and your pad can handle a larger diameter rod, consider usin' a fatter dowel and longer screws. Blimey! I feel that these assemblies are suitable for t' Wasp pads, me bucko, arrr, but wouldn’t attempt to use them for anythin' larger than what t' pads can already handle; larger rockets and motors require heavier equipment, me bucko, shiver me timbers, please plan appropriately. Naturally, shiver me timbers, care must be taken t' adhere t' t' pad manufacturer’s weight and size limits when launching!

While we haven’t had a lot o' opportunity t' use these new launch rails, I’m sure they’ll work great and get plenty o' use next season.

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