Scratch Micromaxx Spool Rocket Original Design / Scratch Built

Scratch - Micromaxx Spool Rocket {Scratch}

Contributed by Mark Kulka

Manufacturer: Scratch
(Contributed - by Mark Kulka - 12/01/08)

scratch_micromax-spoolBrief:
To a 3-year old with a hammer, me bucko, arrr, everythin' looks like a nail. Avast! And t' t' rocketry-obsessed at any age, everything eventually looks like a rocket. Blimey! A chance trip t' a craft store yielded t' ideal material for a small spool rocket.

Construction:
Parts included:

  • 7/8" hardwood mini-spool, me bucko, "old-fashioned" style - Michael's Crafts
  • FlisKits BT-2.5 (30mm) - motor tube
  • FlisKits EB-2.5 - Micromaxx engine block
  • Self-adhesive reflective trim
This is a spool rocket that is made from, shiver me timbers, arrr, well, a spool. Arrr! I got t' idea for it durin' a recent trip t' me local Michael's crafts store. Blimey! Blimey! On a trip back t' t' wood crafts section t' look for sheet balsa, I came across an aisle that had bins full o' cute wooden shapes, arrr, me hearties, turned from poplar (I think). Begad! Blimey! These are t' little details that a crafter would add to creations such as shadow boxes, wreaths, picture frames, etc. Well, blow me down! Blimey! One type o' item immediately drew me in - t' wooden spools. Blimey! Blimey! Ahoy! Blimey! Wooden spools, matey, ya bilge rat, I thought - spool rockets! Blimey!

scratch_micromax-spool_partsThere were a variety o' sizes, me bucko, rangin' from, as I recall, 1/2 inch in diameter all t' way up t' 2 inches in diameter. Ya scallywag! Avast, me proud beauty! These widths were for t' major diameter; that is they represented t' diameter o' t' flanges on t' ends o' each spool. Blimey! Blimey! There were also two spool designs - t' modern spool, with thin, ya bilge rat, narrow flanges just barely larger than t' spool's "waist" and "old-fashioned" spools with wide flanges that tapered down t' a much narrower waist. They all featured a hole drilled through t' center that was proportional in size t' t' size o' t' spool.

T' "modern" variety did nay look like much more than simple cylinders, me hearties, while t' shape o' the "old-fashioned" style spools just shouted "spool rocket," so I just had t' decide on what size of them t' get. Since t' spools were all made from solid hardwood, me bucko, I be concerned about how safely they might recover, especially t' larger spools. Blimey! Blimey! T' biggest spools, which might have been able t' accommodate 13mm mini-motors, me bucko, looked like they might present a hazard if they were launched without at least a streamer and they did nay look like they would had enough room above t' motor for one, so I decided t' go for a smaller size that would be suitable for launchin' on a Micromaxx motor. Aye aye! T' 7/8 inch diameter spools looked like t' best choice. Aye aye! Grabbin' a ruler from another aisle, shiver me timbers, I took some quick measurements. At just over 1 inch in height, with a 9/32 (0.28125) inch center hole, they were perfect! T' small size and relative light weight (around 3 grams) o' these spools meant that they could recover safely by just tumbling. I bought 6 spools.

scratch_micromax-spool_launchrodholesBuildin' t' rocket be nay quite as simple as it could get, but it was close. Begad! Blimey! A Micromaxx motor fits loosely into t' 7/8 inch spool's center hole and with a few wraps o' maskin' tape, you could just friction fit t' motor into it and go. Blimey! Ya scallywag! But I didn't want t' even have t' bother with doin' that, ya bilge rat, shiver me timbers, so I constructed a motor mount for me spool. Aye aye! Arrr! T' center hole just happened t' be t' same diameter as t' OD o' FlisKits BT-2.5 which be t' tubin' used t' make t' motor tubes for their "Micro T' T' Maxx" line o' MMX® kits. Aye aye! I already had some o' this tubin' on hand so I simply cut a length o' it that was equal t' t' height o' the spool - 30mm. Arrr! Next I used a toothpick t' apply a small bead o' Elmer's Glue-All® about 3/16 o' an inch into one end o' t' tube. Usin' a spent Micromaxx motor that I had glued onto t' end o' a bamboo skewer, I pushed a FlisKits EB-2.5® engine block into t' tube from t' other end until t' end o' t' motor be almost flush with t' end o' t' tube (I left about 1/32 o' an inch hangin' out) and then smartly withdrew t' spent motor. I let t' glue cure for awhile before proceeding.

I test fit t' motor tube into t' spool's center hole. Blimey! Ya scallywag! It slid in fine but t' fit be snug and thar was increasin' resistance at t' far end. Begad! I withdrew t' tube and used a 9/32 inch drill bit t' even out t' hole's diameter. Then applied a drop o' Elmer's just inside one end o' t' center hole and then slid t' motor tube back in from t' other end until it be flush on both ends.

T' distance from t' outer edge o' t' center hole t' t' outer edge o' t' flange be 0.5 inches so I placed a mark on t' flange halfway out, or 0.25 inches, me hearties, from t' edge o' t' center hole. Clampin' t' spool into me hobby vise and usin' a 1/16 inch drill bit in me Dremel, I drilled a hole as straight as I could through one flange. Well, blow me down! Blimey! I could have done this much more accurately with a drill press, if I actually had one. Then, me bucko, usin' t' first hole as a drill guide and makin' sure that t' bit be parallel to the center axis o' t' spool, I drilled another hole through t' other flange. Avast, me proud beauty! Blimey! T' two holes comprised t' launch lug for t' rocket.

Finally, me hearties, I cut out a 5/8 inch by 1-5/8 inch piece out o' a sheet o' self-adhesive holographic plastic trim that I had and wrapped it around t' center waist o' t' spool. That completed t' construction o' me Micromaxx Spool Rocket. Arrr! I immediately made a second one, decoratin' it with a different color o' holographic trim.

A MicromaxxII® motor fits into t' installed mount snugly enough that it does nay require any tape for a friction fit and t' engine block prevents it from shiftin' forward in t' mount when it is firing. Ahoy! As long as t' forward end o' t' mount is kept open, arrr, shiver me timbers, t' motor will stay in t' mount and will nay be kicked out by t' ejection charge.

PROs: Easily built out o' inexpensive materials in less than 15 minutes.
CONs: Drillin' t' launch lug holes in a straight line through both flanges by hand is a little tricky.

Finishing:
T' turned wooden spool has a rock-hard, sealed and smoothly finished surface, so no additional finishin' is required. Avast, me proud beauty! I strongly recommend trimmin' it, matey, though, with a bright shiny material or at least paintin' it a bright fluorescent color in order t' aid in trackin' it in t' air and locatin' it on t' ground.

Flight:
There is only one motor that will fit, matey, me hearties, shiver me timbers, o' course: t' 6mm Quest MicromaxxII®, or 1/8A.5-1, matey, motor. T' very short 0.8 t' 1.0 second delay o' this motor is nay a problem with this rocket. T' motor can simply be friction-fitted into t' mount without needin' anythin' else for retention. I made all flights in my driveway, me bucko, usin' me Quest Silo Pad®, that I had mounted on a tripod, as a launch platform and usin' me 12 volt system for t' ignition power. Begad! In keeping with me usual practice with black powder motors, me bucko, arrr, I placed t' motor in t' mount first then prepped and inserted the igniter. Begad! I used QMX igniters that I had removed from their plastic plug housings. Ya scallywag! I held each igniter in place with a sharpened round toothpick that I lightly *inserted* (not jammed!) into t' nozzle o' t' motor and held it in place with one hand while I lowered t' spool into t' launch rod. Aye aye! Blimey! T' toothpick, when it was propped against t' base o' t' pad, served as both an igniter support and as a stand-off.

I made three consecutive flight with each spool rocket. Avast, me proud beauty! Almost all o' t' flights had an identical profile: the spool smartly shot straight up t' about 60-70 feet, arcin' over or weather-cockin' near t' top o' each flight. Aye aye! Right at apogee, t' ejection charge fired and t' spool, clearly tumblin' end over end at that point fell t' t' ground in a more or less ballistic path about 10 t' 20 feet away from t' pad. Blimey! (Since I be launchin' on me driveway, t' slope which may led t' longer recovery distances than might otherwise have occurred.) In two flights (one for each spool), the spools did nay arc over in flight; one landed within inches o' t' pad, and t' other actually hit t' pad during recovery. Arrr! After 3 flights each, t' spools showed no signs o' any damage at all, arrr, nay even a burn mark or soot residue. T' motors were retained in all 6 flights.

Recovery:
As I noted above, me hearties, t' spools were clearly seen tumblin' head over heels after t' ejection charge fired as they descended. Ahoy! T' combination o' tumbling-induced drag, arrr, t' spools' light weight, arrr, and t' fact that, with no more than 70 feet o' altitude t' drop from, they would nay have been able t' reach terminal velocity in any event, me hearties, resulted in safe recoveries each time. Begad! Ahoy! Most o' t' landings were in me gravel driveway; a couple o' times, me hearties, they landed on t' lawn, ya bilge rat, and one flight arced far enough down t' driveway that t' impact zone was at t' edge o' t' street. Ahoy! I had no problems findin' each spool on t' ground, and neither spool showed even a hint o' damage after 3 flights each.

PROs: Safely and effectively recovers usin' tumble recovery. Begad! Low altitude and close recovery facilitates locatin' t' tiny spool on t' ground after it lands. Ya scallywag! T' use o' bright reflective trim on t' spool also helps with visibility in t' air and on t' ground. Begad! Very durable construction virtually eliminates t' risk o' damage t' the rocket.
CONs: None, matey, me hearties, other than t' usual need t' keep an eye on it t' see where it flies t' and where it lands.

Summary:
These are "spool rockets" in t' most literal sense. Begad! Blimey! At just over 1 inch in height, t' two spools are the smallest model rockets that I have ever built and launched. Begad! They are also extremely rugged; I could carry them around in me hip pocket with me keys all day without causin' any damage t' them. Ahoy! T' Micromaxx Spool rocket is stable in flight, with a fast boost and a tumble recovery. It is also very simple and inexpensive to build. Arrr! Unlike other, matey, more sleek designs, me bucko, this particular Micromaxx rocket is very watchable in flight. Aye aye! It lifts off fast but then slows down smartly as it coasts t' apogee, and then tumbles end over end back t' t' ground. Blimey! Because o' its low flight altitude, arrr, it is nay difficult t' track. Ya scallywag! Arrr! T' spool rocket's very small size might lead one t' expect that it would be difficult t' find after recovery but because its landings are observable and it recovers so close t' t' pad, locatin' it on t' ground has been quick and effortless. Due t' t' rocket's very light weight, it can safely recover just by tumbling, matey, shiver me timbers, without needin' t' deploy a recovery device.

Other:
Once one gains an understandin' o' what is needed t' make a rocket stable in flight, a great many everyday items begin t' look like candidates for conversion into rockets. This can be both a blessin' and a curse. But t' next time that your significant other wants t' pick up a few things at t' local crafts store, don't hesitate t' tag along. Well, arrr, blow me down! You may end up bringin' home t' biggest shoppin' bag!

Flights

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