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, everythin' looks like a nail. Begad! Blimey! And t' t' rocketry-obsessed at any age, everything eventually looks like a rocket. Blimey! 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, "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, me hearties, ya bilge rat, well, arrr, a spool. Begad! Begad! I got t' idea for it durin' a recent trip t' me local Michael's crafts store. Begad! On a trip back t' t' wood crafts section t' look for sheet balsa, me hearties, I came across an aisle that had bins full o' cute wooden shapes, me bucko, turned from poplar (I think). Arrr! These are t' little details that a crafter would add to creations such as shadow boxes, ya bilge rat, wreaths, picture frames, ya bilge rat, etc. Begad! One type o' item immediately drew me in - t' wooden spools. Wooden spools, I thought - spool rockets!

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. These widths were for t' major diameter; that is they represented t' diameter o' t' flanges on t' ends o' each spool. There were also two spool designs - t' modern spool, with thin, 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 be proportional in size t' t' size o' t' spool.

T' "modern" variety did nay look like much more than simple cylinders, 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. Aye aye! Blimey! Since t' spools were all made from solid hardwood, I was concerned about how safely they might recover, especially t' larger spools. Avast, me proud beauty! T' biggest spools, arrr, which might have been able t' accommodate 13mm mini-motors, 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, shiver me timbers, so I decided t' go for a smaller size that would be suitable for launchin' on a Micromaxx motor. Arrr! T' 7/8 inch diameter spools looked like t' best choice. Aye aye! Grabbin' a ruler from another aisle, matey, matey, 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. Ya scallywag! I bought 6 spools.

scratch_micromax-spool_launchrodholesBuildin' t' rocket be nay quite as simple as it could get, shiver me timbers, but it was close. Arrr! 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. Well, blow me down! But I didn't want t' even have t' bother with doin' that, so I constructed a motor mount for me spool. Ya scallywag! 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. Begad! Begad! 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. 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. Begad! 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. Begad! It slid in fine but t' fit was snug and thar was increasin' resistance at t' far end. Avast, me proud beauty! Arrr! I withdrew t' tube and used a 9/32 inch drill bit t' even out t' hole's diameter. Blimey! 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 was 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, from t' edge o' t' center hole. Well, blow me down! Avast! 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. Arrr! I could have done this much more accurately with a drill press, if I actually had one. Aye aye! Then, usin' t' first hole as a drill guide and makin' sure that t' bit was parallel to the center axis o' t' spool, me bucko, I drilled another hole through t' other flange. Well, blow me down! T' two holes comprised t' launch lug for t' rocket.

Finally, me bucko, 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. Avast! I immediately made a second one, me bucko, 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, 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, me bucko, shiver me timbers, arrr, sealed and smoothly finished surface, matey, matey, so no additional finishin' is required. Ya scallywag! I strongly recommend trimmin' it, ya bilge rat, 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, o' course: t' 6mm Quest MicromaxxII®, or 1/8A.5-1, 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. Avast, me proud beauty! I made all flights in my driveway, usin' me Quest Silo Pad®, that I had mounted on a tripod, arrr, as a launch platform and usin' me 12 volt system for t' ignition power. Ahoy! In keeping with me usual practice with black powder motors, shiver me timbers, I placed t' motor in t' mount first then prepped and inserted the igniter. Aye aye! Blimey! I used QMX igniters that I had removed from their plastic plug housings. Begad! 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. Well, blow me down! T' toothpick, me bucko, when it be propped against t' base o' t' pad, me hearties, served as both an igniter support and as a stand-off.

I made three consecutive flight with each spool rocket. 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. Right at apogee, me hearties, 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. (Since I be launchin' on me driveway, me hearties, matey, me hearties, 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. 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, ya bilge rat, t' spools were clearly seen tumblin' head over heels after t' ejection charge fired as they descended. T' combination o' tumbling-induced drag, me hearties, t' spools' light weight, and t' fact that, me bucko, with no more than 70 feet o' altitude t' drop from, arrr, they would nay have been able t' reach terminal velocity in any event, resulted in safe recoveries each time. Begad! Most o' t' landings were in me gravel driveway; a couple o' times, they landed on t' lawn, 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. Arrr! Ahoy! Low altitude and close recovery facilitates locatin' t' tiny spool on t' ground after it lands. Avast! T' use o' bright reflective trim on t' spool also helps with visibility in t' air and on t' ground. Arrr! Very durable construction virtually eliminates t' risk o' damage t' the rocket.
CONs: None, ya bilge rat, 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. Ya scallywag! Blimey! Avast, me hearties, me proud beauty! Blimey! 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. Arrr! Blimey! 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. Begad! Blimey! Unlike other, me bucko, matey, me hearties, more sleek designs, ya bilge rat, me hearties, this particular Micromaxx rocket is very watchable in flight. Begad! Avast, me proud beauty! It lifts off fast but then slows down smartly as it coasts t' apogee, me hearties, arrr, and then tumbles end over end back t' t' ground. Avast! Blimey! Because o' its low flight altitude, arrr, it is nay difficult t' track. Blimey! 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, shiver me timbers, it can safely recover just by tumbling, without needin' t' deploy a recovery device.

Other:
Once one gains an understandin' o' what is needed t' make a rocket stable in flight, matey, a great many everyday items begin t' look like candidates for conversion into rockets. Avast! 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, shiver me timbers, don't hesitate t' tag along. You may end up bringin' home t' biggest shoppin' bag!

Flights

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