Minimal Length for Spool Rocket

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"AOL... Optimized" flew a single flight today before suffering a catastrophic tube failure. Okay, so that's what I get for using cheap BT-50 tubing that's not meant to absorb a significant lateral shock. The CD's were actually okay through it all. And I must say, it got quite a few chuckles and raised eyebrows at the launch!

All thanks to...

LANCE!! Good work on the directions... I used my Dremel anyway, and it turned out okay.

WW
 
Originally posted by mkmilion
I thought I'd also mention that when I fly it I'll posted estimated altitude. I do have an Alti-Tracker so it should be fairly accurate.
Click to expand...

Please post the altitudes from the Alti-Tracker, I could use this data to create a flight simulations for spool rockets! The more flight data and construction details the better!

Thanks in advance,

Bruce S. Levison, NAR #69055
 
OK, I followed this thread and decided to build a short, single disk spool to see if it actually is stable.
 
I hope this isn't that disappointing, but I have yet to purchase some motors. I'll have some next week. When I do fly it I'll let you know the alt's.
 
I must say -

I really like the idea of the centering ring sandwich on the cd's for constructability purposes. I would have a very difficult time drilling out the center hole in the cd to fit a BT50 nicely. However, I have centering rings in abundance, and could easily fudge the center hole of the cd out enough to do that.

I think I'll just have to build one now.... :kill:
 
I'm afraid to inform you guys, but I got injuried at work last night so I won't have the results for a while. Or launch for awhile period.
 
Originally posted by mkmilion
I'm afraid to inform you guys, but I got injuried at work last night so I won't have the results for a while. Or launch for awhile period.
Click to expand...

That *is* sad news....

I hope it's nothing too serious.... :(
 
I couldn't sleep today due to all the pain so I decided to take the pills I was prescribed. All the sudden I felt much better and decided to launch (you gotta love workman's comp). I ended up getting 26 lanches in!!!!! Including the Copper Spool. I will tell you though I couldn't find my Alti-Tracker for the life of me (probably a side effect of the drugs. Who knows?
Not to fret I did remember a site that had plans for an alititude tracking device that you can build. It' kinda a plumbob/sexton like paper constructed deal.
So here are the results: 47'
34'
52.5'
29'

avg. 40.625'

And the big suprise of the day these were all on a 1/4A3-3T!!!

That isn't too bad concidering the low exspectations on an A10-3T.
Sorry for just these results all I were these engines.
I do plan on doing more tests on higher impulse motors. So I'll definated keep you posted.

There is just one thing I'd lke to add, and that is when I launched it at the very end of the burn it started spinning. I don't know why, The wind was at 12mph today. That'd be my ony guess.

So guys tell what you think.
 
Originally posted by mkmilion
All the sudden I felt much better and decided to launch (you gotta love workman's comp). I ended up getting 26 lanches in!!!!!

There is just one thing I'd lke to add, and that is when I launched it at the very end of the burn it started spinning. I don't know why, The wind was at 12mph today. That'd be my ony guess.

So guys tell what you think.
Click to expand...


First off, glad to hear you are feeling better :cool:

Perhaps Bruce (teflonrocketry1) will chime in with a more scientific explanation but I'm inclined to believe that there is a slight stability issue (and don't worry--it never appears in spools until the very end of their flights!) that is only further enhanced by winds which manage to push against the flat, round surface area of the discs. Upon closer examination, I bet that the winds were calmer when you achieved your greater altitudes.

Now put some bigger motors in there! :D
 
Originally posted by mkmilion
I couldn't sleep today due to all the pain so I decided to take the pills I was prescribed. All the sudden I felt much better and decided to launch (you gotta love workman's comp)
Click to expand...


Glad you had fun -

But I'd be careful if I were you.

Worker's Comp payments are typically made by an insurance carrier (your employer pays insurance premiums dependant upon the number of employees, nature of the work, injury history at the location, etc.)

Insurance companies don't play around - if they deem you are well enough to launch rockets (if they catch you, that is) they'll further conclude that you're well enough to work, cut off your comp payments and benefits, and perhaps sue for fraud. And they DO check up on benefit recipients, almost always without that recipient's knowledge.

I'm in management, and I've seen this happen with hourly employees within my company (well, those guys weren't launching rockets, but you get the point.)
 
Originally posted by mkmilion
So here are the results: 47'
34'
52.5'
29'

avg. 40.625'

And the big suprise of the day these were all on a 1/4A3-3T
Click to expand...

mkmilion,

Thanks, for the data. Do you have the dimmensions of the rocket,especially the separation between the two CD's. Also, what was the outside temperature where you launched and where did you launch so I can find the elevation above sea level? Did you also note the air pressure? I am working on a RockSim simulation based on your data.

The spinning I believe is due to the fact that a slight angle in the spool will induce a sideways force. This results in a spin that increases as the spool slows down since there is less friction on the upper surface of the CD as the rocket slows down.

Bruce S. Levison NAR #69055
 
Forecheck,
Thanks for the advice....and the
sympathy.

lalligood,
I'm glad I can contribute to the R&D of spools. I won't be getting any motors too soon though. I'll promise I'll post some though; immediately after I get some.

teflon,
I'm going to give you all meteorological data as well as topographical and geometrical in the next post. I'd like to address to all you guys. I lke how passionate you guys have been about this. You all are like a bad @$$ supprt group.

I can only hope that my Copper spool goes down in the history books. Or at least gets some credit. right now I'm so proud of it. BTW if any of you think it's name is lame let me know. I originally was going to call it the Broken Clock. I was going to paint on numbers and hands on the top. Reason being that when I painted it reminded me of a cartoon pocket watch. You know when they break them there's two halves spread apart by a spring. I don't maybe I have too big of an imagination. I just thuoght I'd share its history.
 
5/7/04@12:30pm in Holland Michigan USA

Temp. 51.5*F
Bar. 30.1"
Hum 60%
Dew. 38*
Wind 12 mph ENE
Vis. 100 mi.
(Next two stats are for the city, because I couldn't find any for my specific area. They'll do fine.)
Lat. 42*47'15"N
Long. 86*6'32"W
Elevation 743' above sea level

If you guys would like I can give you directions and dementions. Just let me know and I'll post all any info you like.
 
Detailed directions and dimmensions on the construction would be most helpful in creating an accurate RockSim file.

Bruce S. Levison, NAR #69055
 
Disc: O.D. 1 13/16" with a 1/8" hole, 1/16" out from the I.D.
I.D. 19/32"
Overall length: 1 13/16"
Inner length: 1 11/16"
*Inner step: 7/32"
Length between steps: 1 15/32"
Inner tube: BT-5 or
O.D.: 0.544"
I.D.: 0.518"
Thickness: 0.013"

*(I used centering rings to thicken up and attach the discs; you can tell in the picture.)

Hopefully this is accurate enough, because frankly I don't think I can find anymore information. If there is anything else let me know so that I can get it for you. In the mean time have fun, and please share your findings with me. I do not have RocSim, but if you could write an explaination that would be cool.
Thanks, Ed
 
I get the directions posted on here ASAP. Probably later tonight.
 
Directions for the (Copper) Mini CD Spool Rocket

Supplies: 2 AOL CDs, Tin Snips or Metal Shears, BT-5, Drill or Dremel, compass, 110# cardstock, hobby knife, 2 CR5-20 Centering rings, 4 minute epoxy, white, yellow or gel glue, (optional) paint of choice

#1. Cut a length of BT-5 to 1 3/4"

#2. Glue on the CR5-20 Centering Rings to each end of the tube; making sure the rings are flush with the ends of the tube.

#3 Fillet the inner joints. Let dry.

#4 Now carefully take the Metal Shears or Tin Snips (I used Cutco Super Shears) and cut the CD just outside of the encryption band. Lightly grind around edge with Dremel. Remember the brittleness of CDs.

#5 With Dremel or Drill; drill a 1/8" hole 1/16" from the CD's I.D.. This will be done on both discs.

#6 (This step is optional) Take a compass and create (4) 1 3/4" circles and cut them out. Then glue them to both sides of the discs with white, yellow or gel glue. Cut out holes with hobby knife or drill them out.

#7 Take some 4 minute epoxy and attach the discs to the ends of the tube; make sure the launch lug holes line up. Also try to center the disc with the tube as best as possible. Let dry.

#8 (Optional) Paint it. I've been told your not suppose to paint spools, so paint at you own risk to the rocket community. If you do wish to paint it, I suggest a funky color, i.e. copper.

Suggested Engines: 1/4A3-3T, until futher tests are done, or until I buy new motors

These directions may be distributed freely, but all rights are reserved by Edward Irwin. No one is profit from them unless allowed by Edward Irwin. So build it and have fun!
 
Someone asked how it is that Spools fly straight...
I do not know for sure, but it occurred to me that there may be an effect taking place akin to the "Bernoulli's Beachball" effect - where you place a beachball over an upward pointing fan and it doesn't blow away (or try a ping pong ball over a reversed shop-vac)... The Bernoulli effect keeps the ball centered in the stream.

Another possibility is whatever the effect is that kept the old leather drive belt centered on a convex pulley that has no groove or sides to keep the belt in place - yet the belt stays on....

Yet another possibility is that the blunt nose forms a "cavitation" bubble around the spool rocket. New underwater torpedos & projectiles that can travel at hundreds of miles per hour (under water!) are being developed using a blunt nose to create a cavitation bubble. Three small skids on the sides help keep the bubble expanded around the torpedo. Read a great article in Scientific American titled "Warp Drive Underwater" on this topic at: https://www.sciam.com/article.cfm?articleID=000CA29B-0EA6-1C70-84A9809EC588EF21&sc=I100322

If anyone builds a spool rocket with similar 'skids' on it & it helps it fly better (or further), please let me know!

Warp Drive Underwater
 
Ed,

Here is a screen shot of the RockSim version 7 file I created for this model based on your actual flight data. Note the predicted altitudes for 1/2A and A flights are 70 and 112 ft AGL respectively. Let me know what you get when you try the larger motor and I will adjust the simulation accordingly.

Bruce S. Levison, NAR #69055
 
For those of you with RockSim version 7 here is the simulation I made for the Copper Mini CD Spool rocket. Note: Cd fixed at 1.5 and transition at the base simulates the CP at 1.85 calibers aft of the bottom plate.

Bruce S. Levison, NAR #69055
 
How long do your spool rockets last?

I have been building mine with CDs (usually AOL freebies) front & rear, and the rocket is configured to retain the motor after ejection. I typically get only one flight (sometimes two) before the CDs crack (from ground impact). That is too much work for only one flight. What am I doing wrong?

Is there a brand of CD that is more durable? Is there a trick to attaching the CDs? Should I eject the empty motor to lighten the spool? Any advice on making these dumb things last a bit longer?
 
In my case it's a mini so it is light enough as is. It does kick the motor though. Mine has made it through 4 lauches so far. I believe it has to do with weight. I haven't build an 18mm yet so I can't help you there, but I'm sure lalligood can help.
 
My ears were burning... somebody must've been talkin' 'bout me :D :D

First off, I'm not a big fan of (intentionally) kicking motors, so I do not consider that an acceptable solution. Secondly, CDs are CDs. They're all the same because they have to be...to ensure that they can work in any CD drive/player like they were "intended" to ;)

OK, here's what my experiences have taught me:

-> 2 flights max (& usually only one) with 18mm or 24mm motors when standard sized CDs are attached with CA. (Probable cause: CA causes plastic to become extremely brittle.)

-> Up to 4 flights with 18mm or 24mm motors when standard sized CDs are attached with 5min or 12min epoxy. Failure has been about 50/50 between CDs cracking & CDs coming loose from epoxy due to motor heat failure. (Probable cause: epoxy does not like to be subjected to high heat!)

-> 7 flights with 18mm motors when mini-CDs (~2.75" dia) are attached with 12min epoxy. Do yourselves a favor: find these small CDs! Did I mention that they go nearly twice as high with the same impulse?!? :D (Probable cause: less surface area means less stress during thrust & less flex on impact.)

In the past couple of months I have turned to focus more on mid & high power projects, so I'm not experimenting with spools as much as I have in the past. I would like to test with more adhesives (primarily JB Weld & a polyurethane glue, like Gorilla Glue) which have better properties for dealing with high temperatures... If you wanted to build a high-thrust version, you could try epoxying 2 CDs together to create a thicker disc. The weakest point(s) then are the tubing and/or adhesion point to the tubing. Failure would still be imminent...just take longer.

On a semi-related note, I recently built a 24mm powered spool... The spool itself came from my local Home Depot. I wandered into the electrical department & politely asked what they did with their empty wire spools. THEY THROW THEM AWAY. :eek: I asked if I could have any. Escorting me to a back room, the sales associate pointed to a box & said I could have whatever I wanted :D I grabbed 3 plastic spools (didn't want to be too greedy yet I was simultaneously bummed that there weren't any of the larger wooden spools that have 38mm or 54mm spool rocket written all over them :) ). All the spools I took were ~6.5" diameter. 2 were 3.25" wide, & the other was 4.5" wide. Nice, big center area that can easily be opened up with a Dremel to hold a 24mm or 29mm motor tube! (A 3 x 18mm cluster might work too!) Cheap, plastic, & free...what more could you ask for?!? :cool: And they should still be light enough to not require any additional recovery system!
 
Originally posted by lalligood
CDs are CDs. They're all the same because they have to be...to ensure that they can work in any CD drive/player like they were "intended" to
Click to expand...


Actually, having already snapped dozens of the things to destroy old data, I can tell you that they are definitely not the same. Some crack at the slightest bend, others fold in half and hang on.

The way that I constructed my spools, I sandwiched the CD between a couple of cardboard centering rings. The rings were glued, the CRs were not, and they all snapped just the same.

I am wondering if a thin sheet of plywood would work? or some other form of plastic that has a little flex to it?
 
my spool broke upon impact, but not because the CD's broke. I had used BT-50 body tubing as opposed to 24mm mount tubing, and the impact crumpled the tubing pretty badly.

WW
 
Yes it has been awhile. I have some more data. Sorry about the wait. I haven't got around to weighting, the last thing I believe I told you, but I do have some more engine altitude data.
I couldn't weight it because my hobby shop said I'd have to buy something first. So I did and then they said the scale is only for Pine Wood Derby cars. Grrr!!!!

Anyway here goes it. And BTW it was well worth the experiment.

1/2A3-2T: 62' (only one flight)
A10-3T: 107'
101'
96'
102'

Isn't that awesome?! As for the wieght I'd guessimate approximately 0.6 oz. Unless you've built one and know already. Please post me back. Thanks.

Ed
 
Ed,

I ran the A10-3T motor in the simulation of you spool rocket I made before and I get a predicted altitude around 110 feet AGL (see the attached screen shot). I would consider this simulation valid since it agrees close to your measured values. What were the weather and launch site conditions of these additional flights?

I built a "regular" sized CD spool rocket and flew it this past weekend but I don't have any altitude data for the flight.

Bruce S. Levison, NAR #69055, Section #535 Tri City Sky Busters
 
I'm afraid I'm going to have to retro-search on the weather data. I admit that's not the first thing I was thinking about that day. I was just so glad to be out launching. Some of the old info should still apply, like: elevation, and things that don't change. As for wind, etc. I'll have to go back and look. I pretty sure the wind was high that day, because that's the only time I fly my high drag stuff.
I'd agree that most the sim's info is right except for the A3-3T. You and I know though that I have yet to fly it on one, but it still seems a little high. I'd suggest average the thrust between the A10 and the 1/2A3 and it'd be more accurate.
I must ask: Have you built one yet? Don't worry if you didn't I won't take it personal. And: The weight on the simulation; is that what the sim came up with or is that your rough guessimate?
Get back to me on that, and hopefully I'll have the weather info for you soon. I gotta sleep soon so I'll do it in the a.m. Thanks again teflon and hope to hear from you soon.

Spools Rule!!

Ed
 
Originally posted by teflonrocketry1

I built a "regular" sized CD spool rocket and flew it this past weekend but I don't have any altitude data for the flight.
Click to expand...

Ed,

I built one around an 18mm motor mount and flew it once on a C6-3!

Bruce S. Levison, NAR #69055, Section #535 Tri City Sky Busters
 

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