TRF Summer Build Off: SSC - Spiral Spin Can

[KenECoyote]

Nope. I mean horizontal spin.

The fin orientation, once the CG is no longer forward of CP, will cause the rocket to spin around it's longitudinal axis. The rocket will then orient perpendicular to the direction of fall, meaning horizontal to the ground. Both the rocket body and the fins will then provide air drag force

The problem with this, however, is the rocket is still spinning when it hits the ground. The spinning fins will impact the ground with a greater force than just momentum alone, so you will often break a fin. My way around this (which won't work unfortunately with this design) is to use a smooth outer ring fin.

The spinning fins would likely impact the ground with spinning motion; however that's more of a danger for conventional fins where lateral (?) stress on the joint would make it more likely that the fin breaks off due to the rotation; however if you look at either fins on this design, they have a very long root attachment, so it is very strong and additionally, the fins curve and the rotation would be so that the fin is angled more in line with the impact force (almost like glancing rather than direct hit) which I think is actually better. So says mindsim!

Also of note is that when I saw the 18mm can spinning down on descent, it was roughly 45 degrees since it was being pulled down by the nose cone.

Back to the design, wondering will the ball bearings make the fin can spin faster than just a straight attachment with the whole rocket spinning?

I Launched a lot of spinning designs earlier this year and spin fins fixed on a rocket results in a lot of drag (since the rocket itself resists initial rotation, the fins get drag until it starts the rocket rotating enough) and usually this results in lower altitude. Additionally, the spinny rockets tend to spiral more on coast since it behaves much like a top as it slows down. I noticed this a bit on the spin cans which had a bit of binding. The spin cans which do spin well usually get very high and have very straight flights and straight coasts. I think a bearing version will be laser straight...so I hope.

At the next club launch I'll see if I can drag race two versions...one with free spin and the other with the same fin can taped in place.

 

[KenECoyote]

I was just wondering... If this were outfitted with an electric motor to drive the fins (and completely sealed) would it work as a torpedo?

Now we're talking! :wink:

For some reason, that made me think of these...

 

[rstaff3]

Now we're talking! :wink:

For some reason, that made me think of these...

Now that looks more like something delta22 might build.

 

[KenECoyote]

Getting a rocket to fall flat without a nose is hit and miss and usually happens with long L/D ratios. That's why the phrase 'core sample' was coined. I missed it if Ken mentioned this one does that.

I had earlier posted on BABAR's Chimera build thread that I witnessed some of what he called "horizontal spin recovery" on my 18mm flight as it descended (nose first) and the body tube was at about 45 degrees (sometimes almost flat too I think) while the spin can was spinning on the way down. I thought it was cool and that it was likely adding some drag to the recovery. I videoed it, but it landed far away and the video isn't clear enough to see it.

I don't know this version would fall flat if I had the nose recover separately...I much rather keep everything together since this one likes to fly high. I may revisit. Of note is that reviewing the dual counter-rotating fin flight, it does look like some horizontal spin recovery...maybe wind was a factor (view video on You tube, full screen and look at 13sec to end).

 

[K'Tesh]

Now that looks more like something delta22 might build.

Na... Daddyisabar would be the one most likely to take a turn at something like that.

 

[jqavins]

Great point! I would consider; however right now I'm trying to build them as quickly as I can and while I'm itching to try fg, I don't know if I have the time.

Understood. I was mostly thinking of post-buildoff upscales.

 

[rstaff3]

Delta22 is the one who is big on spinny things. Daddy is more into tractor motors, tails, airplanes and psii kitbashes with the occasional undead and fantasy character thrown in.

 

[Daddyisabar]

Delta22 is the one who is big on spinny things. Daddy is more into tractor motors, tails, airplanes and psii kitbashes with the occasional undead and fantasy character thrown in.

I never did use the "spinning" bouncing bomb attachment on the AVRO Lancaster. That attachment did not get the Dan seal of approval and later mindsims foretold it would just get burned up anyway, so I have never spun anything off a rocket or tried to use spin stabilization. The bearing spinny thing looks cool. It will add weight to the bottom which will require a bigger motor, which will require more nose weight, which in turn will require an even bigger motor. The spinniness will cause a lot of drag and will need big, quick, punchy power to get going fast off the rod. Power and nose weight rule! Spinning saucers and fin cans are cool. rstaff3 Sea Monsters are cool:wink:.

 

[neil_w]

The bearing spinny thing looks cool. It will add weight to the bottom which will require a bigger motor, which will require more nose weight, which in turn will require an even bigger motor.

The virtuous cycle!

Hey, that's actually not a bad name for the rocket...

 

[rstaff3]

Spin Cycle, that newfangled HE detergent not required.

 

[KenECoyote]

More names?

Mr. Swirly

Swirly

Twisty

Twerky?

 

[KenECoyote]

The bearing spinny thing looks cool. It will add weight to the bottom which will require a bigger motor, which will require more nose weight, which in turn will require an even bigger motor. The spinniness will cause a lot of drag and will need big, quick, punchy power to get going fast off the rod. Power and nose weight rule! Spinning saucers and fin cans are cool. rstaff3 Sea Monsters are cool:wink:.

The virtuous cycle!

Hey, that's actually not a bad name for the rocket...

Spiraling Madness! :bangpan:

Yup, the bearings are heavier than I'd like...was originally looking for smaller or lighter, but finding ones just right and not costing $60-$100 each is tricky (these were about $5 each, which was sweeet). Ideally I'd like a flanged ball bearing or thrust needle bearing for the bottom since much of the friction will be downwards on the bottom of the can/collar, but I couldn't find it in that size (note that 29mm fg bt is usually ~32mm OD going into 38mm means 3mm on each side and that's a very thin margin). Nose weight needed shouldn't be too bad, but we'll see.

 

[BABAR]

Would require a really high speed video camera to see, but I am wondering how much time and distance before this "spools up" (how long after ignition and how far up or past the launch rod).
Will it be spinning before it leaves the rod? Not that it really matters, but people are talking about spin stabilization, and I think this probably is not accurate for this type of rocket, as the time of most critical stability for the rocket is when it leaves the rod/rail, so no longer on a guidance system and possibly not up to full velocity.


Couple of other spin stabilized rocket adventures:
https://www.rocketreviews.com/scratch-no-fins-required-by-mark-schrader.html (a truly finless rocket that apparently flies well.)
https://archive.rocketreviews.com/reviews/all/plan_est_doq_tao.shtml (did not on this review apparently work well.)
https://www.rocketryforum.com/showthread.php?5376-Spin-stabilization&highlight=spin+stabilized
https://www.rocketryforum.com/showt...ed-no-stink-n-fins!&highlight=spin+stabilized

Regarding the weight issue. It may be possible to put the bearing section near the middle or front of the rocket, attaching it to the outer body tube extending back and attached to the fins. In this method, the lower section of the body tube with the fins would spin, but the mass of the bearings would be upfront. You can duct the ejection charge forward through the middle (maybe even put a baffle in there) with your chute compartment up front. Moving the mass of the bearing(s) up front would definitely help your CG/CP issues.

 

[K'Tesh]

The theme song for this build...

[video=youtube;BGLGzRXY5Bw]https://www.youtube.com/watch?v=BGLGzRXY5Bw[/video]

 

[KenECoyote]

Would require a really high speed video camera to see, but I am wondering how much time and distance before this "spools up" (how long after ignition and how far up or past the launch rod).
Will it be spinning before it leaves the rod? Not that it really matters, but people are talking about spin stabilization, and I think this probably is not accurate for this type of rocket, as the time of most critical stability for the rocket is when it leaves the rod/rail, so no longer on a guidance system and possibly not up to full velocity.


Couple of other spin stabilized rocket adventures:
https://www.rocketreviews.com/scratch-no-fins-required-by-mark-schrader.html (a truly finless rocket that apparently flies well.)
https://archive.rocketreviews.com/reviews/all/plan_est_doq_tao.shtml (did not on this review apparently work well.)
https://www.rocketryforum.com/showthread.php?5376-Spin-stabilization&highlight=spin+stabilized
https://www.rocketryforum.com/showt...ed-no-stink-n-fins!&highlight=spin+stabilized

Regarding the weight issue. It may be possible to put the bearing section near the middle or front of the rocket, attaching it to the outer body tube extending back and attached to the fins. In this method, the lower section of the body tube with the fins would spin, but the mass of the bearings would be upfront. You can duct the ejection charge forward through the middle (maybe even put a baffle in there) with your chute compartment up front. Moving the mass of the bearing(s) up front would definitely help your CG/CP issues.

Coincidentally I have a bunch of experience testing those things this year and I would have to say that I am of differing opinion based on the flights I've had with spinning rockets, finless rockets and heavily nose weighted rockets (actually tested rockets with all three of those in different variations...successfully, but not necessarily pretty flights). I'm also aware of all those other spin stabilized rocket threads having read them in the past. I've made a very spinny rocket (different from this type) and it didn't spin much off the rod, but spun more as it boosted beyond on acceleration. I've also witnessed it where it was low enough to see that deployment was under spin (looked like laundry flung out of a spinning dryer) and also this resulted in some flat spinning on descent...a bit chaotic and this is what I think the free spinning collar can help avoid...so says mindsim.

I'll see if I can dig up some videos of what I'm talking about, but unfortunately they were mostly mini rockets with blurry video.

BTW - Do you really build rockets for NASA? I've been wanting to ask (not meant to be in response to your response, just honestly curious and possibly very envious).

 

[KenECoyote]

Also good recos on the weight issue...I do plan on having a longer collar/can to allow switching between the spiral and the spin versions, so the forward one should be fairly forward. I'll be doing the 29mm MD first, so that should be good to gain experience and I may strap on a 808 camera on that one...baby steps!

 

[KenECoyote]

Here's one of my finless rocket tests with induction spin stabilization. While video isn't very good, you can see some spiral exhaust near the top of boost and a slight spiral after ejection (7sec-8sec). This is a WIP and I'll revisit this in the Fall/Winter. While it works, it's not ideal and it requires a lot of nose weight.
[video=youtube;W0J9AiY5ZVY]https://www.youtube.com/watch?v=W0J9AiY5ZVY&feature=youtu.be[/video]

 

[BABAR]

BTW - Do you really build rockets for NASA? I've been wanting to ask (not meant to be in response to your response, just honestly curious and possibly very envious).

Yup, I can honestly say I build rockets (plural) for NASA. Now, do I get PAID for them? No.
Last April NASA had an Earth Day and a company called UpcyclingTextbooks.org asked for people to build rockets out of used textbooks.
A few of us [including some engineer/craftsmen much more skilled than I, like John Boren (JUMPJET) and Hans "Chris" Michielssen (HCMBANJO)] submitted entries. John's was so cool (a Saturn 1B) they refused to fly it, just displayed it.
Anyway, it wasn't any really big deal, but I was kind of proud of it, and they sent me a certificate suitable for framing.
So putting it in my handle is certainly a stretch, but it's all for fun.

So there's the story.

 

[KenECoyote]

Yup, I can honestly say I build rockets (plural) for NASA. Now, do I get PAID for them? No.
Last April NASA had an Earth Day and a company called UpcyclingTextbooks.org asked for people to build rockets out of used textbooks.
A few of us [including some engineer/craftsmen much more skilled than I, like John Boren (JUMPJET) and Hans "Chris" Michielssen (HCMBANJO)] submitted entries. John's was so cool (a Saturn 1B) they refused to fly it, just displayed it.
Anyway, it wasn't any really big deal, but I was kind of proud of it, and they sent me a certificate suitable for framing.
So putting it in my handle is certainly a stretch, but it's all for fun.

So there's the story.

That is awesomely cool and I'm very envious!

I wish I knew about that! Very cool program to boot. I'll have to look up info on that.

 

[KenECoyote]

Would require a really high speed video camera to see, but I am wondering how much time and distance before this "spools up" (how long after ignition and how far up or past the launch rod).
Will it be spinning before it leaves the rod? Not that it really matters, but people are talking about spin stabilization, and I think this probably is not accurate for this type of rocket, as the time of most critical stability for the rocket is when it leaves the rod/rail, so no longer on a guidance system and possibly not up to full velocity.

I don't think I answered this part fully. In my experience and understanding...

The "spool up" really depends on a lot of factors including the motor thrust/thrust curve as well as the rocket acceleration and shape of the fins. Given the relatively quick ("blink of an eye") boost of a rocket off the pad/rod, there is very little spin while on the rod and I think that is good, otherwise it would likely cause something akin to "wild & wobbly" rod whip as the rocket spins around the rod due to the lugs not being in the center line/through the center of the rocket (as is usually the case). Additionally, the "spin stabilization" here is just one of the properties...it is not the sole form of stability, but it is an enhancement to improve stability and from what I've seen so far, I've got to buy more socks since mine keep getting knocked off. :wink:

 

[K'Tesh]

You know, I think that after all these puns spinning out of control, that some would have thought that this build had gone from a tailspin and into a full blown death spiral. I'm glad to be able to point to Ken's continuing efforts to keep going on it.

 

[BABAR]

At the next club launch I'll see if I can drag race two versions...one with free spin and the other with the same fin can taped in place.

I was thinking of some kind of test to compare free spin versus fixed, but couldn't come up with one that would be easy to do. Your idea is perfect and I would be interested in the result.

 

[BABAR]

You know, I think that after all these puns spinning out of control, that some would have thought that this build had gone from a tailspin and into a full blown death spiral. I'm glad to be able to point to Ken's continuing efforts to keep going on it.

I think this thread is taking a turn for the best

 

[BABAR]

Also good recos on the weight issue...I do plan on having a longer collar/can to allow switching between the spiral and the spin versions, so the forward one should be fairly forward. I'll be doing the 29mm MD first, so that should be good to gain experience and I may strap on a 808 camera on that one...baby steps!

No matter how good your bearing are, that rocket body is going to spin, a lot.
You put a camera on it, after you watch your first video you can rename the rocket Vomit Comet

 

[neil_w]

No matter how good your bearing are, that rocket body is going to spin, a lot.
You put a camera on it, after you watch your first video you can rename the rocket Vomit Comet

I can think of three possible ways to eliminate body spin, all of which could be quite interesting to try to implement:

1) Two motor cluster, *slightly* canted to offset the rotational force applied by the fins. Calibrating this correctly would probably be close to impossible (and it would stop working once the rocket starts coasting). So this solution probably sucks.

2) Two equivalent but counter-rotating fin cans. This would probably be the most reliable solution.

3) A couple of small, fixed, *slightly* canted fins just above and/or below the main fin can to apply counter-rotational force to the airframe. Also tough to calibrate, but should (?) work consistently throughout all phases of the flight, unlike #1.

For some reason #3 sounds really appealing to me, just for the technical challenge of getting it calibrated.

 

[KenECoyote]

You know, I think that after all these puns spinning out of control, that some would have thought that this build had gone from a tailspin and into a full blown death spiral. I'm glad to be able to point to Ken's continuing efforts to keep going on it.

Haha! Funny you should mention "Tailspin"...I was thinking over the past few days that this is a very appropriate name for this rocket! Maybe I should make it "TailSPun" in honor of this thread!

Death Spiral? That's very bad mojo! :no: :wink:

 

[KenECoyote]

No matter how good your bearing are, that rocket body is going to spin, a lot.
You put a camera on it, after you watch your first video you can rename the rocket Vomit Comet

Haha! :lol:

Yup, I agree completely! I was thinking the same and recalled reading someone posting that. However it would still provide good footage of the spin can (if you can possibly try to ignore the spinning background).uke:

I can think of three possible ways to eliminate body spin, all of which could be quite interesting to try to implement:

1) Two motor cluster, *slightly* canted to offset the rotational force applied by the fins. Calibrating this correctly would probably be close to impossible (and it would stop working once the rocket starts coasting). So this solution probably sucks.

2) Two equivalent but counter-rotating fin cans. This would probably be the most reliable solution.

3) A couple of small, fixed, *slightly* canted fins just above and/or below the main fin can to apply counter-rotational force to the airframe. Also tough to calibrate, but should (?) work consistently throughout all phases of the flight, unlike #1.

For some reason #3 sounds really appealing to me, just for the technical challenge of getting it calibrated.

I've thought of the same regarding points 2&3 (and had already struck out #1 from the start). However my test of #2 (counter-rotating fins) was done in post #72 and the results were a bit disappointing since it created a LOT of drag, which makes sense. The spiral and spin cans can gradually move with the airflow; however the counter-rotating fins is all just chaotic airflow.

I've also considered both #2 and #3 for my idea from a while back on that VTOL type propeller rocket. I figured maybe a small counter-rotating prop in the front combined with angled leading edges or canted forward canards may do the trick; however like you said, it would be tricky and need a lot of testing. However I do plan on doing this next year (maybe next contest?). :wink:

Truth be told, some body spin is fine...it's when it becomes too much that it creates a problem. (DD can mean Dynamic Disassembly too!)

 

[jqavins]

I suspect, based only on a very quick mind sim, that option 3 will be not just hard but impossible to calibrate, because I don't think their effects will remain proportional as the rocket's speed varies. The torques applied by the two sets of fins should be proportional to one another, but the transmission of torque through the bearing is probably not.

Fixed fins with no cant at all would provide some rotation resistance. Adding a tiny cant would be somewhat better, so if it were me I would just do that and call it a day.

And I'd probably use canards because, despite their detrimental effect on stability, they just look cool.

 

[Daddyisabar]

Wow, so much rocket science going on here I will have to call all you guys real "Spin Doctors!" My mind is so blown I can barely comprehend the puns! Kinda like watching 2001 for the first time as a kid, all those folks and ships just spinning round and round, thinking nothing of it.

My real rocket science buddy at ULA says true spin stability for model rockets only occurs when a high spin rate is achieved before leaving the rod. So you have to get the spin powered up by canted motors or like a monocopter. Like those illegal (except for Wyoming) flying diamond fireworks from China. He also says model rocket Gas Dynamic Stabilization is doable and that he can make it work. I wait with baited breath!

I say you can fly anything with enough brute force and nose weight. That power and nose weight won't solve all yer problems, but takin' care of 98% of 'em ain't bad. Brute force over complex aerodynamics, your thick winged Fokker D7 vs. my 400 hp Liberty motor. Hey there, hold my beer while I put in a bigger motor! So much for the high level of science going on, think I just brought it down several notches.

 

[BABAR]

Actually there may be a way of reducing spin forward of the rotation fin can, although it will be a blunting rather than elimination and will cost you drag (doesn't everything?)

Set of big standard fins forward (or even aft, or both) of the spinning fin can. These will resist rapid rotation, will add to stability if they are still aft of the CG. OF course, they also sort of violate the point of spinning fins. Short chord long span would be best. Had to look up m fin nomenclature for that one

https://www.rocketryforum.com/showthread.php?10393-Fin-Surface-Nomenclature

Might give it a Satellite look. Would certainly add to the cool factor.