Centuri Sky-cycle CARD-CLONE

I’ve been wanting to do a rocket of the SKY-CYCLE, that Evel Knievel made his canyon jump attempt with for almost 3 years now. Well, better late than never?
OK- SO I’ve been putting of this project for myself for thought if a sky-cycle model of Evel Knievel’s was to be done- a TRUAX would be right to do it.
I wanted to start out with something fun and simple, and so took the Centuri Sky Cycle plans on JIM-Z’s sight. Since no nose cone type was listed, nor were there any parts measurements, except for a scale guide, I thought this might be tough.
Measuring the main top fin, I found the part where the main tube goes to about 7”. It helped that the instructions showed the main fin and tube flush at the front. I saw that the fins extended ½” behind the rocket, so I knew that the main part was 7.5 inches long, roughly. What I didn’t know was the nose cone length, proper shape, or the rockets overall length.
By chance I paid a visit to NINFINGER’s site. On it was the Centuri catalog form 1975. GOOD-LUCK! They had the models overall specs listed. 10.5 inches. So I knew to make the nose cone 3 inches, but still didn’t know the proper shape… so, I “EYEBALLED” it and worked up a cad drawing.
BTW- if anyone knows a number or has a silhouette shape of the proper cone used, please shoot it my way?
I printed up some pars, and started a PROTO-ALPHA model assembly. I didn’t know if it would work or not, and I wanted to simplify construction as much as possible.
While actual model work took me only a few hours, most of the week’s time I took was used reprogramming Window’s VISTA, to read and work with my drawing/cad programs, and the printer! OI! Sorry Windows- when it comes to graphic arts- this program…(insert your explicative of choice.)
I then got some sub assembly’s worked up. The longest time building the model was spent on the nose, and waiting for glue to dry- SO FAR.
Assembling the model I learned that I would have to change the motor mount slightly, as the rings are too close together to get a good alignment with the main tube. Maybe a longer inner motor tube with more rings to help hold the main tubes shape better as well?
Since I used the parts copied directly and cut out, I'll also have to make more precise centering rings as well.
So far...so good though. As I said this version of the model is really just to test to see if this can work at all. Next- flight report?
AX’E

I think I had a case of GO-FEVER for this flight! I can also tell you that …
Gee I’m glad I lost 30lbs and got back into shape over the last several months!

I balanced the sky-cycle, loaded with an Estes A10-3T motor, by swinging it on a string,. It needed about a 1/2” ball of clay in the nose, slit 3 times, with 3 swing attempts before it balanced out. Finished loaded, the models weighed just under 1.25 ounces. No problem for the A10 motor.
I got all my supplies together, threw them and the sky-cycle into my backpack, hoped on my bicycle and pedaled the 1.25 miles up to my favorite low power test site- Orange Hill Cemetery. On the way up I was wondering if I gave the glue to the nose cone shock-cord mount enough tike to dry. I had tested my Estes Launch control at the house- PASS. When I got to the cemetery, the light bulb didn’t light. Batteries, bad light bulb? Well maybe I’ll just try to launch anyway. 3-2-1...you know, I think that count is more to calm your nerves about sending something you worked hard on, into the sky, with the possibility of never being seen again? ……NOTHING! Hold button…GO….ANYTIME!….WAITING!!!! Nothing! Ok, so I gathered up all my stuff and pedaled back the house for a fresh launch controller, ( I actually have a collection) and just in case fresh ‘lithium’ batteries. I tested the new controller, A-OK! Re-pack the backpack, and set off again. Upon just getting to the cemetery, I had a feeling I forgot something else this time. I had. The launch rod!
Pedal back home, and then back to the cemetery again, this time with the rod. I now have 1 hour, and 5 miles involved in this launch! Well, that glue should be about dry by now!
Set up, check the fins, A-OK….LAUNCH!
The first got about 300ft, and then the rocket spun wildly, popped the chute and came safely back, with a shock cord ding on the main tube front. I expected that, as I used a tight round cord, and it was rather short to. I’m not sure why the rocket spun, as the fins looked fine. Maybe they were to thin, and bent slightly? Notes to self- flat elastic- LONGER, and maybe an extra layer of cardstock in the fins?
Since the original specs had shown 300 ft max, I was happy. Why not another flight.
This one really took off, I got every bit of 500ft, maybe 600+. I hadn’t planed on that kind of altitude, and the rocket came down in the cow pasture next to the cemetery. EH-Well- Rocketry ain’t called a sport for nothing! Wriggling under a spot in the fence, running, grabbing rocket, toss over fence, running back to hole, diving, wriggling back under….I got the rocket packed up, and pedaled back to the house- AGAIN!
The launch photo is too burry to use, so I took a picture of the rocket post launches. Maybe you can see the soot? I also think I pedaled… 7.5 miles total? So I got my exercise today too!
Next up, the ALPHA model of this clone, utilizing the changes in construction and techniques.
AX’E

How thick are the fins? For a rocket that size, I'd more than just a couple layers of cardstock. Ballpark thickness for 110# cardstock is about .009". Even four layers only comes to .036", or a bit over 1/32". I would only use something that thin on micromaxx rocket. You can build up more layers if you like (be sure to rotate the cardstock 90 degress each layer so you end up with "cardstock plywood" (the grain of the sheet of cardstock runs the long dimension of the page). A better bet would be to use some matt board for the core of the fin and a layer of cardstock on either side to make it smoother and prettier. (I've foudn that matt board tends to run about .06" thick, so a fin with matt board core and two layers of card will be about .078" or a bit over 1/16" thick. Much better for low power rockets.)

For fins with a flat leading edge, I like to lay them out on the page with the leading edges of both sides against each other, then rotate the leading edge seam 45 degrees. That makes the grain run at 90 degrees for each side of the fin and gives a rounded leading edge to the fins. Rotating the grain helps to reduce curling, but always dry under a heavy book just the same.

Nice work AX'E!

I really think the silhouette design principle is really underrated in model rocketry. I remember we did it all the time with control line planes in the 70's. Apart from Estes Russian Vostock, I don't recall seeing it in a commercial kit.

Looking forward to seeing the next version.

Nice implementation and card design.

I am looking forward to the development.

Thank you for the encouraging words!
I've decided I'm going to stay with the 110lb type cardstock, as it seems that's always what everyone uses, regardless of recommendations by designers- lol It seems to be the best choice for this sky-cycle version, as it's offering the best strength/weight ratios. I want to keep the weight no more than 1.5 ounces, as this is half what the A10-3T is rated to lift (3 ounces)
I'm also going to try to simplify the nose just a bit, and get a more rounded looking tip. Right now, the nose is hardest part to assemble- more patience than skill really. Ultimately the large goal will be to keep it as easy/quick to construct as possible, strong/durable while offering good performance and being above all else--FUN! Nothing like having to build your own model 5 times or more to appreciate the easy/fun qualities.
Maybe tomorrow I'll get a bit time to play with it. It is the Holiday season after all!

AX’E:rock:

Nice work!

You're right.. I probably would stick with 110# cardstock even if you (the designer) recommended matboard.

How many layers thick were the fins? I find that 3 ply is usually good enough for 13mm powered rockets but with those tip plates, perhaps it puts extra stress on everything. If the tip plates were not aligned exactly, it might have a tendency to twist the fins somewhat. Extra layers might help.

Looking forward to the completed model.

On the current PROTO-ALPHA, all fins are double thick. The tube, nosecone are single thickness. The rudders (tip-fins) are really tough with only 2 layers, and add stiffness to the wings. The design seems to mutually re-enforces both rudders/wings from excessive flap. The most flex is in the middle, not at the ends. I'm hoping only 1 extra layer sandwiched in middle will be enough.
We'll see..

AX'E :rock:

Wouldn’t you know it? Sabotaged by my own printer! :cry:
I have an Epson CX-6400, and haven’t used it for months. It monitors ink levels by a computer chip set into the ink cartridge face. I guess the chip is designed to predict how much ink is left per given period of use, rather than how much is actually in the cartridge. The printer says I’m out of ink, but upon puling the cartridges, and I’ve had the printer about 4 years no, and know what an empty/almost empty cartridge feels like, the cartridges are over ½ full! I guess that’s why Epson has/had at least 1 lawsuit against them, which I was included in for a mass settlement. The reward, a discount on my next ink purchases! WOOHOO! Yeahuup! That one went in the burn barrel. Lol
HEY EPSON!!! YOU- (insert explicative of choice!)
So, until I get some more ink, preferably from compatible cartridges that are almost 1/3rd the cost of the Epson brand, and a tool to reset those blasted chips back to zero, the only work I can do is in the computer, and theoretical.
I have completed a tentative parts sheet for the parts I designed, the body /engine tubes, and nose cone. Instead of using separate glue tabs/joiners, I’m building them into the parts themselves. Although it leaves raised seam areas, the parts maintain a more rounded appearance, and at this size, the paper can be press-flattened to mesh the seams almost flat. It should also give a stronger structure, and definitely easier and quicker to assemble- I hope? Hopefuly, this post attached a small copy of the main body parts sheet. YES!- If completed the kit will be made available to everyone- provided it has a host.
I also have tentative centering rings made up, but of course need actual parts to test fit them. I’m working on all the fin parts, mostly by cleaning up the parts sheet from Jim Z’s and clarifying it. Hopefully that should be done this week, and then I’ll just be waiting to print up the sheets and build an ALPHA version based my theoretical assembly ideas.
Next post will be when I get to that point. SEE YA!

AX’E:rock:

ALRIGHT! I finally got my ink early Monday afternoon, and as soon as time permitted, got to work printing up parts. :beer:
Up till now, I have been plugging away at re-drawing parts for paper type cut out/construction, and improving things somewhat, but without being able to print anything, it was all theory till today.
WOW! :banghead:
It’s amazing how much looks good on screen but doesn’t work when you actually try the build. Other than minor re-sizing of the centering rings, and a slight change to the motor mount; the nose cone needed an overhaul! The design I picked to round out the tip left too much slop, and the petals wouldn’t properly close. Although only 4 pieces, instead of the original 6, it took over so minutes to try to shape the tip, and it wasn’t going well, causing much frustration! This, obviously, is neither easy nor fun! BAD DESIGN!
I instead opted for a 5 piece nose, with smaller vertical cuts at the tip. Even with the extra cutting and gluing, the nose was far easier to assemble, and the petals of tip almost closed themselves. I like it, anywayJ
The picture shows the original nose at the left, the trial upper nose section that didn‘t work as I hoped, and the assembled 5 piece version of what I intend to go with on the kit.
At this point, l'm final sizing the Centuri parts, and fitting them as necessary Fortunately, because of the decal layout, not all pieces have to be made with 2 printed sides.
Next up, fitting everything together. My definition of an ‘ALPHA’ is to have all the parts fit properly. Then it will be time to paint, which I have already been looking at, and it’s posing challenges all it’s own, due to the decal scans I obtained. I’m getting way ahead of where things are in the design process as a thread, so I’ll elaborate on that later...:date:
OK! Next up- Fitting it all together!

AX’E :thrasher:

This is great. Flying card models is a small segment of model rocketry and we get to see the designer work through his plans and drawing to final construction. Cool stuff.

Your rounded cones are really interesting, but I've never been able to get them to work right. I always just use a rather blunt cone for the front segment (as in your first cone on the left). Just how do you get the durned things to look so good and smooth?

boo!

Well, the real world is cutting in on my play-time, so I'm cutting this thread super short:
everything is fitting together mith minor changes. Just needs a test flight to double check everything. the 3 layered cardstock fins are definately thick enough for the job. As soon as I finish decorating/and putting it into kit form, it may be coming to a website for downloading by anyone who wants a copy.

I'll be hiding back under my rock now- Take care!

AX'E

AX'E said:

I'll be hiding back under my rock now- Take care!

AX'E

Click to expand...

Eric,

Don't stay under too long.. Come back and visit once in a while.. We'll be here.

Try here for double checking your plans. Good Luck!

https://www.dars.org/jimz/cen2150.htm

OK! Back on the net for a bit… Not to long though, I only have 10 hours per month, (Net-Zero free service), and I burned up much of it doing taxes and such. I’ll need time to load up this model later this month to send to Wayne Hill, who has offered to host it. https://rocketry.wordpress.com/

The ‘ALPHA’ version of the parts worked well, with minor sizing modifications. Of course I painted (placed) EVEL in the cockpit. I thought he’d enjoy the test flights, which went perfect! Fully loaded for flight with an Estes A10-3T, the model weighed in at just under 1.5 ounces. Using the Estes A10-3T, I had only 2 motors at the time, both flights went to about 350ft, with a slight clockwise rotation of about 1.5 revolutions each time. The model did fly noticeably slower than the first version, obviously due to the heavier laminated parts, and compensatory nose weight. The only difference between the two flights was where the rocket actually landed, due to the wind. The pictures are 'BEFORE FLIGHT' photos
That accomplished, I moved on to painting the parts for the ‘BETA’ version.

AX'E :thrasher:

I promised more about the challenges of painting this thing, and here it is:
WHAT A CHORE! :argh:
To begin with, the decals on Jim Z’s site were yellowed, and ‘almost’ unusable. Fortunately, over at YE OLDE ROCKET SHOPPE, https://www.rocketshoppe.com/ , on KURT’S DECAL PAGE, https://www.rocketshoppe.com/decals.htm , I found a very nice neat set for the sky Cycle that Kurt? (his work?)- had put a lot of work into. The only hitch, was that Kurt, used a beautiful shade of Pantone instead of the Gold coloring on the originals.
Metallic colors, for the average household printer, are something of a Holy Grail! Gold is one of those colors that is really tough! I wanted to simulate a Gold Paint color. One of the ways to simulate metallic’s, is to find, or take a photo, and use patches of it where needed. Other’s are to find a color code already in existence, or use part of a photo that looks good. This is tough because usually any metallic color simulation is made using pixilated patches of several shades of color. I didn’t find any listed color codes I liked, but did find a photo of a gold painted BB-gun someone was proud of enough to put on the net! One section of the image was very consistent and not heavily pixilated. I got an RGB code, ( R204-G170-B125), and used it. I thought it looked good in print as well, so I replaced - Pantone with the Simulated gold color. How many hours this took, especially with Dial up service looking through Google images? It was in the double digits!
Other decals I modified to look more like the photos of the Centuri built model, increasing the 6 red wing stripes to 8 and changing the spacing, resizing-reshaping others to fit better-etc. Of course, I also designed a few of my own.
Anyway- it’s painted, and I’ll be assembling the BETA this weekend.
I’ll post more soon-net time permitting The images are of the current painting scheme, I couldn't decide on the fianl Main Fin scheme, so there's a poll. https://www.rocketryforum.com/showthread.php?t=43041
You get to vote! LOL

AX’E :thrasher:

Looks great! I can't wait to build one!

Eric,

Looking good! I'll be building one for sure!

OK! I have the BETA completed. :dancing:

I had to do a few last second teaks to the design, nothing major, or even worth mentioning. (code for something really embarrassing I forgot) :shot:
The weather and circumstances here have thus far kept me from being able to launch it, but I’m hoping to do so tomorrow. Getting pics of a launch is tough. I could do the ubiquitous rocket on the pad photo, but there’s no proof it flew. My cameras are really not good enough to catch it in the act, and I have no site for a short video. If I tell you it worked, would you all trust me? :d I’m sure it will as the only mod I did from the ALPHA was to simplify the motor mount by leaving out the original shock chord attachment, and choosing a simplified Estes type instead. (Paper mounts glued to the frontal inside of the body tube, and another in the nose cone, as opposed to a mount intense cone, and the fancy Centuri motor mount set-up as listed in the instructions.) It cuts out almost 30-45 minutes of assembly time, and works for my desire to keep this as simple a model to build as I can. I’m really trying to keep this something that beginners can build, and yet be more than a 3-4 FNC. I hope this model will achieve my aims, but really may not know for years, or even ever, after the kit is released. Well- that’s not important. What is important, is that I hope this will be something fun and different; perhaps a bit nostalgic for us ‘aging’ rocketeers, and yet something of curiosity for the newer generations? I also would like to keep Evel Knievel’s accomplishments and memories alive. He was surely the bane of every parent’s existence in my time. I had several scrapes, bruises, cuts, from trying to jump my li’l Huffy over X-amount of wagons, or whatever. ( I got 3,:stickyman:. Same as my friends.) Well, if Evel could do it… He was also an inspiration , for me and my friends, at least, to show no fear and take on a challenge! That meant everything form quizzes/tests in school, to standing up to bullies! :boxing:
CHEERS Evel! I'll never forget you... :beer: Of course, it was Bob Truax that designed the original steam rocket motor for the cycle... Did I mention my name is Eric Truax?
Thank you Centuri, for the model, and to Jim Z’s for posting it, and everyone who posted information for this classic!
Next up the final launch report...

AX'E :thrasher:

Eric,

That model looks GREAT!!
:congrats::congrats:

I can't wait to build one!

That is one cool looking model rocket.

You rock Mr. T-R-U-A-X...

Looks awesome! You could always use Photobucket to host your video of the flight.. That's where I put all the photos and videos I post here! I upload them to photobucket then just link to the file from here in the post...

As planned for the BETA version, I left out the Centuri shock chord mount, and went with an ‘Estes’ style double tri-fold paper type. One in the body, the other in the nose. Without the extra weight of the shock chord, and mounting tang in the rear, less nose weight was needed.
Launch day was calm, with a 70’F temp, and very little breeze. Coming off the pad the rocket was definitely faster than the ALPHA version, and flew to what appeared to be a higher altitude, 400ft or so- FAST! Changing the shock chord mount may have helped boost the performance, so I’ll mention both types when I write up some instructions. The ejection came way too soon, before apogee. A 4-5 second delay would be better. I hadn’t filmed a launch in over a year, almost two really, and so had a bit of trouble. The camera setting wasn’t the best, and so the pictures are a bit grainy. There were 2 launches, and the rocket is still here, and will probably last for at least 5-10 more launches. I’ll probably give it away, as I want to build one more for show anyway.
Well that’s about it for posting on this model. Next time you see it, you should be able to download your own!
Thanks again for all the help, input, and encouragement everyone!

See ya next project and around the forum!

AX’E :thrasher:

AX'E said:

.... The ejection came way too soon, before apogee. A 4-5 second delay would be better.....

Click to expand...

Try using an A3-4T instead of the A10-3T. That's the 13mm motor I use the most.

I only use the A10-3T's on heavy or high drag models where the 3 second delay is about right.

EDIT: I looked at the motor data on the NAR website the A10-3T motors they tested only had an average 2.35 sec delay.

They both were really quick ejection pop flights....I heard the engine burning, less than a second of smoke then POP! I have trouble getting A4's. I have one pack, and they cost about 50% more, when I can find them, then the A10-3T- because that's what Wal-Mart carries! Most everything I build in 13mm needs the A4 as well. Maybe I can find a NET sale somewhere? I guess on the good side for this model- the A10 does work well if I use the original Centuri shock chord configuration....lol
TY for the info Bob...
edit- I'll try and get a flight video out, but NET-ZERO is not letting me load any attachments.

AX'E

I generally get A3-4T's at Michaels with a 40% off coupon which brings the price down to $4.80.. about the same as Walmart charges for the A10-3T's.

Since I have to pass right by a Michaels on my way home from work, it's no problem for me to pick up a pack of motors whenever there is a coupon in the mail.

It's been 6 months since I've been in the Michael's in Gainsville (fl) They stopped carrying rocket supplies in 2006, I bought em out of the motors then. In fact I'm still saving a few.
....Come to think of it...I'm the only person I actually know who does anything with rocketry in the area! OI!

AX'E said:

[Snip] Come to think of it...I'm the only person I actually know who does anything with rocketry in the area! OI!

Click to expand...

I am in your area! ha.

Well I have not done anything in rocketry in a long while, so you maybe are correct.

I do the same as Bob, use Michaels coupons for motors. In addition, there are a few good online vendors. I have had luck with hobbylinc. They sell A3-4T motors for $5.09 plus shipping, of course.

A3-4T MINI Model Rocket Engine (4)

I also agree with Bob, the A3-4T makes for the best motor selection for most lightweight flying paper rockets (card models).




Mike