Mini A Heli modification: no burn string

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neil_w

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Have there been any mainstream (or not) heli designs that don't involve a burn string *or* split into two tethered pieces? I'm envisioning something where the ejection charge shifts either the motor mount backwards, or the nose assembly forwards, just enough to release hooks that hold down the rotors.

My interest is purely for purposes of (a) cool mechanism, and (b) something that requires the absolute minimum flight prep. Not competition or anything like that. Seems like it should be possible, but I haven't put pen to paper yet. Wondering if anyone has done something like this.
 

neil_w

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Thanks, that's exactly the sort of thing I was wondering about (although I was thinking hinge-on-top). Do you know if it was a good/reliable mechanism? They seem to have abandoned it.
 

Antares JS

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Thanks, that's exactly the sort of thing I was wondering about (although I was thinking hinge-on-top). Do you know if it was a good/reliable mechanism? They seem to have abandoned it.
I had one that flew a couple dozen times before finally coming apart and breaking/losing pieces. 12 year old me didn't know how to properly prep a paper-to-plastic joint.
 

BABAR

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Have there been any mainstream (or not) heli designs that don't involve a burn string *or* split into two tethered pieces? I'm envisioning something where the ejection charge shifts either the motor mount backwards, or the nose assembly forwards, just enough to release hooks that hold down the rotors.

My interest is purely for purposes of (a) cool mechanism, and (b) something that requires the absolute minimum flight prep. Not competition or anything like that. Seems like it should be possible, but I haven't put pen to paper yet. Wondering if anyone has done something like this.
fliskits TiddlyWink

also


You’ve seen this since you posted to it. Estes Flip Flyer is designed as two pieces, but easily modifies to one piece.
Estes could have made that SOOOOOO much cooler if they ditched the entire Forward section and just extended the body tube, put the ring with the fin rod holders just Above the SHOULDER of the nose cone, lengthened the blades (with bigger fins to maintain stability), and just had a piece of Kevlar to hold the cone after ejection.

I guess technically it is Two tether pieces

my Helis and AirBrakes use two burn bands per flight (just two #16 rubber bands) but once you have done a couple of flights rigging them is really easy. They can fly with or without motor retention, most of them don’t even have a body tube or a motor mount.

anybody still using burn bands should try either rubber bands or elastic cord. It stays tighter and burns just as easy, and it self retracts once burned.
 
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BABAR

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Come to think of it, if you built something LIKE my imaginary Estes Super Extended Flip Flyer, instead of ejecting the nose cone, just put it on a piston with big (like REAAAALLLY BIG) side holes. Nose cone, ring with rotor slots, and piston slides forward but stays as one piece with the rocket.
 

neil_w

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fliskits TiddlyWink
Yup, that seems like a good example.

Tempted at some point to try converting the Mini Heli A to a mechanism like this (to re-use the hinges and rotors), but I'll probably build mine stock first, and consider future modifications.

Come to think of it, if you built something LIKE my imaginary Estes Super Extended Flip Flyer, instead of ejecting the nose cone, just put it on a piston with big (like REAAAALLLY BIG) side holes. Nose cone, ring with rotor slots, and piston slides forward but stays as one piece with the rocket.
I have a Flip Flyer sitting unbuilt in my basement, at some point I guess I should pull it out and have a look.
 

BABAR

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You could do the same thing in reverse, with the blade forward, the blade holder on the back with the motor mount On a piston.
Yup, that seems like a good example.

Tempted at some point to try converting the Mini Heli A to a mechanism like this (to re-use the hinges and rotors), but I'll probably build mine stock first, and consider future modifications.


I have a Flip Flyer sitting unbuilt in my basement, at some point I guess I should pull it out and have a look.
when you build it, do the one piece bit. No chute to pack, only one piece to keep track. If you build it stock, consider putting the coupler on the FORWARD piece and not the rear. In the rear, it messes with chute ejection.
 
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BABAR

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Consider sewn in double tape hinges. Cheap, easy, durable, and light.

see post 5

 

Scott_650

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I have a Flip Flyer sitting unbuilt in my basement, at some point I guess I should pull it out and have a look.
My modded Flip Flyer with the sections tethered together works well. I have one of each color combo with the r/w/b being tethered and the o/w/g original 2-piece style. For what they are the do work well - they’re not all that “sleek” but for the price they’re fine.
 

MadRocketer

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this is the mechanism I built for mine. It is a solution to a previous version that failed, but has not flown yet. The red beads have been replaced with tiny eye screws.
4A5D5BDE-5E57-4CFB-8A0A-4E8B01B528C8.jpeg

the blades are the body sections. Ejection charge pushes the assembly forward, disengaging the tabs that hold the body closed.
466414AC-E7A5-45B3-A636-4DA21AFD26D5.jpeg

this flew straight and true on a D-12. Then it broke apart on ejection and went back to the drawing board to be upgraded to the new mechanism
 

shockie

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or if you can't use the nose moving forward to release the blades, move the engine backward to release the blades. The engine compartment would have hold down wires and at ejection the engine compartment moves backward, allowing the blades to actuate....
 

afadeev

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Or buy a kit with a nifty Rotor Hub from here:

A fun and challenging build.
Unfortunately, the tolerances are too tight for humid NJ summers.
The blades were sliding in/out of airframe easily when I had initially built the kit. But by the time I brought it out for launch last summer, the rubber bands ended up snagging on the inside of the airframe during first launch, and the blades never ejected.
heli-roc.jpg

Rocket core-sampled, with minor damage.
Manufacturer suggested it was the user assembly error, and offered to sell me another kit.
 
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shockie

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Check out this PDF file . . .

Dave F.
when I first created my warped and formed helicopter blades back circa 2005, I first sanded an airfoil shape in the blade, and then after soaking them in ammonia/hot water bath, I placed them on a teflon mandrel and then wrapped them with Dunston heat shrink tape and stuck them in the oven to cure. about 150F
this was 1/32" balsa. once dried I coated them with a very thin coating of low viscosity epoxy resin, put them back on the teflon manrel and wrapped them once more with heat shrink tape and cured them in the oven again....... came out very stiff and light with a nice curvature in them......I sent a bunch of samples to Mark Petrovich for him to try out.....
 

mooffle

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I think a lot of designs that use a tether and hold down tabs could easily be converted to a piston design.

Here is my own design using a lego hub. The tube is certainly long enough that the shock cord could be a piston instead.
 

Amsterdam

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Neil,

The estes Mini-a is an okay candidate for a piston conversion, add hooks or something akin to a rail button to the underside of the blades to hook into the body tube or a reinforced clam shell designed specifically to accept the hooks / buttons at the separation point, id make the separation point where the burn string was threaded through. the hardest challenge is making a piston for Bt5, they burn up pretty easily
 

neil_w

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The estes Mini-a is an okay candidate for a piston conversion, add hooks or something akin to a rail button to the underside of the blades to hook into the body tube or a reinforced clam shell designed specifically to accept the hooks / buttons at the separation point, id make the separation point where the burn string was threaded through. the hardest challenge is making a piston for Bt5, they burn up pretty easily
Well first I'm building it (and will fly it for a while) totally stock, then will consider whether it's practical to modify it or just build a new one with alternate mechanism.

I'm not convinced a piston per se is necessary. The ejection charge should push just fine on the nose cone, just need to implement the ability to have the two halves of the rocket slide apart about 1/4-1/2" without fully separating. An unglued coupler and a piece of internal Kevlar to allow movement but not separation, would do it, but exactly how to attach the Kevlar internally at the correct length is something I've not figured out yet. Doing it externally would be very easy, albeit unsightly and a bit draggy.

I was pondering some sort of 3D-printed thing, but haven't worked out the details yet.
 

tab28682

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I am kind of partial to the burn thread option.

Have had several of these in 18mm size for B and C versions, based on the old QCR kiit. Very reliable and light weight for their size. Only takes a moment to prep the elastic thread holddown.

Actually won C Heli multi-round duration with one at a NARAM in the 1990s.

I do like the idea of simply using a longer coupler and an internal shock cord so that the model basically stays in one piece, though. Little tiny bit heavier than a burn string heli of the same size, but makes sense for a sport heli model.
 

neil_w

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Yeah, I'm not looking for competition performance here, a bit of extra weight is fine. I want something as close to zero-prep as possible, to make it easier to get more flights in. Also I'm lazy. :)
 

Amsterdam

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Well first I'm building it (and will fly it for a while) totally stock, then will consider whether it's practical to modify it or just build a new one with alternate mechanism.
unsolicited tips: use a sewing needle when threading the burn string, as for string choice.. people always say elastic thread and while that is the best, any finer sewing thread works.

Heli‘s are addictive! and it would be really cool to see what scratch designs you cook up if you get into them.

edit: my mini A build thread :Building an Estes Mini “A”
 
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Sooner Boomer

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Another idea that takes a lot of stuff going right to work...

Most heli recovery rockets have the blades attach at/near the nose. What if we turn it upside down. The blades aould be attached to an engine mount/piston that runs the length inside the body tube, with the blades attached at the aft end. In flight, everything is tucked (slid) up inside the body tube. On ejection, the piston and the blades would slide out the aft end (but not all the way out of the rocket). Once the piston/blades slide far enough out of the body tubes, the blades are free to swing out into heli recovery position. I remember seeing someone design/build something similar - a drag retarded bomb, with fins (panels) that were hinged at the rear.
 

Culprit

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I would love to see a scaled version of a Hellfire R9X with helicopter recovery.
8303C9AC-AB1B-4D50-996F-0B7344B5B598.jpeg
 

BABAR

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Another idea that takes a lot of stuff going right to work...

Most heli recovery rockets have the blades attach at/near the nose. What if we turn it upside down. The blades aould be attached to an engine mount/piston that runs the length inside the body tube, with the blades attached at the aft end. In flight, everything is tucked (slid) up inside the body tube. On ejection, the piston and the blades would slide out the aft end (but not all the way out of the rocket). Once the piston/blades slide far enough out of the body tubes, the blades are free to swing out into heli recovery position. I remember seeing someone design/build something similar - a drag retarded bomb, with fins (panels) that were hinged at the rear.
Definitely do able. If done with wooden blades, an issue would potentially be an inadvertent early or late deployment (like if the rocket weathercocks.) if the rocket is traveling at rapid forward velocity, the high air flow not only will help open the blades rapidly (good) but might potentially snap them off (not so good)

I had a similar untoward event that SHOULD have been forseen:facepalm:

two stage with 15 inch gap. Put a pod on the sustainer with a chute inside attached to booster. At separation the chute pulls out of the pod to recover the booster (long gap boosters tend to NOT tumble well.). What I did NOT consider was the velocity at staging........

yup, booster was essentially at Vmax for the stack when chute deployed.

7 of 8 shroud lines tore out.

it WAS a successful STREAMER recovery.
 

neil_w

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@GlenP told us about Apogee's Texas Twister

View attachment 450388
That one does have a piston mechanism similar to what I'm envisioning, would be interested to see exactly how it works. Anyone know?

I'll also note that it is quite similar in concept to a certain user's design that caused a bit of a brouhaha here recently.
 
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