vcp
Well-Known Member
I had the Mini A Heli worked up as a 3D print for NARAM60. Have to dig it up and get it posted.
Mini A Heli modification: no burn string
- Thread starter neil_w
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In the home stretch now. I was happy that when I went to check on the rocket today, there was no evidence of stray epoxy and the mechanism operated smoothly.
Next up: the hold-downs for the rotors. Here's one of them:
The curve in the base piece was formed in the usual way, with a piece of 220 grit paper wrapped around a spent motor.
Here they are on the rocket:
...and here's a pic showing a (dry fit) rotor in position:
All that's left to do now is glue in the rotors, and maybe clean up the Sharpie job on the front section of the rocket, which has suffered quite a bit from all the handling. Shoulda waited until after assembly for that.
Next up: the hold-downs for the rotors. Here's one of them:
The curve in the base piece was formed in the usual way, with a piece of 220 grit paper wrapped around a spent motor.
Here they are on the rocket:
...and here's a pic showing a (dry fit) rotor in position:
All that's left to do now is glue in the rotors, and maybe clean up the Sharpie job on the front section of the rocket, which has suffered quite a bit from all the handling. Shoulda waited until after assembly for that.
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.
I don't quite buy the "lazy" part, but I can definitely see the appeal in a rocket with near zero flight prep. No wadding, no parachute to fold, no stubborn shock cord to stuff into BT-20, etc... I'm starting to think about prepping rockets for Red Glare in 3 weeks, so a heli like this seems like the best thing since black powder.
There's a reason I bring my Quinstar and/or Cyclone to almost every launch...
I launched a mostly 3D printed heli that simply used piston ejection. Very simple mechanism. The tip of the fins slip inside the NC, Ejection pushes NC out to release them. It flips over and comes down nose-first. However it lawn darted on me and shattered. I think the plastic parts were weak, the ejection charge or air stress snapped the hinges. And I need stronger fins. Those were shattered also.
I think the hinges broke at apogee and the wings shattered on impact. best guess.
It was one of my early 3d projects. I might print it again with better material.
Thingiverse heli rocket
I think the hinges broke at apogee and the wings shattered on impact. best guess.
It was one of my early 3d projects. I might print it again with better material.
Thingiverse heli rocket
I am fully prepared for mine to blow apart on the first flight. Have been considering ways to improve it for v2.0 that will mitigate that risk. But who knows, maybe it'll hold together. It would be nice to get one good flight in.
vcp
Well-Known Member
stl files for the Mini A Heli parts I'd done. This was intended for a push off the nose/hinge section, with the blades clipped at the fin unit. The OpenSCAD code file is attached. I think it contains the code for all of these bits, but it's not formatted/commented for easy use. Fiddle with it at your own risk. Pics to follow.
vcp
Well-Known Member
This shows a blade slotting guide for cutting the slot for the swing arm, the swing arm itself, and guides for gluing/forming the blades.
Fin unit has integrated clips for the blade tips, and support for the fin trailing edge is included. I think I printed this in vase mode, ABS.
The hinge unit is printed upside-down. Support is included. The hinge pins are just a length of 1.75mm filament. Cut that bit of filament so that about a 1/8" length protrudes on each side of the hinge unit, then heat stake it with a soldering iron tip, to 'mushroom' it on each side. No glue in the hinge that way. I looked at those stacks of cardboard bits and just knew I'd make a sticky mess of it. This is clean and everything is aligned perfectly.
Nose section glued to top of hinge unit. Print vase mode.
Last edited:
vcp
Well-Known Member
BTW I did print all of those bits with pretty fair results, but never got around to attempting a flight. I've probably still got the prints around here somewhere; pics if I find them.
Very nice, those clips are basically what I fashioned more crudely out of balsa.
Finishing up:
I attached the rotors, and added a bit of CA coating a few places that are likely to get handled a lot. And, as promised, fixed up the Sharpie at the front:
Everything fits together nicely. Final weight is about 2.5g heavier than the facecard value, which makes sense for the stuff I added. If I were doing this again, I would have needed to add less stuff (like that ridiculous cardstock wrap at the front).
On minor annoyance that I discovered:
My hold-down clips cover part of the tail where tape is applied to hold in the motor. Only 1/4" is left exposed (now coated with CA, natch). I don't have any concern about it having enough contact area to hold, but I'll have to cut the tape narrow to fit it in there. Another fix to be made in a 2.0 version, should there ever be one.
I attached the rotors, and added a bit of CA coating a few places that are likely to get handled a lot. And, as promised, fixed up the Sharpie at the front:
Everything fits together nicely. Final weight is about 2.5g heavier than the facecard value, which makes sense for the stuff I added. If I were doing this again, I would have needed to add less stuff (like that ridiculous cardstock wrap at the front).
On minor annoyance that I discovered:
My hold-down clips cover part of the tail where tape is applied to hold in the motor. Only 1/4" is left exposed (now coated with CA, natch). I don't have any concern about it having enough contact area to hold, but I'll have to cut the tape narrow to fit it in there. Another fix to be made in a 2.0 version, should there ever be one.
Thanks for the build thread @neil_w I just finished mine the other day. First attempt at something like this so I enjoyed seeing how someone else might modify it. It's definitely not for fat fingered folks like me but I managed to complete it without too much hassle.
@vcp If I had started my build a week later, I might have given your parts a tryout.
@vcp If I had started my build a week later, I might have given your parts a tryout.
Here's the finished rocket in flight configuration:
Because the rotors are thin, and only held down at the tips, they bow out a bit under pull of the rubber bands. I checked this early in the build, and decided that it's OK, since the rocket isn't going to spend much time in this state.
I once again tested deployment by giving a stiff puff of air into the end of the tube, and it seems to work fine and dandy. Sorry, not enough hands to take a video.
It is now ready to fly.
Because the rotors are thin, and only held down at the tips, they bow out a bit under pull of the rubber bands. I checked this early in the build, and decided that it's OK, since the rocket isn't going to spend much time in this state.
I once again tested deployment by giving a stiff puff of air into the end of the tube, and it seems to work fine and dandy. Sorry, not enough hands to take a video.
It is now ready to fly.
Alright, hope you manage to get a video (or at least pics) on the first flight. That's a fun one. And hope you get to launch sooner, rather than later.
You've got a fair bit more bowing out then I had, how much camber did the rotors take?
(P.S. Red Glare is in 2 weeks!)
You've got a fair bit more bowing out then I had, how much camber did the rotors take?
(P.S. Red Glare is in 2 weeks!)
Definitely. This one I'll be taking video on the maiden flight for sure.
You mean more bowing when you hold the rotors down with your fingers? With the string tied up it shouldn't bow at all. That's one of the disadvantages of the hold-down-at-the-end scheme, but I couldn't think of any reasonable way to have the hold-downs operate in the middle of the rotors without making significant design changes. Maybe I can come up with something for v2.0.
My rotors took very little camber, although I bent them according to the directions. I'm fully prepared for it to behave more like one of @BABAR 's airbrake model than as a helicopter.
Jealous.
Ah, yes. I've already forgotten the details of the stock build. You're right, with a string near the middle it will be pretty flat.
Mine were the same initially, I wasn't really satisfied with the lack of camber so I made deeper cuts (not just a score line) and reglued the rotors so that they held nearly the full camber of the cardstock template. It may not have been necessary, but it flew great (and heli'd off into the wild blue) on its first (and only) flight. This would be a model I'd rebuild.
I'm looking forward to flying it, and I would gladly build another if it doesn't come back.
One thing I'm curious about: why is the A10-3T the only recommended motor? It's .8 oz, should fly fine on a 1/2A3-2T, shoudn't it?
That's a good question, I have no idea. The 1/2A3 might improve your odds of a recovery on the first flight.
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May be a bit late for this. As I understand it, your piston at the front pulls the rotors forward releasing them from fixed position retainers at the base. Wouldn’t it be easier to have the piston at the REAR, pushing the rotor restrained BACKWARD and releasing the rotors that way? This is basically the Texas Twister approach. You can almost do it with near zero weight penalty. Cut the body tube just below the forward end of the motor casing. Attach your rotor retainers to this cut segment. Run a small segment of kevlar connecting the segments, you will need to tuck the slack somewhere on launch but many easy options.
at apogee, motor ejects with the the retainers, it will dangle from the Kevlar (a swivel wouldn’t hurt).
you really want to take weight off, remove the central segment of the body tube and replace it with a carbon fiber rod.
at apogee, motor ejects with the the retainers, it will dangle from the Kevlar (a swivel wouldn’t hurt).
you really want to take weight off, remove the central segment of the body tube and replace it with a carbon fiber rod.
There are two sections of the rocket: a front section that includes the rotors, and the rear section that includes the retainers. There is no meaningful distinction between saying that the front section moves forward, vs. saying the rear section moves backward. The two sections move away from each other. The only difference you're describing is having the separation between the two sections towards the back rather than towards the front. I chose to use the existing cut in the body rather than create a new one; that happened to be towards the front of the rocket.
I crunched my heli Saturday ... I need to replace a few inches at the rear and the nose piece. I taped over the big string holes because they burned my rotors last time. Overcompensated
The string burned but got caught on the tape and didn't release the rotors.anyway, when I thought about fixing it, I came up with the very thing you said here. Kevlar thread attached to the fin can. We'll see how it goes
Sorry to hear things didnt go as planned.
Pardon a dumb question . . .
Why is a Helicopter Recovery model in the Glider Section ?
Dave F.
Why is a Helicopter Recovery model in the Glider Section ?
Dave F.
re-construction in progress. top piece replaced. I dont know if it's actually needed for stability so I replaced the tube just to be sure.
motor is stuck and i crunched the BT trying to pull it out, so it's getting replaced also, except this time with a kevlar thread attached to the engine block.
When a Boost Glider experiences "helicopter" recovery, it's usually a "Red Baron" . . . LOL !
Dave F.
Flew the rear-eject yesterday. Flight 1 was beautiful. worked flawlessly.
Flight 2 had a red baron, the tail was hanging over a blade. dont know how that happened. bounce?
need to shorten, really shorten, the tail attachment string.
Flight 2 had a red baron, the tail was hanging over a blade. dont know how that happened. bounce?
need to shorten, really shorten, the tail attachment string.
My modded Mini A Heli flew twice yesterday, and deployed perfectly without blowing apart. Success!
The first flight was on a 1/2A3-2T, which is not a recommended motor but I couldn't think of any reason it wouldn't work. Indeed, it wasn't very high but a perfectly satisfactory flight, with nominal deployment and a good helicopter descent. On the second flight I tried an A10-3, which was fine except it recovered upside-down, which works but doesn't spin as fast. I don't know if the motor choice played a role in the descent orientation; I'll keep an eye on that in the future.
The only slight cautionary note is that the slide mechanism feels a little rougher than before. I'll have to keep an eye on that as well. The current model is not build to allow disassembly or any cleaning or maintenance of the slide. I've thought about that a bit but haven't come up with any ideas I really like yet.
Overall I'm very happy with this mod. It works, and made flight prep a 5-second affair: fold the rotors, slide into place, load motor and go.
Here's a lousy video of the second flight. Tracking with a smartphone is pretty difficult and I'm very much out of practice; somehow, amazingly, I kept the rocket in frame the whole time, although I had no idea at the time.
View attachment IMG_1445.mov
The first flight was on a 1/2A3-2T, which is not a recommended motor but I couldn't think of any reason it wouldn't work. Indeed, it wasn't very high but a perfectly satisfactory flight, with nominal deployment and a good helicopter descent. On the second flight I tried an A10-3, which was fine except it recovered upside-down, which works but doesn't spin as fast. I don't know if the motor choice played a role in the descent orientation; I'll keep an eye on that in the future.
The only slight cautionary note is that the slide mechanism feels a little rougher than before. I'll have to keep an eye on that as well. The current model is not build to allow disassembly or any cleaning or maintenance of the slide. I've thought about that a bit but haven't come up with any ideas I really like yet.
Overall I'm very happy with this mod. It works, and made flight prep a 5-second affair: fold the rotors, slide into place, load motor and go.
Here's a lousy video of the second flight. Tracking with a smartphone is pretty difficult and I'm very much out of practice; somehow, amazingly, I kept the rocket in frame the whole time, although I had no idea at the time.
View attachment IMG_1445.mov
