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RUBBER POWERED HELI DESIGN 101 (Read 1181 times)
Reply #15 - Jun 11th, 2017 at 8:05pm

Ray_K   Offline
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6-11-2017

Hi Mario,

The Hiller kit was a full and complete kit it has all laser cut parts, Cad drawn plans, vac formed canopy and engine housing, water slide decals, pre-formed rotor blades, all hardware, wire and bearings and a full instruction manual.

Cheers, Ray K.
 
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Reply #14 - Jun 10th, 2017 at 12:21am

Mario I. Arguello   Offline

Vintage MIA Scale R/B
Powered Helis

Posts: 13
 
How did your Hiller Kit come?
In parts?
Pre-assembled?
Any photos of the kit contents?

My MIA MD500 R/B Kit came in similar with balsa, mechanics, rubber, plan, like on this simpler MIA Feather R/B Heli kit photo attached.
 
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Reply #13 - Jun 9th, 2017 at 10:40pm

Ray_K   Offline
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6-9-2017

I hope you do not mind all the questions about your models I find them fascinating, when I first saw your RB 500 I wanted to get one but never did so I am trying to re-create it just so that I could have one.  Smiley

Cheers, Ray K.
 
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Reply #12 - Jun 9th, 2017 at 10:31pm

Ray_K   Offline
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6-9-2017

Hi Mario, I have been working on the Huey since October of last year, I work a lot at my full time job so I build when I can.
I am looking for flight times of around 30 seconds or better.
There was no real lift issues, the Huey is tail heavy so when she started to lift she went backwards, I re-balanced her, I did not put no where's near the winds that I could have, the videos you saw are all only low power tests 400 hundered winds, she can take up to 1500 to 1800 winds.
Kit cost depends on if I do a full laser cut kit, or if I just supply plans, patterens and full pre built transmission system, if I do the full kit it would go for around $50 to $60.
My Hiller kit sold for $60.

Cheers, Ray K.
 
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Reply #11 - Jun 9th, 2017 at 9:30pm

Mario I. Arguello   Offline

Vintage MIA Scale R/B
Powered Helis

Posts: 13
 
Thanks Ray .. Smiley yes, I have done work with gears  and a host of other contraptions just to try it back in the day. This was also the time I started doing the micro free-flight and rc palm size helis, autogyros, microlights, and ultralights, so there was a lot of mechanical parts cross-polination among all these projects. 

Gears that were light enough were hard to come by and you may remember American Science Center in Chicago always had a great selection of interesting gears, cheap, but never the size required. I did find some gears made of thin phoenolic and I bought the whole lot, to try them in experimental projects, which eventually worked great for spur gears, not just on some of some of my early electric rubber helis, but also free flight, rc palm-size helis ... 

Great Huey!

How long did it take you to build the scale huey? 
What type of flying time were you shooting for?
Have you resolved the lifting issues in your videos?
What do you think your Huey rubber powered model would cost in kit form?   



« Last Edit: Jun 10th, 2017 at 12:24am by Mario I. Arguello »  

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Reply #10 - Jun 9th, 2017 at 4:23pm

Ray_K   Offline
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6-9-2017

Here is my R6, my Jet ranger and the vintage aero.

Cheers, Ray K.
 

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Reply #9 - Jun 9th, 2017 at 4:21pm

Ray_K   Offline
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6-9-3017

Very nice Mario, I see you have done work with gear drives too, here is what my new gear box looks like and my current Huey project, the Huey is 30 inches long with a rotor DIA of 28 inches. Keep the photos coming, it's nice to see other helicopter work out there besides my own. Well done.

Cheers, Ray K.
 

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Reply #8 - Jun 9th, 2017 at 3:33pm

Mario I. Arguello   Offline

Vintage MIA Scale R/B
Powered Helis

Posts: 13
 
Forms of Powering a Rubber Powered Helicopter

There are several ways to power a rubber powered helicopter and the ideal is dependent on the type of model we are building and what we are trying to achieve with it.

Powering strictly for Performance

Basically requires consideration of "flying weight". This can lead to a very minimalistic structure  and one can actually get away with a very simplistic, few or even single long strand of rubber of the appropriate thickness and  more importantly type of rubber. 

Note: Just because it says "rubber", does not mean it will provide efficient number of turns per length and thickness. There are a number of rubber manufacturing formulas out there and the best is the one you can select after trying various types and see which one you can extract the most energy and and flight time from by trial and error. Treating the rubber also depends on what type of lube you use to soften the material and get the most number of winds.

Powering for Scale Flight

Requires once again consideration of flying weight, but also structure and depending how clean we want the structure to be, (consider this as how a 3D CAD model is built by polygons), the more polygons the more resolution and the more detail, but also the more weight.

A a scale-ish frame, less polygon air-frame points,  one can easily and efficiently get away with a vertical mounted, non geared, looped strands of rubber, but this also depends on the rubber type.  Or with a geared set up if the model requires high torque as well as RPM. 

If the desire is more in-scale with more polygon air-frame points structure, we start to get into a more elaborate rubber motor mechanical arrangement, either vertically or horizontally placed motor mechanics and rubber strands and it may even call for "stretch-winding" to get the most turns out of x number of strands, x in length, x in thickness,  but note this has a compromise of less torque and this is very important to keep in mind in a Rubber Helicopter Scale Design and there is a lot more to consider than just making a pretty structure if you are after a model that provides satisfying realistic flights.

Point of Rubber Power Energy Equilibrium

The trick is to find a point of balance in the rubber motor, (strands, loops, mechanical components) and
the type of air-frame we want to power.  Traditional rubber, as used for powering stick and tissue airplane models, is never consistent from batch to batch and we can never set a fixed specification, in other words no two models will have the same energy, even when built using the same rubber, from same batch, as the rubber may have different atomic properties at different sections of the material. But, in general, we can say we can expect somewhat similar energy results.

An analogy to this would be that of an electric BL motor, depending on the type of copper, (made with or without impurities) size of wire, number of copper winds, single or double stacked, and  finally the type of magnets, core/armature materials and motor construction precision.
 
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Reply #7 - Jun 8th, 2017 at 10:44pm

Mario I. Arguello   Offline

Vintage MIA Scale R/B
Powered Helis

Posts: 13
 
... a few more, for the time being. I have to keep scanning old photos, as time permits will post more.
 
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Reply #6 - Jun 8th, 2017 at 10:29pm

Mario I. Arguello   Offline

Vintage MIA Scale R/B
Powered Helis

Posts: 13
 
more old photos... no particular sequence...
 
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Reply #5 - Jun 8th, 2017 at 10:26pm

Mario I. Arguello   Offline

Vintage MIA Scale R/B
Powered Helis

Posts: 13
 
Hi Ray,
Nice helis you got there also.  30 secs is about average for a rubber powered heli in scale. I don't recall the exact flight time I got with the bell 47G but it was under 1 minute, with a slight breeze. The use of the double row geared box helped with torque and speed, because the rotor was close to 2ft in diameter. This also helped sustain the heli in the air longer than expected.

Some more old photos scanned with a cell phone. I had to dig out my box of old photos, it's been that long!

 
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Reply #4 - Jun 8th, 2017 at 6:56pm

Ray_K   Offline
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to create that which never
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Posts: 255
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6-8-2017

Here is a picture of my scale Hiller Commuter, she fly's quite well, average flight times are around 40 sec's. My Vertol sea knight can do 30 + sec's. 

Cheers, Ray K.
 
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Reply #3 - Jun 8th, 2017 at 5:45pm

Ray_K   Offline
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to create that which never
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Posts: 255
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6-8-2017

Mario, this is a great looking Bell 47, did this fly? What was the weight of this model, what was the rotor DIA, what was the average flight time, do you have a video of it in flight.

This looks pretty scale to me, well done  Smiley, would love to see more.

Cheers, Ray K.
 
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Reply #2 - Jun 8th, 2017 at 2:16am

Mario I. Arguello   Offline

Vintage MIA Scale R/B
Powered Helis

Posts: 13
 
Designing for Kit Sales and Personal Use

When you embark on making flying model products for sale, performance and primarily cost is key and sometimes this requires a bit of a tradeoff in looks.   

I have always been a performance seeker first, while employing durability and realism next. However this has not stopped me from making scale helis that are more easily recognizable and better suited for rubber.

My goal when I started designing Rubber Power Helis, was never to offer museum quality replicas of the real thing, because the cost would have been prohibited for the average consumer and I was really after trying to understand the complexities of real helicopters more less and move on to other projects that I was working in parallel with these helicopters while maintaining a balance of family life and a regular day job career. 

So I elected to start off with simple heli kits,  like the MIA Moskito 123™, the MIA Feather™, and the MIA Shark™, while keeping the more 3D scale like and full scale helis, for self enjoyment.  But I  decided to offer simplified versions of scale models in kits. Kits like the MIA MD500R/B, Bell 47G, Bell Huey, Bell Jet Ranger, Hughes 300, I even offered some freestyle helis, like the MIA Scorpion, MIA Exect 90 both designs inspired by the real Heli Kits made by Rotorway International. Somewhere along this list I also did giant size rubber powered helis just to try it out. Piaseky (banana style helis) twin rotor, I did not do coaxial helis as these were never attractive to me,  they posed no real challenge in design,  it had been done before in the more traditional ways stick and rubber and I really wanted to challenge my self with making the more typical and easily recognizable small rotor on tail type helicopters, thus the MIA Bell 47G-S R/B I have attached photos below. I did some other ones in various degrees of geometrical frame complexities and  one which I intended to produce in kt but never made in kit called the MIA Dart™.



« Last Edit: Jun 11th, 2017 at 2:42pm by Mario I. Arguello »  

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Reply #1 - Jun 7th, 2017 at 8:45pm

Ray_K   Offline
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to create that which never
exsisted before.

Posts: 255
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6-7-2017

I agree with Mario that the more structure you have the more weight you have to lift and the more power it will take to get the model to fly. I myself tend to overbuild but to me there is something about seeing a scale model helicopter fly even thou it is for only 15 to 20 seconds it is well worth it. I do need to keep this in mind when I design something, I am working on a new light weight structure, bare bones minimum but it is scale. More to come.

Cheers, Ray K.  Wink
 
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