Worth it starting a Scratchbuild Heli thread?

[HobbyCAD]

Hi Guy's,

I've been following the forum for a while, and it seems to me there are not many homebuilt "driven rotor" enthusiasts out here in Australia. Maybe I'm wrong, but the rate of posts sure tells me Gyro's are king in the rotorcraft department.

I've had a few years of Bensen B-80 experience, but have always been lured to tackling a heli project. Most of you will tell me I'm crazy, and let me tall you, everyone I tell my intentions to, says just that !! But Einstein said, If at first an idea does not sound absurd, then there's no hope for it !!! We'll, then mine is going to be a great success.

What is it that keeps so many rotorcraft enthusiasts away from building a helicopter? The fact that there is no RA-Aus license for it, the fact that one has to do a full license in at least a Robbie, the fact that somehow the safety record looks bad, the fact that it is expensive, or all of the above?

I have been tinkering with little "starter projects" for years, and have now finally decided to initiate a build project. I would like to know if there are any fellow enthusiasts out there, that would like to join me in my quest. Not only from scratchbuilders, also some of the Rotorway builders out there, the Mosquito's, HeliCycle's and Mini-500's.

For a first project, I intend to take Mini-500 components, the M/R transmission, the T/R transmission, the complete control system, a 100HP 4-stroke, and build it into a Cicare open frame fuselage. This seems to me the best way to go at first. I would like to hear some comments from you guy's out there.

Attached some pictures of a similar project.

Regards,

Francois

[MechFx]

I'm a bit of a Heli fan too.

For a first project, why not just build a proven kit ?

all the bugs already sorted and established flight performance ?

is it possibly a "Journey as important as the destination " project ?

I have a few Aussie homebuilt Heli videos on Youtube if you want to have a look. YouTube - mechfx's Channel

I can put you in touch with the owners if you PM me.

cheers Art

[HobbyCAD]

Hi There Art,

Thought about starting that way, but decided against that. Not too many options out there. A600 Talon, way too expensive. RW-162F, also expensive, and what people do not want to hear, or believe, bad crash record. Mosquito and Helicycle, not much bang for your buck. All the other stuff out there, AW-95, Scorpion, older Exec, Lonestar, Skylark, all marginal flyers. The best of the lot seems to be the CH-7 Angel, the Kompress, Baby Belle, and Talon. Just a bit too expensive. You will see I have not mentioned the Mini-500, it is a contraversial machine, but in my mind, has the biggest potential.

Just another thing that springs to mind, seems like in the field of Homebuilt heli's, all the comments and arguments out there are based, 30% on proven Engineering Principals, 60% on Personal Opinions, and 10% on Gut Feel. So many people shoot down the ideas, but they are all idle bystanders, guy's having nothing to do with it, have never tried it, just spewing garbage, because they think they know it all. I'll be the first to admit, I don't know it all, but I'm going forward in babysteps, making sure of my facts, every inch of the way. If I do run into dead ends, it's school money, I've learned something. I'm wiser after that, well on my way to do it right the next time.

If we manage to cut the crap of the Mini-500 history, you will see there is a 90% super machine packaged in there. The 90% comment is my own personal opinion, things I'm not comfortable about. Again I will say, what is "scary" for me, might not be scary for someone else. The Mini-500 has a super smooth control system, ask any guy that flies one, as well as the Angel and Kompress owners. Apart from normal teathing problems, there has never been any hassles with it. Some initial castings were drilled inaccurately, or bearings were of the wrong material. That quickly went away when the AD's were published, and the production line corrected. PROBLEM SOLVED after that. No need for anyone to point fingers to that part of the design again. The M/R Transmission is fine, again, bad SKF bearings in the beginning, after the AD's, no problem. The complete boom, tail and T/R transmission, no problem. The root of all it's evil, it's my own personal opinion, originated from the 582 2-stroke powerplant. It revved high, inducing all kinds of vibrations, shakes, harmonics, what ever you want to call it, into the structure. Therefore, the frame cracked. Not because of a bad frame, it was because of the high vibrations. Once the frame upgrades, and rotor mast supports came out, the problem went away, but you still had the 582! That motor caused not only the frame hassles, it just died on people, cuasing them to go into full down auto's. Now remember, these are single seats, no way to train for it. The low time pilots, facing a full auto, caused many crashes. Who is to blame, the 582 I would say, did not give anybody time to build up experience with the machine. An important point, at that time, there was no 4-stroke Rotax available, and the 618 only came out much later in the life of the Mini-500. A different angle, so why is the 582 flying so well in the CH-7 Angel ???

So what about the high time pilots crashing. My opinion is as follows. I understand that if you ask the first Mini-500 pilots, the machine would hover fine, but in high forward speed, it required a load of forward cyclic stick input. It wanted to sit back on it's bum when flying. I believe the semi-scale fuselage design had something to do with it. again, it's my personal opinion. To counter that, either the mast had to be angled, a large design change, not able to correct with a quick AD, or a trimtab, forcing the nose down. This was the option they went with, a nose down forcing tab. So, in forward flight, it would want to pitch back, the tab forced it forward, all seemed OK. But when the engine failed as suddenly as they did, no pitch back any more, but the tab stayed there, pitching it forward. That lead to some situations where it pitched over nearly 90 degrees, the pilot would instinctively full full back cyclic, the blades whacked the tail, the rest is fatal statistics. It bit the high time pilots as well.

I must add, for all the Mini-500 problems, there were good fixes. With proper training, it was, and still is, a good flying machine in standard form. Testament to this statement are the stacks of guy's out there still flying it with no hassles. It's an uphill battle trying to get rid of it's bad history.

So why not take all the good of a Mini-500, stick it in a new frame, and power it with a reliable power source. That's my idea. And I've been wanting to do it for ages. Now, I discover there is a man in China, that has done EXACTLY that. I'll post pictures in my next post.

I now have Mini-500 components. I'm going to integrate it into a Cicare frame, it will become a Cicare CH-6/Mini-500 hybrid. As a powerplant, I'm planning to use a 912S, drop the compression, and have it tick over reliably in the heli. Again, the Kompress 2-seater has beaten me to it, with the 914 flying in it.

Have to go now, will carry on with my story a bit later.

Regards,

Francois

[HobbyCAD]

Hi There Art,

Some more to give you some more insight into what I'm planning.

I've been wanting to combine the Mini-500 components with the Cicare CH-6 frame for years now. While searching the net for titbits of info, I came across this man in China, that has done EXACTLY what I was always planning on doing. Check out the following pictures. First, some of the Cicare blueprints. You will see the Chinaman used the exact Cicare console, rudder pedals, tailboom attachments, cyclic and collective control stick.

From the photo's, you can see the Blue Cicare parts. Have a look at the bare metal fuselage, the blueish tint metal is the original Mini-500 frame, and the darker tubing is the Cicare part that they mated to the Mini-500 frame. Once painted, it looks quite nice. I very much like such an open cockpit design. Have a look how they modified an Angel canopy, to be half open, now that appeals to me as well.

Some more in a next post

Francois

[HobbyCAD]

Hi There again, some more info to share.

Firstly, a picture of how an American guy did his open frame Mini-500 conversion. Secondly, some pictures of basically how nice a Rotax 912S wil fit into the rear of a Mini-500 frame, yes, some minor frame mods required. These pictures are of the Kompress 2 seat frame, with a 914 in it.

For the future, I'm thinking of using the same seating arrangement as the Kompress, with the "lightweight" pax sitting straddled in the rear, much like the weightshift trike microlight seating. I feel the need to make arrangements for a passenger, but without the complications of dual controls. The idea is to take someone along for a ride, not to have them fly it. A single control arrangement makes matters much easier. Also, dual controls forces us to go for "side-by-side" seating. It has a large effect on CG, having one up, or with a pax. That "shifting around the lead weight" affair of the Rotorways. I am going to move the pilot seat way forward, and design it for perfect CG, with my weight. The idea is for the pax to sit right back against the mast, thus having the least effect on CG. With a pax, it will be an increase in payload, but a marginal shift in CG. What do you think about that?

Attached the pictures. The last one is of what parts not to use !!!!!

Regards,

Francois

[MechFx]

Sounds like a lot of work !!!!!!!

It will all be worthwhile as soon as the skids leave the ground for the first time.

I heard there are a few Helicycles in OZ in the build stage at the moment. so you should have some company in the sky.

Have you joined the SAAA yet ? There are a few people there that will be able to help along the way. They will have experience with VH experimental rego and build inspections etc.

I met one guy at the Cowra SAAA weekend this year that was building a twin engined (Blackbird motorcycle 112kw each) Coax chopper from scratch. Didn't catch his name though.

Art

[bones]

At least this guy has his head on right and is using a 914 in the machine, it has me buggered why these kits all seem to go with fuel hungry turbines or 2 strokes.

[MechFx]

Thats an easy answer.


The SOUND of the turbine

The $ of the 2 strokes. ( also I read that when the mini 500 was designed, the 2 strokes were the only things available )

4 stroke definitely the best choice nowadays.

cheers

Art

[HobbyCAD]

Hi There Art,

I also used to be under the "spell" of having a turbine heli. Maybe we all have this secret inner desire to be jet jocks !! You are right when you say, we are after the "Sound", also the "Smell". No one can disagree, it sure is a thrill to hear the thing spooling up. I went as far as sourcing 4 T62-32's. All in good working condition. The first sign of trouble was when I ran one on the bench, it guzzled fuel like it was going out of fashion. It made me sit back, and recalculate the practicality of going the turbine way. End of the day, I decided against it. I only had the -32's to base my findings on, not a -16 or 2A. On my -32, the calculations showed that with a tip-top condition turbine, I would need nearly 3 times the fuel than with a 912S. How do the HeliCycle guy's get around that. As it gets older, you have to burn more, to get the HP out of it. Also, after adding all the additional hardware, like reduction gearbox and controllers, it came out with no weight savings. The TBO seems for all practical reasons, much lower, and then, should it fail, or just hit a small snag, spares are a fortune, if you can find the part required. So, the 4-stroke won the battle.

Another comment, you always hear of guy's going for turbine conversions, but I never hear of guy's talking about their machines, a couple of dozen hours later. Lot's of You-Tube clips of new conversions, then that's it. Do they all run into snags after a couple of flights. The HeliCycle has support, that's another situation, but even there, I don't hear that it's the best thing since grated cheese !!

My take on 2-strokes for heli's, I have my own personal opinions, important, my own opinions. I can be right, I can be wrong.

Take a typical 2-stroke engine, you find them running in snowmobiles, jetski's, microlights, dirt bikes, and then in heli's. The typical version used for airborne use, seems to be premixed, ie the lubrication is part of the fuel supply. In a snowmobile, jetski, dirtbike and propdriven microlight, with full throttle, the motor rev's high, the fuel supply plentyfull, thus a lot of lubrication into the engine. Lower throttle, less fuel going in, thus less lubrication, but then, the requirement for lubrication is less, for the RPM's come down as well. High power = high RPM, low power = low RPM. Now take a heli, it has a fixed drivetrain, thus in flight, engine RPM is a fixed ratio to rotor RPM. On average, when you crank in the power, the RPM goes up, and soon, you have full rotor RPM, but way before full power of the engine. From there on, as you pull in the pitch, you add power to maintain the SAME RPM. So, in flight, you are juggling the throttle between 50% and 100%, to maintain the SAME RPM, as you change the collective settings. Let's take the situation where you have been using close to full power for a while, the engine is then nice and heated up, the pistons are nice and expanded, you are pumping in a lot of fuel, and thank heavens, with it, a lot of lubrication going in. Now you decide to come down, you lower the lever, as well as throttle down to maintain the same RPM. What happens, same RPM, same friction of the piston going up and down at the same rate, but a LOT less fuel going in, thus a lot less lubrication going in. Friction shoots up !! Add other possible situations in, such as a high engine temp due to a hot day, or a slight loss of engine coolant, or hot engine compartment, now is that not a sure recipe for a "sudden stoppage" due to sudden seizure!! This 2-stroke premix lubrication vs RPM issue situation is the big difference between the same type of engine running well in a microlight, but dangeriously in a heli.

So again, the 4-stroke wins my vote as the more reliable choice in a heli. Again, these are my opinions, and there might be ways to get past the lubrication issue, but it still stays a very tempremental setup. Too many parameters to keep lined up.

Regards,

Francois

[MechFx]

On my youtube videos, The yellow Helicycle was using at least 50 litres/hr and had a 45l tank. so short trips were the order of the day no way around it.

The same owner purchased and rebuilt the red CH7 I filmed at Cowra. running a 582 he has over 2hours duration.

Willi E has a CH7 that has a 618 motor, not sure of the fuel usage but must be somewhere in between.

Anywhichway you look at it there are a million different ways to get into the air.

When I started my chopper training, the ground school instructor threw a set of car keys across the room an jokingly pointed out thats an example of helicopter aerodynamics in motion ! Funny guy,

cheers

Art