Skeeter Jr.

Jincamty

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Te Kauwhata, New Zealand
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Home made helicopter
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Francois,

I don't understand. Did the original pitch horns have a problem with them?
Were there failures?
Why is a two piece 6061 pitch horn inadequate?
It seems like a waste of material and time machining this from one block of 2024, or are these being made just for the "Bling" factor.
I'm sure you could machine a two piece version for a tenth of the cost. And engineer it for a hundred lifetimes. :)

Cheers Cam.
 

HobbyCAD

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Hervey Bay, QLD, Australia
Francois,

I don't understand. Did the original pitch horns have a problem with them?
Were there failures?

The original horns were simply a bent steel plate. They may have been sufficient, but they may also have flexed. No-one knows, without instrumenting them for in-flight measurements.

Why is a two piece 6061 pitch horn inadequate?
It seems like a waste of material and time machining this from one block of 2024, or are these being made just for the "Bling" factor.

The 2-piece horn design is just fine, but look closely at what Joe Rinke added to them. He has introduced the drag link attachment. This is much better, and this is the upgrade that I'm after. This will enable one to remove blades, and re-install them without having to track again. The way the stock Mini-500 blade installation works is not optimum.

I got my set of 2-piece horns from a badly crashed helo. One horn was actually snapped off, the other was fine. I then got a second horn from Barney. When I bead blasted the 2 to make them look fresh and new, I noticed the casting quality on one was pretty crap, it had a lot of voids in it. I also have a main transmission casing that is so full of pinholes, it's pretty scary to think someone hung his life off that thing. I was absolutely gobsmacked when I paint stripped that perfectly looking transmission casing, and discovered under the paint was a pretty shoddy quality casting. Now there were some people that said RHCI did not necessary use the best foundry for their castings, and that they in fact were using a foundry whose primary function was to make ornamental lawn chair castings. Judging by the quality I have seem in the one transmission casing and the pitch horn, I had my doubts to use it. This made me decide to go for another set of pitch horns.

I'm sure you could machine a two piece version for a tenth of the cost. And engineer it for a hundred lifetimes. :)

Cheers Cam.

You are correct Cam, but I live in Australia. A company with a 5-axis machining centre will charge me an arm and a leg to churn out the part. a simple tail transmission driveshaft cost me $800 to machine down, and that was with me supplying the material!! Going with Joe's will save me a lot of effort.

Cheers,

Francois
 

bryancobb

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Cartersville, GA
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Owned Brantly B-2b/Fly Kitfox III/Mini-500b
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Concern

Concern

...The original horns were simply a bent steel plate. They may have been sufficient, but they may also have flexed....

...The 2-piece horn design is just fine, but look closely at what Joe Rinke added to them. He has introduced the drag link attachment...

...I got my set of 2-piece horns from a badly crashed helo. One horn was actually snapped off, the other was fine. I then got a second horn from Barney...

...I also have a main transmission casing that is so full of pinholes, it's pretty scary to think someone hung his life off that thing. I was absolutely gobsmacked when I paint stripped that perfectly looking transmission casing, and discovered under the paint was a pretty shoddy quality casting...

Francois,
I am listening and paying attention to your opinions and findings. I have nowhere near enough experience with Mini-500's to stop learning. I have a few thoughts/questions, based on things you said above.

* All of my hours in a Mini was with the stamped steel pitch arms and I felt they were more than adequate. The cast aluminum ones were one of Fetters' early changes he made because he thought vibration was causing frame cracking and he thought the stamped steel ones were keeping owners from getting their rotors real smooth. After the real reason fro frame cracks was found (flexing) and stopped, we all understood that the stamped steel arms were OK.

* The 2-piece pitch arms from Fetters have the drag link connection point at the trailing edge.

* Are you sure the pitch horn you got from Barney was a genuine Revolution part? I bead blasted my pair off my Texas parts helicopter (factory Bravo) and they looked like very nice castings.

* The biggest concern you caused me to have is on the MRGB castings. I have never seen one naked! The inside surfaces of mine are without paint and I have not seen any pinholes. The Texas one had oil in it and didn't appear to have been leaking. My biggest scare, if pinholes are present, is that a couple of the mounting lugs break off in flight. Do you think having the cases x-rayed for pinholes would be a necessary path to take. I have a close friendship with a Level III NDT Technician and getting him to x-ray the castings may be smart?
 

HobbyCAD

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Hi Bryan,

I hear your comments, and when I sit down and weigh up the pro's and con's, I always come up with a "she'll be right mate". If I had nothing else, I would use the stamped steel horns.

I know the stock cast horns have a provisioning for a drag link, the way Joe incorporated his looks a lot beefier to me.

As I explained, my main "fear" is this one horn section I have parting on me in flight. The one from Barney is original, and it is not as bad as the one transmission I have. The transmission has a universal distribution of neat bubble holes all over the casting, the horn only has one or 2, but to me, they are like stress risers. I just want to make it 100% clear, the one I got from Barney was 100% brand new and unused, and I do not think he ever went in that close to it, to see the small void in it. He bears no blame in my decision.

I've attached some pictures. Just like you, I have visions of the lug coming off in flight, or the top bearing pulling off the top. Every casting from RHCI that has ever passed through my doors has been paint stripped and checked, it's only the one upper casting that looks like a dogs breakfast. Seems on the surfact, it looks fine, but the moment you machine into the insides, you see the voids. This says a lot of the RHCI QA process.

Now you guys know why I put Barney through all the trouble of driving a 1000 miles to go and collect me a pile of parts. That transmission has become my serviceable unit.

Cheers,

Francois
 

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Jincamty

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Te Kauwhata, New Zealand
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Ahh Francois, you have it all wrong... the bubbles are to keep the weight down ;-)

Just like my castings.

Cheers Cam
 

MH1FLYER

We Fix Legends!
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Mt Vernon AR.
Hi Bryan,

I hear your comments, and when I sit down and weigh up the pro's and con's, I always come up with a "she'll be right mate". If I had nothing else, I would use the stamped steel horns.

I know the stock cast horns have a provisioning for a drag link, the way Joe incorporated his looks a lot beefier to me.

As I explained, my main "fear" is this one horn section I have parting on me in flight.

I had the steel stamped arms on my helicopter. Just moving it from the shop on the rough ground to the heli pad would cause them to flex a little bit and that resulted in out of track blades. That got old very fast so we made the back plates and the pitch arms I am using now. They work really well, but Joe’s one piece arms and back plates are even more beefy and are much better than what I have. I have seen many of the cast arms and the quality was not good enough for me, the steel stamped arm would never hold to the kind of flying I would be doing here in the hills. The new arms Joe is making will also be a true match up with the new blades we are fixing to produce with lead lag dampeners. This solve a lot, if not all the past problems.
 

HobbyCAD

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Radiator Plumbing

Radiator Plumbing

Starting fiddling with my radiator plumbing tonight.

Cheers,

F.
 

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HobbyCAD

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Skeeter Jr is progressing along. It's starting to look more and more like a helicopter.

Cheers, F.
 

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Jincamty

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Te Kauwhata, New Zealand
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Home made helicopter
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Looking good Francois.

Have you had it running?
How are you coping with the regulations over there?

Cheers Cam.
 

HobbyCAD

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Thanks Don.

Thanks Cam. As far as the building inspection, I've been keeping a good log, and I have had an inspector in to see that I'm really doing it all. So the heli will be legal, but it's the testing that is going to require careful treading. It seems there is a regulatory grey zone between ground running or hover testing, and actual flying. I don't want to make too many statements in an open forum, but regulatory powers have given me some guidance. I think I will be able to get up to the stage of track and balance in the hover, before I am going to attract the attention you got. In the meantime I'm hoping to see progress with a recreational type of heli license appear. At this stage, having to fork out $50K to get a full PPL-H on a Robbie just to hover mine around the paddock is ridiculous.

Cheers,

F.
 

birdy

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Alice Springs-central Oz.
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open frame single seat & a 'wasa' RAF, among other types.
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Regulaters in this country are the best in the world,............at maken normaly law abiden, placid, productive people say F### you and your illogical crap.
 

bryancobb

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Good Job Francois!

May I ask what your final configuration of the TR drive-shaft is? What drive flanges? How many flex-couplings? Bearings or Teflon bushings? How are bearings or bushings locked to shaft tube? To bulkheads?
 

HobbyCAD

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Modified Dual Bellcrank TR Pitch Slider

Modified Dual Bellcrank TR Pitch Slider

Here my version of implementing a dual bellcrank pitch slider.

Cheers,

F.
 

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HobbyCAD

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Some further continuation of the TR slider upgrade.

Those pesky ball bearings fretting grooves into the TR shaft. Instead of the little phosphorous bronze inserts into the same ball bearing location, I've decided to re-engineer the spider and slider with a groove machined into them, into which a slider bush is fitted during re-assembly.

Here some pics of the parts, I still have to machine down the precision sliding bush.

Cheers,

F.
 

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All_In

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Not sure over 10,000+ logged FW, 260+ ultralights, sailplane, hang-gliders
Looking good Francois!!!
 

HobbyCAD

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After a long hibernation, the Skeeter Jr project has been dusted off, and is in progress again.

Swopped out the original drive sprocket for a special order larger one I bought of John, this will bring the engine RPM more in-line with the torque curve. Engine now finally installed. First task is to plumb up the fuel, oil and cooling to the engine. Next is to figure out a tacho pick-up independent from the one on the FX Nytro engine.

The job that is staring me in the face is the MRG internal alignment, both mesh and pre-load. I am envisaging disassembling, inserting shims, assembling, torqueing it all up, measuring, recalculating, disassembling, adjust shims accordingly, assembling, torqueing it all up again, re-measuring...., umpteen times till it hits the sweet spot.

Some progress pics will be posted this weekend.

Cheers, F.
 
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