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Old 7th Apr 2002, 19:54
  #61 (permalink)  
 
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The fact that the instructor was able to call his office afterwards is a positive sign. Any further ifnromation on the condition of the student? Hope to god the news is good.
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Old 8th Apr 2002, 18:34
  #62 (permalink)  

Senis Semper Fidelis
 
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Why can't these sort of Helis use Renolds type chains, after all if they are used in GM automatic boxes to propel big metal along the ground, there should be no problem with driving a tail rotor, that goes for Robbies, Enstroms and any other rubber powered craft as well, Nick or any other techie wizard out there your the experts on the tech stuff like this , will you let us know!
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Old 8th Apr 2002, 19:12
  #63 (permalink)  
 
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The RotorWay uses a system of three double belts to run power down the cone, taking it from a vertical shaft and using three intervening pulleys canted at about 30 degrees each to obviate the need for a tail rotor gearbox. Simple, light, cheap, easy to maintain, and about as foolproof as any other system.
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Old 8th Apr 2002, 19:22
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An idea.

Vfrpilotpb


The weak tail-rotors could be replaced by a second strong main-rotor [intermeshing configuration]
Sorry, just had to get that in.
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Old 9th Apr 2002, 14:20
  #65 (permalink)  
 
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Arrow RUBBER!

There are lots of subtle reasons for using belts as the primary means of transmission in light helicopters Ė hereís a few.

If you consider the R22 installation, the nature of the rigidity in-plane of the blades means that teeter-rotors convert the Coriolis forces due to flapping into a RRPM response that can create lareg loads in the transmission, though its small in piloting terms. This response is absorbed by the rotor, transmission and engine inertia and other resistive forces in the system.

With a stiff transmission such as a chain or gears, these loads would create large fatigue loads in all of the major drive-train components.

Furthermore, the non-continuous power delivery of the 4-cyclinder engine at relatively low speed would feed large oscillating loads back up the drive train to the rotor - again fatigue problems.

Incorporating a 'soft/flexible' member in the transmission will help reduce the transient shock loads fed both ways by the visco-elastic deformation of the belts. To the benefit of transmission and engine and rotor life.

Big turbine helicopters use turbine engines that have continuous combustion and hence smooth power delivery, though flexible members are sometimes still incorporated to reduce shock loads in the system - not belts though!

Further advantages of belts over chains are as follows:

The load bearing elements in belts are physically bigger than chains for the same torque and hence cracks/splits will be physically bigger and easier to spot before they are failure-critical. Belts have a relatively benign failure mode in comparison to a sudden catastrophic failure that would occur with a chain.

Belts don't need lubricating or oil changes and they are out in the open and so easy to inspect.

Belts don't need encasing to allow lubrication - additional weight & maintenance.

With the belt system you get an lightweight, reliable clutch mechanism almost for free! (in weight terms)

Belts are physically robust - tolerant to dust ingestion & the presence of various contaminants.

LIGHT LIGHT LIGHT!!!

Very easy to design-in redundancy with little addition of weight. Multiple belts on a single pully. Though locating the two belts right next to each other and in the open is perhaps not quite so prudent!

Hope this helps

Cran


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Old 9th Apr 2002, 19:32
  #66 (permalink)  
 
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nucleus33

A temporary hijacking of your thread, for the fun of a little technical banter;

Hi CRAN

There can be no argument about the oscillating loads from a reciprocating engine, particularly a four stroke one, with few cylinders. As well, your comments about the many advantages of belts make sense. The following might deserve a little more clarification, though.

"If you consider the R22 installation, the nature of the rigidity in-plane of the blades means that teeter-rotors convert the Coriolis forces due to flapping into a RRPM response that can create large loads in the transmission, though its small in piloting terms. This response is absorbed by the rotor, transmission and engine inertia and other resistive forces in the system.".

Subject to correction by higher authorities, I believe that most tail rotors incorporate delta-3. If the delta-3 is by 'flap hinge geometry' ( see sketch ) it will have a lead-lag component and this should reduce torsional oscillations in the drive train.


Dave J

Last edited by helidrvr; 10th Apr 2002 at 00:43.
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Old 9th Apr 2002, 19:39
  #67 (permalink)  
 
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Belts give you something to whip your Co-pilot with after the mishap (only if it was his/her fault)
(more suited to a JB post, but I couldn't resist)
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Old 9th Apr 2002, 21:18
  #68 (permalink)  
 
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Torsional Oscillations due to flap

I agree that delta-three by flap hinge geometry will reduce (but not remove) torsional response.

However my earlier remarks were regarding the main rotor. The torsional response of the TR on most helicopters would be insignificant compared to the MR. Though it should not be ignored.

I'm sorry if that was ambiguous.

The main rotor will exhibit a RPM Response to flapping which will induce appriciable torsional loads. It is to this that I refer. Determining the exact magnitude of this oscillating torque is complicated and will be significantly effected by the size and rate of cyclic control and coning angle amongst other things. The belts help remove transient peaks from these loads by flexing and sliping.

Cheers
Cran
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Old 9th Apr 2002, 21:40
  #69 (permalink)  
 
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Hi CRAN

Agreed.

The Kaman helicopters make for an interesting study of these activities. Each rotor has a teetering hub and delta-3. These two separate rotors are physically linked together and now they act similar to a four-bladed rotor. ( Picture ++ )

Best to uses Really Rigid Rotors.
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Old 9th Apr 2002, 23:40
  #70 (permalink)  
 
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Belts & Chains.

I seem to recall Rotorway use a triplex chain for the primary drive and that there is a history of drive shaft failure, possibly associated with this.They allegedly leak oil from the chain casing in large quantities. I have also read of alignment problems.
I suppose it depends on how well the kit is put together.

Seems chains may not be such a good idea.

There is an aftermarket 'upgrade' to belt primary reduction.
(Dog tooth belt I think).
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Old 19th Jun 2002, 22:53
  #71 (permalink)  
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RotorWay Exec 162

Was reading the thread "A Chopper is born" and it talks about the 162.

Now I like most people have seen the website, looked at the price and thought what you were getting all seemed OK for what you pay for a fun little machine.

Has anyone out there ever owned/flown/maintained or built one.

Any general info re "is it too good to be true" etc.
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Old 20th Jun 2002, 00:28
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I was sent out to evaluate the Exec back in the 80s, and I was quite impressed. The CAA took the view that if it survived in the litigious atmosphere in the States, then they would look favourably on it, and I must say I agreed with them. Sadly, the project fizzled out, but I would buy one with my own money, which is probably more than I can say for a Robbie (OK, my tin hat is on!).

heard a couple of things about the engine which I heard they fixed.

phil
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Old 20th Jun 2002, 10:54
  #73 (permalink)  
 
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bcp,

This is my view...

The thing about helicopters is that there are lots of hidden phenomena at work that are not immediately obvious to a none-technical person.

There is a big difference between building a plane and building a helicopter. Just because you can do one doesn't mean you can do the other.

Lets take the example of fatigue, the huge oscillating loads that the helicopter is subjected to in its everyday operation place enormous demands of the structural integrity of the airframe. By virtue of the complicated mechanical arrangements required in helicopters load paths in the structure are often concentrated such as the steel tube frame of the 162F. Let's say you inadvertently scratch/score one of the member steel tubes of the frame - this scratch could develop into a crack and cause a structural failure 200, 500, 1000hrs later. Of course you would hope that you would spot such a flaw or notice you had scratched the frame before every flying and seek advise from the factory who would of course be in a position to give you the correct technical advise. In a concentrated load path such as a steel tube the size of a critcal crack would be very small indeed and very hard to see in many cases. So what if it goes un-noticed...........

In essence the people the fabricate and assemble certificated light helicopters, Robinson, Schweizer, Enstrom are companies with many technical experts with a great deal of experience in the field. The hands-on guys that work on the factory floor are extremely well trained and do a very limited scope task many, many times. Hence, the quality of there work is predictable and very high indeed. They have been trained in all of the supporting technical knowledge pertinent to there job and can spot things that may develop into problems during the aircraft's life.

None of this experience is available to a first time kit builder. It is 'assumed' that joe-public can learn how to assemble a helicopter for a limited manual 'monkey-see-monkey-do' and assemble it without serious error or oversight correctly first time. What happened to learning by your mistakes?


Let me just add - Of course you have the telephone help line and PFA rep, but in the case of the help line - how do you know what to ask about? The PFA Rep can't inspect everything.....hidden behind an inaccessible panels etc?

The earlier comment...So you think you can build a helicopter, would you trust your life on it? Is so so very true.

What we have to ask is....what about the guys that don't know any better....where's the safey net.

So thatís my 2p on kit building helicopters by amateurs. Now for a few words on 'unproven' light helicopters.

Lets have a think about the development of the (Proven) R22 over the past thirty'ish years. The R22 has become an extremely well used and proven machine. Used in many high demanding roles. Even today with all of the experience and expertise available at Robinson they are still modifying the design to improve it's reliability. The sheet metal work around the engine (just an example I know of) still cracks and has to drilled. In earlier versions frames and bits of structure cracked and had to be modified (this is normal for a new design and is not particular to Robinson) Thatís after however-many-million flight hours and 3000 in service. By virtue of the small numbers [600] of Exec's in service and the low time on the fleet the design simply hasn't got that level of evolutionary-pedigree to be in the same league in terms of reliability and integrity. The problem is that the feedback loop to the manufacturer with regards design problems doesn't exist in the same way that it did/does at Robinson, the ships don't go back after 2000/2200 hour for a strip down and rebuild were the engineers in the 'know' can crawl all over the machine with all sorts of clever gadgets to find the little monsters hiding in the design. Therefore, it is reasonable to assume that it may take many more accidents and failures before design fixes filter through than were required for the rapid development of the R22.

I'm aware that i'm ranting a bit.....

so i won't mention: Construction quality variability or the effects of shifting the cause of failure from design flaw to a construction flaw in the eyes of the legal people. Maybe flying lawyer has some thoughts.

Hope this helps
CRAN
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Old 20th Jun 2002, 20:01
  #74 (permalink)  
 
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............ and in addition to CRAN's remarks. :) :) :)

My knowledge about helicopters is very limited, but one thing became very obvious, very quickly. There are two extremes in the rotorcraft industry.

One lunch-hour, while auditing a helicopter maintenance course, I was taking some dimensions and had placed a single sheet of paper on top of an engine. An engine, with display cutouts, that would never fly again. An instructor happened to be passing by and he reamed my ass out for what seemed like an hour, for laying something on an engine.

At the other extreme, there have been gyrocopter get-togethers at someone's farm. The farm owners keep their gyros in a shed, along with the antiquated tractor and plow. The most popular metal in these sheds was iron oxide.

Professional pilots are very fortunate to be backed up by other professionals on the ground.
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Old 21st Jun 2002, 06:01
  #75 (permalink)  
 
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Wink Exec 162F

I have to agree with the posts so far. I spent a couple of years researching what to get, cos I had the time and not enough money
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Old 21st Jun 2002, 06:14
  #76 (permalink)  
 
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carrying on from my inadvertant post closure!

Sorry about that. Somehow my connection dropped out.


To carry on.

I researched for a couple of years while I rented an R22. I ended up buying a used R22. I have sat in a couple of 162s but not flown in them.
Was due to fly in one but the FADEC rolled over and wouldn't let the machine start. Cancel that one.

The other was in my engineers hangar for months waiting for a new tailcone. It had a huge buckle in it that was said to have occurred from normal usage. Owner claimed no hard landings or damage. Just finished a flight one day and noticed a thin buckle in the skin. Fired it up again and after a few, some ? exactly how many, minutes there was a big buckle.

The engineer had a really good crawl all over it and he isn't very impressed. Mind you he's Robbie man through and through!

I did a lot of comparisons with costs etc as well as all sorts of other things and I reckoned then (and still do after owning my R22 for nearly 3 yeays) that I made the right decision.

see http://helipics.homestead.com.index and go to "To buy or Build"

The only thing I think the Rotorway has in its favour is it is a way better looking machine than the R22. (But don't tell my Robbie I said that
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Old 21st Jun 2002, 06:37
  #77 (permalink)  
 
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corrected URL

Sorry.

Once again I've stuffed up the URL try

http://helipics.homestead.com

and while you're at it have a look at our local flying clubs latest adventure at

http://secretmensbusiness.homestead.com

(they are cross linked so you can find them both by going to either one of them
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Old 16th Jul 2002, 08:50
  #78 (permalink)  
 
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Post How to build a Rotorway TV prog on tonight

For all you UK based ppruners,

A new series entitled "A Chopper Is Born" is starting tonight on Discovery Home and Leisure at 9pm.

It follows Mark Evans building a Rotorway Exec. He's previous two series followed him building a car, and then an aeroplane.

He's also doing a helicopter conversion in Arizona.

Should be interesting to see how difficult these things are to build safely...

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Old 16th Jul 2002, 10:24
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Is it possible one kind PPRuNer could record the series, and ( like with the "People Like Us" video ) send it to the next person in a list so we can all see it ?

Failing that RH, lots of beers and requisite monetary compensation if you could record onto a tape for me !
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Old 16th Jul 2002, 12:31
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Tape? How 90's...I'll see if I can find one of them VHS things in my attic to download the Sky+ digital recordings on to ...

Of course it'll not stop Mrs. Horn overwriting them with fecking Eastenders or Big Brother.

She argues that having already filled 80% of the disk space in the sky+ box with helicopter-related programmes she's entitled to use the other 20% !

Can't see it myself...

Anyway, I'll see what I can do.
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