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Marty_d

Rudder & elevator cables

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Hi all,

 

I'm about to install rudder & elevator cables.

 

Firstly, turnbuckles.  Is it acceptable to use marine-style stainless steel turnbuckles?  Looking at various pictures of 701 builds, they look like brass fittings (obviously supplied in the hardware kits).

 

Secondly - cable shackles (see pic below)

Main Image

 

These handy little things seem ideal for the control surfaces and elevator bellcrank (so 6 required).  Trouble is they seem to cost an arm and a leg.  Aircraft Spruce in US sell them for $10.85 each,  I logged on to an Australian supplier (AAE) who have them as something like $38 each.

So it looks like an Aircraft Spruce order (when the dollar gets higher perhaps...) unless anyone knows of a supplier here or has some spares they'd like to sell??

 

Thirdly - safety wire.  Is this a special grade or will any 0.032" S/S wire do the trick?  

 

Thanks!

 

Cheers, Marty

 

 

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The brass look is cadmium plating - on steel.

Aviation parts are suitable for aviation uses without question or concern. Marine parts - who knows. Having said that, one would imagine that there are some huge loads and forces on yacht rigging cables made from those marine grade items. Unless you can test load cable assemblies you make to some known figure and be satisfied, you're a test pilot.

The dollar is not going to fluctuate enough any time soon to wait, if you need them, order them, and more things in the one box.

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Marty,

Do not use stainless steel for cables, rod ends or turnbuckles. Experience in the GA field has shown that stainless steel has a higher rate of failure than steel as the metal is more brittle than plain steel.

 

The integrity of these parts is what your life is relying on. So forget about your fancy glass instrument panel, or any other cosmetic touches you intend for your aircraft. Spend the money on high quality, made to a standard, certified and traceable components. Yes they are expensive, but it costs the manufacturer money to ensure that the product meets specification, and to maintain the traceability records. 

 

When you buy from Aircraft Spruce and Specialty, make the effort to order by phone. (Ring before 10:00 am our time to get then before they knock off). When you order, specify that you will not accept paying for postage of a massive box. For the turnbuckles and shackles needed for you build, they should be able to put them in a small mailing box which will cost about $US35 to send and arrive in about 10 days.

 

The safety wire can be any stainless steel stuff. The part number for 32 thou stainless steel safety wire, not temperature rated, is MS20995C32

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Posted (edited)

Marty - Stainless steel is not as strong as you tend to think it is. It is made for corrosion resistance, not extreme strength. 

High grade steels are heat-treated low-alloy steels. But these steels need a protective coating of some type, because they're prone to corrosion, as all high grade, high strength steels, are.

Lifting equipment, and aviation components, are strength tested, and load rated accordingly, with load ratings that are only a small percentage of their tensile strength.

Those cable shackles from Aircraft Spruce are a bargain at US$10.85 each. Most aviation suppliers are asking a lot more for them. Bite the bullet, this is your life you're playing with.

On a boat, a coupling snaps, you might end up with a flapping sail, or a mast with a lean. On an aircraft, a coupling snaps, and it's all over, red rover.

Edited by onetrack

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Remember you pay over $100 / hr to have some apprentice change the oil on the wife's car.. Nev

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Stainless steel is used for aviation, but not in the 1/19 format.

The finer strands used are capable of bending safely and if you get one broken strand that tells you it is time to discard the whole length.

I replaced my SS control cables last year, due to the CASA requirement to ditch the terminal ends at the turnbuckles. Cables were perfect after 15 years of use. CASA then changed their mind and allow inspection, rather than replacement.

I don't think there is any requirement to use SS for lockwire, Gal is acceptable.

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Posted (edited)

I'd use the right lockwire . Something else might not '"work" as well . You can get several thicknesses. Neat turns/twists are a must.  The elevators are the most important control. It's a good idea to back it up with a separate trim system or duplicate it. Running along the fuselage would perhaps work but hard to arrange. Nev

Edited by facthunter

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I wouldn't use turnbuckles. There is not a lot of stress on the elevator or rudder cables so stretching is not a big issue especially if you use quality cable. I'd either make them to the exact length (I did this with no slop yet) or use thimbles, U bolts and a joiner plate with multiple holes for length adjustment.

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2 hours ago, kgwilson said:

I wouldn't use turnbuckles. There is not a lot of stress on the elevator or rudder cables so stretching is not a big issue especially if you use quality cable. I'd either make them to the exact length (I did this with no slop yet) or use thimbles, U bolts and a joiner plate with multiple holes for length adjustment.

How do you adjust tension without turnbuckles?

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I have aircraft control cables from FNQ cables on my CH701. Might just be my aircraft engineering background but I prefer them over anything else I could have made up.

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It's worth your life to get control cables made up by people qualified to do so. FNQ Cables might be one, but I know that AirAg at Bankstown is. and Aviall in Melbourne had a cable shop. Both will give you a Release Note for each cable which further ensures that they are suitable for purpose. 

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FNQ are Ian Colville  who bought Ian Aviation at Archerfield and has since moved his operation to an airstrip on Atkinson Dam Road. I believe. I would always use the local small business where possible.

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Aircraft propellers and spares at Moorabbin for aviation cables.

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40 minutes ago, Old Koreelah said:

How do you adjust tension without turnbuckles?

As Mark said, 2 plates (strips) with a series of holes, the pitch of the holes on one plate slightly less or greater than the pitch on the other, so you get a sort of Vernier effect of matching holes, through which you bolt.

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2 hours ago, Old Koreelah said:

How do you adjust tension without turnbuckles?

It is possible to get a small amount of variation in length by twisting or untwisting the cable. This is how you get a Thruster to fly hands of in roll by twisting the leading and trailing edge lift cables to produce a small change in angle of incidence.  

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13 hours ago, 440032 said:

The brass look is cadmium plating - on steel.

Aviation parts are suitable for aviation uses without question or concern. Marine parts - who knows. Having said that, one would imagine that there are some huge loads and forces on yacht rigging cables made from those marine grade items. Unless you can test load cable assemblies you make to some known figure and be satisfied, you're a test pilot.

The dollar is not going to fluctuate enough any time soon to wait, if you need them, order them, and more things in the one box.

 

10 hours ago, onetrack said:

Marty - Stainless steel is not as strong as you tend to think it is. It is made for corrosion resistance, not extreme strength. 

High grade steels are heat-treated low-alloy steels. But these steels need a protective coating of some type, because they're prone to corrosion, as all high grade, high strength steels, are.

Lifting equipment, and aviation components, are strength tested, and load rated accordingly, with load ratings that are only a small percentage of their tensile strength.

Those cable shackles from Aircraft Spruce are a bargain at US$10.85 each. Most aviation suppliers are asking a lot more for them. Bite the bullet, this is your life you're playing with.

On a boat, a coupling snaps, you might end up with a flapping sail, or a mast with a lean. On an aircraft, a coupling snaps, and it's all over, red rover.

 

Thanks guys, this is why I asked the question.  A friend in Canberra who's mostly built a 750 has used S/S turnbuckles and fitted cable ends - I will forward the warning to him too.

 

I'm not trying to save a buck at increased risk - if that's the price of those shackles then that's the price - but given the size of them (ie postage per each would not be a lot when buying 100's from the US)

I think it's a bit rich to be charging close to $40 each for them over here.  I need to do an order for the engine mount bolts & rubbers etc from Aircraft Spruce anyway so will do it sooner rather than later.

 

8 hours ago, kgwilson said:

I wouldn't use turnbuckles. There is not a lot of stress on the elevator or rudder cables so stretching is not a big issue especially if you use quality cable. I'd either make them to the exact length (I did this with no slop yet) or use thimbles, U bolts and a joiner plate with multiple holes for length adjustment.

 

That's a valid alternative in the 701 plans - 2 lengths of 0.040" with AN3 bolt spaced to suit.  I thought it looked a bit amateur but given the complications around turnbuckles and lock wire etc it's starting to look like an attractive method.

 

Another acceptable method is 2 short sections of L extrusion back to back with a single bolt through the upright bit.  Didn't like that one.

 

8 hours ago, facthunter said:

I'd use the right lockwire . Something else might not '"work" as well . You can get several thicknesses. Neat turns/twists are a must.  The elevators are the most important control. It's a good idea to back it up with a separate trim system or duplicate it. Running along the fuselage would perhaps work but hard to arrange. Nev

 

It has electric trim so I guess that's a separate system.

 

5 hours ago, old man emu said:

It's worth your life to get control cables made up by people qualified to do so. FNQ Cables might be one, but I know that AirAg at Bankstown is. and Aviall in Melbourne had a cable shop. Both will give you a Release Note for each cable which further ensures that they are suitable for purpose. 

 

Aviall won't even show you prices unless you're a member, and they won't accept you as a member if you're not part of a registered business.

 

When I bought my Rotax the seller told me he makes his own cables, but also does a short section with eyes/swages each end and sends them over to be tested.  The company tests them to destruction and sends him a report which shows the strain before breaking (in effect a release).  If the swaging is done properly the elevator would fail at some other point before the cable itself failed.

 

I'll have a talk to AirAg and/or Aircraft Propellers and Spares.  

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Here are the savannah ones. The adj plate is at the rudder pedals and the 2 flat plates attach at the rudder. They just have thimbles on the end of the cables crimped. These are the originals off Mabel

 

 

IMG_7485.thumb.jpg.4368d8fb7b9d3250f38c14750679d6f8.jpgIMG_7487.thumb.jpg.eb23f6423cde02c49c1acb43a96895f1.jpgIMG_7486.thumb.jpg.f513b102ca63f2c8a28e8a9800684464.jpg

 

 

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A couple of very useful document are available as a free download from the FAA website.

AC43 is the generic title.   Specifically:  AC43. 13-1B  &  AC43. 13-2B

They describe acceptable practices for various maintenance and repair tasks.

 

I have used them for more than 30 years as a reference document when training others in the care and feeding of gliders.

 

 

Robert

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17 hours ago, Kyle Communications said:

Here are the savannah ones. The adj plate is at the rudder pedals and the 2 flat plates attach at the rudder. They just have thimbles on the end of the cables crimped. These are the originals off Mabel

 

 

IMG_7485.thumb.jpg.4368d8fb7b9d3250f38c14750679d6f8.jpgIMG_7487.thumb.jpg.eb23f6423cde02c49c1acb43a96895f1.jpgIMG_7486.thumb.jpg.f513b102ca63f2c8a28e8a9800684464.jpg

 

 

Crikey, it’s a meccano Plane!

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It's O.K., Derek - Mark already knows what the finished product is supposed to look like - it's on the box! Even better, the instructions are bi-lingual - and all the tools are included! :cheezy grin:

 

I just hope he understands that those plates he pictured, are part of the fuselage and firewall. :scratching head:

 

I personally believe, he'd be a lot better served by swapping those trapezoidal wheels for round ones, but I guess that's a matter of personal choice.

 

 

 

Meccano plane.jpg

 

 

Edited by onetrack
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19 minutes ago, onetrack said:

It's O.K., Derek - Mark already knows what the finished product is supposed to look like - it's on the box! Even better, the instructions are bi-lingual - and all the tools are included! :cheezy grin:

 

I just hope he understands that those plates he pictured, are part of the fuselage and firewall. :scratching head:

 

I personally believe, he'd be a lot better served by swapping those trapezoidal wheels for round ones, but I guess that's a matter of personal choice.

 

 

 

Meccano plane.jpg

 

 

Haha, love it!

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Very funny Onetrack....mind you truth and humour are pretty much the same when it comes to the italio english build manual...this is my second one and I am still scratching my head and swearing regularly about the quality of the build manual. I have never seen that meccano aircraft before..thats pretty cool..would look great on my desk at work 🙂

 

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Mark, you can get the Meccano aircraft off Amazon.com.au for $19.00 (delivered free if you spend $39.00). Best of all, it doesn't require batteries! :cheezy grin:

Edited by onetrack
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