Control surfaces actuators design/preferences

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geosnooker2000

Well-Known Member
When you say 6061 you also have to specify which temper condition. In condition -0 the material is too soft to use as control tubes, but can easily be bent for piping. -T6 is what you should get for structural applications.
Duly noted, but in my post I copied and pasted for accuracy. "Aluminum Pipe 6061 Extruded T6 Schedule 40"
So it is T6, but nobody else I looked at added the word "Extruded" to the description. Wonder what that's about.

geosnooker2000

Well-Known Member
When they say "schedule" (usually 40 or 80) it's considered pipe, not tubing, and intended primarily for liquid flow, not structural. Not that it can't necessarily be used for structural purposes, but the dimensions are usually inconvenient, and it's usually too heavy for aircraft work.
Yes, I am aware of schedule 40 and 80 meanings from my architectural work, but like you alluded to; if it will work, and it costs half as much, why not? Looks like it would add about 5lbs. to the plane through the wing. If it saves $300, I think it's a good tradeoff. dog Well-Known Member Duly noted, but in my post I copied and pasted for accuracy. "Aluminum Pipe 6061 Extruded T6 Schedule 40" So it is T6, but nobody else I looked at added the word "Extruded" to the description. Wonder what that's about. Extruding might be the only process now used to make aluminum pipe. Did a little search and only came up with casting for pipe fittings,and extrusion and drawing for pipe. Dan Thomas Well-Known Member Looks like it would add about 5lbs. to the plane through the wing. If it saves$300, I think it's a good tradeoff.
If you carry that philosophy throughout the design and build process, you will have a disappointingly heavy airplane. An airplane that was affordable, maybe, but has no usefulness. There have been way too many homebuilders learn that the hard way.

TFF

Well-Known Member
5 lb here and there is almost a gallon of gas. At least a half an hour in the air. It is someone’s backpack in the baggage. $300 on something that will in the end cost$40,000 will be a short term gain in the pocket, with a lifetime of wishing you had an extra hour in the air.

geosnooker2000

Well-Known Member
I will not carry that philosophy throughout the plane. On the other hand, $300 here,$200 there, pretty soon you're running into real money. It's a balancing act.

gtae07

Well-Known Member
Yes, I am aware of schedule 40 and 80 meanings from my architectural work, but like you alluded to; if it will work, and it costs half as much, why not? Looks like it would add about 5lbs. to the plane through the wing. If it saves \$300, I think it's a good tradeoff.
Why are you still chasing the Schedule 40 stuff? Did you not see where I posted that Spruce has 6061-T6 tubing in aircraft-appropriate sizes at reasonable prices?

Heliano

Well-Known Member
Map is right. 6061-0 should not be used in anything structural. Rivet and bolt holes tend to enlarge due to loads, its elastic range is short. At the other end we have 7075, an aluminum alloy with very high tensile strength, but, depending on the geometry and the loads, is prone to fatigue cracks. It is way more expensive too. 6061-T6 or 2024-T351 is the choice in the vast majority of cases

geosnooker2000

Well-Known Member
Map is right. 6061-0 should not be used in anything structural. Rivet and bolt holes tend to enlarge due to loads, its elastic range is short. At the other end we have 7075, an aluminum alloy with very high tensile strength, but, depending on the geometry and the loads, is prone to fatigue cracks. It is way more expensive too. 6061-T6 or 2024-T351 is the choice in the vast majority of cases
It's T6.

Well-Known Member
The only difference I would see using 6061-T6 verses 2024-T351, would be that 6061-T6 would have a lower fatigue life by maybe a 1/3 (shouldn't be an issue, just something to be aware of).

rtfm

Well-Known Member
On a completely different tack, but still on the subject as proposed by the OP, what about electrical (servo motors)? I have a situation of a wing which folds on a hinge in the middle, but I want ailerons on the outer panel. Mechanical linkages (be they cables or tubes) are problematic. The two solutions which present themselves are hydraulic and electrical. Hydraulic is beset by leaks (so I'm told), I know nothing about them, and weight. Dual servo motors (i.e. one on each end of the aileron for redundancy) would seem a simple, inexpensive and reliable solution.

Thoughts?

Duncan

Well-Known Member
I have a situation of a wing which folds on a hinge in the middle, but I want ailerons on the outer panel. Mechanical linkages (be they cables or tubes) are problematic. The two solutions which present themselves are hydraulic and electrical.
Have a look at the automatic connecting controls they use on gliders, can be as simple as basically two bell cranks that touch when the wings unfolded.

gtae07

Well-Known Member
Look at the old WWII-era Navy birds for some ideas. A bellcrank at the hingepoint could work.

Vigilant1

Well-Known Member
Dual servo motors (i.e. one on each end of the aileron for redundancy) would seem a simple, inexpensive and reliable solution.

Thoughts?
In my opinion, it would be very difficult to make a DIY fly-by-wire primary flight control system sufficiently reliable. The results of a failure (a possibly uncontrollable aircraft) are much more significant than, say, loss of engine power. It needs to be bulletproof. Dual actuators would be a start, but you also need independent switches for them. Then you need independent power sources (truly independent, so a voltage spike on one system won't fry anything on the other system). Also, we'd need to protect against one set of actuators making the backup actuator ineffective (say, if we had a failure in the gear train of the primary servo that resulted in a jam). In the case of ailerons, we'd need a way to keep the left wing and right wing coordinated at the desired ratio (something accomplished easily with mechanical control runs). That means position sensors and a digital or analog circuit, and more failure points. Also, we don't really have operationally redundant systems unless we have a way to know that one part has failed and now we are operating on one system only (that could be via a functional check of each system before flight, or something more sophisticated). And, with all that, maintaining everything will be a lot more trouble than a simple mechanical system. There are elegant ways to accomplish wing folding with mechanical flight controls. The Onex and some other planes used paired bellcrank push pads that seem to work well.

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mcrae0104

Well-Known Member
HBA Supporter
Log Member
Like V1, I’d look closely at the Onex and SPA Panther for paddle design.

Hot Wings

Grumpy Cynic
HBA Supporter
Log Member
Mechanical linkages (be they cables or tubes) are problematic. The two solutions which present themselves are hydraulic and electrical.
Don't overlook Teleflex style cables. They DO have some disadvantages, but are simple to design and bend nicely where needed.

gtae07

Well-Known Member
In my opinion, it would be very difficult to make a DIY fly-by-wire primary flight control system sufficiently reliable. The results of a failure (a possibly uncontrollable aircraft) are much more significant than, say, loss of engine power. It needs to be bulletproof. Dual actuators would be a start, but you also need independent switches for them. Then you need independent power sources (truly independent, so a voltage spike on one system won't fry anything on the other system). Also, we'd need to protect against one set of actuators making the backup actuator ineffective (say, if we had a failure in the gear train of the primary servo that resulted in a jam). In the case of ailerons, we'd need a way to keep the left wing and right wing coordinated at the desired ratio (something accomplished easily with mechanical control runs). That means position sensors and a digital or analog circuit, and more failure points. Also, we don't really have operationally redundant systems unless we have a way to know that one part has failed and now we are operating on one system only (that could be via a functional check of each system before flight, or something more sophisticated). And, with all that, maintaining everything will be a lot more trouble than a simple mechanical system. There are elegant ways to accomplish wing folding with mechanical flight controls. The Onex and some other planes used paired bellcrank push pads that seem to work well.
As someone who has worked in testing and service support of FBW systems, this is a really good high-level summary. The only fly-by-wire I'll put in my homebuilt is electric trim, and autopilot.

mcrae0104

Well-Known Member
HBA Supporter
Log Member
I flew a plane with electric trim for the first time recently, but the increments available didn’t quite suit my liking—I’m used to making micro-adjustments with the wheel. Are there trim systems that could offer very fine control, which I presume would be a prerequisite for a home brewed FBW aileron system?

Lendo

Well-Known Member
Hs anyone considered Titanium Pressure tubing, it's very light and may be strong enough for Push-pull Tubing. As I just don't know I'm just throwing it up for consideration.
George

BJC

Well-Known Member
HBA Supporter
Are there trim systems that could offer very fine control,
Some Glasair builders have installed two speed pitch trim.

BJC