Build threads look fun

[RknRusty]

I see Duke has a four blade prop. I'd be interested to know any flyability differences.
.76s, eh. I'm about to fly my first plane in this category, a Magnum(maybe not quite as big), and am frankly worried about hanging on to it. Never flew anything bigger than a .35, and I only weigh 125 pounds. Will I need a pole and a safety belt?
Rusty

[Dave_Trible]

Rusty I'm size-challenged myself but don't worry.  It's more about airplane weight and speed than engine size.  Bigger airplanes might wear you out at the field a little faster though. 
The four blade prop is nice.  It just seems to run a little smoother.  Thrust?  Not noticeably different than a three.  One must get out of the way of it one blade faster when starting!

[Dave_Trible]

A peak under the hood of the accelerometer system going in the test airplane.  When I took this shot I was waiting on the LiPos and a voltage regulator to arrive so they aren't in the photo.  Trying a 2 cell 180 mah LiPo and have a 350 if I need more.  One of my .76s spun a bearing so I may do the early testing with a .61 while the engine gets an overhaul.  I'm wondering if this system will actually be more useful with the .61 anyway.  The .76 pulls through the pattern in a flat four cycle at a constant speed up, down or level as much as I can sense and so I'm not sure what I'm regulating.  The .61 however can be 'goosed' under load to maintain a better maneuver shape.  We'll see.

[Tim Wescott]

Sorry to be rules lawyering at this late date (and forgive me if someone's already posted on this).  The FAI sporting code, section 1.3.2, does indeed allow radio shutoff in control-line aircraft:

1.3.2 b) Powertrain control may be accomplished by the pilot via the wires or cables or by an onboard self-contained, automatic process.

But the aerobatics-specific code, section 4.2.2, seems to very emphatically rule it out:

4.2.2 e) The use of a pilot activated power shutdown device to define the point of the beginning of the power-off descent in the landing manoeuvre is not permitted.

This certainly seems to toss a wrench into thoughts of using a radio (or inertial control) to shut down a motor in FAI.

[Dave_Trible]

Hi Tim.  I sure stand to be corrected but I'm under the understanding they already do use the 2.4 in FAI in Europe for shut off.  Lauri Malila and I have had discussions about doing what he already does routinely.  Might be like our own rules;  technically AMA would allow the 2.4 for our use now but 'aerobatics' hasn't specifically opened the door to it- until this new rules cycle proposal.  Would be interesting to know if there is an updated amendment someplace there or could they have now disallowed it?  I can see where the seven minute FAI time limit would make the use of  a shut off much more an issue for IC since electric timers made it a non-issue for electrics yet still some challenge for IC .

[Tim Wescott]

It's new: in the front matter of the code it's mentioned as being implemented for the 2014 sporting code.  It may well have been implemented as a response to the use of the radio gizmos in 2013, but you'd think that Laurie would know of the change if so.

I'm certainly not the one to correct you: one of the facets of being human is that there's the rules as stated and the rules as read, and the rules as enforced.  I read the rule as disallowing radios, or third lines, or down-elevator cutoffs, or using the characteristics of your fuel tank for a cutoff loop, etc.  How that rule will be enforced by FAIens, and whether it'll be enforced differently at "local" contests vs. the WC is well beyond my ken.

If you have a timer, and you know exactly when your plane will shutoff, you could in theory doodle around to pull the shutoff point back in the circle, or fly high to push it forward.  The timer would remain "autonomous" per the new rule, so you could still effect shutoff where you want it (with some skill on your part) while cleaving to the letter of the law.

[Igor Burger]

As I wrote in rules section:

http://stunthanger.com/smf/index.php?topic=33941.msg353733#msg353733

Radio cut off was ment from begin as an emergency tool especially for combats for cancelling flight, the same way as in FF. So it should not be used for controlling landing maneuver. However I do not see how it should prevent usage of TIMERs. 

[Tim Wescott]

As I wrote in rules section:

http://stunthanger.com/smf/index.php?topic=33941.msg353733#msg353733

Radio cut off was ment from begin as an emergency tool especially for combats for cancelling flight, the same way as in FF. So it should not be used for controlling landing maneuver. However I do not see how it should prevent usage of TIMERs. 

So, is anyone trying to use radio for a cutoff in stunt in FAI, and are they getting away with it?  I'm not sure whether it's realistic or cynical to even ask -- I fear that it's realistic.

[Igor Burger]

I did not see anyone to use any remote cut off on FAI stunt planes. And I do not see any reason to use it myself. I have timer, everything works well, but I can imagine it could be good thing for beginners (in case of crash, in case of inability to continue etc) but I do not think it is any issue for F2B rules :- ))

[Dave_Trible]

A shot with all electronics on board, pre-programmed and checked with the Jeti box (thanks Igor!) and now waiting to be packed into the belly with Velcro and sticky foam tape.

Inside the fuse; top left, accelerometer sensor
                        top right, ubec
                        servo and switch
Outside fuse left top;  Futaba 5v regulater
                   left bottom, timer on end accelerometer sensor
Outside fuse right; 180 mAh 2 cell LiPo
                   bottom,  charge lead

I think on future builds I might build compartments for this luggage in the wing roots outside the fuse.  Even though I have a charge lead I am still going to remove the battery for charging.  No reaso to chance lighting up a good airplane.  Still a few weeks out before I'll know much about how well this works.  I want to flight trim the new machines pretty well and have some fit issues with the gadget on the engine.  Would also like to test that out on the motor test stand before it goes in the airplane.  Then we'll get this airplane re-trimmed some and go for a system calibration flight.  Then we can play with servo inputs and go from there.

[Dave_Trible]

I also got the phase 1 system less accelerometer set up in Asteroid today.  Really all I had to do was pull the 2.4 ghz receiver out and plug the programmable timer in its place.  Then I programmed in a simple flight time and shut off servo response into the timer ( 6 min. 5 sec. Flight time with a 4.5 second servo turn at 98% travel.). Could plug the radio unit back in and change nothing if wanted.

[Igor Burger]

Dave, do you have any protection (some shielding or so) to protect all electronic components from pipe heat?

[Dave_Trible]

No not yet but I am concerned about it.  Thought I might cover everything in aluminum foil.  Do you think that will be adequate?  Open to ideas.

[john e. holliday]

I would think of something different than aluminum foil for insulation.   You need something that doesn't transfer heat. 

[Tim Wescott]

I would think of something different than aluminum foil for insulation.   You need something that doesn't transfer heat. 

Aluminum foil would make a good heat shield if you had a source of cool air for the electronics.  Ideally it'd entirely or largely keep the hot air from the pipe from going past the electronics.  If you could keep it clean you'd want the shiny side toward the pipe, but I suspect that after a season's accumulation of fried-on castor droplets, you'd be better off going shiny side toward the electronics.

Just wrapping the electronics in aluminum foil and hoping for the best would slightly slow, but not at all prevent, the heat from transferring.

[Doug Moon]

It would seem with this system you could eliminate the pipe.  Using a can muffler in its place. You are no longer using the boost/restriction from the pipe.  Then place the electronics in a compartment behind the exhaust area.  Only thing in the heated area would be the servo and the wires.  Using a sub-micro servo would be more than enough power to run it, but you need to make sure it can take 7.4 or you fry it about 2 minutes in. A simple in-line step down cures that issue so you can still run 7.4 to the rest of the system if it needs it.  The sub-micro is so tiny it can be far enough away not to get hot.  The wires can be tucked away as well.

This is going to be interesting for sure.

[Dave_Trible]

Doug that is a thought about removing the pipe... I have a rear exhaust muffler.  I'm not quite ready to surrender my pipes yet though.  My thought for now is a small range in power adjustments of maybe just a few hundred rpm.  Maybe as I gain more knowledge and confidence that the engine will respond fast enough then I'll give the system more latitude.  I'm going to try the foil.  My pipe tunnel is really wide open with the pipe totally exposed.  I think it will cool well enough in the air.  My concern would be after the engine quits and heat just rises up into the electronics for a short while.  The voltage issue is why we went with the 5v regulator.  We needed more than the single cell LiPo would give for active regulation ( but is fine for the phase one system) but 2cell batteries were 7.4 volts.  The Jetibox needed at least 5v to program either system so the regulator became nessessary.  Phase 1 timer was programmed out of the airplane with 5volts then plugged into the airplane. The other system can be done in the airplane, though I'll pull the LiPo out to charge where I'm OK with charging the single cell in the bird.

[RknRusty]

Just to be clear, as Doc pointed out, aluminum foil will bring heat To your electronics From the hotter pipe, not the other way. Aluminum is the heat super highway from a hotter place to a cooler place.
Rusty

[Dave_Trible]

I'm still open for ideas on this Rusty.  My thought is at least there will be some shield instead of none.  There isn't much room for anything thick between pipe and gear and can't weigh much.  One continuous sheet of foil laid loosely on top of everything front to back would seem better than nothing.  Still listening for something better....

[Tim Wescott]

On the foil: it can act as a heat shield, but not as an insulator.  It'll stop convection if it's wall-to-wall, and it'll stop radiation if it's shiny.  The "stops radiation" is why "space blankets" are shiny, and that's why they work.

If you look at the old pictures of the Gemini capsule in space, you'll see that the back of one of the sections was covered with gold foil -- that's because gold reflects infrared, which makes it a heat shield.

If you were to put the foil in contact with the electronics and all that in contact with the pipe, then you may as well not have the foil.

A thin balsa wall, with aluminum foil on the pipe side, shiny side toward the pipe, will provide insulation, it'll bounce the infrared back toward the pipe, it'll be light, and it should be easy to mount.  Think on that...

[Dave_Trible]

OK well maybe I've got something.  I have some roll cork shelf liner just under 1/16" thick.  It's very pliable and easy to work with.  To that I can glue foil on one side.  This I can stick down with the sticky foam tape on top the electronics.  Sure I'll tear it up when removed but I have yards of it to use.  Maybe this will make everybody happy!!  LOL!
Oh it's self adhesive.  Even better to attach the foil.

[Dave_Trible]

I manufactured the new space insulating material.  The cork with aluminum foil skin.  I really do think it will work.  I'll try putting it on the Asteroid tomorrow.

[Doug Moon]

Doug that is a thought about removing the pipe... I have a rear exhaust muffler...

Your pipe is going to react faster than throttle response ever will in our application. If using a pipe and the accelerometor one could confuse the other??  Maybe.... 

The engine is still beholden to the laws of physics.  Our electric brothers are not.  So when you point the nose up the motor is going to feel the added load and it will break on its own regardless.  The pipe reacts faster due to the change in soundwaves from the increased rpms. 

The throttle response will be different.  By removing the pipe and riding on a muffler you could run a setup that breaks pretty strong in the corner then the accelerometer shuts it down with the choke to get it back to the normal operating rpm.  I don't know the ins and outs of it but I think you can set how long it waits to respond so you could fly the corner and shut off the break, and vice versa,,,,  going to take alot of programming and test flying to get this just right.  Should be very interesting for sure.

What exactly are looking to achieve by using both pipe and accelerometer??

[Dave_Trible]

Doug there is so much to be learned here.  In fact the accelerometer could prove not to do much for us but the programmable timer application will be very useful.  Something I was surprised to see was watching video of my own practice and also a number of team trials flights.  When seen especially in slow mo you can see just how much the airplanes slow down at the tops of loops and in verticle manuevers,  even with the pipe doing its thing.  Obviously heavier airplanes, less power and slower lap time exaggerate the slowing.  The speed itself isn't the issue but what it does to manuever- or the illusion of manuever shape maybe- is.  If the airplane can keep most of its speed the manuever should be easier to keep round for example.  You shouldn't need much correction through the manuever due to changing speed, ie., lift and centrifugal force during a turn.  The pipe sure does this to a large degree but not quite enough in some circumstances.  My project would be to give the pipe a little help.  As I mentioned earlier my .76 airplanes which are lighter this year don't seem to need any help but the .61 or any set up that doesn't yield the horsepower of that .76 could be helped quite a bit if this works.  Will it make you fly a perfect pattern?  No.  But it should make getting there a little easier to do. 

[Tim Wescott]

The engine is still beholden to the laws of physics.  Our electric brothers are not.

I don't think you mean quite what you said.  Until God reaches down from heaven and touches what we're doing, we're all limited by the laws of physics.  They just apply differently in the case of electric power.

I had a discussion with a helicopter-flying club-mate about this sort of thing, and he came up with a very helicopter-pilot sort of suggestion: use an engine that's actively regulated for constant speed, and a variable-pitch prop.

No, I don't know if it'd even start to be worth the extra weight and complexity.

[Derek Barry]

: use an engine that's actively regulated for constant speed, and a variable-pitch prop.

Now that is a cool idea! I have seen the 4D foam planes fly and they can do some crazy stuff. Imagine being able to fly down to 5 foot super slow then accelerate out of the corner. It may be pretty difficult now that I think about it but you could certainly slow it down quite a bit. Pretty much what Paul was getting with his but you could possibly get a little more with the variable-pitch prop.

Derek

[Doug Moon]

I don't think you mean quite what you said.  Until God reaches down from heaven and touches what we're doing, we're all limited by the laws of physics.  They just apply differently in the case of electric power.

Yeah, what I meant was when you add load, IE pointing the nose up, to a 2s motor is will break.  The electric motor will not do the same thing.  In fact with no governor in place it should slow down a little.  With a gov in place it will maintain RPM no matter what the plane is doing.  The plane and the motor are separate in that one is changing many things while the other is doing all it can to no change anything one tiny bit. The accelerometer brings the two together again. 

I had a discussion with a helicopter-flying club-mate about this sort of thing, and he came up with a very helicopter-pilot sort of suggestion: use an engine that's actively regulated for constant speed, and a variable-pitch prop.

No, I don't know if it'd even start to be worth the extra weight and complexity.

HAHA!! Now you are talking, BRO!!! That's how they fly all that 3D stuff with accuracy and the ability to stop on a dime and start again.  It's all in the blades.  The motor/headspeed is constant never changing. Their governors are pretty dang quick and can regulate very fast to keep things at a contant motor/head speed. OK, so who's gonna try it first??

[Tim Wescott]

HAHA!! Now you are talking, BRO!!! That's how they fly all that 3D stuff with accuracy and the ability to stop on a dime and start again.  It's all in the blades.  The motor/headspeed is constant never changing. Their governors are pretty dang quick and can regulate very fast to keep things at a contant motor/head speed. OK, so who's gonna try it first??

Come to think -- does anyone already make an assembly for an IC engine?  If so, then way more than half the work is done.

[Eric Viglione]

Finally, a real world use for accelerometers that makes sense. Can't wait to upgrade my phone. And think of the sales potential, all the people dropping their phones just to hear it scream...

EricV

[Dave_Trible]

A little (very little) update on testing Briddled Thunder.  Too windy to fly this morning so mowed some a took along my engine test stand to the field to finally try out the variable Venturi on the .61 Jett.  First thing I noticed was the engine was already in a solid two before I got anywhere near my launch RPM.  The ID is small so I'll need to bore it out to what I'm using for my regular set up.  This requires use of a remote needle.  This showed no problems and gave a wide and smooth range of adjustment.  This will narrow when I bore the Venturi out.  The engine would reliably idle down to only about 4000 rpm.  It may be enough for a idle-up launch.  The thing I most wanted to know was how much range I could expect for instant response without much dwell time.  I'd say 500 rpm is pretty much instant up or down.  That should be plenty for active regulation.  At a certain needle setting that got me from a solid four to a solid two and back.  This was done without pipe.  Don't know yet what that will do. 
My thinking for now is that my time until the Nats will be better spent on practice than on tinkering and since I'll be using a .76 this time, further work with the accelerometer and the .61 will need to wait until after.  I might well be using the timer though.

[john e. holliday]

Dave have been by the field and see that you have mowed the perimeter and a take off section.   Need to get off my duff and get the rider out there.   But, Thursdays is spent at the clinic getting the injections in the knees.   Two more weeks of them and then Brodaks.   School will be out and maybe I can get out to mow more than I have.   Yes it has been windy on the days I can fly.   But, was told I should not go flying alone anymore,   But do I listen.

[Dave_Trible]

John I got it all mowed yesterday.  The mower blew up last week and had to buy a new one but back in business.  Get out and get ready for the contest!  Thinking my next chance with work will be late Friday.  Nothing else I'll see you in Topeka Sunday.  Kevin crashed the Stuntman last weekend so he may finally be flying the Trivial Pursuit he built like 4-5 years ago and never flew.  See ya!

[Dave_Trible]

Kevin (Prier) sent me this shot this morning of his new machine coming along.  It's his first self-design and is loosely patterned after a P40.  Originally set up for the FP40 but recently changed over to RO Jett .40 with rear exhaust muffler.   I really am looking forward to seeing this one fly.

[john e. holliday]

Don't tell him the old DOC says it looks great.  Don't want him to get big headed.