Fuel cutoff

[Gary Dowler]

A thought occurred to my brain cell yesterday. The sort of random thing that pops into my consciousness now and then, and totally uninvited….lol.

Anyway, I’ve understood that one big advantage to E power is the timer. You can program it to run exactly as long as you want, and it will quit at the same time every flight. Usually.  With Glow, it’s simply not that easy. Lot of trial and error, lot of variation based on altitude, etc. (though I’m sure electrics see increased current draw in denser air as well, but I understand it’s a pretty simple thing to reprogram)

Anyway, has anyone tried a timer activated fuel cutoff?  It seems to my inexperienced brain cell that such a thing would take a lot of the guesswork out of getting the right flight duration with glow power.

Or am I 25 years too late to the party?

Gary

[Brett Buck]

A thought occurred to my brain cell yesterday. The sort of random thing that pops into my consciousness now and then, and totally uninvited….lol.

Anyway, I’ve understood that one big advantage to E power is the timer. You can program it to run exactly as long as you want, and it will quit at the same time every flight. Usually.  With Glow, it’s simply not that easy. Lot of trial and error, lot of variation based on altitude, etc. (though I’m sure electrics see increased current draw in denser sure as well, but I understand it’s a pretty simple thing to reprogram)

Anyway, has anyone tried a timer activated fuel cutoff?  It seems to my inexperienced brain cell that such a thing would take a lot of the guesswork out of getting the right flight duration with glow power.

Or am I 25 years too late to the party?

Gary

   A timer would work and several FF DT timers would appear to be appropriate for the task.  You can also use a 2.4GHZ transmitter to shut it off. Not many people bother because it is easy to hit the 8 minutes without any extra help.
   
    Brett

[L0U CRANE]

I seem to recall. from way back, a simple, non-mechanical, non-electronic cut-off. Was it Igor who set it up?

The fuel tank had a baffle, quite close to the outer wall, that sealed to the tank's interior bottom and the 'inside' and 'outside' walls, but left space along the interior top. With the normal sequence of maneuvers, fuel  will pass over the baffle to the outer volume and reach the pickup to the engine. Early in the run, fuel passes over the baffle due to the 'centrifugal' load's fuel surface angle. Maneuvers requiring inverted flight or outside 'g' place the fuel surface 'above' the baffle, passing fuel to the outer chamber.

After a certain time, that fuel 'surface angle' will not flow over the top of the baffle while in extended level upright flight.The outer chamber fuel is not replenished. Engine stops within a few laps. Sure, this requires some careful development,  and a relatively low vibration engine run... - but there is nothing to be inconsistent, or to cause unpredictable mechanical or electronic glitches.  ... once set up.

Simple things never are...

[Ken Culbertson]

I would love to see a simple light weight "Kill Switch" that is not timer or fuel remaining dependent.  You take off, something is not right or you know what you are looking for and you kill the motor/engine.  From what I gather, they exist but not in 2.4GHZ.  If I am wrong, please enlighten.  It would be a delight at contests.  When I am judging or next up and someone takes an attempt and then the motor proceeds to run for 10 minutes - yuck. Then they do it again on the re-fly - double yuck.   Electric timers are a giant step in the right direction but "on demand" is really what I would love to see.  As I get longer in the tooth, I have lost most of my ability to correctly feel wind direction.  It sucks but having a "kill switch" would let me set my flight time to say 6:30 minutes to allow for those extra laps I sometimes take to get the wind right.  I hate it when we make rules that are specific technology.  They take far too long to un-make.

Ken

[Motorman]

Not a timer but I have a note pad for each plane and fuel with a graduated syringe but most of my planes have the right size tank to just gas and go.

Don't want the neighbors finding out the garage door opener shuts my plane off.

Motorman

[Dave_Trible]

I started working on this a few years ago after having issues with overruns flying the 7 minute FAI pattern.  Igor made me a couple tiny programmable circuits to operate a tiny servo.  At the same time I found a guy (in Florida I think) who makes 2.4 transmitters and receivers for free flight dethermalizers also to operate a tiny servo, run on a single cell lipo you can charge with a D cell battery.  Works great!  The hard part I never got working to my satisfaction was a device to adequately pinch off the fuel line that the tiny servo could trigger.  I sort of settled on a better fuel tank design and didn’t do any more with the other stuff.

Dave

[Dan Berry]

I started working on this a few years ago after having issues with overruns flying the 7 minute FAI pattern.  Igor made me a couple tiny programmable circuits to operate a tiny servo.  At the same time I found a guy (in Florida I think) who makes 2.4 transmitters and receivers for free flight dethermalizers also to operate a tiny servo, run on a single cell lipo you can charge with a D cell battery.  Works great!  The hard part I never got working to my satisfaction was a device to adequately pinch off the fuel line that the tiny servo could trigger.  I sort of settled on a better fuel tank design and didn’t do any more with the other stuff.

Dave

Several outfits are making a radio DT for Free Flight.  Lots of Hald Launch Glider fliers use one that drives a servo. All it needs to do is release a hinged arm to a simple mouse trap. It uses a single cel LiPo the size of a Chiclet. Weight without a servo is like 3 grams.  Ken Bauer's device from Airtek 
https://airtekee.wordpress.com/rdt/
doesn't use the 2.4 hz frequency.
My only concern for Control Line purposes would be the tiny servos having an issue with vibration.

I will bring a unit to the Tulsa Glue Dobber event in September so you can see it up close.

[Ken Culbertson]

I started working on this a few years ago after having issues with overruns flying the 7 minute FAI pattern.  Igor made me a couple tiny programmable circuits to operate a tiny servo.  At the same time I found a guy (in Florida I think) who makes 2.4 transmitters and receivers for free flight dethermalizers also to operate a tiny servo, run on a single cell lipo you can charge with a D cell battery.  Works great!  The hard part I never got working to my satisfaction was a device to adequately pinch off the fuel line that the tiny servo could trigger.  I sort of settled on a better fuel tank design and didn’t do any more with the other stuff.

Dave

It is simple to rig a device that will trigger a shutdown using either a slider switch or mousetrap.  It is finding one workable that is 2.4MHZ.  Don't worry about the neighbor's garage door.  Technology is well past that problem.  I would put the non 2.4 one in a heartbeat if I could use it in competition.  FYI, the mousetrap will work for stunt if set up properly.  Vibration is not a major issue with RC type equipment.  They have it just like we do.

Ken

[Dave_Trible]

Several outfits are making a radio DT for Free Flight.  Lots of Hald Launch Glider fliers use one that drives a servo. All it needs to do is release a hinged arm to a simple mouse trap. It uses a single cel LiPo the size of a Chiclet. Weight without a servo is like 3 grams.  Ken Bauer's device from Airtek 
https://airtekee.wordpress.com/rdt/
doesn't use the 2.4 hz frequency.
My only concern for Control Line purposes would be the tiny servos having an issue with vibration.

I will bring a unit to the Tulsa Glue Dobber event in September so you can see it up close.

See you then!

[Dave_Trible]

It is simple to rig a device that will trigger a shutdown using either a slider switch or mousetrap.  It is finding one workable that is 2.4MHZ.  Don't worry about the neighbor's garage door.  Technology is well past that problem.  I would put the non 2.4 one in a heartbeat if I could use it in competition.  FYI, the mousetrap will work for stunt if set up properly.  Vibration is not a major issue with RC type equipment.  They have it just like we do.

Ken

These devices are now legal in competition.  Frustrating is rigging something in between the tank and engine in the cowling of a stunter and reaching around the fuel tank to activate it.

Dave

[Dan Berry]

These devices are now legal in competition.  Frustrating is rigging something in between the tank and engine in the cowling of a stunter and reaching around the fuel tank to activate it.

Dave

That would be the biggest obstacle.

[Brett Buck]

Technology is well past that problem.  I would put the non 2.4 one in a heartbeat if I could use it in competition.

  That has always been legal. Windy used the Zigras "Z-Tron" as a throttle 20ish years ago, and it was legal then and until recently.  The rule I submitted about it was more about restricting *other* forms of control rather than adding a new one, but it explicitly allows exactly what you want.

     Brett

[Lauri Malila]

.

[Ken Culbertson]

  That has always been legal. Windy used the Zigras "Z-Tron" as a throttle 20ish years ago, and it was legal then and until recently.  The rule I submitted about it was more about restricting *other* forms of control rather than adding a new one, but it explicitly allows exactly what you want.

     Brett

"2.4 GHz spread spectrum radio control signals may be used to control
retraction or extension of landing gear and/or a one-time irreversible
engine or motor stop function. Otherwise, all control of the model during
flight shall be through the flying lines. The retraction/extension of the
landing gear and/or motor/engine stop function shall be under the sole
control of the pilot and may not be operated by any other means that direct
pilot control. No other uses or any other means of wireless remote control
are permitted."

The rule clearly states that non 2.4 is forbidden in competition.  You know more about this stuff than I do so please direct me to where I am wrong.

Ken

[Dan Berry]

including your idiotic 2,4gHz requirement.

I will accept the apology that you owe me.
 I have not advocated nor campaigned for the 2.4 hz rule. I HAVE mentioned it.

[Lauri Malila]

.

[Brett Buck]

The rule clearly states that non 2.4 is forbidden in competition.  You know more about this stuff than I do so please direct me to where I am wrong.

Ken

  Sorry, I misread your "non 2.4 GHz." part. So use 2.4GHZ, or better, nothing, because I think even 2.4 will be gone soon enough.

 
    Brett

[Brett Buck]

I think this has allready been discussed here, including your idiotic 2,4gHz requirement. But hopefully that rule is changed at some point, at least when 2,4 becomes obsolete. Untill then, I’d just lie the frequency.
With a stand-alone (from Airtek/Ken Bauer, for example) RDT you can bui

   We'll run our rules, you run yours - except, oops, you don't have any control over your rules because they come from France. Sorry.

   If the AMA rule is changed, I predict it will be changed to "RC is not allowed at all" rather than a different band, at least for stunt.

     I can see now that I made a mistake trying to do something simple that allows RC, all it did was start a bunch of arguments. I ignored my instincts on that one, I should have known better.

     I think there are something like 120 different RC events in the rule book already, people interested in RC can fly one of those.

     Brett

[Dan Berry]

Oh no, Dan, it was not aimed to you personally.

Fair enough. What I read was an assault.

[Lauri Malila]

.

[Keith Renecle]

I seem to remember in the FAI rules discussion that in competitions a remote shut-off would be unfair, and that a shut-off timer was allowed. Remote throttle control was suggested for a few years already by some folks but was never accepted. I also came to same conclusion as Lauri about a small servo that pinches off the fuel pipe but I was looking for something even simpler. So far that has not happened and the small servo's are looking like the easiest solution so my plan now is to use a simple timer with an option for an R/C link as a plug-in for practice flying. I broke my last competition electric stunter  a year ago, so lately I resorted to flying my old IC models and I really missed the convenience of stopping the motor on time.

[Dave_Trible]

I'd seriously be interested to see how someone gets a servo mounted in the right spot to pinch off the fuel line, and if the servo itself had the power to pinch off a normal silicone fuel tubing.  Surgical tubing is a softer material but my past experience with free flight tells me the fuel will turn the tubing to jelly and short order. 
My attempts before were to initially try to simply add whatever hardware to an existing airplane.  I made an aluminum scissor-like contraption to pinch the line but could not find anyplace around the tank, header and pipe to mount the servo and receiver and still get a fairly straight shot forward with a push/pull rod to trigger the device.  Next I decided to build an airplane from the beginning with provisions for the hardware.  I built a Super Shameless with built up fuselage.  I put cheek pods near the nose to give me more space inside.  I provided a space IN the wing in front of the bellcrank to mount the servo, receiver and little lipo. To go forward I used RC throttle cable passing outside the plywood nose doublers,  buried in the 1/8" balsa fuse sides that re-entered the fuselage just ahead of the tank.  Since I wasn't sure which side would end up the best for trigger operation I ran one down each side.  I foiled myself with this by getting the airplane quite a bit too heavy with silk covering and gadgetry so it never flew-I scrapped it out.  I ended up just re-shaping and sizing the fuel tank I was using to minimize the chance of the engine cutting in the first loop of the clover (like a cut-off loop) and flying just a little faster to finish sooner.  Maybe after I retire soon I'll find time to dig the stuff out and try again.

Dave

[Howard Rush]

I used muscle wire for electronic combat shutoffs. It’s finicky, though.

[John Rist]

All of the racing guys use a cutoff that is tripped with full down.  Why wouldn't this work on stunt.  Rarely do you use full down in a stunt pattern.  Or you could trip it with servo but this would add weight.

[Lauri Malila]

.

[Dave_Trible]

Full down would absolutely be a problem in stunt, a safer (fully mechanical) solution would be tripping it with strong line pull. It's been already done by Sirotkin/Kolesnikov/Yatsenko.
The added weight is irrelevant; my system weights 8...9g, and I don't even use a light servo.
Dave; There are many kinds of silicone tubings, you can use something softer/thinner walled for the part that gets pinched. And you can make a very simple piano wire lever/clamp, and mount the servo that pulls a wire further back in the fuselage. L

I will have to play with that idea.  Here is the gizmo I made before.  It takes several ounces of pull to squeeze the tubing well enough.

[Ken Culbertson]

Surgical tubing is a softer material but my past experience with free flight tells me the fuel will turn the tubing to jelly and short order.  My attempts before were to initially try to simply add whatever hardware to an existing airplane.
Dave

My input to this discussion is not to solve the problem, someone will if given the chance, it is to not limit their options.  Simply saying that you effectively cannot have an electronic fuel shutoff in IC gives an enormous advantage to electric.  With all of the recent developments in short range electronics that are not using 2.4 we are hurting ourselves to not allow them in competition.  With electronics, things change overnight.  Imagine if you would if there were rules for some computer competition and they stated that you must use CPM.  It was at one point the dominant OS.

I have flown and competed in most all of the "classical" control line events, speed, combat, carrier, stunt and the same with FF and Soaring.  Now I am down to simply PA.   A lot can be learned from the innovations in other disciplines.  With electronic, all you need is a simple slider switch triggered by a micro-server.  IC is more difficult. You either have to cut off fuel or cut off air.  I think the cutting off air would be simpler that having to worry about the state of your fuel line all time.  A guillotine type really shortens the life of tubing and has to be pretty strong to handle silicone.  I have found surgical too prone to pin holes.

A simple "toilet seat" attachment over the venturi would fit almost anything.   It could be made using the O-ring supporting what is left of your wife/girlfriend's pantihose.  I like your idea of routing the throttle cable and the electronics and servo could go under a false canopy/hatch or under one in the outboard wing.  Too bad we have eliminated the bottom of the fuselage with pipes.  To hot there.  I am currently using a 15" micro throttle cable to drive a CAM rudder and it is more than strong enough.  More than enough to close a toilet seat "clapper" on the venturi and light as a feather. 

I just read the posts while I was writing this.  Any shutoff that is coupled to the controls is a crash waiting to happen.  Maybe the excessive pull could work but both that and the full up/down would not only be on your mind every time you turned a tight corner or started to wind up in a strong wind, but it would add an unwanted shutoff to a serious tension loss when it hits the lines again.  Granted we don't use all of the control we have but there are times we need it. 

Ken

[Lauri Malila]

.

[Ken Culbertson]

Here is my unit. It’s a little strange as I had to make it afterwards into a very limited space. It works ok, but the next one will be completely different; a miniature valve integrated in the remote needle valve.
The bad drawing is something simple you could bend from 1,5..2mm piano wire and mount directly to engine bearer.  L

I like that.  It could literally go anywhere on the fuel line.

ken

[Lauri Malila]

.

[Trostle]

Full down would absolutely be a problem in stunt, a safer (fully mechanical) solution would be tripping it with strong line pull. It's been already done by Sirotkin/Kolesnikov/Yatsenko.

And the "strong line pull" to "trip" a "fully mechanical solution" was banned in the FAI rules almost as soon as it first appeared at a World Championship.
Reference FAI F2b Rule 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."
Years ago when this appeared, Aeromodeller magazine showed pictures and a drawing.  The "strong line pull" was evidently more like a "jerk" at the handle.  I will see If I can find that.

Keith

I posted this and the statement is incorrect.  The rule 4.2.2. e) was removed completely in 2020 after the 2020 rule book was published.

Keith

[Dave_Trible]

Here is my unit. It’s a little strange as I had to make it afterwards into a very limited space. It works ok, but the next one will be completely different; a miniature valve integrated in the remote needle valve.
The bad drawing is something simple you could bend from 1,5..2mm piano wire and mount directly to engine bearer.  L

Very cool Lauri.  Next time I'll try something like yours.

Dave

[Howard Rush]

Reference FAI F2b Rule 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.

I think this was recently repealed. I used such a device last week.

[john e. holliday]

Hey guys take time to go look at the shut off set up on the different control line racing planes.  The servo can be mounted with a flexible cable to trip the shut off that is mounted to the back of the engine or fire wall/bulk head.  Doesn't take that much to pull the cable.

[Trostle]

I think this was recently repealed. I used such a device last week.

??

K

[Lauri Malila]

.

[Trostle]

Yep, the paragraph banning the shut-off was deleted in 2020. 4.2.2 if I remember right. L

Lauri,

I missed that change.  So, thanks for correcting me.  Also thanks for correcting me on the headquarters location for the FAI.

Keith

[Lauri Malila]

.

[Steve Helmick]

I seem to recall. from way back, a simple, non-mechanical, non-electronic cut-off. Was it Igor who set it up?

The fuel tank had a baffle, quite close to the outer wall, that sealed to the tank's interior bottom and the 'inside' and 'outside' walls, but left space along the interior top. With the normal sequence of maneuvers, fuel  will pass over the baffle to the outer volume and reach the pickup to the engine. Early in the run, fuel passes over the baffle due to the 'centrifugal' load's fuel surface angle. Maneuvers requiring inverted flight or outside 'g' place the fuel surface 'above' the baffle, passing fuel to the outer chamber.

After a certain time, that fuel 'surface angle' will not flow over the top of the baffle while in extended level upright flight.The outer chamber fuel is not replenished. Engine stops within a few laps. Sure, this requires some careful development,  and a relatively low vibration engine run... - but there is nothing to be inconsistent, or to cause unpredictable mechanical or electronic glitches.  ... once set up.

Simple things never are...

First I read about this fuel tank being used, it was an Aussie that did it. I got some sketches from one of my Aussie amigos, but for some of the reasons Lou brought up, I didn't bother with it. With our 8 minute flight time, it's just not that hard to get it done with only a little care in fuel load adjustments. One plane (PA .51/pipe), I just cram in all the fuel I can get into the tank (7 oz). Another plane (AAC OS .46VF/pipe), I fill it up and then remove 10cc >15cc. With the Tweester that I gave to Tim, I just filled it to the top front edge of the (clunk) tank while it sat on its wheels. If the pit area was reasonably flat, it worked fine.

The key to getting your flight in and back on the ground under 8 minutes is to know how to start your engine quickly and then quickly adjust the NV. I do that by either pinching the pressure line or blocking off the uniflow inlet several times while watching the tach. The idea is to bring the engine up to temperature where it holds the same rpm several times, then set the NV.

My experience has been that I never get the same launch rpm between AM and PM flights without adjusting the NV. If you watch some guys start the engine and immediately head for the handle, just about the time they are picking up the handle, the engine goes rich. No bueno...    Steve 

[L0U CRANE]

Thanks,Steve, for the author ID. Thinking over my Post#2, I realized I'd described the location of the baffle wrong.

The baffle runs lengthwise -front wall to rear wall - of course. That forms the outboard, smaller, cut-off chamber.

There's been mention of bellcrank-tripped mechanical cutoffs. Back about 1970-71 I made a retractable landing gear stunter -a kit bash of a green box Nobler to resemble a Dewoitiine 320(?) French WW2 Fighter - I used the bellcrank to trip small toggle switches. Like a 3-way hallway switching circuit..(Either end of a hallway can turn on or off the lights.)  I put a bellcrank tripped DPDT toggle switch in to start one function. Another toggle switch, ready to power other function then switch back (to OFF) at full travel.

I did the extreme UP maneuver between the scorable level flight laps and the RWO. Same-same - the extreme DOWN input was after the Clover. And, yes, it did affect things.The only contest I tried to use it in was in Union, NJ, and somehow got a needle too fat for the pull needed to do tightening outsides to trip LOWER the gear. (The D520 had a belly radiator, like many WW2 fighters, so minimal damage, except to my ego.)

Total weight added may have be about 4 oz, including structure mods, two shaved-down Goldberg nylon RC retract linkages and a 4.5 V snap-cap cell as used in Polaroid cameras back then. It did work when things went right. Looked 'nice' with wheels tucked away. My 'level' then wasn't to brag about (has it ever been?) Military moves, family, nearby stunt friends, etc., were not strongly supportive factors Wouldn't trade the memories for anything.