2.4 Ghz for engine cutoff - Anyone using this?

[Fred Cronenwett]

In 2015 the CL stunt rules were changed to allow 2.4 Ghz to be used for retracts and engine cut off in CL stunt. 2.4 Ghz has been legal for CL carrier and scale since 2013.

Is anyone using a 2.4 Ghz system to kill the engine for CL stunt? And if so what time of controller are you using? The on board system would be minimal, a very small servo, tiny battery and small receiver. The servo would have to trip some kind of mechanism to pinch off the fuel line

Fred

[Tim Wescott]

I'm using a TUT, servo, and battery.  I'm not using a pinch-off -- instead I'm using an RC carb.

P.S.:

I know that RC carburetors are reputed to not work well for stunt runs.  However, this one -- a stock carb on a 46LA -- is working well.  Dave Trible had a mechanism shown in one of his posts a couple of years ago that looked like it'd work well.  Using a FF-style pinch-off that's triggered by a servo may work well, too.

[Dave_Trible]

Fred I don't know of anyone using this in competition.  I have a couple different types I've played with some but not used in competition.  The 2.4 units I have are indeed very simple but servo placement and a shutoff gadget that works reliably are harder than it seems,  especially around a pipe and header.  I'm not home right now and  the fellow in Florida who built my units,  the name escapes me.  I'll look later. Another unit I have Igor Burger built for me which uses pre-programmed electronics to kick a servo at a set time.  Again the other issues above tabled my efforts with that until I design the system right into the airplane and build for it.  Until then I'm getting by with the tried and true syringe measuring method.  Maybe I'll find more time to play with that and a couple other projects after the Nats.

Dave

[Tim Wescott]

I'm using a TUT, servo, and battery.  I'm not using a pinch-off -- instead I'm using an RC carb.

I failed to mention: I don't think this is necessary.  It's just so that I can tell myself that I'm making progress with the TUT.  I haven't had an overrun in competition, without using a TUT, for years.  It may be nice for FAI, however.

[Dave_Trible]

Got home and pulled out one of the 2.4 systems.  These are from Micro Flyer Radio and are meant for F2D combat shut offs.  Functions very well.  The battery is a 100mah single cell.  It's good for at least 4-5 flights between charges.  It is charged with dry cells at the field. This small servo has a wire loop on top which will twist soft fuel line off very well.  It's just hard to mount the thing in the fuel path between the engine and tank within a cowling.....?
I was working last on the idea of using a regular arm on the servo tripping a fuel line pinching gizmo.  It's difficult to make one with enough 'pinch power' that this very light servo can trip.
Dave

[Dave_Trible]

...

[Fred Cronenwett]

Dave,

great idea to run the fuel line thru the loop to pinch off the line when the servo moves

This is the basic shorting plug on/off that Dan is using on his Dusty model, I added he 3rd wire so I could charge the NiCad battery.  Basically the same idea as the shorting plug we use for the electric motors but on a smaller scale. that might make the system even lighter and smaller.

Forgot to mention that this shows the Deans charge jack

Fred

[Dave_Trible]

I failed to mention: I don't think this is necessary.  It's just so that I can tell myself that I'm making progress with the TUT.  I haven't had an overrun in competition, without using a TUT, for years.  It may be nice for FAI, however.

Tim the FAI time limit ( and having lost a shot in the top 10 two trials ago due to an overrun) is what inspired me to look for a solution.  Regular AMA 8 minute time frames are really very easy to deal with.  In FAI where you have 7 minutes and you are flying on the slow side in lap times,  you may be looking for a shut off in little more than 30-45 seconds after you finish the clover.  You start counting drops of fuel it seems.  The cutoff loop becomes the main tool in your toolbox.  It works OK but can slow you down just when you need a burst of speed for the one-full-glide-lap required for FAI.

Dave

[Tim Wescott]

@Dave:  Yup.

@Fred:  I've been using a miniature headphone jack, which contains a switch that closes when the plug is pulled.  It's light weight and can be used in conjunction with a battery charger.  All I need now is a little red ribbon that says "remove before flight" in white lettering.

[Lauri Malila]

Dave,

Have you experienced any problems with servo's breaking in vibration? That's my biggest concern. I am building a pinching gizmo in my new model and I'm planning to use Hitec HS35 servo, just because I have lots of them in stock for free flight models.
I just have no idea how well it lasts.

Lauri

[pat king]

Tim,
Why a little red ribbon? Get a big honkin "Remove Before Flight" ribbon. ;-)

Pat

[Dave_Trible]

Dave,

Have you experienced any problems with servo's breaking in vibration? That's my biggest concern. I am building a pinching gizmo in my new model and I'm planning to use Hitec HS35 servo, just because I have lots of them in stock for free flight models.
I just have no idea how well it lasts.

Lauri

Lauri I haven't used them enough to judge it.  To get the servo down someplace near the fuel path I've mounted one just behind the engine in contact with the motor mounts.  Worse case for vibration.  The idea of moving it back over (under) the tank with a pushrod forward to (?) would seem better.  This is where the header gets in the way and you get bad angles going forward.  A pull cable might be better but I'd try to isolate the servo and transmitter.  I did OK with foam pads and Velcro strips to hold things down.  I don't know how much vibration the servos will take.  Sometime we'll find out......

[Russell Shaffer]

The servos should be OK.  The carrier guys have been using them with no problems that I know of.  Mine are hard mounted with no vibration protection and haven't failed yet.  If I was putting a servo in a stunter I would make sure there was access just in case. 

[Fred Cronenwett]

Most servos have rubber mounts built into them and the only failure I have had with a servo was due to fuel getting into the servo. The head of the servo was exposed to the exhaust and over time the servo failed but that has been the only case. If the servo is mounted inside the fuselage you should not have any problems.

You do want access to the servo just in case it fails for any reason

Fred

[Tim Wescott]

Tim,
Why a little red ribbon? Get a big honkin "Remove Before Flight" ribbon. ;-)

Pat

I want a scaled-down big honkin' ribbon.  I figure about 1/2" wide should be about right.

[Jim Kraft]

I have thought of using similar for old ignition engines where I could use the ignition battery to operate the servo and a micro switch to shut of the engine. I use that system on my old time free flights that use a radio, and it works well. However on those the radio battery and ignition battery are separate. Then I could fill the tank and not worry about running out of fuel or an over run. I have had plenty of those.

The best would be just a timer to operate the servo at a preset time without the transmitter and receiver. One of you electronics guys should be able to come up with that and make millions. I know just enough to be dangerous.

There are a lot of micro timers out there, but I have not found any settable to 6 minutes.

[John Rist]

I have thought of using similar for old ignition engines where I could use the ignition battery to operate the servo and a micro switch to shut of the engine. I use that system on my  old time free flights that use a radio, and it works well. However on those the radio battery and ignition battery are separate. Then I could fill the tank and not worry about running out of fuel or an over run. I have had plenty of those.

The best would be just a timer to operate the servo at a preset time without the transmitter and receiver. One of you electronics guys should be able to come up with that and make millions. I know just enough to be dangerous.

Any of the simple timers used in an electric U-control airplane to "time" the the electric motor run can be used to drive a cut-off servo.  The signal out of the timer is the same as the signal out of a 2.4 Ghz receiver. The only problem is making sure the battery voltage is in the right range for the timer.  The timer, in a normal setup, gets it power from the speed controller.  Most speed controllers have a 5 Vdc regulator to provide power for the timer.  A BEC module from Hobby King will fill the bill.  http://www.hobbyking.com/hobbyking/store/__67181__TURNIGY_3A_UBEC_w_Noise_Reduction_AR_Warehouse_.html?strSearch=bec

1 cell lipo is 3.7V which may be a little low. 2 cell lipo is 7.4V  which may be high.  One needs to look at the specks of a Hubin timer.  If it can stand 7.4 volts and the servo can stand 7.4 volts the BEC module would not be necessary.

[Lauri Malila]

Well, I break servo's in free flight gliders, sometimes due to too much force (stab servo) or because they allways do the same movement (hook, rudder or wing wiggler); potentiometer wears out. So what's good in RC isn't necessarily enough for this use.
I'm planning to install the servo near bellcrank and to have a pull cable to actuate the gizmo.
L

[Dave_Trible]

I have thought of using similar for old ignition engines where I could use the ignition battery to operate the servo and a micro switch to shut of the engine. I use that system on my old time free flights that use a radio, and it works well. However on those the radio battery and ignition battery are separate. Then I could fill the tank and not worry about running out of fuel or an over run. I have had plenty of those.

The best would be just a timer to operate the servo at a preset time without the transmitter and receiver. One of you electronics guys should be able to come up with that and make millions. I know just enough to be dangerous.

There are a lot of micro timers out there, but I have not found any settable to 6 minutes.

Hi Jim!  From the fertile mind of Igor..... Exactly what you were talking about.  The 'brain' is the little berry in the lower right corner.  It's set with a Jeti box.  It pretty much just replaces the 2.4 receiver.

Dave

[Dave_Trible]

And this?  Top Secret.... Code name Bridled Thunder.

[Tim Wescott]

I have thought of using similar for old ignition engines where I could use the ignition battery to operate the servo and a micro switch to shut of the engine. I use that system on my old time free flights that use a radio, and it works well. However on those the radio battery and ignition battery are separate. Then I could fill the tank and not worry about running out of fuel or an over run. I have had plenty of those.

The best would be just a timer to operate the servo at a preset time without the transmitter and receiver. One of you electronics guys should be able to come up with that and make millions. I know just enough to be dangerous.

There are a lot of micro timers out there, but I have not found any settable to 6 minutes.

It's called a TUT.  If you're serious, send me a PM.  If you're using a LiPo for the ignition system you can probably run the TUT off of that.

[Jim Kraft]

Hi Tim. I just went to Igor's site and was lookin at his timer. I have all my ignition planes set up with three nicads or nimh batteries which only gives about 4.2 volts fully charged. I don't know if that would be enough to operate the timer. Also, what kind of current will these little buggers take? It seems to me that if they would handle the current then I would not need a servo but just do the switching to the ignition through the timing device.

Or am I missing something here? Even if I had to run a servo I could make up a small battery pack to operate the timer and the servo to operate a micro switch like on my FF planes.

[Tim Wescott]

Hi Tim. I just went to Igor's site and was lookin at his timer. I have all my ignition planes set up with three nicads or nimh batteries which only gives about 4.2 volts fully charged. I don't know if that would be enough to operate the timer. Also, what kind of current will these little buggers take? It seems to me that if they would handle the current then I would not need a servo but just do the switching to the ignition through the timing device.

Or am I missing something here? Even if I had to run a servo I could make up a small battery pack to operate the timer and the servo to operate a micro switch like on my FF planes.

I can't speak to Igor's timer on this, but the TUT works fine with a LiPo battery -- I'm using it with a servo that's specified for operation on 3.7V, and things are working well so far.  I'm a bit concerned about the servo's longevity -- it's teeny, and meant for an electric plane -- but we'll see.  It should still be working fine long after the battery is fried.

Since the 'U' in TUT is "universal", I can set it up to just turn a line on or off (as opposed to a "servo style" output, which is pulsed).  That can be use to turn the power to the ignition system off via a single FET, which should be all you need.

Igor can probably do all this, too -- you'd have to check and see if he'd be interested.

[Jim Kraft]

Thanks Tim. After thinking about it, I put the micro switch in the lead to the points which carries very little current since it is only operating a transistor, but does fluctuate a lot as the points open and close. I will have to go to Igor's site and read up on the operation and see if it can be moded to work for me. Maybe I can get a few more guys flying ignition. Sparky engines are very tempermental on fuel load as to timing advance and needle setting.

I had a super high flight at VSC a few years ago but ran over on gasoline by 8 seconds. I had let it set on the black top for about 5 minutes full of gasoline, and it flooded itself which cost me a full minute in starting. I have learned to start them and shut them off before giving the hand signal to start, and then they always start right back up. Usually not necessary, but it never hurts. Most times I can start them on the first or second flip.

[Jim Kraft]

I just read up on Igor's site about the logic of the timer. It will operate down to 3 volts, and has a logic output that will carry 20 ma of current. I will do somemore checking and contact Igor to see what would work the best for our application.

Thanks for the input Dave and Tim.

[John Rist]

Hi Tim. I just went to Igor's site and was lookin at his timer. I have all my ignition planes set up with three nicads or nimh batteries which only gives about 4.2 volts fully charged. I don't know if that would be enough to operate the timer. Also, what kind of current will these little buggers take? It seems to me that if they would handle the current then I would not need a servo but just do the switching to the ignition through the timing device.

Or am I missing something here? Even if I had to run a servo I could make up a small battery pack to operate the timer and the servo to operate a micro switch like on my FF planes.

Whats the link to Igor's web site?

[Jim Kraft]

Hey John. Just google Igor Burger and it will come up.

[Lauri Malila]

Hi.

Well, I don't use 2,4 Ghz but it doesn't matter. Here are some pictures of the mechanics for my new model.
Total weight of the system with Hitec HS35HD servo and 70mAh LiPo cell (I think they are strong enough) is 14g (1/2oz.)
It looks a little ugly as I am in a hurry.


Lauri

[Lauri Malila]

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