RC ESC for airstart?

[rrobe99999]

I am getting into RC BGs and have a design in mind for my 3X Orbital Transport. I would like to airstart a motor in the glider after seperation to get a little extra hangtime. It would be cool if I could trigger this with the radio. Has anyone used the output from an electronic speed controller to fire a motor igniter? Of course I would ground test it 1st, but I don't want to buy an ESC if it could not work. Otherwise, I will airstart the motor from a Raven at a preset altitude. I've read that some RC guys fire missiles off of their planes. What do they do to fire the motor?

Russ Roberts
SEARS572

 

[Rex R]

I'd use either a servo activated switch, or an E switch, something like this https://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXCJD6&P=0 before trying to fry an esc .
rex

 

[[POW]Eagle159]

Can't you just use another channel on the radio and then attach the igniter to the receiver... flip switch/press button to send power to the rocket engine......?

 

[mikec]

Can't you just use another channel on the radio and then attach the igniter to the receiver... flip switch/press button to send power to the rocket engine......?

No, receivers output PPM signals, not simple voltages.

A brushed ESC would probably work, though as noted there are R/C switches built for this purpose that might be better. https://www.dimensionengineering.com/PicoSwitch.htm is another possibility.

Launching rockets from airplanes is a violation of the AMA safety code. I think what you're trying to do is OK if you're flying it as a rocket glider and not an airplane.

 

[rrobe99999]

Thanks for the feedback guys. I was originally thinking of using a servo to activate a switch, but wanted to have a soid state solution. The pico switch looks like the way to go.

 

[aerostadt]

I have tried to do this several times on my 4x OT. This first time I used a electromechanical switch and I had problems, so I have gone to a Jomar switch. The wings have been damaged on the last 2 flights sometime during the flight up, so I have not had a good test, yet. There is one problem that I found. I needed 2 arming switches. The R/C receiver must be turned on first before turning on the circuit for the igniter. Otherwise, there is a power surge that goes through the Jomar switch and will likely fire the igniter.

 

[BEC]

Dimension Engineering stuff is good stuff....though the PicoSwitch is only good for 1A (it uses a tiny relay) - so that would limit you to low-current igniters like Q2G2s - not necessarily a bad thing. If I were trying to do this, that's where I'd go.

The Jomar switch is bigger and more expensive, but is solid state and can handle 20A via its power MOSFET. But a 4x OT would have room and could handle the 1/2 ounce.

I didn't realize Jomar products were still available (Joe Utasi sold the business to EMS years ago), but apparently some of them are still out there.

Concur with mikec that a brushed motor controller would do it - even a pretty small one. A brushless one - no. Brushed controllers are getting hard to find. If I were buying new for this application and wanted a speed control I'd probably use the 7A unit here: https://www.electrifly.com/escs/gpmm2005.html

If RC guys are firing missiles off their planes they are either on AMA show teams and have special permission or are in violation of the AMA safety code....

Again, if I were going to do that I'd either grab a small old brushed ESC from my collection or I'd get one of John's switches (the Dimension Engineering ones).

 

[Wingarcher]

+ 1 for the brushed ESC. Small, light, and pretty darn cheap.

N

 

[aerostadt]

I used the pico switch electro-mechanical and it ignited the (orbiter) glider on the pad as soon as I threw the arming switch. This could have been because of the same power surge problem as the Jomar switch, which I solved by later using 2 switches, one for the R/C receiver and one for the arming switch to the igniter. Perhaps, this would have solved the problem for pico switch. I don't know. The pico switch is much lighter and takes up very little space, which I liked. Then again, there is the concern that the pico switch has a mechanical aspect and the acceleration forces might activate it on lift-off. I asked the distributor about this issue, but never got a satisfactory answer. Whichever route you go, I would bench test the device until you are confident that it won't ignite when you activate the arming device on the pad.

The NAR allows for inflight R/C ignition. Check the safety code. As I recall the LCO must be notified in advance, ignition must be 100 feet, and audible countdown must be given.

 

[BEC]

The NAR allows for inflight R/C ignition. Check the safety code. As I recall the LCO must be notified in advance, ignition must be 100 feet, and audible countdown must be given.

Yes, that's true. But launching things from an R/C airplane is a different matter. See screen capture attached:

 

[burkefj]

I've done this many times using a small brushed 7-10 amp speed control from eflite or castle, and a 3 s lithium battery, which is sufficient to ignite copperheads. You could get by with a 2s and smaller capacity if only lighting black powder motors. I use a separate BEC for power, so pull off the pos wire from the esc since the esc bec will conflict with the other BEC, and plug it into the gear switch. I make sure to only connect the igniters to the ignition ckt after the radios are on, otherwise a glitch can set off the igniter. You could do an inline plug as well. I need the bec anyway as I'm running lipo and their voltage range is above the nominal rx input voltage. I have not seen any brownout yet using the same battery to power the rx and light the igniter, but I was using a 1320 mah pack, if you use a smaller battery you might want to use a separate battery for the ignition than for the rx so you don't brown out the rx and cause a glitch. This isn't as critical if you aren't using some sort of spektrum rx.

The 10 amp pixie or similar speed controls are pretty light and not very expensive. You could use the built in esc, BEC if you are only running 2 small servos.

I've used it for air starts, as well as launching off the pad when I didn't have a helper to push the button. I've since gone to a remote push button ignition switch that I can hold in my hand along with the xmitter.

Frank

 

[BEC]

Sadly, Castle Creations doesn't make brushed ESCs at all any more - that's why I linked to the Electrifly ones, which are still in production. But for this purpose a small used one - even a junker (from an airplane point of view) like a WattAge unit would be fine.

It does look like the E-flite brushed units as well as some from GWS are still out there as well....

 

[mercsim]

Read the AMA safety code carefully. You can't launch things but you can ignite a motor still attached to the model such as JATO (RATO) or air start.

Try to avoid the Electrifly ones. They make an excellent product but they have a unique safety feature built in that requires you cycle the throttle to full and back to idle before they arm. This could be dangerous on the ground hooked to a rocket motor and time consuming in the air.

I have air started dozens, if not hundreds of Estes motors. The ESC works fine for this. Be cautioned the ignitor wires could short out upon ejection causing a problem if you are using the ESC to power the radio. I have only had it happen once, but it did happen.

An Estes igniter only spikes up to about 2 amps so any of the small cheapy controllers work fine.

Best of luck. Its a lot of fun!

Scott

 

[burkefj]

That's a good point Scott about the shorting of the wires, normally I use a separate BEC so never ran into that being a problem.

Frank

Read the AMA safety code carefully. You can't launch things but you can ignite a motor still attached to the model such as JATO (RATO) or air start.

Try to avoid the Electrifly ones. They make an excellent product but they have a unique safety feature built in that requires you cycle the throttle to full and back to idle before they arm. This could be dangerous on the ground hooked to a rocket motor and time consuming in the air.

I have air started dozens, if not hundreds of Estes motors. The ESC works fine for this. Be cautioned the ignitor wires could short out upon ejection causing a problem if you are using the ESC to power the radio. I have only had it happen once, but it did happen.

An Estes igniter only spikes up to about 2 amps so any of the small cheapy controllers work fine.

Best of luck. Its a lot of fun!

Scott

 

[BEC]

Try to avoid the Electrifly ones. They make an excellent product but they have a unique safety feature built in that requires you cycle the throttle to full and back to idle before they arm.

Scott

OH! I had completely forgotten about the arming procedure on the Electrifly controllers when I suggested them. Good point indeed.