2 stage ignition

Thermalite.

SIMPLE AS FALLING OFF A LOG AND NOW IT IS DIPPABLE.

not to say anything is better or not, but alternative systems are out their. My friend Fred uses a Perfect Flite Mini timer 3 hi current timer. About $35.

it can use a pull wire, or g switch.

ohh the days gone by, and thermalite air starts on my LOC Heavy Duty beauty and thoughts of the ultimate on seven motors. the smell of rocketry.

But now that most people can not get thermalite, I have to use air start timers and dipped ignitors to finally get my 1988 ultimate flying two weeks ago. And no, its not about a leup, it's that it's not out their to get readly.

Art

Point.

The better way is to have the timer/stager located in the upper stage rather in the interstage coupler as PML has it.

JD

I'm planning on flying my Ultimate Max next weekend (weather permitting) on a J330 airstarting 3 H123's and 3 I161's. Thermalite :-)

Tom

Take a lot of photos and videos, especially including prep. "Last known photo" sort of thing for the future whipper snappers :)

I'll even create a Thermnalite web page for you if you want.

I recommend Thermalite, if you can get it. But that can be tough to come by these days, so you'll probably need some kind of electronic igition. A simple timer will do, in fact I'd say the simpler the better. PerfectFlite makes some great timers that are relatively cheap, very tiny and quite reliable. There are others on the market, but I have no personal experience with them.

So what is thermalite and how is it used?

This should be in the FAQ.

I sell AIR-3 (for a pittance) which answers the question.

Hi Tim,

I scratch-built my second stage ignition circuit from the schematic for a launch controller out of the old yellow pages of the older Estes catalogs, substituting the filament continuity bulb with a shock proof led, and the momentary push button with a microswitch that sensed stage separation wired into a NC (instead of NO). Ran the thing off of 9-volt duracell ultras and fired off home dipped Ignitor man ignitors until the cows came home. This method was also printed up from the Launch Pad. Material costs was pretty much limited to the LED, microswitch, safety switches, a battery holder and a terminal board--Prolly < $8 ?

I've seen the G-Wiz stuff work reliably also...

Good luck with your project.

Andy

For those experienced using timers for 2nd stage ignition, what methodologies do you use to determine the timer's time. I would assume that altimeters might be more precise but more complex than timers. If a person decided to use a timer instead, what should he know? how does he determine the time to use?

shockie B)

I used a g-wiz for perfect ignition of my L1860 -> J460 Terrier-Sandhawk. Some people disagree with the need, but I recommend a faster propellant in the upper stage for easier ignition.

Also, be sure that you secure the sustainer ignitor so that it doesn't slip down the motor core under acceleration. To prevent that, I made a "thermalite spider" and pushed a small section of the bare thermalite core wires into the forward face of the uppermost grain segment.

Philip

A wood dowel also works well to keep igniters at the head end.

Stronlgy agree on the high thrust upper. Also keeps the flight far more vertical.

depends on what you want. booster motor bruns for 1.5 secs. I set the timer for 1.2 secs and allow the extra .3 seconds for the time it takes te ignitor to ignite the upper stage.

for max altitude, you might delay the upper stage ignition some. do some roc sim work and 5-6 sec delay between say a j285's burnout and a I160 upper statge ignition can produce an extra 1000 foot altitude !

PS,

I learned this from Trip Barber's delayed staging article in like 1973 or 4. they used B-4-2 as booster motors to get better altitude.

Absolutely correct! If the stages drag separate before sustainer ignition, ... well, that's bad. Also with the timer in the sustainer one can delay sustainer motor ignition until the stages have separated. I learned this the hard way

- a J350 igniting before stage separation really makes a mess of an epoxy-coated (for protection, I thought) interstage coupler. Besides, sustainer coasting and then ignition is way cool! Just don't let it coast too long (not way cool). If the stages won't drag separate (been there too - not good) use a small BP charge in the interstage coupler to make them seperate. Some people wire this charge in parallel with the sustainer igniter but I now use a separate timer (PerfectFlite MT3) in the interstage coupler to fire it. At first this all seemed more complex than necessary, but it would have saved me more than the $40 for the second timer if I had done it before the first flight. However, if the rocket is light and uses small motors (H), one can get away with less complexity and still have an undamaged rocket. Larry (staging composites is the best!) Lobdell, Jr.

I assume you want to know about ignition and not parachute deployment, so I would never use an altimeter for motor ignition. If the sustainer was ignited at booster apogee it would have very little speed and would be almost certain to be pointing any other way than up. Very bad time to ignite a motor :( I use a timer, and for the total time, I add the published motor burn time, one second for the sustainer motor to ignite, and however many seconds I want the sustainer to coast before ignition. Has worked good for me, so far. Larry Lobdell Jr.

Thermalite is igniter cord. A very hot burning fuse with a consistant burn rate. To use it to light an outboard, you take a length long enough to reach from the top of the outboard motor and down to under the nozzle of the main motor. Place a sheath (shrink tube) over the part up in the outboard motor, leaving 3/4" or so bare. This carries the flame to the front of the motor, preventing ignition at the nozzle end. The other end of the Thermalite hangs below the nozzle of a ground started motor. On liftoff, the outboard fuses are lit, carrying the flame to the head end of the outboards, igniting them. Inside the sheathing, the Thermalite burns very quickly, without coating, much slower. By controlling the amount of bare Thermalite between the main motor and the outboards, you can control the amount of delay before outboard ignition. There are also different speeds of Thermalite which allows even more control of the delay.

ATFE says you need a permit for purchase and storage.

Tom