Igniting Clusters

If the J350 has enough thrust to achieve liftoff on its own, then what you can do is use a G-Wiz LC accelerometer flight computer in the "cluster mode" (selectable by a jumper on the circuit board), where it fires one of its pyro outputs when it sees a launch detect.

Ignite the J350 from the ground-based firing system, and use the G-Wiz to start the outboards when it detects the acceleration from the J350.

-dave w

Your thinking is a little backwards... All though you might like to have the J come up to pressure first , most likely it won't. I've flown numerous clusters & the smaller motors kick up first because there is less volume to pressurize. You could use 2 igniters or a double dipped igniter for the J to ensure that it does light first & just a plain single dip for the H's.

JD

I think he said that he does expect the J350 will take longer.... so maybe you reading is a little backwards? :-) Just messing with you, don't get mad!

Also, it is important to know that all you have to do is get the propellant for all motors lit before the rocket lifts off; they don't all have to come up to pressure. If the H128's come up and start to lift the rocket, and the J350's propellant is lit at the top but comes up to pressure as the rocket is going up the rod/rail, that would be OK. What is NOT ok is that the igniter gets pulled out before the propellant gets lit.

Your suggestion of 2 igniters in the J is a good one; I think I'll try that for my next cluster.

Well, so long as the H's have enough thrust to get the rocket stable by the end of the rail. Anyone see that video of a LOC magnum on 2 rocketflite motors and a kosdon I500? The smaller motors lit first, the rocket left the rail, pretty much stopped, and then the I500 kicked in. Someone posted it up on here a while ago...

snip

That sounds interesting. Got any video?

Randy

nice strip of thermalite in the J might increase your odds but it might be better to air start those H's for safety's sake. Do this with electronics or a strip of shrink wrapped sheathed thermalite that has a small unsheathed portion under the nozzle of the J.

Koen

Method 1.

Get a package of Pyrodex 50 caliber, 30 gain pellets (not powder). A 50 cal pellet should fit in the core of an AeroTech 38mm motor. Put one pellet in the top of the core of the top grain of the J350. Cut a pellet so that about 1/2 of a pellet fits in the top of the top grain of each H128s. Use Daveyfire N28F (F, not B, although a B would probably work, too) igniters. Make sure the Daveyfires touch the pellets. The Daveyfires will ignite the Pyrodex, which will ignite the propellant. As long as the pellet ignites you will have a built-in igniter that will continue to try to ignite the propellant until the pellet is consumed.

I've used this method with AeroTech 38mm, 54mm and 75mm motors and get instant ignition. In 54mm and larger motors I stick a toothpick into the smoke grain and CA pellets onto it. (Pyrodex pellets have a hole through the center.)

Method 2.

Daveyfire N28F (F not B) igniter and copper thermite for instant ignition.

Dean

These sound exactly like what a Pro38 uses.

RDH8

I could post it again if you like.......

JD

I've just posted it to ABMR...

Jeff

They sound like it but they're not.

I've just posted it to ABMR...

Jeff

I've just posted it to ABMR...

Jeff

I've just posted it to ABMR...

Jeff

I've just posted it to ABMR...

Jeff

I've just posted it to ABMR...

Jeff

What are some of the technical and practical differences?

Thanks Mike