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  #1  
Old 08-15-2018, 01:34 PM
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Gus Gus is offline
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Default A novel cluster igniter at WSMC

Oh how we miss Q2G2's!

Just got back from the World Spacemodeling Contest in Poland and wanted to share something our British friends came up with.

For the S2P Precision Fragile Payload event the goal is to fly a raw egg to 300 meters with a flight duration of 60 seconds. Three flights, total is added, egg compartment is only opened after the 3rd flight. Very similar to TARC except that there are 3 flights and no construction requirements, any motor and rocket combo is OK. Huge fun.

The Brits entered two teams (3 guys each) and finished first and second as teams, 1st and 3rd individual. (I finished 4th, 0.3 seconds out of 3rd, ouch, LOL). Tremendous consistency and reliablity and solid design.

But what was really interesting is that the Brits flew 3 motor clusters of Estes D12's with a really novel ignition system. In the S2P event most of the foreign flyers do not have access to either Estes or Aerotech motors (which is what the U.S. flew). The Brits had great Estes motors but not such great cluster igniters, so they came up with their own.

Basically, the Brits used cellophane quickmatch to tie together what looked like fireworks fuse in each of the 3 motors. Fuses were held in by split Estes white igniter plugs. Quickmatch connected the 3 fuses and was electrically ignited by an Estes igniter. Really clever, really consistent, and really reliable.

After the contest the Brits flew a goofy 4 engine cluster rocket made out of rubbish. I got a nice picture of the igniter system and the rocket with all 4 motors ignited (below).

Just thought you folks would appreciate how our British friends successfully stretched the envelope!
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  #2  
Old 08-15-2018, 01:59 PM
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Hilarious pics.
Instead of "Egg Lofting" that cold be known as "Trash Lofting".
Almost as fun as BOWLIN' BALL Lofting.
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Old 08-15-2018, 03:47 PM
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It was allowed at WSMC, yet I was crucified for even talking about flash pan ignition on TRF. There isn't even much difference in the amount of BP used....unless you just like to see big fireballs and scorched rocket tails!

Now I'll have to build myself a separated cluster to play with. Classic green cannon fuse burn rate is about 20s/ft to 30s/ft according to brand, IIRC. I believe the pink thermalite I used to have was about 20s/ft.

With that cannon fuse for the final ignition phase, timing might not be perfect. A good stiff decent length rod, rail, or tower would be a good idea. Not that it's ever a bad idea.
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Old 08-15-2018, 06:24 PM
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ghrocketman ghrocketman is offline
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The shorter the pieces of cannon fuse you use the closer the ignition time of each motor will be.
Back in the 80s/90s I used cannon fuse exclusively for igniton of all non-clustered flights. I NEVER had a failure to ignite the motor. Far more reliable than solar igniters.
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  #5  
Old 08-15-2018, 06:43 PM
olDave olDave is offline
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Default We need some official NAR definition of what is allowable

Quote:
Originally Posted by tbzep
.......yet I was crucified for even talking about flash pan ignition ......


IfI am reading that picture correctly, that cellophane quickmatch fills that whole outer circle? Does that stuff really burn fast enough to ignite all the individual motor fuzes simultaneously? (or nearly so?)

Here in the USA, possession and/or use of loose black powder for anything other than a firearm seems to get you immediately into trouble with local authorities who are generally unfamiliar with rocketry. We could sure use some clarification from the NAR, citing specific federal statutes, and an additional letter of approval from the ATF wouldn't hurt. It is already OK to use BP for ejection charges, but even THAT application raises the eyebrows of the police. We need some legal help in this area before our hobby gets strangled even more.

(As far as crucified on TRF, just consider the source, most of those people don't know what used to be allowed in NAR competition or what is legally allowed to be done under current laws, all they care about is how big a motor they can find in a sparky version and how much fiberglass they can plaster onto a rocket)
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  #6  
Old 08-15-2018, 06:51 PM
olDave olDave is offline
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Default And about that cluster---

Those outboard motor locations seem (to me, at least) to be unnecessarily spread apart. Maybe I don't understand whatever configuration limitation required this, but it looks borderline unsafe to me.

One late ignition, or one failed ignition, and that thing looks like it would be prone to cartwheeling above the end of the launch rod/rail. A healthy dose of extra launch rod/rail length would seem to be indicated.

If I was serving as RSO, that rocket would be assigned to an "away" pad.
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  #7  
Old 08-17-2018, 04:48 PM
vcp vcp is offline
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Quote:
Originally Posted by olDave
... all they care about is how big a motor they can find in a sparky version and how much fiberglass they can plaster onto a rocket)


That cracked me up.
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  #8  
Old 08-17-2018, 04:58 PM
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Jerry Irvine Jerry Irvine is offline
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Quote:
Originally Posted by tbzep
It was allowed at WSMC, yet I was crucified for even talking about flash pan ignition on TRF. There isn't even much difference in the amount of BP used....unless you just like to see big fireballs and scorched rocket tails!

Now I'll have to build myself a separated cluster to play with. Classic green cannon fuse burn rate is about 20s/ft to 30s/ft according to brand, IIRC. I believe the pink thermalite I used to have was about 20s/ft.

With that cannon fuse for the final ignition phase, timing might not be perfect. A good stiff decent length rod, rail, or tower would be a good idea. Not that it's ever a bad idea.
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  #9  
Old 08-17-2018, 09:38 PM
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Quote:
Originally Posted by olDave
(As far as crucified on TRF, just consider the source, most of those people don't know what used to be allowed in NAR competition or what is legally allowed to be done under current laws, all they care about is how big a motor they can find in a sparky version and how much fiberglass they can plaster onto a rocket)

While that's true, it was somebody that flies tiny rockets and takes tiny pictures that started the flogging, then a bunch of lemmings chipped in their blind support.
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  #10  
Old 08-18-2018, 04:14 AM
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Leo Leo is offline
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Quote:
Originally Posted by Gus
...

Just got back from the World Spacemodeling Contest in Poland and wanted to share something our British friends came up with.

...

What they came up with is actually a product from Raketenmodellbau Klima GmbH

Tape Match

I don't why the brits used wicks. For instant ignition in conjunction with the tape match you would use these:

Igniter sticks

I fly all my cluster in this manner...



... be it single stage or multi stage rockets.



Ignition is super fast and very reliable.

Here an example video of the startup ignition in slow motion:

Click me video
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