Trouble Lighting Single Use AT G78 Mohave Green.

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jeff2space

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I like the SU AT G78 Mohave Green but the last two or three times they have been difficult to light. The last time I went through three igniters. Any suggestions? Hope this is ok to ask here but anyone use Triple Seven Pellets to assist in ignition? Does it work?
 
Are you keeping them sealed until use? Do you live somewhere humid?

I think the pellet would be too large. I would consider buying a single grain Blue Thunder reload, chopping the grain up, and attaching to your igniter to augment it.
 
Yes I keep sealed until use. Last time I used the day I bought. I'm in WI. I use igniter that comes with motor - AT FirstFire Jr. When that doesn't work I use a Wildman igniter.
 
BP pellets in a small single use is not the best solution. I've had a few stubborn G78's. They're core burning, so if you take a small rod and scuff up the core near the top of the motor, it aids ignition by clearing some oxidation.

I also prefer magnelite ignitors. hot stuff.
 
Single-use, I'd avoid trying the pellet. I've seen good results using slivers of blue to get it going... blue's a lot easier to light.


Later!

--Coop
 
It would probably help if I knew what speed this was at....but you get the idea.....

[youtube]4IbKegUYZX8[/youtube]
 
It would probably help if I knew what speed this was at....but you get the idea.....

Description says 60 FPS, played at 30 FPS and 5% speed. So that would be 2.5% original or 40x slow. Looks more like 20x slow to me with counting frames, but that only works if I'm actually seeing all the frames.
 
"If you take a small rod and scuff up the core near the top of the motor, it aids ignition by clearing some oxidation.", This was the solution for me last week with the same problem/ motor.
 
Description says 60 FPS, played at 30 FPS and 5% speed. So that would be 2.5% original or 40x slow. Looks more like 20x slow to me with counting frames, but that only works if I'm actually seeing all the frames.

ah I did put it there, didn't click to see more. recorded at 60 fps in a 7D, then iMovie killed it to 30 fps, then dragged to 5% speed.

At any rate, they make good fire.
 
Is the AT G78 the same as the Estes-labeled G80? I have one of those that won't light with the sonic ignitors (no surprise) or one of the Crazy Jim starters that are supposed to be able to light everything. I was planning to put it in a desiccator for a couple days and then to scratch the inside with a wire, but maybe a slug of blue propellant is in order too.
 
The Estes G80 is a relabeled Aerotech G80.

A desiccant might help.

Green propellants in particular absorb a lot of moisture making them tough to light. I would think puting the motor in a sealed bad with desiccant should help.

Also, leave them sealed until you are going to use them. I have flown a number of the K805 Green and never had an issue.
 
Is the AT G78 the same as the Estes-labeled G80? ...but maybe a slug of blue propellant is in order too.

As Mark said, the Estes G80 is a relabeled Aerotech G80 Blue Thunder motor. If you burned a couple of the sonic ignitors and then a crazy Jim, you probably just have a bunch of residue built up on the grain face that needs to be cleaned off. Do the small rod, scratch/scuff thing, and you should be good.
 
Mojave Greens are notoriously hard to ignite, I like to use QuickBurst Twiggy igniters if the First Fire doesn't light it. They always work. I suspect there are several other similar igniters around (somebody mentioned the Wildman ones, which I haven't tried), but the bottom line is that you need something that burns hotter and longer than the First Fire.
 
Mojave Greens are notoriously hard to ignite, I like to use QuickBurst Twiggy igniters if the First Fire doesn't light it. They always work. I suspect there are several other similar igniters around (somebody mentioned the Wildman ones, which I haven't tried), but the bottom line is that you need something that burns hotter and longer than the First Fire.

I have flown four K805 Greens, and they all started on the first using the supplied first fire. I think adding a sliver of blue thunder to the igniter will get things going.
 
All good ideas. With the RMS version, I always cut and scuff the crap out of the upper propellant grain with a knife. For an SU, get something long, skinny, and abrasive up in the core and grind away at it.
 
Now here's a question: how much is a "sliver" of Blue Thunder for a SU 29mm, like an Econojet?
 
I think that when new, Mojave Green motors will usually light off without an issue but if they're allowed to age, than like Redline in particular they can become stubborn.

Earlier this year, I flew a 29/40-120 G76G that I've had since 2010. It took 2 AT Firstfire Jr's to get it going. Once lit it was fine and the delay went the full 4 seconds.
 
Now here's a question: how much is a "sliver" of Blue Thunder for a SU 29mm, like an Econojet?

That is a good question. I would think a longish piece that is as large as you can attach to the igniter and still fit though the nozzle. It is not a very big piece, but you could make it as long as a grain is.
 
There is a custom igniter preparation tool that works well for these, bamboo skewers, pack of 100 is a few dollars at the grocery store, use the blunt end and press it in, also helps open up the c-slots that have closed in. They are around .040 - 060 diameter.

Works great.
 
Is the AT G78 the same as the Estes-labeled G80? I have one of those that won't light with the sonic ignitors (no surprise) or one of the Crazy Jim starters that are supposed to be able to light everything. I was planning to put it in a desiccator for a couple days and then to scratch the inside with a wire, but maybe a slug of blue propellant is in order too.

No, the G78 is Green, the G80 is blue. The propellant doesn't get wet so much as exposure to air builds an oxidation on the outside. scuffing the inside should suffice. A few failed ignitions can also build up crud on the inside and make it harder to light.

I have flown four K805 Greens, and they all started on the first using the supplied first fire. I think adding a sliver of blue thunder to the igniter will get things going.

The K's also come with much larger ignitors, that burn longer and hotter.
 
There is a custom igniter preparation tool that works well for these, bamboo skewers, pack of 100 is a few dollars at the grocery store, use the blunt end and press it in, also helps open up the c-slots that have closed in. They are around .040 - 060 diameter.

Works great.

Yep, I always shove one in whenever I assemble a G64. Holds the grains for taping and as you said makes sure the slots are open. I've had several that they were almost swollen shut. And I scrape the inside of the slot (top of the upper grain only) too.
 
Harbor freight sells tiny pipe brushes (5-6 on a key ring) for cleaning air brushes. They are great for cleaning out SU motors to scuff them a bit and brush out oxidation / debris from the first 3 attempts at lighting.

Can't find them on their website, but bought some in the store.
 
Yep, I always shove one in whenever I assemble a G64. Holds the grains for taping and as you said makes sure the slots are open. I've had several that they were almost swollen shut. And I scrape the inside of the slot (top of the upper grain only) too.

Emery boards work great for reloads with a C-Slot.
 
You know, I'm a little surprised to read about this. Last month, I clustered 2 G76 reloads in a rocket, and had not problems at all. Both lit together, and right away. I've also used that motor previously in a 3-motor cluster, also with great results.
But, I will also say I loaded those on Thursday night, and capped them, and launched them on Saturday morning, so I don't think they really had a chance to absorb any moisture.
But, based on what I've seen here, I think I'll stick to the G64 white lightning, at least till they re-introduce the Redline for this case.

Phil L.
 
You know, I'm a little surprised to read about this. Last month, I clustered 2 G76 reloads in a rocket, and had not problems at all. Both lit together, and right away. I've also used that motor previously in a 3-motor cluster, also with great results.
But, I will also say I loaded those on Thursday night, and capped them, and launched them on Saturday morning, so I don't think they really had a chance to absorb any moisture.
But, based on what I've seen here, I think I'll stick to the G64 white lightning, at least till they re-introduce the Redline for this case.

Phil L.

Igniters & launch controller can make a huge difference on this. Especially if you have marginal amperage for a single FFJR (e.g. slow ignition), going to two in parallel can cause fairly significant variation.
 
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