Quantcast

Trouble Lighting Single Use AT G78 Mohave Green.

The Rocketry Forum

Help Support The Rocketry Forum:

jeff2space

Well-Known Member
Joined
Nov 26, 2011
Messages
580
Reaction score
7
Location
Waterford, WI
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?
 

markkoelsch

Well-Known Member
Joined
Mar 18, 2009
Messages
4,364
Reaction score
148
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.
 

jeff2space

Well-Known Member
Joined
Nov 26, 2011
Messages
580
Reaction score
7
Location
Waterford, WI
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.
 

DavidMcCann

Well-Known Member
Joined
May 15, 2016
Messages
2,656
Reaction score
166
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.
 

Coop

Well-Known Member
Joined
Dec 15, 2011
Messages
1,768
Reaction score
3
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
 

JJSR

Well-Known Member
Joined
Dec 12, 2012
Messages
777
Reaction score
65
+1 on the magnelite ignitors
 

DavidMcCann

Well-Known Member
Joined
May 15, 2016
Messages
2,656
Reaction score
166
It would probably help if I knew what speed this was at....but you get the idea.....

[youtube]4IbKegUYZX8[/youtube]
 

Tonimus

Well-Known Member
Joined
Jul 9, 2014
Messages
1,511
Reaction score
4
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.
 

ParrytheWind

Well-Known Member
Joined
Jun 15, 2013
Messages
143
Reaction score
0
"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.
 

DavidMcCann

Well-Known Member
Joined
May 15, 2016
Messages
2,656
Reaction score
166
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.
 

watermelonman

Well-Known Member
Joined
Sep 22, 2014
Messages
2,597
Reaction score
8
Hah, those have lit much easier than any white lightning for me!
 

BDB

Absent Minded Professor
Joined
Aug 22, 2015
Messages
2,184
Reaction score
417
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.
 

markkoelsch

Well-Known Member
Joined
Mar 18, 2009
Messages
4,364
Reaction score
148
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.
 

AlfaBrewer

Well-Known Member
Joined
Mar 18, 2011
Messages
866
Reaction score
8
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.
 

cerving

Owner, Eggtimer Rocketry
TRF Sponsor
TRF Supporter
Joined
Feb 3, 2012
Messages
4,162
Reaction score
1,435
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.
 

markkoelsch

Well-Known Member
Joined
Mar 18, 2009
Messages
4,364
Reaction score
148
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.
 

Bat-mite

Rocketeer in MD
Joined
Dec 5, 2013
Messages
10,986
Reaction score
1,738
Location
Maryland
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.
 

Tonimus

Well-Known Member
Joined
Jul 9, 2014
Messages
1,511
Reaction score
4
Now here's a question: how much is a "sliver" of Blue Thunder for a SU 29mm, like an Econojet?
 

Donaldsrockets

Well-Known Member
Joined
Jan 18, 2009
Messages
3,562
Reaction score
1
Location
Fort Myers, FL
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.
 

markkoelsch

Well-Known Member
Joined
Mar 18, 2009
Messages
4,364
Reaction score
148
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.
 

kramer714

Well-Known Member
Joined
Jan 20, 2009
Messages
697
Reaction score
10
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.
 

watermelonman

Well-Known Member
Joined
Sep 22, 2014
Messages
2,597
Reaction score
8
5mm by half mil? That is about what I use with my 20 year old G64s and F40s.
 

DavidMcCann

Well-Known Member
Joined
May 15, 2016
Messages
2,656
Reaction score
166
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.
 

rstaff3

Oddroc-eteer
Joined
Jan 18, 2009
Messages
11,759
Reaction score
14
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.
 

cavecentral

Well-Known Member
Joined
Jul 1, 2011
Messages
3,129
Reaction score
25
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.
 

cavecentral

Well-Known Member
Joined
Jul 1, 2011
Messages
3,129
Reaction score
25
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.
 

Maxitout

Well-Known Member
Joined
Oct 25, 2011
Messages
398
Reaction score
14
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.
 

dhbarr

Amateur Professional
Joined
Jan 30, 2016
Messages
6,985
Reaction score
1,436
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.
 
Top