Chuff?

So I had a AT E20-4W failure and I contacted AeroTech with this:

I recently purchased a 2 pack of your E20-4W engines and while one of them worked beautifully, the other failed. It ignited and gave a split second of thrust and then quit. It didn't even get off the launch pad. The failed motor is serial number 100632 (see attached). How do we work out a replacement?

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And their response was this:

Hi David,

what you described was a chuff, all you need to do is take a small wire and slightly scuff up the area where you placed the igniter the first time and insert another igniter and launch.

please provide me with a good shipping address and I will send you some replacement igniters ....K

Karl Baumann
Warranty & Tech Support
RCS/Aerotech Inc.

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Anyone have any experience with this?

Yes,

and what he says works.

Chuffing is fairly common with the harder to ignite propellants such as Blackjack and White Lightning.

It can actually be quite amusing at times when the motor chuffs for 5 or 6 times before coming up to thrust. Of course, its much less amusing when it YOUR motor in YOUR rocket.

The trick described does work. You're just exposing some fresh propellant.

Here is RocketJunkie's "Chug Chug" video from the Freedom Launch a week ago.

https://www.youtube.com/watch?v=WSzx-xlBlwY&feature=relmfu

In his case, his chuffed multiple times before it fully ignited. In your case it chuffed and went out. You hear somebody at the end of the video say "old motor". It is common for older motors or poorly stored motors to get oxidation on the propellant, like John and Chuck have described above.

The motor is still completely usable - you just need to use another igniter, preferably after scraping the propellant surface a bit to get rid of the oxidized coating. As everyone said above, it's not terribly uncommon, and the response is accurate.

Chuffing is the Father of the Land Shark. If you get a few good chuffs on a light rocket, its occasionally enough to lift it off the launch rod/rail. Then, when its laying sideways on the ground, the motor decides to come up to full pressure. Excitement ensues.......

My son's Initiator experienced some good chuffing earlier in the year on a blackjack load. https://www.youtube.com/watch?v=RiyfDDAWgxA. It ended up going in the wrong direction after it finally decided to fly and is still hanging from the evil pine tree. I've had a few redlines chuff as well.

if some one were to do a compilation video of chuffs...the 'Locomotion' might make a suitable soundtrack .
rex

neond7 said:

Chuffing is the Father of the Land Shark. If you get a few good chuffs on a light rocket, its occasionally enough to lift it off the launch rod/rail. Then, when its laying sideways on the ground, the motor decides to come up to full pressure. Excitement ensues.......

My son's Initiator experienced some good chuffing earlier in the year on a blackjack load. https://www.youtube.com/watch?v=RiyfDDAWgxA. It ended up going in the wrong direction after it finally decided to fly and is still hanging from the evil pine tree. I've had a few redlines chuff as well.

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Were you at TTRA a couple months ago when somebody's rocket sat on the pad and chuffed over and over for at least a solid minute, maybe more like 90 seconds, then ignited and had a successful, though rather low, flight? That was quite something to see-- I was impressed it even got off the ground!

Wouldn't that destroy the case temper?

LW Bercini said:

Here is RocketJunkie's "Chug Chug" video from the Freedom Launch a week ago.

https://www.youtube.com/watch?v=WSzx-xlBlwY&feature=relmfu

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And that was the *third* igniter!

CarVac said:

Wouldn't that destroy the case temper?

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That depends - just chuffing wouldn't really heat up the case very much, so I would think it would be fine. On the other hand, I've seen a motor do a slow burn without enough thrust to leave the pad for several minutes, and that did indeed melt the case.

Cases usually are fine after a chuff. Even an extended chuff.

I have never seen one damaged by a chuff.

Yep happens all the time in fact you are lucky it didn't chuff chuff chuff and burn up your delay and eject your chute mid flight, longest zipper I have ever seen.


TA

One of the forgotten side effects of a chuffing motor is: Your delay can become quite a bit shorter. The rocket sits on the pad chuffing and the delay can shorten along with it. [it starts burning with the motor]

Your rocket finally takes off and only a few seconds into flight the ejection charge fires. [many times while the rocket is under full thrust or shortly after causing zippers or other forms of havoc]

Along with old motors being a cause, is not making sure the igniter is fully to the top. It can get caught on an edge between grains and you think it hit the top. When lit, the motor burns from the middle, not developing full pressure and sits there not moving, doing what.............. chuff....chuff.......chuff!

Rocketbuilder said:

Were you at TTRA a couple months ago when somebody's rocket sat on the pad and chuffed over and over for at least a solid minute, maybe more like 90 seconds, then ignited and had a successful, though rather low, flight? That was quite something to see-- I was impressed it even got off the ground!

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Missed that flight, although I might have been there and was busy getting ready for my L2 attempt. I was so nervous/excited it was hard to pay attention to much else. Although I do distinctly remember Mike's glider doing the CATO dance. And my wife got to see her first "surrender Dorothy". After she saw one zig zagging all over the sky, she was so happy she yelled out "That what one of those is!!!".

I'll be there this Saturday, we are even dragging a friend along. We couldn't make it to both days - are you launching? The weather looks ok, a chance of showers, but the wind is low.

For damaging the case, yes, it can....
it has to be bad tho... for small motors like an e20 or well lined motors like phenolic that AT uses probably not....

the reasons is that the ends next to the liner could be burning -and burning the liner. it is developing pressure between the grains and has increased burn rate, while the core is (not burning) then, when the motor kicks up and is in fire mode, theres areas there is no liner and the case is exposed....

never seen that on a commercial motor, but i have had that problem with EX motors.....



As far as the temper... any time you fly a graphite nozzle that is excellent at getting hot, heat soak can always ruin a temper!

neond7 said:

Missed that flight, although I might have been there and was busy getting ready for my L2 attempt. I was so nervous/excited it was hard to pay attention to much else. Although I do distinctly remember Mike's glider doing the CATO dance. And my wife got to see her first "surrender Dorothy". After she saw one zig zagging all over the sky, she was so happy she yelled out "That what one of those is!!!".

I'll be there this Saturday, we are even dragging a friend along. We couldn't make it to both days - are you launching? The weather looks ok, a chance of showers, but the wind is low.

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I'll be there on Saturday launching LPR and MPR. Nothing very big though; I've decided that if I'm going to do HPR, I'll wail until I'm 18 and don't have to worry about what I am/am not alowed to do with motors and such. BTW, I noticed you mentioned your son earlier; how old is he?
Sorry for the threadjack. :blush:

Just out of curiosity, has anyone ever seen or heard if a chuff that lit the delay, and caused the laundry to eject on the pad?

Rocketbuilder said:

Just out of curiosity, has anyone ever seen or heard if a chuff that lit the delay, and caused the laundry to eject on the pad?

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How 'bout this one...



Engine ignited, lifted 4 inches off the pad, plug uncoupled a bit early, read as a malfunction, engine shut down, dropped back onto the pad, flight electronics registered as an abort, blew the tower sep bolts and fired the escape tower simultaneously instead of firing the capsule to booster bolts and hauling the capsule off the booster, then the capsule electronics registered the abort and popped the parachute...

Hehehee...

Later! OL JR

Rocketbuilder said:

Just out of curiosity, has anyone ever seen or heard if a chuff that lit the delay, and caused the laundry to eject on the pad?

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It's happened occasionally - it always leads to some entertaining commentary from the LCO...

Rocketbuilder said:

Just out of curiosity, has anyone ever seen or heard if a chuff that lit the delay, and caused the laundry to eject on the pad?

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Yes...several times on old motors. Especially the redline. Motor chuffs so much, by time it builds pressure, not enough oomph left to get the rocket up and away. So it road flares on the pad till ejection. Very funny.

That was not a chuff.

https://www.youtube.com/watch?v=7O4V7JfeTSU

luke strawwalker said:

How 'bout this one...

View attachment 96988

Engine ignited, lifted 4 inches off the pad, plug uncoupled a bit early, read as a malfunction, engine shut down, dropped back onto the pad, flight electronics registered as an abort, blew the tower sep bolts and fired the escape tower simultaneously instead of firing the capsule to booster bolts and hauling the capsule off the booster, then the capsule electronics registered the abort and popped the parachute...

Hehehee...

Later! OL JR

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thobin said:

Yep happens all the time in fact you are lucky it didn't chuff chuff chuff and burn up your delay and eject your chute mid flight, longest zipper I have ever seen.

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I had one chuff, chuff, chuff ... for a while then the delay ignited while the rocket sat on the pad. A few seconds later, the ejection charge fired.

Video: https://www.payloadbay.com/video-7908.html

-- Roger

Rocketbuilder said:

Just out of curiosity, has anyone ever seen or heard if a chuff that lit the delay, and caused the laundry to eject on the pad?

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Yes. See my previous post.

-- Roger

shreadvector said:

That was not a chuff.

https://www.youtube.com/watch?v=7O4V7JfeTSU

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:eyeroll:

Geez... get a grip...

LOL Some people's children...

Later! OL JR

This is an interesting thread to me... the first time I experienced chuffing was with an RMS 100 G54... white lightning propellant. BUT my experience with the now defunct E15's was solid... (likewise with 24/40 E18's). I HAVE however had chuffs with E20's two out of three times. I've had F24's do it (after a string of three no chuffs... I got a 2/3 in the next batch). I am assuming (rightly or wrongly) it's me and not necessarily the motor. I would *assume* that if I got a good, active ignition, then chuffing would not occur. I would think that those in the know (like the manufacterer) might have some advice (no, I've blown too much money on casings to switch to those "other" motors now so forget it! Besides I don't care THAT much if it chuffs once or twice) as to ways to minimize it...