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D10 casing heat and ejection charge

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fulldec

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I've only flown this motor a couple of times a few years ago. It was in a BT-20 model. The motor blistered the paint on the rocket around the motor.

I flew a D10-3 yesterday (new pack) and the ejection charge burned the BT20 stuffer tube clean in half in front of the motor. The casing itself was solidly stuck in the BT20. I had to use pliers to get it out of the remains of the model. In this case, the BT20 was not blistered where the motor was located, just burnt to a crisp in front of the motor. The delay also seemed a lot longer than 3 seconds.

So my question is, have others had these kind of issues using this motor in a minimum diameter model? Maybe I am missing something. If this is a general problem with this motor, I don't see how people can use it.

Thanks,

Don
 

shreadvector

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Google "the hibachi effect" - there is an excellent article on it from Apogee.
 

fulldec

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Fred,

That looks to be exactly what is going on. The Apogee article is very good and searching with "the hibachi effect" has led to some good other discussions and actions that can be taken.

Thanks,

Don
 

mikec

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FWIW, I've flown the D10-5 a half dozen times without issues; as the article says this is more likely to be a problem with a shorter delay.
 

BEC

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I have a Nova Payloader (BT-50-sized model) that has flown on D10-5s and D10-7s and it, too, has bubbled paint above the motor mount from this effect. I finally retired it after 75 flights because it's getting really soft in that area. Of those 75 flights perhaps a handful were on D10s.
 

cerving

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Personally, I'm impressed that you managed to get the BT20 rocket back... a D10 or D21 is usually a one-way flight: Up.
 

shreadvector

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I keep a supply of D10 and D21 motors on hand for newbies who ask me for the most powerful motor they can put in their model.


They are often fathers of cub scouts.

They have bought one and put it in anything from a High Flyer to a Make & Take. They all went stupidly high and they all recovered them (to their amazement).


Personally, I'm impressed that you managed to get the BT20 rocket back... a D10 or D21 is usually a one-way flight: Up.
 

Daddyisabar

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When you are flying a SU D10 or 21 you better know what you are doing. Awesome 18mm composite fun. The ejection charge goes off followed by still burning delay grain and maybe some propellant. Lots of hot gas and the wimpy, narrow paper tube can't take it. So you just have to reinforce a bit above the motor tube when you build it (several ways to do this). But what if you already built it stock and are bored flying your Alien 8 on C6 motors? The darn reloads don't fit because the ejection cap won't clear the engine hook and or thick motor block. Just pop in and SU and feel the burn! Take the damage like a man.

How about when you get tired of flying your Kit bashed P40E Spaceship One on the C6? Just pop in an SU and say "Hey, hold my beer and watch this." With a tight pack on the chute/wadding you can even get a bit of melt on the big plastic tail cone. Scrape out all the burned wadding, inspect the burn holes in your chute, smell the AP, curse Aerotech and tell yourself to build 'em right from the start.

Build them from the start to take the SU's, or ditch the engine hook and motor block for the reloads. It is high power composite time now, time for Vitalis. No more wimpy black powder. no more wimpy kid's stuff!

Vitalis.jpg
 
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