Straight Meal D for endburner?

[skid68]

So I'm working on a couple of dola's and have a couple questions. I made the drivers for this dola using this forumla I read on skylighter:

 

Silver Titanium

Meal D

9

Potassium Nitrate

44

Sulfur

9

Charcoal

8

Titanium

30

 

I mistakingly mis read an article somewhere on there thinking this was a good silver spark comp for endburner rockets, but it is meant for gerbs, and wheel drivers. While the rockets didn't go anywhere, at least not higher than 10 feet. When I used four drivers for the 12" dola seen below. It did go up, slowly, but it did go up. Each driver actually had burn through at the apex, and it continued to burn all the way to the ground.

http://www.youtube.com/watch?v=R43k9sr3H4c

So I know I need hotter fuel for my next set of drivers. I have commercial Meal D and was wondering if I can use that by itself with some titanium added for the sparks. When I was talking to Steve Majdali about dolas down at the Winter Blast I swear he told me I could use straight Meal D for the drivers if I didn't want/can't mill my own BP, but I can't be sure. Can you guys help me out here? Thanks.[

[nater]

Sure can. End burners need fast powder. Commercial meal is expensive, but it will work if you can't mill your own.

[Arthur]

Actually that was an impressive girandola. You WANT it to hang there not launch to thousands of feet. Maybe look at the tube structure, when tubes burn through they waste lot of power.

 

I'd rather see a girandola spin at 100 feet than go up like a rocket and be lost in space, and then have to land somewhere.

[skid68]

Thanks guys, that's what I wanted to hear.

 

Firebreather, I completely agree slow and steady looks great. But I want to put headers on the ones I'm building now. That one in the video could barely carry it's own weight, so I need more power.

[Arthur]

With success like you have, I'd be tempted to tweak that mix.. For example Your "Gyro Silver Ti" could have 12 parts of mealD rather than the standard 9, or even make a couple of drivers with 15parts meal D with the header that you want, the others as in this test (That would make the rise swifter then the hover and header, then a few would stay on to steady the descent.

 

You are (IMO) TOO CLOSE to make big changes

[skid68]

With success like you have, I'd be tempted to tweak that mix.. For example Your "Gyro Silver Ti" could have 12 parts of mealD rather than the standard 9, or even make a couple of drivers with 15parts meal D with the header that you want, the others as in this test (That would make the rise swifter then the hover and header, then a few would stay on to steady the descent.

 

You are (IMO) TOO CLOSE to make big changes

 

Hmmm, now you have me thinking. I could use a slower batch for the dola drivers and maybe go with the Meal d for the rocket drivers.

This video is the same comp, but using a more coarse Ti. This is about what they all did.

http://www.youtube.com/watch?v=wJYcichhmb0&feature=youtu.be

[kpknd]

My endburn fuel is nothing more than full trength BP with less sulfer, the same fuel I use for cored rockets. I mill mine for one hour (1 lb), add 5gm motor oil and mill an additional 15 min.

 

The 3/8" I.D. tube uses a 1/16" nozzel, 1/2" tube 5/64" nozzel, 5/8" tube 3/32" nozzel. I drill the nozzel by hand with the bit, go into the fuel about 1/8" to 1/4" to make a short core to give it a little kick. I usualy carve a conical opening in the clay with an exacto knife after drilling.

 

Do not make the fuel length in the tube too long or you can get burn through. A couple of inches will give you a long duration of several seconds or more.

Edited August 19, 2013 by kpknd

[skid68]

So I tested one of these Meal D plus Ti motors tonight..... BOOM! The tube blew into pieces. I'm using the Ben Smith Super BP Endburner 1# tooling. But maybe the nozzle is just too small? The fuel was granulated as much as commercial Meal D can be, and rammed on concrete using a 3lb dead blow hammer, so I highly doubt consolidation was the problem. What are your thoughts? I want fast endburners for rockets by them selves, but I may need to tone this down some. What is the best way? 10% Airfloat?

[Bobosan]

Here is an end burner flight test of 2oz rocket using milled BP with 3% dextrin straight out of the mil jar. Charcoal is paulownia, no metals. Nozzle formed with Skylighter 2oz tooling.

 

http://youtu.be/1dNfsN06els

[Mumbles]

It isn't really possible for BP to be too hot for end burners. If you do want to tone down the mix, or add a little more tail, I'd start closer to 5%.

 

You might also want to leave out any binders, and try smaller increments to see if that fixes the issues. You should be using increments that will add fuel no higher than 1x ID. I'd prefer to be closer to 1/2 or 3/4 ID in height.

[nater]

How big were your increments? I usually use a rounded teaspoon for 3/4" motors. That might be small compared to some, but 4 different rocket masters have stressed the importance of pressing small, equal increments to me. Their results speak for themselves. I only copy what they have taught me.

 

Also from my experience with ramming vs. pressing, pressing each increment to high pressures helps prevent CATOs. You might find the motor that CATOs when rammed will fly beautifully when pressed.

Edited September 2, 2013 by nater

[skid68]

It isn't really possible for BP to be too hot for end burners. If you do want to tone down the mix, or add a little more tail, I'd start closer to 5%.

 

You might also want to leave out any binders, and try smaller increments to see if that fixes the issues. You should be using increments that will add fuel no higher than 1x ID. I'd prefer to be closer to 1/2 or 3/4 ID in height.

 

That's what I've been told, but dang if it didn't have a hell of an amount of thrust. Nearly 600 grams before it blew, and killed my scale.

I'll go with 5% thanks. Do you think the dextrin might be adding to the problem then? I try and add no more than 3/4 at a time when ramming, but I will cut it back even more on the next run. Thanks.

[skid68]

Hmm, after examining the tube. Maybe I rammed the nozzle too much and weakend the tube? I used nept from hobby horse, so I know they are strong. Maybe it was just the easiest way out for the pressure. Thoughts?

http://imageshack.us/a/img62/8048/0k8g.jpg

http://imageshack.us/a/img543/5505/do6a.jpg

Edited September 2, 2013 by skid68

[skid68]

So I measured the tooling, and the spindle is just a smidge over 1/8" Maybe 5/32". Maybe 3/16" is a better size?

[Col]

You may have fractured the tube wall, you may not see it on the outside but it only takes a hairline crack to weaken the tube. An nept should cope with a lot more than 600g thrust. Edited September 2, 2013 by Col

[skid68]

You may have fractured the tube wall, you may not see it on the outside but it only takes a hairline crack to weaken the tube. An nept should cope with a lot more than 600g thrust.

 

Yeah I just don't know what happened. I tried the same mix with a 3/16" nozzle, but this time the nozzle blew out. I didn't ram the nozzle as hard as usual to try and avoid damaging the tube. :/

I went ahead and added 5% Air Float charcoal to slow the mix down a bit. Here is a test I did today with only 1 teaspoon of comp rammed each time to help consolidate, 5 total and no header. Maybe cut the airfloat down to 3% next time?

http://www.youtube.com/watch?v=8laMgRjeiXk&feature=youtu.be

[Col]

That looked alright.

A tube support might be worth a go, it allows you to use more force without worrying too much about damaging the tube. I use them for everything

Edited September 3, 2013 by Col

[FlaMtnBkr]

So explain your fuel a bit more. You are making 1# (0.75" ID) motors and using commercial Meal D powder? You are adding dextrine, titanium, and now airfloat charcoal? Why the dextrine? Are you wetting the powder at all?

 

I use homemade BP that is significantly hotter than commercial powder and get good performing motors. One of the biggest factors is getting good consolidation. How many blows with the dead blow hammer are you giving each increment? You need to put some effort into it. 10 or 12 solid whacks (hard but not real hard) and only enough powder to make a 1/2 to 3/4 ID increment once compacted. I wouldn't add anything to the Meal D until you get them flying. There is no need for the dextrine as the powder isn't wet and not being bound by it. The titanium can add some sparks but it can also seperate from the BP in your container, same with the airfloat some.

 

Is there anything else you are doing different? For an endburner you should be able to use the hottest BP around without a CATO. Since it is Meal D and there are very small grains you just need to make sure they are getting compacted into a good solid grain. Let us know everything you are doing if it is much different than the above. Good luck.

[skid68]

That looked alright.

A tube support might be worth a go, it allows you to use more force without worrying too much about damaging the tube. I use them for everything

 

Yeah, it could be faster. I think I'm going to get a tube support soon.

 

So explain your fuel a bit more. You are making 1# (0.75" ID) motors and using commercial Meal D powder? You are adding dextrine, titanium, and now airfloat charcoal? Why the dextrine? Are you wetting the powder at all?

 

I use homemade BP that is significantly hotter than commercial powder and get good perfor

ming motors. One of the biggest factors is getting good consolidation. How many blows with the dead blow hammer are you giving each increment? You need to put some effort into it. 10 or 12 solid whacks (hard but not real hard) and only enough powder to make a 1/2 to 3/4 ID increment once compacted. I wouldn't add anything to the Meal D until you get them flying. There is no need for the dextrine as the powder isn't wet and not being bound by it. The titanium can add some sparks but it can also seperate from the BP in your container, same with the airfloat some.

 

Is there anything else you are doing different? For an endburner you should be able to use the hottest BP around without a CATO. Since it is Meal D and there are very small grains you just need to make sure they are getting compacted into a good solid grain. Let us know everything you are doing if it is much different than the above. Good luck.

 

FlaMtnBkr, yes 1# .75" ID using Meal D. The dextrin was to bind it as I tried to granulate lightly with alcohol. But with 27% Ti, and Meal, it doesn't granulate nearly at all.

I was using bigger increments, but have since cut them back. I think the problem is too much Ti, and not enough compaction using the meal.

I contacted Ben Smith about the problem asking about the spindle diameter since I picked them up from him. He told me to just use a good ole 75/15/10 with 3% vaseline instead of trying to ram the meal, since it is very hard to consolidate properly without a press, and cut the Ti back to 10%. So I made a batch without Ti and I'm going to test tomorrow. Since I killed my scale and can't check the thrust, what is an average header weight you can put on a 1# endburner if there is such a thing as an average.

Edited September 7, 2013 by skid68

[skid68]

Well that didn't work. The 75/15/10 with 1% Mineral oil I made is crap. Used commercial Airfloat, hammer milled Potassium Nitrate also blended in a coffee grinder, and sulfur powder. The fuel is waaaay slow? Am I missing something here?

[Mumbles]

You are supposed to mill the mixture to make hot BP for the fuel. Unmilled just doesn't work as well. Using a hot charcoal will also help.

[skid68]

You are supposed to mill the mixture to make hot BP for the fuel. Unmilled just doesn't work as well. Using a hot charcoal will also help.

 

I know I need to mill it to get it really hot, but I don't have one yet.

I told Ben I didn't have a mill yet, and he said that screening the baby powder fine chems together would make a servicable fuel. But my fuel is painfully too slow.

Not sure what the airfloat I have is made from. It is from Pyro Chem Source.

Edited September 8, 2013 by skid68

[Bobosan]

I know I need to mill it to get it really hot, but I don't have one yet.

I told Ben I didn't have a mill yet, and he said that screening the baby powder fine chems together would make a servicable fuel. But my fuel is painfully too slow.

Not sure what the airfloat I have is made from. It is from Pyro Chem Source.

 

Look for some willow, balsa or paulownia charcoal and screen together several times without any binders or oils. Anything added to a basic 75/15/10 screened only BP mix is going to slow it down even further until you get your mill.

Edited September 8, 2013 by Bobosan

[nater]

Commercial airfloat only makes average strength BP. You did not mention milling. You won't get fast BP without a ball mill. Oil also slows the BP down. Are you pressing these with a sleeve yet?

 

Edit: interesting delay there. The replys weren't there when I typed my response. In addition, what are your expectations with an end burner? With core burning tooling, you can make great motors with screen mixed BP. End burners have such a small amount of fuel burning at once that they need the hottest fuels you can get. Even then they don't have the lifting power that core burners do. What they lack in power they make up with long burn time.

Edited September 8, 2013 by nater

[skid68]

Look for some willow, balsa or paulownia charcoal and screen together several times without any binders or oils. Anything added to a basic 75/15/10 screened only BP mix is going to slow it down even further until you get your mill.

Duely noted, just going off what Ben told me. Aside from the usual suppliers, where can you pickup willow and paulowinia?

 

Commercial airfloat only makes average strength BP. You did not mention milling. You won't get fast BP without a ball mill. Oil also slows the BP down. Are you pressing these with a sleeve yet?

 

Edit: interesting delay there. The replys weren't there when I typed my response. In addition, what are your expectations with an end burner? With core burning tooling, you can make great motors with screen mixed BP. End burners have such a small amount of fuel burning at once that they need the hottest fuels you can get. Even then they don't have the lifting power that core burners do. What they lack in power they make up with long burn time.

 

I don't have a press, and I picked up a HF mill today. I was just doing what Ben had told me to do to get some respectable fuel without a mill. I even cut the oil back to only 1% instead of 3.

My expectations are to make a rocket that will work on it's own with a small payload using my own BP, but mainly for use on Girandolas. I would like to get away from using the commercial Meal since it can be expensive. This is what I don't want from my rockets.

This was today with the screened mix.

http://www.youtube.com/watch?v=5bYw9FRsRn4&feature=youtu.be

Edited September 8, 2013 by skid68