Performance Rockets

[DIYMark]

Recently I've been trying to achive "Estes" power from my end burners and its near impossible.

 

Ive made all sorts of different blackpowder ratios - you name it...

 

Lift - 74/14/12

 

"Ideal" - 75/14/12

 

Standard - 75/15/10

 

End Burner - 60/10/10

 

Estes - 72/14/14

 

All were ballmillied in 100 gram batches for 10 hours (In an efficent ball mill)

 

All but the Estes and end burner powders burnt fast. Once a spark hit a 5 gram pile it would deflagrate insantly with a loud "boof", while the 60/10/10 and "Estes" ratio burnt relativly slow with a more progressive burn.

 

So far Ive been making 1/2" ID rockets and If I use an Estes nozzle size (Their half inch rockets have a 3mm nozzle) I achive around 180 grams thrust...while an Estes rocket achives 420 grams!

 

WTF

 

Using all these different powders the best thrust I could achived was 250 grams (with a 2.4mm nozzle) which is nowhere near Estes power and Im using a smaller nozzle! After witnessing this Ive started to wonder, just how does Estes attain such power? At first I thought it was due to their motors having a low density propellant grain to increase burn rate. But according to their data a standard C6 motor has 12.5 grams of propellant and from my tests to fit that in a 1/2" by 2.75" long rocket case is only possible under extreme pressure while packing. So low desnity is out of the question.

 

Secondly I thought they could have used a slight conical core in the grain, causing the propellant to burn not like a typical end burner but more of a cone which would increase the Kn of the motor. However after testing and inspection of Estes motors they are just typical end burners.

 

So does anybody here know HOW Estes can achive so much thrust from their motors with such Low Kn ratios? Does anyone know what kind of charcoal they use?

 

PS - All my BP for this was made from eucalyptus charcoal. I made a fire and put it out when the wood was sufficiently "charcoalised". Once this was done I dried the charcoal. With such "bad" charcoal my lift powder burnt very similar to this Click So this had me thinking...if powder that fast made poor end burners what else can I do? Maybe use a different charcoal other than eucalyptus? Perhaps one that is more Brisant? Because my powder is almost the same as the one in the video and Im sure that does deflagrate fast enough for endburners. Also I plan to buy a pack of Estes motors - Ill fly one, static test the other and then reverse engineer the last one to work out the density of propellant, nozzle size/shape and burning speed of the propellant.

Edited September 22, 2008 by DIYMark

[Mumbles]

First of all, bristant refers to shattering power, not exactly applicable here.

 

Secondly speed is not the only contributing factor here. Gas production plays a significant role. I believe Estes rockets have their black powder specially manufactured for them, likely by Goex. Goex is reported to use Maple primarily, but I've heard of others too.

 

Now, with this being said, I suspect it's your loading pressure. Estes rockets are known to use New England Paper tubes, an extremely high quality very hard and very strong tube. I've heard loading pressures of well over 10,000psi reported before. I'd like to hear how you were making the engines though, as it may help to trouble shoot.

[tentacles]

For the given thrust with the Estes motors, do they burn proportionally shorter duration to the motors you made with 180 grams of thrust?

 

You might try balsa, tree-of-heaven, or paulownia charcoal for a faster burn. Paulownia or balsa might either one give better thrust, as they are known for copious gas production. Granted, they may be too hot to use in a rocket, even an endburner.

[FREAKYDUTCHMEN]

What's your goal? making nice performing engines for lifting big headers or is mean for just rockets?

[PyroMedia]

Try a star-core?

[FrankRizzo]

It's the charcoal, guaranteed. Eucalyptus makes poor charcoal for anything other than spark production. Even switching to a commercial BBQ lump charcoal should give you a considerable increase in power.

[DIYMark]

Oh dont tell me that

 

Living in Aus means that the only wood around here is eucalyptus! lol

 

I will buy some balsa for charcoal purposes in the near future and see how that fares, also I can buy willow charcoal used here for art but its like $10 for a few stick which weighs around 10 grams! BUT put it this way, 10 grams of charcoal will make me ~70 grams of BP which is enough for ~6 rocket motors (C6 size). Now this is great considering for me to buy a 3 pack of Estes C6 motors here cost me $20! But still its a rip - perhaps I can get it in bulk?

 

Also I can give that tree that I mentioned in the willow alternatives thread a ago. It made really fast BP; the mill dust after 4 hours of milling would give a good thud noise from only lighthing a teaspoon of it. So, what left for me to try now is to make some more end burners using Balsa, Williow and that tree which I am yet to find a name for. Ill make 3 identical end burners and see which one has the most thrust (Ie best propellant in it). Then I can focus on optimizing it for max thrust and see where that leaves me - If i get near Estes power im happy, but if I dont make any improvements Ill have to look for a new charcoal type.

 

@ Mumbles

Engines were rammed using a 2.2lb steel mallet, my own homemade tubes and my own tooling. The tooling was tooling used was missing the "nozzle" section (diverging cone was left) so I could drill the nozzle to the exact size I needed. I packed them In tiny increments (~0.5 ID tall increments once compacted) and I used fairly big blows from the hammer - untill the current increment wouldnt compress any more basically.

 

@ tenacles

Thrust was proportionaly longer. This indicated that my working pressure was too low. Once a smaller nozzle was used the burn time would decrease but thrust wouldn't increase as it should. Instead I was kind of reaching the limit of my propellant (due to bad charcoal).

 

@ FREAKYDUTCHMEN

Im after making performance rockets engine mainly for the challenge of it but also to hopefully use them in model rockets.

 

@ Pyro Media

I want to stick to end burners for simplicity - although it is starting to get more difficult now lol.

 

NOTE: This was written at college and I had posting issues, so I saved the post and am posting it now. However since then, Ive made balsa charcoal and my ball mill is currently charged with willow charcoal BP (Estes ratio). Using "Estes" ratio the burn rate is a bit slower then 75:15:10 yet after 2 hours of milling the mill dust makes a nice thud once lit and the gas production is vastly better than eucalyptus! Also the willow was "English Willow" that was brought from an art supply shop however I heard cricket bats are made from this stuff too (the expensive ones) So It looks like Ill be burning cricket bats for charcoal hahaha - not.

 

In addition the mysterious trees that around my house is very similar to willow charcoal, velvety smooth if you use it to write with and its flexible, but will snap cleanly once flexed to far. Also the mystery tree is a bit like willow - hard wood and somewhat flexible plus fast growing; and finally the mystery tree has the same performance of willow BP - mill dust will burn with a nice thud and polverone is explosively fast.

Edited September 23, 2008 by DIYMark

[Richtee]

Oh dont tell me that

 

Living in Aus means that the only wood around here is eucalyptus! lol

 

Seriously... try newspaper charcoal. Pack a small can full and cover with foil. Roast it in a fire, and ball mill it.

http://www.apcforum.net/forums/index.php?s...ost&p=37280

[DIYMark]

Thanks Richee Ive seems to forgot all about newspaper! Ill give it a twirl next time I make charcoal.

 

"But the charcoal type/processing and loading pressure has to be the biggest contributors, IMHO."

 

And thats what I experienced today lol. "Coffee Grinder" grade BP (grind each ingredient, screen together) made with my "English Willow" burns like nice core burner mix where as the same grade BP with Eucalyptus burns like thermite and leaves KCO3 blobs everywhere! So willow is clearly more reactive (who woulda thought! lol).

 

Also I took out my willow BP from the mill and man its fast! A Teaspoon full lit make a huge whump and the spoon actually get thrusted down too (yes I held it lol). It burns like Estes propellant if you hollow out a Estes motor (nice bang) - so It looks like I'm getting there. But heres one problem. Willow cots me $10 for 10 grams and the Balsa cost me $13.50 for 42 grams of charcoal. And IIRC balsa is faster than willow yet its cheaper per gram (in my case) than willow. So if Balsa is in fact better - that's good, but I'm yet to make BP from my Balsa charcoal (will tonight).

 

Lastly that mystery tree that's on our land (Ive searched to net for about 2 hours and still don't have a name for it!) makes BP VERY similar to willow, the only difference it that once burnt the noise has a sharper "crack" to it than willows "whump". But Ill have to test both in a motor before can tell which is better.

 

So tonight Ill have tested an end burner with willow BP and Ill have the mill running with balsa BP - Ill keep you all in formed.

 

My todo list -

Make/test Willow BP End burner.

Charge mill with Balsa BP.

Make/Test Balsa BP End burner.

Wait for the "Mystery tree" branches I cut to dry.

Make newpaper and "Mystery Tree" charcoal.

Then make 2 end burners from the above charcoals.

[tentacles]

Why don't you contact these guys (http://www.paulowniatrees.com.au/) and see if you can't buy a few pruned branch pieces from them to make some bitchin' fast charcoal from?

[DIYMark]

I'm not too keen on ordering charcoal, as it is, going and buying it is bad enough - Ive got some spots in mind for where to get willow (weeping and black). However, does anyone know out of the three willows (English, Black and weeping) which is most reactive?

 

Also I granulated my willow BP and made a 1/2" end burner. And it worked! I drilled the nozzle just untill it reached BP (no core at all) so once ignited it has constant thrust. Estes use a small core for a surge of thrust to get rockets up to speed so fins work before the rocket leaves the launch rod. I just wanted to test for average thrust.

 

The motor made wit ha 3mm nozzle (as per Estes specs) had 500g trust then it slowly dropped to 480g. The motor with a 2.8mm nozzle had 550g thrust and then slowly dropped to 430g. According to Estes and various sources the average C6 thrust is 470grams; average meaning the "flat" part of the thrust graph. So willow BP in a rocket motor built to Estes dimensions is equal to an Estes motor. Tomorrow Ill try the same motors (3mm and 2.8mm nozzle) using Balsa BP and see whats the difference in performance - my guess is that Balsa BP will have more thrust and its also cheaper for me to buy than willow (but hopefully ill find a willow tree!) Futhermore Balsa from the model shop (instead of the hardware) will be about twice as cheap - however, if charcoal cost any money; its too expensive seeing as all I need to do it find the right tree.

 

Tomorrow Ill have static test info about Balsa BP.

[tentacles]

Mark, you should really look into paulownia. From what I understand, there is quite a lot of it grown down under, and it makes GREAT BP. Seriously hot endburners, you might even have to tone it down.

[FREAKYDUTCHMEN]

My weeping willow BP is extremely fast, I can't see the difference with my paulownia BP. Well visual there is a difference the paulownia BP is more greyish instead of the more black looking willow BP.

 

I've read that black willow burns faster than weeping willow, I haven't got black willow so I don't know.

[Miech]

Burning speed is not really of interest in rocketry, gas output is way more important (or actually excreted mass per unit of time). Burning speed is more something important in lifting small shells and breaking them.

 

I've made my best rockets with BBQ charcoal, milled as dry as possible for about 8 hours in a rock tumbler. I added 5% dextrin before milling because I planned to make pulverone with it. Specifications as followed:

 

3/4" x 3" PVC tube as casing

3/4" Nozzle made from kitty litter

1/5" Venturi, no core

2/4" Top end plug, also kitty litter.

1/5" Hole to payload

 

I just rammed the nozzle and filled the whole tube with meal, than rammed it. Then I filled it again with meal and compacted it again. Then I rammed the top end plug, and drilled the venturi and hole to the payload. The latter was filled with hand pressed meal to serve as short delay. These rockets produced about 400 grams of thrust and sometimes reached a 500 meters altitude.

Edited September 24, 2008 by Miech

[FREAKYDUTCHMEN]

400 grams trust says nothing, you did a static test to find that out?

And who says BBQ charcoal gives more gas output?

[DIYMark]

About 400 grams thrust from a 19mm ID rocket is poor. An 19mm (3/4") ID tube has got ~2.24 times the burning surface than that of a 12.7 (1/2") tube yet you got less thrust than a 1/2" end burner made with good BP - which has ~500grams thrust. This means if I used my propellant in a 19mm case I would have got 1120 grams thrust. An Estes E9 has an 18mm ID and they have ~980 grams thrust so 1.12Kg from 19mm is pretty darn spot on for a well made end burner.

 

Also I was looking at Ultrabuff's Y.Tube channel and I saw his Willow/balsa BP. Thats exactly how my BP burnt - not exactly because I tried 2 batches, willow and balsa, not both together but his BP burnt like it was between the two charcoals. My balsa BP I finished making yesterday burns like willow, same noise and what seems to be gas production but its the tinyest bit faster than willow. This is good if I end up buying Balsa for BP as balsa is cheaper than art supply charcoal - but I still am yet to go for a drive to search for willow (I know the perfect place - its along a windy road that goes through the bush following a stream and its practically never dry there - sounds like where a willow would want to be).

 

Also Ill look into paulowina; im not sure if it would be where I live but Ill need to research.

 

My Balsa end burners both had massive case erosion. Within a half of a second they had holes in the side! However, the thrust I managed to record was 520 grams average for 3mm (Estes nozzle size) and 580 grams average for 2.8mm. What Ill have to do now is machine up some tooling (Ill use a 3mm nozzle) and make a proper rammer with a converging cone to stop case erosion.

 

Also on the way home I found a willow tree - pity its in some ones yard!

Edited September 25, 2008 by DIYMark

[Yankie]

If any Australians want to buy Pawlonia charcoal I sell it for 150g for $30, the high price is due to the small amount I have left (and I cant make more until fireban is over)

Also you can grow the pawlonia from root cuttings, If anyone wants to buy some I will be more than happy to dig up one of my trees.

[Mumbles]

I would really stop using you tube videos to judge BP. As others have said there is more than just speed. Also, the videos on you tube are usually not the greatest quality or frame rate, so it may be decieving.