Ducted Ramjet that is meant to fly.

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Johansson
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Post by Johansson » Sun Sep 09, 2007 7:25 am

I have only set aside about $3000 for the project (...)
He he, most of the ramjet projects I´ve seen so far must have had a budget roof at $30...

kent
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termal test Cork

Post by kent » Tue Sep 11, 2007 6:52 am

Really? $ 30 :) i wish i could make anything that cheap.

I bought 4 types of cork

Cork 1: Pieces of cork glued together
Cork 2: Large almost continuous pieces of cork
Cork 3: Pressed pieses of cork
Cork 4: Rough large pieces of cork glued together

Testing methodology: å butane torch burning the surface while blowing high pressure air at the sample.

Results
Cork 1: the glue used was highly flammable it burned as if it had been soaked in gasoline. - failure
Cork 2: The piece separated into thin layers and the pressurized air blew some of them off. - failure
Cork 3: This worked well, i kept the flame on for over 3 minutes and after brushing off the foamy ash that formed on the surface it looked almost like new apart from a slightly darker color. - success
Cork 4: this blew apart before i even got the torch trained on it - failure

Cork 3 schould work now i have to test it in a pressurized combustion environment
Attachments
cork1.JPG
Cork 1
cork1.JPG (4.17 KiB) Viewed 6284 times
Cork2.JPG
Cork 2
Cork2.JPG (2.91 KiB) Viewed 6283 times
Cork3.JPG
Cork3
Cork3.JPG (4.83 KiB) Viewed 6286 times
cork4.JPG
Cork 4
cork4.JPG (14.22 KiB) Viewed 6288 times
burntcorktile.JPG
Burnt cork tile
burntcorktile.JPG (13.11 KiB) Viewed 6285 times

pezman
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Cork!

Post by pezman » Tue Sep 11, 2007 11:50 am

Kent,

Udda man! This thread may have actually solved a construction dilemma that I had -- I am installing a ceiling that is very thin and which needs to be insulated w/ foam. Foam needs a fire-retardant covering. Most people use wall-board, which I detest. Cork may just be the thing!

Not exactly a ram-jet, but ...

At any rate, thanks for helping my little project fly.

Zippiot
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Post by Zippiot » Tue Sep 11, 2007 5:33 pm

Oak and a few other woods will form a type of carbon coating when exposed to intense heat on one side, and this coating prevents further burning. I know it flakes off like graphite though, so wouldn't be a permanent fix but wood is cheap and easy to rebuild with!

Try slathering it with phenolic resin, the stuff is literally epoxy that can withstand high heat for short times. Once again 1 time use but coating each wooden piece with it should extend run times a bit.......

You can buy the resin from most pyrotechnic suppliers

http://www.plenco.com/phenolicresins.html
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kent
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Cork doesnt like pressure and oxidant

Post by kent » Wed Sep 12, 2007 9:38 am

pezman

The cork schould work for your construction, no problem, just make sure you get pressed cork not glued.

Zippot

Wood could work but phenolic resin seams to be a possible solution for my filament winding dilemma, it only needs to work for 3-5 minutes and if i understand correctly, these resins can easily handle that.

but it seams like its nasty stuff to work with, i will see if i can find a company that has experience working with this type of resin, so i don't kill myself by mixing chemicals i have no clue about :)

The cork didn't survive pressurized combustion next to oxidant, it burned up together with the fuel.

Back to the drawing board

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Post by Zippiot » Wed Sep 12, 2007 6:17 pm

Phenolic is kinda like Vinyl Ester resin, not so much regular epoxy. Small bit of hardener for big vat of resin, and the hardener is...wear gloves

But some companies made 50/50 Phenolics, I have seen them just haven't tried them.

The stuff [to the best of my memory] is ABLATIVE, so it flakes off in tiny tiny amounts when exposed to extreme heat as opposed to just melting. Retains much of its strength and shape for longer periods, I use it to make nozzles for my rockets!!
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Jim Berquist
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Post by Jim Berquist » Thu Sep 13, 2007 12:44 am

A lame Idea, But what about plain old muffler putty. Silicate based is good up to a few thousand degrees. Even the Epoxy type is quite good.
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kent
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No phenolic resin

Post by kent » Thu Sep 13, 2007 10:16 am

Phenolic resin, as i have learned, is dangerous stuff and difficult to manufacture so i have decided to stay clear of it.

I will go back to trying to manufacture with alumina, i have talked to a professor at the university that knows about these things and he has given me a recipe for manufacturing the body tube.

The key it seams is to cure the alumina slowly 4-5 days at least, this relieves internal tension. He described the process used by companies that manufactures alumina pipes.

I need to manufacture the curing oven, (my budget will probably go bust after manufacturing only the body tube) but i want this .... to work. I will have to save up some more money to continue the project later if i run out of money.

Anyway this is what i will have to do, inside an oven that is stable at 600C i will have to build a rotating steel tube with one end open.
It will have to spin fast and the molten alumina is poured directly into the spinning pipe. this then has to stay heated and spinning for 18-20 hours before i gradually cool it down to under 100C over several days.

So i have to build or buy temperature control, build the owen as well as the mechanics to spin the tube.

The problem is of course that i don't know how to do this but a couple of grad students that i met while talking to the professor have agreed to help me out.

I guess this project will run until the money runs out, then i will have to re-budget before continuing.

One day i will make this fly!

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Post by El-Kablooey » Thu Sep 13, 2007 5:52 pm

Why not just buy a used kiln? Look around on E-bay.

Have you thought about having this machined from a solid chunk of graphite?

kent
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Graphite?

Post by kent » Fri Sep 14, 2007 6:24 am

Good idea about the kiln, ebay here i come.

I think graphite is to brittle to survive the rigors of combustion.

heada
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graphite

Post by heada » Fri Sep 14, 2007 4:31 pm

Most higher power rocket motors use graphite as the nozzle. It isn't as brittle if held under compression and the thermal properties are just great! If a graphite nozzle gets dropped, its going to chip/crack/shatter, but if handled carefully, it would be fine.

-Aaron

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Post by Zippiot » Sun Sep 16, 2007 8:45 pm

The rockets nozzles are machined from a big chunk of graphite...thick stuff though still light weight.

I cant find the link but there is a spreadable clay insulator that protects from heat, spreads like butter. Might come in handy......
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Ghrey
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Re: Cutting alumina

Post by Ghrey » Tue Feb 26, 2008 8:19 am

Have you tried a liquid cooled diamond saw like used in a lapidary shop?

I can cut most things with mine with some practice.


Just a thought.
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Re: Ducted Ramjet that is meant to fly.

Post by airrocket » Sat Sep 13, 2008 11:29 pm

Fill it with a water based saline solution allowing for evaporation cooling through small holes in the inlet spike. Providing it is hollow or drilled out interior.
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thecheat
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Re: Ducted Ramjet that is meant to fly.

Post by thecheat » Tue Sep 30, 2008 5:54 pm

hmm... is there any chance you could try cutting it while it's still hot and a bit more malleable? I don't know much about such things, but, I would think that holding a blow torch to the area (if that doesn't crack it) would allow a little more leniency when you try cutting it with the laser. Maybe even an acetylene torch to pre heat it before cutting.

Also, when you tried to coat the steel with the ceramic, did it fall out in one piece, or flake off? maybe if you just cast it in there and let it pull itself off the walls...

meh, good luck on your project! I probably didn't help any, but you never know... :roll:
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