[AR] Re: Explosive Hydroforming (was Re: Re: F9 Engine Incident)
- From: Paul Mueller <paul.mueller.iii@xxxxxxxxx>
- To: arocket@xxxxxxxxxxxxx
- Date: Mon, 16 Sep 2013 16:23:06 -0600
So if I'm seeing this right, the dome is formed by pressure alone, not
requiring a backing die (which certainly simplifies machining)....? I
suppose you round over the edges of the backing plate so it doesn't form
sharp edges where the dome starts. Maybe you don't care if you will be
cutting out the domed part to weld to a cylinder anyway.
Also, would a pressure washer pump work for this (do they even go to 4500
psi?), and if not, what did you use?
Thanks,
Paul M
On Mon, Sep 16, 2013 at 3:52 PM, Charles Pooley <ckpooley@xxxxxxxxxxxxx>wrote:
> Jon: This is an old sketch of the jig for the domes for the 1994 rocket
> design. They were formed at 4500 psi with water forming 1/8" thick 6061 T6
> aluminum at room temperature. Each cycle was a few sec duration with
> manual control of water pressure.
>
> I found 4500 psi made the domes just under 1 inch deep, and results were
> consistent from dome to dome. Made about 30 total./ With 1/16", less than
> 1000 psi made a dome less deep, before getting the high pressure pump.
>
> I accidentally blew one at 7500 psi by not watching the pressure build-up
> and opening a relief valve quickly enough. Result was conical, with a torn
> opening at the jig opening.
>
> With a test square of aluminum with 1/2" grid painted on, the dome showed
> very even stretching.
>
> A friend made a thin dome 22 inch dia and used air at 120 psi. This
> method works well, the 5 min time for each being mainly that to undo bolts
> and install another 5" square of aluminum. No explosives needed.
>
> Works so well I plan this for the 8" or 10" domes for Microlaunchers.
>
> Charles Pooley
>
> ------------------------------
> *From:* Jonathan Goff <jongoff@xxxxxxxxx>
> *To:* arocket@xxxxxxxxxxxxx
> *Sent:* Monday, September 16, 2013 9:36 AM
> *Subject:* [AR] Re: Explosive Hydroforming (was Re: Re: F9 Engine
> Incident)
>
> Charles,
> I was looking at I think 30-48in hemispherical domes about .25" thick.
> Normal hydroforming might have done it, but a full hemi dome without
> tearing is non-trivial. The nice thing about explosive hydroforming is that
> if done right, the material behaves differently when you deform it really
> quickly than when you do it slowly.
>
> ~Jon
>
>
> On Mon, Sep 16, 2013 at 10:28 AM, Charles Pooley
> <ckpooley@xxxxxxxxxxxxx>wrote:
>
> For Jon: No explosives needed for simple domes. A 1994 rocket I designed
> for a project used 4 inch diameter domes for a 4 inch irrigation tube tank
> rocket. It was done with a jig and water pressure, with room temperature
> 6061 T6 aluminum. They were consistent 0.95 inch deep and required no heat
> treating or anything after.
>
> Charles Pooley
>
>
> ------------------------------
> *From:* Jonathan Goff <jongoff@xxxxxxxxx>
> *To:* arocket@xxxxxxxxxxxxx
> *Sent:* Monday, September 16, 2013 9:22 AM
> *Subject:* [AR] Explosive Hydroforming (was Re: Re: F9 Engine Incident)
>
> Carlo,
>
> I was looking into explosive hydroforming back when I was at Masten. One
> of the documents I was reading had a picture of a submarine nose cone that
> they had formed using the process. IIRC it was over 20ft wide, over 4-6"
> thick, and made of a high-strength submarine steel alloy (a maraging steel
> alloy I think). Pretty fun process. I had been thinking of using it to try
> and form tank heads out of some high-strength aluminum alloys that don't
> spin well (6013 Aluminum and stuff like that), but we ended up dropping
> that for some reason or other in favor of a more traditional spun 5059 tank
> approach.
>
> ~Jon
>
> Note: decided to change the thread name since there doesn't seem to be
> anything in the current thread related to the original thread title...
>
>
> On Sun, Sep 15, 2013 at 4:35 PM, Carlo Vaccari
> <airplaniac2002@xxxxxxxxx>wrote:
>
> I've heard of explosive welding, but not forming, at least until reading
> about the Merlin 1D. I guess it's better than simple hydroforming for thin
> shells which perhaps can balloon?
>
> Checking the Wikipedia page on it says that the SR-71 chines and various
> Russian rocket parts are formed this way...
>
>
> On Sun, Sep 15, 2013 at 6:23 PM, David Weinshenker
> <daze39@xxxxxxxxxxxxx>wrote:
>
> Krishna Kattula wrote at 06/21/2013 10:55 PM:
> > Ben Brockert wrote:
>
> >> Where did they say they were using a new process for the 1D? There
> >> were rumors of them trying a modern approach to the tube bundle
> >> concept, but I haven't seen any evidence that they're pursuing it for
> >> the current engines. 1D seems to be an evolutionary step.
> >> It's almost definitely not printed, no one has done DMLS-type
> >> processes at that scale.
> >> Ben
>
> > Explosive forming apparently:
> > http://spacenews.com/profiles/110425-elon-musk.html
> > "....
> > The hardest part of the engine to mass produce is the electro-plating of
> > nickel cobalt on the chamber. We create this thick metal jacket that
> takes
> > the primary stress of the pressure vessel and it's plated one molecule
> at a
> > time. Plating is about the slowest way you can make a metal thing. With
> the
> > Merlin-1D we take a metal jacket that is explosively formed. We take a
> metal
> > sheet that's in a cylindrical form and put it in a bucket of water,
> > effectively. Sort of a concrete pool. And you set off an explosive and
> the
> > jacket just goes "boohmp" and forms to the outer side walls into a jacket
> > shape, so you have a mold, effectively. And then you just put the jacket
> on
> > the chamber and braise it on. You can do several a day. We have a fully
> > integrated engine and it's being test-fired right now. There's really
> not a
> > lot of question marks remaining about the Merlin-1D.
> > ..."
>
> Pretty clever - the R+D work to make that a
> repeatable process must have been interesting!
>
> -dave w
>
>
>
>
>
>
>
>
>
Other related posts:
