Anthony:
Clever, I suspect a small inner tube might just do the job. Now I have to
figure out how to get epdm in place (w/ bonding agent)....
Bill
On Thu, Aug 23, 2018 at 8:19 PM <acesaroni@xxxxxxxxxxx> wrote:
https://www.torrtech.com/Pages/Inflatables.htm
Anthony J. Cesaroni
President/CEO
Cesaroni Technology/Cesaroni Aerospace
http://www.cesaronitech.com/
(941) 360-3100 x101 Sarasota
(905) 887-2370 x222 Toronto
*From:* arocket-bounce@xxxxxxxxxxxxx <arocket-bounce@xxxxxxxxxxxxx> *On
Behalf Of *William Claybaugh
*Sent:* Thursday, August 23, 2018 9:07 PM
*To:* arocket@xxxxxxxxxxxxx
*Subject:* [AR] Re: Sealing phenolic liner joints
Wyatt:
So far, the best I’ve come up w/ is a double layer of EPDM on the ID of
the liner (doubled so the joint is offset 180 degrees between the two
layers).
The issue is that the joint is 34.75 inches down a 8.125” ID
tube...slightly longer than my right arm. Further, I think I need to have
both pieces of liner in the motor tube (fully greased) so as to assure they
are butted and aligned. This improves the access problem by an additional
5.5 inches....
I’d welcome any thoughts on tools that would allow reliably bonding epdm
(or anything else) “down the tube”.
Bill
On Thu, Aug 23, 2018 at 6:27 PM Wyatt Rehder <wyatt.rehder@xxxxxxxxx>
wrote:
Bill,
That makes more sense. I'll refrain from giving much for "actual
recommendations" as I've never run a motor in your configuration
before. Though I'd imagine sealing the gap with EPDM rubber, an
ablative epoxy mix (epoxy and phenolic microspheres) or ablative of
your choice would be sufficient for something like that. Might work
better to seal the joint prior to casting your grain in the liner, as
you could put a bit of an ablative cap on the inside to shore it up a
bit better; and give you a little more safety margin for gasses trying
to get by.
- Wyatt
On Thu, Aug 23, 2018 at 4:03 PM William Claybaugh <wclaybaugh2@xxxxxxxxx>
wrote:
cast directly against the liner. Thus the concern about a backface ignition
Wyatt:
There are no grains to glue to the liner, the propellant is poured and
at the joint.
for ease of insertion and removal).
The liner fit to the tube wall is w/i 0.005”; I will use grease (mostly
wrote:
Bill
On Thu, Aug 23, 2018 at 5:56 PM Wyatt Rehder <wyatt.rehder@xxxxxxxxx>
wclaybaugh2@xxxxxxxxx> wrote:
As far as I know that is standard practice on longer motors, just
having the joint be in the center of a grain.
You can also glue the grains into the liner for some additional
sealing between the grain and the liner. You hopefully shouldn't see
much gas between your liner and the tube, so long as you have a decent
fit between the two. The gas in the core should expand your liner out
to fit against your case, as the case is the load bearing element. If
you have your seal between your grain and your liner good enough there
shouldn't be a path for gases to travel. Some grease on the inside of
the case might also discourage your hot gas flows a bit.
-Wyatt
On Thu, Aug 23, 2018 at 2:39 PM William Claybaugh <
length as liner for 67.5” of case bonded propellant. This means that the
My 9” motor uses two pieces of phenolic tubing 34.75” in (nominal)
joint between the two pieces of liner is exactly at the center of the
propellant grain.
liner OD and the tube ID, it follows that such gas could ignite the back of
Given that some hot gas will—intentionally—fill any voids between the
the propellant grain at the joint unless that joint is sealed.
that location, probably just warm) gas?
Is there an experience in sealing such a joint against hot (or, at
Thanks,
Bill