Thank you - An excellent tip about the chamfer. It was very difficult
to start the thread on the first rods. I'm using a cutting oil that
says it's for aluminum.
Richard
On Mon, Aug 20, 2012 at 8:24 AM, Jim - TFJ <jim@xxxxxxxxxxxxxxx
<mailto:jim@xxxxxxxxxxxxxxx>> wrote:
Try setting them on a screw.
That should put them pretty close to where you want them in the need.
ah, 3/16 right?
That's the nominal OD for 10-24.
Also, be sure to chamfer the end of the rod before trying to thread.
That helps a lot!
------------------------------------------------------------------------
*From:* roc-chat-bounce@xxxxxxxxxxxxx
<mailto:roc-chat-bounce@xxxxxxxxxxxxx>
[mailto:roc-chat-bounce@xxxxxxxxxxxxx
<mailto:roc-chat-bounce@xxxxxxxxxxxxx>] *On Behalf Of *Richard
Dierking
*Sent:* Sunday, August 19, 2012 11:22 PM
*To:* roc-chat@xxxxxxxxxxxxx <mailto:roc-chat@xxxxxxxxxxxxx>
*Subject:* [roc-chat] Re: Using Aluminum Hardware: Lighter but
strong enough?
Sorry, yes, adjustable _die_. Always get those mixed up. It's a
13/16" diameter rod die with three adjustment screws for the
diameter. Really looking forward to receiving it tomorrow and
doing some testing.
Again, sorry for referring to the wrong tool.
Richard
On Sun, Aug 19, 2012 at 9:58 PM, jim <jim@xxxxxxxxxxxxxxx
<mailto:jim@xxxxxxxxxxxxxxx>> wrote:
Adjustable tap? or do you mean an adjustable threading die
(taps make internal threads, dies make external ones.)
Unless there’s something I haven’t understood yet, I haven’t
bought a threading die yet that didn’t need to be opened up
wider to
make the correct pitch diameter on a stud.
Jim G
------------------------------------------------------------------------
*From:*roc-chat-bounce@xxxxxxxxxxxxx
<mailto:roc-chat-bounce@xxxxxxxxxxxxx>
[mailto:roc-chat-bounce@xxxxxxxxxxxxx
<mailto:roc-chat-bounce@xxxxxxxxxxxxx>] *On Behalf Of *Kurt
Gugisberg
*Sent:* Saturday, August 18, 2012 3:07 PM
*To:* roc-chat@xxxxxxxxxxxxx <mailto:roc-chat@xxxxxxxxxxxxx>
*Subject:* [roc-chat] Re: Using Aluminum Hardware: Lighter but
strong enough?
Hey Richard. Great work on the testing. It confirms my
thoughts on fin attachment. I am interested in seeing how
nylon nuts hold up under high shock loads. After pulling
steel eye bolts straight and seeing fender washers pulled
through 1/2 plywood bulkheads, I have my doubts about aluminum
and nylon holding up.
Also, what is an /adjustable/ 10/24 tap?
Kurt
-----Original Message-----
From: Richard Dierking
Sent: Aug 18, 2012 10:20 AM
To: roc-chat@xxxxxxxxxxxxx <mailto:roc-chat@xxxxxxxxxxxxx>
Subject: [roc-chat] Using Aluminum Hardware: Lighter but
strong enough?
Since I've had the opportunity to go through some of my old
projects lately (cleaning out the garage), I've been taking
some rocket airframes apart including some destructive
testing. It's interesting to see what holds and where
weakness occurs. For example, for through the wall fins, the
surface fillet doesn't seem to do much. The most important
thing is that the fin slot is tight. So the lesson here is to
create tight slots and don't expect for epoxy to fill the gap
and hold strong.
For attaching the fin, creating many small slots (1/8"
deep) in the root edge for attachment to the motor mount works
well and doesn't require much epoxy. Bryan showed me how to
do this. If the surface is roughed-up with 80 grit sand paper
a fillet doesn't seem to be required. The failure I'm seeing
is the motor mount tube material. The surface of paper tubes
peels and phenolic fractures and peels. And, as expected,
fiberglassing the root to the motor mount tube works best, and
it doesn't require much resin. In fact, the lay-up can be
pretty dry and it seems to do fine. The extra amount of resin
I commonly use for a good finish is not necessary. I guess
drilling small holes in the motor mount tube where the fins
are attached might help hold the epoxy bond between the fin
and the tube. I haven't tried this yet.
**Another thing I've been experimenting with is the altimeter
bay. This is the important part of this message, and sorry it
took so long to get around to it.** Recently, I've done a few
deployment tests using 3/16" aluminum rods that are tapped to
10-24 tread and nylon hardware (nuts and wing nuts) to hold
the bay together. Also, I reduced the size of the U bolts
significantly. I replaced the 1/4"-20 U bolts (1" wide) with
U bolts from Home Depot that are in packs for cable clamps
(5/8" wide). Even though the cable clamps say they are 1/4"
size, the nuts are actually 6 mm metric. Just to give an idea
of the weight savings; Replacing the steel hardware and
reducing the size of the U-bolts on a 4" diameter altimeter
bay reduced the weight from 495 grams to 325 grams (34%
less). Also, instead of using metal fender washers, I've been
fiberglassing both sides of the bulkheads, and switched from
1/4" thick plywood to 1/8" thick. So, no more
fender washers. I'm wondering if I could make aluminum
U-bolts without causing too much stress on the aluminum rod
during the bend?
The deployment tests have gone so well, that I just ordered
some 3/16" high-strength aluminum (alloy 7075) rod, aluminum
nuts, and other light-weight hardware from McMaster-Carr. I
also ordered an adjustable 10-24 tap. I would appreciate any
advice on threading this new aluminum rod.
So, do you think this will hold? Are there problems with
using aluminum hardware I need to consider.
If you're interested in using light-weight materials and
techniques for your project, I would like to discuss at the
September launch. I'm planning on launching a two-stage
rocket with the 'new' hardware.
Richard
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