Something I have to continuously remind myself of… And I finally decided to
throw this into the discussion…
Don’t over-think…
Don’t over-think…
Don’t over-think…
Sometimes stuff happens…
You’ll pay extra attention “next time”, probably about as much as can be asked
for…
From: roc-chat-bounce@xxxxxxxxxxxxx <roc-chat-bounce@xxxxxxxxxxxxx> On Behalf
Of Jason Muckenthaler (Redacted sender "jmuck78" for DMARC)
Sent: Tuesday, July 23, 2019 4:09 PM
To: roc-chat@xxxxxxxxxxxxx
Subject: [roc-chat] Re: Rail Button Damage on LOC Army Hawk
Thanks, Kurt. It sounds like there is at least a consensus that the rail
button damaged happened during launch (or at least did not happen during
flight, landing, or on the ground). Oh well, something to keep an eye on in
the future.
On Jul 23, 2019, at 3:34 PM, Kurt Gugisberg <kurtgug@xxxxxxxxx
<mailto:kurtgug@xxxxxxxxx> > wrote:
Maybe it was the perfect storm of torquing in the wind just as it took off with
a kick in the butt motor. The rails are one piece so no seems or anything to
snag it.
Kurt
On Tue, Jul 23, 2019 at 2:52 PM Cris Erving <cris.erving@xxxxxxxxxxx
<mailto:cris.erving@xxxxxxxxxxx> > wrote:
I have a couple of rockets that have enough flights on them that the skinny
part of the buttons are worn flat from contact with the rail. Completely
different wear pattern from these pictures. To me it looks like the top part
of the buttons hit a seam on the rail, or something like that, and sheared off.
No way a shock cord or torquing on the rail would do that kind of damage. A
shock cord would bend the button, and these look straight; ditto for torquing
on the rail.
Eggtimer Cris
_____
From: roc-chat-bounce@xxxxxxxxxxxxx <mailto:roc-chat-bounce@xxxxxxxxxxxxx>
<roc-chat-bounce@xxxxxxxxxxxxx <mailto:roc-chat-bounce@xxxxxxxxxxxxx> > on
behalf of Mike Riss <dmarc-noreply@xxxxxxxxxxxxx
<mailto:dmarc-noreply@xxxxxxxxxxxxx> >
Sent: Tuesday, July 23, 2019 2:35 PM
To: roc-chat@xxxxxxxxxxxxx <mailto:roc-chat@xxxxxxxxxxxxx>
<roc-chat@xxxxxxxxxxxxx <mailto:roc-chat@xxxxxxxxxxxxx> >
Subject: [roc-chat] Re: Rail Button Damage on LOC Army Hawk
Jason,
The vertical black marks to the left of the rail buttons, most visible in the
second pic, make me think the rocket rubbed on the rail at some point. If this
didn't happen during loading, I'd guess there was some friction on the buttons
during takeoff, causing the damage. I have seen some worn flat spots on some
of my rail buttons, mainly the center sections (nothing like in your pics, but
the buttons were on lighter rockets flying on smaller motors).
Mike
On Monday, July 22, 2019, 6:28:33 PM PDT, Jason Muckenthaler
<dmarc-noreply@xxxxxxxxxxxxx <mailto:dmarc-noreply@xxxxxxxxxxxxx> > wrote:
After retrieving the LOC Hawk on Saturday, I noticed that both rail buttons had
been damaged with very little damage to area immediately surrounding the rail
button locations. My initial, knee-jerk reaction was that the rail button
damage was just another consequence of the rocket being carried across the
lakebed, but on further reflection, I wonder if the damage was actually caused
during the launch. The wind was blowing at a healthy pace (while still less
than the 20 mph limit) and the rocket has quite a large fin area. The large
fin area coupled with a potential torque due to the nozzle exhaust hitting the
blast deflector at an angle, may have been enough to shear the outer edges of
the rail buttons off before the rocket cleared the tower.
I have attached pictures of the two rail button locations, and there is a clear
lack of road rash in the vicinity. The other possibility is that the rail
buttons impacted something during its trip along the lakebed, but if that were
the case, I would have expected the rail button screws to show some deflection
or some other impact damage - but there is no such visible damage to the rail
button screws.
I am also now curious if I should have used one of the larger unistrut rails
instead of the 1515 rail tripod. I don’t know where the cutoff for using the
1515 tripod launcher is versus the unistrut rail (and I should have asked prior
to the launch, but it didn’t occur to me until I saw that rail buttons). Does
anyone else have any similar experience with broken rail buttons like this, or
does this look more like damage from wind carrying the rocket across the
lakebed, and I’m just not recognizing it?
Some Data: The Lift off weight was about 46 lbs with the M1297. Velocity off
the rail (according to OR) was about 40 mph.
Greg Smith has a nice video of this torque on his blog from 2016 here:
http://hawtakshun.blogspot.com/2017/01/lucerne-dry-lake-november-2016-l1500-is.html
Thanks,
Jason
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