It's just a thought that crossed my mind when you mentioned the anomaly. I
just know that a torque of twisting action happens with fluids flowing
through a line or duct. Are you familiar with the mass flowmeter I
mentioned Carl? It's made of a 'U' tube that vibrates and a torque is
produced when fluid flows through the U tube when vibrating with the
torque directly proportional to the mass flowing through the tube.
Somewhere I have a 16mm film of a H-1 rocket engine test which shows one
of the propellant ducts twisting upon ignition and transition to main
stage, very dramatic and not subtle in the least. This may be different
physics involved than the mass flowmeter, a bit outside my area of
experience.
Maybe somebody else on this list might have some ideas.
K
On Fri, Jul 31, 2020 at 5:38 PM Carl Tedesco <ctedesco@xxxxxxxxxxxxxx>
wrote:
I’m sure at least one of the propellant lines makes a 90 degree turn into
the rocket motor. But if this were the case, wouldn’t it continue to torque
the rocket until the rocket gains enough speed to be aerodynamically
stabile? What I have seen is just one abrupt “kick-over” then the rocket
flies true. Full disclosure: We are not always able to locate the launch
lugs at the CG and CP.
--- Carl
*From:* arocket-bounce@xxxxxxxxxxxxx <arocket-bounce@xxxxxxxxxxxxx> *On
Behalf Of *ken mason
*Sent:* Friday, July 31, 2020 12:22 PM
*To:* arocket@xxxxxxxxxxxxx
*Subject:* [AR] Re: Modeling liquid engine aft body in OpenRocket
Carl, do you have any plumbing runs perpendicular to the flight path where
corriolous might cause a torque moment?
This effect is used in very precise mass flowmeter like the Micromotion
brand,I used the model C with 1/10% accuracy. Model D replaced it.
Ken
On Fri, Jul 31, 2020 at 10:48 AM Carl Tedesco <ctedesco@xxxxxxxxxxxxxx>
wrote:
Bob,
FYI… here is a design for a retractable launch lug. This is for a C-type
rail, but we have modified for the Baxter launcher at FAR which uses a
T-type rail. I have found (and you can sim to verify) that the launch
lugs/rail guides add a "not non-significant" amount of drag to the rocket.
<<...>> <<...>>
Kevin,
I have had "slow" accelerating liquids weathercock by 5-10° even in light
wind conditions off the Baxter rail at FAR. I feel there might be some sort
of "torqueing "effect as the aft rail guide leaves the rail. Can anyone
address this?
--- Carl Tedesco
-----Original Message-----
From: arocket-bounce@xxxxxxxxxxxxx <arocket-bounce@xxxxxxxxxxxxx> On
Behalf Of Robert Watzlavick
Sent: Wednesday, July 29, 2020 5:42 PM
To: arocket@xxxxxxxxxxxxx; Kevin Ho <rebelwithoutajob@xxxxxxxxxxx>
Subject: [AR] Re: Modeling liquid engine aft body in OpenRocket
I was going to follow the FAR guidelines for the Baxter launcher, placing
one at the CG and one at the aft end of the body. I've seen other
references that suggest one at the CG and one at the CP. The skin is very
thin (0.016 inches) so I'm going to have to add stiffeners underneath.
I'd really like to 3D print the rail guides out of nylon but I'm worried
the steel rail will cut through it so I'll make them out of aluminum.
-Bob
On 7/29/20 7:17 PM, Kevin Ho wrote:
IIRC you are using a long rail, which should reduce weathercocking to
a certain extent. Longer rails means higher off-rail speed, which
means that even in a wind gust your relative wind will shift by less
degrees off the nose.
Also a controversial topic, but where are your rail buttons going to
be? That can greatly affect off-rail weathercocking. Placing the aft
button close to the CP can reduce the swing somewhat.