https://youtu.be/7i-zdEOKgQc the test of my motor recently discussed
Nikolai Nielsen
On Sat, Sep 9, 2017 at 3:49 AM, Steve Peterson <dmarc-noreply@xxxxxxxxxxxxx>
wrote:
Nikolai,
I do get that you are taking *some* precautions. Wearing safety glasses is
good. Taking refuge behind a compost bin (hopefully full of compost) is
also good. That you took an hour to write your message is great.
But what I seem unable to convey to you is that you are not doing the
right things, and I think that is because you are being lulled into a false
sense of security because of the rather mild way your motors have ruptured
so far. The early ones ejected the nozzle because the nozzle wasn't
securely attached. Your containment "worked" not because it was well
designed but because the rocket never came up to full pressure. It may have
also caused you to think that's the way rockets fail. Then, by your own
description, your end burner failed *in a new way*, but, again, at low
pressure because the pvc either wasn't high quality to begin with or had
deteriorated over the time it was used for irrigation. Again, your
containment "worked" (note the quotes) not because it was proper
containment, but because the cato was so mild.
As you build rockets that actually do come up to full operating pressure,
they will continue to fail *in new ways* and with so much more explosive
power that your current preparations will be unable to contain the blast.
Since I seem utterly incapable of finding the words to convey just how
powerful a motor can be when it is at full pressure (as yours appear not to
have been), I found a video on youtube that conveys what I am talking about:
https://www.youtube.com/watch?v=lHOxRa4Icwg
Now tell me again how, exactly, your nail, wire, pvc, and a bucket are
going to contain a *real* cato?
--Steve
On 09/08/2017 01:37 PM, Nikolai Nielsen wrote:
The setup I use is explained in my tutorial https://youtu.be/fEyk-Mj1xHU
at 21:49(please go watch it before continuing reading) .
The thing that you said looked like a tile was a piece of particle board
that was drenched in water from the recent rain and in the video I was
using powdered fuel that I put down the nozzle because I don't have any
other ignition methods that can fit down a 2 mm hole so I used powder that
was lit with a fuse that took quite a long time to actually reach the
powder so I obviously didn't add that to the video.
With regards to my own safety, the place where I stand is behind a large
wooden compost bin which the edge of is literally 2 cm below the view of
the camera and the boards are quite thick. I am also wearing safety glasses
that my neighbour gave me from his work and he works at a steel milling and
machining factory so these glasses are of a high standard.
The pipe that I show in the end of the video where you can see it has
ruptured is actually the first time I've ever had a pipe rupture as usually
either the nozzle or the rear bulkhead pops out when I'm using the 40mm OD
schedule 40 pipe but the green pipe seen in the video was a whole bunch of
pipe that I saw the grounds staff at my school tossing out so I took it to
make motors(which is the same pipe that grant Thompson uses in his screw
lock sugar motor tutorial).
For testing small motors like the one in my tutorial and the above
mentioned one, I test those in our garden but the motor that I was
discussing in the "my biggest motor" thread, (
https://youtu.be/XZCcoiwihqs it's the second clip) my dad wouldn't let
me do it in the garden so I arranged with my amazing science teacher to do
it at school on a weekend. I made extra sure of safety on that one as I
managed to get a very thick walled pipe that left about 1cm gap between the
pipe and motor in order to give the motor some space in case it ruptures. I
also put one of the garden poles through the pipe behind the motor and
rammed it into the ground + I put a brick behind the pipe with an
additional two garden poles to make sure that the motor would not be able
to move forward if it was successful. I also placed a bag of heavy firewood
on top of the pipe to stop it from lifting the poles out of the ground. I
then placed a metal fence gate (which was quite heavy btw)on front of the
motor to stop the motor if it got ejected(which it did and successfully
stopped). For my and my teachers safety, I brought with a wooden pallet to
hide behind so that I could touch off the igniter with the
battery(explained in first video).
With regards to the motor that I'm making at the moment, I'm rather not
going to use iron oxide and the nozzle I have drilled is 4 mm and the grain
diameter is 33mm so I should be relatively on the safe side(right?)
Any way as I said a couple messages ago, I'm just experimenting with end
burners as I already have a proven design that is shown in the tutorial.
I appreciate the help you guys(and gals... I think) have shared with me
and others, I'm glad I joined this group and have been able to learn from
the best ^_^
Kind regards
Nikolai Nielsen
(This took me like an hour to type)
