Placement of Launch Lugs

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Kryten
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Re: Placement of Launch Lugs

Postby Kryten » Fri Dec 11, 2015 7:05 am

:lol:
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joeman
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Re: Placement of Launch Lugs

Postby joeman » Sat Dec 12, 2015 10:31 am

Nice photo Jase. Awesome movie.

Anyhow, I think I know why no 'nut' has been included, because if one puts a nut on, it might not slide terribly well on the 1010. It might grind against it. Also, it is hard to get to other end of screw to tighten it.

I decided to areldite the button on to the screw as well as areldite the screw in place.

For where I cannot put a screw in (because the motor tube is in the way) I:-
1. Cut off head off screw
2. Scuff bottom of button with sand paper
3. Drill hole in rocket tube
4. Scuff rocket tube around hole with sandpaper
5. Put some sellys putty into the hole...pushing it through with a stick
6. Make some 5-min areldite up
7. Immerse screw in areldite and push screw through hole and into sellys putty
8. Put a bit more areldite over screw, on the bottom of button and on rocket tube around screw
9. Slide button on
10. Make sure it is all seated ok and give it plenty of time to dry.

It seems pretty strong. Slides up and down the 1010 well.

What do you reckon?
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L1 - Callisto (H133) - 11-Jan-2016

joeman
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Re: Placement of Launch Lugs

Postby joeman » Sat Dec 12, 2015 10:56 am

That is os obviously not the final rocket tube....just something for me to experiment on. :)
L1 - Callisto (H133) - 11-Jan-2016

Lister
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Re: Placement of Launch Lugs

Postby Lister » Sat Dec 12, 2015 1:12 pm

The nut goes inside the airframe.. you screw from the outside *that sounds wrong*. If I were you 1 I wouldnt use araldyte as its brittle as buggery and 2 I would have it screwed into something like centering rings as they tend to rip out of cardboard.. maybe drop a few hundred grams onto the lug and see if it snaps off.

joeman
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Re: Placement of Launch Lugs

Postby joeman » Sat Dec 12, 2015 3:00 pm

They do seem very strong. Would think the tube would break before anything else 'falls off'.

I'll hang a weight from the 'test' set-up buttons to see how it fairs.

Yeah, I don't have much of a centering ring. So what I did was put selleys putty stuff (that sets like rock...and is the same material I use for fillets) through the small hole. Then I put the screw INTO this material, while it is still soft. So this should help to distribute the load over more of the airframe and the selleys putty also bonds to the motor mount tube as well.
L1 - Callisto (H133) - 11-Jan-2016

Lister
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Re: Placement of Launch Lugs

Postby Lister » Sat Dec 12, 2015 3:06 pm

Maybe build up around the centering ring and mount the screw into that.. its just if you screw it into the centering ring it will help distribute the force alot more than if its in the airframe.. how heavy is this rocket?

joeman
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Re: Placement of Launch Lugs

Postby joeman » Sat Dec 12, 2015 3:15 pm

Hi Lister,
It is 225grams in total (exc motor).

I did hang a 4kg dumbell weight from each button on the 'test' setup. Seemed to take it quite well. Tried from different directions.
That being said, the cardboard is a little thicker in this 'test' setup.
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Lister
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Re: Placement of Launch Lugs

Postby Lister » Sat Dec 12, 2015 3:47 pm

A weight of 220g I would think it would be fine with a set up like that if its holding up to 4 kg.. just make sure the top buttons around the CG.

did you try dropping the weight from an inch or so to see if they shear?

my bench test is normally a whack on the bench.. if it breaks it was too weak.. if it holds im gold ;)

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Re: Placement of Launch Lugs

Postby OverTheTop » Sat Dec 12, 2015 3:53 pm

did you try dropping the weight from an inch or so to see if they shear?


Careful with this test. It is surprisingly aggressive and depends heavily on the mountings and the material used to suspend the weight.
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Lister
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Re: Placement of Launch Lugs

Postby Lister » Sat Dec 12, 2015 4:03 pm

Very true but the way i see it is the force from a rocket being corrected on a rail can be quite aggressive and dependant upon the same things that will ensure the lugs stay on.


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