Placement of Launch Lugs

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joeman
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Placement of Launch Lugs

Postby joeman » Sat Nov 28, 2015 2:39 pm

Hello,
My son and I our building a Aura rocket and we are going to use some 'buttons' so we can launch it on the 1010 rail.

How do we know where to place these?

I'm assuming we should have one mid-way along the root of the fins and the other at the CG (with motor installed). Would that be about right?

(Obviously we'd have them midway between two fins)

Thanks

Joseph & Jeremy
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Re: Placement of Launch Lugs

Postby Lister » Sat Nov 28, 2015 2:57 pm

I try and get the buttons to screw into the top centering ring and I try to moumt the centering ring as close as I can to the CG. I doubt the aura centering rings are thick enough to do that so just mount the top button at the and the aft button screw it in just above the bottom centering ring.. then take it out and inject some epoxy in and screw it back in and tilt the rocket slightlyso the epoxy will pool around the screws thread..

thats what I would do but im sure someone else has a better way.

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Re: Placement of Launch Lugs

Postby SpaceManMat » Sat Nov 28, 2015 3:02 pm

I usually place the bottom one just above the bottom CR so the thread grips into the CR. If the top CR is high enough then I'll use that for the top button. I think this would work ok for an Aura but if they are too close together the rocket may drag against the rail during launch. If this is the case then I will mount the button not far below the NC (or av bay) shoulder, usually with a cut down screw and nut with epoxy over the nut so recovery gear does not catch.
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Re: Placement of Launch Lugs

Postby Lister » Sat Nov 28, 2015 3:08 pm

I have also seen a nut that fits into the hole in the airframe and has a backing plate that sits flush against the inside of the airframe.. not sure where you get them but I noticed them in an apogee video.

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Re: Placement of Launch Lugs

Postby joeman » Sat Nov 28, 2015 3:38 pm

Cool. Thanks. Like the idea of taking advantage of the centering ring. So many good ideas and tips. Thanks :)
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Re: Placement of Launch Lugs

Postby OverTheTop » Sat Nov 28, 2015 4:07 pm

From what I have seen (and what I generally use) the top button goes around about where the CG is. The aft one goes as far aft as I can get it practically. I wouldn't get too hung up on the exact placement. Probably doesn't matter that much.

Using a CR to support the buttons works well. Saves putting in other bits to help.
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Re: Placement of Launch Lugs

Postby SpaceManMat » Mon Nov 30, 2015 9:49 pm

Came across these http://cart.amwprox.com/index.php?optio ... Itemid=473

Ideal for attaching the upper lug when it's not near a CR
QRS: 124
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Re: Placement of Launch Lugs

Postby Lister » Mon Nov 30, 2015 10:54 pm

SpaceManMat wrote:Came across these http://cart.amwprox.com/index.php?optio ... Itemid=473

Ideal for attaching the upper lug when it's not near a CR

Thats the one i was meaning.. Thanks for the link matt I'll grab a few. Be good for rockets where the centering ring is too thin to hold a screw.

also some of the buttons come with a nut and bolt.. doesnt hurt to epoxy the nut to the inside of the airframe or notch the centering ring and epoxy the nut into it so it sits flush with the airframe.. be sure to put a spare bolt into the nut while applying epoxy so you dont get any on the thread.

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Re: Placement of Launch Lugs

Postby SpaceManMat » Tue Dec 01, 2015 12:44 am

Lister wrote:
SpaceManMat wrote:Came across these http://cart.amwprox.com/index.php?optio ... Itemid=473

Ideal for attaching the upper lug when it's not near a CR

Thats the one i was meaning.. Thanks for the link matt I'll grab a few. Be good for rockets where the centering ring is too thin to hold a screw.

also some of the buttons come with a nut and bolt.. doesnt hurt to epoxy the nut to the inside of the airframe or notch the centering ring and epoxy the nut into it so it sits flush with the airframe.. be sure to put a spare bolt into the nut while applying epoxy so you dont get any on the thread.


A light smear of oil / wd40 will also do the trick but be careful as it also may prevent the epoxy bonding to the nut entirely.
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Re: Placement of Launch Lugs

Postby vance2loud » Tue Dec 01, 2015 1:15 am

You can make a similar mounting point by pulling the centre out of an aluminium rivet and putting a tap through the middle of the aluminium piece. I used to do similar on model aircraft. If you can find a rivet that fits inside your rail button you will get plenty of thread to lock it in place. You could possibly use normal or stainless rivets as well but they will be a bit harder to tap.
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joeman
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Re: Placement of Launch Lugs

Postby joeman » Wed Dec 09, 2015 7:09 pm

Hi Guys,
This is what I got with my buttons.

But I seem to be missing a nut. They'd normally come with a but wouldn't they?


Thanks

Joe
p.s. I think I'm going to suggest to my Son that we ditch the buttons and go for hollow guide tube instead.
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Re: Placement of Launch Lugs

Postby Lister » Wed Dec 09, 2015 9:09 pm

The new lot dont have nuts with them.. I bought 5 lots only to discover they dont come with the buttons now :?

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Re: Placement of Launch Lugs

Postby SpaceManMat » Wed Dec 09, 2015 9:19 pm

Are these from Aus Rocktery? I didn't think there's came with a nut. If you're looking at putting an F or G motor in the Aura then I would definitely not use tube. Seen too many rocketry hanging sideways off a flexing launch rail, looks a bit silly to me. Go down your hardware store and find some nuts or self taping screws.
QRS: 124
AMRS: 32 L2 RSO
Highest Altitude: 10,849 feet
Largest Motor: CTI 1115J530 IM
Current Project: X Wing

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Re: Placement of Launch Lugs

Postby joeman » Thu Dec 10, 2015 8:12 am

Yep. From AusRocketry.

ok. I'll get a few nuts for these.

Cheers!

Joe
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Re: Placement of Launch Lugs

Postby jase » Thu Dec 10, 2015 12:53 pm

No Nuts @ Ausrocketry ??? HAHAHA :lol:

FWIW - I prefer nut-less :shock: :wink:

New Jules Verne rocket perhaps, The Nutless ??? :roll: (back to work now jase)...

...but HEY, could be on to something?

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