Need help on launch lug sizing - Northern Colorado Rocketry

This topic has 67 replies, 9 voices, and was last updated 19 years ago by Warren B. Musselman.

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April 26, 2006 at 2:27 am #39633
Ken Plattner
Participant
How do I determine the size (diameter and length) needed for a launch lug? I’m building a new design using a 4″ tube approximately 48″ in length. Total length of rocket will be about 64″. Three clustered G motors.

Any help would be appreciated.

Thanks.
April 26, 2006 at 3:08 am #42064
Doug Gerrard
Participant
Start by throwing the lug away and switch to rail buttons 😉 Seriously, the issue isn’t so much length as distance between the two rail guides / launch lugs. For a rocket that size, don’t just use one. One rail guide / lug should be about at the genter of gravity or forward and the other as far aft as reasonable.

If you wish to use lugs, I would think 1/2″ diameter rod should do. Some may think that too big but to avoid rod whip it has to be rigid. I hope this helps.

Doug
April 26, 2006 at 4:40 am #42065
Chris LaPanse
Theoretically, a 3/8 or 1/2 inch lug would be fine.

Realitically, throw the lugs away and switch to rails. They whip less, are easy to use, and the buttons add less drag and impact the appearance a lot less.

Overall, they’re a much better choice.
April 26, 2006 at 11:54 pm #42066
denverdoc
Agree with CJL. Not only that TRA may follow CAR’s (Canada Assoc Rocketry) and disallow them on all H and above birds, so you may end up having to retrofit ayway. Hobbytown has some nice “rail lugs” for a few bucks which can be glued or screwed to your rocket. Just spend some time using angle iron or a plumb line to make sure you get the two lined up exactly…
JS
April 27, 2006 at 2:03 am #42067
Ken Plattner
Participant
Thanks to all that replied. Picked up two 5/16″ rail lugs today at HobbyTown.

Ken P.
April 27, 2006 at 3:00 am #42068
denverdoc
Assuming you went to the HT at 92’nd, notice if there were any K’s?
J
April 27, 2006 at 3:04 am #42069
Chris LaPanse
Why would they have K’s?

Did Joe finally secure a LEDP?
April 27, 2006 at 3:23 am #42070
Ken Plattner
Participant
I did go to the HT on 92nd. Didn’t notice any K’s. In fact, I wouldn’t know one if I saw it 😀 . Did see alot of anodized aluminum stuff though. I’m pretty new to the larger rockets. Growin up there were only A, B and C’s. Just launched an E with my 11 yr old and that was pretty big. Hoping to launch a G at the MHM. I just hope it flies!

I did go to the HT in Longmont and they had some large red tubes (maybe 3″ x 18″??).

kp
April 27, 2006 at 3:36 am #42071
Chris LaPanse
yeah – those are motor casings. John (I assume) was asking about reloads.

Also, good luck with mile hi mayhem, and trust me, you’ll be hooked 🙂

Someday, you’ll think of G’s as the motor you launch when you can’t afford an I (or bigger) 😀

If it’s a rocket, it’s good though, and with those linear lugs, just make sure they’re aligned. If they are, it should all work out. I assume you got the PML lugs, and if that’s the case, I have them on my AMRAAM and they work great.
April 27, 2006 at 10:14 am #42072
denverdoc
oh, and xman, whatever you do with your cluster, do not, repeat, do not attempt to use the copperhead igniters for your cluster. They simply aren’t reliable enough. 🙄 And of course a cluster of 3 G’s would require a level 1 certification flight first.

First fire jrs should be available at HT–5 bucks for 3 seems like a lot, but in this instance, $$ well spent. If they are out, one of the vendors should have something appropriate.
John S
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