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My L3 Project
#11
(03-01-2014, 10:54 PM)Nat Kinsey link Wrote: I plan to use an eye bolt in the forward closure of the motor, with a slack loop on a u-bolt in the top ring for a backup. 
N

Good move Nat.  I do that with my 75 mm cases.  Perfect insurance and cheap.
Jim
Jim Goggins NAR  L3
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#12
You guys have me rethinking the recovery harness mount...
I will be using a CTI 75mm casing, installed with a 75mm CTI adapter to fit the 98mm MMT...
Using single forged eyebolt mounted to the end of the casing would save some components.
Nat it sounds like you feel a backup using a u bolt on the fwd ring is a good idea, if I have it correct..
Greg Young - L3
NAR #42065
TRA #00234
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#13
Since weight isn't an issue, nor is space, I figure why not. 

Reality though-  a proper backup would be a second, full length plus, shock cord on that u-bolt.  If something fails in the primary attachment it's likely to be the shock cord itself.  A secondary attachment point that is somehow connected to the primary shock cord may find it's connection location below the point where the primary broke.  A backup strap between primary and my u-bolt would only succeed in the case of the eye-bolt backing out of the motor hardware or a similar sort of failure.

N
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#14
I actually used that method Nat when I flew my 1st L3.  I didn't use the backup shock cord for the main body, but for the 20 lb nosecone.  There was a shock cord attached inside to a centering ring in the nose and it was attached to the centering ring on the shoulder that had the U bolt attached for the main shock cord.  Good thing I did because the deployment of the nose cone yanked the main shock cord thereby ripping the shoulder centering ring completely out of the nose cone (fiberglass with wood bulkhead).  The second attached small length of shock cord saved the day.

Backups for anything is always good insurance.
JD's thoughts of coming up with some way to reduce the stress of deployment would be great as the BP charges no matter how you figure them still create a lot of stress once separation occurs.  It's almost like the chute needs to be able to open in small stages without a big yank. 

As for using threaded rods and the fact that it seems like overkill is true and false in my opinion.  Linda's Max that came down in flames for instance.  The entire fin can assembly withstood the motor CATO, stress of deployment, and the whacked out motor ignition.  Yes, it was built like a moose and burned to a crisp but it stayed intact. Smile  Of course that being said, it was still destroyed regardless.  :'(
I guess in the end it looks cool and it it gives the flier a better sense of security in having a successful flight for an added couple of bucks considering the high expense involved, then why not.
Jim Goggins NAR  L3
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#15
OK taking John's idea a little further, I played around with my forged eyebolt using the threaded insert on the fwd closure.
It certainly would simply recovery harness attachment, and looks like a slick way to mount the recovery harness.
That being said, one question immediately comes to mind - what stops that eyebolt from unthreading from the forward closure should the sustainer be rotating on the shock during descent?
Is that where a second recovery harness attachment like a U bolt, or forged eyebolt mounted to the first CR with the end of the harness tied to it, would prove useful?
Greg Young - L3
NAR #42065
TRA #00234
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#16
Jam nut against the closure.

N
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#17
(03-09-2014, 07:42 PM)Nat Kinsey link Wrote: Jam nut against the closure.

N
And Blue Loctite for insurance,
And add a swivel if you want teritiary insurance.
John Derimiggio
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#18
I jammed the nut, but it still could loosen. Considered Locktite, but thought you all might have a different approach
There is a swivel on the chute itself, so that may be adequate.
I am using the CTI 75 mm to 98mm adapter to secure the reload casing to the 98mm MM tube, which is why I initially thought mounting the harness to an epoxied in ring might be a little more sound.
Reflecting on it a little more, if the adapter is attached firmly enough to hold the motor in place during launch, it ought to be fine to handle recovery stresses.
Thanks for the suggestions!
A single forged eyebolt, attached to the fwd enclosure of the 75mm reload casing using a little Locktite, it is!
Greg Young - L3
NAR #42065
TRA #00234
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#19
John is right.  Swivels.  Give it something else to twist and it will leave your jam nut alone.  ;D

Dale
Dale Stoyer - L3
NAR #91256
TRA #13499
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#20
Yes and replace the swivel on the chute (which is probably a weak little thingy) with a big honkin swivel on the motor end. 
John Derimiggio
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