Guidance on recovery hardware sizing

[danielhv]

Is there not any widely accepted standards on recovery hardware sizing? I’ve searched all in and around this rabbit hole and can’t seem to find anything definitive.

Building my punisher 3, and not sure what size quick links, eye bolts/nuts to use. Obviously we want max strength with minimal weight, but there’s a point where it’s just too overkill.

 

[-Slick-Ice]

Hi, in the descriptions of the harness on the Wildman site they have recommendations for sizing.

There is also another post from OneBadHawk covering these
https://www.rocketryforum.com/threa...ness-mount-in-the-fincan.171991/#post-2380914

 

[danielhv]

Hi, in the descriptions of the harness on the Wildman site they have recommendations for sizing.

I must be looking in the wrong place because I don't see it on the Punisher product page, the recommended harness page, or their recovery products pages.

 

[-Slick-Ice]

Its in the harness description...
https://wildmanrocketry.com/collections/onebadhawk-harnesses/products/3-inch-harnesshttps://wildmanrocketry.com/collections/onebadhawk-harnesses/products/4-inch-harness
I would look at either of those depending on how much space you have available or send onebadhawk sales an email and he can custom make one for about the same price

Otherwise if you want a nylon I have a bunch left over from 3 and 4" LOC kits you can have.

 

[danielhv]

Its in the harness description...
https://wildmanrocketry.com/collections/onebadhawk-harnesses/products/3-inch-harnesshttps://wildmanrocketry.com/collections/onebadhawk-harnesses/products/4-inch-harness
I would look at either of those depending on how much space you have available or send onebadhawk sales an email and he can custom make one for about the same price

Otherwise if you want a nylon I have a bunch left over from 3 and 4" LOC kits you can have.

I'm not talking about the harness. I'm asking about the hardware... quick links, eye bolt, etc. I have the OBH harness already. Just shopping for the hardware to connect everything up and not certain how "heavy duty" I should be going.

 

[-Slick-Ice]

My vote would be 1/4" for hardware for the eye bolts and quick links.

 

[Rschub]

I have been using the 3/16" ones myself for my 5-10 lb rockets.

 

[Antares JS]

1/8" ones are fine for rockets weighing under 5 pounds or so.

 

[Handeman]

I use U-bolts on the ends of the av-bay to spread the load out near the threaded rods that go end to end in the av-bay. As long a the quick link opens enough to fit over the U-bolt, that's as big as I use. I've got a 1/4" U-bolt on my 55 lbs. rocket and 3/16" on the ones over 15 lbs. the 1/8" U-bolts work for anything smaller than that. In 15 years, I've never had a quick link fail or a U-bolt get bent or distorted. YMMV

 

[pathtouch]

Another guideline I see a lot is to plan for 50-100 Gs of acceleration in a bad recovery deployment. That’d be like the delay on a motor eject opening early or late and a chute is inflating with lots of velocity.

So if your fin can weighs 5 lbs plan on hardware good for 250-500 lbs.

 

[Onebadhawk]

You must take into account the direction of tension when choosing the size of an eye..
All eyes are far stronger when tension is straight away from the threaded shank then when at 90° to it.
Then if the choice is for a tight space you may have to use a smaller one then you otherwise would.
With this in mind.
Generally speaking, other specifics may change a choice for a certain application.
I use-
1/4" Eye's on 3" Airframes.
5/16" Eye's on 4" Airframes.
3/8" Eye's on 6 & 8" Airframes.
Years ago I used smaller, but if the application will allow for a sideways tension, worse in a shock, then go slightly heavier.
3" Airframe with a 54mm mount, my attachment point on the top centering ring there isn't room for a 1/4" Eye,
I use a 3/16" eye with no fear, you cant have any sideways tension..



This is exactly what must be understood.
If the tension is straight away, then the threaded steel eye with steel washers spreading the load as much as possible,
the steel is stronger than whatever it's mounted to. This point isn't a guarantee, but will prove correct 98 or more times out of 100..

Teddy

 

[troj]

Listen to Teddy. There are a lot of aspects of recovery that Teddy factors into his recommendations and products that are easily overlooked. Those are details that matter.

-Kevin

 

[Onebadhawk]

Lol,
Thank you Kevin..

Teddy