Sheer Pins

[MikeSModerator]

Flying my Intimidator 4 on an L1115.

What would the suggested size of nylon screws for the nose cone
and booster?

It has been suggested to put three at each location.

thanks MikeS

[Christopher Dreher]

I used (3) 4-40 on my Intimidator 5. With a 4 inch airframe you could probably use 2-56 if you wanted. According to Missileworks it takes 35 lbs of force to shear a 4-40 and 25 lbs to shear a 2-56 nylon screw.

[edwardModerator]

What are the weights of the components you are restraining? On my 2.5″ diameter L3 rocket I had to step it up to 6-32 shear pins to keep the nose from deploying when I separated the rocket. I’d start with 3 4-40’s and then do some ground testing.

I considered my successful when I could shear the pins and get the shock cord to deploy 85%-90% length.

Edward

[MikeSModerator]

thanks

[Steve JensenParticipant]

Mike,

I listed my shear pins on my Intimidator on an earlier response. Two on the fore and aft, 4-40’s, worked flawlessly.

My Raven data demonstrated separation at apogee and main deployment went as planned.

The Intimidator has big fins and drag. I worried more about premature separation of the aft at speed. I plan on using the same set up again for my next launch that will hit mach on my Intimidator (KMAG).

We’ll see how it works…

[MikeSModerator]

I ordered some from Missile Works. Will be here in a few
days.

Thanks.

[Warren B. MusselmanModerator]

My rule of thumb – 29mm, little pieces of plastic; 38mm and 54mm 2-56 screws. 3″, 4″ 4-40 screws. Anything about that, break out the 6-32 screws. Bigger than 6″, 10-24… always nylon of course.

[BEAR]

Miek, For what it is worth, you should be able to get 4-40 nylon screws at a good Ace hardware store. If you need smaller, I can get 2-56 at the screw supply here in Fort Collins. Let me know and I can get some for you, we can meet up and exchange them. I know it is not cost effective, but it does save time.

[Author]

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