Shear pins and plastic nose cones (LOC style nose cone)?

[supertaco]

I plan on using shear pins for the first time in a few weeks. However, I have concerns about using plastic shear pins with a plastic nose cone shoulder that might have a similar elastic modulus to the shear pins. In other words, I have concerns about binding or nose cone damage. Can folks with experience provide some insight the matter?

Thanks!

 

[tim cubbedge]

I personally have not had any issues but this guy makes a small mod to his NC:
https://www.rocketryforum.com/threads/blue-bruiser-sky-pirate-v3-0.164660/page-3#post-2120539

 

[supertaco]

I saw that and it looks impressive. But, as a professional lazy guy, I plan to just try the shear pins in the plastic nose cone as I now have one data point (you ) that it works for. I appreciate the quick response!

 

[heada]

Depends on the pins. I've done nothing and the cone was fine, I've epoxied brass tube into the cone and I've epoxied stainless shim stock to the cone and tube. It all depends on the number, type and size of the pins.

 

[supertaco]

Depends on the pins. I've done nothing and the cone was fine, I've epoxied brass tube into the cone and I've epoxied stainless shim stock to the cone and tube. It all depends on the number, type and size of the pins.

Thanks, heada! Good info!

 

[tim cubbedge]

I think a lot also depends on how tight a fit the NC shoulder is in your airframe.

 

[Crazyrocket]

I use 1/16" diameter nylon rod all the time in plastic nose cones and cardboard tubes. I put CA on the tube to toughen it up. I do check periodically to make sure the hole is not opening up. If it does, I rotate the cone cone and drill new holes.

 

[supertaco]

I use 1/16" diameter nylon rod all the time in plastic nose cones and cardboard tubes. I put CA on the tube to toughen it up. I do check periodically to make sure the hole is not opening up. If it does, I rotate the cone cone and drill new holes.

I like that. Thanks!

 

[teepot]

I us brass blades in a recess in the BT or if the tube walls are thin on the outside of the tube.

 

[Nytrunner]

The only plastic nosecone that troubled me with pins was the thin estes pro-series II cones. It was thin enough that it twisted and didn't shear the pin.

If its soft plastic and the shoulder wall is thinner than the pin, that's probably a red flag. Normal high power cones work fine.

 

[crossfire]

We used to use styrene rod as shear pins. It works very well

 

[Crazyrocket]

Ok. I mistyped and stated nylon rod. But Crossfire is correct and you should use styrene rod. That is what I use. Sorry for the confusion (if any).

 

[supertaco]

Ok. I mistyped and stated nylon rod. But Crossfire is correct and you should use styrene rod. That is what I use. Sorry for the confusion (if any).

I have some styrene rod and some of those nylon shear pins (2-56 X 1/4" long Round Slotted Machine Screws) from Apogee Systems. No confusion, but thanks!

 

[jrains]

I have used both 1/16” styrene rod as outlined in the Mike Westerfield’s book and nylon screws with no problems. I added brass shims to the inside of the cardboard tube. Note, styrene rod works well, just moved to nylon screws as I was shamed to do so.

 

[Crazyrocket]

I used both as well. If the rocket is fairly light, I will use styrene rod. Heavier rockets I use 2-56 nylon screws. If I have a heavy cardboard rocket, I will also put in brass shims as well. Really depends on the rocket.