Piano wire

[blueskyracer]

Ok I want to get some piano wire for shear pins.. Where do you get yours and what is the part number I am looking for. I went to MCMaster Carr and they have 1065 or 1080 Carbon steel in a .187 size one foot lengths.. Is that what I need.. I have tried every other shear pin material known to man with no luck on my 44's..

[25xs]

Shear pins...

Hold tight. Someone will chime in with the aircraft rivet part number from Aircraft Spruce & Specialty in/near Griffin, GA

[ZUL8TR]

shear pins

Ok I want to get some piano wire for shear pins.. Where do you get yours and what is the part number I am looking for. I went to MCMaster Carr and they have 1065 or 1080 Carbon steel in a .187 size one foot lengths.. Is that what I need.. I have tried every other shear pin material known to man with no luck on my 44's..

When you shear a pin have you been getting stuck props on the shaft? Regardless of Yes or No put high temp wheel bearing grease with moly additive on the prop shaft before putting prop on. It is not fool proof but if the engine is shut down quick the grease does help prevent seizure and galling the shaft. Worked for me.

As far as the shear pin issue you are having have you checked the squareness of the prop rear contact area relative to the nut surface when tight. I had some props that were not perfectly 90 degrees relative to the shaft. With this missalignment the pin is put under unequal shear when tight and the prop is slightly off kilter depending on the prop to shaft clearance and degree of out of square the prop contact surface has with the nut.

Also do you use a lock washer and the nut? Is the nut a nylock type. I found the nylock nut alone when about 2 threads of the shaft were exposed at the nut top worked for me. Adding a flat washer acts like a shim and could provide additional bearing on the prop surface if needed but still leave about the 2 thread exposure at the nut top.

The harder pins are a possible solution but they may be so difficult to shear that the internal prop gear pin might go first? Assume that you are using the standard Merc quicki foot.

[JBM]

Mike, I have #8907K18 written down from another thread, altho I have never bought any.

[blueskyracer]

Thanks John. That was a good number and wire is ordered from McMaster Carr

[modhydro]

Shear pin theory

I have been in discussions about this in the past.

I have seen guys torque down a shear pin so hard that it deforms under the load from the prop nut. This is about guaranteed to shear when you run it. Think about what the pin is resisting; the prop motion relative to the propshaft. A pin only has a certain amount of strain it can take before it becomes a three piece unit instead of the single part you put in. Overtorque on the nut uses a percentage of its strength up before you even start the engine. The more propnut torque the less prop load it can withstand.

I put on the prop with just enough to snug the pin in the hole and put a small piece of music wire on the clevis pin. This leaves virtually all the load carrying capability for the prop load.

Even with light nut torque, the 3/16" pin is pretty much maxed out on a good D. I wound up drilling mine to 1/4" and have used the same pin since then. No more one-time use for the 3/16".

Another factor that can make it worse is if there are chips around the shearpin hole in the propshaft. Sometimes this leaves a sharp edge that makes the situation worse.

Just another guys thoughts.

Steve Roskowski

[john527]

you ordered the same ones I ordered this morning, you should have no problem with these, when you cut them to length, don't overheat and put a nice chamfer on both ends!

[blueskyracer]

you ordered the same ones I ordered this morning, you should have no problem with these, when you cut them to length, don't overheat and put a nice chamfer on both ends!

Thanks will do.. I have used my one foot with the 1/4 hole and I have used the same two pins for one season..No problem but I have a couple yamato feet I would like to try some props on again.. Cant drill a 9/16 shaft to 1/4 so I need to work with some good pins..I will remember to use less torque.. I always use anti seize on the shaft prior to install of prop and the holes are chamfered and very smooth

[1100-one]

shear pins

Both John 527 and Steve gave excellent ideas and tips. I also have a few new Konig shear pins from Litzell I will give you to try if you like never sheared these when I ran. Years ago the late Doc Collins gave me shear pins he had they were allen bolts. I bought some and I may still have them not sure I dont remember what grade though but they held up on a merc 6 cyl and my 44. They had a small locknut as well

Just some thoughts for ya

Todd

[blueskyracer]

Both John 527 and Steve gave excellent ideas and tips. I also have a few new Konig shear pins from Litzell I will give you to try if you like never sheared these when I ran. Years ago the late Doc Collins gave me shear pins he had they were allen bolts. I bought some and I may still have them not sure I dont remember what grade though but they held up on a merc 6 cyl and my 44. They had a small locknut as well

Just some thoughts for ya

Todd

Thanks Todd I will keep you in mind if I have any more trouble,, I even tried a smooth shank Titanium bolt from Boeing and it failed after a heat and one lap..

[Guest]

Pins

http://www.aircraftspruce.com/catalo...ispinsgrid.php

We have been using MS aircraft pins with a 3/16 hole for years. Never shear them and you can put a small cotter pin in the hole that extends through the prop and you will never throw them. Another aircraft hardware option is the 3/16 NAS bolt with a GB series nut.

Alan

[Bill Huson]

back when I had a hobby shop I used 3/16" piano wire from my supplies - K&S rack fulla wire next to the K&S rods, strips, and sheet, including shim stock. Ah yes those were they days - when folks actually built from itty bitty pieces the airplanes they were going to fly. . .

[Bill Huson]

oh yeah, cut the wire with a Dremel 409 disk - nickname "dangerous disk" `cause they would self destruct if you got a hand twitch.

[blueskyracer]

oh yeah, cut the wire with a Dremel 409 disk - nickname "dangerous disk" `cause they would self destruct if you got a hand twitch.

Thats what I usually use and you are right Bill it is easy to EAT one if you know what I mean

[form-e one]

mike get hold of rick keller he orderd us our 1/4" shear pins under my rude they hold up fantastic under my 9" dia props,,,, no need for wire just good lock washer ,,, no worries