Prop shaft nuts

[ABoatGuy]

I'm working with a vendor who insists that on a twin installation the left turning prop should have right hand threads and the right turning prop should have left hand threads. This is on a normal SAE taper keyed shaft.

I can't think of a good engineering reason that a properly installed fitted key, installation would loosen based on the direction of the threads. I can't find any standard that suggests this is a requirement.

And I can think of several practical reasons why it would be an annoyance for owners (sourcing large diameter LH nuts, two spare shafts instead of one, etc.)

Does anyone have experience with props coming loose due to LH/RH nuts?

Thanks

 

[Carteret]

Double nut with cotter pins and there is no issue.

 

[gonzo]

I have never seen left and right threads. If they came loose as the vendor claims, they would come off in reverse. It makes no sense.

 

[JSL]

Put on the nut (thin one) and then the lock nut (thick) plus a cotter pin and you are fine.

 

[Mr Efficiency]

This is just nuts. Maybe the vendor had a screw loose ?

 

[michael pierzga]

Imagine the poor engineer who pulls the props. No many are anticipating counter rotation.

 

[CDK]

Using different threads is the old fashioned line of thinking.
On a tapered shaft and key, the only counter clockwise force acting on the nut is the friction of the surrounding medium. A locking ring with one or two lips bent against the nut is the normal way to secure it.
Early automotive wheel drive shafts had different threads on each side, modern ones have a collar on the nut that is pinched or otherwise deformed to prevent turning loose.

 

[michael pierzga]

Using different threads is the old fashioned line of thinking.
On a tapered shaft and key, the only counter clockwise force acting on the nut is the friction of the surrounding medium. A locking ring with one or two lips bent against the nut is the normal way to secure it.
Early automotive wheel drive shafts had different threads on each side, modern ones have a collar on the nut that is pinched or otherwise deformed to prevent turning loose.

What is the name of the locking ear washer for nuts ?

King and queen washer ?

And why cant the second locking nut be a pelleted nut. I hate drilled shafts and drilled nuts....the thread may get burred and when a new prop is fitted the hole no longer works.

How many times have i seated a component only to find that i have put the nut on upside down of pickup the drilled nut for component A when installing component B.

Pain in the butt

 

[FAST FRED]

>I have never seen left and right threads.<

On boat shafts , however it was common on bus and truck wheel nuts 50 years ago.

 

[CDK]

What is the name of the locking ear washer for nuts ?

King and queen washer ?

I have no idea Michael, not in English, not in my native language. I've seen several variants, like a washer locked in a key way, lobes on the outside, or the thing Mercury uses, with a hexagonal seat for the nut.

 

[gonzo]

I had an early 90's Leyland DAF in the UK that still had left and right threads on the wheel studs. It makes no sense since the load is axial. There will never be any torque from the wheel. Likewise, the torque on a propeller is all absorbed by the key and the friction on the taper.

 

[PAR]

It's called a tab washer . . .

 

[SamSam]

This is just nuts. Maybe the vendor had a screw loose ?

If so, you'd want to bolt from him as soon as possible.

 

[DCockey]

"pelleted nut" Is that another name for a "castle nut".

 

[michael pierzga]

Pell-it. Is somekinda trademark for self locking fasteners.

You see them on pieces of equipment assembled by robots

http://www.ndindustries.com/pell-it.php

The nut or bolt has a hole bored thru and a nylon or other material pellet inserted into this hole