Safety Spinner Nut

[Goose is the real hero]

Morning All,

 

After some advice on spinner nuts please  -I haven't used one before and I am a little stuck! 

 

1. Does the nut simply screw on to the crankshaft without any retention or locking?

 

2. What are the holes at the front of the nut for?

 

3. I seem too have a few mm between the nut and prop when the nut is tightened as far as it will go (please see next question!) - should I be using the prop washer supplied with the engine to mitigate this?

 

4. The nut will only tighten a certain amount before it is simply turning the engine over instead of getting any tighter - I guess this isn't normal but how is it mitigated?

 

Any help would be much appreciated.

 

Cheers,

Goose. 

 

NB. Sorry, the site doesn't seem to like my photo upload but hopefully the above makes some sense anyway...

 

[J D 8]

  Not heard of safety spinner nut, are you meaning the safety prop nut system that is normal found on four stroke engines ?  Or is it something to do with the type of spinner that has a long screw from its point to fitting in end of crank shaft ? Supplied prop washer should be used no matter what other fittings are attached.

[jrman]

I think he means a rounded (domed) nut. The washer should be used between nut (of whatever type) and the prop.

The holes are for a "tommy bar" to tighten the nut with.

Edited July 6, 2021 by jrman
Extra data

[Nigel R]

I've not come across a domed prop nut that does not have enough thread in the nut. But if you do, you could always stick the normal nut on first and use the domed nut as a locknut.

[Chris Walby]

18 minutes ago, Goose is the real hero said:

Morning All,

 

After some advice on spinner nuts please  -I haven't used one before and I am a little stuck! 

 

1. Does the nut simply screw on to the crankshaft without any retention or locking?

 

2. What are the holes at the front of the nut for?

 

3. I seem too have a few mm between the nut and prop when the nut is tightened as far as it will go (please see next question!) - should I be using the prop washer supplied with the engine to mitigate this?

 

4. The nut will only tighten a certain amount before it is simply turning the engine over instead of getting any tighter - I guess this isn't normal but how is it mitigated?

 

Any help would be much appreciated.

 

Cheers,

Goose. 

 

NB. Sorry, the site doesn't seem to like my photo upload but hopefully the above makes some sense anyway...

 

Hi Goose,

 

The old wife's tail of double nutting requirements on all ic engines is not necessarily required or approved by the some manufacturers 

1. Laser and OS engines come with a single standard nut, Laser Engines do NOT recommend double nutting, but using the correct installation procedure is sufficient including regular checking
2. If this is a nut for holding a spinner cone on (center hole in the cone) then that's what its for.
3. Prop washers should be used
4. Either us a standard nut or ensure the prop nut spinner version is not bottoming on the reduced section of the nut

Hope that's clear, if not please ask more questions

 

PS How do you double nut when there is not enough crankshaft thread showing + what about engines that use a bolt up the crankshaft, how do you double nut that?

 

[Goose is the real hero]

Thanks for the replies guys, I did indeed mean the domed nut - Great Planes call it a 'safety spinner nut' although I am unsure where the 'safety' part of this comes in. 

 

Frustrating that I cannot upload photos as this would be a a lot clearer - I think that using the prop washer and then tightening the nut using the holes (thanks Jrman) may resolve many of my issues, will try again with the photos once I have done this as it is not something i want to get wrong for obvious reasons. 

 

Thanks again,

Goose

[leccyflyer]

The safety part comes from the dome preventing the exposed shaft of a model engine becoming a very effective trepanning tool, in the case of flying into somebody's head. IIRC the BMFA used to have a minimum radius for domed nuts and spinners.