Prop taper.

[Jacq]

Hi,

Could anyone help me work out the taper on a prop?

Dimensions I have are: SHAFT DIAMETER: 50.8 mm. / SMALL END: 41 mm. / TAPER LENGTH: 146 mm.

I really need it in imperial. 50.8 equals 2”.

What I need to know is this 1:12 or 1:10?

Thanks.

[nb Innisfree]

Hi,

Could anyone help me work out the taper on a prop?

Dimensions I have are: SHAFT DIAMETER: 50.8 mm. / SMALL END: 41 mm. / TAPER LENGTH: 146 mm.

I really need it in imperial. 50.8 equals 2”.

What I need to know is this 1:12 or 1:10?

Thanks.

 

With those measurements I make it 1:15.8, not very likely, maybe your measurements are not accurate. Imperial shafts are 1:12 and metric 1:10 so I would guess 2" shaft would be 1:12. Equivalent metric shaft would be 50mm.

[WotEver]

With those measurements I make it 1:15.8

I make it 1:14.9, but that's just as unlikely.

 

Tony

[Jacq]

Could you tell me the formula to use please

[bottle]

the length of taper (146) divided by the difference in diameters (50.8- 41 = 9.8)

 

146/9.8 = 14.89

 

therefore taper is 1:14.89.

Edited April 26, 2011 by bottle

[RLWP]

Hi,

Could anyone help me work out the taper on a prop?

Dimensions I have are: SHAFT DIAMETER: 50.8 mm. / SMALL END: 41 mm. / TAPER LENGTH: 146 mm.

I really need it in imperial. 50.8 equals 2”.

What I need to know is this 1:12 or 1:10?

Thanks.

 

That taper length seems very long

 

Richard

[Timleech]

That taper length seems very long

 

Richard

 

I think the American (SAE) standard taper is 1:16, a bit of googling will tell you.

Tapers are very difficult to measure accurately with simple gear.

 

 

Tim

[RLWP]

I think the American (SAE) standard taper is 1:16, a bit of googling will tell you.

Tapers are very difficult to measure accurately with simple gear.

 

 

Tim

 

Nearly 150mm, getting on for 6", is still quite a long taper. How deep is the hub of the prop?

 

Richard

[nb Innisfree]

I make it 1:14.9, but that's just as unlikely.

 

Tony

 

Correct!

[Timleech]

Just remembered, SAE tapers are defined from the small end.

OP says SHAFT dia is 2", but doesn't give prop bore at large end.

If you look here and find 2" shaft, it gives small end 1.625" (= 41.275mm) and length of taper 5.75" (= 146mm).

Eureka!

 

Tim

[bottle]

So now we have a taper of 1:15.3

 

which is quite close to the 1: 14.89

 

I originally calculated.

Edited April 27, 2011 by bottle

[RLWP]

So now we have a taper of 1:15.3

 

which is quite close to the 1: 14.89

 

I originally calculated.

 

That gets you a Gold Star and a smiley face for being good at sums

 

Richard

[Timleech]

So now we have a taper of 1:15.3

 

which is quite close to the 1: 14.89

 

I originally calculated.

 

Whence cometh your 1:15.3?

 

SAE prop taper is defined by the small end and the taper (1:16), the large end is derived from the length and the small end, the large end of the prop taper is likely to be less than full shaft diameter.

 

Tim

[bottle]

I was not calculating/defining the SAE taper.

 

All I did was calculate the taper from the figures given.

[Timleech]

I was not calculating/defining the SAE taper.

 

All I did was calculate the taper from the figures given.

 

Fair enough, I haven't done the sums myself.

It seems to me that SAE taper is the most likely though, unless it's a one-off.

 

Tim

[bottle]

Going back to the original post, question.

What I need to know is this 1:12 or 1:10?

 

No, it is in the region of (calculated) 1:15 but as Tim said it is probably 1:16

 

Better measuring and the help of someone that knows, is the best way.

[Jacq]

Thanks all,but now my head hurts.