Correct size pulleys for 9" 6 speed

Before building the drive setup for my old 9",
I would like all of your views on the correct
size motor (1725 or 1120, 1/2 hp or 3/4) and the correct driving and driven pulley sizes for overall cutting speeds. I am considering buying a
1725 1/2 motor with a 2" driving pulley and a 12"
sheave pulley, does this sound right? Or should the driving pulley be larger for more surface contact, which would increase the sheave size.
Are the slower speeds more important and should I size toward that end of the speeds.

Thanks
Steve Wells

On my 9" I built up the drive as follows:

Motor 1350 rpm 1hp
motor pulley 2 1/2 "
countershaft pulley 10"

This gives pretty well exacly the
'right' spindle speeds according to the SB
specifications.

I used 1/2" v-belt and the friction is fine.

I also worked out that a 4" motor pulley and 9"
countershaft pulley is about right for the high
range, and the belt length comes out about the same too.

In the light of experience, I'd think a 3/4 hp motor was plenty, and (if you can get the pulleys)
3/8" v-belt would have been better.

Actually, I turned the motor pulley (as a double
pulley) myself out of Aluminium bar, but I think
the sizes above are standard.

All the best

Nick,
With your back gears engaged and disengaged, what are your spindle speeds? I would like to make sure I can turn in the 30-100 FPM range.

Steve Wells

According to the catalogue, the combinations
are:

Backgear out 658 370 212 rpm
Backgear in 127 72 41 rpm

Timing mine on the slowest pulley, backgear in
come to near enouth 49 rpm, so I'm actually a bit
faster than the specification.

All this applies to a 1943 9" with the three
pulley flat belt spindle drive. The 4 groove
v-belt spindle drive is definitely different,
and newer models might be but I wouldn't expect
so.

I did mine by lashing up an arrangement which
worked using shop bought pulleys, and then used
the lathe itself to turn the motor pulley to the
size I wanted for the final version of the drive.
It was pretty simple really.

I've just realised that my motor speed won't be
available to you since we're on 50 cycle
electricity in the UK and yours is 60. It's easy
enough to do the calculations though for a given
motor speed.

Nick
Nick

With the motor and pulleys suggested
in the original post I estimate the
spindle speeds would be about:

557 313 180
108 61 35

Nick