hi,
thanks for everyone's help so far.
i'm trying to calculate what size pulley i'll need and what should be the
speeds at the chuck.
i visited several "star" brand lathe websites, found one with an old
catalog. the entry in the catalog for the jackshaft they sold for this
lathe to convert it from treadle power to steam power said "...speeded up to
200 rpm." i figure that must mean the maximum recommended speed for the
jackshaft (and hence the input speed for the lathe) would be 200 rpm. so
i've been trying to come up with a pully combination that'll supply the
lathe with (as close as possible) a 200 rpm input speed.

what i've come up with so far...
motor 1725 motor pulley 2" reduction drive v belt pulley 14" (largest i
can find in die cast (=inexpensive), the cast iron pulleys go for between
sixtysomeodd bucks ~ $140 (w/o collar!)) with formulas i found on the web
that makes 244 rpm for the input to the cone pulley reduction. the
reduction cone pulleys are 4.5"/5.625"/6.5625" the cone pulleys on the
lathe are 5.4375"/4.3125"/3.1875" that, according to my calculations, with
a 244 rpm input, will produce, at the chuck, 20.17/318.25/502.34 rpms. it
seems unbelievable there's such a huge difference in the speeds between #1
and #2. is 20 rpm (and that's even w/o back gears) too slow?! i don't even
KNOW what it'll be in back gears. is 502 rpm on the highest speed too slow
too? i'm a little concerned about speeding this lathe up too much, it has
bronze bearings (and they don't look perfect, there is some scoring.)

b.w.

You slipped a decimal place on your low cone calc. It should be a
reduction of 4.5/5.43= .82 times imput speed of 244 rpm would be 202
rpm, not 20.2 rpm.

7:1 reduction using 'V' belts is pretty much a pain due to the huge size
of the driven pulley. As big $$ as you already found out. You can get
some weld-up pulleys sold in the farm stores that consist of a suitable
hub (various standard bores, a couple of standard external diameters)
and your choice of stamped steel pulley. $6 for the hub, $20 or so for
the 14" pulley,

I think I'd speed it up to run at something like 800 rpm top spindle
speed. This would let you run a 1/2 hp 1720 rpm motor with a 2" drive
pulley and an 8 inch driven pulley. This would move your lowest direct
drive speed up to 350 rpm. Back gears are usually around 6:1 or so,
figure your lowest speed in back gear at 60 rpm.

William Wixon wrote:
hi,
thanks for everyone's help so far.
i'm trying to calculate what size pulley i'll need and what should be the
speeds at the chuck.
i visited several "star" brand lathe websites, found one with an old
catalog. the entry in the catalog for the jackshaft they sold for this
lathe to convert it from treadle power to steam power said "...speeded up to
200 rpm." i figure that must mean the maximum recommended speed for the
jackshaft (and hence the input speed for the lathe) would be 200 rpm. so
i've been trying to come up with a pully combination that'll supply the
lathe with (as close as possible) a 200 rpm input speed.

what i've come up with so far...
motor 1725 motor pulley 2" reduction drive v belt pulley 14" (largest i
can find in die cast (=inexpensive), the cast iron pulleys go for between
sixtysomeodd bucks ~ $140 (w/o collar!)) with formulas i found on the web
that makes 244 rpm for the input to the cone pulley reduction. the
reduction cone pulleys are 4.5"/5.625"/6.5625" the cone pulleys on the
lathe are 5.4375"/4.3125"/3.1875" that, according to my calculations, with
a 244 rpm input, will produce, at the chuck, 20.17/318.25/502.34 rpms. it
seems unbelievable there's such a huge difference in the speeds between #1
and #2. is 20 rpm (and that's even w/o back gears) too slow?! i don't even
KNOW what it'll be in back gears. is 502 rpm on the highest speed too slow
too? i'm a little concerned about speeding this lathe up too much, it has
bronze bearings (and they don't look perfect, there is some scoring.)

b.w.

thanks Roy! jeez, i did that calculation like 5 times and kept coming up
with the same answer, must've kept making the same mistake over and over
again. red faced again (i went to art school, what can i say)

(more below...)

"RoyJ" wrote in message
k.net...
You slipped a decimal place on your low cone calc. It should be a
reduction of 4.5/5.43= .82 times imput speed of 244 rpm would be 202 rpm,
not 20.2 rpm.

7:1 reduction using 'V' belts is pretty much a pain due to the huge size
of the driven pulley. As big $$ as you already found out. You can get some
weld-up pulleys sold in the farm stores that consist of a suitable

i've used those (large diameter) two piece spot welded stamped sheet metal
pulleys in teh past but couldn't find them on-line and figured they must've
stopped making them.

hub (various standard bores, a couple of standard external diameters) and
your choice of stamped steel pulley. $6 for the hub, $20 or so for the 14"
pulley,

I think I'd speed it up to run at something like 800 rpm top spindle
speed. This would let you run a 1/2 hp 1720 rpm motor with a 2" drive
pulley and an 8 inch driven pulley. This would move your lowest direct
drive speed up to 350 rpm. Back gears are usually around 6:1 or so, figure
your lowest speed in back gear at 60 rpm.


thanks very much Roy for the suggestions, recommendations, advice. (!)

holy crap i found some nice (relatively inexpensive) large diameter cast
iron (!) pulleys at www.surpluscenter.com. example,
http://www.surpluscenter.com/item.as...tname=electric
and they have some (nice?) electric motors there too, reversible, etc.
was going to ask you guys for suggestions on where to get a nice reversible
electric motor, i was hoping for a honking big 2 hp motor but maybe (with
teh prices for 2 hp) i can settle for something smaller grin.


b.w.

William Wixon wrote:


what i've come up with so far...
motor 1725 motor pulley 2" reduction drive v belt pulley 14"
(largest i can find in die cast (=inexpensive), the cast iron pulleys
go for between sixtysomeodd bucks ~ $140 (w/o collar!))

Willam
If you determine for sure you need a big pulley, I have one on a
lathe I'm parting out that is probably 12" OD, single groove, takes a
1/2" belt. It is mounted to the left end of an Atlas 10" spindle, so
it's ~1.5" ID. Cast iron, good condition.

email me privately if interested.

rex at txol.net