Replies

1. 
   mike4244 | Jun 07, 2005 12:00am | #1

   Multiply the size of the pulley on the motor by the motor rpm, example  2" pulley  x 1725 =3450 rpm. Then divide this by the pulley on the shaft, example 3" pulley divided into 3450 = 1150 rpm's.

   motor pulley size  x   motor speed  ;   divided by speed wanted = pulley size needed.

   example 2" x 1725=3450  ;  430 rpm's wanted = 8" pulley

   mike

1. 
   Steinmetz | Jun 07, 2005 01:07am | #3

   Mike, build a 'jackshaft' and use two 4 cone step pulleys (one on motor, one on jackshaft, another from shaft to lathe.(Can be multible)
   Now, you'll have plenty of choices. Stein.

   Edited 6/7/2005 11:34 am ET by steinmetz

2. 
   WillGeorge | Jun 07, 2005 04:22am | #4

   I think Mike got that out of a old Brown and Sharp book!  Go mike...

   Do NOT forget.. Power changes with pulley speeds... As I remembers... No I do not know the formula!

   Edited 6/6/2005 9:24 pm ET by Will George

1. 
   Jellyrug | Jun 07, 2005 07:13am | #5

   As speed goes up, the torque comes down and the power stays the same.

1. 
   WillGeorge | Jun 07, 2005 10:39pm | #7

   Jelly.. I'm old I THINK I wanted to say TORQUE!  Thanks fer remindin' me!

2. 
   Jellyrug | Jun 07, 2005 12:11am | #2

   S = speed of motor pulley rpm

   D = diameter of motor pulley in units of your choice

   D1 = diameter of intermediate pulley driven by motor pulley

   D2 = diameter of intermediate pulley driving lathe spindle

   D3 = diameter of lathe pulley

   S2 = speed of lathe spindle

   S2 = (S x D x D2)/(D1 x D3)

    

    

3. 
   philip | Jun 07, 2005 12:41pm | #6

   Flonji,
   If you go the jack or lay shaft route, you can get an added bonus of more speeds both slower and faster by using a pair of 3 or 4 step conical pulleys-these are even made right here in sunny New Zealand. You don't say what the existing set up is .
   I modified my Wadkin lathe by adding a lay shaft with matched step pulleys at headstock , lay ends and motor- got much more versatility e.g for biggish sanding disk on outboard and with slowest speed can turn table tops with the use of an independent tool rest.
   If you are interested I can send pictures.

1. 
   flonji | Jun 07, 2005 11:16pm | #8

   Good morning.

   Will first show my ignorance. I do not know the meaning of 'lay' or 'jack shaft'. Am guessing it would be the middle pulley of a set of three.

   I have built an extension so that I can now turn a 2.5m length. I presently have a 1450rpm motor with 2only 4step conical pulleys. My plan is to reverse the motor pulley and insert another 4 step inbetween.( Will have to construct a new frame to hold it all. )

   Now that I have the maths I can now determine what size pulley to look for.

   Would be great if you could post pics.

   Many thanks for the info.

   have a smile                               flonji

4. 
   philip | Jun 08, 2005 09:55am | #9

   Greetings Flonji,
   Herewith pictures of lathe pulley set-up using a lay or jack shaft-which is simply the intermediate shaft. It is the one at the foot of the lathe,driven by motor and then driving the headstock shaft.
   The motor used to be in that well at the foot of lathe, and with a pair of 4 step pulleys gave 4 speeds-this was fine but I wanted more slower speeds and some faster ones. Slow for outboard turning of large diameters like table tops and a sanding disk-faster for polishing wheels etc.
   I don't know your existing set up so can't say how easy or practical it would be to add another shaft-it may be easier than mine was. It was certainly worth doing.
   You can also see an independent tool rest on one side- I just shift it to the opposite side (heavy) after unbolting the standard tool post,which you can see under the sanding disc-a mighty useful item.
   Hope this encourages you to go for it.

   
1. 
   flonji | Jun 09, 2005 12:52pm | #12

   HI.

   Many thanks for the pics and for increasing my knowledge re a jack shaft. I can see where you would have had problems with putting yours in.

   I have a big advantage in that my motor is completly independant of the lathe. When I purchased it 35 years ago it consisted of a headstock, sq section bed, tailstock and toolrest. I had to build a frame and attach a motor. This is out the back on a hinged plate for an easy change of belt and with a bottom support so that the belt does not take the full weight of the motor. Still the original motor!!.

   My idea at prresent is to drop the motor and hinge it to the bottom lateral  frame member, build a cage for the jack shaft and attach that to the vertical frame, and have some kind of foot operated cam under the motor to reduce the belt tension for easy change.. My other major advantage is that I have a mechanical engineer son in law living 5 mins away**. A constant supply of firewood brings a good return.

   Sorry I cannot send you any pics, have still to learn the art of scanning.

1. 
   Jellyrug | Jun 09, 2005 07:02pm | #13

   Flonji,

   Have you looked at a Reeves pulley, here?

1. 
   flonji | Jun 10, 2005 11:37pm | #14

   Hi.

   I had a similar setup on my very first lathe and from memory at the slow speed end it took the easiest option and just slipped the belt. Will go with the lay shaft and use your maths

   Many thanks                                     flonji.

2. 
   philip | Jun 11, 2005 02:06am | #15

   Engineer son-in-law---- ah well there you are then.
   Re quick release for belt tension- that is a mighty convenient thing to have: make it part of the "specifications".

5. 
   BobHowell | Jun 08, 2005 01:18pm | #10

   Jack shaft speeds.

   I did this in 97' for a secondhand(30yr old) Delta lathe. I got a Delta catalog and looked up pully options from Delta. In looking at the speeds listed for different pullys offered and doing the math, I noticed it was not coming out as I learned in highschool. I called a local industrial supply house and here's what I got.

   For a cone v belt pully you have 2 diameters, inside and out side. The belt rides on the sholders of the v and you use some number between the inside and outside number. Delta uses 1/2" A size belts for its lathes and the speeds come from adding about 1/4 to 3/8th to the inside diameter. I got the smallest cone drive pully available and it had 1.75 as its smallest size. It cut the lowend down from 950 to 650, but traction became a problem when roughing out 12" bowl blanks. They would stall. I switches to a red link belt which helped.

   I still wanted slower speeds of about 300 and found the cost of a jackshaft to be about$150 plus a reworking of the motermount and drive setup. I opted for a variable speed DC drive for about $350 from a guy in Organ or Washington State. He advertizes in the AAW Journal. You lose tourqu at low speeds but I have no problem roughing out blanks at about 200-300. I am still using the 1.75" drive pully on the cone I origionally purchased. I can dig out details if you need them.

   Bob Howell

1. 
   BobHowell | Jun 08, 2005 01:33pm | #11

   I notice now you are DownUnder so US names and sources are of little use. The math will be the same if you have size A, V-belts. I don't know conversions. Just find a industrial supply house and get a catalogue. they will give the speeds available from diferent offerings. You can then what effective sizes your combo works out to be.

    

   Bob Howell

2. 
   WillGeorge | Jun 11, 2005 07:01pm | #16

   I can not get a hold of the guy anymore so I can't ask him.. He had as many lathes as I have empty beer cans... Wood and metal..

   He used some sort of transmission and a electric motor... Sort of like a right angle box with a shaft and a gear selector knob...

   All I can say he would always say how good they were on torque..

   As I remember he ALWAYS went to Granger... Try to look there for stuff. Do they have a web page???