What's new
What's new

Is a counter shaft *MASS* pulley needed with VFD setup

sandman-pi

Plastic
Joined
Jan 14, 2020
First order of business to say hello to everyone and state I finally got a lathe.. 😇 .. 😍.. 😎.. 🕵 ..

Maybe not a 10EE but.. A SB 9.. Its a catalogue 382-R / 4.5 ft bed / seems in good shape / bakelite paint 99% intact / metal tags as new / gears do have grease caked on.. Well post pics.. I am doing the cleaning / new felt / mobil machine oil etc etc..

I bought a new 3/4 HP 3 phase 1140 RPM and have a VFD.. QUESTION on should I use a V belt or serpentine belt??

Pulley setup will be close to 1:1 ratio - or may bump the pulley sizes to get 1200 - 1300 rpm... Or whatever the lathe max RPM should be.

REAL question is on need of some form of MASS counter shaft pulley for rotational issues..

This is my first lathe and have no real experience with all the pulley gizmos .

Thx in advance for any notes / advice / input ..👓
 
Well darn .. Not that I really know what speed I really need.. Having said that - the VFD conversion idea somehow went from simple to confusion.. The counter shaft pulleys for one.. And the only thing missing.. I have the overhead mounting parts - or at least most of them..

So its either the VFD route or DC motor lol.. SMH
 
Johnoder thx for quick note and info.. You sent me down the internet highway 5 minutes after you posted..

Forgot to let all know I am on a cell and dont pay attention to grammer etc etc.. I used to -- but more times then not i would loose everything taking to long .. Hitting wrong key or getting side tracked lol. 😇🕵.. Anyway

Iwan10K will post some pics trmw.. I seem to have the overhead silent drive.. V belt or chain unknown - just for the record.. Maybe the line card will tell me that if i get one..

Which brings a ** QUESTION ** just because😎 and for the knowledge.. The specs on the mass pulley on a 9 horizontal and overhead silent V pulley of the same age .
 
The mass has little to do with it. The countershaft exists to drop the speed to something appropriate for the spindle, and give the operator some speed choices. But, your low speed motor and VFD give you the option to do without the countershaft, if you use a small enough motor pulley. Belt slip will become a problem, so you should run a Poly-V belt and pulley. You'll have the option to overspeed the VFD if you want higher speeds. I routinely go to 90 Hz on my various machines. So, measure the OD of your largest step and divide by 3, and get a pulley roughly that size. You can leave the belt on the highest step and work fine for most tasks using the VFD speed control. Back gear for anything really slow.
 
Kitno455 - you cleared the trees so I can see the forest 😇.. Thx .. No pun intended..

That brings me to my first thought / question on the spindle pulleys.. Which is best, or should I say, which brings fewer issues.. Should I use flat belt, or V belt pulleys? Posting spindle pic for that question.

Posting a few pics of basic parts for the record here / and for maybe finding the few pieces I lack.. So I can have the complete overhead silent setup..
 
Comment on kitno455 last post..

Assuming v belt pulleys all the way around..

As for low speed motors / VFD setup on this series O lathe - you noted divide by 3 - giving 3:1.. I think you are "thinking" 1800 rpm motor.. I cant do 3:1 with a 1140 rpm motor- can I?? Thats a small diameter pulley 😣

Factory max speed 600 rpm rounded off
1140 rpm * baldor motor
Large flat belt pulley on spindle 5"

5" v belt spindle pulley
2.5 inch motor pulley would 540 rpm - 2:1 .. So wouldnt a 3 - 3.25, or even a 3.5" motor pulley be a good compromise on sizing here.. Can always put in a gerneralized limiting speed function on VFD..

Yes / no / maybe / other ?? 🕵
 
Assuming 1140 motor....

5 / 3.5 = 1.43 : 1 = 800 spindle RPM

5 / 3.25 = 1.54 : 1 = 741 spindle RPM

5 / 3 = 1.67 : 1 = 684 spindle RPM

5 / 2.66 = 1.88 : 1 = 606 spindle RPM

Before settling on anything would it not be wise to see just how good spindle bearings are? How good the related lube system is?
I mean the lathe is way past 80 years of age.
 
As for low speed motors / VFD setup on this series O lathe - you noted divide by 3 - giving 3:1.. I think you are "thinking" 1800 rpm motor.. I cant do 3:1 with a 1140 rpm motor- can I?? Thats a small diameter pulley ��

Uhh, 3:1 would yield the same size motor pulley regardless of the motor speed :)

Anyway, as I said before, you'd need to use a Poly-v belt (something like J section) in order to use that small of a motor pulley.

allan
 
just in case....
poly v = *serpentine belt*....so yes, flat belt.:)

im in total agreement on the smaller size motor pulley....keep in mind at 90hz your 1140rpm motor effectively becomes a 1725ish rpm motor....so for motor pulley sizing IMO you should pretent like it is a 1725ish rpm motor since there is no appeciable loss or risk with running at 90hz....while there IS risk of overheating the motor if you run it too slow..assuming you have a fan cooled motor...the fan will slow as the motor slows.

IOW- sizing your motor pulley so you get your max 600rpm spindle speed at 90hz puts you more in a sweet spot to take full advantage of your motor/vfds potential.

this would be suitable IMO....dont know your shaft size but they have others in 1/2" and 7/8" bores too...also in sizes down to 1.5"
https://3bgsupply.com/pulleys-and-sheaves/poly-v-pulley/6j160x5-8-b-b-manufacturing

ps- i didnt work the maths....:)
 
Last edited:
Thx all for the notes..

On poly v belts - I will just say i had wrong type "pictured" when thinking about it.. Now I understand exactly what is meant by that definition.. And the profile type of pulley needed..

On the topic of my vintage machine I am in process of generalized cleaning and "generalized" detail.. Like replacing all felts / using Mobil machine oil, not whatever was on hand at that time .

On the topic of spindle bearings I will be happy take whatever advice for checking the state of them.. Have not touched the spindle.

I will setup a photobucket acct for P.M. use..

Just a ref note: me a R.N... Thats Registered Nurse .. Telemetery / cardiac post surg. .. X Datapoint Corporation, San Antonio Tx.. Google that if you think computers came of S. V. California..
 
for the record....your spindle pulley does not need to be grooved for the belt.

and if you want to work the maths...its not the diameter...its the circumference you need to figure...as if it were a wheel....how far will it go in one revolution.
 
Last edited:
Must say VFD and single phase / 3 phase / 90 hz / this hz / that hz + poly v belts and pulley got my attention.. I will stop trying to do 10 things at once..

IWAN - wouldnt it more than marginally better to go ahead and use a poly v pulley setup at both ends.. If I am not really going to use the flat 3 step spindle pulleys - and taking the spindle off anyway - why not.. They are not $..

And now that I think of it my diesel serpintine 50 foot v belt has a few of both lol.

I hope you dont say on lathes that equals trouble 😶.. Putting in a poly pulley on spindle to get most out of the switch.. Meaning "unforgiving" .. Its just something about doing the conversion and leaving the flat pulley in 😶..

Good night..I ask lathe 101 questions trmw..
 
theres really not much advantage to using a grooved spindle pulley....plus its a PITA and requires some modification of your orginal part....you may want to get the original set up working again someday....id love to have an original overhead drive.

with the small ammount of wrap you will have at the motor end you will want the grooved pulley.....but the larger step on the spindle cone will provide plenty of wrap.
those poly v belts dont slip easily...but you also dont want to entirely eliminate belt slippage....in the event of a jamb up it can save unnessesary damage.

you of course can do it if you wish....but IME theres not much to be gained with the small ammount of power being transmitted. (fractional HP motor)
 
I well "listen" and keep it simple and running stock spindle.. I keep saying I will post a few pics and I will.. Trmw .

Question on J section rib count - 4 or 6??? Or other?. Any other odd option / or whatever I should know about?

Did you know they have diff hardness 61, 67, 73 shore hardness example... Just thought that was a?interesting detail..

One thing this site could use is updated software / web hosting .. Like click on picture link icon - go grap photo and insert image.. I know there must reasons for not having..

NOTE on my overhead.. Thought I had at least 3 parts - still looking for 2 small ones.. Anyway I HAVE the main FRAME for overhead.. Also pulley belt guard.. Need the motor plateform / pulley mount shaft / setup for starts.. I am sure the main frame is the biggest missing link .. And if not - well makes my life easier trying fab a topdeck..
 
when you reply you will see a box at the top that looks like a tree in a picture frame...click that to link pics.

i would go with at least a 6 rib...thats about 3/4" wide IIRC...i "think" the steps on your spindle cone are 1.25"??....so you could go wider depending.
 








 
Back
Top