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8ntsane
01-18-2009, 03:10 PM
Hello everyone
I want to up the spindle speed of my 1941 Sidney lathe. its a big monster 14 swing x 32 centres with what I beleive to be a 5hp 3phase motor. Pics of the lathe can be seen on this site by shearching for 1941 Sidney Lathe. This old girl tops out at 860 RPM, and want to get the speed up to 1200-1500 RPM.
I would like to hear from anyone that has done the same on a simular machine of this size. What was your method of doing this? I was thinking of making up a new sheave/ pully for the motor its self, as the top has a clutch and don,t want to mess with that end of it. Or,,what say you,,on how you would do this? This Lathe should no doubt handle the increase in RPM, and the chucks should allso easly take a top speed of 1500rpm , so Machine and chucks should be fine as far as I can see.

The lathe will run up to 860 now and Im not trying to go any more than 1500- tops so, if there is any thing im over looking here,, by all means,lets hear it.
If you guys know of a better way to do this, or different way, Im all ears

TIA
Paul

barts
01-18-2009, 03:21 PM
By far the easiest way is to use a VFD to drive that motor at up to 2x its nameplate rpm. This can cause problems in some motors :). Keep in mind that the spindle bearings will need close attention, particularly if they're babbit.

1200 rpm should be a piece of cake... that's 50% overspeed. The other neat part of the VFD is of course the "dial a speed" knob; my 5 Hp YMZ will just crawl along at 5% of rated rpm, handy for killing corners w/ a file w/o stopping and switching gears. I hooked up the original jog button to generate a similar slow speed crawl...

NickH
01-18-2009, 03:21 PM
As you already have 3 phase you can probably pick up 3Ph to 3Ph VFDs quite cheap as they are of little use to the hobby market.
Depending on your motor's capability this could get you part or all of the way prior to modifying transmission components.
Check your bearings, chucks & backplates will take the increased speed & loads before spinning it up!
Regards,
Nick

beckley23
01-18-2009, 04:20 PM
I've got a 16"(18-1/2") CY Monarch, about the same vintage as your Sidney, that I increased the top end to 1100 RPM from 487 by changing the motor pulley. Monarch offered this machine with a top end up to 1000 RPM. I've had the lathe for close to 20 years, and I've only used the top end once. I usually stay under 700 RPM.
I've also got 12"(14-1/2") CK Monarch that I doubled the top end to 1400, and have only used the top end once, and I usually stay under 800 RPM. Monarch offered this lathe with a top end up to 1200.
I also increased the HP for both lathes, from 5 to 7-1/2 on the CY, and from 3 to 5 for the CK.
Exercise caution in your speed selection for the top end. Running at the upper speeds has tendency for oil foaming.
You should also consider what a speed change will do to the other speeds. I'm very tempted to drop the top end on the CK to 1200, as I would more usuable mid range speeds.
Also, consider your chuck sizes.
Harry

lane
01-18-2009, 06:35 PM
Replace motor with one that turns 3450 Speed doubles.

8ntsane
01-18-2009, 09:52 PM
Thanks or the input guys

I think now is a good time for me to do the research on VFD ,I no nothing about them other than a bit I read on a google site tonight. I see now that changing the driven sheave will increase the top end, but will mess with the lower speed as well. I want to have it all, the low end, but I like the top end to hit 1200 to 1500 rpm. The one reply had mentioned the he changed out the motor pully but had uped the HP from 5 hp to 7 hp,,,now this raises a new question, Is RPM dependant on HP? To spin it up to say 1500 rpm,,do I need more HP to get atleast the same amount of torque. And with the factory 5hp motor that the lathe has, with a VFD installed, will there be a noticable loss in torque at the top end?

TIA
PAUL

Teenage_Machinist
01-18-2009, 09:58 PM
If the bearings get hot, slow down NOW\

Pressure lubrication can sometimes help.

One option is to make an adapter as detailed in recent HSM mag.

luthor
01-18-2009, 09:59 PM
What type of bearings were used in these machines? That may be your limiting factor.

beckley23
01-18-2009, 10:37 PM
RPM isn't dependant on HP, but torque is. I want the ability to move a lot metal fast, in other words large DOC, heavy feeds, and high speeds. The only limiting factor is dodging those big, hot chips.
IIRC, the headstock input RPM on my 12" CK is higher than the top speed, which means that the top speed has a bit more torque than the motor is supplying, and that torque keeps increasing as the speeds are lowered.
Personnally, I don't think you are going to have any issues with the 5 HP motor.
Harry

Teenage_Machinist
01-18-2009, 10:49 PM
With higher speeds rigidity may become a big factor due to chatter beign a high speed problem.

rdfeil
01-18-2009, 11:42 PM
Paul,
Three choices as all mentioned above... Change shivs/pulleys easy to do but screws up the lower speeds. Go to a VFD in one of 2 ways, 1) just over speed your existing motor, not my favorite fix. 2) put a 3600 rpm motor on it and use the VFD to slow it down, this is my favorite. Now for cost, the shiv is the cheapest. The VFD is not high cost for a 3 ph x 3 ph drive. My approach to this would be to buy a VFD for the application. I would probably buy at least a 7.5 hp drive, this is why... if you run the existing motor at double speed there will be more Hp available. If the existing motor fails at the increased speed (which is very possible / likely) then just replace it with a 3600 rpm motor probably 7.5 Hp and reprogram the VFD and go. I say a 7.5 hp motor because running the motor slower will reduce the hp available.

So in summary.. I would recommend going to a 7.5 Hp VFD on your existing motor and setting the max frequency as is appropriate. This may last a lifetime for HSM use, but a motor failure is possible. If that happens replace the motor with a 3600 rpm motor and slow down the VFD. The end result is that you get the speeds you want and the money spent is recyclable into future changes.

Robin

clint
01-19-2009, 01:27 AM
I don't think with this lathe you will have any problem with rigidness, and I doubt he will be using the higher speeds for large work, however I'm sure carbide inserts may be one of the reasons, along with work with smaller diameter stock for the lust of higher speeds. I think looking into a VFD would be a great way to do this, and you would also get the benefit of dialing in the speed, once you get used to a VFD it spoils you fast.

If you go the VFD route, and it seems your interested in this type, if it were me I would look at getting a bigger pulley for the motor, I'm not sure of the setup on this lathe for transfer of power from motor to spindle, but instead of over speeding the motor you would be better off going with a bigger motor pulley to give your added speed by not over speeding so much. Just don't go to big, you want to keep plenty of power for the slower speeds, it may also be easy to change the pulley out, and if it's just a seldom needed thing for the fast, or slow speed you could keep a nice power band so to speak through out the entire range by having two pulleys.

My Clausing 4900 is set up with a VFD, and the motor has a step pulley on it, I rarely change the speed by the pulley, it saves me loads of time, and aggravation having a VFD.

SVS
01-19-2009, 07:25 AM
Unless you have a money tree, I'd spend $50 for a 50% bigger moter pulley and forget the $500 vfd and $500 motor. Don't mean to be a buzz-kill, but you can swap pulleys in an hour. Figure two days to replace motor and install and program vfd.

clint
01-19-2009, 11:41 AM
SVS

He may not need a motor, just a VFD, and if he is frugal about it, he may come out around $150 or so. Just the benefit of VFD speed adjustment alone in my opinion is enough to pay for that, and while he is wanting to add speed to his lathe I think this will just be icing on the cake. However I do agree with the need for a larger pulley, it would save a lot of other problems, and may keep him from damaging the motor as well. Then again over speeding the motor may not hurt anything, I don't have enough experience over speeding motors to give any advice here, but from reading most motors of this type are built the same as far as bearing etc for 1750 RPM or 3600 RPM, not sure if it will damage the electrical components of the motor.

A pulley change to increase the speed before you dump any more money into it would however give you a hands on example that will let you see if this is what you want to do, how the lathe, cutting tools, etc react to the increase of speed etc.

jkilroy
01-19-2009, 01:44 PM
"its a big monster 14 swing x 32 centres..."

Thats funny, must be the smallest Sidney ever made, and its a monster!! :D

noah katz
01-19-2009, 07:52 PM
"1) just over speed your existing motor, not my favorite fix. 2) put a 3600 rpm motor on it and use the VFD to slow it down, this is my favorite."

One thing I like about overspeeding is that the cooling fan is running faster than normal, not slower.

Not sure what kinds of bad things might be happening with that option, though, like higher likelihood of insulation breakdown.

beckley23
01-19-2009, 08:04 PM
The lowest speed on my 16" CY is 27 RPM and the CK's is 34. I would look very closely at the mid range speeds and work some nunbers on SFM for various diameters. I think you would want usuable speeds for both HSS and carbide, that's why I'm considering lowering the top end on the CK; the 3 speeds under the top end aren't optimum to my tastes.
I've got a 10" 3 jaw on the CY, and work smaller than 3/4" gets to be dicey, especially when working close to the chuck, and I'll usually put it on a smaller lathe just for easier handling.
Unless you're going to use the VFD as a phase converter, I would change the motor pulley; as has been noted it is far more economical.
I'm linking to a posting by the late Jim Kizale that is very enlightening, he really gets into the power transmission system of a lathe, more to the point the "super lathes". It's a good read;
http://www.practicalmachinist.com/vb/showthread.php?t=115875&highlight=super+lathe
Harry

Carld
01-19-2009, 08:54 PM
The Sidney lathes are one of the strongest heavy duty lathes you can buy. If I were you I would not increase the speed. If you do, why don't you just change the pulleys on the motor and headstock. That would be the cheapest way and you can always switch back.

You could even use a double sheeve on the headstock and motor.

8ntsane
01-19-2009, 11:49 PM
Thanks for the input given
I have read through all the posts very carefully and it seems there is a few ways to go about this speed increase deal. I do like the Idea of useing the VFD and having a vari-speed type of control, as my Induma Mill has the Vari-speed head that I just feel in love with, after a short time after owning the machine. So its a good thing to have on a lathe as well. I intend on mounting uo a collet chuck on this lathe and would really like to have the extra spindle rpm, and if I can gain control of the speeds with the VFD then thats great.

As recomended, I think it would be a good move to change out the motor pully to see if that is what I want,and how the machine, cutting tools react to this change. This lathe has 4-groove pully on the motor that run up to the spindle that has this clutch set up attached up stairs at the spindle. So at best, I would be maching up a 4-groove motor pully to increase spindle speed. As mentioned, the top end has this clutch arangment on it, so Im not into messing around with that end of it. The motor pully seems like a easy project for me, so Im thinking I will start with that. I do understand that doing this will mess up my low speed rpm,and wont be able to correct it unless I use a VFD.

dbc58
01-20-2009, 12:23 AM
Paul,
I just got got a similar Sidney from 1945. It is identical to yours except I have the 8' bed (about 60" between centers) and a top speed of 594. You apparently have what was considered the "high speed" option. I haven't done it yet, but my plan was to change the motor sheave for a top speed of about 1200. If you wouldn't mind could you measure your motor sheave? I was wondering if Sidney had simply used a bigger sheave or actually changed the gearing in the headstock. Thanks,
Dave

8ntsane
01-20-2009, 12:39 AM
Thanks for the input given
I have read through all the posts very carefully and it seems there is a few ways to go about this speed increase deal. I do like the Idea of useing the VFD and having a vari-speed type of control, as my Induma Mill has the Vari-speed head that I just feel in love with, after a short time after owning the machine. So its a good thing to have on a lathe as well. I intend on mounting uo a collet chuck on this lathe and would really like to have the extra spindle rpm, and if I can gain control of the speeds with the VFD then thats great.

As recomended, I think it would be a good move to change out the motor pully to see if that is what I want,and how the machine, cutting tools react to this change. This lathe has 4-groove pully on the motor that run up to the spindle that has this clutch set up attached up stairs at the spindle. So at best, I would be maching up a 4-groove motor pully to increase spindle speed. As mentioned, the top end has this clutch arangment on it, so Im not into messing around with that end of it. The motor pully seems like a easy project for me, so Im thinking I will start with that. I do understand that doing this will mess up my low speed rpm,and wont be able to correct it unless I use a VFD. Im going to make up the motor pully first , then if Im happy with it, Im thinking the VFD would be the next thing to add on.

Now, the question of , will the original 5 hp motor live with the VFD? Well, thats something that time would tell the story on that issue. As I understand it, over speeding the motor on a VFD risks damage to the motor, and running the motor slower can make it run hotter, so I guess its a balance of the worst of the two evils. It seems like there is much for me to learn about these VFD conversions,but Im doing alot of reading now its been mentioned to me. Its all a bit confusing , but Im getting the newbee to VFD input both here and on google. I never had so much as looked at VFD units till yesterday,so as you all know, I have some more home work to do here.

Im thinking end result of the pully, and vfd would give me more than I need, with varible speed would be a big plus in my book. Even if the original motor dies over this, I think I could dig up a good replacement with out breaking the wallet. Im figuring that its going to be 3-stage deal, pully 1st,,VFD second, and if need be, Ill swap out the 5hp, for a 7 1/2hp @ 3650 rpm and that should do it. I dont mind spending a few bucks on old Sidney, cause Im going to have this lathe till they throw me in the fire.

Any and all input on this topic is good reading lessons for me,,thanks guys.
TIA
Paul

8ntsane
01-20-2009, 12:59 AM
Paul,
I just got got a similar Sidney from 1945. It is identical to yours except I have the 8' bed (about 60" between centers) and a top speed of 594. You apparently have what was considered the "high speed" option. I haven't done it yet, but my plan was to change the motor sheave for a top speed of about 1200. If you wouldn't mind could you measure your motor sheave? I was wondering if Sidney had simply used a bigger sheave or actually changed the gearing in the headstock. Thanks,
Dave

Hey Dave
I can check the motor sheave for you tomorrow, just gotta pull that plate cover off to get at it. I think all they did was change out the pully, but thats just my guess. The belt number on the clutch cover doesnt match the machine, the number given is to small , and it takes a longer belt on my machine, I know Sidney did alot of low speed lathes, I dont think they would go through all the trouble to change the gearing in the headstock, would they ? lol But keep in mind that my lathe is currently running a top speed of 860 rpm. I have verified it with a digital tach. Still want me to measure it?

Let me know
Thanks Paul

8ntsane
01-20-2009, 01:34 PM
[QUOTE=dbc58]Paul,
I just got got a similar Sidney from 1945. It is identical to yours except I have the 8' bed (about 60" between centers) and a top speed of 594. You apparently have what was considered the "high speed" option. I haven't done it yet, but my plan was to change the motor sheave for a top speed of about 1200. If you wouldn't mind could you measure your motor sheave? I was wondering if Sidney had simply used a bigger sheave or actually changed the gearing in the headstock. Thanks,
Dave[/QUOTE


Dave , the pulley od is 8 inches and the belts are B-90
On my cover its says the belt #B-85 but I had tryed to fit them up, just not long enough. The B-90 is what was on mine when I got it. They are 5/8 wide v belts on this one. By the way, the this pully the belt sits allmost flush with the pully, sticks up maybe 1/16 when in the groove

Paul

tiptop
01-20-2009, 09:22 PM
Paul,
I think you are on the right track with your motor pulley change out and the VFD addition. I have a Monarch 14C with a 5hp, 3ph motor. It is a 1942, with 16" swing and 54" between centers. That is what I was intending on doing, although I do not think I will go as fast as you are planning. My thoughts were about 1000 rpm and a Sensorless Vector VFD. I do not believe that even with the VFD running at half hertz I will find any deficiencies in motor torque. I will be hard pressed to ever run this machine to the capacity it was originally set up for. Good luck with your project and keep us posted as I am very interested in seeing which way you end up going and how it works.

Jay

dbc58
01-20-2009, 10:37 PM
I just checked the motor and it is 1160 RPM, 5 HP, 220/440 3 phase. It has a 5" pulley and B85 belts. I opened the headstock today and it doesn't look like they have enough room to change the speed that much through gearing. The book I have shows the high speed head with a 25-950 rpm and the low speed to be 14-534. It also mentions a drive pulley of 575 for low and 1024 for high. So it looks like pulleys or a motor rpm change.
Dave

Carld
01-20-2009, 11:04 PM
8ntsane, if the belt number on the door is a factory mark I would suspect that the motor pulley has been changed to a larger diameter. Is there an adjuster for the belts?

8ntsane
01-21-2009, 12:09 AM
Dave

Funny you meantion the motor speed, and I have found on the clutch cover nose, its marked for clock wise rotation, and RPM of 575, and yea with the cover off and watching the motor turning that big 8in dia pully, I would have to say mines probably turning that RPM. So I guess they had some different motor speeds back in the day, Im going to have a deeper look at this now.
Im thinking that the 8-inch pully is plenty big now, and to make up a larger dia 4 groove pully is going to be alot of wt spinning on that motor.

I have no idea if those VFDs work with a low speed motor such as mine. I think there will be a few complications along the way to changing the RPM .
Mostly im hearing about 1750,or 3650 motors be used, thats a fair jump if mines only turning 575 rpm. Im going to check with a tach to make sure this is indeed the rpm my motor turns. Im getting a little confused now, on just how they get there speeds. Pullys,motor rpm,,both,and then?

You have some numbers that are close to mine for the hi-speed model, but mine is 24 to 860 rpm but mines a 41 and yours is 45.

Now, if in fact my motor is a 575 rpm deal, even if I wanted or need to swap over to say a 1750 rpm deal, then I have to wonder if it would be bad to slow it down so much with the VFD? Sounds like I would need to reduce the pully dia, along with that motor swap. THis mght take some deeper thinking here.

Carld
The belt number is stamped into the cover B-85 and I thought ok some how this machine had the wrong belts installed, the belts that where on it are B-90,,I tryed them but they where too short to fit. The motor sits on a big Plate that is hinged on one side, and has this long stud that has a spring under the plate, and one on top of the plate. The ajustment wouldnt allow me to use the B-85 belts, so back to the B-90 I went.

Im thinking the B-85 belt works with a 5-inch pulley like Dave has.
Now its getting interesting,lol

Tip top
What RPM is that 1942 motor turning?

Thanks guys

dbc58
01-21-2009, 12:32 AM
The book isn't clear, but I believe those drive pulley speeds are for the input shaft of the gear head. Mine appears original. I don't have power to it yet so I can't measure the speeds yet. Another issue I have is the voltage. I have 208 3ph and the motor is 220 3ph. I don't believe it will be an problem other than losing a little of the HP and maybe running warmer. Do VFDs provide buck/boost?
Dave

tiptop
01-21-2009, 01:21 AM
Paul,
My motor turns at 1750 rpm, The drive pulley(on the motor) is 3.75" Dia., The driven pulley (on the clutch pack) is 11" Dia., The lathes current high speed is 487 rpm, and the lowest speed is 12 rpm. I am planning on a 5" to 6" drive pulley with a VFD to slow it back down.

Jay

barts
01-21-2009, 03:49 AM
I have no idea if those VFDs work with a low speed motor such as mine. I think there will be a few complications along the way to changing the RPM .


The only possible thing to do is correct the 60hz = ? rpm factor if your VFD has a speed display in rpm; otherwise it will Just Work, TM. VFDs just care about volts & amps....

8ntsane
01-22-2009, 12:02 AM
I just checked the motor and it is 1160 RPM, 5 HP, 220/440 3 phase. It has a 5" pulley and B85 belts. I opened the headstock today and it doesn't look like they have enough room to change the speed that much through gearing. The book I have shows the high speed head with a 25-950 rpm and the low speed to be 14-534. It also mentions a drive pulley of 575 for low and 1024 for high. So it looks like pulleys or a motor rpm change.
Dave

Hey Dave
I just got back in from the cold shop, and I did the test with a tach, and my motor runs at 1196 rpm and I think I should let you know that I was off a bit when I measured the motor pulley, its not 8 inch,,but is a 7 3/4 inch instead.
I removed the whole cover to get a more accurate measurement. I didnt pull the clutch cover off , I am going to do that tomorrow, as I would like to know what dia pulley is on up stairs. Have you measured that one yet? If so, let me know what your has. While I was testing out the motor speed, I also checked the spindle speeds , and yes , its a low of 24, and the hi is 860 so I dont have a changed out motor pulley, as all the speeds are correct to the machine. I guess maybe they got the wrong cover on mine, that lists it as a b-85 belt.

So, as it goes, my motor runs 1200 rpm , no load, and my spindle speeds are correct as marked. I guess the next thing for me is to check the dia of the upper sheave, then it might be easyer to calculate the new dia on the motor to speed this thing up some. Im starting to think maybe I should just add the VFD and not really worry about the motor sheave. If the VFD will let the motor speed up to say 1500 rpm, then thats only 300rpm more than she had to start with. But if I increase the motor speed by 300, what will that get at the spindle? More checking and thinking I guess.

Im hoping to get a VFD mounted up on Sidney, as I like the idea of having vari-speed. Just have a few more things to check out. Have you figured out what size sheave your going to use on your machine Dave?

Im thinking that if a VFD could be added to mine with out changing the motor sheave, that would be nice, and would save me alot of work, buiding a ne motor sheave, but let see what unfolds from here.

thanks guys

dbc58
01-22-2009, 01:05 AM
Just a rough estimate, but your highest speed is about 2/3 of your motor speed so a gain of 300 rpm would increase the spindle by only about 200 rpm. WWGrainger has 4 belt sheaves in larger sizes for "B" series belts.

beckley23
01-22-2009, 07:20 PM
If you change the motor to an 1800 RPM motor, all your speeds will increase by 1-1/2 times, so your new high is 1290 and new low is 36.
Be careful of the motor frame size, you can run into problems with shaft diameter and center height.
I just went through that recently.
Harry

8ntsane
01-25-2009, 07:49 PM
If you change the motor to an 1800 RPM motor, all your speeds will increase by 1-1/2 times, so your new high is 1290 and new low is 36.
Be careful of the motor frame size, you can run into problems with shaft diameter and center height.
I just went through that recently.
Harry

Harry and others that have experiance with this.

I don,t know if you have followed this post , but maybe you could help me figure out what speeds I would end up with useing the 4-groove sheaves that grainger sells. They range in price from 120 bucks on up, so not really worth my effort to machine up a new one. As I have allready stated, my motor runs at 1200 rpm now, and Id like to change out the lower pully to get the rpm up, but I dont really know how to figure out what diam sheave to buy, and what rpm would be expected to get with a given dia sheave.

The sheave currently being used is 7 3/4 OD, and have been thinking of using the Dayton 4JE36 with a OD of 9.3/4 . There are others listed, but using this one for example only. The top speed Im trying to hit would be 1200 1350 at the spindle.

Once all this pulley change is done with, I would intend on slowing this back down with a VFD

Paul

beckley23
01-25-2009, 10:59 PM
Paul,
Motor RPM X D of pulley mounted on it divided the the D of the driven pulley will get the driven pulley's RPM.
You already know the existing diameters and the RPM of the motor and you also know the top end on the spindle. You have an established relationship between the driven pulley and the spindle that is a constant, and can't be changed.
For your lathe as it is now this equation would look like this; 7.75 X 1200 divided by 8(input pulley D, IIRC)= 1162.5 RPM on the input RPM, and through the gearing in the headstock you have a top end of 860 and a bottom of 24. I just multiplied the top end by 1.5 to get the new top end with an 1800 RPM motor.
Now if you want use the existing 1200 RPM motor and effectively increase your top end to 1290 RPM(let's make it easy) you will need an input RPM of 1743.75. Your new equation is (1200)(X) divided by 8= 1743.75. Solving for X = 11.625" D for the motor pulley.
Now, I have a question for you; Will the belt guards for the lathe allow you to do this? My guess is no. When I upped the top ends on the CK and CY, and my #5 J&L turret lathe, the clearances got real tight with these guards, and the new drive pulleys were still smaller than the input pulley. Your new drive pulley is going to be considerably larger than the input pulley.
I've made a multi-grooved pulley, it wasn't easy, and it was a lot smaller than 11-5/8".
I think you can see the reasoning behind my suggestion of a new motor.
I know of the enthusasism with VFD's, I've got one on my 10 EE, but I feel that on a geared head lathe they are a waste of money, unless you are using the VFD as a phase converter. I ran some SFM calculations on a 14" D piece; at 36 RPM it's approx 113' SFM, @ 24 it's approx 88' SFM.
Harry

8ntsane
01-29-2009, 12:05 PM
Paul,
Motor RPM X D of pulley mounted on it divided the the D of the driven pulley will get the driven pulley's RPM.
You already know the existing diameters and the RPM of the motor and you also know the top end on the spindle. You have an established relationship between the driven pulley and the spindle that is a constant, and can't be changed.
For your lathe as it is now this equation would look like this; 7.75 X 1200 divided by 8(input pulley D, IIRC)= 1162.5 RPM on the input RPM, and through the gearing in the headstock you have a top end of 860 and a bottom of 24. I just multiplied the top end by 1.5 to get the new top end with an 1800 RPM motor.
Now if you want use the existing 1200 RPM motor and effectively increase your top end to 1290 RPM(let's make it easy) you will need an input RPM of 1743.75. Your new equation is (1200)(X) divided by 8= 1743.75. Solving for X = 11.625" D for the motor pulley.
Now, I have a question for you; Will the belt guards for the lathe allow you to do this? My guess is no. When I upped the top ends on the CK and CY, and my #5 J&L turret lathe, the clearances got real tight with these guards, and the new drive pulleys were still smaller than the input pulley. Your new drive pulley is going to be considerably larger than the input pulley.
I've made a multi-grooved pulley, it wasn't easy, and it was a lot smaller than 11-5/8".
I think you can see the reasoning behind my suggestion of a new motor.
I know of the enthusasism with VFD's, I've got one on my 10 EE, but I feel that on a geared head lathe they are a waste of money, unless you are using the VFD as a phase converter. I ran some SFM calculations on a 14" D piece; at 36 RPM it's approx 113' SFM, @ 24 it's approx 88' SFM.
Harry

Thanks Harry for taking your time to sort that out for me.
Your right, I have no room for a pulley of that size on my machine. I might be able to fit a few inches more dia, but not 11 inch and bigger.
So, it looks like I,m going to need a motor change to start with. Im kind of in the dark about what I should be going after, the motor I have is 575 volt 3-phase, and Im not sure if I should be looking for the same voltage, or go to the 240 volt replacement in single or 3-phase? I have heard of some guys talking about using the VFD as a phase converter, and that is somthing I dont understand. Thats way I am wondering what voltage motor I should be hunting down. I have noticed that the older motors appear to be much larger than the motors they have thes days, so I can see what your saying about the centre hieght being different. Ah yes, so much to learn. Im still going to need a VFD to slow this down after the motor change. I also have been wondering if I should up the HP to 7.5 like you had done, or stay with the 5-hp?

I know, I have lots of questions, just trying to understand all of this stuff. Thanks again for taking the time to reply to all this.

beckley23
01-29-2009, 07:30 PM
I'm getting out of my expertise about electricals, but here goes, and this may be a lttle disjointed on my part.
If anybody else wants to jump in here, feel free, I just basically write the checks for electricals.
You will need to know the voltage that you can supply, and the amperage the circuit can handle.
If you have 230V available, either single or 3 phase, this should be relatively easy. Most VFD's that I'm aware of are 230 V, I'm assuming you're in the USA. There are VFD's available that will take a 230V single phase input and convert it to 3 phase, up to 5 HP.
Regarding the 575V motor, I don't think you are going to find a 230V VFD that will output 575V, so I think your motor is history.
I recently did a motor switch that I covered in this topic onthe Monarch forum of PM
http://www.practicalmachinist.com/vb/showthread.php?t=163406
The only reason for the increase in motor HP, is because the replacement had the same shaft size as the original. I examined the costs of going with a tapered bore pulley and bushing, the motor costs, etc, and found the cost would be about the same, but the installation difficulty was increased with a smaller frame size.
Harry

8ntsane
01-30-2009, 08:20 PM
I'm getting out of my expertise about electricals, but here goes, and this may be a lttle disjointed on my part.
If anybody else wants to jump in here, feel free, I just basically write the checks for electricals.
You will need to know the voltage that you can supply, and the amperage the circuit can handle.
If you have 230V available, either single or 3 phase, this should be relatively easy. Most VFD's that I'm aware of are 230 V, I'm assuming you're in the USA. There are VFD's available that will take a 230V single phase input and convert it to 3 phase, up to 5 HP.
Regarding the 575V motor, I don't think you are going to find a 230V VFD that will output 575V, so I think your motor is history.
I recently did a motor switch that I covered in this topic onthe Monarch forum of PM
http://www.practicalmachinist.com/vb/showthread.php?t=163406
The only reason for the increase in motor HP, is because the replacement had the same shaft size as the original. I examined the costs of going with a tapered bore pulley and bushing, the motor costs, etc, and found the cost would be about the same, but the installation difficulty was increased with a smaller frame size.
Harry
Thanks Harry
Ill will check out the link on PM. Im sure I will find lots of reading material on this subject ove there. Again thanks for your response. It does help when you talk to someone thats been there before. ;)

Paul

yf
02-02-2009, 03:11 AM
One more option would be a "Driveall" type gearbox between the motor and gearbox input pulley.

They are three or four speed gear boxes with ratios of 1-1, 1-2, 1-3 and 1-4.
The only ones I've seen were 3 and 4 speed. They have a lever that is pulled or pushed and turned to engage the gears. They must be shifted at rest.


For your need, 1-2 and 1-3 would work with a 3600 rpm motor.
1-3 would give you the same speeds as now, 1-2 would be 1.5 times faster and 1-1 would be 3 times as fast.

Or, you can use your existing motor and run the Driveall in reverse to double, triple, quadruple or keep the same RPM.

You can also change the motor pulley or the Driveall gearbox input pulley, to alter the ratio as desired.


There is always another way.
Driveall's show up on ebay occasionally.