have 4:1 from 3000rpm dropping down to 750 rpm what gears to get 600rpm

[Michael GilliganParticipant @michaelgilligan61133]

Gentlemen,

I may be wrong [it has been known]; but I think it's reasonable to assume that Martin is working with the Kity motor that was the subject of this earlier thread, and the happy ending of  this one … If so, then suggestions of substituting a 3 phase motor and inverter might be considered inappropriate.

MichaelG.

Edited By Michael Gilligan on 03/07/2016 13:05:11

[Keith LongParticipant @keithlong89920]

One point no-one's picked up on so far – if you're looking to get the lathe top speed at 600 rpm then you should be doing so with the SMALLEST diameter pulley of the three (?) on the lathe spindle not the largest – that's for the slow speed.

[Martin NewboldParticipant @martinnewbold]

Gave up and bought a laser RPM gauge as someone above said cant rely on online tables so will see if they are acurate when it arrives. thanks for all the help

 

Cheers

M

Edited By Martin Newbold on 03/07/2016 13:35:30

[SillyOldDufferModerator @sillyoldduffer]

Posted by Martin Newbold on 01/07/2016 21:23:07:

Hello

Ah I see from the 750 rpm I need a driven 5" pulley driving a 4" on the final from my 1" on motor driving 4" So would need a 5" and a 4", on single intermediate shaft.

Cheers

Martin

Looking back I think you had it right early on in the thread Martin.

1 on the motor and 5 on the counter-shaft would reduce 3000 to 600 rpm. Then to get from the counter-shaft to the 4 on the lathe, you need a 1:1 ratio, which would be provided by another 4.

So 3000 x 1/5 = 600

and

600 x 4/4 = 600

I think anything between 350 and 650 rpm would do for most general purpose work. Ideally you would have three of four speeds available between 100 and 1000 rpm. The extra speeds make it easier to do a wider range of jobs.

Cheers,

Dave

[Martin NewboldParticipant @martinnewbold]

Hi Dave

Yes have been working on this two measuring all the pulleys This is the information I have gathered ( the data is without the benefit o the rpm gauge i have ordered )

Lathe

Largest : outside 114mm(4.5 ” ) inside 100 mm(4”  ).

Middle: outside 90mm(3.5“ ) inside 80mm(3“ ).

Small end:  outside 64.5mm(2.5“ ) inside 55mm(2“ ).

Motor

Small End: inside 25mm(1” )

Middle: inside 50mm(2“ ).

Largest:inside 75.5mm(3“ ).

Floating Pulley

52mm 1”.

 

Therefore using Pulley Calculator

1:4.5 = 658rpm, starting with 3000rpm.

1:4 = 750rpm, starting with 3000rpm.

1:3.5 = 833rpm, starting with 3000rpm.

1:3 = 1000rpm, starting with 300rpm.

1:2.5 = 1179rpm, starting with 3000rpm.

1:2 = 1500rpm, starting with 3000rpm.

 

1:3 = 500rpm , starting with 1500rpm.

2:3 = 1000rpm, starting with 1500rpm

2:4 =750rpm, starting with 1500rpm.

2:5 =600rpm, starting with 1500rpm.

 

If this is correct would just need a 5" pulley next to my 2" driven from the motor, On a question with your sized pulleys Dave would the bigger pulleys give better torque than the 2" to 1"

The trouble wth a 1 to 5 giving 600rpm i would nee a 3.5,4.5 or 2.5 pulley to match the lathe not so easy to find i think. This is why I have been looiking for other options

Cheers Martin

Edited cause of Damn smileys

 

Edited By Martin Newbold on 03/07/2016 19:16:35

[SillyOldDufferModerator @sillyoldduffer]

Hi Martin,

Good timing – you got rid of the smileys whilst I was away logging in.

Re: 'On a question with your sized pulleys Dave would the bigger pulleys give better torque than the 2" to 1"

Well, in theory no. The torque conversion simply follows the same ratio as the speed conversion, only the other way round. (So a 2:1 ratio would halve the speed and double the torque whereas a 1:2 ratio would double the speed and halve the torque.)

It's not that easy though. Theory is fine and dandy but in the real world belts slip. And they are much more likely to slip on a small pulley than a big one. Slip costs both torque and speed, wears the belt and might overheat. Therefore for a given load and speed it's unwise to go below a certain minimum pulley size, which is why some of the other posts questioned your 1" pulley.

I'd give it a try and see what happens. If you get slip that you can't control with a jockey wheel or other way of adjusting belt tension, try bigger pulleys.

Trouble is, if you double the size of the driver, you have to double the size of the next one too.

It's a bit of a balancing act.

Cheers,

Dave

[Martin NewboldParticipant @martinnewbold]

tah ,Dave am going to wait till i get a tachometer reading to see if my figures are correct , with the 4.5 opposed to 4 of the lathes pulley, as this will have a bearing on my extra pulleys and if its compatible with 4". If it is then this will be eaiser. My motor is on a wedge pulling the tension by its own weght so no problems there . The second stack of gears will need a tensioner havent thought about how to work this yet .

Cheers

Martin

[Martin NewboldParticipant @martinnewbold]

ok according to laser guage have 150rpm on back gears and 420rpm on main drive.

Cheers

Martin

[Martin NewboldParticipant @martinnewbold]

Well don't worry about buying one of these its not accurate cant understand why anyone would make one that doesnt give continuous readings

**LINK**

[Martin NewboldParticipant @martinnewbold]

Aha found out why it didnt work had the tape on the outside didnt work has to be on on the diameter poking over edge got top speed 1013 r.p,m and 113r.p.m low back gear . This is why its been heating up the bearings needs to reduce to 600 rpm. so 5" and 4" pulleys here we come me thinks

[Martin NewboldParticipant @martinnewbold]

Yep you were right the Pulley calculator isnt accurate on the online pages my motor is running at 2939 r.p.m and cannot get any combination of the pulleys on the site to get speed to 1013 r.p.m so think you are correct it does not work

 

Cheers Martin

Edited By Martin Newbold on 11/07/2016 21:57:48

[bodgeParticipant @bodge]

Posted by Martin Newbold on 11/07/2016 20:45:09:

. This is why its been heating up the bearings needs to reduce to 600 rpm. so 5" and 4" pulleys here we come me thinks

Well no surprise`s there, the lathe is now seriously over powered, the belt does not fit the mandrel pulley properly so is driving through tension more than grip, a 4 pole 1428 rpm 1/2 hp would have been more than ample for this lathe and a lot less bother to reduce the speed………….b

[not done it yetParticipant @notdoneityet]

Ahh, I see, bodge. Thread started on the wrong track. The real issue was substitution of an inappropriate drive? Too powerful, too fast (for a plain bearing spindle?) and likely excessive radial loads, beyond the bearing limits and possibly in the wrong direction? Nowt better than proper design, rather than trying to beat the mechanical constraints of the installation.

[bodgeParticipant @bodge]

Posted by not done it yet on 12/07/2016 04:35:29:

Ahh, I see, bodge. Thread started on the wrong track. The real issue was substitution of an inappropriate drive? Too powerful, too fast (for a plain bearing spindle?) and likely excessive radial loads, beyond the bearing limits and possibly in the wrong direction? Nowt better than proper design, rather than trying to beat the mechanical constraints of the installation.

Yes thats about the long and short of it, ( been there, seen it and done it, on same model lathe. ) plus there are three threads running all to do with same model lathe . Martin Cleeve did some excellent articles on lathes and drives in the ME years ago, one in particular comes mind to do with an EW lathe, gave much information on the ratio of speed increments as one moves the belt across pairs on cone pulleys,

Have spent much time on drives on my own lathes, and run a double counter shaft on the main use 4 inch lathe , which came about because i wanted the motor under the lathe ( bit different from your usual myford ) so this gives two highs and lows using two steps ( counter shafts and motor pulleys are doubles ) plus the usual four on the mandrel cone = 16 speeds plus 16 more with the back gear engaged, low low with back gear in is about 12 rpm, high high direct is around 1000-ish, motor pulleys a poly v belt and motor pulleys are easy and quick to make so could go faster if need be………………….b …………….powered by 1/2 HP 1428 motor !…………b

yes plain split p/bron bearing ………….(. so is my 4 inch lathe ) ……………….sorry for all the edits had refer to notes to check speeds………………b

Edited By bodge on 12/07/2016 06:35:07

Edited By bodge on 12/07/2016 06:40:59

Edited By bodge on 12/07/2016 06:52:57

Edited By bodge on 12/07/2016 07:10:40

[Martin NewboldParticipant @martinnewbold]

Cant believe the gearing charts online are such rubbish . Its going to make it hard to work out which pulleys to use to get close to 600rpm any ideas. Will be putting in a second set of pulleys but need to work out what sizes to use as the website data i was using is completely wrong

[Martin NewboldParticipant @martinnewbold]

Well am getting 113rpm on back gears and 1013 rpm from a 1" to 4.5" drive on a 2939rpm as powered from motor . Am clueless as to figure out lay shaft if these block pulley charts are all rubsh which it seems they are .

How did you work out your pulley sizes bodge ?

Cheers

M

Edited By Martin Newbold on 16/07/2016 12:32:15

[bodgeParticipant @bodge]

Hi Martin,

Due to the way you have your lathe set up, you can only really use the largest pulley on the lathe mandrel, trying to use the two smaller sizes will at the least cause a loss of grip due to less contact area, (also may cause clearance problems, the bigger the pulley the better the grip.) So the final drive ie last driven pulley in the drive train will be one to one ( 4 inch pulley driving the 4 inch lathe mandrel pulley ) I would also suggest you use a polyurethane type belting on this section of the drive train as it will grip better due to being a better fit and give a smoother drive. I would also suggest you obtain 1428 / 1500 rpm motor, 1/2 hp will be enough.

To work out the speeds/pulley sizes, using my one pic as example= Motor pulley 11/4 inch dia`at 1500 rpm – Driving – 61/4 inch = div 6.250 x 1.25 = 5 — 1500 rpm divide by 5 = 300 rpm, So driving speed is now 300 rpm.

The cone on the driven shaft is the is the same as the cone on the mandrel ie –4–3–2- now

driving –2–3–4– so 4 driving 2 (is = to 1 to 2) will be 600 –3 driving 3 ( is = to 1 to 1) will be 300 — 2 driving 4 (is = to 2 to 1 will 150 rpm

The above is example only and no allowances made has been made for motor slip, the above gives fastest possible —-(but its near enough)

The problem as i see is you will need to rig a pair of cones and shafts under the lathe, might not be to pleasant to use, ……………………b

To use 3000 rpm motor , you would need 1 inch motor pulley driving 91/2 pulley………

Edited By bodge on 16/07/2016 22:34:26

[Martin NewboldParticipant @martinnewbold]

HI bodge

Hmm am in need of som emore info as am not driving up to a 91/2 pulley as its huge

With my 4.5 on my lathe and 1 " on my motot at 3,000 and looking at two pulleys under side by side as a lay shaft. its hard to find a 4.5" puley so not sure i can use one to 9 1/2 am in need of a differant solution of pulleys.

cheers

Martin

[Howard LewisParticipant @howardlewis46836]

Coming in late on this, it seems that your solution has already been given.

Make up a Countershaft. Drive from the 1" motor to a 5" on the Countershaft, and then from a 4" to the 4" on the lathe mandrel. Then you should have your required 600 rpm. The Countershaft/Mandrel belt tension is set first, and then you set the tension on the Motor/Countershaft belt.

Being me, I would try to arrange things so that there were at least three sizes of pulley on the motor shaft and on the Countershaft, with little or no change in belt tension as you change speeds Although cannot see ANY need to run the mandrel faster than the motor on an elderly plain bearing machine)

Possibly the best way is to have a 1" pulley on the motor with three sheaves, driving to three pulleys of increasing diameter on the Countershaft. The motor will need to be moveable to set the tension, but If you want to increase the wrap around on the pulleys, use a longer belt and run a jockey pulley on the outside of the primary belt (motor to Countershaft). The jockey pulley can adjust the tension by various methods, 1) a lever with a weight on the end of an arm, to given more or less constant tension, 2) a screwed rod to adjust the position of the jockey wheel, or 3) a spring to hold the jockey in contact with the back of the belt..

Also, with a large enough range of movement on the Jockey Wheel, that can be used to set the tension, as well as increasing the angle of wrap.

With regard to tension, Vee belts tend to increase tension when at speed, because of the centrifugal forces acting on the belt. And, if you over tension the belt, you increase the load, needlessly, on the bearings. You only need enough to prevent slippage, just about 1/2" of movement, with a little force applied midway between the pulleys, assuming a centre distance of about 10".

The Countershaft could run on a pair of plummer block bearings set on a pivoting  frame.  The Countershaft possibly could be sited behind the lathe, driven by the motor below.

H T H

Howard

Edited By Howard Lewis on 23/07/2016 13:35:42

[Martin NewboldParticipant @martinnewbold]

Yes Howard, yes i know its been said but the final drive pulley on lathe is 4.5 not 4

[Ian S CParticipant @iansc]

The only size lathe I would(do) run from a 1" pulley on the motor is something the size of a "Super Adept", with a 100W or so of power and driven through a 5 mm heat fused belt. Unless you are using a Poly V belt, 1" does not have enough surface area to prevent belt slip, and for an ordinary V belt it is too tight a bend.

Ian S C

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Ian S C on 24/07/2016 12:03:59:

Unless you are using a Poly V belt, 1" does not have enough surface area to prevent belt slip, and for an ordinary V belt it is too tight a bend.

.

Martin,

Please heed this ^^^

MichaelG.

[Michael GilliganParticipant @michaelgilligan61133]

Martin,

Please correct me if I have chosen the wrong pictures but; for the benefit of any late-comers to this thread, I think it worth linking a couple of your photos.

1. Early configuration: **LINK** http://www.model-engineer.co.uk/wp-content/uploads/sites/4/images/member_albums/152239/660217.jpg
2. Replacement motor, currently in use: **LINK** http://www.model-engineer.co.uk/wp-content/uploads/sites/4/images/member_albums/152239/681115.jpg

May I suggest that you set up a countershaft with a primary reduction on poly-vee, and a secondary reduction on the existing vee-belt arrangement … I'm sure this would make things much easier.

MichaelG.

[Michael GilliganParticipant @michaelgilligan61133]

Martin,

Yes, it's me again … I just had another look at the first picture that I linked in the previous post.

You appear to have the cone pulley on the motor the wrong way round … Usual practice is to have the motor pulley the pointing the opposite way to the lathe pulley.

MichaelG.

[bodgeParticipant @bodge]

Posted by Michael Gilligan on 24/07/2016 12:11:03:

Posted by Ian S C on 24/07/2016 12:03:59:

Unless you are using a Poly V belt, 1" does not have enough surface area to prevent belt slip, and for an ordinary V belt it is too tight a bend.

.

Martin,

Please heed this ^^^

MichaelG.

Yes that is why i refer to my one & only pic, poly v primary drive, round belt finale drive, 200 watt 1428 rpm motor. ( As can see in the pic, still need to cut second step on large pulley & make two step motor pulley ) always think it best to sort out lowest direct speed first & aim for around 100 rpm, as this has direct effect on what speeds you get with the back gear engaged.

Martin

The counter shaft cone ( the cone hidden behind the big pulley ) is exactly the same as the mandrel cone, it may well be 41/2 in, on the biggest pulley of the cone, i didnt check it, but what ever it is the two cones are the same, so the ratio will also remain the same…………………….b

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