Torque

Not easy to answer.

The differences between the motors themselves are not very interesting here, I think; in "normal" use, they are marginal.

The systems for differenciating speed are far more important when it comes to "power on the spindle", the various electronic systems normally being superior to most mechanical ones, with the Nova DVR probably on top.

I now use the Vicmark with electronics. I am never at a loss for power.

But then, I also got used to my old Record with 1/3hp motor, and _that_ was enough for most of my work, up to bowls of 20".

Bjarte

I can give you a very unscientific evaluation of my own experiences. I have turned on just about every lathe on the market, with the exception of some lower end lathes like the HF, etc. Currently in my shop I have two machines with comparable motors, a Poolewood Euro 2000 and a Vega 2600. Both have 2 HP 3 phase motors.

It is almost impossible for me to stall my Poolewood, and I am what might be called an aggressive turner. Aggressive is defined (I timed myself for a student a few weeks ago) as going from rough blank to finished on the outside and ready to reverse for hollowing in about four minutes on a 12" x

5" blank of wet maple, turning at about 700 rpm. About the only ways to stall it are running it very slowly, around 200 rpm or less, or jamming my 3/4" Glaser into a 20"+ blank, again while roughing out less than 500 rpm, or really jamming in a Kel McNaughton coring tool while coring out 12" bowls from 15" bowls or so. However, the jamming from the KM tool usually happens because the tool rest slips and the curve of the bowl is causing the binding problem. I usually core at 750-800 rpm, and the cores come out in less than a minute. It is much easier to stall the Vega, although it still has lots of beef to it. Going back to my first comment above, I have found it relatively easy to stall a Stubby, a Vicmarc, and an Oneway, although in some cases it was more of the belt slipping while in others it was stopping the motor.

I think that the direct drive of the Poolewood is what gives it its edge. However, it is my understanding there there is not much in the way of Poolewoods to be had, and I do not think that Silverdrive has their machine ready for market. From all I have read, they seem to be doing their best to offend as many people in their potential market as possible by refusing to return calls, emails, etc, although this is just from what I have read. Perhaps that is not really the case, but I have not tried to contact them, nor have I seen any machines for sale. Of all the other lathes, I think that they are going to be fairly equal in their power output when comparable motors are used.

I have a General with a 2hp 3ph variable-speed drive. It also has a 4 step pulley system which you can use to get the torque up for big pieces. On the lowest speed pulley the max rpm is around 625 whereas on the highest it is about 2900 which is a 4:1 multiplier in simplistic terms. For turning 12-16" wet maple it doesn't seem to matter which pulley I use. I often have the belt set 1 below the top speed pulley. If the blank stops it is always due to belt slippage which I deliberately run a bit loose. FWIW, Billh

I have the PM3520. It has two pulleys, and a 3 phase 2 horse motor. In the low speed range, when it down to the slowest that you can go without it stopping, I can stop the motor. At any higher speeds, I can get the belt to slip, but can't stop the motor. In the higher speed range, it is much the same thing. If I am turning a 14 inch by 6 inch bowl, I can trip the breaker on the lathe, but can't do it with smaller pieces. I can still make the belt slip, but can't stop the motor. I have turned on the 1 1/2 horse Delta, and it doesn't have nearly as much torque (or at least not as much as I would expect from 1/2 horse less than my PM), even in the slower speed ranges. I am curouis about the Nova DVR, but haven't had the chance to try it out yet. robo hippy

Therein the answer. Unless you're showing off or production turning, cutting the wood can be done with rotational inertia alone. Much easier on your forearm and elbow as well as the lathe itself. Pretty rapid if you do it properly, as well. You might have to sharpen a bit more often.

Outsmart the wood rather than purchase a beast or turn into one.

Most answers are using 3 phase which is a lot more expensive to bring to a house, I understand, or even a shop.

Wonder what the difference is between 115v and 230v with still the same horsepower? Seems the 230v would perform better, particularly at slow speed. Costs more to get it and sometimes you have to use an inverter which seems like another thing to go wrong.

I'm looking to get a Jet 1642 with 115v and this concerns me. Certainly 115v is more versatile.

My biggest concern is not stalling, rather it's frequent stopping and starting with heavy green wood.

TomNie

Under ideal circumstances, a 2 hp motor will deliver the 2 hp whether

115 v. or 230 v. The problem is that we are seldom dealing with ideal circumstances. The 115 v motor will draw twice as much current as the 230 v motor and the drop in voltage over a wire of a given size and length is mainly a function of current. So, you would need much larger wire to deliver a true 115 v from your panel to your motor. Since it is unlikely that your house is wired to do that, it would be necessary to run a new circuit. As long as you need to do that, you might as well run a 230 circuit and save yourself some time and money -- you don't need such a large wire.

Three phase is not just expensive, it is just plain unavailable in residential areas and also in many commercial areas.

The advantage of 3 phase motors is that they are cheaper to build (both because they are simpler and because they are used by the millions in industry), can be made to run in either direction easily, need no starting circuit and no capacitors (a major cause of motor failures) and are pretty much bullet proof. If you drive a 3 phase motor directly off the power company's line, though, it runs at one speed -- the speed it was designed for.

The VFD, then, gives us the best of all worlds. It gives us the ability to run a good, relatively inexpensive motor from single phase and it gives us variable speed, proper braking characteristics, soft start and stop...

There have been attempts to run lathes with 1.5 or 2 hp motors from a

115 v VFD which have been less than successful. The reason is the same as above -- by the time you get enough current to the VFD, the voltage is too low due to resistance in the wiring of your shop.

I hope that this helps on some of the issues.

Bill

Tom Nie wrote:

Tom, most of the lathes sporting 3 phase motors run on single phase current, so the only real expense in bringing it to the house, so to speak, is in the lathe itself, and some extra for the wiring up of a 220 v line if you do not already have it. The "magic box" on the lathe converts the single phase to

3 phase and as Bill R. mentions, gives a very luxurious variable speed control complete with braking, reverse, etc.

A friend of mine has the Jet 1642 although I do not recall if it is wired for 110 v or 220 v. I have turned on it a couple of times, and it is a very nice lathe. The biggest issue I have discovered with frequent stopping and starting (on any lathe) is when the blank is really heavy and out of balance. It can sometimes unscrew itself from the spindle while the lathe is coming to a stop, which is always exciting. Using the tailstock for support is a good idea. As far as wear and tear on the controls themselves, my Poolewood has seen very heavy service for over five years now, with lots of newbies turning on it and turning it on and off frequently as well. I had to replace the speed potentiometer for something like $12.58, and the switches sometimes need dust blown out with compressed air, but that has been the worst of it.

Torque increases as the motor approaches a stall. The joy of a VFD is _low_ torque if you're speaking of starting, stopping and other variable loads, for which it increases current in an attempt to maintain constant rpm. That's the principle behind soft start and electrical braking. Capacitor-start single phase give a huge kick then cut to run.

As 220 V has twice the potential of the 110, a 220V _only_ motor should be able to run under greater load at lower speeds than a 110 or dual-voltage motor. The controller provides a variable voltage to frequency ratio to do so.

Just mentally substitute tool pressure for flow control in the following for a good picture. Once again, the best thing for operator, machine and electric bill is to cut with less pressure.

I have heard a lot of people say that a 120 volt motor uses twice the current that a 220 volt motor does. Don't they use the same amount? A

15 amp motor still uses 15 amps, but it is drawing from 2 leads at 7.5 amps each instead of one lead at 15 amps. robo hippy

No. The current still goes in one wire and out the other. The amount of power (volts x current) is the same.

110Vx15A = 1650W and 220V x 7.5A = 1650W.

There is no real advantage to running a motor at 220V instead of 110 if the supply wire is of adequate size for its length. If the wire is too small then the larger current will cause more voltage to be lost from your panel to the motor. That said, I tend to run any of my dual-voltage motors at 220V since I prefer connections (at the breaker, screw terminals, wire nuts...) carrying less current and it also more or less guarantees that my wire size is good.

Billh

Motor is rated in horse power or fractional. A horse power is 745 watts IIRC. If a 120 motor uses N current - the wattage is 120 * N in VA - indicating not real wattage but one that may contain imaginary components. (phase angles and that stuff - )

When the motor is on 240 - then the current is 1/2 the value or the motor grew somehow. The VA value is the same - the horse power value is the same.

Higher voltages require lower currents for the same power.

Martin Martin Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net NRA LOH, NRA Life NRA Second Amendment Task Force Charter Founder

robo hippy wrote:

Billh

Be patient. Let me be absolutely sure I understand.

I'm hearing that with sufficient size(? -30'-10gauge) wire there is NO FUNCTIONAL difference - even at slow speeds - 230v versus 115v.

Also, I'm thinking that we pay for KWH which would remain the same either voltage BUT that furnaces, ovens, dryers, etc. use so much amperage that it becomes sensible to make them 230v because of wire cost. Is this correct?

Really helpful discussion during a lathe decision - Thanks Guys. TomNie

Almost true. Without a vfd you can't get slow speeds -- only the speed the motor was designed for. With a 3 phase motor and vfd you need 230 because there are few vfds which run on 115 for anything over about 3/4 hp.

Correct. Actually, the thing which makes no sense is using 115v for anything. Most of Europe uses 220 for everything and that makes a lot more sense. Many factories, btw, do not use 220 3 phase power, they use

440 or greater. Same deal -- lower wiring cost.

Bill (the wrong one though)

The 230 would give you more instant on since the copper loss on the same wire is much less. Half the current due to double the voltage. Half the current and now an over rated wire - so it isn't pushed and doesn't have much copper loss. The motor starts easier (normally).

I'm doing 3 phase at 380 for the same reason. I could have re-wired 6 motors (what a job) and they are 1950 and 1960 versions so EIA didn't drive spec drawings or cable labels... So I opted to just build up a converter and provide the industrial voltage.

The cables for multi-horse motors are thin. Look like 16 ga. Maybe 14. I'll have to measure.

My converter box will use #4 internally in the 220 section and (not there yet) likely 10 for the 380.

Since it is higher voltage, leakage currents are tricky - in the plug to the hand... and such - but I am safe and work with high voltage. We shall see.

Conversion down is easy if I have to change.

Martin Martin Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net NRA LOH, NRA Life NRA Second Amendment Task Force Charter Founder

Tom Nie wrote: