How much for a larger motor and VFD/Inverter? Cost? Advantage over new?

[Gregory of Sherwood Forest]

I'm considering an investment into a larger lathe, and some of the options are vintage Powermatics, Generals, or a monster Oliver.

Here's the issues:

1) I only have 220v single phase in my shop.
 
2) Any of these lathes have a minimum speed range of around 500-600 RPM's, but I'd like to get down to 100 or even slower. I've found that I enjoy turning larger platters and bowls.

3) The vintage lathe's that I have to choose from right now have motors around 1.5 - 2 HP. I'd prefer 2-3HP.

What I'd like to do before buying (I may buy as early as next week) is get an idea of what I'd need as far as a new motor and an VFD/Inverter.


So, what expenses am I looking at? What are my options??? Is there a company out there that specializes in this and I could buy a matching package to get this done?

If costs are too prohibitive, perhaps I should just save my WW pennies a bit longer and just get a new lathe in the $3k range.


Thanks in advance.

[cvillewood]

If I were you I'd use the lathe as is, once you buy it, and see if you need more power (unlikely?). You can get a good TECO FM50 from factorymation 3hp VFD for under $200. If get that and it'll work on a 1.5hp motor or a 3hp should you upgrade. Used 3phase motors can be had cheap.

[Gregory of Sherwood Forest]

I will give it a tryout as is, but my main reason for wanting to make the changes is to get a lower speed range.

My favorite turnings are large platters. I've now made a couple over 2" at a friends lathe and I'm addicted. Unfortunately, It seems to be almost necessary to have a slower speed (60-100 RPM) to get much larger, and also keep the HP so it doesn't stall the turning.

I'm positive I want that slow range. Now, I just need to figure out what I need, equipment (motor/VFD) AND expense.

[OneStaple]

A few thoughts for you from someone with an old Oliver lathe (model 2159) from the '60s. Mine has a 1HP 3-phase motor with a VFD. I put riser blocks on to increase the swing from 14" to 19".

Older motors seem to have more power than new ones for the same HP rating. I haven't researched it in a while, but my understanding is that it has to do with the measurement technique (hp at stall vs. operating HP or something). Seems like an old 1HP motor has the same umph (technical term) as a new 2HP motor or so. I'm sure someone will better explain or correct me. Either way, even with a 19" swing that I've maxed out, I've always had adequate power. Might be worth trying the original motor before changing it.

When it comes to VFDs, get one with senseless vector capabilities. Using that mode gives you full (or nearly full?) torque at the slower speeds. You want all the torque you can get on a big platter. The FM50, while good, is not sensorless vector. I'd recommend the Teco L510 line. They're a hair more expensive, but give you sensorless vector. 2HP is about $173 and 3HP about $207. I'd also recommend some sort of dust enclosure to protect them. I lost one because I didn't and sawdust got in. Most VFDs are sold with a NEMA 4 enclosure option ($$$). I built my own with an ammo can.

I love my old Oliver. Good luck!

Tyler

[thomasegan]

The term "sensorless vector drive" was always a mystery to me.  I have a VFD in a box, not yet connected to a machine......
 
I did a quick search and found this:   http://www.practicalmachinist.com/vb/tra...ve-276144/

 I trust it is pretty accurate since the PM site has a deep knowledge base.  

  I agree, in general, with the recommendation to go with the lathe as-is, and see how it does. 

  Keep in mind that if you increase motor HP, you will need to -- if the lathe has a magnetic starter -- get new heaters (like fuses) for the appropriate rated amps of the motor.   This may not be an obstacle, but an added expense of perhaps $10 to $20 and that assumes the heaters are available and the starter can handle the higher amp current.  

   a chart for sizing starters to HP,  single phase and 3 phase:   http://www.southlandelectric.com/motor_s..._for_s.htm

[MichaelMouse]

Consider countershafting.  You have MORE than enough ponies already.  After all, how much does it take to remove a shaving.  You do it all the time with just Armstrong rating when carving. 

Or, just get a Nova shortbed.

[EvilTwin]

Im as much an old arn guy as they come, I have a whole shop full of older, larger equipment.  I had a 12" Delta VS speed lathe for probably about 10 years, and while it served my needs, it wasn't good for larger turnings.  So when Woodcraft had a sale on the new Nova DVR lathes, I hemmed and hawed a bit but eventually bit the bullet and got one.  While I will be the first to admit that the build quality of anything that is coming out of China doesn't hold a candle to the old stuff, the features on these new machines really can't be matched.  In particular, this Nova DVR has a nominal 16" swing, but if you pivot the head about 30-45 degrees off center, now its probably around 18 or more.  Pivot it to 90 and use an outboard stand and its whatever you want.  The motor can go as slow as around 100 rpm or up past 5000 and there are no belts, its all direct drive.   And it's very quiet and smooth.  

The good thing about old iron is that you generally don't loose any money on it.  If you buy and old machine and fix it up and use it, you can generally sell it for what you paid or a bit more if you improved its condition.  Not so much on a new piece of equipment.  But you also get to a point in life where you can say it's worth it to me to spend the cash to get what you want and enjoy the hobby, rather than always trying to save pennies and make do.

As for VFD's, to stay on the original topic, as long as you keep the motor below 3hp,  the VFD is a good route to go.  Agree with the sensorless vector type, they will keep torque up at a designated speed and allow you to slow the output way down.  I'm running 3 machines right now using VFD's and have not had any issues.  

[cvillewood]

I'm not certain, but I don't think the older motors rated at say 1 hp had more like 2 hp today. I think the older motors where just bigger and heavier and had larger rotors which had more mass therefore they wanted to keep spinning more than today's smaller motors. An OWWM expert could confirm.

[EricU]

my lathe got converted from 3 phase to single phase.  I think I have the original motor, sort of by random happenstance.  I never really thought about the advantages of speed, but I did want to convert it back.  I think I will now.  Probably get some money for the single phase stuff while I'm at it.

Older motors are less efficient, and newer motors are more likely to be happier about being driven by a VFD.  I know there is a lot more copper in an older motor, and there are probably some advantages to that. I have never had any problems driving an older motor with a vfd, but there are plenty of warnings out there against doing that.

[TDKPE]

The nameplate HP rating of most motors is a continuous output value, as determined by the internal temperature of the windings under load, and the winding wire insulation value.  Old motors had, by today's standards, wimpy insulation (low temperature), and tended to be larger for that and other reasons.  But the output power was based on winding temperature, deep inside the windings where it's hottest (the so-called 'hot spot').  If a motor could be made smaller or with less copper for the same continuous output power and insulation value, it would have been.  Old motors didn't normally even have a box on the nameplate for insulation class, as they all had the same thing; there was nothing else.  I don't recall now if they were equivalent to Class A (105 C/221 F), or was even lower than that.  Today, the highest class is, I believe, Class H (180 C/356 F
).

There are, of course, motors with other than continuous output ratings, with unconventional torque curves (NEMA Design 'D', for instance, which has no breakdown torque, similar a DC motor), torque motors (which sit stalled, often continuously, like a ventilation damper motor), and others.  And there are single-phase motors specifically designed for higher breakdown torque, for short duration, than 'normal' motors, like the old Unisaw R-I motors, where you could push it farther beyond its rated output power than a 'normal' motor before it dropped suddenly in speed to a crawl, or stalled.  Today, they just use a higher hp motor, but back then, a 1 or 1.5 hp Unisaw motor ran like a 2 or 3 hp of today, because they were designed to work beyond their continuous output rating (for short duration) without letting the magic smoke out, and the breakdown torque value was higher than common motors of today.