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24th July 2021, 09:44 AM #16
The only time I wish I had a bit more neddy than my VS 1.5HP is when I'm coring larger diameter blanks. Coring is one of the most HP demanding tasks on the lathe. My 1.5HP struggles with that when cores get up around 18" diameter.
A 2HP unit would be more than adequate for my purposes if I was not coring up to that size. Even with just 1.5HP I can manage to do regular turning up to 21" diameter outboard.
Stay sharp and stay safe!
Neil
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24th July 2021, 10:07 AM #17.
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It depends how often you expect to be operating at lower motor speeds.
A 3 Phase motor that runs at 1440 rpm using a VFD will have full power only from about 50 to 100Hz or 1440 t0 2880 rpm.
Above this speed the power drops off and running at really high speeds is not safe so a max of about 125Hz is recommended.
Below 50Hz power drops off proportional to Frequency.
A standard VFD (known as a V/F VFD) only has half power at 25Hz.
There are two ways that help this.
The easiest is to get a more powerful motor.
Doubling the motor power will produce the original motor power at 25Hz.
The next is to get a "Vector Drive" VFD. This produces more power at lower frequencies.
This is not an automatic gain and some fiddling with the VFD parameters and running an auto tune is required.
The actual power gain varies but a well tuned VFD will nominally produce the same power at ~12.5Hz that a V/F produces at 25Hz.
Real wins occur at very low frequencies (eg 5Hz) where a Vector drive will be producing even more power than what a V/F VFD powered motor would output..
Sounds Good eh, BUT
Running at low speeds can lead to over heating as the motors fan may not turning fast enough to cool the motor.
A bigger motor helps simply because it has a greater thermal inertia but only for a while.
This can be more effectively dealt with by adding an independently powered fan like a large computer fan.
There is a temptation to get extra large motors but this can lead to unsafe situations like damage to the lathe if something gets stuck.
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24th July 2021, 11:25 AM #18Novice
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So 2hp in place of 1hp is probably okay, unless I had plans to increase my swing with a riser.
Using the current drive pulley, lowest speed of 350, I will still have 1hp down to 175rppm
At this point 600mm platter and 400mmm bowl is probably all ill be doing.
Is that ebay linked combo what I should be looking for.
Garry
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24th July 2021, 11:59 AM #19
That is not a terrible price for a motor VFD combo. You could get it cheaper if you shopped around a bit but Conon are pretty good to deal with.
The motor by itself is around $250. Getting decent VFDs is becoming more expensive and that is not a vector control VFD. They recommend that combo for a belt grinder, which you pretty much run flat out most of the time anyway so it would be fine for that but I would look at a vector control VFD as Bob suggested.Those were the droids I was looking for.
https://autoblastgates.com.au
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24th July 2021, 12:33 PM #20.
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24th July 2021, 12:38 PM #21Sounds Good eh, BUT
Running at low speeds can lead to over heating as the motors fan may not turning fast enough to cool the motor.
A bigger motor helps simply because it has a greater thermal inertia but only for a while.
This can be more effectively dealt with by adding an independently powered fan like a large computer fan.Inspiration exists, but it has to find you working. — Pablo Picasso
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25th July 2021, 10:17 AM #22
Like Jim (Powderpost), I also retrofitted a VFD unit (I presume that was what it was) to a Woodfast back in the 1990s. It wasn't cheap at the time but it was a quality European unit and of interest to this discussion is that it ran down to just 10rpm on the lowest pulley setting, which was very nice for particular tasks like sanding warped pieces.
That lathe had quite a big left hand outboard swing and I don't remember its 1HP ever flinching at anything I put on it for regular turning.
My current Woodfast (C1000X) only goes down to 20rpm, which is slow enough for most purposes, although I did find a noticeable difference between 10 and 20rpm, which I wasn't expecting.
Vicmarc still have lathes that go down to 10rpm.Stay sharp and stay safe!
Neil
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28th July 2021, 04:25 PM #23Member
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I converted a wood lathe using a sewing machine servo motor. Sort of like this Lathe Motor upgrade - adding a 550w 3/4hp brushless servo sewing machine motor - YouTube
Motor cost me a little over a $100 USD. Nothing else needed to control it, but I did add a sperate pot to control it at the front of the lathe.
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29th July 2021, 01:27 PM #24
I could see that this is an economical solution for some small diameter work, like a dedicated pen turning lathe. But, I would miss the auto soft start for larger diameter work that is built into my VFD. With a pot you could probably manually wind up the speed gradually to replicate that and that may be ok if you are not frequently stopping and starting all the time. But that might be a minor inconvenience if you are wanting to save some dollars.
However, I don't know just how economical this style of servo motor unit would be for larger diameter wood lathe work. Here are two offerings as a retrofits in the 1.5 to 3hp range...
Amazon.com
https://www.ebay.com.au/p/2181125437
Most lathe manufacturers go with a VFDs and 3ph induction motor for VS control, but I can see that Harvey is using the servo motors on theirs TURBO T-60S 24"X48" Wood Lathe With Servo Motor – Harvey Woodworking
Some discussion in the following on the use of servo motors on wood lathes...
Servo motors vs the other motors | American Association of WoodturnersStay sharp and stay safe!
Neil
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