What is the lowest useable RPM that this lathe will run under load??
Some of the literature says 100 RPM, but most of it stresses the 3000 RPM top end, and ignores the lowest speeds. Woodcraft doesn't know, and their only answer is that nobody has complained. I have seen only two (2) DVR's in real life, and neither of them would run below 300 RPM.
I want to buy one (1) and maybe two (2) lathes for students and have been considering either the DVR or the Nova-3000 with the variable speed drive. The speed issue may drive me towards the 3000 with a variable speed motor.
>Russ, I am not familiar with the VS Nova, which I am seriously considering as an additional, bigger lathe. I don't know what kind of motor and control are in this lathe.
I have heard many comments about variable speed DC motors losing torque at slow speeds. The reason mentioned is that the control varies the voltage, and of course, at low voltages the torque suffers. For this reason a frequency drive AC motor is often recommended.
While it is true that some DC controllers vary the voltage, this is not true in all cases. I have a metal and a wood lathe that have DC motors driven by CHOPPER circuits. This is usually called PWM - Pulse Width Modulation. The controller varies the CURRENT, not the voltage. It accomplishes this by sending shorter pulses when a slower speed is required.
Now comes the interesting part. These controllers usually (but not always) have internal adjustment pots which control the minimum and maximum speed, and sometimes maximum torque. They are set at the factory, with a drop of glue to hold the setting.
I installed a DC motor in my Jet Mini. The motor has an encoder (wheel that sends RPM signals to the controller, like a tachometer). The speed is set in the dial, and the circuit maintains a constant speed even if the torque requirements vary. Very smart circuit, analog to a servo motor.
For those who would be interested in a DIY DC VS, top of the line DC controllers (Minarix) are available for under $60. These are suitable for smaller lathes, with up to 1 HP power requirements.
It would be beneficial to find out exactly what kind of motor and controller comes with the VS Nova. I would not buy a variable voltage DC motor at any price.
>My NOVA DVR runs well (lots of torque) at between 100 - 200 RPM. The speed range goes down to at least 100, and maybe even a bit lower, but I'm not sure. I'll check tonight. Mine is a year old now. I understand that some of the earlier DVRs could only go down to 250-300 RPM.
There is a NOVA DVR user group out there, although I haven't been to it in a long time, and don't have the URL on this computer. Should show up in a search though. This issue is well addressed in the archives of that user group.
One of my lathes is a Nova DVR. I have one of the earlier model. My lowest speed is 500 rpm. The updated model as stated here and elsewhere will go down to approx. 100 rpm. I think the motor has more than enough torque for around use. I like the controls right at hand for quick changing and stopping. I will give the group link for the Novas. GT
>Russ, I have been turning on a DVR for a couple of years. The lowest speed on my DVR is 100 rpm. There has been a lot of discussion on the low end torque or lack of it. The DVR can be powered by either 115 or 220. They come wired for 110 but the change to 220 is fairly easy. (See Technitool website). I have not changed mine to 220 as I have not had a problem with the low end torque. When turning large pieces at 100 - 200 rpm I learned to make light cuts and felt it helped my tool control. If I got a big catch the lathe would stop until I removed the tool and it would start right back up. This saved me from breaking my tool, my rests, or my head.
Above about 300 rpm the lathe does not stall. I looked at the lack of low end torque to be a safety feature.
I looked into this pretty extensively from last March to July, so my information may be a few months out of date...
What I learned at that time was that the standard configuration, run on 115 volts, had a low speed of about 200 - 215 RPM. The circut can also be wired for 220/230 volts, and can then run down to 100 RPM with good torque.
It would be worth checking in with Lyn Mangiameli on this, who has really studied the minute details of this lathe. Most reviewers have concluded that it is the best and smoothest spindle turning lathe they had ever turned on. As of last summer, the only small drawback to bowl/faceplate turning was the built in safety feature to cut power to the motor when encountering a big catch (or a sharp spike in rotational resistance as seen by the motor). For roughing or coring large, uneven chunks, which is often a herky-jerky process until the blank is balanced, some have reported annoyance with the motor control circuit cutting power, and needing to be restarted. Teknatool was working on this, and may have come up with a good solution. I thought an optional switch to turn this controll feature on and off would be a good solution. This seems a very reasonable safety feature for a teachuing lathe, though not so great for a production lathe.
As for the question of the motor/controller type, it is unlike that of any other lathe I know of -- DVR means digital variable Reluctance, and the motor is the simplist design I've ever seen -- 1 part moves, one stays still, plus bearings. The reluctance part I still need to learn a lot about !
My research was on behalf of a local turning club, and we eventually decided on the Nova 3000, retrofitted with a variable speed motor operating over 8 speed ranges for high torque, low speed coring and roughing capability, but when I buy my own next lathe, the DVR is probably the first one I will consider -- a very nice machine.
>I was lucky to get a surplus motor from Vega early last year, complete with controller for about $50. This is a bargain that will not be probably repeated.
In addition I bought a new pulley from Jet, because it needed to be bored slightly to 5/8". I wanted to leave the existing pulley in the motor. A new, longer belt was purchased from Aarubco Rubber. They have the 3 rib J-section Poly-V (serpentine) belts in all sizes. Inexpensive and shipping cost is low.
The old motor is still in its original location under the bed. It takes only a belt change to use the old motor.
I built a cabinet for the Jet Mini. The motor is mounted under the lathe. All I had to do is connect it to the controller, and plug it in. Other than the cost of the cabinet, I spent about $80 including some hardware.
A brand new surplus controller and surplus 1-1/2 rated HP motor (take out from treadmills) will run about $100. Other than hardware and some connectors, that is the total cost. I would still mount it under the lathe.
how tough is it to wire up that minirix controller. i have a treadmill i am in the process of dismantling.. and was checking out that controller in the surplus center catalog.. i just am not an electronics wiz.. and was curious how easily it is wired..
>The Minarik controller from Surplus Center is real easy to wire up. There is a power cord of course. I would put a power switch someplace. Then there are the wires to the motor.
The speed is controlled by means of a potentiometer. This is just like a volume control in a radio, with a knob on it. It has three wires. You mount the pot in any convenient place, and wire it to the controller.
There are a couple of switches. These have to be set. One is for the input AC voltage, 110 or 220.
The other is for the output DC voltage, 90 or 180, according to the motor you have.
It comes with instructions. Matter of fact, too many instructions.
The main thing is the pulley on the motor. Check and see if you can use the one already there, or if you can fit the right one on.
>I have a DVR that is about two years old. The speed range is from 250 to 3500. I use the 250 speed frequently for roughing large blanks and for power sanding. It does stop if you get a big catch but it starts right back up, unless you stop it over and over about three times, then it stops and you have to restart it from the controls. Almost as if they programed it to say "Amateur!, take a break, think, and try again."
I have read that the new ones start as low as 100 RPM, but there is one at the local Woodcraft store and it starts at 250. Not sure why you would want it to start that slow. 250 is so slow you can watch the lumps on the blank coming.
Converted mine to 240 current. Easy to do, excellent instruction available over the net from Teknatool. Seems to give it a little better torque. Good, but not astounding improvement.
No belts, no pulleys, just push the buttons and go. I would buy it again. Also, easy to add a vacuum chuck.
The problem with talking about the DVR is that there is no one DVR. The contol and drive circutry has been modified over a half dozen times, each with some discernable change in performance. There are a few trade-offs that must be managed and not all versions behaved similarly, even though the most obvious parameters such as minimum speed might have been the same.
I have one of the older versions with a 250 rpm minimum speed, run on 230 V. Power is not so much the issue with mylow end as it is the speed control sensing. The lower the rpm, the fewer corrections available per second.This makes sudden variations in load more difficult to correct for,and may lead to more frequent interrupts. As for power itself,the DVR has loads of power,way above what it is rated for.The key at low speeds is to apply the load evenly, to allow the DVR to smoothly apply that power.
That said, Iactually probably am discussing issues that are not nearly as prominent,if at all, in thelatest versions. I am supposed to be getting the latest boards in the next month or so, and I will be better able to discuss current performance then. I've been told my DVR is like a "Model T" compared to the latest boards.
Personally, I believe the DVR would be an excellent lathe for student's. The power interrupt features will take the drama out of severe catches, and as said earlier, cut the power for only a second or two, allowing the thoughtful student to back off and then start right in with better technique.
In general, I've been staying out of most DVR discussions as I don't feel my DVR is representative of the current models. When the new boards come I'll update my old reviews and be a bit more active in commenting on threads like this.
I think you have pushed me in the direction I was going already, and that is to NOT consider buying the DVR. I want a lathe that will do what I want now, and not one that is a work in progress. There are too many other options out there.
As far as it being a good student lathe because of the low torque and slippage at the bottom end, I can do that by loosening a belt.
>I think you need to look at the DVR vs 3000 like looking at a 60's car to a 2000 car. Upgrades are chip/firmware based, not hardware based. If you want more performance from the engine in a 60's car, you're looking at alot of futzing with hardware. With a modern car, its as simple as a chip replacement or reprogram. Clean, easy and relativly cheap. It *WILL* do what you want now...and better in the future.
I've used my DVR for almost a year in production. It beats the pants off the 3000 in smoothness and power. The only thing that really irked me was the time it took to change speeds (10 seconds is WAY too long for a production turner). I think the DVR would be a perfect lathe for teaching students. The time spent changing belt positions alone would mean more time with the students. Not to mention the fact that you can't "accidently" turn up the speed too rapidly while its on.
The Nova 3000 with belt and pulleys has a lower speed of 180, I am not at home and cannot verify this, I will correct this post tomorrow if I said the wrong thing. That slow speed is very slow and it is good to have when mounting unbalanced blanks.
>Is this smoothness an instantaneous feedback that keeps speed constant with miniscule changes in the wood or tool application or is there less vibration or spindle runout compared with the N3K or what? I suppose the extra power is an advantage for bowl saving, if that's what you plan to teach. but IMO the N3K with VS is entirely adequate to learn on and may even have some advantages. Not the least are less cost and being able to ramp up from or down to zero rpm.
After all Russ, it's your knowledge and abilty to impart it that is important. I'd learn more from you on a vertilathe than from some (who shall remain nameless) on a Oneway.
>If you have a treadmill you already have the controller. The only problem with the controller is that it is a very high speed motor. You may need to use a jack shaft to reduce speed. I had to open mount my box or it would get quite warm and trip the relay on overload.
