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When is 3hp not 3hp (lathe motors)?

Discussion in 'Woodturning Discussion Forum' started by Bill Szydlo, Oct 2, 2020.

  1. Bill Szydlo

    Bill Szydlo

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    I am hoping someone can shed light on this question. I am considering the new Rikon lathe primarily because it has a 3 hp motor. My current lathe, a Nova DVR is rated about 2hp on 220 so I eliminated the PM 3520C since its motor is rated at 2hp so I assumed they would be comparable. After speaking with someone they said that because of how motors are tested the 2hp PM would be equivalent to the 3hp Rikon. If this is accurate is there any way to tell by the specs exactly how the motors compare?
    Thank you,
    Bill
     
  2. Roger Wiegand

    Roger Wiegand

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    Lots of funny games played with HP ratings of motors, perhaps most famously for us of a certain age, the "Sears HP". They measured the power developed in the instant before the motor burned out, and hence could have 6 HP motors that would still run on a 15A 120V outlets. Nominally one HP is 746 watts, but that needs to be derated for the efficiency of the motor. For most motors 1 HP is in the 8-900 watt range. Wattage at normal operating speed is a first approximation, it gets much more complicated from there. The question of "at what speed" becomes important with VS lathes, the ability to have power at low RPMs being both good and expensive AFAIK.

    I suspect other factors than rated HP end up being more important in the long run. Quality of the bearings and insulation, for example. Going from a 2 HP Leeson DC motor on my old lathe to a 3 HP Baldor with VFD on my new one I can notice some difference. It's considerably harder to stall the 3HP, but still can be done with a heavy enough cut. When coring the added power is definitely appreciated. That said, the 2 HP seemed pretty good for my first 25 years of turning.

    I'm sure others here are much wiser in the way of motors than I.
     
  3. guy laizure

    guy laizure

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    Robust lathes can be equipped with 3hp motors.
     
  4. Glenn Lefley

    Glenn Lefley

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    Something not right. Rikon overstating horsepower! can someone shed light,

    power matic 2 hp Motor 3 phase 6.2 amp 3 phase.
    Rikon 3 hp motor 3 phase 14.8 amp 3 phase.

    if amp right then Rikon would be a 4 hp which is not right.

    bioth say require 20 amp breaker.
     
  5. Joe Kaufman

    Joe Kaufman

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    The VFD / Motor Controller needs to be part of the useable HP consideration. It is controlled by software and variable parameters basically unknown to the user. There are specifications as to it's design capabilities but the complete system, motor and controller operation, are not revealed from manufacturers specifications. Throw in the mechanical speed changes available to the end user via belts and pulleys or gear selection and it becomes a complex issue. A dynamometer or pony brake could be made with commercial components and adaptable to various lathe beds to measure Torque and RPM. Add a laptop and simple software and actual HP performance curve could be displayed. I would think that would generate a significant following on social media as you compared various lathes. It might also generate unwanted communication from lathe manufacturers and distributors.
     
    Last edited: Oct 3, 2020
  6. Bill Szydlo

    Bill Szydlo

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    Looking into a couple of lathes it is really difficult to get an accurate comparison. For instance looking at the Laguna 2436, PM 3520C and Rikon 70-3040. The PM has 2 hp while the other two list 3hp. In addition the various manufacturers don't consistently supply information such as number and type of bearings. I think the PM uses two bearings in the headstock while the Rikon uses four. Additionally, I assume the various components should match the motor output. Basically, my question is, how do you make an informed decision when comparing lathes?
     
  7. robo hippy

    robo hippy

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    I would guess that the Rikon ' 14.8 amps means 7.4 amps per lead wire, for 14.8 combined. Don't know. I had an old Woodcraft blue no name grinder many years ago. It was listed at 3/4 hp. I stepped up to a Baldor grinder that was also rated at 3/4 hp. The amp draw on the no name grinder was higher than on the Baldor, but the Baldor was way more powerful.

    As for lathes, 2 hp on 220 volt is probably fine for most turners. I haven't met a lathe I can't stall yet. I do prefer those few that have 3 pulleys rather than just 2. The reason for that is that the high speed range works for most of my bowl turning, but doesn't have the torque for coring. The slow speed range has the torque for coring, but not the speeds I want for turning smaller bowls.

    robo hippy
     
    Dennis Weiner likes this.
  8. john lucas

    john lucas AAW Forum Expert

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    Horsepower is often misstated and I don't know how you find out what is accurate. I have a 2hp Makita Router. My 1 1/4 horsepower Porter cable will run circles around the Makita. I would look more at the lathe specifications and how things are set up. Horsepower is only one small decision.
     
  9. stu senator

    stu senator

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    Horsepower:
    The term was adopted in the late 18th century by Scottish engineer James Watt to compare the output of steam engines with the power of draft horses.It is defined as
    "a unit of power equal to 550 foot-pounds per second (745.7 watts)

    In an electric motor this is usually defined at a specific speed and duty factor. As a lathe operate at many speeds and duty factors this term can be misleading and a torque at some speed may be a better indication of stalling. An efficient motor will run cooler and use less current.

    Different motors have different speed - torque curves and different stall characteristics and efficiencies. The same is true of the different speed controllers if used. Putting them together is something a lathe manufacturer should do to fit a function or price point.

    It boils down to what you are willing to pay and the difficulty you want to go thru to get what you want. It is probably better to use a motor that fits and a controller designed for use with the specific motor chosen and one that will not overpower the other lathe components.

    Stu
     
  10. Curtis Fuller

    Curtis Fuller

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    I wish there was an independent user rating that tracked the reliability of lathes similar to the reliability ratings of cars, similar to what Consumer Reports puts out. (Although I sometimes question the independence of CR). The published specifications of lathes seem to be like comparing apples and oranges with no standard in their comparisons. Anecdotally though, I have an older Vicmarc 3hp VL300 and a turning friend has an older PM 3520A 2hp. I can tell no difference in power when turning on the two lathes. Like Robo said, either can be stalled and actually that's a good thing. When your lathe stalls it's telling you to back off before something else gives. Both of these lathes are getting pretty "broke in". Mine is a 2007 and the PM 3520A model is at least that old and both are still going strong. If I were trying to decide today whether to buy a PM or something comparable on paper alone, I would go with the proven track record of the PM over the questionable horsepower rating of a newer knock off lathe model. About the only reasons I've ever heard for selling a PM lathe is the turner died, has health issues and can't turn anymore, or is moving up to one of the very high end lathes available.
     
    Last edited: Oct 3, 2020
  11. Joe Kaufman

    Joe Kaufman

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    While on this subject, another issue is the amount of overspeed or under speed in cycled per second the drive is using. As the frequency (cycles per second or Hz.) increases there is an increase in iron loss (recirculating current induced in individual stator and rotor steel laminations also called eddy current loses). Higher frequency operation require thinner laminations to reduce eddy current losses, reduce heat rise and to improve efficiency. Is the motor designed to accommodate the higher programmed frequency used? In talking with Robust a few years ago, the motor they used was rated for 120 Hz. but 90 hz. was the maximum drive speed used. My PM 3520B uses 137 hz at maximum speed. and about 8Hz, minimum speed. Minimum speed or HZ. concern is heat from the wider current wave forms and reduced fan cooling. Good luck obtaining that information for offshore manufacturers. The advertised lathe HP figures are not as exaggerated as air compressor or shop vacuums but they should be taken as advertisement as they contain bits of truth which may not be representative of the complete operating system.
     
    Last edited: Oct 3, 2020
  12. Bill Szydlo

    Bill Szydlo

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    Obtaining good information from offshore manufacturers is definitely a challenge. I would assume Laguna and Rikon use offshore manufacturing. Does anyone know where the PM motor components come from?
     
  13. Glenn Lefley

    Glenn Lefley

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    221017C2-715E-4E32-B456-451FC207ED0F.jpeg
    Pm and jet are the same owners.
     
  14. Bill Szydlo

    Bill Szydlo

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    So basically Rikon, Laguna and PM are all manufactured offshore?
     
  15. Glenn Lefley

    Glenn Lefley

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    yes. Nothing made in USA!
     
  16. Bill Szydlo

    Bill Szydlo

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    So, when individuals cite PM's long standing lathe quality, can it be assumed that they are now on the same par as the other manufacturers?
     
  17. JeffSmith

    JeffSmith

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    The manufacturer of the lathe - the companies doing the build on those tools made offshore (PM, Jet, Griz, Bayleigh, Laguna etc) are often the same. The customer is the marketing company that specifies the build/parts used. In order to compete the customer will compromise quality where possible to achieve the pricepoint needed. Cheaper switches may be helping offset better machining somewhere else for example. Hardened spindles, better/bigger bearings, better fit/finish all add to the cost.
    Most premium lathes - Oneway, Robust, Vicmark, Titan, etc. do their own manufacturing and maintain better control over quality throughout the process. They also have full control over parts sourcing. The result - premium lathes commanding a premium price.
    Sometimes comparisons are misleading. When I started research to buy my “last lathe”, the difference in cost between the Robust AB and a Powermatic 3520 was huge, but when comparing to the then new PM 4224 (closer to equal specs/capacities) the difference in cost between the AB and the 4224 was truly minimal.
    Buyers choice - know what the differences are and decide what you’re willing to pay for.
     
    Curtis Fuller likes this.
  18. robo hippy

    robo hippy

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    Maybe horsepower needs to be rated like dust collection systems. With the DCs, there are 2 given statistics, well for some of them. One is cfm/cubic feet per minute, and the other is static pressure. If the brand only lists cfm, they are probably over rated. The static pressure is the important measure, which is how much it can actually pull. I remember an incident some years back where an independent person was rating DC systems and one manufacturer, which I believe was Penn State, threw a hissy fit because their stats didn't measure up, and threatened legal action.

    The 6 hp motor on my compressor is about 1/4 the size of the 4.5 hp Baldor on my Laguna 16hd bandsaw...... I want truth in advertising...

    robo hippy
     
  19. Bill Szydlo

    Bill Szydlo

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    Couldn't agree more. Since there are not many lathes in the full size category I'm surprised no one has done an honest comparison/review. Possibly they are afraid how it would affect advertising but it would be extremely helpful to individuals looking for a new lathe.
     
  20. john lucas

    john lucas AAW Forum Expert

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    I taught classes to 3 of the Powermatic design engineers. The question of quality came up. They said you have to state clearly what you want and have a quality control person there to over see. If that's done you get a high quality tool. They have the skills to build high quality tools you just have to make it a priority. If you ask for lower prices you get less quality components.
     
  21. Bill Szydlo

    Bill Szydlo

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    Thanks John, your comment begs a follow up question. How do you know the quality of the components of a given lathe? I am sure that if a company makes that a priority then they can accomplish it but how does a consumer tell the difference? Throughout all my years woodworking and woodturning there seems to be extensive reviews of standard woodworking tools but not so much when it comes to lathes.
     
  22. Emiliano Achaval

    Emiliano Achaval Administrator Staff Member

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    Maybe we need to know the size of the horse they use to measure the power. Was it a draft horse or a miniature Falabella horse? A fast thoroughbred or Quarterhorse? LOL
     
  23. Roger Wiegand

    Roger Wiegand

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    Fortunately lathes are extremely simple machines and almost every component is readily available for tactile and visual inspection. Often the only hidden parts are the bearings. Even then you can at least see what they used for the outermost ones and in a worst case they are usually pretty easy and inexpensive to swap out. If proprietary motors and speed controllers are used those can also be difficult, but at least they are, frequently, ephemeral parts relatively easy to swap out in the event of failure (I wouldn't buy any lathe where this wasn't true). Visual inspection will tell you a whole lot about the quality of the castings, the subsequent machining, and the welds. Sloppy welds may be structurally fine, but they are a warning to look deeper. Operation of the tailstock quill, sliding and locking the tailstock and moving around and using the banjo, being mindful of odd vibration, play in the parts, and any stickiness will tell you a lot more about the quality of the machining.

    We aren't machinists trying to work to 0.0001" tolerances; the kinds of flaws in machining that affect our outcomes are, I think, pretty readily detectable as movement we can feel that shouldn't be there, stickiness that shouldn't be there, and simple tests like checking runout and moving the tailstock around and seeing whether the points on the drive and tailstock centers still line up.

    I'm not sure I've ever had a woodworking machine (of any sort) where careful attention to the small details and fit and finish of the machine was paid to inferior components. If the maker has sweated the details I've found it generally safe to trust that the major components are also good.
     
  24. john lucas

    john lucas AAW Forum Expert

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    Bill. I have no way of knowing how you can tell.the quality of components other than tryi g to follow things like the number of complaints about the equipment. And we really have no way to follow that. At least not with any accuracy. I'm sure the companies arent going to volunteer this info. And in reality they may not even know. They ask for a lathe to meet an price point and the company complies. Then they can inspect the final.product and say yes or near. The problem.is you cant just look at a bearing or electronic component and tell the quality without doing a lot of research. So really the consumer can only come to places.like this and other forums and ask if their are complaints. Its really a lot like buying a car. You base your decision on price and the reputation of the company. How do you find out about the quality of components in a new car. You really dont other than a few years later when recalls.come out.
     
  25. hockenbery

    hockenbery AAW Advisor Staff Member

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    I thought you were a polo pony guy :) When I was a kid we had a team of Belgians and they were gentle giants - lot of horse power.
     
  26. Doug Rasmussen

    Doug Rasmussen

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    There's all sorts of funny business in rating horsepower of electric motors as others have mentioned.

    I like to go by the Full Load Amps (FLA) rating of the motor as shown on the motor's tag. Even this is not totally fool proof though since it can depend on the motor's efficiency which you don't know. Still better than just relying on the stated hp rating.

    Checking on a few my industrial grade motors, Baldor, etc, there's maybe a +/-10% variation between HP and FLA on different motors, not a major significance IMO. No where near the exaggeration of a Sears 4 HP compressor motor running on a 115V, 15 amp household circuit.
     

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