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Motor options for a rather large lathe.

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  • Motor options for a rather large lathe.

    Hello. 1st post here. Be gentle please.

    I've got a little lathe running a 3 phase motor through a single phase inverter.

    I like having the easily adjustable speed.

    I'm picking up a considerably larger (huge) lathe in about a week and need to think about how I'm going to power it.

    I've got a 3HP induction motor on my bandsaw that could be re-purposed (it's way too big for the bandsaw) but there will be no speed control apart from swapping pulleys on the counter shaft.

    I've also got a couple of 2000W brushed motors from some old chopsaws that could be re-puposed. They'd need to be geared / pulleyed way down but that's doable, and the speed can be adjusted via a suitable controller.

    I know I could get a big 3 phase and an inverter but I like to work with what I have (if possible) but I'm open to all suggestions.

    Also, I like to go cheap if possible!!

    Has anybody here used a brushed AC motor to run a lathe?

    Any opinions would be most welcome.

    Thank you.

  • #2
    First, welcome to the forum. It's populated with considerable experience in a wide variety of subjects in addition to machining that are eager to help.

    What is the make, model of the new lathe? Does it already have a motor? When you say "huge" keep in mind that's subject to interpretation.
    Last edited by tom_d; 02-06-2021, 06:01 PM.

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    • #3
      Welcome.

      Mentioned above but we are going to need a few more details on the lathe.

      3hp is not all that much for a “huge” lathe but your definition of that may differ from others.

      I’m going to take a guess and say this is an old belt driven line shaft lathe?

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      • #4
        Thank you for the welcomes. Very kind of you.

        My little lathe is a 100yr old 3" RandA. Currenly undergoing a bit of a reworking.

        The 'new' lathe is a 10" about 75 to 80 yrs old.

        Oxford is right...I’m going to take a guess and say this is an old belt driven line shaft lathe

        It's far bigger than anything I ever imagined I'd get, but I enjoy the challenge of such things. It'll need to be stripped down to component parts just to get it through my house and down to my small garden hobby workshop. No idea how I'm going to even get it home! But that's all part of the fun.

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        • #5
          Welcome to the forum.

          10" swing... radius or diameter? 3 HP on a 10" diameter swing lathe is quite frankly a ton, and I can't think of anything but a very beefy tool-room lathe that would have that much power in that size. Lathes of that period would be suited for about 1/3rd to 1/2 HP in that size.

          Since you said "rather large", I'm going to assume it's a 20" diameter swing lathe, in which case 3hp is a bit small, but still maybe passable for lighter work. 5, or 7.5 would be better suited for actually pulling any chips. These lathes run relatively slow though, and at HSS speeds, you don't need a whole lot of power. Running them up near the higher speeds on reasonably sized work, you can still pull plenty of power on an older lathe. The belt may actually become the limit. Various references (maybe an old machinery's handbook) will have the power per inch of belt at a given speed. 3 phase is the only sort of motor I like. DC and Brushed AC sound like a miserable and/or noisy drive to be running for hours at a time. Treadmill motors all burn up when you ask considerable power for any length of time.

          Pictures help, but I'd try to keep the drive arrangement and speed control factory. It worked then, it works today. If you don't have a countershaft, then a drive-all box, Ford Model A transmission, etc, all work good, but are getting rarer and kind of expensive. Also a cone head belt lathe is more like 100 years old, minimum, unless it's a SB or Hendey.
          21" Royersford Excelsior CamelBack Drillpress Restoration
          1943 Sidney 16x54 Lathe Restoration

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          • #6
            Get a 3ph motor & VFD for it. You will never be sorry you did.
            Location: Saskatoon, Saskatchewan, Canada

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            • #7
              Biggest problem ...is motor inside lathe base or outside.. ?
              if outside you have dozens of options..

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              • #8
                Hopefully I've done this right and you'll see a pic.

                Obviously you guys are used to proper huge. I think this one is a mere toy by your standards.

                This exact machine (a Chekka) is not on Lathes .co.uk, so I'm not sure of the complete spec, but it's 10" diameter I believe, The chuck in the pic is a 10" according to the seller. The big brother of this one is on there and weighs 1.7 ton. I hope this one weighs considerably less!

                I do agree that a 3 phase and a VFD would be the ideal answer. Just not sure how many horses it'll need.

                Before splashing out I thought I'd investigate other options.
                You may only view thumbnails in this gallery. This gallery has 1 photos.
                Last edited by Jonesy; 02-06-2021, 07:27 PM.

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                • #9
                  Looks like a 14 inch lathe , with external motor. .. and looks like mostly complete.
                  has flat ways looks like.l

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                  • #10
                    Originally posted by Jonesy View Post
                    Hopefully I've done this right and you'll see a pic.

                    Obviously you guys are used to proper huge. I think this one is a mere toy by your standards.

                    This exact machine (a Chekka) is not on Lathes .co.uk, so I'm not sure of the complete spec, but it's 10" diameter I believe, The chuck in the pic is a 10" according to the seller. The big brother of this one is on there and weighs 1.7 ton. I hope this one weighs considerably less!

                    I do agree that a 3 phase and a VFD would be the ideal answer. Just not sure how many horses it'll need.

                    Before splashing out I thought I'd investigate other options.
                    I concur with 754. For it's time period it's probably 14 or 14.5" swing. And if my eyesight is good enough, I'm seeing flaking left of the saddle which would mean that this lathe has been properly re-done, or is in like-new condition. Either way, if it was well done you're in for a treat.

                    3HP is the answer for that machine.

                    I will probably disagree with most others here, but I think you should set it up exactly as it was intended. I would hang the countershaft on a ceiling or wall, and shift the belts the old fashioned way. It only takes a few seconds to roll a belt off one pulley and onto another. You'll get quick, and you get full power in every speed. Any electronic setup will lose HP when slowed down.

                    In addition, I'd even keep the tight loose pulley setup. Faster than a motor starting up, and can be done very gently, which has a number of distinct advantages. Granted, that's all more work than hanging a motor on the wall and running a belt and VFD. But it has some advantages and is period correct, if you care about that sort of thing.

                    If you want to see how time consuming it is to fool with belts, check out David Richards on YouTube. He has a 20" American and I think the belt changes are plenty quick. They certainly are on my belt drive drill-press.

                    -----------

                    754, they look like low angle and short Vee ways to me, but I believe they are Vee ways. I could be wrong.

                    21" Royersford Excelsior CamelBack Drillpress Restoration
                    1943 Sidney 16x54 Lathe Restoration

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                    • #11
                      3hp is not he answer if you intend use a vfd without belt changing. You are only going to get 3hp at 60hz or above. Below 60hz you are constant torque so HP is proportional to speed; above 60 to maybe 120, hp is constant but torque is inversely proportional to speed. Sure... you maybe don't "need" 3hp" so you can stretch the envelope, but...

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                      • #12
                        More modern lathes of that size that I've seen typically use motors in the 1-1/2 or 2 hp range, but especially since you've already got a 3 hp I'd go with that, it's certainly not what I call "oversized". 5HP and up I'd call "oversized".
                        "A machinist's (WHAP!) best friend (WHAP! WHAP!) is his hammer. (WHAP!)" - Fred Tanner, foreman, Lunenburg Foundry and Engineering machine shop, circa 1979

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                        • #13
                          I am a pro VFD guy for almost everything. However, If you have the room and are willing to mount the countershaft, you could use the 3Hp motor you have and have all of that 3Hp available in every speed. True variable speed is a nice side benefit of a VFD, but these machines worked thousands of hours with just belt change speed options. This might be an economical way to get it going.
                          Robin

                          Happily working on my second million Gave up on the first

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                          • #14
                            over powering if using a VFD is a good idea and 3hp isn't so large that a VFD is going to be super expensive. Depending on where you are, I'd hunt for a used 3P motor. They are cheap and saves you the work and having to find a new one for the bandsaw. If in working condition, about the only thing that can go wrong is bearings which are cheap and easy to replace
                            in Toronto Ontario - where are you?

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                            • #15
                              Thank you all for your input. It really is very appreciated.

                              Along with the actual lathe there are a number of large wooden boxes with plenty of extras. In the corners of some of the pics I can make out a steady or 2, and what looks like the handle of the tail stock. I'm taking a bit of a gamble as the listing was very vague, and if I asked too many questions there may have been more info added to the listing, and the price would (I think) have gone up considerably.

                              As it is I got it for a song and can't wait to go get it. Or should that be Get R Done!!

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