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  1. #1
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    Default Drill Press motor size - help

    Gday All.
    My old Richardson DP had a 3 phase motor on it when I first got it back in the mid 1970's. At the time (not having 3 ph) we removed it and replaced it with a 2 speed, single phase washing machine motor which has done (and is still doing) sterling service. I have no idea what the power of this motor is and cant remember what the original 3 ph was. The current motor is more than likely only 1/4 hp or even less but I've never had an issue with it being too small.

    When I refurbished the old DP about 25 years ago (geez writing that makes me feel old) I replaced the original 3 step flat pulleys with 4 step V pulleys so ending up with 8 speeds. However the lowest speed is still around 400 rpm which is way too fast for larger hole saws or trepanning tools etc. When I converted it to 4 step pulleys I also got an extra pulley with the intention of one day making a compound drive for it. That hasn't happened and is not going to.

    Now though, with VFD's being so cheap, I'm leaning towards fitting a 3 phase motor and VFD to get the variable speed control.
    So can someone who has a decent DP (either Richardson, Brobo or Tough etc) be so kind as to have a look and tell me what size motor and speed is fitted please? I want to start looking for a 3 ph for my old DP.

    dp 004.jpg


    Thanks in advance.
    Peter

  2. #2
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    Default mottr 550watts

    Hi Peter
    my waldown drill press is 550 watts about 3/4 .
    I thought it was 1/2 hp. when i checked it said 550 watts
    aaron

  3. #3
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    Default

    I put a 1HP on my Tough when I did the VFD conversion, original was 3/4HP (I think??)

  4. #4
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    Default

    Thanks Gents.
    I was thinking 1hp so I'll keep my eyes out for one.
    peter

  5. #5
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    Default

    Boy could I do a deal for you.. I have a second motor same frame size as the one I used on my tough I might be willing to do a deal on. Not sure of the wattage though, I have it in my head I bought two different ones, but can’t remember. It’s in storage so I don’t have access to check until Monday. PM me if you’re interested and wish to discuss further.

  6. #6
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    Default

    Quote Originally Posted by racingtadpole View Post
    Boy could I do a deal for you.. I have a second motor same frame size as the one I used on my tough I might be willing to do a deal on. Not sure of the wattage though, I have it in my head I bought two different ones, but can’t remember. It’s in storage so I don’t have access to check until Monday. PM me if you’re interested and wish to discuss further.
    PM sent.
    peter

  7. #7
    BobL is offline Member: Blue and white apron brigade
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    Default

    Marked Watt rating on many motors may be input power rather than output. HP ratings tend to be output. When adding a VFD even vector drive VFDS have less power at <50Hz have less power so increasing the motor power is seriously worth considering. My DP originally had a 1HP motor on it but changed it to 1.5HP when I added. A VFD.

  8. #8
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    Quote Originally Posted by BobL View Post
    Marked Watt rating on many motors may be input power rather than output. HP ratings tend to be output. When adding a VFD even vector drive VFDS have less power at <50Hz have less power so increasing the motor power is seriously worth considering. My DP originally had a 1HP motor on it but changed it to 1.5HP when I added. A VFD.
    Bob.
    Thanks, hearing you. Pretty sure the motor I currently have wouldn't be any bigger than 1/2 hp (more than likely less) so a 1 hp should be fine.
    peter

  9. #9
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    Default

    Quote Originally Posted by bollie7 View Post
    Bob.
    Thanks, hearing you. Pretty sure the motor I currently have wouldn't be any bigger than 1/2 hp (more than likely less) so a 1 hp should be fine.
    peter
    You may still need a bigger motor when running slow with a big drill bit or trepanning tool Peter. The bigger tool needs more power but slowing from 400 rpm to say 50 rpm reduces power, — assuming 400 rpm is at 50Hz, 50 rpm will be around 6Hz, with I think 1/4 H.P. maximum.

  10. #10
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    Default Use the pulleys..

    Running a VFD much below 40Hz is an exercise in futility that if not careful will lead to burning the windings into oblivion. Best practise is to gear your motor for as close to lowest speed desired at 50Hz and use the frequency to ramp it up from there. Motors are more tolerant to running at higher frequency than lower. Attempting to run a 50Hz motor at 6Hz is not going to produce anything close to useable power, you’ll be able to stop the motor with a finger pressed against the chuck.

  11. #11
    BobL is offline Member: Blue and white apron brigade
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    Quote Originally Posted by racingtadpole View Post
    Running a VFD much below 40Hz is an exercise in futility that if not careful will lead to burning the windings into oblivion. Best practise is to gear your motor for as close to lowest speed desired at 50Hz and use the frequency to ramp it up from there. Motors are more tolerant to running at higher frequency than lower. Attempting to run a 50Hz motor at 6Hz is not going to produce anything close to useable power, you’ll be able to stop the motor with a finger pressed against the chuck.
    It depends on the quality and use of the motor ,and the type of VFD.
    A good quality motor running unloaded should be able to run indefinitely even as low as 15 Hz.

    For a machine like a DP most loaded use is relatively intermittent, more so than a lathe or mill where long loaded cuts are more common.
    I run regularly run the Leeson motor on my DP with Vector drive VFD as low as 15Hz under load ie large bits, for a few holes and yes it does warm up, it's nowhere near overheating.
    As soon as the holes are completed I sometimes increase the frequency to 50Hz to cool off the motor and only change the belts if I need to drill lots of big holes or drop down to really low revs.
    On my WW lathe I also operate under load as low as 12 Hz for a few minutes without heating problems.

    Non-vector drives enable most motors to produce about half power at 25 Hz.
    My testing shows a Vector drive will produce half power as low as about 15Hz.
    If the original motor was 0.5HP and that is doubled to 1HP, then under a vector drive it could still produce 1/2HP at 15Hz.
    This is worth the effort.

    If one was worried about over heating a computer fan could always be added to add extra cooling.

  12. #12
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    Default

    Quote Originally Posted by racingtadpole View Post
    Running a VFD much below 40Hz is an exercise in futility that if not careful will lead to burning the windings into oblivion. Best practise is to gear your motor for as close to lowest speed desired at 50Hz and use the frequency to ramp it up from there. Motors are more tolerant to running at higher frequency than lower. Attempting to run a 50Hz motor at 6Hz is not going to produce anything close to useable power, you’ll be able to stop the motor with a finger pressed against the chuck.
    I agree that you need to be careful when running a motor at less than 50Hz, but you will get usable power at much less than 40Hz if you use a good vector drive, and you would need strong fingers against the chuck to stop it I understand, when using a properly set up vector drive and a 1.5Kw 3~motor.
    BobL has said it all before I could respond, and with much more authority too, I didn't realise that you could still have full power at low rpms with a vector drive and just looking at a Google reference, on closed loop some drives even work to well below 1HZ, but at such low frequencies another cooling system is needed.
    Last edited by Ropetangler; 9th Feb 2020 at 12:10 AM. Reason: BobL said it sooner and better.

  13. #13
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    Default

    A vector drive is a different animal to a regular variable freq drive, so it’s kind of an apples/oranges thing. Vector drive has torque compensation of sorts, a regular VFD doesn’t.
    I get the theoretical arguments around it all but let’s look at practical, how many home workshop VFD conversions are closed loop? How many have independent cooling? Reality is if you try and run a drill press size motor off a HY drive at ridiculously low frequencies, you’re either going to be disappointed or let the smoke out or both..

  14. #14
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    Quote Originally Posted by racingtadpole View Post
    Running a VFD much below 40Hz is an exercise in futility that if not careful will lead to burning the windings into oblivion. Best practise is to gear your motor for as close to lowest speed desired at 50Hz and use the frequency to ramp it up from there. Motors are more tolerant to running at higher frequency than lower. Attempting to run a 50Hz motor at 6Hz is not going to produce anything close to useable power, you’ll be able to stop the motor with a finger pressed against the chuck.
    Yeah, now that I'm not as tired as I was last night, I've been doing some sums and I think I might have to bite the bullet and set up a compound drive on the DP after all.
    My current 2 speed motor does approx 990 rpm, on low and approx 1490 on high (according to the hand held optical tacho I have - who knows how accurate that is) so if I fit a 1400 rpm (or thereabouts) 3 phase then I'm going to need the compound drive to get the final speed down without trying to run the motor at too low a frequency.
    I might have to convert it to take A section belts rather than the M section I'm currently using.
    Why am I using M section will be the next question. Well, when I did the conversion I was working in the F&M section at a TAFE college and the students had to make a 4 step cast iron M section pulley as an exercise. Once they were marked, if the student didnt want it (and most of them didnt) the pulley went in the bin. As I had a young family and not much money at the time, 2 of these pulleys found their way onto my DP.
    Back then we didnt have the cheap stuff from china that we have now and a 4 or 5 step, A section pulley was quite expensive.

    This will be a longer term project as I've got by all these years with it the way it is atm. My main reason for thinking about a VFD is so I dont have to change the belt for speed changes all the time.

    peter

  15. #15
    BobL is offline Member: Blue and white apron brigade
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    Quote Originally Posted by racingtadpole View Post
    A vector drive is a different animal to a regular variable freq drive, so it’s kind of an apples/oranges thing. Vector drive has torque compensation of sorts, a regular VFD doesn’t.
    I get the theoretical arguments around it all but let’s look at practical, how many home workshop VFD conversions are closed loop? How many have independent cooling? Reality is if you try and run a drill press size motor off a HY drive at ridiculously low frequencies, you’re either going to be disappointed or let the smoke out or both..

    Closed loop is not needed to get the benefit of Vector control.
    Nearly all need VFDs (including HY's) these days come with sensorless vector control as standard.

    Below is some practical info which shows the comparative (vector/non-vector) performance curves I generated in 2015 for a 10 year old, 2HP SAJ sensorless Vector Drive VFD I had on my lathe.

    The blue line shows how about same torque is generated at ~ 10 Hz in vector drive mode as at ~24 Hz in non-vector mode.
    Even 4Hz the torque from vector mode was almost the same as what could be obtained ta 17Hz in non vector mode.
    Running at 4Hz under load without added cooling is indeed foolish but there's no doubt that one can run at 12Hz, I've been doing this on my DP for about 8 years.

    Setting up the senseless vector parameters can be a PITA but its not beyond the scope of a keen DIYer.


    VectorsdriveVF.jpg

    Ove the last 10 years Ive had about 20 different VFDs through my workshop over and whether by design or accident have at times hammered them pretty hard. During that time I've had one "accident" whereby I damaged a used VFD beyond repair by repeatedly asking it to decelerate a load that was too high for its electronic and programming limitations. I treated that as a learning experience. All of the other VFDs (including those I have moved on) are still running as far as I know.

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