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Forum topic by GeraldH posted 11-15-2014 02:25 PM 1299 views 0 times favorited 24 replies Add to Favorites Watch
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GeraldH

37 posts in 770 days


11-15-2014 02:25 PM

Topic tags/keywords: lathe bowl turning bowl lathe

Hello fellas. I am going to attempt to make my own bowl turning lathe. I just can’t see paying 2-3k for one and I think I can make one that will work as well or better than one I could buy (for my purposes). I have the general design down pretty well but I am not sure about the variable speed function. I would really rather use a variable speed motor instead of pulleys to achieve the different speeds. I am not sure about how to go about the electronics of making this happen. I would really like to have a knob of some kind that I could turn “up” or “down” to adjust the speed as well as reverse the motor with the same speed control ability. I have seen some “plug and play” type controls for that purpose but I am not sure how to use them with the reverse switch. I guess you would just put the switch before the speed control in the power sequence?

If anyone has any advice on “features” or “design ideas”, PLEASE SHARE with me. Also, if anyone has any “what not to do” advice, that is also welcome.

BTW, I received my new PM2000 Thursday! :) Boy that thing is SWEET! I haven’t had a chance to finish the set up though. I will put a review on here once I have used it for a while. Thanks Guys and Gals.

-- Gerald in B-ham


24 replies so far

View Julian's profile

Julian

1037 posts in 2156 days


#1 posted 11-15-2014 04:40 PM

I think you can control the speed of the motor with a VFD (variable frequency drive). Many of the major brand, large lathes are set up this way. Don’t know enough of the details but a good electrician could problem explain it.
Or perhaps check out a lathe that has a VFD and see what type of motor and VFD it uses.

-- Julian

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Wildwood

1886 posts in 1600 days


#2 posted 11-15-2014 08:02 PM

Much easier to take an existing lathe and convert it to EVS (electronic variable speed) than build a lathe from scratch. You will still need to make belt changes from low to high range in most instances. Having a 220V power supply will make the job a lot simpler. Expect to pay anywhere from $400 to $600+ for motor, converter & control box. Sometimes amounts included upgrading shop electrical circut to 220V and sometimes folks did it themselves.

http://www.youtube.com/watch?v=ZFVuJ0hwNnw&feature=plcp

http://www.ipenz.org.nz/ipenz/forms/pdfs/TreNz5.pdf

Back when Nova 3000 routinely converted to EVS, lot of folks bought their stuff at an electrical surplus store. Cost for a new Nova 3000 lathe, and conversion equipment might run between $1,000 to $1500 depending upon where they got the stuff.

Have seen several old iron Delta & brand name lathes converted to EVS during the restoration process. Sadly do not have those skills!

Good luck with it!

-- Bill

View GeraldH's profile

GeraldH

37 posts in 770 days


#3 posted 11-15-2014 08:11 PM

I thought about using an existing lathe to make it out of. I can get a 3hp motor and vdf control for $1000.00. The rest of the lathe is not that complicated really. Its just a bunch of square tube, plate, and angle steel. I have a pretty good design I think :). I have a friend with a machine shop who is going to help me out. He can make a shaft and do the major welding. I’m just going to use pillow blocks to support the spindle shaft. I will also have some outriggers to bolt down to the slab in my shop. With enough power and no vibration, I should be able to turn as large of a bowl as I want to. I have a tool rest built into the lathe but I will also make a “stand alone” one from a large fan base that my father in law got from his plant. It should work well. (think very large and heavy “lamp stand” type set up.

-- Gerald in B-ham

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Wildwood

1886 posts in 1600 days


#4 posted 11-15-2014 11:57 PM

Sounds like a plan go for it!

-- Bill

View REO's profile

REO

889 posts in 1539 days


#5 posted 11-16-2014 12:39 AM

2 hp will most likely be plenty. Vfds are cheap and can be used on 115 or 220 for 2 hp or less. slow speeds will require a powered fan to cool the motor because the TEFC fan wont be turning fast enough to provide enough air flow for the heat build up in the motor. a couple belt change speed ranges are better and properly planned will seldom need changing for the same turning. The directions that come with the VFD are pretty good and if you have additional questions just ask!

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GeraldH

37 posts in 770 days


#6 posted 11-16-2014 12:45 AM

Nothing I’ve read from where I plan to buy the motor and VFD from has mentioned an additional fan being required. How should that be done? Is it an external fan that is only on when turning at slow speeds? How would that need to be set up?

BTW- I will be using 230V power. I want to go ahead and get a 3hp just so I won’t say later “I wish had just a little more power”. It isn’t much more for a 3hp than a 2hp.

-- Gerald in B-ham

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Nubsnstubs

826 posts in 1195 days


#7 posted 11-16-2014 01:43 AM

Paying that amount for a motor and VFD is way too much. Even going with a brand new Baldor motor and VFD should be in the range of $700. If you do find a 3 hp motor, make sure it’s a 3 phase motor. Get over to an Electric Motor repair place, and see what they can do for you.
If you do it yourself, find an Electrical engineer to help you program forward/reverse, ramp speeds, and braking speeds. Mine was factory set for 10 second coast down speed after the stop button was pushed. It took another 10 seconds to reach speed. Now, with the help from a club member EE, I have a remote on a 10 foot cord. At my suggestion, the VFD was programmed to ramp up to speed in 4 seconds and 4 seconds to stop and has f/w…............. Jerry (in Tucson)

-- Jerry (in Tucson)

View GeraldH's profile

GeraldH

37 posts in 770 days


#8 posted 11-16-2014 02:12 AM

I have since sound a motor with a “matched” vfd for about $575.00. I have no idea about the programming though.

-- Gerald in B-ham

View REO's profile

REO

889 posts in 1539 days


#9 posted 11-16-2014 02:49 AM

The Vfd will come with instructions and they are not hard to follow. With a real world motor not a blown out of proportion motor you will find that 2 hp is plenty and they are easy to find. 3 hp is kind of an odd duck. I have done turnings 2 feet in diameter with power to spare with only 1 1/2 hp. you may find 5 hp motors easier than 3 hp and cheaper too! check with the appliance recyclers and get the blower motor out of a rooftop air unit. offer them fifty bucks and see what they say. I have gotten several for 25 dollars and less.

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GeraldH

37 posts in 770 days


#10 posted 11-16-2014 02:59 AM

I haven’t had any trouble finding a 3hp. The one I planed on buying is around $250 I think, and the vfd they pared the motor with is about the same. I’m building this thing to be able to turn unbalanced loads that are pretty large so I’m a little iffy about going with a 2hp. It seems like the 3hp is a “cut-off” for many of the vfd units I’ve looked at so I thought the 3hp was a good choice. What’s the deal with the fan for low speeds? Are you sure that’s needed and if so, how would it be set up?

-- Gerald in B-ham

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REO

889 posts in 1539 days


#11 posted 11-16-2014 03:36 AM

the motor is an electric heater. the harder it works the more heat it generates. running a motor slow with a VFD takes more power than when the motor is at syncronous speed. AC motors are syncronous. depending on the number of poles the rpm will be a multiple of 60(the hz of the ac line) 1800 and 3600 would be a no load syncronous speed but the nameplate RPM is based on electromagnetic slip at the rated HP thus 1725,1750 or 3450 and 1800. Hp is a rating of moving a fixed load a certain distance in a certain amount of time. A 1725 1 hp motor will have a higher torque rating(carry a bigger load) but a 3450 1 hp motor makes more trips with lighter loads (faster RPM) They will still finish the job at the same time using the same amount of energy (creating the same amount of heat) the fan on the end of the motor takes the heat away. If it runs too slow the fan doesn’t work well enough to remove the heat and it stays with the motor. The directions that you get with the VFD will talk about minimum and maximum operating speeds. and it will mention that operating the motor at slow speeds will affect cooling. Torque requirements increase as the rpm slows down as well. your best bet is to read the information that comes with the VFd. Get a good muffin fan and mount it over the end of the motor and set it up to turn on when you power up the main control and let the fan run after the VFD is in the stop mode before total power down.

View GeraldH's profile

GeraldH

37 posts in 770 days


#12 posted 11-16-2014 03:55 AM

Is there a relatively easy way to make the fan come on when running at low speeds? If a “muffin fan” (I’m not familiar with that) won’t be an issue as far as “constantly running”, I would just assume the fan kick on every time I turn the lathe on. I have a good understanding of heat and a decent understanding of electrical motors. Maybe you have an idea of how to “set up” the fan?

-- Gerald in B-ham

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MNclone

187 posts in 1049 days


#13 posted 11-16-2014 04:05 AM

The fan is attached to the back end if the motor. It spins at the exact same speed as the motor.

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GeraldH

37 posts in 770 days


#14 posted 11-16-2014 04:12 AM

Perhaps I’m confused, I thought we were talking about an additional fan, to help cool the motor when the “motor fan” is turning at low speeds for an extended period of time???

-- Gerald in B-ham

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GeraldH

37 posts in 770 days


#15 posted 11-16-2014 04:21 AM

I’m starting to reconsider this idea. I also looked at the robust lathes and that was a terrible idea.

-- Gerald in B-ham

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