Thread: Current breed of eBay VFD's for lathe upgrade

A 1.1km motor is likely to have a 19 mm shaft while a 1.5KW is likely to have a 24mm shaft
Before you bore out the pulley make sure you have enough meat left on the pulley for the keyway and grub screw.
I couldn't do this on my Woodfast pulley without risking making the pulley walls too thin so I turned up a new pulley.

Any of the cheap VFDs will be adequate to run a small WW lathe.

My woodfast cobra lathe was converted a few years ago with the same problem of 5/8 shaft and pulley size, I ended up purchasing a 3 phase .72 kw (1 hp) CMG motor (made in Aust) product code CW34075 that has a 5/8 shaft which fits the Woodfast pulleys. It is up to you what motor size you use but I have no problems turning products inboard or outboard with the current motor sizing . It is worth noting that my Vicmarc VL175 also has a 1hp motor,

Originally Posted by Oddy

I've had my starter lathe for a while now and am quite happy with it (an old Woodfast in perfect shape), but am considering a cheapish upgrade to variable speed. I plan to go with a 1.1 to 1.5 kW motor and only have 240V for input.

Will probably have to get my step pulley bored out to fit new motor shaft - current .75kW motor only has a 5/8 shaft, but otherwise the mounting configuration is going to make it very easy to replace the motor.

Anyone have any experience with the current crop of VFD's selling on eBay these days? Any decent ones out there among the cheapies?

Depending the capacity of your Woodfast. I would be looking at maybe 2.2kw if it will physically fit in the Woodfast. The reason for the increase in power is that as you lower the speed on VFD you will lose torque. One of the problems with Woodfast is the motor space is limited, but I would still go with the bigger motor option where possible
One way to counter this is to have a stepped pulley arrangement to increase the mechanical advantage. But on 1.1 or 1.5 you probably wont obtain enough mechanical advantage to over come the loss.
As to which one might be the better, look for those that have a guarantee, say 12 months and are sold by an agent etc here in Australia. At least you will some recourse if it goes pear shaped.

Thanks for the replies so far.
@hughie I don't think I would have problems with any practical size motor. My lathe is mounted on a custom steel stand with the motor mounted on a platform below the bed. The platform could take just about any motor you would want to throw at it. The lathe is an MC908 with a 42cm swing over bed and possibility of larger outboard turning, though at this stage I don't think I would attempt anything bigger than 40cm.
I just don't want to go overkill on the motor though. It seems new lathes of a similar size tend to have motors in the 1.1 to 1.5kW range.

Originally Posted by Oddy

Thanks for the replies so far.
@hughie I don't think I would have problems with any practical size motor. My lathe is mounted on a custom steel stand with the motor mounted on a platform below the bed. The platform could take just about any motor you would want to throw at it. The lathe is an MC908 with a 42cm swing over bed and possibility of larger outboard turning, though at this stage I don't think I would attempt anything bigger than 40cm.
I just don't want to go overkill on the motor though. It seems new lathes of a similar size tend to have motors in the 1.1 to 1.5kW range.

The new ones have a different variable speed set up that offers full torque through the speed range, hence the suggestion. I have rebuilt a couple of lathes with electronic variable speed drives one of which was a M400 Woodfast and the motor bay could only handle a 1.1kw.
overhaul is complete and tested


I am currently building another with the same set up but the drive will be external so as not have any hassles with space.

Why not contact Woodfast? I fitted one of their variable speed kits to my Woodfast lathe about 10 years ago. I have turned down a block of maple 500mm diameter and 250mm thick on the outboard until it fitted inboard down to a lace bobbin. I only have good words for their kit. Will add also the kit is not real cheap, but it is excellent quality.

Jim

Yeah, I did look into the kits - Woodfast and Vicmarc, but they are extremely expensive compared to the ebay vfd's + used motor, or even a new motor. The kits are even more expensive than buying the components separately e.g. decent quality new motor and same VFD.

Originally Posted by hughie

The new ones have a different variable speed set up that offers full torque through the speed range, hence the suggestion.

If you are referring to vector drive VFD? then while they do have improved torque across the speed range it is far from full torque.

Below are some test measurements for a nominal 1HP motor free running at 770 RPM @ 50Hz using a Non-vector (V/F) drive and a Vector drive.
The torque outputs for the vector drive are clearly superior to the non-vector drive but as you can see the torque is far from constant

Under load if the 1HP motor can maintain 770 rpm then it generates about 9.3 NM of torque.
The reason that some torques in the graph are greater than this is because most motors can generate more HP and torque than their specified rating.
It's not unusual for a 1HP to output 1.5HP and hence correspondingly higher torque

In practice the max torques generated by the vector drive are (over a limited low speed range ~5 to 25Hz) about the same as that for double the frequency of the non vector drive.
EG the torque generated by a motor running via vector drive at 10Hz is about the same as that generated by the non-vector drive at 20 Hz.

At very low frequencies (<5Hz)where the non-vector drive just dies, the vector drive will allow the motor to still generate some torque.

Above about 25Hz the Vector drive does allow the motor to develop the same torque as at 50Hz. Above 50 Hs they work the same as the non-vector drive.
So in practice the Vector drive enables the motor to have more or less constant torque from about 20 t0 50 Hz.


TorqueVRPM.jpg

BYW this was done directly on my Hercus MW lathe by clamping my De Prony Brake onto the bed of the lathe (using suitable padding of course) and mouting the brake drum in the chuck.

On terms of price the vector drives used to be double the price of the non-vector drives - at least that was the case hen I bought the VFD for my MW lathe in 2011.
Now I see there are some cheap brands that cost about 50% more but I haven't tested these to see if they are any good.

I picked up a Vacon (new old stock) on ebay which I am competely satisfied with.
I was a bit concerned about the safety aspects (electrical/fire) of some of the cheaper ones on ebay.

I wrote to Vacon overseas for some advice on programming the unit, and got a call the next day from their Australian office with all the information & diagrams I needed.
They were extremely helpful & I was very impressed with their service.

Originally Posted by nalmo

I picked up a Vacon (new old stock) on ebay which I am competely satisfied with.
I was a bit concerned about the safety aspects (electrical/fire) of some of the cheaper ones on ebay.

Of the 12 VFDs I have in my shed since 2011, 10 are cheapies and one of these died when I tried to force it to do something it's limited instruction set would not allow it to.

The cheaper ones are basically copies of the more expensive ones but with reduced instruction sets and programability.

While they use cheaper components, the standard safety mechanisms such as current limiting facilities are still available so they are still able to protect circuits and motors.

If the VFD had to be used in operator free environment that might be a good reason to invest in a more expensive unit, but or wood working, especially where the operator is present 100% of the time, 95% of the programability of the more expensive ones will never be utilised.

Bob yeah vector drives are the ones I was referring too.

HI ALL,
I have just converted my woodfast c 1000 from 1hp single ph to 1,5 hp three phase vdf am very happy with the result,Ample power at low rpm I have retained my 6 speed pulley 35 rpm at 20 htz on small pulley 4500rpm on 125 htz on5th section total cost of $800 dollars, john t

Originally Posted by John T

. . . total cost of $800 dollars, john t

$800 Sounds expensive.

A basic 2HP VFD suit able for a WW lathe can be obtained for $150 and a used 3P motor can be obtained for under $50.
$30 for a pot, remote switch and a plastic box to hold them.

Even a basic Vector drive VFD can be obtained for ~$250

Originally Posted by John T

HI ALL,
I have just converted my woodfast c 1000 from 1hp single ph to 1,5 hp three phase vdf am very happy with the result,Ample power at low rpm I have retained my 6 speed pulley 35 rpm at 20 htz on small pulley 4500rpm on 125 htz on5th section total cost of $800 dollars, john t

What VFD did you end up going with John?