Boxford motor help

Hmm that was one of my concerns

cheers

So - time to give the full backstory

I have a wee workshop beside my garage which I use for woodwork - having a combined workshop in the garage wasn't good - wood don't like engine oil and engines don't like sawdust!

I have a 3 phase converter which i originally had running my wadkin bursgreen bandsaw and my Union Graduate lathe. Both ran great but I got a bit fed up changing the connection and settings on the converter every time I wanted to work the 'other' machine. One day a friend offered to add some weird gizmo -that I now know to be a VFD - to my woodlathe to allow it to be fed straight from the 240v supply. Ideal said I, after he told me about the variable speed etc.

However..... when roughing or turning larger dia wood blanks - specially out of balance blanks the woodlathe has to be run at fairly low RPM and it just doesn't have anywhere near the torque it had before the conversion and it kind of spoiled my experience to the point that I avoided woodturning for a good couple of years.

Spring forward to current times and I am looking to get a system that will work my Boxford in the way it's meant to be used.......

I was right on the point of ordering a 3 phase + VFD when Speedy made his point about the reliability of VFD's and the cost of replacement.

I'm happy to spend a wee bit more - looked at the website recommended earlier and its around £200 - £220 for the complete 3 phase system with VFD - if it will give me the best solution.

There does seem to be an argument for single phase from a cost point of view although as previously mentioned - I'm a bit clueless in this area and don't really know what else I need, do I just buy a motor (££?) and pop that in and it works or do I need other gubbins and have to rework switches etc?

I'm still leaning towards the 3 phase but want to make sure if I do go that route that I get a reliable VFD . I'm also really enjoying all these different points of view and appreciate all the advice folks are giving. I'm happy to take the time and listen to folks to make sure I opt for the best all round solution

thanks again

ewan

Hi Andrew

would a jump from 4 pole 3/4HP to 4 pole 1HP be enough to overcome the torque problem?

cheers

ewan

The 1 hp motor will always have more grunt at whatever speed, but hobby lathes are rarely taxed to the limit of motor power or torque.The beauty of the VFD is to give conveniently rapid speed control for the large majority of jobs. Don't forget that on the, probably, rare occasions that you do need lots of low-speed torque, the lathe pulley system and back -gear can always be used just as they would have been with the original, fixed speed motor.

As Clive says, the belt system and back gear still allows just as much power, with torque, for either motor type. The advantage is that a wider choice of speeds at the twist of a knob (or press of a button) comes with a VFD.

Adding a greatly more-powerful motor is folly, IMO. Any time that powerful motor is at full power, it will likely stress the machine - even worse if there is a ‘crash’.

Most machines will tolerate a power increase but 33% might be pushing it in the long run as there is always the temptation to overload the machine. I would expect a 3 phase motor to perform better than a single phase equivalent, anyway.

I increased the motor power on a gearbox machine by 20% (I found I could run a higher rated 415V motor at lower horsepower with a 240V VFD).  I am careful not to stress the gearbox by using extra ‘grunt’ as it is old and might be awkward/expensive to repair/replace if I ruined it.  The soft start of the VFD helps on that side of things, of course.

Edited By not done it yet on 24/06/2020 21:40:26

thanks to both Clive 1 and not done it yet for the comments - good common sense advice regarding not going overboard - the original motor was a 3 phase 3/4hp so a 25% increase to a 1hp used sensitively might be the way to go.

Having a VFD controlled motor is an addition to using pulleys and back gear, not a lazy persons substitute.

Evan I would say stay with a 4 pl 1500 motor .75 HP or even move up to a 1HP buy your inverter or a inverter /motor pack from reputable supplier who can give you advice and support if needed, and as NDIY pointed out if you need to go slow with torque put it into back gear. One of the advantages of fitting a VFD is that it gives you some speed adjustment for a given pulley combination. Look at it this way do you need to fit a DRO no does it make life easier yes same goes for a VFD

H

Edited By Harry Wilkes on 24/06/2020 22:03:48

Ewan, you raised the point earlier tonight about wiring and switches. If you use a VFD with a new 3 phase motor then you will have to connect the VFD directly to the motor. You will not be able to use any switches/wiring in the same manner that was used in the original 3 phase configuration. A VFD is not a plug compatible substitute for a 'real' 3 phase supply.

Thanks for this good advice Harry (& thanks to SM as well)

I think it's time to get on with this as I have a few wee jobs starting to build up and I'm looking forward to having some fun with this wee thing.

CB1 mentioned Inverter Drive Supermarket on an earlier post - based on your experience are there any other reputable suppliers out there I should be looking at?

Sorry, but 3/4 —-> 1 in my book is rather more than a 25% increase! As I commented above, a 1/3rd increase is likely to cause problems in the future.

I’m sure Boxford designed their lathe with a healthy safety factor - but that was when it was all new (and spares were readily available). OK to use some/all of that extra safety factor, if you wish to accept increased wear and repairs. I don’t particularly wish to overload my machines.

Back in the 60/70s we (my brother and I plus a few of our friends) used to drop larger engines in cars. Ours were Anglias/Cortinas/Escorts - but we always up-rated other components to reflect those increases in power. It was generally the clutch/gearbox/rear springs that failed (even with the standard engines), not the engine!. Brakes were always up-graded and appropriate rubber was fitted between car and road. Even illumination, suitable for much speedier night-driving, was installed.

These machines are not like computers, which can be up-graded with only cooling issues to be dealt with.

Hi NDIY - scuse my rushed maths - you're right it is more than a 25% increase - typing without engaging brain!

fair point about upgrade one part - consider the rest.

I've emailed Inverter Drive Supermarket and asked them to recommend a VFD/motor combo - any other reliable companys that folk would recommend trying?

cheers

Evan got all my VFD gear from Transwave, Taking NDIY comments about different controls on an inverter than on your lathe you can control the VFD from it front panel or you can purchase one already made up from your supplier.

can I also suggest if you unfamiliar with VFD's go take a look on youtube

H

Thanks Harry

My workshop converter is also a transwave that I bought almost 20 years ago and it's still going strong - they do good stuff but seem to be a bit more £££ than some of the others.

I'll have a wee youtube session and see if I can expand my VFD knowledge

Cheers

Ewan

Not sure what make the VFD is on my lathe. It came as part of the deal. (Free fitting if ordered at the same time as the lathe ) Unless the pendant is a generic one, it looks like a Newton Tesla?

The standard single phase 1470 rpm motor was a 2 hp. I asked for 1.5 hp three phase motor, since I thought that it would be an equivalent.

The VFD has been in use, not daily, but many times long enough for the cooling fan to cut in, and is still functioning after 16, nearly 17 years, so could be described as being reliable. The motor spends most of its time being run at maximum sped.

Howard

Not sure what make the VFD is on my lathe. It came as part of the deal. (Free fitting if ordered at the same time as the lathe ) Unless the pendant is a generic one, it looks like a Newton Tesla?

The standard single phase 1470 rpm motor was a 2 hp. I asked for 1.5 hp three phase motor, since I thought that it would be an equivalent.

The VFD has been in use, not daily, but many times long enough for the cooling fan to cut in, and is still functioning after 16, nearly 17 years, so could be described as being reliable. The motor spends most of its time being run at maximum sped.

Howard

Hi Howard

I'd say 16-17 years qualifies as reliable