Motor choice for Wadkin AGS10 restoration

[Goldfinger234]

To the OP. There’s a few things to consider. I work in commercial BMS controls and have long since lost count of the number of motors and VFD’s I’ve fitted and replaced.

If you change to single phase, your inrush current when starting the saw will greatly increase. Mine (3HP table saw) needs a C20 breaker to ensure it doesn’t trip off when starting with a dado set, and you’ll need to wire it via a 16A trailing socket as it’ll blow a 13A fuse every time, even with a normal blade.

The saw was more than likely originally fitted with an imperial motor, in which case you’d need an imperial motor to replace, otherwise the pulley won’t fit the shaft, and the bolting mount will be different. Hacking the mount to bits can be easier said than done, depending on available space and size of mount. Far easier to just but the right motor. Pulleys aren’t expensive though.

The VFD option would be best to eliminate inrush current on a domestic supply, just try and avoid the cheap tat otherwise you’ll be replacing it so often you’d wish you’d just bought a good one to begin with.

The other option is just to downgrade it to 2HP with a new pulley same size as the old. It may change the size of the belts slightly, but there’s loads of online pulley calculators to sort that out. Unless you’re using it commercially, you’ll never need a 3HP motor anyway. It’s one of the big myths of woodturning, so many people want bigger and bigger motors, when oversizing them does your electricity bills no good as induction motors are quite inefficient when used well within their capabilities. You’re better with a correctly sized motor than an oversized one.

 

[Myfordman]

This may also help

View attachment 155161

1 = 400 volts

I think you might want to check that graph for accuracy?

 

[Goldfinger234]

And I would very strongly suggest you don’t wind an induction motor up to 70/80Hz unless it’s specifically designed for such. Most are 50Hz UK with 60 maximum. Most standard induction motors are good for +20% speed increase above stated spec (IEC regs), but that all depends on the load being applied via the saw, the quality of the windings (People’s Republic tat etc.,) the max output of the VFD and as always the ability of the bearings to withstand the speed and load. You’re better off speaking to the motor manufacturer than other woodworkers.

 

[Megaweasel]

@Goldfinger234 - cheers for that, the inrush current is one thing (along with breaking) that I was thinking about. However, For the moment I've ordered a 2hp single phase - its advertised as a new motor (surplus to requirements) and got it for 50 quid, so its good enough to test the saw with. My current machine is a ten inch (250mm) and uses a 2hp motor and I've never had an issue with it so it should be fine. I'm intrigued enough by the vfd thing to be thinking about my drill press though where it will make much more sense.

Also, delighted to find the right Wadkin Bursgreen nameplate available today for not much, so things are looking up!

Chris

 

[Matt@Nearfield]

No offence intended and I hate to take the thread off track but what the hello are you cutting that you need the saw wound up that much?

Pete

Oh, shouldn't have posted really.. it was early this morning whilst I was still dozy. Tip speed.. now theres a whole new conversation. But generally, if the blade is rated for it ( v. Important) the faster its spinning the less of a bit it will take as you you delivery the work piece to it. This. FOR ME. seems to give a better quality of cut, with longer blade life as each tooth is taking a smaller cut and filling with less sawdust so heating up less.

BUT.. I also remove blade guards and use my fingers when I should use a push stick so really ignore me.

 

[Matt@Nearfield]

And I would very strongly suggest you don’t wind an induction motor up to 70/80Hz unless it’s specifically designed for such. Most are 50Hz UK with 60 maximum. Most standard induction motors are good for +20% speed increase above stated spec (IEC regs), but that all depends on the load being applied via the saw, the quality of the windings (People’s Republic tat etc.,) the max output of the VFD and as always the ability of the bearings to withstand the speed and load. You’re better off speaking to the motor manufacturer than other woodworkers.

Agreed. I should have kept my mouth shut. I've confused matters.

 

[Goldfinger234]

ww

My

Presumably your drill press has pulleys at present?

Even with a VFD you still have to use the pulleys, depending which speed range you want to work in. That’s why variable speed lathes generally have 3 pulley settings. You can’t leave the pulleys set to high speed and then turn your speed pot down to say 300rpm because the motor will hardly be turning over, won’t be putting out much power, and when you run motors in that manner it causes them to overheat, melting the insulation on the windings, as one of the moderators mentioned in an earlier post.

VFD’s aren’t the answer to everything. I suspect with a pillar drill you’d be better off staying as you are, or if you had a 3 phase one, getting a suitably sized Transwave Converter or something similar to give you a 3 phase supply, and use the pulleys themselves as normal, which to a greater or lesser extent you’ll have to do anyway.

With variable speed, you still want the motor running at or reasonably near its full load current, not being laboured in the same way a car would be doing 20mph in 6th gear. To reduce speed, the pulleys act as reduction gearing. This only changes with things like supply and extract fans, where as you reduce the speed, you also reduce the load, as they are moving less air. With a drill, you may slow it down, but you’re still trying to drill a hole, so the load can be the same if not more, but the power output of the motor is far less, so it struggles and overheats, if not stalls.

 

[Spectric]

I think you might want to check that graph for accuracy?

Wrong one inserted, not sure what project that came from except it was an old SMPS drive for mobile applications.

 

[Megaweasel]

ww


Presumably your drill press has pulleys at present?

Even with a VFD you still have to use the pulleys, depending which speed range you want to work in. That’s why variable speed lathes generally have 3 pulley settings. You can’t leave the pulleys set to high speed and then turn your speed pot down to say 300rpm because the motor will hardly be turning over, won’t be putting out much power, and when you run motors in that manner it causes them to overheat, melting the insulation on the windings, as one of the moderators mentioned in an earlier post.

VFD’s aren’t the answer to everything. I suspect with a pillar drill you’d be better off staying as you are, or if you had a 3 phase one, getting a suitably sized Transwave Converter or something similar to give you a 3 phase supply, and use the pulleys themselves as normal, which to a greater or lesser extent you’ll have to do anyway.

With variable speed, you still want the motor running at or reasonably near its full load current, not being laboured in the same way a car would be doing 20mph in 6th gear. To reduce speed, the pulleys act as reduction gearing. This only changes with things like supply and extract fans, where as you reduce the speed, you also reduce the load, as they are moving less air. With a drill, you may slow it down, but you’re still trying to drill a hole, so the load can be the same if not more, but the power output of the motor is far less, so it struggles and overheats, if not stalls.

Makes sense - Only speculation on my part at this stage - but if I still need to adjust the pulleys it really wouldn't be worth the added expense of a 3p motor and VFD to vary the speed. More research required on that one I think.
If you buy a new pillar drill with variable speed, how do they manage the issues you mentioned? Sounds like not with a VFD - DC motor?

 

[Spectric]

Stop and think, it is too easy to chase after some objective without fully understanding that objective and wasting time and money in getting there.

Question why you think you need to need a variable speed pillar drill and look at what it is you are doing and for me I don't change the speed very often because on the middle pulleys it covers my needs. If on the odd occasion when I use a large morse taper drill then I will drop the speed but most of the time it is not altered.

 

[Megaweasel]

@Spectric - wasn't a big deep thought - just from the discussion on VFD for my table saw (the original question) It sounded like using a VFD and 3phase motor on my pillar drill would avoid me changing speeds via pulleys - something I do find I need to do quite often. Was only some idle musings and its great to learn new things.

 

[Goldfinger234]

Makes sense - Only speculation on my part at this stage - but if I still need to adjust the pulleys it really wouldn't be worth the added expense of a 3p motor and VFD to vary the speed. More research required on that one I think.
If you buy a new pillar drill with variable speed, how do they manage the issues you mentioned? Sounds like not with a VFD - DC motor?

You’d have to be specific about the drill you were looking at.

 

[Goldfinger234]

You’d have to be specific about the drill you were looking at.

Put it this way, you’d need more money than sense to go chasing after variable speed pillar drills without very good reason. Far better off getting a used Fobco and tidying it up. Give you a lifetime of use then the same for whoever gets it after you, long after the variable speed trash has failed.

 

[Fergie 307]

Indeed. Personally I would stick with a single phase for simplicity. Just make sure it runs at an appropriate speed for the size blade, and pulley sizes you have. Regarding fitting a modern replacement motor, I find that the modern motors tend to be significantly smaller than the oldies. This means there is often room to fit an adapter plate between the motor and its original bracket, without altering the relationship of the shaft to the machine. This can often make it fairly straightforward. As to the pulley, if the original bore is imperial then the easiest approach is to see if you can get a metric shaft a little larger. Then you can just machine out the bore of the original pulley to fit, so 3/4 up to 20mm for instance.

 

[Goldfinger234]

Indeed. Personally I would stick with a single phase for simplicity. Just make sure it runs at an appropriate speed for the size blade, and pulley sizes you have. Regarding fitting a modern replacement motor, I find that the modern motors tend to be significantly smaller than the oldies. This means there is often room to fit an adapter plate between the motor and its original bracket, without altering the relationship of the shaft to the machine. This can often make it fairly straightforward. As to the pulley, if the original bore is imperial then the easiest approach is to see if you can get a metric shaft a little larger. Then you can just machine out the bore of the original pulley to fit, so 3/4 up to 20mm for instance.

The OP has obtained a 2HP motor, so on the proviso it’s metric, that’s a 90L frame size with a 24mm shaft. There’s no exact correlation with 24mm to imperial so it’ll either be new pulley or himself doing a bit of machining, and I suspect a new pulley and taper insert will be vastly cheaper than paying for someone to bore it out and mill a keyway.

He’d have been better off just getting a 2HP single phase imperial motor, then it would have been a straight swap, minus 2 phases plus a neutral, same frame size, same everything, so long as he got the correct foot mount. As it is, nothing will quite fit and it’ll need some hacking around. I once had to do the same on an AGS. Imperial is the way to go. They are a good fence setup at least.

 

[Spectric]

For a table saw there is no benefit in having a variable speed, all you need is the optimum speed and so just fitting a replacement single phase motor is the most cost effective solution as @Goldfinger234 has said. Bear in mind you also need the correct number of poles to get the correct speed.

 

[Goldfinger234]

For a table saw there is no benefit in having a variable speed, all you need is the optimum speed and so just fitting a replacement single phase motor is the most cost effective solution as @Goldfinger234 has said. Bear in mind you also need the correct number of poles to get the correct speed.

Correct.

Most table saw motors are 2 pole, or c.2800rpm. If the data badge shows 1350-1400rpm that is 4 pole. Most planer motors are also 2 pole, certainly the older ones (Wadkin etc..)

That is the cause of the inrush current. Press the green button and the saw instantly tries to run at 2800rpm, you cannot have a soft start on a single phase induction motor, only 3 phase. Modern electronically commutated motors used in HVAC appliances aren’t fitted to woodwork machinery, and where they are, you won’t get anything like the lifespan you would from a standard motor. EC motors can be speed controlled at single phase, but they are effectively a DC motor that incorporates circuitry transforming the 230vac input to DC, hence the far shorter lifespan. It’s rarely the motor that fails, always the electronics.

 

[Fergie 307]

The OP has obtained a 2HP motor, so on the proviso it’s metric, that’s a 90L frame size with a 24mm shaft. There’s no exact correlation with 24mm to imperial so it’ll either be new pulley or himself doing a bit of machining, and I suspect a new pulley and taper insert will be vastly cheaper than paying for someone to bore it out and mill a keyway.

He’d have been better off just getting a 2HP single phase imperial motor, then it would have been a straight swap, minus 2 phases plus a neutral, same frame size, same everything, so long as he got the correct foot mount. As it is, nothing will quite fit and it’ll need some hacking around. I once had to do the same on an AGS. Imperial is the way to go. They are a good fence setup at least.

Oh I agree, but was basing my comments on him having already got the, presumably metric, motor. On my lathe the modern replacement 3hp metric motor was a lot smaller than the original 1960's 1.5 Brook Compton that was on it. It was a doddle to make up a mount. I was lucky enough that I have another lathe, so modifying the pulley was simple. If you don't have the means to do it yourself, or a mate who can do it for you, then a replacement is probably the way to go, and of course you might need to alter the size of the pulley anyway, if your replacement motor isn't the same speed as the original. I can certainly see the attraction from the OP's point of view in using his £50 motor though, all depends how easy it is to fit it. Might be easy, might be a real PITA.

 

[Goldfinger234]

Oh I agree, but was basing my comments on him having already got the, presumably metric, motor. On my lathe the modern replacement 3hp metric motor was a lot smaller than the original 1960's 1.5 Brook Compton that was on it. It was a doddle to make up a mount. I was lucky enough that I have another lathe, so modifying the pulley was simple. If you don't have the means to do it yourself, or a mate who can do it for you, then a replacement is probably the way to go, and of course you might need to alter the size of the pulley anyway, if your replacement motor isn't the same speed as the original. I can certainly see the attraction from the OP's point of view in using his £50 motor though, all depends how easy it is to fit it. Might be easy, might be a real PITA.

I presume you’re talking about an RS or something similar. They were 6 pole 900rpm motors originally and a very big lump of a thing. Hopefully changing the mount on the saw won’t be too bad, it won’t have had a motor like yours to begin with. I can’t remember exactly what mine was like internally, it was nearly 20 years ago, the belts on saws are usually short, therefore if the OP has got a 4 pole motor by accident he could be screwed to start with, as you’ll need a bigger pulley on the driven shaft to give you the same speed at the arbor as the saw was designed for. I hope he’s got the right one. This is where the minefield can start with these machines if you’re not very clued up on motors etc..

 

[Matt@Nearfield]

To get back on track if this chap does choose to go down the vfd route then IN MY OPINION it's worth checking Clough42 YouTube Playlist on the TECO LS510 unit. It may help.


Be happy.

M.