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1940s Unisaw question

by Luthierman
posted 08-26-2016 12:14 AM


21 replies so far

View MrUnix's profile

MrUnix

7357 posts in 2557 days


#1 posted 08-26-2016 01:48 AM

There are specific motors depending on tilt, left or right. Mounts are different for each. But you are mistaken about using a VFD… three phase motors are more efficient than single phase ones, and running a VFD will make it even more efficient – and give you a ton of extra benefits that you could never get with a single phase motor.

Also, you will most likely have to cut the cabinet opening for a newer motor to fit unless you replace it with a similar bullet R/I motor.

Cheers,
Brad

-- Brad in FL - In Dog I trust... everything else is questionable

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Luthierman

222 posts in 1446 days


#2 posted 08-26-2016 01:56 AM

Thanks for the reply. SO what I am finding most interesting is that when I do a search for replacement motors, nearly none of them specify whether they are for right or left tilt. It must be based on part numbers. Well, truly I am spinning my wheels until I have this in my hands, which in reality will be in less than 24 hours.

Are you knowledgeable on compatibility with older saws vs new motors? Meaning specific brackets for specific years and whatnot.

It would be cool to find an original motor that is a single phase. That would be the bees knees. I don’t want to have to cut the cabinet even though it is already missing the cover.

Also, say I decide to get a VFD, for the sake of originality, any suggestions as to what would work? This would be the only machine running on 3 phase.

Just a fun fact, This saw came from the Purdue university cabinet makers shop.

-- Jesse, West Lafayette, Indiana

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MrUnix

7357 posts in 2557 days


#3 posted 08-26-2016 02:04 AM

If you ignore the cabinet opening size requirement, any right tilt motor will fit in any right tilt Unisaw. And any left tilt motor will fit in any left tilt Unisaw. You can find OEM bullet motors over at OWWM in the buy/sell area. I personally would get a VFD and keep the three phase motor – less money and more benefits. YMMV.

Cheers,
Brad

-- Brad in FL - In Dog I trust... everything else is questionable

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Luthierman

222 posts in 1446 days


#4 posted 08-26-2016 02:13 AM

Thanks, Brad. I’m starting to realize and agree with what you are preaching the further I go down this hole. Perhaps I will just recondition the motor and save some pennies with a VFD. Waaaay cheaper option. I was thinking a VFD was similar to a rotary converter. Boy was I wrong. A VFD is friggin brilliant way to run 3 phase, damn near anywheres.

-- Jesse, West Lafayette, Indiana

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MrUnix

7357 posts in 2557 days


#5 posted 08-26-2016 02:29 AM

For a little bit more incentive… if you swap out the motor, you will also have to change the heaters (overload protection) in the starter and modify it’s wiring to use single phase. The wiring isn’t hard, but finding the appropriate heaters may prove a bit difficult and add more cost.

If you stay three phase and use a VFD, the VFD provides the overload protection – so you can rip the starter off the machine and sell it to recover some (or maybe even all) of what you spend on the VFD. It also makes wiring much, much easier, and gives you the ability to do other stuff like add an emergency stop switch in addition to just the normal three wire control station (start/stop). The hardest thing about using a VFD is figuring out where to mount it.

Cheers,
Brad

-- Brad in FL - In Dog I trust... everything else is questionable

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Luthierman

222 posts in 1446 days


#6 posted 08-26-2016 02:37 AM

Do you have any suggestions on a VFD? I’m not certain of the hp of the motor but will know tomorrow. Looking mostly for a good reliable maker of the VFD.

-- Jesse, West Lafayette, Indiana

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MrUnix

7357 posts in 2557 days


#7 posted 08-26-2016 02:48 AM

The most popular is the TECO (westinghouse) FM50, which is a V/Hz type drive. However, with the advances in circuitry, sensorless vector drives, which used to be much more expensive, are now virtually the same price. It can be argued that a sensorless vector drive is overkill on a table saw, but given the now minimal price difference, it is an attractive alternative that will give you a few extra benefits over a plain V/Hz drive. The newer TECO L510 series of drives can do both (V/Hz or sensorless), and are only about $20 more than the FM50’s.

Also, ignore HP ratings… size based on amperage and keep in mind that they can do 150% of rated current for short periods. Also, those motors rarely, if ever, see full FLA current – so you can easily run a 5hp motor on a VFD that is rated as ‘3hp’. The slow start function of the VFD also eliminates the ‘inrush’ current when turned on. There are plenty of 5hp Delta 12/14 owners over at OWWM who are happily running on those ‘3hp’ FM50’s. My 3hp Unisaw just purrs right along running with a ‘2hp’ branded one.

Cheers,
Brad

-- Brad in FL - In Dog I trust... everything else is questionable

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01ntrain

259 posts in 1429 days


#8 posted 08-26-2016 03:47 AM

Just in case it hasn’t been mentioned….EBay is your friend when trying to locate the VFD.

View ErichK's profile

ErichK

80 posts in 1022 days


#9 posted 08-26-2016 05:18 PM

I found a VFD on Ebay for <$200 from this seller: http://www.ebay.com/itm/251296138141?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT and have been really happy with it. It is a very popular one in the home-CNC metalworking world.

Note that this link is for a 5 HP one (I have a 3 HP 3 Phase PM66), but it is usually considered smart to buy one a little bigger than you need (though that might be old advice!).

Definitely better than spending ~$600 to buy a new 1 phase motor!

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Luthierman

222 posts in 1446 days


#10 posted 08-27-2016 06:03 PM

I went and picked up the saw last night. Boy, is it a beauty. Clearly, it is not a 40s saw. I was going completely on memory without seeing the unit for several years. Looks to be a seventies era saw. I haven’t gotten the actual date but it basically looks like this minus a few differences;

Anyway, today I went to the local supply store to pick up a coil of 10-3 wire as I don’t have any 220 in my shop currently. While I was there I was becoming confused as to which plug and socket combo to buy. Old school methods of hooking 220 don’t require a neutral. I imagine a VFD with all of its sophistication would probably benefit from an up to date, modern 3 wire twist loc system.

The motor is a Rockwell 3 phase, 2 hp, dual voltage unit. Should I just get a 2hp VFD or do you (Brad) think a smaller unit would suffice? Also, if I am not mistaken, I need to make sure the motor is wired for 220 unless I want to run 440 out to my shop, which I really don’t want to do. One more thing, the VFD is basically acting as a switch, right? Can I just run a 220 cord from it to my newly installed circuit and hard wire from the VFD to my saw motor? Is there a way to use the stock switch as a disconnect between the VFD and the motor? I would like to have a secondary switch for safety reasons as I will likely mount the VFD in a less than ideal place to keep it free from dust.

Thanks, folks, for all the help. This place is a wonderful community of helpful, knowledgeable, individuals. I am glad to be a part of it.

-- Jesse, West Lafayette, Indiana

View ErichK's profile

ErichK

80 posts in 1022 days


#11 posted 08-27-2016 06:49 PM

For a VFD you always want to go a little larger. Check out a 3 or 4 hp VFD, they tend to be ~$150.

Unless you add one, the VFD doesn’t come with a plug at all, you just wire it directly. I did an L6-30 plug for mine, but directly wiring to 220 would be fine. It takes 2 wires and a ground (3 wires total). 3 Phase has 3 out and a ground (4 total), so you’ll wire that from the VFD to the saw.

You will likely need to take the wire-plate off the side of the motor when youre hooking up the VFD ANYWAY, so just check 220 vs 440 then. It is trivial to switch the motor from 220 to 440 (just a few wire nuts!).

The VFD has a ‘soft switch’. Do NOT put your table saw switch between the VFD and the motor, you lose too many features. The one I have has a hookup for a switch that you wire separately into the VFD, and it’ll power up/shut down the motor for you! I used a stock switch for mine, it is just a touch more (low voltage) wiring.

View MrUnix's profile

MrUnix

7357 posts in 2557 days


#12 posted 08-27-2016 07:32 PM

Get the serial number, as that will give you the date it was made. And get the motor data, particularly FLA, to correctly size the VFD based on amperage. There is no need to go bigger than needed unless you like spending extra money. A FM50-202 unit will set you back about $160 (same unit I’m running my 3hp Unisaw on), or a L510-202 will be about $175. You can get the cheaper Asian units, but if you stick with a US dealer (like Factroymation or Dealers Electric), you will have support should something go wrong or you need assistance. The existing start/stop switch wires into the VFD via low voltage wiring, just like it does with the starter that is on the machine now (and the starter will no longer be needed once you switch to the VFD). As mentioned above, DO NOT wire anything between the VFD and motor… you won’t just “lose features”, you will destroy the VFD by doing so.

Cheers,
Brad

-- Brad in FL - In Dog I trust... everything else is questionable

View ErichK's profile

ErichK

80 posts in 1022 days


#13 posted 08-27-2016 07:42 PM



Get the serial number, as that will give you the date it was made. And get the motor data, particularly FLA, to correctly size the VFD based on amperage. There is no need to go bigger than needed unless you like spending extra money. A FM50-202 unit will set you back about $160 (same unit I m running my 3hp Unisaw on), or a L510-202 will be about $175. You can get the cheaper Asian units, but if you stick with a US dealer (like Factroymation or Dealers Electric), you will have support should something go wrong or you need assistance. The existing start/stop switch wires into the VFD via low voltage wiring, just like it does with the starter that is on the machine now (and the starter will no longer be needed once you switch to the VFD). As mentioned above, DO NOT wire anything between the VFD and motor… you won t just “lose features”, you will destroy the VFD by doing so.

Cheers,
Brad

- MrUnix

Overbuying is usally suggested so you get the full power out of your motor. Note that motor data plate ratings are only accurate within ~10-15% as they get older, so if you have a motor that draws a little higher, it’ll trip the VFD way earlier than you’d want. In the commercial world, VFDs get overspec’ed by 10% for exactly this reason.

The TECO ones are also quite well regarded in the hobby world, though a bit more expensive. FWIW, the seller on ebay has a shipping center in California, and was quite responsive when I had questions and are quite highly rated as well in the hobby community.

As far as “Destroy the VFD” wiring something between it and the motor: That really isn’t true anymore. They still give the warning, but protection circuits/fuses will save it. That said, do NOT wire anything between the two. It won’t cause an explosion, but it’ll definitely cause headaches.

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MrUnix

7357 posts in 2557 days


#14 posted 08-27-2016 08:20 PM

Overbuying is usally suggested so you get the full power out of your motor. Note that motor data plate ratings are only accurate within ~10-15% as they get older, so if you have a motor that draws a little higher, it ll trip the VFD way earlier than you d want. In the commercial world, VFDs get overspec ed by 10% for exactly this reason.

Better not tell that to the guys running 5hp motors on the “3hp” FM50-203 :)

You are certainly free to believe what you like, but the VFD can supply up to 150% over current for a short period of time (up to 1 minute on the TECO’s), and on top of that, the motor will rarely, if ever, see full FLA in use unless you are really pushing it to it’s limits. As long as it’s rated for the motors FLA, you are not going to lose any power from the motor and won’t be anywhere near overloading the VFD. Going bigger certainly won’t hurt anything, but it’s not necessary and just costs more. The only valid reason I see to going oversized is if you plan on using it later with a larger machine.

As far as “Destroy the VFD” wiring something between it and the motor: That really isn t true anymore. They still give the warning, but protection circuits/fuses will save it. That said, do NOT wire anything between the two. It won t cause an explosion, but it ll definitely cause headaches.
- ErichK

I think I’ll stick with the manufacturers warning: Do not use a separate device to switch motor ON or OFF during operation. Otherwise, the AC drive may experience an overcurrent breakdown.

I know of at least one person who fried their VFD when the wiring from it to the motor failed, due to a user installed connector that became disconnected during use. No explosion, but lots of that nice burnt electric smell and a few hundred bucks down the drain. YMMV.

Cheers,
Brad

PS: If you do go with a sensorless vector drive like the L510, you just set a few basic parameters and then do an “autolearn” to automatically match the VFD to the motor – which will give you the best efficiency out of the motor that can be obtained.

-- Brad in FL - In Dog I trust... everything else is questionable

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Luthierman

222 posts in 1446 days


#15 posted 08-27-2016 10:06 PM

Okay. Got it. Thanks dudes. I will report back later with pics of the saw as I progress. Exciting time in my house. It sort of stinks that there isn’t a big SHUT IT DOWN switch on those VFDs. I like the the knee bump options. Ah well. I can deal.

-- Jesse, West Lafayette, Indiana

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MrUnix

7357 posts in 2557 days


#16 posted 08-30-2016 12:31 AM

It sort of stinks that there isn t a big SHUT IT DOWN switch on those VFDs. I like the the knee bump options. Ah well. I can deal.
- Luthierman

It does… or at least it can. In addition to the normal three wire control station (start/stop), you can wire in additional switches, which are assignable. For example, if you routinely cut sheet aluminium or plastic (or anything that tends to melt at a high blade speed), you can wire in a ‘slow speed’ button, or use a SPDT switch to make up a “Normal/Slow” speed switch (all speeds are programmable). Another can be wired for an emergency stop, so you can use one of those big honking “STOP” paddle switches, or several in different locations. As for knee bump, I’ve seen some creative setups where a length of PVC was mounted on the front of the machine so when it was pressed, it would push the emergency switch – a lot of surface area to hit with just about any part of your body if needed :)

Cheers,
Brad

-- Brad in FL - In Dog I trust... everything else is questionable

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Luthierman

222 posts in 1446 days


#17 posted 08-30-2016 11:48 PM

I just watched a very helpful video on how to wire in a switch. It couldn’t be easier. Thanks for steering me this way. 3 phase is pretty awesome stuff. Placing an order tonight for the L510-202. It should be plenty for a two horse that will mostly be making box joints or ripping brace material for my guitars. This machine will never be taxed in its use so I see no reason to go oversized. Thanks for the help.

And just for fun, here is the actual saw out in my workplace work shop. This saw will make it to my home shop where I do the finer work. Up next, the fence. Seriously considering making my own rails and buying the Very Super Cool Tools T-square fence. Looks legit.

-- Jesse, West Lafayette, Indiana

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Luthierman

222 posts in 1446 days


#18 posted 09-04-2016 09:46 PM

Forgive my ignorance, but the instructions aren’t very clear on the connections. First, I have 3 wire with ground 220 service in my shop. What my instincts tell me is to hook one of the power wires to L1, the other power wire to L3, and the ground and neutral to the ground posts below. Seems right. It just doesn’t explain it all that well. Basically it says make connections here. Umm. Okay. Sure. Once again, I will turn to the sage advice of this community. Also, there should be no need for the magnetic switch that used to be on this saw, right? I’m talking about the big honker that was at the bottom of the unit, not the little guy up front. I plan on actually wiring that little guy up to the vfd so it’ll still function like it should. In appearance anyway. My understanding of the signal path is that I go from my service, to the vfd, to the motor. No other connections are needed. With the exception of wiring in a switch, which isn’t really changing the path, but rather disabling the start stop button on the vfd.

-- Jesse, West Lafayette, Indiana

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MrUnix

7357 posts in 2557 days


#19 posted 09-04-2016 10:00 PM

That one is missing the L2 lug, so you don’t have much choice but to wire the 240v input to L1 and L3, along with the appropriate ground connection. If your 240v service has 3 wires plus ground, then one of those wires is the neutral, and can be ignored – just fold it back and tape it off. T1, T2 and T3 (along with ground) goes directly to the motor. Doesn’t matter which order you wire them. If it runs in reverse after it’s all hooked up, just swap any two of those three wires to change direction.

And no, you don’t need the starter that shipped with the saw (as I mentioned in post #12 above). Rip it all out except for the start/stop control station, which you will wire into the VFD. You can then sell the starter to recover some of the money (maybe all) that you spent on the VFD.

Cheers,
Brad

-- Brad in FL - In Dog I trust... everything else is questionable

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Luthierman

222 posts in 1446 days


#20 posted 09-04-2016 10:20 PM

Thanks for the confirmation. It helps to have someone in the corner, just in case.

-- Jesse, West Lafayette, Indiana

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Luthierman

222 posts in 1446 days


#21 posted 09-05-2016 12:10 AM

Huzzah! It works! However, is there a reason it shudders? If I hold it right at 30hz, it does it rather constantly. At full speed, it purrs. Through the entire range to get there, it shudders at a few intervals and then calms down. Weird.

-- Jesse, West Lafayette, Indiana

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