Thread: SAG 12 Restoration Progress

Anything new with the trans oil pressure/pressure switch woes?

Originally Posted by RevetsP

Anything new with the trans oil pressure/pressure switch woes?

For testing the trans now I bypassed that problem and just screwed in the old switch to plug the hole. My plans are to get the wiring to the saddle back in so I can put the trans back in the lathe, then tackle the smaller items such as the oil pressure switch - I'll keep you posted....

Originally Posted by TexasTurnado

According to the data sheet that came with it, it is rated at ±1 count to 5999 rpm, and ±2 counts 6000 to 25,000 rpm! I had no idea it would go that high, but it uses a 32.768 KHz crystal clock (same as watches, I think) to get the high accuracy.... It came with three points that slide on the end for different attachment options - the large disc is sized to give FPM readings for surface speed. The disc is supposed to be 6.0 inches in circumference, so it looks like it should read .5 FPM for each count.

Checked out Mitutoyo, apparently newer version goes to 100k and non-contact too......which might make it applicable to something else I had in mind without spending a small fortune.

Any thoughts on timers by the way? Never ending saga here, suggests this one is kaput, hence the bypass that was put in place - and I'm not inclined to re-install obsolete electrics, even if available in some back corner of Italy.

Originally Posted by BillE

Any thoughts on timers by the way? Never ending saga here, suggests this one is kaput, hence the bypass that was put in place - and I'm not inclined to re-install obsolete electrics, even if available in some back corner of Italy.

I have not given timers any consideration at this point - I was under the impression that one could just hold the start button down for a few seconds manually until the pressure was high enough to operate the pressure switch and a timer was not needed - is that not the case? If a timer really is needed, then there are solid state time delay relays that should do the trick.... or one can use something like a 555 timer ic and do it with a standard relay.

Anyway, I thought the bypass was done because the pressure switch was bad (causing the lathe to stop after starting) and unrelated to the timer circuit.... As I understand the timer circuit, it has contacts that keep the circuit closed (after the pushbutton on the panel is released) until the pressure closes the contacts on the pressure switch. Once the ps contacts close, it does not matter what the timer contacts do (but they should open after the timeout period so the ps can stop the lathe if it indeed does lose oil pressure)....

Yeah, the contacts didn't close in the switch - so that was the assumed cause for the bridging, further digging by the sparky and he thinks the timer is duff too. Suppose holding the start button down for 5 seconds or so shouldn't be much of a hardship, if that addresses the problem.

Originally Posted by RevetsP

Anything new with the trans oil pressure/pressure switch woes?

I decided I was entitled to a little machining time.... So I shortened the piece you sent me a bit, and made a nipple to screw into it and also have 1/8 BSPP on the other side. Now I just need a sealing washer to go between the oil pump and this adaptor:

Hi Tex,

I would say a bonded seal will do the job.

Bertus

Glad to see it's working for ya! I'm assuming the casting is spot-faced for a washer/seal? What about the original, or any kind of standard banjo washer/seal?

Also, have you tested the switch out at all?

Yes, the oil pump is spot faced for the standard BSPP sealing washer (straight or parallel pipe threads need a sealing washer) - but I can't seem to locate the original. I think it needs to be a bit thicker anyway as I was not able to turn the BSPP theads as close to the shoulder as I would have liked - my fault though, I should have ground the 55º cutting tool asymmetrical just for that reason.... I think I will make the washer from C110 copper.

Have not been able to check the switch as yet - do you know what pressure it closes at? Also, what was the original application for this 1/8 BSPT two terminal switch in case I need another?

Originally Posted by TexasTurnado

Yes, the oil pump is spot faced for the standard BSPP sealing washer (straight or parallel pipe threads need a sealing washer) - but I can't seem to locate the original. I think it needs to be a bit thicker anyway as I was not able to turn the BSPP theads as close to the shoulder as I would have liked - my fault though, I should have ground the 55º cutting tool asymmetrical just for that reason.... I think I will make the washer from C110 copper.

Have not been able to check the switch as yet - do you know what pressure it closes at? Also, what was the original application for this 1/8 BSPT two terminal switch in case I need another?

This particular unit was off of a motorcycle front brake line ('76 kawasaki KZ400, but Kawasaki used these on alot of their models brake lines), the switch controlled the brake lights. From what I could tell it was a metal diaphram in there so it should be ok with oil/ATF. As far as pressure I could'nt tell you exactly but it does not take much at all the get it to close, unlike an low oil pressure switch (or, "its too late!" switch on motorcycles). Any brake like pressure switch should be nearly identical to this.

Originally Posted by BillE

Yeah, the contacts didn't close in the switch - so that was the assumed cause for the bridging, further digging by the sparky and he thinks the timer is duff too. Suppose holding the start button down for 5 seconds or so shouldn't be much of a hardship, if that addresses the problem.

If you think the timer is not working correctly, replace the capacitor first - these tend to lose their capacitance over time and may be timing out too soon. About the only other thing it could be (other than faulty wiring) is the relay itself....

There is an old style capacitor in place that's been hacked in at some stage, I'm told, there's going to be an Eaton timer installed rather than spend time chasing gremlins. Ideally the electrician said he'd junk the lot and start from scratch with modern electronics and DIN rails, but he'll see if he can get this rubbish to operate for now. Slow feed clutch at the tailstock end appears to have gone out now too for added joy!

Originally Posted by BillE

There is an old style capacitor in place that's been hacked in at some stage, I'm told, there's going to be an Eaton timer installed rather than spend time chasing gremlins. Ideally the electrician said he'd junk the lot and start from scratch with modern electronics and DIN rails, but he'll see if he can get this rubbish to operate for now. Slow feed clutch at the tailstock end appears to have gone out now too for added joy!

Getting rid of that old stuff (except the transformer) is probably a good idea - I have no idea if fuses could be found to replace the ones in there now. And since using a VFD eliminates the need for main motor starter - just a simple disconnect switch would suffice. Something would need to be done for the coolant pump, but small VFD's can often be had for $50 or less on ebay.

The pressure switch could be wired into the VFD inputs to shut it down if the ps opened (and the timer could be eliminated if one is willing to hold the start switch down until the ps closed). If wanted, a led could be used to signal the ps had closed and the start button released....


The 24VDC for the clutches would still be needed, but by using the relay contacts inside the VFD (they are not high voltage/ high current) to switch it on only if the motor is running (eliminates the cooking problem of the clutches as happened with the ps contacts bypassed).

The 24VDC supply is powered from a 32VAC winding on the transformer and the contactors are all powered from the 24VAC winding on the same transformer originally, but by using two VFD's (one for the main motor and one for the coolant pump) these contactors could be eliminated as well as the second winding on the transfromer secondary. That transformer is a custom design, and if it ever goes out, it will have the be rewound or replaced with two separate transfromers (or a custom wound unit - $$$).

Of course, the lathe would now be a single voltage lathe, but that happens as soon as you incorporate a VFD in the first place.... In return you get variable speed (on the coolant pump also... ) and no need for the two motor starters with their contactor coils.

I have not given this a whole lot of thought, but at the point I can actually turn the lathe on it will take center stage!

"Slow feed clutch at the tailstock end appears to have gone out now too for added joy!"

Sorry to hear of more troubles, but I am not following which part you are describing here....

Less inclined to get rid of the electrics myself, spent more than I was expecting already, but if needs be.....and it simplifies bug tracing for him, might come to that.

The ceramic bottle fuses don't seem to be a problem to come across down here, probably less common than the modern cylindrical type, but picked up a bag of them for about $10 some time ago. I do remember there's been a few mentions of it on this site as being difficult to find over there though.

On the other hand - and I don't believe they're on a 12 - the little glass Fusit branded ones, holders and spring loaded caps seem unique and they'll probably end up in the garbage.....I think they related to the automatic control on this anyhow.

Don't know much about VFDs, and being a near electrical illiterate, probably a good thing too! Always had the good fortune of having 415v at a nearby socket.

Would have confused you on the clutch, it's the rapids gearbox one, not the feed EKR2(?) and 30V. It was sent away with the others but there's no continuity in the coil for some reason.....or that's what I'm reading on the meter, hopefully someone more competent will double check. The bayonet style connection on it might be the issue perhaps. Certainly not inclined to dismantle the enclosure and then the box to access it again....not as if much long work is done where it might have some use either.

You must be very close now.....or do you want to poke the devil between the headstock and transmission.

before I needed it.... :



As you can see, my fuses look nothing like you are describing - or like the picture in the manual, for that matter! I'm not even sure this was from the factory. For one thing, there is an extra relay (upper right corner, right of the timer components). For another, I'm not sure they had even started making those wiring channels in the 70's.

BTW, new data point on when my lathe may have been made: the electrolytic capacitor in the timer circuit is dated 1975 - oh, and it's 1000 uF at 50 Volts.

I tried to match the schematic to what I have, but several nice-to-know details are left out: like which terminals of the motor starters are the coil - pretty clear it has to be a and b, but they are not marked on the actual units so that's an educated guess. Also, there's a little letter b on what appears to be the heaters, but again, just a guess on my part. Fortunately, I know how the circuit basically has to work, but getting the diagram to explain the details has not been straight forward.

Upper left is the mechanical input disconnect from the supply lines, below that is the dual secondary transformer. I have not verified this by wires, but I expect the 3 large fuses to be for the main motor, and the two smaller ones to protect each secondary winding from over current. Right of the two smaller fuses is the timer circuit and right of that is the extra unknown relay. At this point I am guessing it was added to handle the current of the timer circuit, as the contacts on that smaller relay are miniscule (but gold plated! ).

The main motor starter is below the unknown relay, with the coolant pump motor started under that - the bridge diode silicon rectifier is at the bottom, and replaces the antique selenium rectifier stack shown in the manual pic. The terminal strip at the right (which is really the bottom of the assembly when it's in it's box) is where all of the interconnections to the joystick and electrical transmission are made, as well as the power input and motor electrical connections.

The other thing making understanding the circuitry difficult is the places on the schematic where wires cross is not consistently marked as to whether there is a connection at the crossing point, or if it is a cross over point (no electrical connection). I have a bad feeling I may have to draw my own schematic before this is over.....

Oh, and a question for the readers: There are six devices (one on each of the clutch wires) that are round discs with a lead soldered on each side (like a ceramic disc capacitor without its coating) about 3/8 in (10mm) in dia marked with "150/4" that only make any sense to me if they are MOV type surge protectors - again, were these in existence in 1975? Or can someone identify what they really are?

I thought the cable channel was put in at some later stage too during a rework. The 210 on ebay - early 1980s vintage? has them as well, so must have been around back then, unless there's a few astounding coincidences. I notice he has the same singular relay near the timer.

Capacitor is the same, can't say I noticed a date printed on it. Timer and rectifiers identical....one more here.

Is the pump 3 phase or fused elsewhere?

The ceramic diazed version fuses, I assumed would have been used within the range around that date, although again, the ebay lathe has your type. These were made by Sipa, so maybe those long cylindrical ones come from them as well, the short ones look garden variety.

Did notice what I thought were capacitors in the rapids gearbox bridging both wires for the clutches back there.

Now that you have gotten me started on this....

I spent a couple of hours with the digital multimeter and discovered the timer circuit cannot work as I (and I suspect others) thought it did. Instead of holding the motor starter closed for the pressure switch contacts to close, it is wired to keep the motor starter closed for short dropouts of the ps while running - just guessing, I would think it is covering for such things as air bubbles in the oil line, etc.

The motor starters stay closed after the initial push of the start button by using an auxiliary contact to apply coil voltage after the momentary push button is released. Normally, the stop button (normally closed) is pushed to remove the coil volage to the contactor and once it starts to open and opens the auxiliary contact, it will continue to open - to only way to restart the motor is to re-push the start button.

Graziano is using the ps contact to apply coil voltage to the contactor, so even a momentary opening of the ps contact due to a drop in oil pressure will shut the motor down. The function of the timer circuit is to parallel the ps contacts and stay closed during this momentary drop of oil pressure. To do this, they use a 1000 uF cap across the 930 ohm resistance of the timer relay coil, giving a time constant of almost 1 second.

Unfortunately, this design requires to ps contacts to charge the 1000 uF cap every time they close, so it's no wonder they do not last very long! There has to be a better way to keep the timer relay closed......

I also realized during this more detailed examination of the circuitry the statement I made earlier about the voltage being applied to the clutches even when the motor is stopped is incorrect - by running the voltage supply line for the clutches thru another set of auxiliary contacts on the motor starter, no voltage is present on the clutches unless the motor starter is closed.... implying the motor should be running. With this arrangement, the clutch voltage is removed even if the motor is stopped by the heaters of the starter from overload.

Here is a close-up pic of the mystery devices I asked about in my last post:



As I mentioned then, they only make sense the way they are connected if they are surge voltage devices when the clutch current is interrupted.....

Also, I deciphered the function of the second unknown relay: it is connected to the push button on the joystick and used to apply the brake by turning on both the forward and reverse clutches at the same time. Wires are connected to both clutch 5 and clutch 6 using a diode in series with each line so the connection of the two together does not interfere with normal operation - here is a close-up of the that relay with the protective cover removed:



The two diodes are at the lower right of the pic and are green in color. Note the relay used has two extra set of contacts, so if one gets pitted from use, one can just rewire to another set...

Originally Posted by BillE

I thought the cable channel was put in at some later stage too during a rework. The 210 on ebay - early 1980s vintage? has them as well, so must have been around back then, unless there's a few astounding coincidences. I notice he has the same singular relay near the timer.

Capacitor is the same, can't say I noticed a date printed on it. Timer and rectifiers identical....one more here.

Is the pump 3 phase or fused elsewhere?

The ceramic diazed version fuses, I assumed would have been used within the range around that date, although again, the ebay lathe has your type. These were made by Sipa, so maybe those long cylindrical ones come from them as well, the short ones look garden variety.

Did notice what I thought were capacitors in the rapids gearbox bridging both wires for the clutches back there.

After looking at it closely and looking for extra holes on the backside, I believe what I have is a factory job - the wires are all numbered in agreement with the schematic (except those not present... ). Apparently, the 3 phase coolant pump lost it's fuses when the brake relay was added. On mine the motor starter with its heaters are being considered adequate.

The big fuses in mine are Gould TRS-30, but notice they are a bit shorter than the holder would allow, so may not be original - 30A is too large for any real protection of the motor and I noticed both adjustable current settings on the motor starters were maxed out as well - perhaps the previous owner thought bigger was better....

The relay currently being used for the timer circuit has a second set of contacts that are currently unused (it is a double pole double throw [DPDT] relay). The current design has the 1000 uF electolytic cap hard wired across the 930 ohm coil - instead, if the cap were connected to the common terminal of the unused side and the coresponding normally open contact of the relay were connected to the coil where the hard connection was, then the pressure switch would only see the coil resistance when it closed and the very high surge would be avoided on closure it the cap was already charged to +24 volts.

To accomplish this, the normally closed contact could be connected to +24 v thru a resistor to "trickle charge" the cap to +24 v as soon as the main breaker were closed.

Any comments from the readers out there? Is there an easier way to avoid the high surge of charging the 1000 uF cap at turn on? The basic problem is the cap looks almost like a short circuit the instant the ps contacts close in the current design - if the ESR (equivalent series resistance) of the cap was 1 ohm, then the initial surge from 24 v would be 24 amps!

Your sleuthing should be quite useful John, I'll print it out! Every time the sparky arrives...and I was hoping for today again, he has to re-familiarize and ends up talking to himself about N/O and N/C switches while waving hands in the air trying to work out the logic.

Originally Posted by TexasTurnado

Also, I deciphered the function of the second unknown relay: it is connected to the push button on the joystick and used to apply the brake by turning on both the forward and reverse clutches at the same time. Wires are connected to both clutch 5 and clutch 6 using a diode in series with each line so the connection of the two together does not interfere with normal operation - here is a close-up of the that relay with the protective cover removed:

Is that certain? Would have thought that necessitates the motor going off-line and then restarting after each use?


No evidence of anything like your mystery item at all, hardly a good indication with this thing....need some 12 owners to pipe up!

The main motor fuses here are 50A, quite a bit more than another lathe of the same hp nearby - odd.

You've mentioned "heater" a couple of times too, you might be talking to a brick wall maybe , but is that a NA usage? Not familiar with that term.