Hendey's Reliance motor generator has poor speed control

[Peroni]

I picked up a 1953 Hendey 9x24 with the Reliance motor generator. I managed to get the unit running by swapping in a NOS tube. It starts right up, spindle runs forward and reverse and stops pretty quick too. But I'm having a problem with the speed control rheostat. I can change the speed fine but what the dial says and what the spindle is actually turning do not agree. I've tried getting them to sync with poor results. In open belt drive if I dial up 200rpm I get 86, 1000rpm gets 367 at the spindle and 2600 comes closer but still only 2327rpm. This lathe has the high speed range of 20 to 3000rpm. I can't run it up to full speed as one of the rheostats is damaged. When I hit the damaged are the relay circled in red will start to cycle, each time doing so it throws a large spark and the speed becomes very unstable.

There are two Ohmite rheostats used here. The diagram list a pair of model N 1500 ohm - parts number RRS1K5. However on this lathe I have a different one. The generator rheostat is as listed but the motor field rheostat is a spec # 34657 1400ohm unit. This is also the one that is damaged.

Someone has been in here before me as there are a lot of newer wire terminals plus the two rheostats are connected up with wire nuts.

At this point I'm not sure what the problem is. I can't say if the motor field rheostat was replaced in the past or not, it has certainly been in there for a long time. Or could my problem be elsewhere on one of the boards? Electrical stuff like this is my weak point and I also have no prior experience with a motor generator. My last Hendey had the mechanical drive and the 10EE's I used to run were either wiad or converted to an AC motor. I do have the wiring diagrams for this machine plus a good multimeter along with a brand new RRS1K5 rheostat that came with the lathe. Some guidance as to what might be going on and where I should start checking would be welcome.

 

[Cal Haines]

I picked up a 1953 Hendey 9x24 with the Reliance motor generator. I managed to get the unit running by swapping in a NOS tube. It starts right up, spindle runs forward and reverse and stops pretty quick too. But I'm having a problem with the speed control rheostat. I can change the speed fine but what the dial says and what the spindle is actually turning do not agree. I've tried getting them to sync with poor results. In open belt drive if I dial up 200rpm I get 86, 1000rpm gets 367 at the spindle and 2600 comes closer but still only 2327rpm. This lathe has the high speed range of 20 to 3000rpm. I can't run it up to full speed as one of the rheostats is damaged. When I hit the damaged are the relay circled in red will start to cycle, each time doing so it throws a large spark and the speed becomes very unstable.
View attachment 392700

This is the first Reliance motor/generator (MG) drive that I remember seeing on a Hendy. It appears to be the same basic Ward-Leonard drive used on 10EEs, but with a different DC control panel. Where 10EEs use mechanical exciter, this one has an electronic exciter. The relay that's cycling is called out as the FV relay. On a 10EE that would be the FA (Field Acceleration) relay. It's job is to apply full field when the motor is accelerating under load.

In both cases the motor rheostat is connected in series with the spindle motor's field windings. Above base speed, the rheostat reduces the field voltage, allowing the motor to speed up. What's happening is that you're hitting an open spot in the rheostat, causing you to lose field. The motor then starts to run away, resulting in high armature current, which closes the FV relay. The FV relay bypasses the rheostat and applying full field voltage, slowing the motor until the FV relay opens, repeat.

The rheostats used in Reliance MG systems are specially wound, so that they only change resistance over half of their windings. If someone has replaced one or the other with wrong rheostat, the system won't work correctly. If you look at the rheostat's winding it should be obvious that the two halves are different. Checking with your Ohmmeter you should find that windings on one side have near zero resistance. Please post an overall photo of the winding side of the motor rheostat and a close up of the bad spot.

There are two Ohmite rheostats used here. The diagram list a pair of model N 1500 ohm - parts number RRS1K5. However on this lathe I have a different one. The generator rheostat is as listed but the motor field rheostat is a spec # 34657 1400ohm unit. This is also the one that is damaged.

View attachment 392702View attachment 392703
Someone has been in here before me as there are a lot of newer wire terminals plus the two rheostats are connected up with wire nuts.
...

I think that you're getting the rheostat part numbers from the second diagram (Hendy Wiring Diagram C45-1634D). I don't see any part numbers on the MG diagram (Reliance W/D 16306-4). I don't think the Hendy diagram applies here. The right-hand section of the Reliance diagram has a box labeled "VSX Electronic Exciter ... see W/D 15556". Do you have wiring diagram 15556?

If you can find terminals GF1 and GF2 on the MG itself (10EEs have a terminal panel on the side of the MG), check the DC voltage between the terminals as you increase the speed from minimum to base speed (base speed should be indicated on the motor's data plate; it's 690 RPM for a 10EE). You should see the voltage go from near zero to a maximum at base speed, then stay there as you continue to increase speed.

Please post a photo of the data plate on the motor and the module with the vacuum tube.

 

[Peroni]

Cal I have a few parts from another Reliance motor generator from a 1946 Hendey. That one does have the piggy back exciter on the AC motor.

Here is the 1400ohm outer rheostat, you can see the damaged spot near one end, the fine wires are broken in that area.


Here is my 'spare' 1500 ohm rheostat, it is identical to the inner one that is labeled as item 15 on Drawing C45-1634D.


This is a shot of the electronic exciter. I do not have drawing 15556 but I do have instruction sheet K-3125. It has two sets of diagrams in it but does label for which size or model they are for.


Both motor tags

 

[Cal Haines]

The damaged motor rheostat is what I expect to find in a Reliance MG drive. These are specially wound for the application. Note that the windings consist of one long winding on one side and four short winding sections on the other side. If you check, you'll find that it's resistance is 0 Ohms on the long winding side. From the point where the wiper is at the midpoint, the resistance increases from 0 to about 1400 Ohms (near the break). You need to check and see what the resistance actually is just before the open spot.

The spare rheostat's winding appear to be one continuous winding. I think you'll find that its resistance changes evenly from 0 at one end to 1400 Ohms at the other. That rheostat can't be used in place of the original motor rheostat, despite the fact that they are both about the same resistance. You indicate that another one of these was used to replace the original generator rheostat and that's not going to work correctly either.

A Ward-Leonard DC drive operates in two ranges: base speed and field weakening. In base-speed range, the spindle motor's field is held at 100% (230 VDC in this case) and the armature voltage is increased from near zero at minimum speed, to 100% (230 VDC) at base speed (690 RPM at the motor). With the field and armature at 100% (230 VDC) the motor will run at base speed. To increase above base speed, the field voltage is reduced (the field is weakened), dropping to well under 100 VDC at maximum speed (2070 RPM).

The way these MG drives function, the generator rheostat (connected as a potentiometer) changes its resistance from 0 at minimum speed to maximum resistance at the midpoint of the rheostat and stays at maximum for the second half. This increases the generator's field voltage from 0 to maximum which, in turn, increases the spindle motor's armature voltage from 0 to maximum at the control's midpoint (base speed). From midpoint on, the generator rheostat stays at maximum and the armature voltage stays at 100%.

During the entire time that the generator rheostat's resistance is changing and the generator is ramping up the motor's armature voltage, the motor rheostat stays at 0 Ohms, keeping the spindle motor's field at 100%. After the midpoint on the rheostat wipers, the motor rheostat resistance increases from 0 to maximum (1400 Ohms). The motor rheostat is connected in series with the spindle motor's field and introduces additional resistance in the field circuit, reducing the field voltage. By the time the speed control and the rheostat wipers reach the end of travel, the motor rheostat has introduced 1400 Ohms of resistance into the field circuit, fully weakening the field and causing the motor to run at full speed (2070 RPM). But when you hit the bad spot in the rheostat, the motor loses all field voltage and tries to run away, as previously discussed.

The reason that a rheostat like your spare won't work for the generator rheostat is that it only reaches 50% of the required resistance at the midpoint, where it should be at 100%, and thus the motor doesn't get full armature voltage. The motor will never reach the base speed condition. This is why the control dial is behaving oddly.

The only way to get the controls functioning as designed is to find a replacement generator rheostat and either repair or replace the motor rheostat. The replacement rheostats can be used to control the MG, but you need two knobs, so that you can individually control each rheostat.

By the way, your spindle motor has a 230 VDC armature and 230 VDC field. The newer Reliance 10EE spindle motors and MGs, starting with the piggyback-MG round-dials, have 115 VDC fields, so most 10EE rheostats won't work either.

 

[Peroni]

Cal thank you for helping me get a better grasp on how this drive functions. I may have a pair of replacement rheostats that could work? These are Ohmite 1500ohm model N's, same as listed on Hendey's diagram. They are from a 1946 Reliance VS drive that came out of another 9x24 Hendey. However they were mounted in a very different arrangement that is not a direct swap into this later machine I'm working on.

I see they are wound 'backwards' from the larger damaged rheostat. What determines the maximum speed in these drives? These rheostats were from a lathe that went 20 to 2000rpm. The one I'm working on would go 20 to 3000rpm.

Are there any other options short of a drive replacement I could look into for speed control? I currently do not fancy my chances of finding correct replacement parts.

 

[Cal Haines]

Cal thank you for helping me get a better grasp on how this drive functions. I may have a pair of replacement rheostats that could work? These are Ohmite 1500ohm model N's, same as listed on Hendey's diagram. They are from a 1946 Reliance VS drive that came out of another 9x24 Hendey. However they were mounted in a very different arrangement that is not a direct swap into this later machine I'm working on.
View attachment 392883View attachment 392884

Rheostats for a Reliance MG drive need the zero Ohm segment for one half of the windings. The motor and generator rheostat have the zero Ohm segments opposite each other, so that when one rheostat is at zero Ohms, the other's resistance is changing, and vise versa. The 1946 Reliance VS drive rheostats do not appear to be that type. The segments with different types of wire allows the way in which the resistance changes as the wiper moves to be fine tuned.

The rheostat that you called your spare 1500 Ohm rheostat is actually a little better choice:

Do you just have one of those? Is there a part number on it?

I see they are wound 'backwards' from the larger damaged rheostat. What determines the maximum speed in these drives? These rheostats were from a lathe that went 20 to 2000rpm. The one I'm working on would go 20 to 3000rpm.

The maximum speed is determined by the series resistance in the spindle motor's field circuit. That depends on how the motor's field windings are set up. Your motor has a 230 VDC field and calls for 1400 Ohms, with a maximum speed of 2070 RPM. Reliance motors with a 115 VDC field use a smaller resistor. Square-dial 10EE MGs use a 400 Ohm rheostat and have maximum speed of 2400 RPM.

Are there any other options short of a drive replacement I could look into for speed control? I currently do not fancy my chances of finding correct replacement parts.

It actually won't be very difficult at all to make the drive work with the parts that you have. By adding a DPDT (double pole double throw) switch we can make it work with the existing speed control knob and rheostat mounting method. It would work as follows: The switch would have a low and high position. In the low position, it would bypass the motor rheostat, providing full field, and letting the generator rheostat control the armature voltage. In the high position, it would bypass the generator rheostat, providing full armature voltage and allowing the motor rheostat to weaken the motor's field. I would set it up so that setting the speed control knob all the way CCW gives you minimum speed in the low switch position. As the knob is turned CW, the speed would increase, reaching base speed at the CW end. If the switch is then moved to high, the motor will still be at base speed. Dialing back the other way in the high switch position would increase the motor speed, reaching maximum speed when the knob is back at the CCW end.

The above depends on what rheostats we have to work with. Can you check the rheostats from the 1946 Reliance VS drive and see how the resistance changes? Hook one probe of your Ohmmeter to the right terminal of each rheostat, then probe the winding (where the wiper runs) about every 30 degrees and let me know what you read. Do the same thing for the 1500 Ohm "spare" rheostat.

 

[Peroni]

Cal here what I measured on the three different rheostats I have:

The 1400ohm special wound model R
.1, .3, .5, 1., 65, 325, 3760 <--- I checked this last one several times, it reads similar on either side of the damaged area.

The 1500ohm special wound model N from 1946
.25, .71, .983, 1.217, 1.284, 1.400, 1.498

'spare' 1500ohm model R
.9, 285, 485, 718, 942, 1150, 1460

As received the lathe was wired up with one 1500 model R and the 1400 model R but they were both setup the same direction, the wiper arms were both in line. Ones on the 1946 machine were mounted so the wiper arms faced each other and would rise and fall opposite.

I'm going to see if I can dig up any more specific info on how the lathe was equipped when it left the factory.