Round Dial Rheostat Measurements - Test - Etc
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    Default Round Dial Rheostat Measurements - Test - Etc

    So cleaned up a bit my rheostat trying to figure out if it is good to go and came up with the following readings. I don't have much to compare it with, but poking around it seems about right. What say ye?

    rheostat.jpg
    Last edited by rakort; 05-13-2018 at 10:04 PM. Reason: title typo!

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    Can you post the pertinent part of a schematic?

    Did you make the measurements with the rheostat connected or disconnected?

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    Quote Originally Posted by rakort View Post
    So cleaned up a bit my rheostat trying to figure out if it is good to go and came up with the following readings. I don't have much to compare it with, but poking around it seems about right. What say ye?

    rheostat.jpg
    MUST be out of circuit. Is not complicated.

    Motor sez max RPM is 2400 right on the data plate, and that it is accomplished with 400 Ohms in series with the field. Reliance nor Monarch didn't cheat much on that. I don't get quite exactly that neat a reading, even so. Almost certainly the 75 years of wear on the portion of the resistance wire under the slider that mine are lower. High 300-somethings. Matters not much so long as they do not overheat and play FUSE!



    That's a current-limiting or Rheostat-connected circuit, BTW.

    Voltages measured are the byproduct of it and the winding's properties, not off a potentiometer-connected voltage divider.

    Each of those training-potty toilet-seats are wound with the full 400 Ohm or near-as-dammit on one side of half-travel or the opposite, plain wire the other half of travel.

    Tedious but not HARD to buy the wire and rewind them from bare porcelain if one must do. Not that much harder to make new sliders. The porcelain or Steatite form AFAIK is still sold, new as blanks or used in custom-order wound high Wattage variables. The braking resistor segmented forms certainly are still stocked.

    A competent farrier could learn to keep an MG running. Only a Modular wants the slightly more technologically advanced skill level of a motorcycle mechanic.

    One DOES have to expand an education. And/or dig history. These goods are simply no longer in common use.

    That works. More about need and dedication than brilliance. It pays-off in independence as to keeping your machine running at its best. Sameset ofequatiosn as runnign a vintage bke or motorcar. Lower risk of speeding tickets is all.

    Either way, be rich or be willing to dig-in and master what yah need to know for a good grade of DIY effort. 10EE are unusual. Uncommon. That ain't quite the same as Voodoo or similar persuasions of black magic.


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    Quote Originally Posted by rakort View Post
    So cleaned up a bit my rheostat trying to figure out if it is good to go and came up with the following readings. I don't have much to compare it with, but poking around it seems about right. What say ye?

    rheostat.jpg
    Brian,

    Both rheostats are wound so that their resistance only varies over half of their rotation. The resistance readings change at 50% of rheostat's rotation. I haven't made detailed measurements on the rheostats in my round-dial, but did check out the rheostats for my square-dial MG set.

    The generator rheostat controls the field voltage for the DC generator and ultimately the spindle motor's armature voltage. Measuring from terminals GR1 to E2 just gives you the resistance of the rheostat's windings. My square-dial rheostat measures 660 Ohms as well. Measuring from terminals GF2 to E2 (disconnected from load, of course) you should see the reading change linearly from 0 to 660 Ohms for the first half the rotation (starting at minimum speed) and at 660 Ohms above that. 0 Ohms between GF2 and E2 results in 0 volts on the generator's field and no voltage on the spindle motor's armature. 660 Ohms between GF2 and E2 applies maximum (115 VDC) voltage on the generator's field and maximum output voltage (230 VDC) to the spindle motor.

    The motor rheostat controls the spindle motor's field voltage by introducing a resistance in series with the field. You should see 0 Ohms for the first half of the rotation, then the resistance should vary linearly from 0 to the maximum. My square dial rheostat maxed out at 275 Ohms at the max speed setting. The windings actually go to a measured 390 Ohms (the rheostat is marked 375 Ohms), but there's an adjustable stop that keeps you from getting to the end of the winding. The big jump that you're seeing, from 67 to 500 Ohms, looks suspicious. There may be a dirty section on the windings. You should remove the rheostats, clean the windings and check the wipers. While they're out, look to see what markings you can find on them and if either one is marked with its maximum resistance.

    Here's a link that contains an explanation of how the two rheostats are connected and how they function:
    I hope that helps.

    Cal

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    Quote Originally Posted by thermite View Post
    MUST be out of circuit. Is not complicated.

    Either way, be rich or be willing to dig-in and master what yah need to know for a good grade of DIY effort. 10EE are unusual. Uncommon. That ain't quite the same as Voodoo or similar persuasions of black magic.


    Definitely out of circuit. Always dig and master what I own....kind of a freak show that way. Obviously why I'm here analyzing this stat. Some where in the Rhetoric I think I heard I should be looking for something 400 ohms not the 600 ish I was seeing. I found out my fluke is puke for measuring resistance so I'm trying to retrain myself to operate my micronta (radio shack) circa 1980 that has been horribly reliable, but a finicky analog instrument.

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    Quote Originally Posted by rakort View Post
    Definitely out of circuit. Always dig and master what I own....kind of a freak show that way. Obviously why I'm here analyzing this stat. Some where in the Rhetoric I think I heard I should be looking for something 400 ohms not the 600 ish I was seeing. I found out my fluke is puke for measuring resistance so I'm trying to retrain myself to operate my micronta (radio shack) circa 1980 that has been horribly reliable, but a finicky analog instrument.
    660 Ohms is correct for the generator rheostat. The motor rheostat rating depends in the resistance of the spindle motor's field windings. 400 Ohms is a good number for a motor with 115 V field. The data plate for the square-dial spindle motor is even stamped 400 Ohms for 2400 RPMs (yet the matching rheostat was marked 390 Ohms and set to a maximum resistance of 275 Ohms). (And no, I don't know if the motor reaches full speed at that resistance--all I have is the MG set and I've never powered it up.)

    When you get the rheostats out, you'll find that the motor rheostat has a jumper between the wiper and one of the winding terminals. Disconnect the jumper and read the resistance between the terminals at either end of the winding. Compare that reading to the value marked on the rheostat, if any. If you get a reading between the wiper and terminal E2 that's any higher than the resistance of the entire winding, over the travel of the wiper, then something is wrong with the wiper. Look at both wipers and make sure that there is still some meat left on the brushes and that the metal of the arms can't contact the windings.

    I would appreciate photos of the rheostats and of the stop, if you get a chance.

    Cal

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    Quote Originally Posted by rakort View Post
    Definitely out of circuit. Always dig and master what I own....kind of a freak show that way. Obviously why I'm here analyzing this stat. Some where in the Rhetoric I think I heard I should be looking for something 400 ohms not the 600 ish I was seeing. I found out my fluke is puke for measuring resistance so I'm trying to retrain myself to operate my micronta (radio shack) circa 1980 that has been horribly reliable, but a finicky analog instrument.
    Got some kinda curse here that I can discard an old 'scope, but never a meter, so yah. RCA Voltohmist through Fluke and wotever else I've added the past year there are 2 or 3 "Micronta", some Lafayette, Triplett, Simpson, Weston.. etc.

    Don't knock 'em. Use 'em!

    Not many things on a 10EE really need high-precision meters. Your most-appropriate meter goes WHERE appropriate, others where they are good enough.

    It is right handy and MUCH safer to have as many as 3 even 4 meters pre-hooked-up before running a hands-safely-out-of-danger test on lots of 10EE's ish things.

    This ain't no audio gear nor PeeCee motherboard.

    Lethal voltages, rather.

    Bad habit to probe about on a hot rig. "Stick and fry" DC can easily - as Peter used to put it - "rectumfry" a body!

    Set up the leads first, "COLD", back off. Don't mess about "hot". Run your test, take note of readings, shut down.

    Confirm "disconnect". Twice. Before moving the clip-ons for a different test. The more meters, the fewer moves.

    The extra effort and care will only SEEM slower because you are still alive to notice!

    There are BOLD HV DC technicians. There are OLD HV DC technicians.

    There ARE NO Old, Bold, HV DC technicians.


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    Quote Originally Posted by thermite View Post

    It is right handy and MUCH safer to have as many as 3 even 4 meters pre-hooked-up before running a hands-safely-out-of-danger test on lots of 10EE's ish things.

    This ain't no audio gear nor PeeCee motherboard.

    Lethal voltages, rather.


    I am a safety nazi and can't agree more with these comments....kids....keep your fingers out of there when messing with unknow voltages and available currents.

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    Quote Originally Posted by Cal Haines View Post
    660 Ohms is correct for the generator rheostat. The motor rheostat rating depends in the resistance of the spindle motor's field windings. 400 Ohms is a good number for a motor with 115 V field. The data plate for the square-dial spindle motor is even stamped 400 Ohms for 2400 RPMs (yet the matching rheostat was marked 390 Ohms and set to a maximum resistance of 275 Ohms). (And no, I don't know if the motor reaches full speed at that resistance--all I have is the MG set and I've never powered it up.)

    When you get the rheostats out, you'll find that the motor rheostat has a jumper between the wiper and one of the winding terminals. Disconnect the jumper and read the resistance between the terminals at either end of the winding. Compare that reading to the value marked on the rheostat, if any. If you get a reading between the wiper and terminal E2 that's any higher than the resistance of the entire winding, over the travel of the wiper, then something is wrong with the wiper. Look at both wipers and make sure that there is still some meat left on the brushes and that the metal of the arms can't contact the windings.

    I would appreciate photos of the rheostats and of the stop, if you get a chance.

    Cal
    Thanks for the insight and confirmation that I'm on the right (600 ohmish) track with the 'stat. Interesting that the pixs will show that I found an OE marking reading 625 which I assume is resistance rating. I do understand that 'stats should be reading from 0 to something then at the half way mark or so the resistance locks in for the other half of the turn as my table showed. In the end, I am happy with the test results and think the rheostat is in serviceable shape.

    With out further delay, pictures(including the stop):

    thanks for your help and insight Cal

    img_20180514_220018645.jpg

    img_20180514_220030914.jpg

    img_20180514_220040741.jpg

    img_20180514_220057254.jpg

    img_20180514_220146990.jpg

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    img_20180514_220004806.jpg

    last pix

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    Quote Originally Posted by rakort View Post
    T I am happy with the test results and think the rheostat is in serviceable shape.
    Concur. Besides the electrical tests, cosmetically they look better than my dirtier set, almost as clean as my cleaner set - long overdue to be packed and shipped to another PM member, hopefully this week, the leg healing much faster now.

    It aggravates me a tad that the ceramic is not easier to get clean because my mind's eye sees "leakage path" and a place for an arc to travel.

    That said, the very length of any such path at the relatively low voltages involved PLUS... 10EE NOT being known for having such problems over the better part of 80 years indicate it has not been an issue, and probably will never become one.

    Besides.. over-zealous attempts to clean the ceramic are all-too likely to risk damage to the "working" bits - the wound wires, slider, and their terminations to the lugs.

    I'd say wire it up, fire it up, see if any of the other players refuse to salute, then sort THEIR hash if need be.

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    Quote Originally Posted by rakort View Post
    Thanks for the insight and confirmation that I'm on the right (600 ohmish) track with the 'stat. Interesting that the pixs will show that I found an OE marking reading 625 which I assume is resistance rating. I do understand that 'stats should be reading from 0 to something then at the half way mark or so the resistance locks in for the other half of the turn as my table showed. In the end, I am happy with the test results and think the rheostat is in serviceable shape. ...

    img_20180514_220057254.jpg

    img_20180514_220146990.jpg
    Just to be clear, the 625 Ohm nominal value only applies to the generator rheostat.

    The motor rheostat should be reading about 400 Ohms max. Your readings had a value of 500 Ohms at the end of travel. 100 Ohms additional resistance in the field is not in the "right-ish" realm and needs additional follow up, as that might cause the motor to over-speed. As I said before, the big jump in resistance on the motor rheostat is not good. You're getting about 4 Ohms per percent-travel from 60 to 75%, and 17 Ohms/percent-travel after 75%. That's a factor of four change in a device that should be linear. RED FLAG! A jump like that will result in poor speed control, at a minimum. You need to get a reliable meter and check the reading from terminal F2 to the unmarked terminal with the jumper (that is, check the value of the full winding) and compare that to the reading you get from E1 to F2 at any position; IF your E1-F2 values exceed the winding resistance, THEN you have a wiper problem. One way to do the test without removing the jumper is to lift the wiper and slip a thin piece of card stock underneath to isolate it from the winding.

    I'm seeing quite a bit of black residue on the windings. You should try gently cleaning them with 600 grit wet-dry sandpaper; stop when the black stuff is gone. Then check your measurements again. If there's any doubt about your Ohm-meter, pick up a pack of 5% rated 100 Ohm resistors and use them to check your meter. Two 100 Ohm resistors in series should read 200 Ohms, etc.

    I can't tell if your stop is working. It should look like this:

    img11274.jpg

    Make sure first pin bumps into the head of the bolt.

    Cal

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    OK I'm right on track. I measured 400 ohms and wrote down 400 and in my table typoed it up with 500 ohms.

    So 'stats are swinging from 1ish to 400 ohms and the other from 1ish to 660 ohms. Both swing to the mid point then hold solid the rest of the rotation. As you pointed out Cal there is a decided lesser ramp rate in the early part of the rotation. that point persists after a 2nd round of measurements.

    Good catch on the 500 ohms...and sorry for my bad translation.

    On my rig the stop bolt is sucked in MUCH more that yours and doesn't seem to contact the pin nicely. I'll figure that out in fact I think I saw a link/thread on how to setup this stop/bolt.

    Oh yeah, that other thread....in the chichi weeds! LOL I thought I smelled smoke.

    One thing that is bothering me about this rig is one wiper has some "rotational" slop (5 degrees ish). Not sure how the whole wiper attaches to the shaft with some piece of ceramic and some sort of keyway.

    Any one blow one of these up with pixs?

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    Quote Originally Posted by rakort View Post
    One thing that is bothering me about this rig is one wiper has some "rotational" slop (5 degrees ish). Not sure how the whole wiper attaches to the shaft with some piece of ceramic and some sort of keyway.

    Any one blow one of these up with pixs?
    Could, but your one and its wear is what needs looked at if anyone has an easy fix.

    Magnifier & verbal description, if not camera?

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    Quote Originally Posted by rakort View Post
    ...

    So 'stats are swinging from 1ish to 400 ohms and the other from 1ish to 660 ohms. Both swing to the mid point then hold solid the rest of the rotation. As you pointed out Cal there is a decided lesser ramp rate in the early part of the rotation. that point persists after a 2nd round of measurements.

    ...
    The only way that there can be a factor of four difference in the rate of change of resistance with rotation is if they used different types of wire in the second part of the winding. (I have no idea why they would go to that trouble.) If you look closely, the diameter and/or appearance of the windings should change where the resistance per turn changes, and you should be able to find the splice in the two different types of wire.

    If you managed to sort out your Ohm-meter problems, do me a favor and check the resistance across groups of five or ten winding turns, over the half of the winding where the resistance changes, and see if you can find the spot where the wire type changes.

    Cal

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    Quote Originally Posted by Cal Haines View Post
    The only way that there can be a factor of four difference in the rate of change of resistance with rotation is if they used different types of wire in the second part of the winding. (I have no idea why they would go to that trouble.) If you look closely, the diameter and/or appearance of the windings should change where the resistance per turn changes, and you should be able to find the splice in the two different types of wire.

    If you managed to sort out your Ohm-meter problems, do me a favor and check the resistance across groups of five or ten winding turns, over the half of the winding where the resistance changes, and see if you can find the spot where the wire type changes.

    Cal

    I hear you on the non linear resistance readings. I'm confident on the readings. I have no less that 3 meters to cross reference and reconcile the readings. As I said though my fluke is puke in this regards so results there were discarded. I will do some tests like you suggest regarding resistance between a few turns, but not tonight....its been a day....


    For sure as at you look at my windings you see where there were splices made in the wires during the winding process, but haven't tried to reconcile that with the non linear ramp rate.

    here is an example and there are several more....
    splice-1.jpg

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    Quote Originally Posted by rakort View Post
    I hear you on the non linear resistance readings. I'm confident on the readings. I have no less that 3 meters to cross reference and reconcile the readings. As I said though my fluke is puke in this regards so results there were discarded. I will do some tests like you suggest regarding resistance between a few turns, but not tonight....its been a day....

    For sure as at you look at my windings you see where there were splices made in the wires during the winding process, but haven't tried to reconcile that with the non linear ramp rate.
    Cal,

    there are four distinct zones (~ 45 degrees of rotation) in half of the E1-F2 winding (~180 degrees worth) Each zone is separated by a slice in the winding

    there are three distinct zones in half of the E2-GF2 winding (~180 degrees worth) Each zone is separated by a splice in the winding

    There must be a different wire in each zone as the "ramp" rate is different in each zone

    Resistance Readings as follows:
    capture2.jpg


    Graphically:

    capture.jpg
    Last edited by rakort; 05-18-2018 at 04:03 PM. Reason: typo

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    Quote Originally Posted by rakort View Post
    Cal,

    there are four distinct zones (~ 45 degrees of rotation) in half of the E1-F2 winding (~180 degrees worth) Each zone is separated by a slice in the winding

    there are three distinct zones in half of the E2-GF2 winding (~180 degrees worth) Each zone is separated by a slice in the winding

    There must be a different wire in each zone as the "ramp" rate is different in each one

    Resistance Readings as follows:
    capture2.jpg


    Graphically:

    capture.jpg
    Brilliant work!

    Goes a long way toward explaining what Monarch did to make the 10EE work as well as it did, and why a restoral - any era - has merit rather than a conversion.

    Tuning for its purpose!

    I don't think anyone has previously looked at it in this depth - just USED the buggers.

    I have an (over) "due out" set of Ohmites being donated, and another part out set, spare.

    I'll see it I can move enough other shite to get close enough to the test bench to confirm that over the weekend.

    Good on yah!

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    Quote Originally Posted by rakort View Post
    Cal,

    there are four distinct zones (~ 45 degrees of rotation) in half of the E1-F2 winding (~180 degrees worth) Each zone is separated by a slice in the winding

    there are three distinct zones in half of the E2-GF2 winding (~180 degrees worth) Each zone is separated by a slice in the winding

    There must be a different wire in each zone as the "ramp" rate is different in each one

    Resistance Readings as follows:
    capture2.jpg


    Graphically:

    capture.jpg
    Thanks for that! That's new information and very interesting.

    I'm confused by your rotation numbers. Are you using the wiper angle, or what? I'm asking because there isn't a full 180 degrees rotation from the middle, more like 160-170 degrees.

    Cal

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    Quote Originally Posted by Cal Haines View Post
    Thanks for that! That's new information and very interesting.

    I'm confused by your rotation numbers. Are you using the wiper angle, or what? I'm asking because there isn't a full 180 degrees rotation from the middle, more like 160-170 degrees.

    Cal
    Yes good info I agree. Bottom line is it is not linear and like therm pointed out it was an old school method to tune the performance of the MG set. Don't read too much into the exact angular measurements. Yes you are right, the 'stat doesn't rotate a full 360 degrees. I simply eye balled it and called half way 180 degrees even though, like you said, it was probably 165 or so. I didn't actually measure the angular movement. For sure I do know that one zone had three roughly equal increments before it hit the midpoint and the other had four zones. I called mid point 180 degrees.

    I have not, like you requested, did any measurements from turn to turn, but my conclusion is there is a varying resistance ramp rate throughout the rotation of the 'stat.


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