(Topic ID: 153807)

Why and when did Williams change motor nameplate from 24 to 27 volts


By SteveinTexas

3 years ago



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  • Latest reply 3 years ago by SteveinTexas
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    14A-7836_Derby_Day_Winner_Hayburner_(resized).JPG

    #1 3 years ago

    They moved the operating voltage from 50 V to 24 V in the mid 62 time frame but somewhere between then and late sixties they upped the motor voltage to 27 V from 24 V.

    Why I am intrigued is I have four running man motors all labelled as 14-A-7751 and the same identical spec number but two listed as 20 RPM at 27 volts and two are 14 RPM at 24 volts. I want to use the best two on my games and keep the others as spares.

    Steve J.

    #2 3 years ago

    Well, schematics for Grand Prix, which came out in December 1976, show the transformer output voltage as 24v. As far as I know, that's what they always used after they dropped from 50v. I've never known them to use 27v

    I looked up several other games earlier in the 70s on IPDB. All 24v for coils.

    #3 3 years ago

    You'd have to dig around but I think the motor specs for each individual game are listed in the parts manuals.

    http://www.planetarypinball.com/mm5/merchant.mvc?Screen=BOOK

    #4 3 years ago

    Yes I am unable to find examples also in the Williams parts catalogs. The motors are definitely marked as 27 Volts and one I stripped from a 73 Line Drive running man. I think Chicago Coin games used 30 Volts.

    #5 3 years ago

    Is this for Major League? I think you need motor 14A-7757 (50 cycle). Page 97 and 102.

    http://www.planetarypinball.com/reference/partsmanuals/WMS_Parts_1964/index.html#/109/zoomed

    #6 3 years ago
    Quoted from AlexF:

    Is this for Major League? I think you need motor 14A-7757 (50 cycle). Page 97 and 102.
    http://www.planetarypinball.com/reference/partsmanuals/WMS_Parts_1964/index.html#/109/zoomed

    Alex, The reproduction page is very poor if you look again that is for a 50 Hz European motor. The 14 A-7751 is correct.

    I looked on eBay and there are other late 60's examples fof Williams 27 V motors. See the snapshot of one for a Williams Derby Day, Winner, Hayburner example.

    14A-7836_Derby_Day_Winner_Hayburner_(resized).JPG

    #7 3 years ago

    Ok, that's good. Now you just need to know rpm. I wish I could help figure that out. Major League isn't that uncommon there has to be an owner that would be able to solve that mystery for you.

    #8 3 years ago

    The Derby Day schematic indicates the motor voltage at 24V. What is marked on the motor is different than the actual supplied voltage.

    #9 3 years ago
    Quoted from minnesota13:

    The Derby Day schematic indicates the motor voltage at 24V. What is marked on the motor is different than the actual supplied voltage.

    Yes and that is the case for the Major League example I have to.

    Without any other information than what is in this thread I am thinking that the additional volts the motor nameplate is designed for may be to do with the high tap connection on the transformer. Did the motor get designed to operate somewhere between the normal and high tap? I am assuming that if the transformer is on high tap then we would get a little more voltage in the motor. Possible?

    #10 3 years ago

    yup. what the transformer output is, is what everybody feels.
    unless there is a resistor in line.
    or a rectifier, in whick case, the output would be a little higher

    #11 3 years ago

    I check all four motor Rpm's tonight. All operate on a 24 v transformer on normal tap at 20 rpm. For the 27 volt motors that is per the nameplate that is correct but not the 24 volt motors that is not as the nameplate 14 rpm.

    I believe as a rule that motors pulling a few less volts pull a similar % increase in current (amps) as a rule so speed stays close to nameplate. No explanation on the 24 volt motors turning 30% above nameplate.

    I still would like to know when Williams starting using 27 volt motors over 24 volt and whether it is due to high tapping.

    I will alter the title to better reflect what the question is now.

    3 months later
    #12 3 years ago

    I spoke with Steve at Pinball Resource this week and asked about a few things after placing my order. One was about Williams motors and the difference in motor coil voltage. He suspected the possibly of people using high tap may be the reason as this would add some safety factor. This makes so much sense.

    He also stated that Multi Products designed the motor for each game unique application and this included measurements that required a selection between three different minute springs on the rotor drive shaft. Shoot, I can hardly see the springs let alone see differences!

    #13 3 years ago

    On a synchronous motor the speed will always be the same regardless of the voltage, as long as the line frequency (Hz) is constant. Synchronous motors get their speed setting from the AC frequency, not from the voltage. This is one of the big advantages of synchronous motors, because it means their speed is unaffected by voltage variations. It is also why a European 50 Hz score motor runs faster when you use it in the USA, where we have 60 Hz.

    If you run a 27 VAC 60 Hz motor at 16 VAC, 22 VAC, or 27 VAC (all at 60 Hz) the motor will always run the same speed. At the lower voltages the motor will have less power but the drive coil will run cooler. At the higher voltages the motor will have more power but the drive coil will run hotter.

    So the change from 24 VAC to 27 VAC in the motor spec could be that Williams engineering decided that a slightly under-voltage motor would still have plenty of torque for the application and the extra head room for the drive coil would make the motor more reliable (especially, as others have noted, when the game was on high-tap).

    Gottlieb did a similar thing, their score motors often being rated at 30 VAC even though the GTB transformers typically provided power several volts below that.

    - TimMe

    #14 3 years ago
    Quoted from TimMe:

    On a synchronous motor the speed will always be the same regardless of the voltage, as long as the line frequency (Hz) is constant. Synchronous motors get their speed setting from the AC frequency, not from the voltage.
    So the change from 24 VAC to 27 VAC in the motor spec could be that Williams engineering decided that a slightly under-voltage motor would still have plenty of torque for the application and the extra head room for the drive coil would make the motor more reliable (especially, as others have noted, when the game was on high-tap).
    Gottlieb did a similar thing, their score motors often being rated at 30 VAC even though the GTB transformers typically provided power several volts below that.
    - TimMe

    TimMe,

    Steve did tell me about this being a synchronous motor and how they worked but I couldn't spell all the words.
    Thank you for the excellent explanation. This makes sense to all the observations I originally made and did not fully understand until now.

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