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  1. #1
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    Default Colchester electromagnetic brake

    G/day all, I have a colchester master 2500 and would like the electro brake to engage a bit quicker, it takes about 1 to 1 1/2 seconds after the clutch lever is thrown into neutral before the brake hits the skids and I can see problems ahead.

    It might not sound like an issue but when you want to stop NOW !!!!!! it doesn't............

    With this lathe when the clutch is engaged and the spindle/chuck is turning power is applied to the brake coil to hold the brake in the disengaged position, when the clutch lever is thrown into neutral power to the coil is switched off , supposedly, and about 1 to 1 1/2 seconds later the brake clicks as the spring pressure applies the brake.

    I wouldn't have thought that the capacitor attached to the brake coil wires would hold the brake coil energized for that length of time? The capacitor doesn't appear to be on the schematic so maybe it is the culprit and should not be there ?????

    The brake coil operates on about 120 v dc and has 252 ohms resistance. I can't see any other capacitors or timers.

    3KIM is the brake contactor.

    So what I would like to know is how can I speed this brake application up?

    cheers, shed
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  2. #2
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    Default

    You sure it's a capacitor


    Sent from my iPhone using Tapatalk

  3. #3
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    Default

    Quote Originally Posted by azzrock View Post
    You sure it's a capacitor


    Sent from my iPhone using Tapatalk
    Well I did think it was...... I just googled it, https://www.highpowersemiconductors....-z21l221-220v/ it must be there to stop the back EMF when the coil is switched off.

  4. #4
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    Em . I'm no sparky but I have a feeling that that thing is to do with voltage spikes that can be a result of a dc coil.
    I think is something similor to that whole calapsing field thingy.
    Some times a diod is used for this aswell
    Aaron

  5. #5
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    Default

    What do you think of your master 2500? I thought they had foot brake.
    Do you start and stop via a lever on the apron.

  6. #6
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    Quote Originally Posted by azzrock View Post
    What do you think of your master 2500?
    I haven't used it yet, I bought it recently and it needed some time cleaning it up.


    Quote Originally Posted by azzrock View Post
    I thought they had foot brake.
    I guess mine is a later model, I would prefer the foot brake.

    Quote Originally Posted by azzrock View Post
    Do you start and stop via a lever on the apron.
    yup

  7. #7
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    Default I know i't probably a bit late but...

    Quote Originally Posted by shedhappens View Post
    G/day all, I have a colchester master 2500 and would like the electro brake to engage a bit quicker, it takes about 1 to 1 1/2 seconds after the clutch lever is thrown into neutral before the brake hits the skids and I can see problems ahead.

    It might not sound like an issue but when you want to stop NOW !!!!!! it doesn't............

    With this lathe when the clutch is engaged and the spindle/chuck is turning power is applied to the brake coil to hold the brake in the disengaged position, when the clutch lever is thrown into neutral power to the coil is switched off , supposedly, and about 1 to 1 1/2 seconds later the brake clicks as the spring pressure applies the brake.

    I wouldn't have thought that the capacitor attached to the brake coil wires would hold the brake coil energized for that length of time? The capacitor doesn't appear to be on the schematic so maybe it is the culprit and should not be there ?????

    The brake coil operates on about 120 v dc and has 252 ohms resistance. I can't see any other capacitors or timers.

    3KIM is the brake contactor.


    So what I would like to know is how can I speed this brake application up?

    cheers, shed
    I know probably a bit behind in the times for a post (2017)... but have just bought a master, and having the same issues, re speed of braking.

    Did you sort the problem? I am an elec eng... and cannot see why the delay in the brake (mine behaves exactly as yours) unless it is somehow mechanical... but the delay (as you quite rightly mention 1...1 1/5 sec) is very consistent, across all speeds... the "pull up time" only being effected by (what would appear to be) the set spindle speed?

    The 'capacitor' you mentioned, is actually a "varistor"... common control item to overcome "transient spikes" such as with DC braking circuits! Stops the collapsing coil voltage stuffing up the bridge rectifier.

    Nothing in the circuit I can see can (or would) cause this delay. I am about to attack mine over the next few days to "re-invent" the wheel and make it behave better... and hopefully find out why the delay... as i would like it to "plug brake" also. I cut a lot of threads to 'the shoulder' (mainly plunge cut...yeh i know I'm lazy)... so would like same to work as I think (and would appear you do), stop the thing quickly?

    let me know if you still require anything further... happy to help (especially on the electrical side)!

    Steve...

  8. #8
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    Quote Originally Posted by compind View Post
    I know probably a bit behind in the times for a post (2017)... but have just bought a master, and having the same issues, re speed of braking.

    Did you sort the problem? I am an elec eng... and cannot see why the delay in the brake (mine behaves exactly as yours) unless it is somehow mechanical... but the delay (as you quite rightly mention 1...1 1/5 sec) is very consistent, across all speeds... the "pull up time" only being effected by (what would appear to be) the set spindle speed?

    The 'capacitor' you mentioned, is actually a "varistor"... common control item to overcome "transient spikes" such as with DC braking circuits! Stops the collapsing coil voltage stuffing up the bridge rectifier.

    Nothing in the circuit I can see can (or would) cause this delay. I am about to attack mine over the next few days to "re-invent" the wheel and make it behave better... and hopefully find out why the delay... as i would like it to "plug brake" also. I cut a lot of threads to 'the shoulder' (mainly plunge cut...yeh i know I'm lazy)... so would like same to work as I think (and would appear you do), stop the thing quickly?

    let me know if you still require anything further... happy to help (especially on the electrical side)!

    Steve...

    Hi Steve, welcome to the forum.
    No I did not persist with it, I sold that lathe and bought a larger lathe and fitted a VFD and brake resistor.
    Not that the brake resistor works tho, the braking unit in the VFD is faulty and the EBAY seller won't talk to me.
    But it stops much quicker than the 2500 at low a frequency and it just made the lathe so much nicer to use, with the
    VFD you can have any RPM between any gear ratio and even dial back the RPM as you get close to your feed stop point.
    Sorry that I can't help you but I sure would be interested in what you find and how you fix it.
    cheers, shed

  9. #9
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    Quote Originally Posted by shedhappens View Post
    Hi Steve, welcome to the forum.
    No I did not persist with it, I sold that lathe and bought a larger lathe and fitted a VFD and brake resistor.
    Not that the brake resistor works tho, the braking unit in the VFD is faulty and the EBAY seller won't talk to me.
    But it stops much quicker than the 2500 at low a frequency and it just made the lathe so much nicer to use, with the
    VFD you can have any RPM between any gear ratio and even dial back the RPM as you get close to your feed stop point.
    Sorry that I can't help you but I sure would be interested in what you find and how you fix it.
    cheers, shed
    No probs... though I might be behind the times with reply.
    Regarding VFD's... good way to go, and have a 10HP one on my big lathe (which i plug brake as you have... but also has foot brake to the motor), and one also on the Anyark mill (fggn bridgeport on steroids). I set the mill up with a plug reverse p/button... so I can power tap with it... best thing I ever done for doing multi tapping jobs! Being in the game i am a bit spoilt and only use the SEW VFD's now, as their tech back up is well worth the extra $, over the chong imports... and just find their programme language is easier to deal with.
    Thanks...Steve

  10. #10
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    Quote Originally Posted by compind View Post
    and one also on the Anyark mill (fggn bridgeport on steroids). I set the mill up with a plug reverse p/button... so I can power tap with it... best thing I ever done for doing multi tapping jobs!
    Thanks...Steve
    I also have a anayak mill, I fitted a powtran sensorless vector drive VFD to it and got rid of the variable drive pulleys.
    I did a thread on it here if you are interested https://metalworkforums.com/f303/t20...ghlight=anayak

  11. #11
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    Quote Originally Posted by shedhappens View Post
    I also have a anayak mill, I fitted a powtran sensorless vector drive VFD to it and got rid of the variable drive pulleys.
    I did a thread on it here if you are interested https://metalworkforums.com/f303/t20...ghlight=anayak

    Thanks for the heads up on the thread (just had a quick look and will "in depth it" tomorrow... time for ZZZZZZZZZZZ). About time I gave my old girl a bit of a birthday as well. Spline and drive (in the cone pulley) getting a bit clunky of late (to many big rose cutters? Like your idea on removal of the pulley/s... mine has the 2 speed motor, driving through stepped cones (which after the SEW VFD went on...just after I bought it) has never had the belts changed...no need. The thing has high/low in the head + 2 speed motor and VFD... don't know where to set the bloody thing some times!!!
    Good bit of kit but... and made me money over the last 10 years or so, doing all sorts of "jobber" work from facing cat manifolds to boring 150 mm holes in 'kidney plates' for spreader bars (weighing in at 300 kg and had to take the weight of em with me die lifter). And still capable of doing nice fine work when required... bloody good machine.

    Fkn small world... I thought I was the ONLY one who had one (an Anyark) usually get met with... "a what?"

    Thanks... made my day!

  12. #12
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    Default

    Quote Originally Posted by shedhappens View Post
    G/day all, I have a Colchester master 2500 and would like the electro brake to engage a bit quicker, it takes about 1 to 1 1/2 seconds after the clutch lever is thrown into neutral before the brake hits the skids and I can see problems ahead.

    It might not sound like an issue but when you want to stop NOW !!!!!! it doesn't............

    With this lathe when the clutch is engaged and the spindle/chuck is turning power is applied to the brake coil to hold the brake in the disengaged position, when the clutch lever is thrown into neutral power to the coil is switched off , supposedly, and about 1 to 1 1/2 seconds later the brake clicks as the spring pressure applies the brake.

    I wouldn't have thought that the capacitor attached to the brake coil wires would hold the brake coil energized for that length of time? The capacitor doesn't appear to be on the schematic so maybe it is the culprit and should not be there ?????

    The brake coil operates on about 120 v DC and has 252 ohms resistance. I can't see any other capacitors or timers.

    3KIM is the brake contactor.

    So what I would like to know is how can I speed this brake application up?

    cheers, shed
    Hi John,

    That black thing, in the first picture, is a varistor, not a capacitor. It is used to absorb the transient voltage spike from the coil. It will have minimal affect on the speed that the coil operates.

    I would check that the metal core in the brake coil isn't magnetised and that the moving surfaces are clean and that there is not any swarf in there.

    A trick that I've used with sluggish solenoids is to put a layer of sellotape on the end of the plunger. It creates a gap just enough to stop them sticking, the other trick is to swap the wires over to demagnetise them. Just operate it a few times and then swap them back.
    Best Regards:
    Baron J.

  13. #13
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    Default

    Welcome to the forum.

  14. #14
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    Quote Originally Posted by BaronJ View Post
    Hi John,

    That black thing, in the first picture, is a varistor, not a capacitor. It is used to absorb the transient voltage spike from the coil. It will have minimal affect on the speed that the coil operates.

    I would check that the metal core in the brake coil isn't magnetised and that the moving surfaces are clean and that there is not any swarf in there.

    A trick that I've used with sluggish solenoids is to put a layer of sellotape on the end of the plunger. It creates a gap just enough to stop them sticking, the other trick is to swap the wires over to demagnetise them. Just operate it a few times and then swap them back.
    Thanks John, I no longer have that lathe. I did have the clutch off and inspected it and repaired an oil leak. Good idea to swap the wires, maybe Steve can try that first?

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