Buying Colchester Student 1800 Lathe with start issues (electronic and mechanical) UK
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  1. #1
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    Default Buying Colchester Student 1800 Lathe with start issues (electronic and mechanical) UK

    Hello, am new here, you seem a very knowledgable and helpful bunch! I have owned several lathes going back to the 1970's, mainly Colchester. I am now retired but not tired of 'doing stuff'! Reasonably experienced with 3 phase but not expert with electronics.

    I currently own a Harrison lathe but the tiny diameter of the headstock bore (about 17mm?) spoils it for me. The Colchester is about 42mm through the headstock bore, much more useful.

    A friend of a friend has this lathe, but no room for it. He obtained it from a local collage apparently working. Not having three phase, only a domestic single phase supply he has used a white plastic electronic 'box' to convert his single phase to power the lathe motor. I don't know much about the 'box' except it starts the lathe very gently and stops it even more gently, read several seconds...

    The lathe starts and runs, the gears all work. The clutch disconnect seems to be absent as is the brake (only has constant drive while motor running). I haven't investigated the setup, partly because access is close to impossible with several motorbikes sharing space with the lathe in a very small garage and the fact the seller is being VERY realistic about price. I don't want to spend a lot of time and inconvenience him by investigating the issues, I an not one for spending too much time examining the teeth of gift horses.

    I need to be able to have the motor running constantly, using the clutch and brake to stop and start rotation. Over the last 50 odd years of using lathes I have never run one in reverse, I can't see any reason why I might need to start now, so reverse is not a requirement, indeed it's an unwelcome complication.

    I only have a single phase, 230Volt, 45Amp, domestic supply to my shed, so I either embrace this 'electronic box' or install a new 3Hp single phase motor and starter/contactor. I don't expect to be machining really heavy cuts nor will it be in constant use. My 1Hp Harrison has a reasonably easy life.

    I am expecting to get the lathe home in the next week or so, I am kicking ideas about at the moment but it seems my first task is to figure why the mechanical clutch/brake control is absent and rectify that, then decide whether to stick with the 'electronic box' which may be a zero cost option or replace it with a new single phase motor. I guess I need to know more about the 'electronic box' before making a choice. Soft start and constant running isn't a problem, it's the soft start - soft rundown, which for me at least, on a lathe is unworkable.

    If you got this far, many thanks for reading, comments/suggestions are very welcome. I realise I need to ID the white plastic electronic 'box', that is a priority, obviously.

    Robert

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    I would stick with the VFD
    If you reinstall the clutch and brake the motor will see little start stop cycles
    Then the slow starting is not a problem
    But on a VFD you can adjust this slow start and stop And a lott more
    I would sugjest you read the manual of the VFD (=inverter) and go from there

    Peter

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    Like Peter, I would also stick with the VFD. A read of the manual will allow you to see how versatile they can be.
    With regard to the brake and clutch are these electro-mechanical? and have been deprived of their power supply because the motor is supplied directly from the VFD?
    The electromechanical devices are more likely to require a single phase low voltage supply I would have thought. Or at least unlikely to be 3 phase. This could be provided by supplying the low voltage transformer from an independent 240v supply.

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    Looked it up
    The student 1800 is direct drive So no mecanical or electrical clutch

    The brake needs a powersupply
    Or you put a brakeresistor on the VFD and let that do the braking
    It should be in the manual of the VFD how to connect this resistor and how big

    Peter

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    Thanks Peter,

    That I found hard to believe but I have confirmed what you said. The user manual refers to the ‘clutch’ lever on the apron controls. In fact it seems Colchester only fitted a clutch to the single phase version of which very few were made. The Student as the name suggests was aimed at college and training establishments so not fitting a clutch reduced costs and was acceptable because speed of production was not the essence of the installation.

    Colchester student clutch

    I am going to have to wait until I can get my hands on it and see if I can get the original ‘clutch’ lever to switch the VFD on and off. I may even be able to get it to reverse!

    If I can adjust the ramp up and down so it’s reasonably snappy then I will be a happy camper. No doubt I will get used to starting and stopping the motor.

    Is it possible or acceptable (desirable?) to have a very steep ramp up and down with a VFD? Or is it going to reduce the lifespan of the VFD of the motor?

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    Seapy, you can set the ramp up time to zero, i.e. instantly on, equally the ramp down to zero, in which case the motor coasts to a stop. If you wan the motor to stop rapidly you need to fit a braking resistor which Drives Direct can supply you with.
    Hope this helps. I have the same VFD you link to and it's been in steady use for several years now with no issues at all. In addition I found the people at Drives Direct to be friendly and helpful in setting up the device.

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    Typically prefer to ramp up the manual lathe over 3-5 seconds, no reason to have it instantly go to speed, and also if you forget and leave a chuck key in the chuck it is less likely to impale you on start up. On braking you cannot set the VFD to 0 seconds, it will typically trigger a buss over voltage error because it is trying to dissipate the generated electricity when spinning down. The rate of braking is also dependent on the momentum of the machine, swing a big chuck at high speed, it is going to take longer to brake. Most VFD's have provisions to add an external braking resistor, and this can allow faster stopping by dissipating the excess electrical energy. Realistically you can expect 1-2 second braking with a VFD, you can also program different acceleration and deceleration rates and use the VFD inputs to select them. In addition the Colchester Student 1800 Lathe appears to have a manual foot brake, so you can either use that an have the VFD not apply braking, or use the VFD braking but not both. I wire in the lathe brake switch to issue what is known as a base block (or free run) command to the VFD as well as stop the run command when the foot brake is used. All of this is not a direct connect to the switches, but requires some relays.

    Almost all VFD's have a reverse and a multitude of different programmable functions. It is worth reading the manual, it is not a simple connect the vfd to the machine power cord and have it run.

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    I have tried to find the manual on-line without success as yet, I am sure the seller will have it and hand it over when I collect the lathe. The seller remarked that Drives Direct were very helpful in getting the lathe up and running, apparently there were star - delta issues to contend with.

    From the extremely helpful information you have given me I am confident I will be able to get the lathe up and running in a workable fashion.

    One thing I do wonder about is when I am setting something up in the four jaw chuck, how can I rotate the chuck back and forth as I make the adjustments, there appears not to be a neutral gear position for free rotation of the chuck? Perhaps it will become obvious when I get it going…

    Robert

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    The chuck will turn fine when in gear, it may be a bit more resistance if you are in a low gear. Otherwise you can always shift to a higher speed gear which will offer less resistance and then switch back to a low speed gear as needed. Most small work is done with a collet chuck, something like a 5C or ER40, which they make in a set-tru configuration or some lathes have a 5C collet closure system.

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    I don’t do much with small shafts, one of the reasons why I want a larger lathe is for holding biggish irregular chunks of material in the four jaw chuck. I mentioned photography in my first post, I made myself an Astro mount to hold the camera steady locked onto a star or group of stars, it eliminates star trails with long time exposures.

    My next project is to make a precision slide which moves the camera forward along a rail after each exposure to obtain a perfect depth of focus when photographing flowers. Focus stacking.

    I have a stock of 1” thick magnesium aluminium plate which machines beautifully. I tend to use it for these projects.

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    OK, I have found and downloaded the manual for the VFD, 104 pages, not easy to read on my iPhone!

    It looks like I should be able to get the VFD to do what is required but I suspect programming may be a bit of a challenge for a 74 year old… LOL 😂

    Many thanks for the input this far, much appreciated. You have already saved me a lot of time and effort, at least I now know the desire for a clutch is off the table.

    Robert

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    Colchester generally fitted a clutch as a very expensive option ...I dont see why the simple setup of the shoe brake inside the pulley with a disconnect of the motor wont work single phase .......Incidentally ,I ve been intending to see if a car airconditioning pump clutched pulley wouldnt work..car AC pulls about 3 hp.

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    There are many ways which could be used to add a clutch but I don't really feel like embarking on re-engineering the lathe, I feel sure it can be used as Colchester intended. If for no other reason but that they wouldn't have sold so many Student lathes had the method of operation been unworkable. I would have preferred a clutch but I am more interested in the main capabilities and capacity of the lathe than a detail in the controls.

    I have eMailed with Dave at Direct Drives and he has been very responsive and helpful. He understands exactly what I need and has given me the part numbers and prices of the items I need to restore the original operation of the lathe, including the Forward and Reverse 'CLUTCH' lever with braked deceleration and the original brake pedal as it was intended by Colchester.

    I am just about to build a strong timber sled or frame to sit the lathe on so it can be rollered/dragged out of it's current location onto a trailer, then rollered into my shed.


    Robert

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    The deed is done, lathe now sat in my workshop, top off the gearbox for inspection and an oil change. It appears the holes for a clutch shaft are steady there with blanking plates sealing them off.

    Direct Drives are sending me the parts to utilise the original Colchester micro switches so I can restore the original functionality of the apron ‘clutch’ lever and the foot brake/stop pedal. Together with a resistor to electrically stop the motor quickly. I need to get the adaptation done before I put the lathe into position because it will be difficult to get to the back of the lathe once it’s in position. I can’t afford to waste space in my shed by having the lathe away from the wall.

    One big surprise was the deal included a second ’spare’ motor it turns out the spare motor is a single phase, 3 horsepower motor which looks like it’s good.

    I don’t intend to use it with the Colchester.

    Robert


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