Member postings for john fletcher 1

Fit a 3 phase motor every time, the motors are cheaper to make, simpler in construction, smoother in operation and cheap.Smooth like a V6 to a single cylinder engine. However, why pay through the nose for a package, VFD are very reiable, almost bullet proof.Buy a pre-owned VFD and with the motor,wire it up your self all for about £150 max. There are plenty of information details on how to alter the connections on a 3 phase motor, how to make a remote control station and how to alter the internal VFD programme.Its not at at difficult. If you look on Home Work shop there is a guy who often advertises VFD for sale, contact him, much cheaper than the package job. I was very fortunate,I bought three used VFD, at different times, from an auto jumble sale, all worked. I also bought second hand motors for £10 or £12 each altered the connection, down loaded the info, then made remote control box. It took time but saved a lot of money. My inverters were intended to be mounted within a control panel, so I got a sheet steel box from my usual supplier.I drilled a lot of ventilation holes in the top and bottom, at the top I fixed a piece of mesh and also made 4 spacers,

Using them, I bolted on top over the mesh and holes a piece of sheet steel about 20mm all round wide than the holes and mouted it, a bit like a Chinese Pergoda. The box with the inverter inside is screwed to the wall and I control the lathe,mill or drill via the control boxes, one at a time. My home brew set up has been working for the past 6 or 7 years. I have read about motors over heating when running slow due to the lack of cooling air and for a the first couple of years used to check them, never been a problem.

There was good article in MEW about making digital read out so I copied the ideal. I hope I have convinced you, tried my best.If you need any info send me an email.Ted

I and several of my friends have made Tangental or Diamond lathe tools but have found that when taking large cuts the tool piece has a tendancy to be pushed down. We have tried various screws/bolts to prevent this happening.One might say take more modest cuts,we wonder if some one has a crafty means of tighter clamping. One of us person bought one and I notice there is small protrusion ( little lump sticking out), which I think probably prevents the tool bit sliding down. We are not complaining just attempting to improve things, maybe we are missing some thing.Ted

Back again, I forgot to mention that the ON/OFF as Paul mentioned, these as far as I know, do not have overload protection, they engises a relay. I have emergency stops around my workshop, which can be actuated by either knee or foot.They all wired in series with the stop push, can't have to many.I don't want to lecture you all about electrical safety, but probably one of the most important things which is omitted from workshop wiring is EQUAL POTENTIAL BONDING, all pieces of machinery should be linked via a separate conductor.Don't rely on the earth pin of the 13 amp plug.Our bathroom and kitchen should also have EQB. Under freak conditions one piece of equipment could be alive and not blow a fuse, should you then touch an other piece which is not alive but is at earth potential then current will flow from arm to arm. Its mills that kills and volts that jolts. I am told that arm to arm shock are the ones that is an undertakers delight and I believe it, not trying to test the theory.Ted

I'm certain that in the IEE wiring regulation it is stated that ( I'm not sure of the exact number of mm) there should be a physical gap between contacts. Not so in Mosfets, Thyristors or Triacs circuits. The direction switch should be AFTER the DOL. Sequence of operation, select motor direction of rotation by moving the direction switch to forward or reverse position, then press the GREEN DOL switch start button. As I have previously stated the motor surge current can be up to 8 times full load current and possibly higher depending on the position of the Sine wave at that moment in time. This can be viewed on a CRO should a double beam scope be available or a recording ammeter.Most if not ALL direction of rotation switch contacts will arc when used as OFF/ON switches. I have repaired lots of Dewhirst switch as fitted to the Myford range of lathes for my friends, they were just not durable. Eventually the BELL rang at Myford and they fitted DOL together with direction switch, probably pushed by H&S, the DOL did the switching ON. This is the normal procedure in industry. I think we have all move well away from what was originally an information request.TED

I am not familiar with the current wiring regulations, but pretty certain that an electronic NVR wouldn't comply, as there has to be a definite physical air gap between contacts. Which is not possible with semi conductor devices. Its possible to operate AC relays on DC using the appropriate value series resistor, not without ! Just buy a proper starter, thats the way to go, then you have contacts of the right size and all that goes with it. Relay contact are tiny compared to those on a motor starter and motors take a large intial surge current when starting up to 8 times full load current.Ted

Ray your not the only one who has submitted articles (3 at least) which appear to have gone into the unknown. I'm not wasting my time any more.Ted

Hello Steve, I think this might answer your questions, should you have any other question feel free to contact me.

Here in UK we don’t under normal circumstance ever switch the Neutral, all our lighting circuits are switched lives. All Three phase motor circuits are three phases only, neutral not needed.

Both Poles in single phase motor system are switched, but I’m not sure of your electrical system in Norway, possibly you switch both HOT wires. Maybe a North American/Canada reader might enlighten us all on how they go on. I know they have 120 and 220 for heavier loads.

Les, Phil and Peter are quite right in what they say.

Answering your question in Para. 3. Yes, here in UK we switch both live and neutral in single phase motor circuits. I think you would do the same in Norway on your 220 volt two hot wire system, but not sure.Ted

Para. 4. You don’t need a neutral in a 400 volt three phases motor system. Regarding no volt release, over load protection, these are part and parcel of the normal motor starters, found in run of the mill applications

single phasing, such as home workshops. The other facilities such as single phasing monitoring are only found on the expensive industrial drives

You didn’t say the size of your machine motors, be generous with the cable size. Motors can cause a large voltage drop when starting up together with a large initial current surge, up to 8 times normal running current.

I suggest you consider reconnect the motors in Delta, so that they will run on 220 volt three phase, usually it’s only a matter of moving links around in the terminal box, from the horizontal to vertical positions, not a big job.

For an explanation, draw yourself three coils in a Y, shape. Call one coil V the next U and the third W, each coil must have a start and finish on its windings. The centre part of the Y is where all the start ends are connected ( normally known as the one ends and star point) obviously now the outer must be the two ends, this is where we connect the 400 volt three phase from the electric mains, via switch gear and starter, this now known as STAR connected motor.

So you have V1 & V2, U1&U2, and W1&W2.

Now draw a delta shape, label the coils V, U, and W , start at the bottom left hand side V1, the obviously its top must be V2 which connect to W1, the other end of

W1 is W2 which connects to U1, finally U2 connects to V1.The motor is now 220 volt three phase, connect the 220 volt three phases from the mains supply to the outer points. If you connect your motors as I described above you could control them via inverters then you would have speed control as well.

I also have fitted a VFD to my drilling machine, wired it much the same as Ian above and made a digital read out following an article in MEW.The foot switch is very good especially when drilling thin metal which if not well restrained is liable to rotate in a dangerous manner. I have fitted VFDs to my Super 7 and bench top milling machine all pre owned as the car saleman says, and wired a push switch to give jog usedful when setting up. I also fitted a relay, wired to give no volt release.Never had any problems with motors over heating, I am aware of the reasons for possible over heating and when I first fitted the VFDs I did often check the motors when on slow speed.As I said there was a good article in MEW regarding digital read out using VW car ABS braking sensor which counts the teeth on the lathe bull wheel. I made a 60 slot wheel for the milling machine out of some printed circuit board, it works slightly differently. Regarding the foot switch working like an accelerator, what about a sprung loaded linear slide switch, must look in RS, only one direction though.Got me thinking Ted.

I have the copy of the above article which was published in Engineering in Minature a couple or so years.Very good. I never actually understood how the two gears on the small shaft were linked together, perhaps I've missed something ( a keyway perhaps) when reading the article. I hope Hemingway do a kit, If they do, might just lash out when at Harrogate show.Ted

I've just been attending to a friends motor which has a failed start capacitor, nothing otherwise wrong, with the windings or switch. The working voltage was 260 or so it said on the casing, should be at least 400 volts. But as your motor got very hot, it seem that the centrifugal switch wasn't opening leaving the short time rated start winding in circuit when it should disconnected. These Chinese motors and I think it would be, are quite easy to dismantle, remove fan end cover and the plastic fan, which is pressed onto the shaft, then remove the screws and end shields on the shaft end and there is the start switch. No need to mark the motor end shield as one would with a 4, though bolt British motor. Replacement capacitors are available from RS Farnell and others and should be an AC electrolytic type. I think you ought follow Graeme advice.Ted

Getting back to the top item above and out of interest, why should one change from euro quick fittings to PCL which I am familiar with. Are Euro quick less durable or easily damaged, they seem readily available on ebay. I have bought an Aldi compressor and then saw this item. Your comment will be much appreciated.Ted

Maybe some of the cells are US, but if you have more than one batteries it is easy to swap over a cell or two. The straps can be soldered using a large iron (be quick).Alternatively the drill as some one ealier said be converted to low voltage use, using a power supply. I use ex smoothing iron flex, remove the cell from the battery box, put in place some concrete to act as stabilizer (stop it falling over when not in use) and using a non standard plug, wire up the drill. My home made power supply is actually a 24 volt battery charger transformer and rectifier which was thrown out by a neighbour as the case had rusted away, I fitted an electrolytic capacitor to give a bit of smoothing. The transformer had several tappings so it now is 18 volts output and I run my 14.4 volt drill from it. It doesn't over heat and out of interest I ran the drill for a while on 24 volts with no apparent harm. I have several drills obtained from car boot sales, good enough for home workshop use, All have good gear boxes and chucks for 50p or a £1. After all we are not in business have a go nothing to lose.Ted

Regarding dead Ni-Cad batteries.Open up the case, locate the duff cell with a multi meter. then with the aid of a car battery Zap the duff cell observing polarity, a power supply is not man enough. I connect a lead to the neg of the drill battery pack from the car battery and then flick the car battery pos onto the pos of the duff cell or cells, I have a home made Ni-Cad charger and I carry out the former with the charger connected, and it usually jogs the duff cell back into life, not had many failure pleased to say. I have spare battery on the bench that won't start the car and use it.Oh, forgot to say you will get a bit of sparking going on so be careful not to have any petrol around. Some say they have had a cell blow open so be careful, its never happen to me and I've done quite a few.I don't think I get 100% life back but its worth a try.Ted

From memory,and hope I've have got it correct. Remove both links.

Connect Live to terminal 1 on the Dewhurst switch Neutral to terminal 3. Connect terminal A on the motor to 5, AZ to 7, the other two terminals on the motor to 2 & 6 either way round. The motor might run opposite direction to that shown on the switch, if so exchange 2 & 6. By the way Dewhurst switches a notoriuos for bad arcing contacts,could that be the trouble, they are not designed to be used as ON/OFF switches inspite of them being fitted to Myford lathe.Better get a proper motor starter with Green/ Red push buttons and no volt release. Used the starter as ON/Off and the Dewhurst for direction only. Best of luck and if you need any more help call out. Ted

From memory,and hope I've have got it correct. Remove both links.

Connect Live to terminal 1 on the Dewhurst switch Neutral to terminal 3. Connect terminal A on the motor to 5, AZ to 7, the other two terminals on the motor to 2 & 6 either way round. The motor might run opposite direction to that shown on the switch, if so exchange 2 & 6. By the way Dewhurst switches a notoriuos for bad arcing contacts,could that be the trouble, they are not designed to be used as ON/OFF switches inspite of them being fitted to Myford lathe.Better get a proper motor starter with Green/ Red push buttons and no volt release. Used the starter as ON/Off and the Dewhurst for direction only. Best of luck and if you need any more help call out. Ted

From memory,and hope I've have got it correct. Remove both links.

Connect Live to terminal 1 on the Dewhurst switch Neutral to terminal 3. Connect terminal A on the motor to 5, AZ to 7, the other two terminals on the motor to 2 & 6 either way round. The motor might run opposite direction to that shown on the switch, if so exchange 2 & 6. By the way Dewhurst switches a notoriuos for bad arcing contacts,could that be the trouble, they are not designed to be used as ON/OFF switches inspite of them being fitted to Myford lathe.Better get a proper motor starter with Green/ Red push buttons and no volt release. Used the starter as ON/Off and the Dewhurst for direction only. Best of luck and if you need any more help call out. Ted

I once had a similar super 7, and a couple of gears needed relacing. I got replacement gears from HPC gears in Chestfield, this was their phone number 01246 268080 at that time. I think one of the gears needed bushing or boring not sure. Ted

Regarding Amateur radio enthusiasts and CB, its also plug and play for most and has been for at least 25/30 years, very few construct anything at all. It would be difficult to locate radio faults without a lot of electrical/electronic theory and a god understanding of how a raido works and so it is when working out gear ratios, dividing etc. In UK we ridcule theory much to our national disadvantage, just look at the so called third world ,Korea, China,India and how they are educating their children and the product they have invented and produce. Ever bought a mobile phone and have looked where it was made.

Unless you are having the bed reground why do you need to remove the head stock. Don't repair the unbroken. I have had my Super 7 with PCF and G/box bed reground and as the above reader have said, the screws are very tight. Don't forget they need to be put back just a tight,carefull how you go.Ted

Re 9BA nuts, have you tried EKP or tried Googling 9BA.Ted