Member postings for john fletcher 1

I have used for several years a home made speed controller for my battery powered 5" gauge loco. RS components sell for 50p a small printed circuit board which is pre drilled to accept a 555 timer and a few other components.It takes about half an hour to solder all the bits in place, and in one place a cut is needed.The timer is a PWM circuit which controls a pair of Mosfets. A pair of car type relays, when energised or not, determine forward or reverse. Maybe that would be all you need, cheap, easily constructed and works.Ted

Back again Stephen and Adam. RS is an expensive route but good quality,there plenty of direct on line starters and contactor much cheaper. If you obtain a direct on line starter with a 240 volt coil, you can ignor its RED/GREEN buttons and use the ones origally fitted to the lathe,wired as a remote pair. This usually need a piece of 4 core or two twins,I'm including the earth here (4th core). Often the necessary information is attached inside of the starter. But why not fit an inverter and three phase motor, you will never regret it. Regarding the reversing switch, that is some I have rarely used, I hope Santon is more durable than the Dewhirst.Ted

To Adam with his Crabtree circuit breaker( which I think will be a contactor) I don't think Crabtree are still around any more,but it was normal to be able to change over coils in the past. However, in some cases the coils can be modified so that it will operate on 240 volts, by carefully removing about a third of the turns of fine wire. The coils are impregnated with varnish and some need warming otherwise the wire breaks and the end is hard to find. If the coil former is bakalite type material it can be put in warm oven or over the lathe light, becareful with modern plastic as it soon melts and distorts. Measure the coil resistance then remove turns until you have a resistance of 57% of what you had initially. Assemble the contactor and give it a test, a trcky job but it can be done.Ted

To Adam with his Crabtree circuit breaker( which I think will be a contactor) I don't think Crabtree are still around any more,but it was normal to be able to change over coils in the past. However, in some cases the coils can be modified so that it will operate on 240 volts, by carefully removing about a third of the turns of fine wire. The coils are impregnated with varnish and some need warming otherwise the wire breaks and the end is hard to find. If the coil former is bakalite type material it can be put in warm oven or over the lathe light, becareful with modern plastic as it soon melts and distorts. Measure the coil resistance then remove turns until you have a resistance of 57% of what you had initially. Assemble the contactor and give it a test, a trcky job but it can be done.Ted

I am also satified customer, a useful add on to my lathe. I wonder why Myford didn'y fit them to the lathes when they were brand new ? Ted

Out of interest, as some one mentioned 240 or 415 volt coil, I found it quite easy to remove about 40 % of the turns from a 415 volt coil to then use it as a 240 coil. MEN coils are easy to remove and replace.The coil former "hole" is square shape so I made simple wooden mandrel on to which I mounted the 415 volt coil, I run between centres quite slack loose fit NOT UNDER POWER and removed lots of turns about 30%. After a while I rigged up a temporary start/contactor connected it to 240 volts and checked if the moving assembly would pull in as normal.When it does, I taped up the coil and leave it on test for an hour or so. Some coil are mass impregnated, they need to be very hot to loosen the resin, don't put it in the domestic oven. Also its not to difficult to strip out a former and rewind it on the lathe, providing you can souce the right gauge of wire. Ted

Morning all, I have a copy of MEN Motor Control Gear 1964 with all the details and price list, your starter cost 62 shilling and 4 pence in 1964. Actually there is no need to cross link the overload, they will operate OK as they are.Some how electrician have got in their heads that it is necessary to cross link. We carried out tests at work and exploded the mith, but it does no harm. As others have said Auto-Memota series 5 starters have No-Volt release, so you are OK. Also, most of my model engineering friends run their machines via 13 amp socket outlets without any problems. Actually the 13 amp fuse is there to protect the flex and cable, not as many suppose the motor.As Harry said, ensure you maintain the earth (CPC) wire through out and finally enjoy making swarf. Ted

Hello Colin and others. Once you have the motor off the machine why not run it on the bench forward and reverse, that would eliminate the motor.I'm not familiar with your motor or lathe but most of the chinese motors have their centrifugal switch at the shaft end. and are held together with three screws or botls so no problem with re assembly.I think yours will be cap start and cap run. If you have a digital camera take plenty of pictures and mark all wires and their original position/terminal. I have taken apart Axminster motors and seem to think they have an unusual centrifugal switch, could be wrong. One of the motors I fixed had a faulty start capacitor about 70 micro farad,not critical,well thought out and nicely made. I dis-like the advert and comments regarding Chinese motors in the Model Engineer magazine.Ted

Thomas, Esso Nutto 44 is hydraulic fluid so if you go along to an agrigcultural merchants, plant hire firm or ships chandlers you wil get an equivalent. I take along a plastic 1 litre container and get it filled for about £2.50 as do my local friends.I fortunately don't have an oiling problem. I use a cheap die cast oil pump as supplied in a 1960 car tool kit. I ground down the end very slightly to make a better fit onto the nipple and always use a bit of cotton rag across the nipple to form a better seal. The oil in the gun has to be below the cork plunger for it to work , its messy to fill,so i have a container below to catch any dribbles.The gun used to leak when not in use, so I threaded the end and made a cap to fit, the cap together with a bit of rag does the sealing trick. Its parked together with my oil can in a 1 gallon plastic engine oil container with the side cut off. I like the idea of the nipple test rig, you learn some thing every day.I hope you soon get your clutch fixed. Ted

Do NOT in any way interupt the electric supply between your inverter and the motor, as Rob above has said. Why would you want to use a foot switch ? If you do need a foot switch then you should control the INPUT to your inverter via a contactor and wire the foot switch in seried with the contactor stop. Ted

I have an RDM 350 bench top milling machine and plan to fit digital read out. Has any one already done this? Ted

Swarf mostly is correct.What is the reason for not using theON/OFF switch which is shown in photo one.I realise that the switch as shown doesn't give No-volt release, but most grinders have a simple on/off anyway.Ted

Regarding your motor not having resilient mountings.I had the same problem, I took the motor to the car motor factors and bought 2 rubber ring type mountings which fitted over the electric motor end bearings. I had to do a bit of fitting up type of thing.Then I copied the motor to lathe mounting platform as pre Myford, that was about 12 years ago. It certainly quiet things down. I left the original welded on motor plate, it all fitted in OK. The total cost was £2.25 well worth it. If you do make a base don't forget the earth connection, motor to base , base to lathe etc.Ted

I have a RDM 350 milling machine and would like to fit a vertical mounted digital read out, has any one all ready done this,and are there any problems to be over come particularly on the mounting. Also, just in case type of thing, has any one replaced the column bearings.Ted

I'm glad you got your shaper up and running, I wish I had the spacer for one. Very useful machines and you can make your own cutters.OK also about the drilling machine idea.The inverter for my milling machine is mounted on the workshop wall, so I made a control box which easily fits on the machine.The box has For, Rev, speed control and digital read out (from an article in MEW) I now drill a hole, switch off, remove drill, insert taper tap and with very slow speed insert tap for a few revs and finish off in the vice. I regularly tap 2,4and 6 BA never broken a tap. All the threads are square,which is some thing I couldn't do in the past.Ted

Before buying an inverter,consider you already have a 900 rpm motor which now doubt can be reconnected in Delta, why not make up a control box using two banks of capacitors. Both banks are used for starting and then just one for running. The details, values etc are in the late JIM COX's excellent book. EX fluorescent lamp circuit capacitors work well.Ted

Why do people buy a new motor when fitting an inverter as most all three motors are easily altered in the terminal box from star to delta. The motor manufactures usually stick a label under the terminal box lid explaining what to do. The WEG inverter appears to be value for money, and by the way make your own remote if needed. Down load the manual and the details are usually there. The control circuit is low voltage so switches etc can be bought from Maplin, RS, Farnell and other component supplier and the speed pot should be LINEAR.Best of luck Ted

An up/down window motors are very good as they are designed to work in both directions, have low speed with gear box, some wiper motor are not reversable unless you alter the brush postion which is not easy. Also a dog clutch is useful,so that its easy to revert to manual operation when required. Regarding speed control, in MEW Dec/Jan 1992 was a very good circuit diagram together with comprehensive construction details. Ted

If you are a member of a model eng.club chances are that another member will have proper motor starter for sale and will help with the wiring.As stated the reversing switch if NEEDED,should be fitted after the starter.If buying second hand via the net, ensure that the operating coil is wound for 240 volt opperation. A trip to an electrical wholesaler could be useful as you may bump into a friendly electrician who might fix you up on the cheap and also give advice.Be care when running a Myford in reverse as the chuck might wind itself off. Oh, and that switch is not a reversing switch, the lower part is inter changable for a part which is, but I think it will be expensive.Ted

I have copy of the Erskine PCB layout with all the component values, if you send me an email with your address and phone number I will post you a copy and explain a few details. The table motor is a 110 volt DC shunt wound motor and to test it I fixed up a yellow 110 volt power tool transformer and a bridge rectifier, you can see where the 4 wires go inside of the control box. Mark the 4 wires that go to the table motor and disconnect them. Then connect them to the temporary 110 volt supply. One of the faults I have found is the variable (pot) speed controller failure, its an easy job to change.Another fault is a resistor on the board over heater, you can see by the burn marks it should be green ceramic colour,it needs a higher wattage if you have to change it as it might be open circuit. I haven't fixed one for a long time and can't rember other details, but as the day goes on I'll get back to you.Ted