Member postings for Clive Steer

I think it quite difficult to understand the drive requirements of a machine and especially an old one where design data has been lost. As I see it, ignoring the machines capability, the power and torque needed is down to the cutter type and the rate that which material needs to be removed.

Usually machine and spindle rigidity determines how much cutting force can be applied which gives the upper limit to required torque and the rate of material removal determines the cutter speed and therefore power required.

For commercial production you may wish to maximise the capability of the machine but where time is not critical you may wish to operate the machine at say only 10% of its capability.

There is probably a sweet spot for operating machines regarding spindle speed and cutting pressure and a similar one depending on the material being cut and the finish required so a lot of possible permutations.

BLDC motors provide constant torque over their full speed range which is determined by the stator current. The upper current limit and therefore the maximum torque it can provide is determined by resistive copper losses and how well the stator can be cooled and ultimately limited when magnetic saturation occurs. A motor can be subjected to short infrequent overloads determined by the thermal mass of the motor stator and the temperature tolerance of the winding insulation. Again many factors to take into account when choosing a motor which can be made more difficult if you don't know the intended loading or use factors.

A horizontal mill is likely to need low spindle speed and high torque so a 5k rpm BLDC motor will require speed reduction in order to maximise power. If the machines original motor was a common 1400 rpm type it is likely to have this already so maybe this needs to be tweaked to suit.

CS

I have a Jack industrial sewing machine motor fitted to my Pultra which I'm very pleased with. I've checked the internal build quality and also went as far as reverse engineering the circuit to check the design. There are others at lower cost, which I haven't bought as these come directly from China. Whereas when I bought my Jack and Tysew units they came from London and were here the next day.

I also tried a Tysew type which also performed well but the speed setting input was more difficult to convert to a potentiometer driven than the Jack.

I have noticed a worrying trend on eBay that items appear to be sold from a UK address but at the bottom it shows the address as being from China. I prefer UK stocked items, although they may be more expensive, as I know I won't get stung for possible import duty/VAT and collection fees etc

CS

I hadn't made an in-depth investigation into the product before suggesting it may be suitable for driving a machine and I had taken the advert on face value. Robert may have a point about the connectors but a lot of electrical/electronic connectors, although meeting EU/UK Domestic use standards, may not suitable for their final operating environment. I think the connectors Robert has doubts about are the two used to connect the motor to the controller. One will be the Hall signals @ 5V & < 10mA but the other is for the motor phase windings using 3 - 4 Amps @ 300+ volts. The pictures shows a motor similar to the one I have on my Pultra lathe which from personal internal inspection is of good quality and design. Maybe someone in China is noticing how the sewing machine motors are finding alternative application and reacting to the market opportunity.

I can't agree that cheap Chinese = Junk as I remember that Japanese products once had the same reputation. I also remember the design and build "quality" that some British products had.

There are many devices, and not just electrical ones, that are being bought that do not comply with a whole plethora of modern safety standards and these include old high quality British induction motors. These may be a problem if the user/purchaser doesn't understand the possible issues or seek advice and in part that is what this forum is about.

As they say the handbook, if there is one , is for the guidance of wise men and the obedience of fools and if there are still any doubts ASK.

CS

Whilst searching for a suitable brushless DC motor for a friend in the States to fit to his BCA jig borer I came across eBay Item number 225 466 391 205.

This is a motor and servo controller sold as a plug and play system without the hardware associated with the Sewing machine offerings. The motors and matching controllers come in several power rating from 550W to 2.2kw so should suit someone wish to use this technology.

CS

I think an appropriate joke regarding modern programming languages is " How many gigabytes does it need to get a light bulb to work. " I think the answer from the electrician and the IT specialist would be totally different.

CS

For those who prefer fixed speed induction motors I see that there are quite a few being offered on eBay that come from industrial sewing machines at circa £20. The motors have mechanical clutches, a useful feature for a lathe, look to be easily mounted and are rated around 500W . Some being offered are 3 phase so can be used with an inverter.

CS

I had a similar experience with a wind up gramophone my Aunt had. I was so fascinated by it she gave it to me along with a few 78's. It was one of the more compact and portable types so didn't have the huge horn that the dog listened to in the "His Masters Voice" logo. It wasn't very loud and on investigation I found some paper had been stuffed up the horn. I pulled this out and was glad to find that they were plans for balsa and tissue model aircraft which I later constructed. I can't remember what happened to the gramophone but I think my parents "left it behind" in a house move.

I would have liked to see the machine that made the gramophone needles.

CS

Many old AC motors had internal fan driven air ventilation but modern motors do not hence the fins. This is because if there is a severe overload situation or winding failure and the stator winding catches fire this remains contained within the case improving safety. The downside is that although the stator can be conduction cooled the rotor temperature becomes a limiting factor and frequent starting cycles is a frequent cause . The issue here is that heat is conducted from the rotor into the bearings through the shaft. However since the shaft is hot and the outer bearing race is being cooled by the case fins issues with bearing load arise. Unlike plain bushes used on early motors ball races can be lubricated for life so give better reliability especially for motors located where regular maintenance is difficult. Rather like long case clocks nobody thinks they need looking at until they stop. So it is with motors and lathe motors with their frequent stop/start use profile do suffer.

The soft start of a VFD in itself is a worthwhile feature for a lathe without a clutch with the variable speed as a bonus.

BLDC motors with a permanent magnet rotor don't suffer from rotor heating to the same degree that an AC motor does and they don't need as much iron in the stator so are more compact and lighter.

CS

In the beginning there was darkness and then Faraday and Edison gave the world Light. DC was their vision and then Tesla got in on the act and the world became AC mainly because it enabled easier power distribution.

However DC motors are in many ways better than AC and the latest permanent magnet brushless motors are very compact and powerful. An electronic controller for a brushless DC is very similar, electronically, to a VFD for an AC motor so if you want variable speed the cost difference between AC and DC is minimal.

AC motor are best used at a fixed speed with variable load. DC motors can handle variable speed and high load as can be witnessed on a fully loaded Lisbon tram starting on a steep incline.

I'm for BLDC motors every time.

CS

I failed to read an ealier post regarding the relay being a thermal delay device. These are similar to early flashers units for car direction indicators. A heating element is wound around a bimetal strip which forms the contact circuit.

These can fail because the heater goes open circuit as it is on all the time the motor is running or the snap action, if it has one, fails.

CS

I believe the figure 9 circuit shows a circuit where the starting relay has a normally closed contact which connects the starting winding (A2, A1) to the supply and after short time period it operates and disconnects the starter winding allowing the motor to continue running on the main winding Z1, Z2. If the relay fails to operate the starter winding remains powered and the motor rapidly overheats.

The relay is probably an AC type and the delay achieved by a dashpot. If of this type they can become sticky or corroded causing a longer than needed delay or failure to operate.

The delay may also be achieved electronically but I'm not familiar with Cowells electrics. A picture of the relay with thee cover off may resolve this.

CS

Some years ago I fitted a VFD to a Schaublin 70 lathe belonging to Anthony Randall a well known British clockmaker.

He said it transformed the performance of the lathe and particularly when he needed to re-pivot arbors where the lowest speed setting of the Schaublin's standard drive arrangement was too fast and a drill would tend to burnish the arbor rather than bite in.

Early lathes had simple drive systems because of cost as variable speed motor systems where expensive unlike modern BLDC motors or 3 phase with VFD. One lathe I had for a short time had a Ward-Leonard system where a 3 phase AC motor drove a DC generator driving the lathe's DC motor. Quite a sight to see but oh so heavy. I sold the lathe on after refurbishment and would have loved to have retained the original drive system but it needed a 3 phase supply and not many electricians would have been able to repair it if it had gone wrong. So I used the 3 phase motor to drive the lathe directly and fitted a VFD so it could be powered from domestic 240v supply.

I would advise anyone with a lathe/mill/drill to find some with a machine fitted with variable speed drive and try it. They won't be disappointed.

CS

The only trouble with rock wool is that it acts like a sponge if there is any water leak and it won't dry out due restricted air movement so can build up over time without being noticed.

Although not ideal polystyrene is better in this respect and can possibly be done for nothing by collecting sheets or even fragments of PS packaging that can often be found in builders skips. The downside of PS is it is combustible but since a workshop, except in the distant past, is rarely slept in then no problem.

It is amazing what is offered for free on Freecycle sometimes including building materials as some traders would rather give away materials they can't use rather than have to pay for the disposal of trade waste.

CS

As I understand it water and sewerage companies legally have to provide water and sewerage for new developments but what they say they can provide and what they can actually provide are not necessarily the same.

If a council rejects a planning application because they believe that utilities can't be provided the developer just goes to appeal and often the council decision is overruled.

Although sewerage is one issue there are also shortfalls in roads, rail, doctors, hospitals etc that aren't being matched to the housebuilding. Down our way we have just been released from a hosepipe ban, not because our reservoirs are empty but because they can't treat the water needed or have sufficient pumping capacity to deliver it to the full network possibly because of leaks.

CS

The numerous sewerage spills that have been reported are mainly caused by the sewerage system having to handle both surface water and sewerage so when a storm occurs the system is easily overloaded. Have a fairly vague piece of legislation or possibly only guide lines allowing releases in exceptional circumstances doesn't compel the treatment companies to improve or invest in their infrastructure. So we have got we have got and it may get to a point where it can't be fixed.

CS

I think there is a certain amount of hype about all the "alternative" sources of energy. For instance heat pumps are being hailed as the saviour and efficiencies of 300% are being quoted. However these are the best and actuals may be less when outside air temp is low and may reduce to zero if OAT is very low. The downside of this is that just when you need heat it can't supply it. There are also difficulties heating to the 40C needed for our style of wet convection radiator systems. Better efficiency may be obtained if convection radiators are "blown" or hot air used directly. However the biggest problem is that a large proportion of our housing stock has poor thermal performance which can be very costly to improve. I'm not sure that even modern houses are built to the best thermal performance achievable at moderate cost so these properties will become too costly in the future. If we all move to heat pumps plus electric cars our Grid will have to double or even triple in capacity.

The plan is a good idea but we should have started it 50 years ago!

CS

The Scientific Instrument Research Association that was located in Chislehurst developed an optical transfer function instrument back in the 60's. I was shown this when I went for a job interview there and later in the late 70's met an engineer who had worked on it.

CS

I have a Pultra 1770 to which I have fitted one of the Brushless DC motors, with its electronic speed controller, that are being sold on embay for as little as £83. These are sold as upgrades for Industrial sewing machines as a virtually plug and play unit. The motors are about 4 inch cube and rated at 3/4 HP. This may sound excessive but the physical size makes it very attractive and you don't have to use the power. The main advantage they have is variable speed and phenomenal torque so no need for belt/pulley changing so you could dispense with the countershaft.

In my case the motor and controller are compact enough for it to all be fitted to the lathe base (see my pictures).

There are other smaller BLDC motors and controllers that work from 24V but these are far more expensive and certainly not plug and play.

CS

Hi Steve.

My "sensitive drill" was actually designed for tapping but I can find no info regarding the manufacturer. I'll post some pictures to see if anyone can identify it.

I'm currently putting together the BLDC motor system to drive it.

In my case I chose the ER11 spindle with 12mm x 150 mm shaft as it was an almost exact match for the original. I say almost because the original spindle was strangely 11.86mm diameter so hence the need to rebush. Most of the other parts on the "drill" appear to be metric so I believe it may be Swiss or German. As a tapping device it would not need to be run at high RPM so plain bushes would be fine.

CS

Steve

The elegance of the tube system is you make the tubes and spacers all the same length at first and then shave a thou or two off one to get the correct pre-load. The thin spacers between the front two bearings are a bit more tricky to do but you can super glue them to a face plate and skim. Final gapping can be done by "stoning" on say a diamond lap. The pre-load is determined by the difference in length rather than the absolute length so much easier to measure accurately with feeler gauges. The tubes can have fairly thick walls which improves the cartridge and spindle rigidity. Also their inner and outer diameters don't have to be that accurate. You can make one long tube and then part off the thinner spacers and only the face that the parting tool created needs to be trued up.

I'm not sure that given the ER 8 collets and the small cutter/drill you are expecting to use whether you need two bearings at the front.

I've just upgrade a sensitive vertical drill by using a bought spindle with ER11 collets. The spindle is a straight 12mm diameter X 150 mm long and in my case runs in oilite bushes. I don't know if similar spindle are available for ER8 but it would save a lot of work.

The Leinen system used special bearings which had to be assembled in the correct orientation so on reflection the spacing tubes were probably equal length.

CS