Here is a list of all the postings norm norton has made in our forums. Click on a thread name to jump to the thread.
|Thread: VFD drive for a pond pump?|
I want to control the flow from my pond waterfall pump. It is 175w and moves 7,000 l/h. It has an encased 250v winding of some sort that induces rotation in a 4" did iron rotor that has a number of inset copper segments.
Now, I don't understand electric motors in detail but I presume this one rotates at a set speed that is derived from the 50hz supply. I thus assume that the only method of speed control will be to adjust the frequency. If I did this and ran it at, say, 25hz, would it draw less current, which I am hoping it will, or the same as it maintains torque?
I have found pond pump speed controllers for sale but they seem to be triac type that effectively reduce the total current - I can't see that these are suitable for my induction pump.
I would appreciate any thoughts on the subject…..
|Thread: Cable size for Oxford welder|
I respect your care and attention Marcus, but the qualification on thickness of metal is not correct. I have a 150amp commonly supplied, basic MIG welder (Clarke) that runs through a 13amp domestic plug and fuse, and I can fully weld 6mm steel that is butted, vee groove. I have even joined items onto 10mm plate by working from both sides, although probably not a fully penetrating weld. Whether it really delivers 150amps is another matter, but it's called a '150 turbo' !!
Edited By norm norton on 26/07/2016 22:04:15
|Thread: Flying Scotsman's schedule to be kept secret|
The fools are the people with cameras who, unfortunately, have an innate desire to record an event. It is a very natural human response, but one that is best understood and then avoided. Better to just look at the occasion, and around you, to appreciate the sights.
I sympathise with the Darwinian view of the removal of the weakest, but in our modern society it is deemed that the majority must suffer to ensure the protection of the ill-behaved minority.
|Thread: Boiler Paint nightmare|
Sorry, my mistake. I now see that they do several types all under the PJ1 brand.
I looked up that PJ1 out of interest. It is very hight temperature resist (circa 800 degC) and used for motorcycle exhaust pipes. For some reason the manufacturer thinks it unsuitable for engines (car) or radiators. I think it will need a substantial heat cure. The manufacturers recommend three separate cycles with a final one at 340 degC.
Do let us know what the colour and finish is like after it is baked.
Never use a primer under a high temperature paint - it was not designed to cope with the temperature. Remove EVERY TRACE old paint before recoating. Flat the surface with a 200-300 grit and rub with scouring powder (Vim or Ajax) and clean water. This will chemically activate the surface. Any solvent used to clean will leave a microscopic trace of oil.
Always try and use a spray finish, an airbrush is best but a basic aerosol can will work. As John says, many highish temperature enamels for car engines are fine. The problem with some of the wood stove paints is that they come out too grey and flat. Same problem with car exhaust paint.
Buy two or three different aerosols and try them on a old food tin (baked bean or coffee) that has been rubbed down and washed. There will be a difference in the sizes of spray nozzles and you can often swap them over. Practice on the food cans. Three coats is enough, a few hours between coats, first one very thin, final one thicker to ensure full wetting. Leave it 4 or 5 days to dry then light the fire for an hour, gentle blower only, to fully cure it.
Edited By norm norton on 28/04/2016 09:45:17
|Thread: Excentric collet|
Andrew, I fully accept your comments that the ER system was designed for tooling; but that doesn't stop us being creative with our use of our available equipment.
What I don't understand is why a 6mm ER collet is advertised and labelled as 5-6mm, but many of us are finding it only holds accurately at 6mm. Is it because we have bought the cheaper ones? Is the TIR spec applicable over the range 5-6mm, or just at the 6mm nominal size?
I note Neil's comment above that a whole set of his metric collets are "just shocking". Do I now need to buy a full set of PGMS bar to test all my cheap collets, or do I throw them all in the bin and buy a Regofix set?
Interesting subject. I was discussing ER collet errors today with someone at the Spalding Show. I note the comment above by Raymond " the more the collet collapses the worse the runout.."
I have a set of ER25 metric collets, unbranded so they must be from 'budget land', which work OK when the job fits the size of the collet before tightening. If I have to tighten more than 0.5mm on diameter then the runout is worse than gripping in the 3 jaw chuck. It makes a nonsense of the ER system 'adjustability'.
As a result I have purchased some ER25 imperial collets so that when I grip imperial bar material it is reasonably well centred.
Do the expensive/branded metric collets close down better and still offer reasonable concentricity? How much does one have to pay to get 20um at 50mm, with moderate closure onto the work?
Edited By norm norton on 23/04/2016 18:10:49
|Thread: Nitrile ball pushed past its seat|
This infers it is the inlet at the bottom? If the outlet blocks then an axle pump can potentially develop several thousand psi and it will drive a nitrile, or any deformable, ball straight through the inlet ball seat. I also have found one driven inside a copper pipe.
No amount of seat redesign will prevent it happening. The question is how did the outlet became blocked enough to generate the pressure? I would suspect the clack into the boiler.
I have learnt my lesson and use only metal balls in a hydraulic pump. I does not matter if they weep a little bit. It is the clacks into the boiler that need to seal perfectly and here the nitrile balls are most useful, as long as the valve is designed to keep the ball well away from the outlet.
|Thread: New Airship... Here we go again...|
|Thread: Oil viscosity numbers|
I don't think there are any oils that have an increased viscosity as the temperature rises. A 10W-50 behaves like a 10 grade at low temperature, but behaves like a 50 at working temperature. It still gets 'thinner', but not as much as a mono grade oil.
|Thread: Bridge Rectifiers|
Ok, the penny has dropped. The good thing about posing questions is when you think about the answers, and look at the problem again and learn something. My first error was in treating the charger as some kind of dynamo and thinking that its average voltage had to rise above the charging voltage of the battery. The second error was thinking that a resistive load like a bulb would behave like a battery as a test device, whereas a battery behaves like a capacitor. I guess quite a lot of people erroneously think that a 12v battery charger will drive a light bulb at 12v.
I now recall my AC theory from 30 years ago. It is only the tops of the voltage pulses from the rectified AC waveform that flow into the battery, and as soon as you start to charge the battery its voltage will rise to some value, and continue to rise as the plates convert, reaching a maximum when all the conversion has been done.
I have just put the charger on to a small, moderately charged battery that was reading 11.83v: on Hi it read 13.96v and on Lo it read 12.83v. So, yes it is working.
Odd thing is why the previous DVM readings were less than the 1.414 sine wave ratio; either the DVM does not integrate the waveform correctly or the output is not a sine wave?
Thanks again to all and especially john fielding, john swift1 and ajohnw.
Edited By norm norton on 18/03/2016 09:37:10
AC volts across the rectifier AC inputs, no load on the output:
Switch 12v; Switch Hi; AC = 12.9v
Switch 12v; Switch Lo; AC = 11.1v
Switch 6v; Switch Hi; AC = 7.6v
Switch 6v; Switch Lo; AC = 6.5v
I have just had a longish think about what you said a few posts ago. Are you saying that my 'average' 7.3v from a DVM into a resistive load will be pulsing to over 13.6v and thus will charge a lead acid battery?
Now I need the oscilloscope that's in the loft.
Thank you for all the constructive comments, and even a thank you for the off beam comments
I used the diode test setting on one of my DVMs for the first time in my life (!). The new rectifier gave 0.570, 0.574, 0.567 and 0.578 v across the four diodes and OL in the other direction. The old four plate/ five tapping rectifier gave 0.185, 0.330, 0.221 and 0.185 v, and OL in reverse - so I guess that was a germanium one?
So my old rectifier was probably still working and I was wrong to assume it had failed. The assembled charger was connected to a 12v 12w bulb and it lit ok, but when connected to a 12v 60w bulb the overload trip kept triggering. Ah Ha I thought that is the problem, so I bypassed it with a cable. Now the charger will light the 12v 60w lamp, but it was only delivering 3A, and it should be 5A.
So, I put another ammeter in series and confirmed it was only delivering 3A. I put a voltmeter across the lamp and noted the following:
Switch 12v; switch Hi; voltage = 8.8v
Switch 12v; switch Lo; voltage = 7.3v
Switch 6v; switch Hi; voltage = 5.0v
Switch 6v; switch Lo; voltage = 4.1v
The voltages are in the right order but all about 60% of what they should be. Nothing was getting hot or smelly, except the heat sink on the rectifier that was warmish. Unless I have one plug socket in my workshop that delivers 140v AC I can only presume that a winding has failed in the transformer.
I don't really understand how a winding can fail yet I still have circuit continuity and the ability to deliver 3A. Perhaps a winding has blown and shorted to itself, thus reducing the number of turns on the output by 60%, thus reducing the voltage. Have I got that the right way round?
Looks like it will have to go to the great scrapyard in the sky and I will have to buy a new plastic one.
Edited By norm norton on 17/03/2016 17:11:40
Humm, thanks for those thoughts, and for confirming that a 3502 should work. I'm 99% sure the rectifier is wired in correctly as I checked the same diagram as shown above. If it wasn't I would not be seeing 13v surely?
The Hi/Lo switches tappings to the primary on the transformer, and the 6v/12v switches tappings on the secondary and then feeds the rectifier, so perhaps it does switch half to full wave?
I like the suggestion of a dirty/failing switch. All the wires are soldered on (good old seventies construction) so perhaps I will try a jumper lead on the backs of the switches tomorrow and see if I can get more amps to come out. Just be careful of the switched 250v input.
It has got a reverse connection protection device with a resettable button on the output - I suppose that could be putting some resistance in the line?
I think I will put a 60w bulb across the output and see just what gets hot in the circuit after several minutes, and that will be the failing part.
I have a favorite, old battery charger that dates from the 1970s. It switches between 12v/6v, has a hi/lo setting and delivers up to 8A via an inbuilt ammeter.
But the other day it stopped charging. I have some electronics knowledge, so I put a 12v 12w bulb across the output with a DVM in parallel and reasoned that as I seemed to be getting about half the required voltage perhaps the bridge rectifier had failed on one leg.
I found a KBDC 3502 bridge rectifier on the web that was rated to 35A and 200V. That seemed to have the safety margins so I bought and installed it. But the charger is still not right. I seem to be getting the right volts if I put the output onto a charged battery (voltage rise from 12.5v to 13.4v) but it will not deliver much current. If I put the 12v 12w test bulb across the battery and charger the voltage drops to 12v and only half an amp seems to come from the charger.
So have I got the wrong bridge rectifier and is it not switching fully? rather than a 200v maximum should I have got one with a 50v maximum. I don't understand rectifiers.
I cannot see that there can be another fault with the charger. It is a transformer with switches and wires so either there is a circuit or it is blown, and since I can drive 0.5 amps through a bulb it can't be open circuit anywhere.
Edited By norm norton on 16/03/2016 17:57:52
|Thread: Bridgeport Circuit Questions|
Thanks guys. Yes, I took the bulb out and it is 50v, so that answers that one!
Clive, thanks for confirming there are no other diagrams. I also have some numbered sleeves on cables but they seem only to have been numbered one end (?!) - it was probably done for assembly confirmation I suppose.
I think that the VFD must be outside the cabinet because the fans pull quite a bit of air through them, and up highish away from swarf! I will use the VFD extension/dongle to control the motor but I want to use the Bridgeport front switch box to power up the system, enable me to switch on/off the long drive feed, and I have an emergency stop by my knee to switch off everything. I'll sort it out, it will be fun to wire nicely.
Does anyone know what gives if the long drive motor comes up against a firm stop, or the table lock is on (which has happened once or twice)? I'm assuming there is a slip clutch in the drive motor somewhere, or does it just stall?
Many thanks. I was going to ask if anyone had further circuit diagrams. The WD-153 is for my machine and it is the diagram that is in the available manuals. But, it is basically a circuit logic diagram that sort of helps, but I could really do with something with cable colours and cable number codes.
I am going to fit a new motor with VFD so I want to tidy the cabinet. Remove all the 3 phase, bring in some organised 240v and use the Bridgeport front switch box as additional stop/go for the VFD, and keep the traverse isolator switch.
The problem is that the front switch box harness comes into the cabinet as a bunch of coloured wires, many of them red, merges into the system harness and wires pop out at various places on contactors, etc. I am going to have to take the whole harness apart and draw up my own diagram, then reverse engineer the front switch box to deduce which wires come from which switch. Really it is no more complex than rewiring an old motorcycle so I shouldn't fuss.
During a quick look at it yesterday it seemed that the 6F long feed board used 110v AC single phase power only. I could not immediately see where the 50v pink tapping from the transformer was used?
All doable, but is there any other type of diagram that you are aware of John?
Forgive my ignorance, I could look it up but I will ask, how is a pilot motor wired in? I am guessing it is in parallel and as it has no load, but is spinning, it has the effect of stabilising/damping the Transwave output?
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