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Member postings for Simon Williams 3

Here is a list of all the postings Simon Williams 3 has made in our forums. Click on a thread name to jump to the thread.

Thread: Locomotive control extension
16/02/2020 13:56:39

Piece of flexy drive out of a brush cutter? (The kind with a droop snoot instead of a bottom gearbox)

Thread: Cenetc 2A Horizontal Arbor
25/01/2020 00:01:53

At your local plumbing supplies or builders merchant, buy an aerosol can of pipe freezer. Empty the whole can over the arbour, concentrating on the inboard end.

Promptly (while the arbor is still cold0 give the (loosened) drawbar a sharp rap on the knuckles with a proper hammer. No point at this stage in using a soft faced hammer, it's got serious. Make sure the drawbar is still engaged with the thread in the tail of the arbour -- you don't want to wreck the thread on the end of the drawbar, that just creates another level of complication.

Hit it like you mean it. A club hammer (2 lbs) might be overdoing it, but we're not playing pat-a-cake here.

Hopefully the little blighter will oblige. If not, rinse and repeat.

Good luck

Simon

Thread: Desoldering how to?
24/01/2020 16:34:00

Solder sucker every time, unless you can spring for a de-soldering station. Never got on with de-solder wick, just can't get the hang of it.

I know nothing about working with SMD, plated through holes are quite fiddly enough. As others have said, best option is to accept that the removing component is scrap, so cut it to bits in situ.

Two tricks you need to know with a sucker, firstly (exactly as Andrew says) use a hot iron and add solder first.

Then put a Hellerman sleeve (butyl sleeve) over the end of the sucker nozzle so it seals to the plated through hole. A bit of silicon tube would be even better, Some sucker have a soft tip and work much much better than the old type with a hard plastic nozzle. Now get the heat in there, suck and get out. There's a knack to the "heat - suck - leave" co-ordination that needs a bit of practice. You definitely need the board clamped in something so it doesn't run away when you press in with the tip of the sucker. Empty the sucker out each stroke.

With plated through holes you usually have to grab the end of the pin with needle pliers and give it a good wriggle to get the last remnant of solder to let go. Soemtimes adding a little bit more solder and having a second go helps.

As Andrew has said, the trick is adding solder (and hence flux) first.

Thread: Senior S Type Vert' mill repair
24/01/2020 09:26:30

Hi Damian - just one last thought about the thrust washer.

I don't think it needs to be anything fancy, as it doesn't carry any thrust in normal service anyway. If the driven pulley floats a bit vertically, it will take up the position imposed upon it by the tension in the drive belts, so the belts run true between the motor pulley and the driven pulley atop the quill. That pulls the driven pulley upwards, taking any load off the "thrust washer" which now sits idly in the gap. Hence the thrust washer is only there to ensure that the cast aluminium pulley can't contact the cast aluminium housing, which would make a horrid noise and introduce debris into those pretty little needle rollers.

So a needle roller thrust bearing under the driven pulley would look nice, but I don't think it'll be of any benefit. Another mark against it is that there is precious little spare length to get the bits in the available space, so my thrust washer had to be as thin as I could sensibly make it.

If you do decide to modify your vertical head and fit roller bearings, do please take piccy's and post them here. I'd love to see how you get on.

HTH, best rgds Simon

23/01/2020 20:00:47

Old Mart - you're quite right to be concerned about the damage to the driven sleeve outer surface from running in its bronze plain bearing. I sat and looked at this for some time before committing to the procedure described above, but decided that I had nothing to lose as making the driven sleeve was beyond me. I can cut short keyways, but this one is the full length of the bore of the driven sleeve, and is about 3 inches long and maybe 1/8 wide. I didn't rate my chances of making a slotter tool to do that.

So I'd read on here of someone using the viscosity of the Loctite to centre two pieces together, and decided to give it a go. The wear on the driven sleeve outer was only a couple of thou, so it worked out fine. I expect I used bearing fit Loctite and left this assembly to set with it sat on its end - all's well that ends well!

As for reducing the OD to clean up the damage - that's not going to happen as the wall thickness over the keyway is tight, if that's the right adjective to use. Not sure it isn't hardened as well. Besides, you'd need to work to commercially available bearing sizes - next size down would be 25 mm dia if such a thing exists, so that means taking 8 thou off the wall thickness.

Rgds to all

Simon

23/01/2020 19:28:01

Hi chaps, from memory I bought two needle rollers with their external sleeves OD 1.625 inches. They were 0.625 ins long each and were a perfectly standard catalogue item at my local bearing factors.

I also bought two matching hardened inner sleeves, the internal diameter of which was (from memory) 1.000 inch. I chose these because that was the outside diameter of the driver sleeve - with the key way up its middle.

All of these proprietary parts came from my local bearing stockist, but they had to be imperial dimensions because the starting point is that the hardened inner sleeve must be a snug fit over the original (damaged) drive sleeve.

I then made a short spacer 1 inch ID by approx 1.3 OD and 0.25 thick which went between the two bearing inner sleeves to space them vertically, and a PTFE washer which was about 2 inches OD which went over the outside of the needle roller outer below the pulley to make sure the pulley and casing couldn't contact each other. This PTFE washer was about 2 mm thick, it had to be slim enough that the bearings were left with some endfloat when the driven pulley was correctly positioned on the drive sleeve. I know PTFE is self lubricating, but I greased this liberally on assembly. I can't remember what ID this washer was, but it was to clear the OD of the inner bearing hardened sleeve.

Now I bored out the original milling machine top casting to accept the OD of the bearing assembly - I wanted it to be a nice snug fit so bored it out to 1.624 as close as I could get it. This stage is shown in the pictures above.

Now I assembled the bits, bearing (no pun intended) in mind that the driven pulley is an interference fit over the drive sleeve and needed heat to expand the bore. The two hardened inner bearing sleeves were loctited onto the damaged outer of the driven sleeve (with the keyway up the middle) with the 0.250 thick spacer between them.

Pop the casting and driven pulley back on top of the milling machine head, and replace the motor, drive belt and anything else I've forgotton, switch on and admire.

I rather fancy that the factory version of this as shown above uses a double row needle roller bearing, but I used two separate bearings with a spacer to get the same result. I didn't know that there was such a thing as a proper factory fitted bearing, I was making it up as I went along.

HTH, hopefully I kept some sketches of the bits I made in my notebook (and I can find them) so if they would help I go looking for them. It's all pretty obvious once you've got the bearings in your hand.

My modification is still going strong 3 years later, it's done quite a bit of work in the interim though I don't use it every day. I'm reluctant to take it to bits to see if it's holding up - it's not making any inappropriate noises so I've left well alone. I'm a sucker for taking this to bits to see how they work - and a devil for not quite getting round to putting them back together.

Best rgds Simon

Edit - The ID of the PTFE washer must have been a shade over 1.00 diameter as it only needs to clear the outside of the original driven sleeve, not the OD of the inner bearing as described above.  My apologies.

Edit 2 - There is a circlip in the bore of the machined top casting to hold the bearing outers down so they can't "walk" upwards under load, and there must have been another 0.25 inch spacer in this bore between the two outer bearings, though I can't for the life of me remember making or fitting it.  I hope I did!

Edited By Simon Williams 3 on 23/01/2020 19:36:25

Edited By Simon Williams 3 on 23/01/2020 19:39:37

Edited By Simon Williams 3 on 23/01/2020 19:41:39

Thread: Centec 2a
19/01/2020 18:35:00
Posted by martin cross 1 on 19/01/2020 14:42:07:
 
is it a LHT or a RHT to undo the locking nut? There are no instructions/manual?
 

I know it's not a lot of help, but I've got both - albeit on a slightly later Automill which is a 2B with knobs on. To be strictly accurate the left hand threaded one is ex Deckel, so maybe they're special, but I would normally expect the nut to be right handed.

I've just had a quick check in the manual for the 2A and it just says undo it, but doesn't give any indication of whether the arbor would be right or left hand thread. It's a pound to a pinch of snuff that the arbor isn't original, so I think you're on your own.

Apologies if you already know this, but be sure to have the outboard bearing in place to support the end of the arbor before swinging on it. After than try lefty-loosey first, if that doesn't work go for the left hand option. I think it's less torture to the machine to give the spanner a good clout with a soft rawhide mallet with the drive in bottom gear than trying to wrestle with it. A bit of gentle warmth probably won't hurt - eg from a paint stripper gun.

Someone will be wincing at the idea to hit against the gears - yes OK but they are gert steel lumps and you'll have to try hard to damage them.

Good luck and do let us know how you get on.

HTH Simon

Edit - my post is now irrelevant, but good luck with it anyway

Edited By Simon Williams 3 on 19/01/2020 18:35:47

Thread: Sound recording
14/01/2020 16:32:13

Difficult to give a definitive answer without knowing more about the application, filming distance, background noise etc. But this is likely a good place to start:

Shotgun Microphone

Not cheap, but they do come up on ebay at about £140 or so. You'll need at least a foam pop screen and very likely a "dead cat" wind sock as well, also a mounting shoe.

If you are anywhere close to West Gloucestershire UK I can lend you one to try. You'll also need the cable to connect bretweeen the microphone output (XLR3 male) to whatever the external microphone input on your camera uses.

If you want to take this any further send me a PM.

 

Rgds Simon

Edit:  If you enter "Shotgun microphone" in the ebay search filed you'll get 800 plus hits.  You need something with a super-cardioid pattern.  Rode, Sony, Sennheiser are all good makes you could trust, but you may need to buy one with an on-board battery as it will be a condenser microphone which needs a power supply.  Your camera may have the facility of "phantom power" which is to power the microphone, but be careful there are two standards for phantom power - P12 and P48.  You need to buy a microphone compatible with whichever phantom power facility your camera uses.  If you want any further help just PM me.

Edited By Simon Williams 3 on 14/01/2020 16:57:44

Thread: VFD Question
10/01/2020 17:48:35

Andrew - you posed a question earlier about when a star-delta starter was appropriate.

I don't remember where I got it from, but my experience is to choose star-delta starting at 7.5 Kw (yes, it's a capital K) or above.

On 400 volts a typical 7.5 Kw motor pulls 14amps full load, so starting current DOL is about 7 times this ie knocking 100 amps. This might be why this is the decider point, as most of the factories I worked in had a 100 amp supply.

If we use a star delta starter the inrush is about three times full load current, so that makes the initial inrush about 42 amps. Second stage inrush is about 2 times full load current so is less arduous.

HTH Simon

Thread: Electric motor ratings
10/01/2020 16:50:26

Andrew and Robert have (rightly) marked my work and found it wanting. Thank you both for your accuracy.

In fairness I was attempting to steer clear of explaining vector arithmetic!

Robert's comment on the upper or lower case k for kilo is interesting. I know he's right, though I (obstinately) disagree with him and quite possibly the rest of the scientific world. I'm old enough to remember the debate over whether kilo should be an upper case character because all the other multipliers are upper case - e.g. Mega, Giga etc. And the lower case qualifiers are all divisors - milli, micro etc. In my opinion the small k for kilo is an anomaly better resolved by accepting the coincidence with an upper case K for Kelvin and allowing the context to resolve the conflict.

The unit of absolute temperature should have been called a Thomson, though maybe that creates a conflict with the multiplier Tera.

Who said SI units were supposed to resolve all this?

Best rgds to all

Simon

Edit - I suppose, on reflection, my usage of the term multipliers and divisors is un-rigorous, as was my initial use of the phrase "reactive power" which is an oxy-moron.  I guess a better term for Mega, Giga etc is "positive exponents", whereas micro etc are negative exponent multipliers.  Ho hum.

Edited By Simon Williams 3 on 10/01/2020 17:07:46

Thread: Biax Power Scraper
09/01/2020 23:45:02

I know it's a bit off the wall, but would you get anywhere with a multitool adapted for the job?

E.g. Makita multi-tool (other makes/sources are available)

I guess it's not a true scraper action, but the price is a bit kinder and maybe the technique could be adjusted?

Any ideas/comments? Has anyone tried one for this application?

Best rgds Simon

Thread: Electric motor ratings
09/01/2020 23:13:32

Let's untangle some of the folklore from the technology here.

Motor as above is plated for 550 watts OUTPUT, ie mechanical power delivered at the motor shaft. It absorbs 5.1 amps times 230 volts = 1.17KVA to achieve this NOT kilowatts. KVA is a measurement of reactive power, not to be confused with real power measured in KW i.e Kilowatts.

This tells us something about the efficiency and the power factor imposed on the supply. Estimate max mechanical efficiency is say 70%, then power factor at full load is approx. 0.67. Power factor of a single phase motor will drop quite noticeably at part load, may get down to 0.3 while the measured line current (now highly reactive) drops only slightly.

Motor will run slightly faster than the quoted full load speed of 1425 rpm at part load, but not much. Estimate 1470 RPM at no load. Motor will never attain synchronous speed (1500 rpm) - it can't - but this slip factor is largely what controls the power factor the motor presents to the supply. This is with the motor running at service speed (duty point on torque/speed curve) in equilibrium with its applied mechanical load. This motor is continuously rated - which might be what the CR stands for - but it would have to be marked as such if not rated for continuous duty .

This motor will take multiples of its 5.1 amps quoted full load current briefly while starting. A typical figure for a three phase motor is that it will take about 7 times full load current in the first few milliseconds after it starts, for how long this continues depends on the Inertia of the motor and its load. But you'd better let it spin up the full speed pretty quickly or outgepouf und smoken mit ze blitzen. Maurice's 'scope traces show this effect and quantifies it nicely.

A single phase motor is even worse to start electrically, so budget on say 9 times full load current as starting inrush, get it over and done with as soon as possible. What makes single phase motors so treacherous is that this starting inrush is likely to be limited as much by the upstream supply impedance as the characteristics of the motor. In other words the supply wiring and contacts are often the limiting factor and are getting hot during the inrush event.

Whether non European manufacturers actually conform to the same standards is anyone's guess - the machine could only be (legitimately) CE marked if they do.

HTH Simon

Thread: Gluing glass
04/01/2020 16:59:42

Thank you both for your expert attention -

Bill, it's going to take ages to dismantle the meter from the instrument and I don't know if I can do so without the complications of co-lateral damage. But I may well face this and take you up on your kind offer thank you. I'll be in touch.

MichaelG as ever thank you for your encyclopaedic knowledge of the internet and the expertise therein. I'm doing my homework even as you read this!

Best rgds Simon

04/01/2020 16:21:56

Good afternoon one and all, and best wishes for a Happy, Heathy and Productive New Year

Some while ago I had a windscreen chip and crack repair done, which included bleeding adhesive into the crack. If the adhesive is clear and has the same refractive index as the glass, then the repair is invisible.

I'd very much like to use the same technology to repair the glass of the VU meter of a vintage portable microphone mixer. Any suggestions what is a suitable potion, and where do I buy it please? Is the UV curing Loctite used for sticking rear view mirrors to windscreens the right sort of stuff?

Best rgds, and as always many thanks in anticipation

Simon

Thread: Precision 10MHz reference Oscillator.
22/12/2019 23:08:05

Impressed? That's not the half of it. What a neat project - congrat's Joseph.

Greetings of the seasoning

Simon

Thread: Machining a 70mm hole in steel
22/12/2019 23:04:36
Posted by petro1head on 22/12/2019 22:08:14:

To be honest not too bothered about the finish for this job but I get your point

Gas Axe. Definitely.

22/12/2019 09:38:05

Gas axe.

No, just allowing my agricultural background to take over.

Depends on how big the 65 mm (which I assume is material thickness) block is, also depends on how accurately you want to keep the hole diameter and surface finish -

First choice - quickest and most accurate - 4 jaw in the lathe, pilot drill, boring bar. First reserve first choice substitute face plate for 4 jaw.

Second choice if the block is too big to swing - milling machine and boring head. Slow and less accurate, or at least less reliably accurate in my hands, than the lathe

Third choice (getting rougher by the minute) pilot drill, holesaw in a mag drill, from both sides. Pushing the limits of the technology, but it'll go.

Fourth choice , yes the gas axe

Fifth choice - sub it out to someone with bigger machinery that I've got

Season's greetings all

Thread: Three phase Variac Internal wiring
15/12/2019 19:36:03

Ah hah, cunning!

How did you calculate the saturation voltage?

Rgds Simon

15/12/2019 18:56:20

Robert - thank you - I think you have confirmed the answer I'd thought. I'm more than slightly bemused how such an item came to be in this country, though the chap who gave it to me did work for a while in Canada. Why would he have brought this great lump home - we may never know. Unfortunately he's asked me to loan it back to him to run some antique 120 volts (American) Christmas lights - I've got to go and see him on Wednesday and break the news that this ain't going to work.

As for the suggestion of a swapsie, that might not be as far fetched as it sounds as I have family in Peterborough. I'll send you a PM and we'll see if we can work something out.

John - my test set up with a filament lamp works perfectly - provided I only put 120 volts on the input terminals. My input voltage comes from the big transformer, the tappings on this are such that I can only try 100, 120 0r 210 volts or stick the mains on it directly. With 120 volts on the input terminals of one section as a single phase auto=transformer I can twiddle the dial and alter the dimness of the lamp completely as one would expect.

I was curious to see if my theory about the saturation of the core leading to loss of control of the self inductance and thus input current met with any approval within the community. I tried it at first on 230 volts input but realised the current was ridiculous, so I'd imagined I'd got a shorted turn. But then I tried it on 120 volts and the current was sensible that scotched that theory. Besides,. all three sections behave the same.

So many thanks for your help, and season's greetings to all.

Simon

15/12/2019 15:12:48

Good afternoon, and thanks for the help so far. Firstly a picture of the whole gismo, just to show it is a three phase unit.

dsc_2149-1.jpg

The transformer right of picture is my "source" - it has a selection of secondary windings which means I can vary (to some extent) the input voltage to the variac under test. The scratty looking desk lamp is just a suitable load, and was diconnected when I was doing the "no load" current draw tests.

Here is a picture of the terminal arrangement for each of the variac elements:

dsc_2150-1.jpg

If you look closely at the solder remnant on the tags, you can see that the original wiring was connected to a tap on the winding, not the top end. Just as John says I thought if I connected to the end of the winding I could apply anything up to 234 volts and bob's yer mother's brother. Not so.

Here's another close up of the terminals for each stage - this time of the middle section so my test wiring isn't obscuring the legend.

dsc_2151-1.jpg

And lastly a better picture of the user interface terminals propped against the chassis -

dsc_2152-1.jpg

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