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Member postings for Tim Stevens

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

Thread: Metal de-coroder
28/06/2019 15:12:51

The term chelation is used in gardening - it is a good way of supplying chemicals (such as iron) to ericaceous plants (eg heathers and rhododendrons) when they are planted in soils which are not acid enough.

It is also the case that many organic acids serve as reducing agents (ie they reduce ferric iron Fe+++ to Ferrous iron Fe++), and this is much easier to dissolve. Thus ferric oxide (rust) becomes ferrous, and is dissolved by the acid. Ferric compounds tend to be yellow or brown, ferrous tends to be green. A plastic bottle of citric acid which has been used for rust removal will start off green-ish, and after a week or more, will become yellow and pull in the sides of the bottle. This is because the dissolved ferrous iron absorbs oxygen from the air in the bottle, producing ferric iron and lowering the air pressure (as the oxygen is no longer there).

I hope this does not add to the confusion (if any).

Cheers, Tim

Edited By Tim Stevens on 28/06/2019 15:15:57

Thread: Bookpress 5tpi Square thread help please!
21/06/2019 18:31:01

If I were doing this job, I would be happier if the legs of the arch were stayed in some way, ie fixed to the bed so that they remained upright. Just in case anything started to go wrong - it might save a big problem.

Cheers, Tim

Thread: Another Workshop lighting problem
04/06/2019 14:34:42

LEDs are much more efficient at producing light, so LED watts are the makers 'guess' at the light output, and not at all the consumption of power. Usually.

So, you should find that the standard versions offered as tube replacements are a bit brighter - mine are. Just be sure that you choose the colour balance which suits you best - I prefer Daylight or cool white, others tend towards the warm white which is closer to filament-lamp colours.

Cheers, Tim

Thread: Motorcycle 'blipping'...
04/06/2019 14:21:40

In the 'good' old days, many motorcycles were not inclined to tick-over reliably even when new. Especially the cheap two-strokes preferred by beginners. And re-starting the engine was a pain, too. The situation was not improved when amatuer tuning took place, often requiring such sophisticated tools as a coal hammer and a mole wrench. Then the beginner went to a race meeting, and noticed that all the racers did not tick-over at all, but kept blipping their throttles as they warmed up etc (as they had too little flywheel and too much valve overlap). So, a habit turned into a culture.

Cheers, Tim

Thread: Should I have 3 phase supplied to my house?
30/05/2019 18:17:28

There is a big advantage in the speed variation available with a Transwave or similar set-up. It can save a lot of time if you want a very slow drive - perhaps for winding a spring or a coil. And you need to think whether you do need all three devices powered up at the same time. And I see no reason why a device big enough to cope with your most powerful machine should not work OK with the smaller ones. If this sounds a possibility ask your potential supplier for advice regarding switching arrangements etc.

Hope this helps

cheers, Tim

Thread: What is this tool?
30/05/2019 17:54:33

I think the lower object is a rule.

Cheers, Tim

Thread: Practical Electrical Engineer
27/05/2019 15:07:03

I have just acquired 'the Electrical Encyclopedia' - Stubbs - in 4 volumes. It seems to match the style and general ideas of the part-work. It may well be a close relative. I have found reference to a BS 1939, and nothing to hint that they are post war. And I bought vols 1-3 in red, and separately, vol 4 in blue.

And incidentally, I have found two references in them which clarified things -

Chatterton - an insulating compound (Bitumen plus) used on sealing tape. This explains the modern French term for insulating tape, including the vinyl stuff. They took over the word and used it to refer to the tape, not the additive.

Empire Tape - plain strong thin cotton tape used to bind coils when making generator windings etc.

Cheers, Tim

Edited By Tim Stevens on 27/05/2019 15:07:54

Thread: Threading plastics
25/05/2019 12:07:43

Find a length of twine or string the diameter of the gap you need between your turns. Then using the lathe (etc) wind on the twine and the wire side by side. There is no reason to remove the twine before giving a coat of varnish to set things firmly in place - but if you are fussy, be sure the winding ends are held firm before trying to remove the twine.

I have used the same trick for winding springs from stainless steel, using a length of pvc insulated vehicle wire - it makes a proper looking job more quickly than setting up a lead screw etc.

Cheers, Tim

Thread: Oh Dear, I've blown the chop saw...
25/05/2019 11:54:56

Failure could also be due to a mechanical part, such as a bearing or a gear. This will make the rotation stiff or eccentric or both, and can overload the fuse. That was certainly the case with my Aldi angle-grinder, now repaired.

Cheers, Tim

Thread: Childhood diseases
25/05/2019 11:42:04

As my grandma used to say - you will surely eat a peck of dirt before you die, but NOT ALL AT ONCE!


Thread: Getting rid of the garage door...........
25/05/2019 11:36:23

My suggestion would be to find out, before you do much else, the cost of fitting a modern insulated up and over door. This will improve warmth, and security, and still retain the ability to get tooling etc in and out, and would ease any future sale (as it leaves the garage as a shed or an office as well, not instead). And it may be that the cost (and disruption) is less that the cost of building works. There are doors with panels across, and roller systems, so do have a thorough search to meet your needs - and what will work best with any division system you may have in mind.

Cheers, Tim

Thread: A dynamo question: rotation direction?
13/05/2019 17:23:28

Windings correctly connected (using a truly magnetic compass) and away it goes, the right way round.

I still wonder why it motored the wrong way with field coils alternately the right, and the wrong way, round. Ho hum.

Cheers, everyone - helpful as always


12/05/2019 15:55:43

Aha - I think I have discovered my problem - or at least one of my problems. When connecting the coils I fitted the steel centres to each coil, and used a small current and an old plotting compass to check the polarity. Now, though, I have checked again with a new compass, and I have four poles the same way round. All I can imagine is that I am getting old and dafter (true) or the the old compass had lost any magnetism it ever had (quite likely, I think it came from a cracker about 4 moves ago ie 30+ years), and simply was attracted to the first magnetism it saw.

So, I will now reverse the winding connections of two opposite poles and try again.

But this does not answer vthe question fully - it should have declined to rotate altogether, surely?

Robert - I am in Knighton, Mid-Wales, and you are welcome to come if you wish, but give me a day or two to change the connections, re-tape etc, and rebuild, ready for a further test session.

Regards, Tim

PS for Sale - vintage plotting compass, only used by two old ladies to go to church.

12/05/2019 14:29:24

Robert G8RPI: A very helpful (1960s*) summary which is a reminder of stuff I already have at my fingertips. [See latest edition of the Vintage Minor Register newspaper.] So, unless I am missing something, I am no further forward. Thanks, though - the answer ought to be in there somewhere so I conclude that my fault(s) is/are fairly non-standard. Perhaps I have inadvertently fitted two N and then two S coils, rather than NSNS, or even three of one and one of the other. But I don't see how that would give the symptoms I have - so perhaps I have got two things wrong at the same time.

* For interest - I suggest this date for these reasons:
1. only as late as 1960 was the third brush system on the way out:
2. The diagrams show the mainly post-WWII positive earth wiring;
3. The typeface only became generally available in about 1960 - before that it was Times property.

Thanks anyway. If all else fails can I parcel the thing up for you to look at ... no, I thought not

Regards, Tim

12/05/2019 11:52:26

Nimble: Yes, it would but changing the field current direction should change the movement, and it doesn't.

Nicholas: Yes, tried that (along with all the other tricks I know about) - makes no difference.

Trevor J: It is a CAV dynamo - but they were owned by Lucas at about the same time ?1930. My problem is that I have reversed the field connections and it made no difference. I guess that the dynamo number will not be much help as I am not clear how much of it is original, etc. For certain the barrel with the field windings is not the same as the original (but seems identical in appearance, dimensions etc.)

Vintage engineer: They cannot be reversed end to end as the connections won't reach; nor back to front as the curved shape is wrong; nor moved round one place as the slots for the through bolts won't line up. So, I swapped the field connections (which should do the same thing as your suggestions) and it made no difference.

Russel: There was a third brush, but it is not used. The field windings were 'earthed' at the third brush, in effect, but I have connected this end (of the new thinner windings) to the earthed armature brush. And I agree - I can't understand what is happening either.

So - I am going to spend some time with a plotting compass and a low-voltage supply, to see what exactly happens to the field magnetism in various wiring conditions. I'm hoping I don't have to start again with another rewind ...

Regards, Tim

11/05/2019 23:20:11

There is a certain amount of confusion - sorry. I start with a few facts in clarification:

1. The existing field coils were duff, so needed rewinding anyway. Therefore 'Just fit a regulator' does not address the issue.

2. I am not (yet) trying to test whether it generates. I know it motors and I need it to motor in the other sense. Motoring does not rely on a small amount of residual magnetism, as the field coils are energised by the applied voltage. The residual magnetism is only relevant when I test it as a dynamo. And in any event, I have tried flashing and while I did pass current, it made no difference.

3. The reason we have a cut-out on a traditional dynamo circuit is to stop the dynamo, when the engine stops, trying to turn as a motor. It is trying to turn in the direction it normally runs, so I am trying to test my dynamo to see if it will motor - but it does so the wrong way round.

4. Swapping the brush connections won't help in this case as one of the brush holders is earthed, or, more accurately, only one holder is insulated from earth.

5. Swapping the field winding end to end is surely the same effect as swapping the brush connections? This is what I have done and it makes no difference - that is my problem.

6. The problem is not to do with positive or negative earth wiring. A good dynamo will motor in the right direction whichever system is applied (but doing this the 'wrong way round' is likely to set up the residual magnetism the wrong way for charging the 'right way round'[close parenthesis].

So, thanks, everyone for your helpful replies, but we're not there yet.

Regards, Tim


Edited By Tim Stevens on 11/05/2019 23:22:28

Thread: What makes your bristle?
11/05/2019 18:38:47

If there is a problem with tooth goo running down inside the device, would it not make sense to brush your teeth while hanging upside down?


Thread: Honing motor cycle small ends
11/05/2019 17:02:03

Goodness, it was 50 years ago, and I can't see through the fairing ...

But if the bike was used in the TT between 1974 and 1980 I expect I scrutineered it at least once.

Cheers, Tim

11/05/2019 15:12:39

Bending the rod to get it as near as possible was standard practice when I was in the business. Almost my last job at BSA was aligning the little-end on one of the first B50s - then I finished the assembly and put it on the brake.

And if you know anyone who could use a complete Hennan and Froude brake, do let me know. I know of one in the UK which needs a new home for not too much dosh.

Cheers, Tim

Thread: A dynamo question: rotation direction?
11/05/2019 15:02:13

I am restoring a dynamo from an Austin 7 about 1930. The owners needs 12v so I have rewound the 4 field coils with new thinner wire, carefully (I thought) checking the winding directions LRLR. Connect it all up and test with the Field and Output connected together to live, and the body to earth. It motors round as expected, but the wrong way round. So, I rearrange the connections of the field winding set so their current is reversed, leaving the brush connections the same. And once more, it goes the wrong way round. Where am I going wrong?

Conventional shunt dynamo, four field coils, brushes at right angles. No third brush or other complications.

PS: yes, you guessed, this is a follow on from my Empire Tape query for which you were all very helpful - thanks.

Regards, Tim

Edited By Tim Stevens on 11/05/2019 15:03:47

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