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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: Amazing! Too Good to be True?
18/07/2022 18:25:08

The Gap in the HT lead is a known-to-work device. Honest. With some ignition systems, any conductive deposit (eg carbon) on the spark plug insulator can allow a current to flow in the secondary winding of the coil, and this slows down the collapse of the magnetism in the coil, and reduces the spark voltage. Result - misfires.

If you introduce a small gap in the HT line, this current cannot flow, and in consequence the misfiring stops.

But it only works if there is a direct connection with no gaps between the coil and the plug. Some early magnetos had a brush pick-up for the HT, and no gap anywhere else, so the shirt-button trick (or two wood screws point to point in a bit of rubber tube) would work with them. But, all cars since about 1920 have had a spark gap in the distributor (whether magneto or coil). In ordinary coil ignition it is the gap between the end of the rotor arm and the brass connections in the dizzy cap. A long time ago I was at an agricultural show where 'salesmen' were 'proving' their product worked by demonstrating with a pre-war Ford tractor engine. Which, of course, had an early magneto and no gap in the HT leads.

So, if you want to run a car with a WW1 ignition system, this gismo will reduce your misfiring. But so will a shirt button.

Funny old world - Regards, Tim

Thread: turning small square stock
10/07/2022 11:33:05

The collets most commonly used* - E and the size in mm - generally have slots for contraction which are multiples of four. It is likely that you will find an example in which your 3/16 stock will fit, lodged in four of these slots. As long as the stock is accurately square it should locate reliably in such a collet.

Hope this helps - cheers, Tim

* OK, a guess.

06/07/2022 15:46:48

And - at last a chance that someone might listen - NOT SLIPPERY. The last thing we need in our cluttered workshops as we follow an article is the magazine slipping from the bench into a pile of oily swarf on the floor. Ditto when reading in bed what we intend to try tomorrow.

Someone will say 'Oh, it wipes clean' but I remind you it should not get itself dirty.

There is one thing which is better on the example shown - no locomotives to be seen. Makes a welcome change.

Cheers, Tim

Thread: Blacking aluminium
06/07/2022 15:31:36

A couple of comments on the latest from Georgineer and Duncan W:

1. There are likely to be two difficulties with the Anodising recepies - the difficulty, now, of poppping down to Boots for a few ounces of chromic Acid, and then, not knowing what the current density should be. It is easy to measure the current in Amps, but no clue is offered regarding the relevant area. Is (or was) current density measured in Amps per square inch, or per square foot, or some other unit? Sorry, I can't help, here.

2. And yes, a useful reminder that dissolving caustic soda (or potash) in water generates lots of heat, so do it slowly. It is interesting, though, that washing soda shows the opposite effect. Chuck some in your bath (Like we did in the old days) and the water gets colder. Most noticeable if you take a handfull of soda and dip it into the warm bath water. The things we used to do before the internet was invented!

Cheers, Tim

Thread: How to machine out a metal channel by hand?
24/06/2022 16:54:08

Or perhaps find some straight tube with slightly thinner walls to lay in the wood slots? Perhaps brass - which as another option would be easier than steel (and a better bearing surface) to make from flat strip, as long as you get the thickness right first?

Cheers, Tim

Thread: Can a Washer Reduce Friction by Acting as a Bearing?
23/06/2022 18:15:43

Answer = yes, but not always. If the washer surface is nicely flat, and attracts rather than repels lubricant, and is not rubbing on a surface which has a low melting point (such as many thermo-plastics (the clue is in the name), and the environment does not attack the surface leaving abrasive products, the answer is more likely to be yes.

Hope this helps

Cheers, Tim

Thread: Blacking aluminium
22/06/2022 10:32:18

Bazyle asks if 'printer ink' will work here - as you might expect, it all depends.

[A] If you mean ink as used by proper printers in the days following Gutenberg, the black was basically soot - amorphous carbon, in particle form, held together by some sort of usually-water-based glue. So - no.

[B] If you mean 'ink' as used in laser-jet printers it is just a clever powder version of [A], often with magnetic black oxide as well as carbon, and a synthetic resin which becomes sticky when heated. Again - no.

[C] If you mean the liquid ink used in ink-jet printers, then you may have a chance - as the black is a dye (or a mix of dyes) in a water base (with other solvents). Anodising may produce a porous surface which is friendly to the dyes - but there is a risk that the dyes may not all be affected the same way, so you could get a brown or a purple etc. And the result is not going to be waterproof.

[D] modern printer ink used for magazines etc can vary a lot depending on the type of paper, the printing method and speed etc. The results tend to be fairly waterproof. So while this might work, I promise you will spend a long time and get your fingers thoroughly stained as you try to find out.

My suggestion would be to look at the alcohol-based dyes sold to renovate the canvas hoods on elderly motorcars (etc). They are intended to be waterproof and rub-proof, and are dye-based not carbon particles. And - a big advantage - they are sold in small bottles and you won't have a lot of wasted time explaining 'what do you want it for, sonny?'

Cheers, Tim

Thread: De-snagging an SL125
20/06/2022 21:33:09

I can offer guide to 'How quiet the SL125 was when new'.

Back when the bike was new a friend had one, and got it stuck in some very soft ground in Wales. We took perhaps 20 minutes struggling to get it out, and then, as it was put on its side stand om firm ground, there was a cry of astonishment. 'Well I'll be blowed - the jolly little device is still running'.

So yes, it was a really quiet bike at tickover at least, when new.

Cheers, Tim

Thread: Blacking aluminium
18/06/2022 16:30:14

Whether you get black from acid (etc) will depend on what else is in the aluminium you use. And - perhaps just as important - whether the black sticks or rubs off too easily. As Georgineer hints, above. (But Howard is not correct with his Washing soda >> acid suggestion).

And it also depends on the usage, when made. A handrail will not stay black very long, if you rely on the silicon, etc in the alloy.

So, as usual, it all depends - sorry

Cheers, Tim

Thread: More beginner questions
02/06/2022 16:21:03

Confusion indeed. It seems to me that the OP - Speelwerk - makes no mention of the levelling of the lathe, and that perhaps by 'clamping studs' Old Iron meant the studs which clamp the lathe to the bench. So, a different reading offers the likelihood that the lathe is not set up in the 'ready for use' sense as it may not be level or firm at all. This is not the main cause of the nasty turning finish, though.

First, set the lathe up firm and level, and attend to all other adjustments etc. You may find other things which need attention in the process. Then sort out a proper sharp tool of the right angles etc for the job in hand (and this includes knowing what you are turning).

Advice on all these points is there in the literature and from colleagues on this forum, but do try to put the setting-up before the trying out - it will help us to help.

Regards, Tim

Edited By Tim Stevens on 02/06/2022 16:22:37

Thread: Advice on Belt Tensioners
01/06/2022 21:21:35

A couple of thoughts:
A - If you use a tensioner as suggested above by Vic Newey, and it used in compression (pushed to gether) rather than tension, don'have it unscrewed very far. The threads tend to be rather wobbly (cheap mass production) and a sudden collapse is possible.
B - If you add an extra pulley rather than moving the driver and driven apart, use one with the same V profile and add it inside the belt. V-belts don't like being bent the wrong way. Yes, I know Howard says the opposite ...
Arrange it to be held against the belt by a spring, and then speed changes are easy.

Have fun - Tim

Edited By Tim Stevens on 01/06/2022 21:23:56

Thread: Metallurgy of Copper
01/06/2022 17:17:48

If the problem you need to avoid is scale inside the tube, you might make up a bung for each end, and fill the tube with eg nitrogen, or carbon dioxide. Remembering to leave one end not perfectly sealed, to allow for expansion. Then use a blowlamp (etc). Or even try adding eg tissue paper or newspaper in the tube, and this will burn and use up the oxygen quickly.

Scale on the outside can be rubbed off with a brass wire brush, or a kitchen scouring pad (also used to matt a gloss surface).

And yes, old tube does seem to harden on its own - but my experience is with vibrating old engines so not quite 'storage'.

Hope this helps

Cheers, tim

Thread: Unusual Escapement
29/05/2022 17:22:40

Did anyone notice the picture of a clock with the message 'Watch later' ?


Thread: Reinventing Jason's Reinvented Real
28/05/2022 17:51:51

Not wishing to divert the thread, but ... all I'm suggesting is that mathematics, the idea that two and three make five, and four times four is sixteen, etc (an exceedingly big etc) wass true before manking came along with his slide rule and his logarithms, and his decimal system, and his square roots, all of which are inventions based on the bare facts of numbers and how they relate.

Not deep at all - although various of the tricks have been labelled as magic, the work of the devil, and other names from the world of fairy stories. Mostly because of ignorance - but that is no excuse to promote such ideas.

Next week - is Sudoku anything to do with mathematics ... ?

Cheers, Tim

28/05/2022 12:23:12

Can I suggest that mathematics has always been there, and mankind discovered it, played about with it, invented devices to use it, and continues to do so? But, we did not invent it.

Cheers, Tim

Thread: New-style cover finish
20/05/2022 18:05:13

The problem for me is that I keep my MEs and MEWs in piles, in the bottom of the wardrobe, and the slippery covers will not stay in a pile. Much anguish ensues, mainly from the distaff side of the family.

I suppose that the True Model Engineer's Answer would be - Before placing a copy on the pile, take a sheet of wet-&-dry paper and fold it across the shorter dimension, with the abrasive side outwards. Lay this folded sheet on the top of the pile, being careful to place it centrally, and place the latest magazine so that the edges align within a sixteenth of an inch.

But I am minded to say a rude word and cancel my subscription.

regards, Tim

19/05/2022 20:58:09

So, is Keith the only one to have noticed a problem?

Cheers, Tim

19/05/2022 17:57:25

These remarks apply equally to ME and MEW (but the system allows one or the other).

Is everyone entirely happy with the new cover?

I don't want to bias your comments - but I found a problem as I turned the light out in bed, and put the magazine on top of an earlier edition.

looking forward to your comments -
Regards, Tim

Thread: Outdoor Silver Soldering
14/05/2022 18:13:21

There are two major problems likely to arise:

1. The slightest breeze will remove heat very effectively (as discussed above)

2. In sunshine, it is more difficult to judge temperatures. This makes it likely that metals such as brass, bronze, silver, copper, nickel etc will be much nearer their melting point before a noticeable glow appears. And sometimes, above the softening point ...
In addition, the sunlight will conceal any glow at lower temperatures, leading to injury when cool-looking parts are picked up.

regards, Tim

Thread: Ambiguous words
11/05/2022 12:09:50

Has anyone mentioned the use, in police circles, of the word 'intelligence' ?

Regards, Tim

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