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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: Quick setting nuts
06/05/2020 20:55:07

A different approach to the same problem is used in some old-style calipers (like school pairs of compasses only with points at both ends) - the adjuster thread is gripped by a pair of semicircles with internal threads. These have coned ends one end, and locate into a countersunk thick washer; the other ends pivot loosely within the knurled adjuster knob. This enables rapid setting and resetting over a wide range of sizes - very handy when transferring details from a drawing to real metal.

Cheers, Tim

Thread: Balancing IC engine
06/05/2020 20:42:14

Back in the days when Velocette made motor bicycles, I asked the local dealer about balance. He went to his desk and pulled out a cloth bag sewn up with some nuts and bolts inside. 'Set the crank up on knife edge bearings', he said 'and hang this in the little end. That will save you hours of experiment. This one is for the 500, I have a 350 one too'.

Those really were the days, when you could find a dealer who really knew what he was talking about.

PS Guzzi and Ducati got it nearly right - there remained a rocking couple because the big ends sat side by side. And while the Guzzi was across the frame, the inline Ducati engine went round backwards and so counteracted some of the torque reaction ...

Cheers, Tim

Thread: Stirling Engine Fan
25/04/2020 18:00:50

Chris V says: the bright metal parts appear to my eyes to be nickle plated and I'd prefer them un-plated ...

My experience of modern Nickel plating is that you won't have long to wait. Especially if the atmosphere is moist.

Cheers, Tim

Thread: Pickling brass after silver soldering.
25/04/2020 17:46:20

It may help to know that Hydrogen Peroxide is an oxidising agent. When used as a bleach it is the active oxygen that attacks the stain and the colour. It may well be that this extra oxygen changes the balance so that the more reactive (and more easily attacked) zinc is not attacked in preference to the copper.

A factor which might be helpful to some is that if you leave the pink surface it will darken progressively and take on a patina which can be pleasing. But no good if your main object is to dazzle by the super shiny appearance of polished brass.

It seems, too that most acid solutions will help to remove borax-based fluxes, and will also affect the sufaces of brass, bronze, copper, etc in rather different ways. Experiments with acetic, oxalic, formic, etc on a sample of the actual brass you are using could be helpful.

And in any acid dip, avoid the use of steel tools or welding wire to dip the parts. The iron will amplify the copper-plate effect - just the opposite of what is sought here.

Cheers, Tim

Edited By Tim Stevens on 25/04/2020 17:49:43

Thread: Motor for Chester Champion Mill
13/04/2020 17:13:03

It may also be worthwhile to check the air-flow through the motor. It would not be the first time that a sticky label had come off and was blocking the draft (etc etc)

As the motor is running on DC, it would help to put an ammeter in series with the feed, as this will tell you if the current is no more than the rated max current. On the label above this is 4 amps, and you should get this figure only when working hard. And notice that the label the power is 370W at 220 volts - which will draw about 1.7 amps - and this shows that the motor will not stand 4 amps continuous, only as a max and not for long.

Cheers, Tim

Thread: Grinding rubber
12/04/2020 20:24:30

If the O-ring is a good quality, with no ring of flash around the od, it may well work properly without further attention. And if it lets you down, then you can try grinding.

cheers, Tim

Thread: Roller Bearings
12/04/2020 20:13:42

If the bearing is 'crowded' - ie the rollers contact each other and there is no cage (as implied in the description) - there is a risk that a roller could tip enough to cause problems. How much of a risk depends on all sorts of factors. The A7 is alleged to be capable of 9,000 rpm, but the camshaft only does half that.

And the idea that enthusiasts are dumb and engineers are the ones that get things right is not supported by all the evidence. Tay bridge, for example.

Cheers, Tim

Thread: Which suppliers are open for business?
08/04/2020 18:24:55

In the good old days, pre-WW2, Morris Motors was owned by William Morris. He then bought Wolseley, but kept it as a separate company in his personal ownership. Later he sold what was left of Wolseley to Morris Motors for a tidy sum.

So, it is clear (to me) that although two firms can be owned by the same chap (or several chaps) they still count as separate companies, but it can also be that a firm can become the property of a different firm even if both firms are owned by the same person.

Cheers, Tim

Thread: Guidelines for which steel to use for projects
02/04/2020 15:57:46

The answer is always going to be a compromise, so do bear that in mind. Work out the ideal stuff and you will find that:

the spec was changed 17 years ago

it is not readily available in the size or quantity you want,

but you can order a lorry load

with delivery in about 12 months

and you supply the crane to unload the lorry.

In practice, most model engineering designs are used for such a short time, under such small loads, etc, that unless you are building heart by-pass valves, or intergalactic rocket nozzles, the choice can be reduced to 'what can I get that size this week'.

But if you want a guide with a USA bias, try Machinery's Handbook. Added benefit - all sorts of other questions are also answered.

Cheers, Tim

Thread: Model of an epicyclic gear made by apprentices
02/04/2020 15:42:24

This is not the firm Allen which invented / patented/ introduced the hexagon socket drive and key - is it?


Thread: Problem with LED lights
02/04/2020 15:34:06

I have found that white LED lamps can show up the rusty colouration on steel. I suspect this is because the 'colour balance' of the LEDs is not exactly sunlight. The shine on the metalwork is just the same as it was, of course ...


Thread: Gear Cutting - Pressure angle.
01/04/2020 18:03:41

How few teeth? Well, as the gear gets smaller the shape of each tooth changes - the outside looks much the same but the sloping flanks become closer together. This weakens the tooth - there is simnply less metal there. Smaller still and the teeth can 'interlock' as the gear rotates, making a smooth drive impossible and promoting rapid wear.

It is the same with sprockets for roller chain - anything less than about 20 and you will suffer. Yes, chainsaws do it and that is why the chain and sprocket both need replacing about every tree (well, nearly).

Cheers, Tim

Thread: Inlaying silver in brass.
01/04/2020 17:13:11

PS It is useful, when hammering the wire into place, to do it on a firm solid surface, so the energy goes into the job and doesn't buckle the background. Secondly, don't use a hammer alone - use a punch with a smooth and slightly convex surface - rounded at the edges. A useful punch can be made from a coach bolt with a 'flat' filed in the middle of the dome, and then polished using emery, wet-&-dry, and finally chrome polish. If you can see your face in the surface that is shiny enough. You might need an assistant to hold the work against the support while you tap, tap, tap. Using a punch should avoid making half-moon marks around the surface.

And do a practice run first - copper wire will do for this.

Cheers, Tim

Thread: Digital Vernier gauge
01/04/2020 12:50:51

It might help if you could tell us what type of gauge. Never mind the fact that a digital vernier is a contradiction*, is it a depth gauge, a caliper, an indicator, or what?

* a vernier has two scales sliding against each other, and relies on the user identifying where the scales match. Digital, in this context, means an instrument giving a reading directly in figures, usually relying on an electonic counter and a finely divided internal scale.

Cheers, Tim

Thread: Inlaying silver in brass.
01/04/2020 12:18:27

Inlaying has 'always' been done by cutting a groove and hammering in a wire. Cut the groove so that the edges form a burr, and hammer the burr down onto the edges of a half-round wire. It is not 'engineering' in a modern sense, but it is certainly silvermithing. Gold inlay into silver is done just the same, as was silver into steel for posh armour.

Cheers, Tim
(the last apprentice of the Guild of Handicraft)

Thread: Fine Gauze
20/03/2020 23:04:10

DMB: No - the tubes used as internal tent-poles are made of fibreglass, and so are non-solderable and heat resistant. Just what you need to wrap a tube of gauze around for soldering. I make a distinction between fibreglass - a composite of resin and glass, and glass fibre - which has no resin holding the strands together.

Some types of greenhouse watering systems also use the same sort of fibreglass tubing.

Regards, Tim

Thread: Sanitizer
20/03/2020 15:52:05

No-one has suggested (or have they?) that if alcohol attacks the virus the best approach would be to take the alcohol internally. Single malt virus killer - sounds good to me.


Thread: Fine Gauze
20/03/2020 12:33:18

An alternative tube - unaffected by solder - is fibreglass - as used in the flexible tent poles which are threaded through slots in the tent.

Just a thought


Thread: Ideas to best hold blanks with out turning
17/03/2020 18:31:30

My only comment is about the aluminium backing.

As this is cut, the Al will tend (as it usually does) to stick to the cutting surface, building up a hard lump. This makes this surface a different shape, until the Al eventually drops off and the process starts again. But in the meantime it will cut the brass too, and you might not get teeth which mesh properly. It just seems an odd risk to take when removing burrs from the back of the gear is so simple.

There must be a way to do this without using Al, after all it was not discovered how to extract it until about 1850.

Cheers, Tim

PS: M$ is my favourite thread, too ...

Edited By Tim Stevens on 17/03/2020 18:32:37

Thread: Capillary gaps required for silver soldering.
17/03/2020 17:58:46

A simple experiment might help. Set up two small flat plates of your material upright on your soldering base so that one edge of each plate is touching the other, and there is a very small angle (1 degree) between the plates. Then apply your normal flux, heat the assemblage, and run your hard solder into the joint as you normally would. This will tell you how far into a narrow gap the solder will penetrate.

My money is on 'all the way' but others seem to have alternative ideas.

Regards, Tim

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