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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: BSA drop down centre stand
27/06/2020 20:32:15

I bet (as an ex-BSA emloyee) that the steel was nothing special. And if the design only lasted for a few months, the design wasn't much either. But centre stands were a bit new - Norton had them on the International in 1936, though. (I worked for Norton, too, but later)

Cheers, Tim

Edited By Tim Stevens on 27/06/2020 20:32:55

Thread: Hard Surface on Black Mild Steel?
27/06/2020 15:57:40

I bet Harrisons did not 'make' their cabinets. it is likely that this was a job farmed out to a local firm with bending kit. Perhaps the same firm that made cabinets for lots of firms. And so - likely to use whatever was cheapest.

Cheers, Tim

Thread: Motor reduction speed
27/06/2020 15:16:13

A pair of pulleys with a V belt will give you benefits such as - fairly quiet, not 100% fussy about alignment, needs no lubrication (assuming that any extra shaft runs in ball bearings), with a small-section belt you can use a very small motor pulley and get a big reduction, and the investment can be spread over the next two or three projects as pulleys and belts are always handy to have around.

Cheers, Tim

Thread: What fuses Warco lathe and Chester mill
24/06/2020 18:13:38

Why not ask Chester and Warco? And if they don't respond, or don't know, you might draw a conclusion. My bet is that one of them will respond helpfully ...

And it would help if you specify what the fuse does - is it in the mains plug, or for the lighting system, or what?

Cheers, Tim

Thread: DYMO labels [safe removal] ... what method ?
20/06/2020 18:28:16

There is another trick - just say very clearly as near to the labels as you can 'Im ever so glad those labels are well stuck. Surely they will stay there for ever'

Within a week they will start to peel.

Cheers, Tim

Thread: Number punches
20/06/2020 17:40:11

Adam:

Your press will work OK without impact as long as the material is not hardened (but that might destroy the punch anyway, of course). The problem with two tools together is going to be getting the lengths exactly the same. As well as ensuring no tilt, etc. A good result will need care in either case.

As to sources, you will need to search around, bearing in mind that such punches are (Nowadays) made on automatic engraving machinery, and there may be one or two suppliers meeting the needs of all the dealers.

If you need a specific typeface you might have to learn how to cut punches for yourself. Very satisfying but not a quick process. There is literature on the process in typography libraries.

Regards, Tim

Thread: [Project 6] Machinist's Hammer
07/06/2020 20:59:12

A suggestion for the next one you make:

It can be very helpful if you can feel where the head is - and this is not possible with the shaft left round. A pair of flats on the handle end will enable you to feel that the head is in line with what you are hitting, without needing to look. Wood handles are nicer anyway in cold weather, and are always made oval for exactly this alignment reason.

Cheers, Tim

Edited By Tim Stevens on 07/06/2020 20:59:42

Thread: 10.5mm counterbore - 3.5mm depth in cast iron with a pillar drill
06/06/2020 18:18:35

A column or pillar drill should be fine. Set the speed fairly low. The most important things are to ensure that the tool and the hole are properly in line (or the countersink will be tilted) and the job is held really firm (as the cutting tool may snatch on a corner and fling the part and three of your fingers into next doors garden).

You can collect the borings and use them to show your children what a magnetic field is like.

Cheers, Tim

06/06/2020 16:19:45

it depends on how accurate you need the position, the diameters, and the surface finish. If some or all are less critical it is possible to grind the working end of a conventional twist drill - but you will need to be able to do the grinding - or perhaps find a local engineering firm to do it. If I was to have a go, I would first drill a smaller hole in the cast iron as a pilot for the drill - but of course you may have such a hole in the design anyway. This makes the likely accuracy better as you can gring your 10.5mm drill with an extension of the pilot size, and this will help to hold the drill central while cutting.

The shaping could be done with a lathe, if you soften the drill first - by getting it red hot and leaving it in the ashes to cool slowly. If you start with an old, well used drill bit, there will be much less overhang in the turning and you can hold the bit in a collet on the plain shank. Turn the pilot to a plain round shape - don't worry if there are still traces of the flutes. Then with the drill soft you can file the cutting edges to resemble a milling cutter, making sure that the outer corners remain good and sharp, and really opposite each other. Then heat to redness again, and plunge cutting end first into a large dish of water, stirring it round to maximise the cooling. This will (should) make the cutting end dead hard - and you could try the effect of using it on a sample of your cast iron. As long as the iron is 'grey' - not 'white' and glass-hard because the casting was chilled - this should work. The bottom of the counterbore may not be wonderfully flat, and you will get much better results with a column drill or a mill, than hand held.

It might help to use another standard drill to start the cuts and take off any skin, then use the counterbore to get the depth.

Hope this helps. For mass production you might be better with a properly tempered tool - I'm sure there is a posting here which will explain exactly how. Good luck

Tim

Thread: How to glue plastics
06/06/2020 12:20:02

Some plastics are notoriously difficult to glue reliably. Polythene (= polyethylene) is such a material. If you can arrange a fairly robust mechanical joint, it may help to 'improve' the situation with a Loctite type product. but are you sure your shaft is Polyethylene and not polypropylene or nylon or acetal (etc) ?

Cheers, Tim

Thread: Tooling for a spline
06/06/2020 12:11:01

Do remember that in comparing Morgan prop shafts with your drive shafts, the torque at the shaft is what matters, not the power of the engine. A prop shaft rotates about 4 times* as quickly as a drive shaft, and so is subject to only about 1/4 of the torque to drive the wheels, ie only about 1/2 the toque through one drive shaft.

* depending on the actual ratio of the bevels / worm drive

Cheers, Tim

Thread: How easy is it to make a chain sprocket?
30/05/2020 18:43:46

There is a wide range of sprockets used on motorcycles - some for the transmission, some to drive the camshaft. Cakll in at your local motorcycle shop with an example of the sort of size you need and there may be something off-the-shelf. And there is a man in Mid Wales who will make you any size you like in sxteel or light alloy.

The shape is basically a ring of circles exactly the chain-pitch apart, blended to a radius generated by the arriving or departing roller.

Cheers, Tim

Thread: Model Turbines
30/05/2020 18:31:44

I wonder. A turbocharger uses 'spare' power from exhaust gas to compress gas to 'overfill' the engine cylinders, using a turbine to drive a turbine. There is not much difference between waste exahaust gas and steam - not so hot, wetter, certainly, but in principle one hot gas is much like another. Is there any reason why the exhaust half of a turbocharger should not serve as a turbine to drive a (small) vehicle? A purist would say that this is not proper model engineering, perhaps - but has anyone tried it?

Cheers, Tim

Thread: Single point threading
30/05/2020 18:07:44

Given the need to thread right up to the end of the stud section, and the generous length of the knob section, I would make a properly central hole in the knob, tap it, and screw in a length of studding. This can be stuck in place with eg Loctite, and offers significant advantages -
a) the need to cut a long thread on a thin part is removed,
b) the strength is improved as the thread is rolled and so work hardened, and will not be made of free-cutting steel
c) the thread is smoother and will wear longer,
d) a small stud uses less material than turning most of a bar away.

Other advantages are available

Cheers, Tim

Edited By Tim Stevens on 30/05/2020 18:08:44

Thread: Synthetic and enamel paint explained
30/05/2020 17:55:05

Charles Lipscome has not come across baffling engineering terms? How about 'Imperial' spanners which don't fit the bolts which built the empire, but only those from the USA or post war (and so post empire). And I invite him to consider the brushes in electric motors and the points which used to be used in ignition systyms. Every trade and every profession has them - its partly to keep beginners and outsiders in their place, of course.

Grumpy as usual - Tim

Thread: Stirling Engine Fan
20/05/2020 20:58:44

If your burner was designed to run on meths (ie alcohol) it is not likely to perform properly (unmodified) on paraffin. Alcohol as a fuel needs a lot less air than paraffin, which is why paraffin will produce smoke - incomplete combustion and soot and carbon monoxide in the smoke.

There is no likelihood of a problem from a reaction with residue meths. Parffin is so called because it is fairly inert, chemically (parvum affinitas if my O level latin (failed) is any good).

There are (or were) stoves that would run well on paraffin, for greenhouses etc, or you could perhaps find a pressurised stove (Primus, Optimum, etc) or blowlamp which run very well on parafin with no smoke, but a lot more heat than an 'ordinary sized' Stirling engine can cope with. I think.

Cheers, Tim

Thread: Supplier of Johnson-Matthey Stop-Flo or similar
11/05/2020 21:22:24

I have had success with jewellers rouge - the powder, not the grease-base stick. Mix with water and alcohol, and paint everywhere you don't want solder to run. And of course, rouge is indeed a 'finely ground, chemically inert, and thermally stable powder' - just not white. Which is better? I don't know - but silversmiths tend to have rouge and not tippex.

Cheers, Tim

Thread: Adhesive for rubber sheet?
11/05/2020 14:25:33

Some very helpful responses - many thanks. My 'local flooring contractor' is 30 miles away, sorry, Keith. And F Ball has a wonderful list but nothing in sensible sized (or priced) tins for my application. But I like the look of Sikaflex 252 - and I can get 250g through the post. I suspect it is the stuff I have used in the distant past (and forgot the name) for eg sticking a rear-view mirror on a windscreen. We shall see.

Thanks again, everyone

Regards, Tim

10/05/2020 18:35:08

I need to stick some ribbed rubber sheet to the foot panel of a pre-war motorcar. In the past, I have used 'all purpose' spray adhesive, but the edges tend to curl up after a while. My guess is that this is an effect of plasticiser migration, from the rubber to the glue, softening it, or from the glue to the rubber, causing curling. Perhaps both.

The area is about 300mm x 800mm - so this rules out anaerobics such as Loctite, I think (on price at least). Are any of the modern adhesives better for this job?

I have asked the suppliers of the sheet, but they don't seem to know anything about it except the price ...

Stay alert. The country needs lerts.

Tim

Thread: Correcting a misaligned silver solder joint
10/05/2020 18:26:09

The reason a made joint requires more heat to move it, is because when you solder a joint, you don't need to get the whole joint to melting point (of the solder). You can do one side, turn it over, and re-heat for the other side (etc). When you need to reposition, all the solder needs to be melted before it will move. Not necessarily hotter, just more consistently hot all through.

Cheers, Tim

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