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Member postings for duncan webster

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

Thread: Old School Drawing Exercises and 2D CAD
03/07/2020 19:19:04

I'm still confused, the only constraints seem to be the 2 ends of the 60 degree construction line, and that fact that 1.5" radius comes into it somewhere. There are still an infinite number of solutions.

03/07/2020 12:59:51

SODs latest:

assuming we are to use 2 arcs, unless both radii are specified there are an infinite number of solutions

Thread: Hand Planer on ebay
02/07/2020 19:58:42

That will put muscles on your muscles!

Thread: Old School Drawing Exercises and 2D CAD
02/07/2020 14:52:32

SOD's divide by 5 problem:

Draw a horizontal line AB 1 unit long. Erect a perpendicular from the right hand B.

Draw another line 5 units long by repeatedly stepping your compass. The set the compass to the length of this new line (5 units). Stick the point into A and swing an arc crossing the perpendicular through B at point C.

Then reset your compass to AB ( 1 unit) and mark off the diagonal line into 5 sections. Drop a perpendicular from each of these new points to AB and you've done it.

 

All sounds a bit long winded, but it can be a useful way of making an odd scale ruler.

 

Edited By duncan webster on 02/07/2020 14:53:24

Thread: Copper boiler plate flanging, or not?
29/06/2020 15:12:40

To amplify Paul Kemp's point on expansion, the innards of a boiler get hotter than the shell, not by a lot, but there nevertheless. Unless this expansion is accommodated high stresses can be built up. This is why full size boiler design codes require 'breathing' space in the flat end surfaces. Making the end plates thicker makes them stiffer. Not a good thing.

Its easy to skim a smokebox tubeplate, less easy to file a backhead but worthwhile as the outer profile will be slightly tapered due to circumferential compression as the plate is formed round the curved profile.

Thread: Coronavirus, advice from ME
29/06/2020 13:39:48

Re smoke rings issue 4642: next time I want some advice on a Model Engineering topic I'll ask the Chief Medical Officer. On the other hand, perhaps Mr Editor should stick to his last

Thread: Stroboscopic effect
28/06/2020 16:25:20

My experience, admittedly only one supplier, is that the actual LEDs are fine, it's the associated switch mode electronics that die

28/06/2020 13:15:17

Sounds dangerous to me!

Thread: Motor reduction speed
27/06/2020 14:36:38

what output speed are you looking for? ETW design (sold by Hemingway) has 90 strokes/min which seems about right. This implies ~30:1 reduction. I have a feeling you'd do better starting with a slower motor

Edited By duncan webster on 27/06/2020 14:39:52

Thread: Mamod safety valve
26/06/2020 17:55:48

There was a series in EIM about safety valves and springs, and many years ago one by Bill Hall in ME. Basically you have to ensure that not only will the spring keep the valve shut until it reaches operating pressure, but it will then open wide enough to release all the steam the boiler can make without allowing the pressure to rise too much. Probably not a big problem with a Mamod boiler.

Thread: Ring rollers
26/06/2020 00:37:52

You can buy a kit from Hemingway for the Geo Thomas design. If you've got access to material, he will sell you just the drawings

Thread: Liquid shim (or similar)
24/06/2020 23:57:45

cut up food or drinks cans make good shims, and free.

Thread: Halifax 524 Headstock
24/06/2020 18:46:50

You could put a lot of work into this and still not have a decent lathe. By the look of the bed the previous owner hasn't used it for a long time. I very much doubt you could machine anything with the headstock not bolted down, and if the damage occurred when he moved it he'd have noticed the bang if nothing else. I'd stick to getting your money back if at all possible. Get advice from Citizen's Advice and make yourself so much a nuisance that he gives you our money back to get rid of you.

Thread: Digital angle gauges
24/06/2020 00:47:30

what's the doody little display?

Thread: Halifax 524 Headstock
23/06/2020 13:26:49

I agree with others, your best plan is to try and get your money back. I've found Citizen's Advice very helpful on similar matters, they dictated a suitably threatening email which stayed within the bounds of the law, but I suspect customer protection doesn't work too well if this was a private sale.

Thread: Model Engineer Beam Engine - 9/16 Brass Ball Bearings
21/06/2020 18:08:39

building on XD's suggestion, a bit of geometry and a spreadsheet will work out the co-ordinates of a 'stepped ball', which can then be smoothed off with a file, just less filing and more likely to get it round. If your lathe is up to it you could do it with form tool, or I'm sure GeoHThomas reckoned that a 9/16" ID hardened pipe made from silver steel and presented to the brass would produce a ball. Never tried it, but the theory is sound

Thread: Bar top "copper". What is it?
19/06/2020 11:15:53

If you have an accurate weighing scale you can measure the density, which will give you some idea. Copper plated steel would be magnetic

Thread: Pesky Government Announcement!
18/06/2020 16:05:56

If like me you're high frequency hearing is rapidly disappearing down the plug, HiFi is a bit of a waste of time (and money). What I need is an inverse Dolby circuit to boost the high frequencies and leave them there. I think this is what my hearing aids do (otherwise known as tin lugs), but most of the time I don't bother with them as if I can see whoever is speaking I can understand (lip reading?). Old films are good because actors back then enunciated, not like modern dramas where they mumble all the time

It's not all bad, in fact I reckon it's a male survival tactic, women tend to have higher pitched voices!

Edited By duncan webster on 18/06/2020 16:07:02

Thread: Wot's this for ? help please
17/06/2020 13:01:43

If they are flanged bearings then if you attempt to apply end load to the one at the pulley end won't it just be pushed out of its housing?

 

Edited By duncan webster on 17/06/2020 13:03:29

Thread: Brexit No Deal - WTO duty on EU machines/tooling?
16/06/2020 16:24:11

My package was delivered by the postie, obviously not used to dealing with such things, so I told him I wasn't paying, and he should send the goods back to sender as he as unable to deliver them and I'd ask for a refund. He just put it down and walked away muttering. You may or may not get away with this!

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