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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: Brazing hearth - Extraction
16/01/2019 23:22:17

By the time the hot air reaches the fan it will be well diluted, I'd just use a 6" shower extractor fan and see how it goes.

Edited By duncan webster on 16/01/2019 23:35:55

Thread: Bending copper pipe
16/01/2019 13:45:39

Street elbow as in my link above only has one end swelled out, so it won't foul your bolts

15/01/2019 22:53:22

1" rad on 3/8 pipe is quite tight, have you considered long radius elbow? see **LINK**

Thread: Occasional usage Sand blaster
15/01/2019 22:31:44

Definitely write up required, I want one!

My compressor is not 3hp, Not sure what it is, it came from the tip. Can it work in short bursts from a smaller one with a reservoir

Thread: Use of Colour on Drawings
15/01/2019 16:47:43

I do all my 2D CAD on black background with multi colours, but when I print it off I select monochrome, so it prints black lines on white background. this might not be an option with 3D

Thread: Vertical Boiler Fittings
15/01/2019 00:41:51
Posted by Paul Kemp on 14/01/2019 12:44:11:

........Some American design traction engines also had 'wet bottom' fire boxes to give another surface around the fire! ........

Webb tried this on the LNWR. When he found ice forming on the bit under the fire he realised he was wasting his time.

If you run it with the burner flat out and the safety valve blowing merrily and measure how much water you have to pump in to keep the level constant for a time, you know how much steam it is making and so how big an engine it will run. Allow a big margin for losses!

I would expect the twisted shim down the tubes t help, they are quite big for their length and so hot gas can get up the middle without ever touching the sides. Don't go mad, start with half a turn and it then try increasing the twist to see if it gets better.

More blower means you can burn more gas, but eventually you can have too much and have excess air which cools it all down again. Another set of experiments, but when you have enough air to be able to have the gas full on seems like a good place to stop.

Thread: Piston rings
14/01/2019 13:52:04

Never heard of anyone using o-rings in cast iron, but perhaps I'm just lacking knowledge. Slightest bit of rust would rip the ring. Why not make proper cast iron piston rings? Not terribly difficult, I've done it and I'm not one of the demi-gods of the machining world. Proprietary ones work but tend to be too thick and stiff.

14/01/2019 12:26:34

Are you using gunmetal cylinders or cast iron?

Thread: dxf drawings
13/01/2019 23:41:38

I've just drawn up some bits for laser cutting and sent them off for a quote. The company couldn't read my .dwg and asked for .dxf. I find that there are no less than 16 types of dxf available (on Draftsight) ranging from R12 binary to R2013 ascii. Anyone like to explain the difference and suggest a good general purpose dxf that most people will be able to read/import

Thread: What Did You Do Today 2019
11/01/2019 10:53:55

Joseph, I've puzzled about this for a long time. As soon as you grind even the smallest amount off the end of the drill, it's cutting edge is no longer horizontal. Shouldn't you set it so that after a known cut the edge will be horizontal? Of course that implies knowing the helix angle and they are not all the same. I asked DG Brown the same question once and he replied you should set it as I suggest and that you soon learned by experience how much to set it off horizontal.

Thread: Bronze for bushings
11/01/2019 00:35:17

Just bore it to size. Make a gauge a couple of thou small, when that will go in take very fine cuts until the crankshaft (or whatever) will go in.

Thread: L.A.Van Royen Twist Drills and their Grinding
10/01/2019 20:10:52

Well this link suggests carbon steel is harder than HSS at low temperatures **LINK**

Tubal Cain (the English one, not the American upstart) quotes 850/860 Vickers for a carbon steel lathe tool tip. This link suggests 63 to 65 Rockwell for HSS , which is 775/825 Vickers (see for conversion chart) so not much in it. I often use carbon steel in small boring bars (broken taps reground), but I couldn't be bothered trying to source carbon steel squares when HSS is so readily available and even with gentle treatment will last longer and be less susceptible to drawing the temper whilst being sharpened.

There was an article in ME not too long ago about making turning tools out of old files

Dave, you can lose the sack cloth.

Edited By duncan webster on 10/01/2019 20:11:04

Edited By duncan webster on 10/01/2019 20:13:24

Thread: copper boiler with dents
09/01/2019 23:00:06
Posted by John Olsen on 09/01/2019 20:56:46:

If you want to anneal copper, you don't need to shock cool it. Just bring it up to red heat (Locally around the dent will do) and let it cool naturally. It goes very soft and nice to work.


If it was silver soldered initially it probably won't need softening. It might be worth just pumping it up as it is (with water of course) and seeing if the dent pings out

Thread: Small Milling/Drilling Spindle (again)
09/01/2019 18:25:17

If you go on SKF website they give all relevant mounting dimensions

Thread: Welding wrought iron
09/01/2019 14:50:12
Posted by Ady1 on 30/12/2018 09:19:36:

Too many impurities and no-one knows whats in it to start with

So you can't make anything reliable

Some would be cast iron, some wrought iron, some god knows what

Decent metal is like making a decent soup, you've got to know whats going into it to start with, nice fresh ingredients make good soup

Back in the war if they could have used it it would have been gone in a flash

Spoke to a metallurgist who used to work in the steel industry. According to him you could throw any old scrap, wrought, cast whatever into a furnace as long as it had flux and you got it properly molten. The problem nowadays is 'tramp' metals, ie copper and so on that get mixed in

Thread: London Model Engineering Exhibition - Alexandra Palace
08/01/2019 15:00:06
Posted by Bazyle on 08/01/2019 13:57:20:

Thanks for the show guide link.

Stand GG looks worth a visit, and so conveniently close to the entrance laugh

Not that you're biased!

Thread: Vertical Boiler Fittings
08/01/2019 00:13:00

I'm one of the nutters who used to commune with the clouds. Meths Trangia would boil a pan of water in a lot less than 50 minutes, we'd have got bored and given up long before that. I seem to remember a much bigger flame than you show above, but it's all a long time ago. For day trips a thermos flask was a lot easier.

I have the gas equivalent if you want to borrow it, but buying one might be less than the postage.

Thread: Garage Condensation
07/01/2019 22:41:31

According to **LINK** humid air is lighter than dry air. Makes sense because water vapour is lighter than either oxygen or nitrogen (lower molecular weight). Whatever I think you need vents top and bottom, as the moist air flows out you need to let dry air in. Diagonally opposite would be good. Luxury model would have flaps on the vents so you can close them when you want to heat the room.

There is (or was) a ex RN frigate in a museum in Birkenhead. On one of the dorrs on the bridge it had a notice, 'you can't air condition the whole world, so close the *** door'

Thread: Calling Butch owners
05/01/2019 22:43:21

Could someone who has access to a Butch 5"g loco measure the clearance from the rail to the underside of the motion bracket? I rather like the set up of motion plate for my loco, but the clearance looks small.

Thread: Commercial boilers
05/01/2019 21:40:33

Paul, are you sure that a notarised body is needed? It is many years since I read the relevant documents, but a quick scan at **LINK**
refers to the manufacturer doing all the certification. No doubt the manufacturer can if he wishes use a notarised body, but do our suppliers? I doubt it

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