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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: PROXXON MICROMOT 50/E
13/01/2016 00:57:39

I've bought proxon stuff from germany as well, saves a fortune. Why are we expected to pay over the odds? I even asked 2 UK suppliers if they were prepared to match the German price, one ignored me, the other was 'brusque'.

It only took a few days to arrive, but you have to change the plug oh dear.

Thread: Interesting ?? ... or hype??
12/01/2016 20:28:23

Duke engine is axial piston, the original link was a variation on the Wankel. As they never managed to get the original Wankel problems sorted out, I doubt we'll see this any time soon. I'd be very wary of their efficiency claims as well. If there really was a lot to be gained from greater expansion ratio all you need do is keep the exhaust valve open after BDC and have a very high nominal compression ratio. More sensible might be an exhaust turbine, shades of Wright compounds, but although the Wright technology has been around for 60+ years it never made it into cars. **LINK** If it is genuinely 18:1 on petrol how do they avoid detonation?

Chap I once worked with had worked on rotary valve petrol engine development. He reckoned that they had a celebration when they got the oil consumption down to less than the petrol consumption. My old Bantam did better than that at 24:1 petroil!

Thread: ER32 Collet Chuck advise please.
10/01/2016 18:54:20

If you go down the morse taper collet route don't overtighten it or you'll have the devil of a job getting it out. Don't ask how I know.

Edited By duncan webster on 10/01/2016 18:54:36

Thread: test bar - between centres
10/01/2016 18:51:26

I've never seen why you'd want a test bar, but here's how I'd make one if I had to.

Get hold of a bit of precision ground mild steel.

face off both ends

hold one end in chuck (only by a short length, say 1/2", support other end in fixed steady and centre drill

reverse and repeat.

 

The steady makes it impossible for the centre to be not concentric to the OD

Edited By duncan webster on 10/01/2016 18:52:32

Thread: 900 year old Triumph
10/01/2016 18:44:56

In the New International Version we find that Joshua's Triumph was heard throughout the land (josh 6:27). Any more biker prophets out there?

Thread: Superheater elements
08/01/2016 22:51:24

Has anyone ever managed to melt a silver soldered one? I've used sifbronze on one and high temp silver solder on another. Not had much use (driving them is soooo boring, and wears them out!) but long enough to identify any problem I think. I know of many other silver soldered ones, no problems. Worst case is steam test, blower hard on, vert hot fire, no steam flow to cool it down.

Thread: Unwanted Taper on Big End Bolts
06/01/2016 15:17:55

No-one has pointed out that 5/16" is 7.94 mm, not 7.6, although I doubt losing the tops off the threads will matter, the shanks will be less good fit in the holes. Of course the originals could be 7.6mm, in which case I'm talking rubbish, not unusual!

Thread: Emco Compact 5 Motor Problem
05/01/2016 20:02:14

Just a thought, are you using slow blow fuses. The motor inrush current could easily blow a quick blow fuse even if there is nothing wrong

Thread: Time for a name change?
05/01/2016 11:55:13

Perhaps we need a section called ' dinosaur engineering' for people who see merit in doing by hand what you can get a machine to do under your instruction. Tubal Cain once did a series on how to build a steam engine without a lathe, using a lot of hand skills. Perhaps those who object to CNC will sell up their lathes, millers etc and just use files, chisels etc. In the meantime, I'll continue to boldly go, even tho' I don't have any CNC stuff I've considered it.

Thread: Unequal box section in brass
05/01/2016 11:48:22

Even if the tanks ran dry, they are not part of the boiler. There is no way they are going to get up to the melting point of solder. Hundreds if not thousands of model locos have soft soldered tanks, and I've never heard of anyone having problems

Thread: 4mm BMS plate
03/01/2016 18:07:15

What's wrong with scale? It means you don't need marking out fluids, and the paint sticks better. It doesn't flake off, it's only very thin.

Thread: The Iron Duke speaks on our behalf, Long live the Duke !
03/01/2016 17:47:32

I echo Michael's concern, this website gives some idea of politicians background

**LINK**

What is even worse is when incompetent MPs deliberately overrule advice from outside experts. When I was once canvassed by an aspiring MP he gave me a copy of his CV to read. He didn't understand when I asked him if he'd ever had a proper job, his experience was all working within the political bubble

Thread: 4mm BMS plate
03/01/2016 17:33:32

I wouldn't even consider using bright plate, it's full of stress caused by the cold working, and is likely to distort as soon as you start shaping it. Use black, which I would get from a local fabricator for a contribution to the tea fund. Even better get it laser cut.

Thread: Lathe tool geometry for threading aluminium
02/01/2016 14:38:53

With an ML7 you can't rotate the topslide far enough to cut down the flank. What you have to do is leave the topslide parallel to the spindle axis, but apply half the feed you've applied to the cross slide to the topslide, so if you advance the cross slide 10 thou, advance the topslide 5 thou. If you don't do this the tool is cutting on both sides, and the swarf from each side collides and just makes a raggy mess. You can also put some rake on the tool as you're only cutting on one face. Then use WD40 as a lubricant.

Thread: Steam Engine Design
01/01/2016 13:02:26

I'm glad someone else has difficulty with Ewins boiler factor, at least it's not just me. However, I have to take issue with Neil on superheating. Most of the heat transfer in a boiler is used up evaporating the water, the heat transferred at higher temperature to superheat the steam is quite small, and has has little effect on potential efficiency. The real reason why superheat improves efficiency is that it massively reduces condensation. Once you have enough superheat to stop condensation there is little thermodynamic gain from more. This all depends on what cut off you are aiming for, shorter cut off gives more temperature drop to the steam, so you need to start with more superheat. Thus with lower boiler pressure on our models than full size, we run at longer cutoff, so less superheat needed.

Compounding reduced the pressure drop, and hence temperature drop, in each cylinder, so reduced condensation. Once superheat came into vogue, compounding of locomotives went out. Even if it gives better indicated efficiency, all that extra gubbins whirling round absorbs extra power.

Edited By duncan webster on 01/01/2016 13:03:06

Thread: Toolmaker builds his own flood defences
30/12/2015 22:43:18

What SillyOodDuffer is missing is that there are a number of people who blame the EEC for everything, even when it has nothing to do with Brussels bureaucrats. What often happens is that Brussels puts something forward which is eminently sensible, and then our Whitehall lot (well qualified in Ancient Greek and Latin etc) gold plate it. I've read a few Brussels directives and Euro Standards in the course of my professional life and not had any problem with them. I do think though that they should keep their noses out of what are purely national issues.

Edited By duncan webster on 30/12/2015 22:44:26

30/12/2015 13:40:13

If we must build on flood plains why not put houses on stilts? Park the car underneath, and then when you get a flood warning just drive to hight ground. Government is in a no win situation. They have been roundly criticised for building flood defences in my home town where it has never flooded in 100 years. Trouble is last week it did, and they haven't finished the work yet.

Thread: Steel vs brick workshop
28/12/2015 17:52:23

When our old pavilion blew up a tree we bought one of these for the Model Engineering Club. http://www.beaverlogcabins.co.uk/clockhouse-log-cabin-5-5-x-4-0m.html

They are available fully insulated, and the price is very reasonable. The only problems are that the walls grow up and down with moisture content, so you've got to be careful when attaching cabling etc to it as it would be ripped apart, and in driving rain water can get in around the window frames, but we are on a very exposed site, and we have a master plan to cure it, just waiting for the round tuits to come. If you're anywhere near the north west come and have a look.

Thread: super relm 100 parts needed
25/12/2015 01:10:32

If you've got all the other bits, get it running and make the leadscrew engagement lever

Thread: Merry Christmas to one and all!
24/12/2015 16:56:05

Someone's got to say it:

Bah Humbug! Scrooge was sadly misjudged

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