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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: Screw cutting is over complicated
15/09/2019 23:47:09

I've been banging this drum for years, but I put half the cut on the top slide, which generates an included angle of 53 degrees, so you get a light scrape down the right hand flank

Thread: Black Bar
15/09/2019 00:18:38
Posted by John MC on 14/09/2019 18:02:50:

My preference is to always go for black bar if it's available in the grade of steel I want to purchase. Two reasons, its usually cheaper than bright drawn, also less prone to distortion during machining.

If steel is sold as EN3, black or cold drawn it will be EN3. All "new" steel will contain recycled steel, steel being one of the most recycled materials.


And a lot of cast iron is made from steel scrap by adding carbon. The reason I think is you know what you are starting with, so you have a chance of knowing what you finish with.

Thread: The Workshop Progress Thread 2019
12/09/2019 15:14:58

Today I finished the latest batch of signals, and I'm hoping it's the last. This makes 13 I've made, but it does add to the enjoyment of driving little puffers, and helps to avoid running up the back of the train in front when he has run out of chuff just round a blind bend.

Next step AWS to tell the drivers to stop messing with the fire and look at the signals!

img_3673 (small).jpg

img_3683 (small).jpg

Edited By duncan webster on 12/09/2019 15:15:27

Thread: Vickers Bl 8 inch Howitzer cannon of 1917
12/09/2019 00:20:41

This gives a description of the Welin Breech Thread.


I've always wondered how they were made, so I'm looking forward to next week's exciting episode

Thread: wire bender
11/09/2019 19:06:00

Well the 'soft stainless wire' came, and boy do they mean soft. Under reasonable load from the m3 screw in the eye it squashes down to about 1/2 thickness. we gave up with ally wire because it relaxed under the screws, so sticking to the welding wire.

Thread: Loco at Marshalls Works 1906
10/09/2019 23:06:49

Brian has said it all, with the wheels not coupled by an axle, if the wheels on one side stop with the rod (singular) on front or rear centre, the front wheel doesn't know whether to go backwards or forwards when it all sets off again. With 2 wheels on the axle, the rod on the other side keeps it all going. Just try taking one coupling rod off a loco and turning one of the axles (wheels lifted off the rails obviously) It will soon get in a right tangle

Thread: How to upset the neighbours!
10/09/2019 19:20:06

Ex colleague of mine was a Harley nut, he had 'MOT exhausts' which only saw the light of day once a year.

Thread: Loco at Marshalls Works 1906
10/09/2019 19:15:25
Posted by JasonB on 08/09/2019 12:35:22:
Posted by duncan webster on 08/09/2019 11:13:19:

Putting it another way, I think the engine's centre of gravity is too high for the distance between axles. They've addressed that by dropping the boiler, cab, gearing etc deep inside the frame, but maybe that means it's running on less stiff stub axles. (Do the axles run through the boiler's innards?)



Coupling rods only work if both wheels are on one axle. I'd guess that the boiler only just clears the axles, but from the photo it looks very close

They would also work if there were a solid shaft like a traction engines 3rd or 4th shaft with a gear at each end driving the left and right rear wheels which would then turn the coupled front wheels.

No it won't work like that, you need 2 coupling rods and an axle connecting the front wheels even if the rear wheels are gear driven from a cross shaft

Thread: To Pin or Not To Pin
10/09/2019 19:06:18

Old loctite goes off more quickly, if you adjust it after it has started going off it weakens the bond. Don't ask how I know. If you do have to get it apart, warm up the joint, then clean it all up with paint stripper to get the residue off before you remake it.

10/09/2019 17:35:49
Posted by JasonB on 10/09/2019 17:11:17:

Taking your figures, you would have a joint good for upto 6000 if just using loctite and a perfect joint. Or a joint good for 4000 if just using pins but to get them both to fail you would need 10,000 so the combined use is stronger than one or the other.

That gives me peace of mind as per my reply in the other thread even if over any load that is likely to be applied..

It's all about stiffness. As the OP says, if the loctite hasn't failed, the pin isn't loaded, or at least not very much, and if the loctite fails then the pin follows in quick time. They are not really sharing the load. Drilling a diagonal hole for a pin (if that is what is meant) reduces the strength of the shaft considerably. I once literally blew up a 1te jack trying to get some loctited wheels off, 17mm dia * 20 long seat. Scaffold pole on the jack handle and the cylinder burst. Get it nice and clean, use new loctite (it has a shelf life), and observe the manufacturer's recommendation for fits

Edited By duncan webster on 10/09/2019 17:37:19

Thread: Loco wheels cast iron grade ?
09/09/2019 23:36:30
Posted by Andrew Johnston on 09/09/2019 19:25:51:

Cast iron is strong in compression but relatively weak in tension. And it is not ductile, so wouldn't stand up to the hammering from the track and out of balance forces. In contract SG iron is processed so that it is good in tension and compression........

Full size spoked wheels consisted of a cast iron centre with a shrunk on steel tire. The steel tire had good wear and shock load capabilities and being shrunk on put the cast iron centre in compression.


There are hundreds if not thousands of model locos out there with ordinary grey cast iron wheels.

Thread: Recommendation for Tool and Cutter Grinder
09/09/2019 15:35:44

Can'y you just put a very small countersink in the hole? I always do this when using capheads as they have a radius twixt head and shank. For very small screws like yours, just mount a countersink cutter in a file handle and do it by hand.

Thread: wire bender
09/09/2019 13:53:19
Posted by Neil Wyatt on 09/09/2019 11:18:24:

Splash out £1.49 and solve your problems.


Edited By Neil Wyatt on 09/09/2019 11:19:03

I ordered some at 10:42, but since then I've knocked out 50 off with my press tooling, if I can venture to give some bits of bar held in a drill vice such a professional sounding title

Just in case you all think I've become a spendthrift, it's the club's money!

Edited By duncan webster on 09/09/2019 13:54:18

09/09/2019 10:42:28

Annealed wire: obvious, why didn't I think of that? Just shows how useful this forum can be, I've ordered some. In the meantime, I've found a way of churning them out in welding wire, might be even easier in soft. It's a 2 stage process using a punch and dies, first op pushes the wire into a slot to form an open U shape, second step uses the same punch to round the ends, the backstop prevents the loop being pushed away as the punch closes the loop. I'm going to make a better die for the first op, I don't think the little cast iron vice would last very long. The piece of wood in the first picture supports the wire with the large radius horizontal so the loops are vertical if you see what I mean

Thanks to all who replied.

img_3674 (small).jpg


img_3676 (small).jpg

Edited By duncan webster on 09/09/2019 10:43:37

Thread: Loco at Marshalls Works 1906
08/09/2019 11:13:19

Putting it another way, I think the engine's centre of gravity is too high for the distance between axles. They've addressed that by dropping the boiler, cab, gearing etc deep inside the frame, but maybe that means it's running on less stiff stub axles. (Do the axles run through the boiler's innards?)



Coupling rods only work if both wheels are on one axle. I'd guess that the boiler only just clears the axles, but from the photo it looks very close

Thread: wire bender
08/09/2019 11:03:48

I've tried just bending round a nail, it works with copper, but not with SS, too springy. Using pliers you have to grip the wire and then sort of roll it along a flat metal surface. I'm going to try something more akin to a pipe bender, the bending pin on the proprietary ones looks too big. If it works I'll get back

We've looked into axle counters, or just short lengths of track circuit to act as interrupts, in fact the control board has the facility to do that, but can't figure out how to allow for trains being removed/added mid section (either at the normal access via swing link, or just lifted off/on) without a manual intervention. Experiment shows that magnet on the truck and reed switch on the track works well as a train detector, not sure how we'd make an axle detector, a very short length of track circuit isn't all that reliable, the wheel rail contact is not that good with steel wheels on aluminium, our logic allows for that, the section has to be clear for 5 seconds before the signal clears.

On the corrosion issue, we've had SS fishplates and bolts for quite a few years without any issue, and the first phase of signals has been in for nearly as long, Land Rover men have to contend with (road) salt water, perhaps that is more aggressive

07/09/2019 16:02:20

Frank, perhaps loose language, something corrodes like mad, we don't have the same problem with SS.

Ron, I want to buy a tool, got far too many other jobs on the go to start making one, I just need pointing at where to get it

Edited By duncan webster on 07/09/2019 16:03:41

Edited By duncan webster on 07/09/2019 16:04:16

07/09/2019 15:26:55

They are for linking the rails together in track circuits. Copper is a no-no, it corrodes like mad due to galvanic action against the aluminium rails (don't ask how I know). We've tried aluminium wire, but it is too soft, it relaxes under the bolts and comes loose, and is easily damaged giving rise to faults

Thread: Home Workshop Site
07/09/2019 14:55:24

Is there any news on how Adam is doing? I hope he is on the mend

Thread: wire bender
07/09/2019 14:46:22

The bits of wire in the photo are connectors for track circuiting our 5"g track. They are made from 0.8mm stainless MIG wire. I need a couple of hundred for phase 2, and my wrist already hurts from making 10 off with round nose pliers. Anyone know where I can get a little gadget to form the 3mm diameter loops on the ends? The large radius arc comes naturally from being supplied on a coil, and the small angle bend (to get the ends in line) is easy enough with pliers as it's only a small rotationjumpers (small).jpg

Edited By duncan webster on 07/09/2019 14:46:58

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