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Member postings for Marcus Bowman

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

Thread: Looking for a supplier of tool grinding wheels.
18/09/2017 20:27:25

I have used AbTec for several wheels for surface grinding and for tool & cutter grinding, in recent times, and have had a happy experience.


Thread: Boring large diameter hole in aluminium bar
05/09/2017 19:05:20

Although 8 and 12mm bars are useful, I made an additional larger diameter bar with an HSS tip for finishing cuts on larger bores. It's 25mm diameter and much more rigid than the smaller bars. Although the tip is an inserted bar of HSS, it is fine for 2 or 3 fine finishing passes (all of the same depth of cut). It is a bit of a chore having to remove the 4-way toolpost and mount the big bar, but I have found it pays dividends. One of these days, I will make a similar bar which takes a polished tip insert. As you probably know, those polished inserts are available with different tip radii, and the slightly larger radii are ideal for smooth finishing cuts.

I have bought nice inserts and bars, and other tooling, from (with whom I have no connection).


Thread: LBSC's Designs
05/09/2017 15:41:24

LBSC's magazine articles did that, of course. His subsequent books did the same thing for individual designs. In modern times, the equivalent is the ARM1G design, the book for which is shown here:

and its predecessors (Project and Dee), although ARM1G is designed to accomplish just what you describe, including lots of parts which can be bought from trade sources, such as frames, complete cylinder assemblies etc, so that the entry level can be tailored to an individual's pocket, capabilities and resources.

There is a case for 3D modelling of LBSC's designs, as a project in its own right.

There is another case for updating those designs, by converting sympathetically to metric dimensions (which would get my vote) to make them accessible for younger or newer builders (say under 70), and/or by updating the designs comprehensively to modern standards and practices, including modifications in the light of previous builders' experiences.

There is also a case for preserving the 'words and music' of text and drawings from the magazine articles. Those preserve an important aspect of his success, which is the 'can do' spirit. I agree with earlier comments about LBSC's intentions, and his ability to describe how to do the job with limited resources. It would not, however, be my approach now, as I think that although it may (and I do say 'may' lead to success, there is a danger that it fosters an attitude which rather devalues the depth of understanding and sheer skill which can be developed by deliberately pushing oneself to develop the appropriate workshop resources and associated skills to do the job in a more precise, and often more effective, way. This is, if you like, the difference between the approaches of LBSC and G. H. Thomas [I will stop here, as I notice a hobby horse preparing to gallop]. This is important, though, as it impinges on the discussion of whether to simply preserve the LBSC designs in their original state, or whether to comprehensively update them.

Drawings re-drawn by the magazine staff would be M.E. copyright, of course, as would the page layouts, but the words and original illustrations and drawings belong to LBSC's estate. Which takes us full circle, I think...


Thread: Boring large diameter hole in aluminium bar
05/09/2017 08:07:34

RPM = cutting speed (metres/min) / circumference (metres)

Aluminium has by far the highest recommended cutting speed of all the common materials in our workshops, at 75 to 105 metres/min for HSS tools and 900 to 2200 metres/min with an uncoated polished insert.

At the lower end, on a 50mm diameter bore, that translates to 500 - 668rpm for HSS and 5732 - 14102rpm for a tipped tool. Two limiting factors have already been mentioned: lathe top speed and chuck rating.

So; run the lathe at top speed, but expect the carriage feed rate to be slow. The tipped tool rpm are well outside the Myford/Boxford/mini-lathe speeds, but that will not prevent the tips working reasonably well. I certainly would not be inclined to attempt this job with HSS tools, but opinions (and results) vary. I machine aluminium frequently on the lathe and the mill and have found the tipped tools or polished carbide cutters ground with cutting angles specifically designed for aluminium to be the answer to the clogging and sticking problem. Flood coolant helps too, of course, if you can stand the mess. WD40 stinks too much for me. Carnauba wax works too, but is too laborious to apply, and too expensive. Neat cutting oil works, as does water-soluble cutting oil. Application by toothbrush is too much effort, on a time-consuming job like this.

Some manual lathes (Hardinge, for example) can run at 5000rpm, and suitably rated chucks are available at a price.

The smaller diameter stages of drilling and initial boring will work best at correspondingly higher rpm.

In the end, we do what we can with what we have, and a 50mm hole is perfectly achievable without too much difficulty (except, as previously noted, for the copious swarf).

Despite the higher recommended speeds, I would simply use top speed and be content with the chrome-like finish on the final finishing cuts. Wondrous to behold.

Two other points:

The work needs to be gripped in such a way that there is clearance behind the work for the cutter to pass through without hitting chuck or faceplate, at maximum cut diameter.

The boring bar for the final stages needs to be stiff and/or of large diameter, to prevent 'ringing', and to provide sufficient rigidity for the finishing cuts. It depends on the finish you need on the job.


04/09/2017 08:11:21

I have recently done much the same thing, for several workpieces. In aluminium, machining speeds are so high this is not a terribly lengthy job using large drills then a boring bar, compared to the same thing (also recently undertaken) in steel.

I mounted my AL in the chuck, drilled to 19mm, then used a toolpost-mounted boring bar and power carriage feed.

I used a tipped tool with an insert designed for AL (mirror polished, and with an aggressive rake). You have little chance without that, as an HSS tool will clog in seconds, especially at higher speeds without a lubricant. Using the insert, I machined the work dry, although flood coolant would be better. Coolant will also help prevent HSS tools clogging, but not for long.

I also changed the speeds as the diameter of the bore increased, to stay within the efficient cutting speed range.

The grade of AL also makes a huge difference. I used 6082 (HE30). 7000 grades are even better, but much more expensive.

Thread: LBSC's Designs
04/09/2017 08:03:23
Posted by John Lluch on 03/09/2017 21:16:28:
Posted by HOWARDT on 03/09/2017 19:37:07:

If it is the intention to keep the creations as CAD models and drawings, what format will be used. I worked as a designer all my life, and went to CAD in 1989. With changes to the core of the CAD systems old files become unreadable unless you convert immediately after the change. Also later minor changes make for incompatibility. The only sure way is to create jpg scans or similar, even PDF may not be an option. Just a thought, but been there and got the tee shirt on reading old files!

About CAD, I am not aware of any format that would open (in an editable form) in all software platforms. However, for the purposes of dynamic display only, there are several file types that will open in most CAD systems. This does not solve of course the problem of maintaining an editable version of the 3D plans, which will be required to keep future compatibility. I am used to SolidEdge from Siemens because that's what I learned, and that's what I would chose, but I suppose SolidWorks can be considered a better choice because I understand it is more widespread. Other CAD systems have options to import SolidWorks files, though generally in a non fully editable way.

Finally, if the possible legal issues about ownership can be solved, a good thing to do would be to open source the 3D plans files to let everybody propose improvements or correct errors by pushing updates based on experience while building the actual locomotives.

Interesting points, raising different issues.

Firstly. although I like the idea of open source plans available in an editable format, the CAD platform would have to be open source, to allow anyone to edit or alter the plans. There are several possibilities, but there is a somewhat larger question. The nature of open source suggests that a user could make changes and re-post the plans. That might be useful for allowing the correction of universally accepted errors or making necessary modifications. But that leads to two questions: who is to say those errors and/or modifications are necessary (because the plans would then deviate from the original); and who then controls availability of the new open source plans?

One solution is to use a platform such as GIT, where changes are tracked, and it is clear which versions are which, and, especially, which is the current version.

Controlling the addition of modifications and 'enhancements' becomes important as plans are changed and morph into something else, over time. Take 'Pansy' for example. Doug Hewson's version is more accurate and up-to-date, incorporating much more modern approaches, so if I was to make a Pansy, I would choose Doug's drawings. But would it then be fair to call that LBSC's PANSY? It's not a straightforward question. I would not want to use any of the LBSC boilers, because they really need to be brought up to date to comply with current legislation and safety requirements. But does changing the boiler make those designs non-LBSC? We need some person or group to control this aspect.

I might draw the distinction between the developmental course of Mach3 and LinuxCNC, for example. Mach3 was originally updated and amended by its creator. When it was sold on, modifications and bug corrections stopped, as the new owners focussed on Mach4 development. They control development, so that was their choice.

LinuxCNC, on the other hand, is open source, and undergoes active development, with new versions available from a central repository. The development is driven by user suggestion and by the willingness of users to contribute to that development. Older versions remain available.

A mechanism of some sort is required to manage any changes. It could either be the original draughtsman, or a user-driven group. What would not be good would be the model where development was frozen once the initial drawings had been released.

As to the format of the plans; this could either be an agreed open source CAD package, or simply the DXF files. The difference is that having the CAD package available to everyone would allow anyone to edit the plans and perhaps incorporate their own mods, for their person use. The DXF files would be the most useful for the person who simply wanted to take and use the plans. DXF may allow some modifications within some packages, but would certainly allow the CAM stage to take place, to prepare G code files for manufacture by CNC.

PDF files would allow non-CNC manufacture, just like existing paper plans. The benefit of PDF files is that printing could take place at any size or scale. Larger format plans can be printed by may local print/copy shops.

JPEG files are not quite as useful, if the print size is to be made larger, as definition suffers when the file is enlarged beyond the native size. PDF, on the other hand, scales well.


21/08/2017 07:37:22

I assume you know of LBSC's book 'Shop, Shed and Road'? It contains some photos of some of his designs. It does not contain build instructions for any complete locos, but it does deal with his standard fittings and approach to design and construction, including: injectors, pumps, gauges, whistles, safety valves, releif valves and snifting valves, motion work, lubricators, North-Eastern compounds and Mini-steam engines.

First published in 1929, the version I have is the 1969 version edited by the late Martin Evans.

There is also the book 'MONA: A simple 0-6-2 tank engine' by LBSC. That has drawings and build instructions for MONA in 3&1/2 and 1&1/4 inch versions.

The Gauge 1 Model Railway Association members are familiar with LBSC's gauge 1 designs

You may also be interested in the copyright position stated here:

What would be of tremendous interest to me would be new sets of drawings, updated to reflect modern safety standards (boilers etc), and dimensioned primarily in metric units. If you want the designs to live on, that's the way to go, IMHO.

Your CAD approach is the right one, I think, especially as it would allow easy transfer of the drawings from CAD to CAM and CNC with little effort.


Thread: LBSC Memorial Rally
17/08/2017 21:58:32

Excellent idea.


Thread: LBSC's Designs
17/08/2017 21:56:06

Copyright for literary persists for 70 years after the death of the author. I remember attending a conference in 1995 at which this issue was raised, at the time when the Alice in Wonderland books were about to go out of copyright. Aspects of the 1995 Act were somewhat controversial, but the basic rule is that for literary works copyright continues to exist for 70 years after the death of the author.


Thread: Screw Bolt and Nut supplier
06/06/2017 23:25:49

Ah, Whistons. Sorely missed. I still have lots of the little bundles which were supplied wrapped in old newspaper...

The "assorted BA screws" still come in handy. There must have been a thousand in the bag. And the very odd sizes of silver steel wire and small rod. I could go on, but my specs are misting up with nostalgia...


Thread: Woodwards gearless clock
06/06/2017 23:21:50


One of the books I have, to which I find myself returning at intervals, is one of Derek Roberts' volumes: Precision Pendulum Clocks - France, Germany, America, and Recent Advancements. This contains little theory, and is too expensive as a casual purchase, but it contains many good photos of mechanisms, particularly the pendulums, suspensions and other details of the later fine timekeeprs by Reifler, Fedchenko; The Littlemore clock, and it has a chapter by Philip Woodward. There is much joy to be had just savouring the fine craftsmanship. Examples of many of the mechanisms can be seen at the Royal Observatory.

Another book I see mentioned from time to time, and again in this month's Horological Journal, is The Theory of Horology, by Reymondin, Monnier, Jeanneret and Pelaratti, published by the Swiss Federation of Technical Colleges/WOSTEP with the latest edition dated 2015. I am not convinced you would find enough about clocks in the book, or enough about heavy theory, as the description says more about watches. Fearfully expensive, but a book that has been around for a long time. I do not have a copy on my shelves, as my pocket money won't stretch that far.


Thread: Hey guys help me please - Boxford ID
02/06/2017 08:03:12

Looks like a C to me. says 'A (gearbox and power feeds), B (changewheels with power feeds) and C (changewheels and hand-cross feed) ' and that accords with my own experience.

The leadscrew engagement handle also tells you something about the age (black plastic on the much later models), as does the position of the backgear change handle (top of the headstock on much later models). The thickness of the base of the cross-slide indicates whether the lathe is 4.5inch or 5inch centre height.

Serial number (often at the right hand end of the bed, stamped into the front bed way, should also tell you (at least on the underdrive machines, but I imagine on the others too).

There are different bed lengths.


Thread: Woodwards gearless clock
23/05/2017 07:41:16

Woodward wrote 'Woodward on Time' (WOT) which is excellent. However; I don't have 'My Own Right Time' (MORT) and suspect there is some overlap. WOT contains all of Woodward's articles, mostly published in the Horological Journal (monthly journal of the British Horological Journal). You will find much of interest at the level you seek, in the BHI Journal. Membership is not cheap, and the Journal does not have a huge number of pages (about 44 pages per issue), however; it is the place where you will find the most relevant information and articles, both practical and theoretical (reflecting the craft/theory balance typical of the way horology has developed.

The USA-based National Association of Watch and Clock Collectors (NAWCC) are worth a look, but once a member you may also opt into the Horological Science Newsletter, which will more than satisfy any desire you might have to delve into theory. I have found them to be an excellent and very helpful source.

There are lots of books dealing in a serious manner with particular aspects of clocks and watches; and some of those contain some theory. Many contain an in-depth review of a particular kind of clock, and some contain associated musing s on the theory. There are also lots which review types of clocks but do not delve into theory at all. All are expensive (a trait of horological publications of any size).

I believe the craft/theory balance is represented by Wilding and Woodward. John Wildings books are tremendous if you want to make a clock but are not bothered by theory; while Woodward never intended to be a maker, but was interested in the theory. Both have helped take us forward, and both are necessary components in the development of theory. That craft-then-theory path represents fairly typically the way horology has developed since its beginnings. I do believe, though, that the subtle underlying physics are just that - subtle- and most people looking at, or even repairing a clock or watch do not fully appreciate the influence of physics on the physical article, or the theory brought into action in a clock. That's not just true in horology, of course.

Woodward's most important practical work, based on theory, was W5, an impressively accurate clock completed in 1985, and detailed in MORT, I believe. WOT contains a chapter entitled 'A Fresh Look At W5' (first published in Horological Science Newsletter). There has been a lot of interest in that clock, and the underlying theory, and it has been subject to some important development, since the WOT book.

One or two other titles from my bookshelf:

The Science of Clocks and Watches (Rawlings)

Clock and Watch Escapements (Gazeley)

Wheel and Pinion Cutting in Horology (Wild)

One of the conundrums is that early pioneers understood, at least partially, what they were doing, but did not develop the physics or spread the knowledge. The craftsamn protected his own key knowledge, perhpas? That means later studies of the development of particular types of clocks represent an attempt to trace, reveal, and understand the early knowledge (a kind of knowledge archeology perhpas). So there are interesting strands of theory in many of the serious horological books on particlat clocks. Synchronome, by Miles, for example, survays the life and works of Synchronome and his clocks, but also contains clear and well expressed explanations of the theory and practical realisation on which the clocks are based. So a further list perhpas depends on the kind of clock in which you are interested.

I have those kinds of books on Synchronome, longcase, precision pendulum, chronomoeter, musical and electric clocks, which suggests I am interested in the pure mechanics and physics in all clocks and watches, which seems about right. That's the spot that Woodward hits. MORT and WOT being the top of that pile.


Thread: This monster arrived in our small harbour today
19/05/2017 23:06:58

I console myself with the thought that the annual running cost of a large Paul-Allen-style boat is approximately 10% of its running cost. Paul Allen owns TWO of the world's 100 largest super yachts. Octopus cost $200M and Tatoosh cost $160M, so the annual bill just for his water-borne transport is, er..., enough to keep the economy of a small country afloat.

I have to say that, like Neil, I do rather like those big boats.

That's clearly an aspirational statement, because all my yachts are currently models under 1metre. I need to think bigger.


Thread: Woodwards gearless clock
18/04/2017 23:51:35

There is an article in Horological Journal dated March 2003 2hich is by Derek Pratt, discussing his double daisy wheel mechanism on one of his sculptural clocks. There is a mention of an earlier article by Peter Hastins in the August 1979 issue, which is seen as a seminal article giving a comprehensive explanation of the daisy wheel and its many variations.

Here's a thought:

I have built several clocks using a daisy wheel arrangement for the drive to the hands. The basic dimensions were taken from a John Wilding design, and he, in turn, took the dimensions from a much earlier article.

When I chased up the source documents, I discovered that the daisy wheel is an inherently non-linear gearing. The time will be correct at some point, but will be too advanced at some intermediate times, and too retarded at others. The variation is dependent on the length of the anti-rotation stalk. I have a relatively long stalk, but the variation is still present.

I had to vary the dimensions of the daisy wheel itself, and then had to experiment with the pin spacing to get it all to work in a smaller size (the problem being that the as-designed size causes the wheel to obscure the winding square, in some positions of the eccentric cam). I couldn't get the dimensions to scale from the original theoretical explanation.

I also find that there is considerable scope for the weight of the hands to emphasize the clearance present in the daisy gearing.

So; an interesting, but deceptively simple solution to gearing the hands.

It does look pretty though, especially if you skeletonize the daisy wheel itself.


Thread: Polishing Stones
09/04/2017 22:55:10

Water of Ayr stones were produced a few miles from where I stay. Quarrying from the river Ayr was halted many years ago, and as far as I know the stocks are all gone. I still see it listed as available in some places, but don't know if that is the real thing. I have a couple of sticks I use from time to time. It is very soft, and I would suggest too soft for everyday use. I only use it for frosting polished brass plates.

For honing, it depends on the fineness of the finish you require.

600 grit diamond stone, followed by 1200 grit, will give a finish good enough for the faces of a graver for turning steel or brass. Those stones/plates are readily available. For finer finish, a 2000 grit diamond stone or a ceramic lapping stone or wheel used with diamond spray (3 micron, down as far as 1/4 micron). If you need a better finish than that, you better order some strong sunglasses...

Hardened work takes a better polish that unhardened material, so, as with grinding, harden the work before polishing. Yes; unhardened work can be lapped more quickly, but it will not take a really good finish or polish.

Other interesting polishing and lapping compounds include traditional powders and polishes used by clock and watchmakers. I'm not convinced they are capable of giving a better polish than diamond spray, though. I have one or two powders, but use them infrequently.

If you have a lot of lapping/polishing to do, you might look at the GRS Power Hone (try H.S. Walsh).

There are also some useful polishing papers, from the finer grades of emery 0, 0/2, 0/4 etc, and crocus paper.

For plastics, there are micro-polishing fluids and pads which give a terrific finish if you have the patience.

Arkansas stone is worth a look too, but is rather expensive, and, in the end, not any better than diamond; and less effective than the finest grades of diamond spray.

The only real problem with all of this is that a really fine finish takes a little time.


Thread: disappointed - feel I have been cheated
06/03/2017 08:12:06

I think this is also an issue with other magazines from other companies. I have a digital subscription to another magazine and find the digital copy not half as handy as the paper copy, while the paper copy would come via surface mail from far away and be much more expensive. I will not renew that digital subscription, but, as you found, I think I will lose the ability to access the digital copies.

So it seems as though we buy access only and not actually a copy of the magazine.

For the magazine to which I subscribed, I have already decided that the content is not worth the continued subscription, so that solves the problem.

This, of course, is the software subscription problem, where software companies are moving rapidly to a subscription basis where you get to use the software, but only as long as you pay the monthly subscription. The accumulated cost is very high indeed, but you are effectively paying a ransom to be able to continue to access the files you create using the software. Local copies of files are fine, but if you can't access the software to open the files, you will be stuck.

Can you download the issues as PDF files?

Is there a Kindle version available, because there is no annual subscription for the device, and the files are added to your perpetual "cloud" storage area?


Thread: Forming round heads on small steel rivets.
06/03/2017 08:02:40

Once you have seated the rivet, if you make the free length of shank protruding beyond the material (the part you will punch to make the head) between 1.25 and 1.5 times the diameter of the shank. That will allow you enough material to form the head. Less than 1.25 x dia is too little to form a complete hemisphere, and more than 1.5 x dia is too much, which results in the bit nearest the plate/sheet being squashed out, like a fungus at the bottom of a mushroom.

The previous advice to use the pre-formed heads on the outside is good, but not always possible.

Pliers-style manual snap tools used to be available from a chap called Dave Noble, but seem not to have been obtainable for some years. There was a good design in MEW or ME some time ago, and I think Model Engineers Laser does the laser cut parts.. The trouble is the operating head is quite large and needs to be able to fit behind the rivet. There is also an air powered tool commonly called a crocodile (or alligator?) which squeezes rivets closed, forming a flat head or a mushroom head, depending on the anvils fitted to the tool. I have one of those tools, but, again, it is usually too large or has too short a throat to fit where I want to rivet.


Thread: John Wilding Elegant Scroll Skeleton Clock
14/02/2017 09:27:29

The pinions for this clock are stated as being "best" made out of blued pivot steel. I disagree strongly. Pivot steel/Pinion wire has a poor finish on the surface. Try abrading it lightly with a very fine paper, and you will see the surface is like a ploughed field. The wire will be uncut, so that's not going to provide the low-friction surface you need. Carbide rod or HSS rod would be much better.


14/02/2017 09:21:40

One of the problems with the dimensions is that while they are all in imperial units, cycloidal gears are usually dimensioned in Module (M), which is a metric measure.

42DP is approximately the same as 0.6M, but not exactly. So if you convert calculations based on 0.6M to imperial units, there is a small error. The same would be true if you did it the other way around, of course.

Using the Thornton's guide to wheel and pinion cutters,

Module (M) = twice the centre distance in millimetres / sum of teeth in wheel and pinion

Or: centre distance = half of sum of teeth x M

= 98 x 0.6 = 59.8 giving a centre distance of 29.9mm

1&5/32 is 29.36875mm and 1&7/32 is 30.95, so you can see that either imperial figure is a compromise and, as the drawing says “approx”.

It is not unusual to vary the depth of cut on a clock wheel, just a little, so I would use a 0.6M cutter, and increase the depth just a touch. That ‘touch’ could probably be calculated from the Thornton’s guide, or perhaps by using Gearotic (which I think now includes cycloidal gears). That thins the teeth slightly, but not enough, in this case, to cause a problem.

I have seen a clockmaker’s depthing “tool” which allowed meshing to take place without disturbing the dividing setup used to cut the teeth of the wheel, so that the correct depth can be judged at that stage. They are not common, and would not be required for this job, although one would be jolly convenient.

It would be worth calculating all the centre distances, as a check, to see if any others need a slight adjustment, or if the errors cancel out as you progress up the train.


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