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Member postings for Paul Kemp

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

Thread: What causes Blowback in a steam locomotive firebox?
01/02/2018 20:58:44

Any interruption to the normal flow of gasses through the boiler! Passing through a tunnel or under a bridge are the common ones where the normal draughting of the blast pipe / chimney is disturbed. The fix is to have the bower on to augment the draught to keep things flowing in the right direction.

There are other circumstances where the same thing happens, notable the driver shutting off (closing the regulator) to coast down a grade or when stopping, the draw from the blast pipe is lost so there is no good draught through the boiler from firebox to smokebox so the flames will come out of the fire door if opened as they are given a nice ready supply of top air!

One of the first things drummed into you as a fireman is the proper use of the blower (blower is a shared control - ie used by driver and fireman) and the risk of blow backs. It's not an uncommon thing! In the last couple of years there was an incident on a mainline steam special where the footplate crew were quite badly burned and was the subject of an RAIB enquiry.

It's easilly done if the driver / fireman are not on the ball!

Thread: Am I doing this correctly?
29/01/2018 17:00:34


316 machines OK as long as you don't allow the cutter (either milling cutter, drill or turning tool) to rub without cutting as the surface will work harden and take the edge off whatever cutter you are using. If you use a carbide cutter and keep it cutting you should be ok. 316 in itself is relatively soft just very tough and work hardens.

Assuming what you have now is some years old it will definitely be made of something around the 316 grade - if it wasn't it would have rusted away by now! Who ever told you it was gauge plate is sadly a bit off track!


29/01/2018 10:20:29


Your proposed method of manufacture sounds fine if you don't run the cutter right through so you end up with a bevel edge.

However..... Are you really sure about your material? Gauge plate will have no resistance to corrosion in either fresh or salt water. Many years ago I was involved with development trials of 'Spurs' rope cutters for the RNLI and the metal parts of those were a cast stainless of a grade similar to 316. The original bearings were a fairly soft plastic consisting of 2 washers and a thin strip, the washers were put either side and the strip around the inner diameter, lifespan was a couple of months! They were soon changed to a moulded section in two pieces if I remember correctly of some Kevlar incorporated material which got us 12m. I can see your thinking re using a high carbon steel for hardness but I will be very surprised if the thin section of the sharp edge has not disappeared in a couple of weeks through corrosion. By the time you have made the blades and had them heat treated I imagine you will be looking at £100 they will definately need renewing or at the least resharpening in 12m time ad finitum, that doesn't make £475 sound too bad! As you mention a sail drive and that is probably not going to be in regular use you also run the risk of corrosion scale on the faces of the blades that need to pass each other jamming the shaft!

With your machinery what is stopping you machining back the faces of the existing blades a little (ok that will thin them and reduce strength but you probably won't need to take much off to true them up, the edge can be put back on with a die grinder) then making new 'bushes' accordingly to position the blades? At least they are a reasonable grade of stainless and are not rusting away!


Thread: HMS Queen Elizabeth: Leak found on new aircraft carrier
23/12/2017 01:11:36
Posted by ChrisH on 22/12/2017 23:50:07:

Gees, everyone seems to be getting all hot under the collar about this story but in reality, no-one here really knows anything. All we have is a flimsy press report and we all know how dodgy they can be, in fact, generally are. The only people who know are the Navy boys and they are saying nothing. Six pages we have here, all on about something we all know nothing about. We must all be mad. Have we not got sheds to go and play in? Why don't we just leave leaks in warship to those who know a bit about them to sort out quietly and properly; we have better things to occupy our time do we not? Not as though we are blessed with unlimited time, most of us.


Absolutely well said Sir. As someone said earlier it's nothing on a big ship. Six pages of opinion and speculation with some qualifying comments "I imagine". "I don't know anything about ships" etc. An issue talked up by the press because there was nothing more important or interesting to report at the time and if that wasn't bad enough then speculated to death on here! Being a cynic I would say the journalists have done an excellent job with a small and pretty insignificant piece of information in being able to generate this much interest! Before anyone else comments I suggest they first research ceramic faced marine seals and speak to someone with shipyard or marine engineering experience.


Thread: Harrison gear box
21/12/2017 10:00:23


I had a similar problem this year moving a Harrison L6 and I had the same reservations. It was also in a small shed in a garden (lawn) that was about 50' from the house, up hill from the house. There was a passage way between the houses little wider than the machine itself and a step from the lawn to the hard surface of the passage way with a drain right on the corner. At the front of the house the path went straight out onto the road (no front garden). I looked at lifting the lathe off the cabinet but was advised that if I did the seals between the two are difficult to refit and would likely need replacement. They are there to stop coolant / cutting oil getting down to the motor. I also looked at removing the motor but as pointed out by someone else earlier in this thread it adds useful weight to the base for transport as lathes are a little top heavy! Solution was to get some help from two good friends one with considerable experience of moving machines and an engine crane, the other having a plant trailer.

We extricated the machine complete less the chuck and any loose equipment. First step was to use a decent bar to lift it on blocks to remove the feet inserted in the bottom of the stand - from the bottom! Next it had to be turned 90 degrees to be rolled out of the door. Small rollers like 1/2" or 3/4 water barrel are a lot better than large ones like scaffold tube I found. I purchased a sheet of 3/4" ply split down the middle to give 2 pieces 2' X 8'. One was placed outside the door of the shed (about 4' from the boundary) so parallel with the shed and the machine had to be turned 90 degrees again as soon as it came out of the door! I then secured a pull lift with some long strops to a handy anchorage and this was used in conjunction with the rollers to lower it across the lawn down the slope, transferring the ply as we went. We then used small lumps of timber and one piece of ply to bridge over the drain and the step at the end of the lawn, keeping the weight on the pull lift to stop it rolling down out of control until on the flat of the passageway then just pushed it on the rollers down the passageway (very little effort required) until it was out in the road. We then slung it around the bed (important to wind the carriage towards the tailstock and have the tailstock at the end of the bed for balance) and lifted it with the engine crane, backed the plant trailer under, landing it on the rollers again and rolling it forward to balance the trailer. Then lifted with a bar and blocks of wood to remove the rollers, ratchet strapped it down and away. Took about 3 hours start to finish. No issues with the 10 mile journey and then put it back on the rollers, built a ramp with the ply and secured the pull lift to the trailer drawbar and lowered it down the ramp straight into the storage facility.

The important things are, work slowly and steadily, have a good plan and the necessary equipment before you start (rollers, timber packing of various thickness, couple of decent crow bars, pull lift perhaps, strops or decent rope) and be ready to change or adapt your plan as things progress. The fellow that was with me has moved his Bridgeport from house to house at least twice on his own so even on your own it can be done! I would advise you get a couple of willing and sensible people to give you some help though. However if you can't get sensible steady people you are probably best off doing it on your own, willing bulls in china shops make it more difficult and more dangerous!

Good luck.


Thread: A listing of potential helpers
18/12/2017 21:04:23

This is an interesting thread. I am fascinated by the comparisons between a full blown commercial business existing to make a profit and provide employment and the fellow in his shed doing the occasional job to help people out below commercial rates. In fact I don't see any obvious commercial advertiser on this site offering such a service so it's hardly in competition? Irrespective of the accepted definitions of commercial activity it's a bit like comparing Microsoft with your window cleaner!

I have the upmost respect for Jason B, he was instrumental in offering me assistance on another forum I joined and is a very skilled fellow producing some fantastic work. He also offers many practical suggestions and solutions to many contributors on this forum. I can't really agree with the moderator policy he states in this thread though, particularly with a current classified that has obviously not been challenged. I have no problem at all with this advert as I would have no problem with an "assistance thread" should it be started. I do think the moderation policy could do with some revision in this area though. I am sure it is possible in the forum software to make a section where every post has to be pre approved by a moderator before it is published to keep a control of the content and I can't see it attracting hundreds of posts so it's not likely to be an onerous duty?


Thread: Live Steam Loco Questions
18/12/2017 12:08:08



Posted by Sam Longley 1 on 18/12/2017 08:28:27:

Still nothing on cost of materials other than a comment on a commercial boiler!!

I cannot believe that those who work in such accurate dimensions & such rigid controls do not have at least an idea

Are you all deliberately blind to the cost or are you frightened SWMBO will find out?

If you do not know the cost do you have any idea how much you spend a week on the hobby ( perhaps you have a budget) & that might , when multiplied up over the building time of a model, give one some idea of what it cost. That might then include the all important cost of the additional tooling. Tooling, after all, must be a very big part for a new player. I certainly find it so.

I am building a small traction engine & as I come to a new component I find I have to stop because I do not have the material to make it or have B,,gered up the bit I had or tried to use the wrong bit & wasted time because I shuddered at the cost of the correct item.

It is really frustrating & may be what puts many off mid build & why there are so many part built projects about.If one knew & could plan at the start with greater accuracy there might be more finished models about.



If you read my post again you will see I quoted a rough figure of £3000, a bit difficult to be accurate when no specific design is being priced? As to finding you do not have the required material to hand as you progress through the build, with all due respect surely that is a planning issue? I am building a 6" scale traction engine and am constantly looking ahead, as one part is being worked on I am also looking at the next part to be done and aquiring the necessary. It was quite easy to put a budget against the final cost at the beginning, the cost of castings was published by the supplier in a list, with the drawings the cost for bronze for bearings, large section steel for rear axle and shafts etc was easy to price from the Internet. The cost for the boiler from a reputable boiler maker only took an email. If you want a more specific example I estimated the cost of boiler, castings, sundry material and additional tooling for the 6" Savage as £10k (it's quite a large engine being just short of 1000kg complete). I am about halfway through the build with all the major expenditure items like boiler, castings, bearing material, shafts and rubber tyres vulcanised to the wheels completed and am in round terms £2k in hand. The OP did state in his question on price "assuming all equipment is available" but I did qualify in my reply that may not include items like cutting tools. This hobby can be as expensive as you wish to make it! Maybe you would like to contribute what the costs have been for your engine rather than complain others are not being up front?


Edited By Paul Kemp on 18/12/2017 12:10:23

17/12/2017 23:51:43


There have been some good replies on the technical aspects and capabilities and various sizes already given. One thing I haven't seen addressed so far is cost. Cost of materials and castings is also variable with size and probably the most costly item is the boiler, you need a lot more copper to make a 5" gauge express loco boiler than a G1 or G3 shunter. It also depends if you want to make the boiler or if you want to buy from a commercial boiler maker. Castings are also expensive from the commercial suppliers, but you can fabricate or machine from solid some items like horn blocks (you will find out what they are as you go along if you are not familiar with them) and even cylinders. For say a 5" gauge 060 tank engine if you buy a ready made boiler and all the castings and get your other materials from one of the metal stock holders you could easilly be looking at £3000 plus. However if you fabricate and make your own boiler and pick up material from skips you can trim the cost considerably. You also said assuming you have the equipment but you will still need I would wager various drills, reamers, taps and dies!

As has been said in other threads of similar vein it is important to choose a design that inspires you, you are looking at perhaps 2000 hours or more in the workshop, so it has to captivate your interest if it is to get finished! There are an awful lot of part finished models around! Do your research as you have been, find a design you like but try to keep it simple, a 3 cylinder Pacific as a first loco is a bit ambitious and go for it!

Lastly on machinery, there is an awful lot of guff written about lathes and mills, Basically it is true that a decent heavily built rigid machine is more capable at maximum metal removal. However, for the 'hobby' machines as long as you can fit it in, if you are careful you can machine it. I completed all the milling operations for the water pump of a 6" scale traction engine on a Chester micro mill! Granted I was limited to ten thou cuts and it took a while but it can be done.


I know where you are coming from! It is not limited to this forum alone though, it's more common than you might think. People not reading an OP question correctly or where a specific question has been asked failing to answer it in a straightforward manner without suggesting some outlandish solution. Then there are the keyboard warriors that belittle and sometimes bully. There also seem to be individuals everywhere that feel compelled to contribute to a thread even though they have nothing useful to contribute to the subject outside of Aunty Maude once knew someone who could have answered this question. I read this forum regularly but seldom post, it's not too bad to be fair considering others I read but the subject matter is I also believe biased as you describe towards workshop machines and techniques rather than actual models. That said people have to be prepared to contribute, if no one is posting about models then there is nothing about models to read!


Thread: Hobbymat MD65 - Milling Angle Piece
06/04/2017 12:32:47

Obviously there must have been some variation over the production run of MD65's as the angle plate that came with mine is cast iron and the vice a very nice little thing. Before I got my milling machine I did a number of milling jobs with it and found it very satisfactory. Qualifying that the milling undertaken was mostly for a small 3.5" gauge loco but then again the MD65 is quite a small lathe.

As an aside I think overall the MD65 is a brilliant little lathe for its size. I have done all sorts of jobs on it that really were too big for it but providing you use sharp tools and appropriate sized cuts it does exactly what it says on the tin. Mine is now over 25 years old and only last week I turned a 1" diameter 'shaft' 8" long and it was parallel over the length by quarter of a thou. Using a nicely ground brazed tip tool I have taken 40 thou cuts on free cutting mild. I wouldn't swap it for anything else and while I have a ledger machine I still use it quite a bit.


Thread: Making work equipment.
31/03/2017 22:12:50

Definition of machinery in the machinery directive requires it to have at least one moving part, so your educator should be safely outside the machinery directive and as it is not to be put on the market also outside the scope of CE marking. So your HSE department can rest easy. Sounds like they have the usual proactive approach to getting the job done. HSE departments seem to be very focussed on why you can't do something instead of seeking out a way that you can!


Thread: Encouraging new hobbyists
24/03/2017 13:31:49

This is a multi faceted issue! The pecieved decline of model engineering, changes to lifestyles due to the economy and technology and changes to working practices are education are all factors.

Considering university education as that was the original question; The number of universities and consequently the number of students following degrees has exploded exponentially over the last 40 years. 40 years ago there were few universities and when I left school out of my whole year I think there was only one student who went on to university. Fast forward to the present and many colleges and polytechnics have evolved into universities and there is an expectation in schools that students will progress to university! 40 years ago graduates were the academic elite and degrees were prized, now it is the normal expectation that students will progress from A levels to a degree. The increased accessibility to university education has not necessarily lead to a higher number of highly educated graduates! Further education has become big business! Traditionally graduates were for white collar jobs, they were not expected to do be intimately involved with manual labour.

Employment; Heavy Engineering has declined in the UK, economic pressures have dictated that manufacturing has become automated (machines being cheaper to run than people) so there is less demand for people with manual skills, manual machining (which has been the main stay of model engineering from its inception) is in decline and now has become a premium in jobbing and repair shops. Most employers from what I see these days even in apprenticeships concentrate on giving apprentices the relevant skills applicable to their sphere of business and not necessarily a complete rounded bottom up training program (again dictated by economics). 40 years ago employers took on far more apprentices than they required and there was no gaurantee of a job at the end, this gave the employer the ability to cherry pick from the bunch.

Perceived decline in model engineering; From my own society over the last 40 years the demographic has changed. When I joined my local club at 16 the average age of members was around 50, today it is approaching 65. We are still getting new members but they are people approaching retirement age. If you looked at occupations little has changed, years ago members actually employed in engineering or with formal training in engineering only accounted for around 20% of the total, the remainder were bank managers, dentists, media people etc. Today new members are less likely to be or have been professionally involved in engineering but they are starting their interest later. The few members we gain in the 40 to 65 age group are now most likely to buy a ready built, ready to run locomotive (steam and electric) or traction engine. Our membership numbers peaked in the 80's at around 60 members and has remained fairly steady around that number since. So the evidence says overall the interest has not declined but has changed, new members are much less likely to have or aspire too a reasonably equipped workshop.

So to return to the original point re university students and practical experience; traditional universities never churned out fitter / turners they churned out managers, designers and concept people. If employers now are finding the products of universities do not have the skills they require then industry needs to address this with universities and examination bodies to tailor the courses to meet their needs. It seems to me universities these days are run by academics and accountants with the objectives of generating as much revenue as possible rather than meeting a genuine need of employers. I also think from what I read and see that universities have reached or are close to reaching their peak and due to the rising costs on students to gain a university education and levels of debt students leave with there will be a decline in student numbers and potentially a decline in the number of universities. My conclusion is students in terms of what they are taught and employers in terms of what they would like their new graduate employees to know are not being best served by universities that have the objective of clawing in cash and tailoring courses and facilities to what they think is best, rather than what is really required. Interesting times!


Thread: Steam engine with centrifugal pump Pictures
10/03/2017 00:26:46

Two steam ports, one inlet, one exhaust. The outer ones are the inlets and inners the exhaust (exhaust goes to cavity under the valve, inlet is exposed by the valve to the steam chest).


Thread: Brass cylinder block correction question
27/02/2017 17:30:28

Picture might be helpful. Doubtful if ordinary soft solder will last the course, depends on your working pressure / steam temperature. Higher melting point soft solder might do it (Comsol) but I wouldn't rely on it. What is the thickness of the material between the inlet and exhaust ports? Would it be possible to open out the cylinder end of the hole a little and tap a suitable thread in the part you want to plug and then fit a short screwed plug with high temp loctite? That would be a positive definite solution. Another possibility might be to tap the existing hole all the way through and fit a long brass plug and then re-drill in the correct position? I do know of someone who has used JB Weld in this sort of application to recover a cast iron cylinder block where the cored transfer passage was not positioned correctly and ran into a drain cock bore. It's still working as far as I know but it's not something I would do out of choice.


Thread: Small pipe fittings
24/02/2017 18:06:35


Be aware that theoretically brass is not a good material for boiler fittings due to zinc being leached out leaving a spongy copper matrix that is weak and prone to failure! You should use gunmetal or bronze. However practically I think most of the commercial suppliers seem to use brass, certainly those that I have purchased in the past seem to be brass. They should be fine as long as you inspect them regularly and replace any that are going an orange colour.


Thread: Track laying
24/02/2017 17:56:02

Minimum radius for a short wheel base 040 5" gauge is 10' with minimal gauge widening. An 060 however won't go round that, needs closer to 30'. Not tried with a 3 1/2" gauge loco but 20' would probably be the minimum ideal, you might get down to 15' if you widen the gauge by 1/16" or so. Best to use aluminium rail for tight curves then the rail is more likely to wear than the wheel flanges on the loco! Also remember you will need to be loose coupled or on a reasonably long bar to prevent buffer locking. As already said don't forget anything you will be pulling behind, again for tight curves 4 wheel, short wheel base bogies under any stock will be best.


Thread: Square Gas Tank
24/02/2017 17:42:40

You say you were pressure testing it and it leaked at 100psi - what pressure were you intending to go to? Pure Butane in its liquid phase will be 2.6 bar at 38 degrees C I believe. How hot are you expecting the tank to get? 90 psi as 2 X WP should be adequate for a pressure test surely?


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