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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: London Model Engineering Exhibition - Alexandra Palace
19/01/2019 10:28:44

I went yesterday too with three fellow club members. Seemed a similar amount of people around as last year, many carrying bags and boxes indicating money was being spent! Do agree though that with the exception of RDG, Tracey Tools, Warco, myford, Polly and Blackgates some of the traders had pulled their horns in further. What did strike me is the balance between 'engineering' and 'ship' models seems to be steadily shifting towards marine. Very few traction engine models at all. There were some cracking models in both classes and some of the steam powered boats combined both disciplines. Also good to see more of the less than gold medal standard, polished within an inch of destruction models around! Personally I think it's good to see things that are less than perfect on display, gives those aspiring or just starting out some confidence in what they can achieve too. It's good to see clubs supporting the event and putting on a good show and variety of members work, it's not easy to get members inspired to support a club prescence, well done.

All that said and despite being able to pick up most of what was on my shopping list I think all in our party (who have all been regular attendee's over the years and various venues) came away feeling a little flat. Not easy to really put a finger on why. Three of us up until a couple of years ago used to make the trek to the Midlands Show too, with increasing costs and a similar feeling for that show we haven't made the journey since 2016, I suspect that London for us will go the same way.


Thread: 2"durham and north yorkshire
19/01/2019 09:48:29


As Jason says! I am not very familiar with the DNY engine but there should be at least one bush low down on either the sides or front of the fire box just above the foundation ring for a blow down valve, possibly more than one in which case the others will be for wash out plugs, any of these that are accessible will do to connect your air line if you don't have the blow down valve fitted yet. In fact if you don't have any fittings mounted on the boiler yet then any of the tapped bushes will do for this test as long as you fit blanks to the others. Putting pressure on the boiler as Jason says has the advantage of being able to test the regulator and also the saddle flange to the boiler. You should only need to put 15 or 20 psi on it to get it to turn unless it's exceptionally tight, in which case you need to find out why it's tight and ease it first! Sticking high pressure air on the boiler / assembly may not be the best idea if you haven't checked the integrity of all the plugs and fastenings first with a hydraulic test as even 20 psi of air can project a loose plug out with enough force to do injury if it hits you in the eye! I add the latter because your post suggests you may not have great deal of experience of boilers and steam engines - if that is wrong, my apologies! It's not a massively high risk operation but do take due care and make sure you have a pressure gauge connected somewhere in the system so you know you are not over pressuring the boiler!


Thread: Is it just me?
19/01/2019 09:28:55

I have had exactly the same over the last couple of months, been looking for a company that will sharpen some involute gear cutters for me, have used email addresses on half a dozen web sites and the contact us feature where no other email address is shown, all with zero result!

Makes you wonder why any organisation would maintain a web presence advertising their services if they are not going to bother to respond to enquiries? They may be making an assumption that it's a one off job and they are not interested but how long does it take to type, sorry we are too busy with large jobs? Certainly less time than it takes for someone to answer the phone if I call them! Is a lack of response a true indicator of their reliability and competence to do the job? Also how do they know their assumption that this is a pain in ass one off job will not lead to a regular contract for more work or is it such a niche business that they have as much as they can handle already and don't care?

That aside, does anyone know of a company that can sharpen 4DP cutters that I can try?


Thread: 2"durham and north yorkshire
18/01/2019 20:05:19


I am probably being extremely dumb here but what is the test designed to show / prove? If you have removed the valve and buckle then I am assuming you are not expecting it to run?


Thread: Part built Allchin 1.5 inch
18/01/2019 19:56:50


Sounds about right. Couple of off the cuff comments; previously when making pistons I have roughed out the blank including the centre hole / fixing arrangements and ring grooves and then mounted the piston on its rod and held the rod true in a collet or clocked in the four jaw and finish turn the details to make sure everything is concentric and square with the rod. Good test is mount the piston on its rod, put your hand over the end of the liner, pull the rod / piston and release, the piston should return to the initial position or thereabouts if there is no or minimal leakage.


Thread: Hobby lathe
17/01/2019 11:23:37


If you are within travel distance of London nip up to Ally Pally tomorow or over the weekend and you will find some vendors with machines on display. If you are judging them against S&B, Hardinge or Bridgeport though in terms of rigidity prepare to be disappointed. That said most of them will do what they claim just not as quickly in terms of metal removal rates.


Thread: Brazing hearth - Extraction
16/01/2019 22:39:12

You could also use a compressed air jet in place of the fan (or shop vac) in Jeff's second method. Use small drillings in the nozzle to reduce the volume of air used, if you three or four small jets appropriately angled (like a loco blower) you can get maximum effect for minimum compressed air volume.


Thread: Burrell Cylinder
16/01/2019 22:30:59


Well done. Good to hear you are making progress, don't forget to take some pictures!


Thread: Bending copper pipe
16/01/2019 01:11:50

I had a similar requirement with 1/2" pipe and a 1" radius bend a few years back for the blast pipe on my traction engine. Bend needed to be tight to get the blast nozzle in the centre of the chimney! The pipe was thin walled AC copper pipe also which made it worse. Did a bit of research and salt was recommended rather than sand as it is finer and packs tighter. In order to get the salt to pack down tight it was recommended to hold an engraver or similar against the pipe to induce vibration to pack it down (didn't try that as I didn't have one!). Was told there was no way I would get a bend that tight! Red rag........ I annealed the pipe and packed it with salt, crimping the ends. Got a lump of hardwood and filed a profile of half the diameter of the pipe into it and the radius required. Then clamped the pipe to it with a horseshoe type bracket and used the back former from a commercial bender (straight lump of ally with a u groove milled in it, half the diameter of the pipe) and worked it round by hand. On completion it was a pretty fair bend, the pipe had gone a little oval but removing the salt, another anneal and some careful dressing with a planishing hammer sorted it. Polished up quite nicely. Subsequently I was advised to put a cork in one end of the pipe, fill with water and put in the freezer (after annealing) instead of filling with salt or sand. Not had a need to try that yet but it sounds plausible and it's cheap and clean. Would allow a second anneal during the bend without having to un crimp the pipe to empty the filling medium and clean it out before annealing again. I have a similar job to do with 1" pipe this year for the latest engine so may give the ice method a shot.


Thread: What Did You Do Today 2019
15/01/2019 13:49:45
Posted by Douglas Johnston on 15/01/2019 09:14:42:
Posted by Iain Downs on 14/01/2019 20:52:34:

I have a nice note from the vendor of the £12.80 gear cutting set explaining that the batch they got in was poor quality (yeah, right). They offered no options, so I asked when they would get a good batch in....

You never know - I might just get something if I keep on. At least a refund...

Just read my message from the vendor saying the same thing, might have known it was too good to be true. As an aside I saw and bought an item from Amazon a couple of weeks ago that was listed at £3.99 when it should have been £39.99. I fully expected to get a message saying the listing was wrong, but to my delight the item arrived a few days later and I only paid the £3.99.


Hmmm, this rings a bell! When I got my mill I wanted to get it up and running, was on a tight budget, so looked to China for VFD's. I found one supplier on the rainforest marketing site that was offering what I needed for just over £20ea!! So I ordered two which including shipping came to around £48! I didn't expect the transaction to go through as the gear cutters but got order acknowledgement and then notification of shipping. Eight weeks later I noticed the tracking said they had been delivered! Checking they were apparently at the mail reception centre in Southampton! Vendor then advised they had been damaged in shipping and were being returned to them and offered a refund. I refused a refund and requested they send replacements, they said they couldn't send replacements until the originals were recieved back and after a bit of bouncing around they refunded the money anyway and refused to respond to any further contact. Luckily I have a friend who does a fair bit of business with China and he passed me a local contact to whom I explained the situation and copied the correspondence. He found the company and contacted them and apparently their MD was very rude to him, he got annoyed and referred them to the Chinese equivalent of trading standards, 3 weeks later I got my VFD's with a grovelling apology FOC! Real result. Not a normally achievable resolution but very pleasing, subsequently the supplier has contacted offering to supply a coat rack, shoes and other stuff FOC in return for a positive review! I have been waiting for the triads to knock on the door ever since!


Thread: Part built Allchin 1.5 inch
14/01/2019 13:45:30
Posted by derek blake on 13/01/2019 19:50:33:

If anyone gets anytime could some direct me to a picture or video that would explain how the steam travels around the Allchin cylinder block and how the holes etc do there job.

I’m keen to learn all I can about what I’m building and how it should work.

Regards Derek


I couldn't find easily a video of a traction engine cylinder steam flow or a decent drawing (and don't have Jason's excellent CAD skills to be able to draw one!). Niether do I have direct experience of the Allchin cylinder so have tried to put in words a general description of how steam flows from the boiler to the chimney, hope it makes sense!!

Traction engines, particularly English ones do not normally have a dome to collect 'dry' steam from the boiler like a railway loco. The dome on a loco provides a space where steam collects and is drawn off for use that will hopefully not contain entrained water. So on a traction engine the cylinder casting usually performs this function. The casting is generally hollow around the liner so steam gravitates from the boiler barrel into the the space in the cylinder casting around the cylinder bore, this achieves 2 things, it gives a space seperate from the boiler barrel for the steam to be drawn off for use and because the steam surrounds the cylinder bore (in your case liner) it keeps the bore warm reducing condensation of the steam inside the bore when the engine is running. As you are fitting a liner to create the steam space in the cylinder casting and this space will be directly connected to the boiler and at boiler pressure the seal between the liner and the casting needs to be leak free. Any leak can either get into the bore via the end covers bypassing the slide valve which will lead to reduced or non existent performance or will be blowing to atmosphere! Steam is then taken from the steam space via the regulator to the valve chest via drilled or cast passages. The regulator is arranged so that the high pressure (boiler) side acts on top of the sliding regulator valve, so keeping the regulator on its seating face. It is a good idea to make the regulator port under the valve a pear shape so as the regulator is opened the area of the port exposed to high pressure steam progressively increases, this makes the engine easier to control. The passages for the regulator must not break through into any other passages! Once the steam is in the valve chest it is directed to each end of the cylinder by the valve. The steam ports (outer two ports) and the drillings to the ends of the cylinder again must not break through to any other area or drilling. The exhaust port (wider, centre port) is connected to the steam outlet flange for the blast pipe on the exterior of the cylinder casting again by drillings or cast passages and again these must not break into any other passage or area. So you have four areas that must remain isolated from each other within the cylinder block, the high pressure steam space around the liner, the regulator passages and valve to the steam chest, the steam ports to each end of the cylinder and the exhaust arrangement. You will also likely have cylinder drains which are drilled directly from the external boss where the clave will be fitted to the bottom of the bore and usually a steam take off for the steam blower that will be drilled from a point on the front face of the cylinder 'block' directly into the high pressure steam face surrounding the liner (with your engine it will probably turn 90 degrees down and connect with the space in the saddle.

1000 words when a decent picture would do!

As to piston material, bronze as Jason said should be fine. Remember 'technically' the piston does not run on the liner as it is supported by the rings although in practice that is a moot point. Full size generally have cast iron cylinders and pistons, another example of a material running on itself if you like.


Thread: Vertical Boiler Fittings
14/01/2019 12:44:11


Whilst lagging is important and will have an undoubtable effect on overall rate of steam production it won't make your fire burn any better. Personally I think your experiments have followed the right route so far and if you can boil water and make some steam without lagging then when you fit lagging you can be confident it will boil harder and make more steam. Twisted shim in a tube or two is not a bad idea as it will slow the passage of hot gas through the tube allowing more heat transfer. It's worth bearing in mind that with a traditional loco type boiler the greater proportion of heat transfer to the water takes place as direct radiant / conducted heat from the fire through the firebox sides and crown than from flue gasses through the tubes. Some American design traction engines also had 'wet bottom' fire boxes to give another surface around the fire! Your activities with firing are very interesting to follow, giving some direct practical experience rather than theoretical speculation.

With the engine; why not start with the 12mm bore version and follow up with a 24? I am sure your boiler is well able to run the former and most likely the latter, it might even run both!


Thread: VFD recommendations
13/01/2019 22:27:29
Posted by john fletcher 1 on 13/01/2019 16:32:05:

Peter F, have a look in your inbox I sent you a PM last week re inverters. Seems to be a lot of theory here, I thought what Peter wanted was to hear from some model engineers who have practical experience of what to buy. I'm not sure regarding dismissing those inverters made in China, most Model Engineers just want to be able to power up a three phase motor without all the trimming which Industry might require. Also, I think a lot of apparatuses, component,, tools etc parts with British and European sounding names are actually made PRC, think of VW and Landrover. John

Well I am with John on this. My electrical tuition was about 40 years ago, never really sunk in, never really had any interest in it! Consequently I have a base underpinning knowledge of electronics which gets me by but no real ambition to expand or develop it. All I wanted when I got my mill that has 3 phase motors is to get it running from a single phase 240v supply. I bought a couple of the Chinese Huangthingamyjig inverters from e Amazon for less than £90 ea. Connected them up, switched on and for a year they have been doing exactly what it says on the tin (having written this they will probably go bang!). Programming them was a bit of fun but plenty of resources on YouTube and regarding the pot range on the speed control some great feedback on here. They were the means to an end - getting the machine running and cutting metal, nothing more than that! I am very happy with them as they have done exactly what I want. Yes I could have gone more expensive (between 2x and 3x the price I paid) for European versions, yes they may be better built with better quality gizmo's and with greater programming flexibility and more functions and they probably would last longer and have more local support / warranty and possibly repair options. Mean time however I have an extra £200 - £400 in my pot for tooling, equipment and materials to push my project on. The VFD's were just another step towards a bigger project, not the project itself!


Thread: More help please
11/01/2019 00:25:50


When I cut my traction engine gears which were quite big and a mistake would be costly in both time and material I gave myself a check to make sure there were no issues. Clamped a square to the table against the edge of the gear (gears were parallel to the table) and went round and scribed a line at every division. I then clamped a scribing block to the table lined up with the first line and checked each time I advanced the gear that the tip of the scriber lined up exactly with my previously scribed lines. Probably took an hour on the biggest gear to set up but it saved me 2 mistakes due to brain fade over the 6 gears. However focussed and organised you think you are it's very easy with the boredom of winding handles to get distracted


Thread: Part built Allchin 1.5 inch
11/01/2019 00:06:44


Well done. Excellent progress. In less than 2 weeks you have gone from looking for someone to machine the cylinder for you to being almost halfway there. That includes overcoming the issue with the dodgy casting for the liner and sourcing a replacement and a bit of out of the box thinking as to how you can overcome the limitations of your machine capacity. I bet that's a lot more satisfying than paying someone else to do it and the bank manager will be happy too!

The really great thing about this forum is seeing people achieve things with a little advice they didn't think they could do. Well done indeed.


Thread: boiler blowdown
08/01/2019 18:02:00
Posted by Philip Burley on 08/01/2019 09:45:34:

Thanks for the help , I have a working Tich with a blow down valve , but I have acquired a larger boiler that I would lie to experiment with . It doesn't have a BD valve . If I try to silver solder a bush in now is it likely to ruin the boiler ?

Probably! Unless it is a brand new never been steamed example that is clean. You may get away with it then if you have a torch that can localise the heat mainly to the area of the bush.


Thread: Part built Allchin 1.5 inch
07/01/2019 22:56:33


Ooops! Sadly a hazard of the hobby. I don't think I would bother with another casting but get a lump of cored bronze of the right proportions and chew it out of that. You can get cored bronze in various O/D - I/D combinations and it will almost certainly be cheaper than a casting from a model supplier. I have bought from metals4u in the past, they sell by the inch. Doubtless there are other sources. I think I would bore the block first and then turn the liner to suit, needs to be a good fit so steam can't leak from the anulus, you probably need around a thou to thou and a half interference fit on that size.


07/01/2019 19:51:58


Just a thought, when you set it up try and clock it to the saddle radius so you ensure the bore is parallel to the boiler and square to the crank. When I did my 6" I had the luxury of using a horizontal borer so I was able to machine the saddle radius and the bore at the same setting guaranteeing they were parallel. We had the problem with my mate's full size Avelling which had a new boiler and the boiler maker didn't get the cylinder seating rivetted on true - lots of fun trying to correct that! Good luck, you will be pleased you did it when you have done it lol.


07/01/2019 11:00:18


Given the 'non critical' nature of the annulus if you used Jason's 4 lobed method you could always use a small rotary burr carefully and gently after to clean down the high spots if you are concerned re any reduction of CSA.


Thread: Commercial boilers
07/01/2019 09:58:52


I sent you a PM.


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