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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: 8mm live centre
14/11/2019 00:07:11

I feel very old now! When I did my apprenticeship live centres were about as common as rocking horse droppings! We had dead centres and a tin of tallow. I think I would stick that point in my boring head, spot of grease and off we go, if it's only one rod. If it's a run of them, ok it might be worth the effort.


Thread: Part built Allchin 1.5 inch
27/10/2019 20:57:26


Unfortunately you will have to persevere here and get the tap out as 3 studs on a 4 stud PCD will equal a leak! The diamond dental type burrs come with some very small points but you will need a steady hand! If you can nibble the centre section away the threaded sides usually drop out. 10ba is a bit tiddly though!! Good luck.

I tried Alum once didn't touch the drill I broke, obviously the wrong sort of Alum!!


26/10/2019 18:11:52


Screwed or studded, it won't be a push fit. With changes of temp and pressure nothing on a boiler / steam system will be a push fit.


14/10/2019 23:34:48


If you have a constant blow up the chimney both the regulator and the valve are probably letting past a little. Try a smear of engineers blue on the face of both and slide them across their relative port faces and see what marking you get. This will indicate if the valves are contacting the port faces properly. If you don't get good marking try blueing a flat surface such as part of the lathe bed, surface plate (even a small piece of plate glass) and rub the valves over, scrape gently any high spots until you get a good marking right across the surface, then reblue the valves and try again on the faces. You can address any high spots on the faces in the same way until you get good all over contact.

Failing that you can try lapping the two faces together with a mild abrasive (eucryl smokers toothpaste powder mixed in a slurry with water is a good mild abrasive). As its water based its easy to remove too.

On the globe valves 90 degree ones are reasonably easy to make, in line ones are a little more complicated as you need to drill the passages at an angle. I can't remember where I have seen drawings for them, you might find some on here with a search. Or you could try steam they do various sizes at reasonable prices and I have used a couple in the past that have worked fine.

You are getting there now! Won't be long before you can light up!

All the best,


Edited By Paul Kemp on 14/10/2019 23:37:42

Thread: Electric Traction Engine
08/10/2019 21:48:59


In your case you can make the gland the bearing, just make it long necked with a step and fit it in the cover. Cover can be anything then, ally of you want! The gland isn't going to have to do much sealing after all with no piston on the rod.


Thread: Live steam models Burrell Metric or Imperial Drawings
06/10/2019 22:14:27

What is the majority of your tooling? Not necessarily just machines but drills, taps, reamers, milling cutters, micrometers etc. If you are just starting out that won't matter as you will have to get it anyway. There is no rule to fit a bar pressure gauge to a metric one and a psi to imperial, so who will really know.


Thread: Question from a customer
06/10/2019 22:08:38
Posted by Robert Atkinson 2 on 06/10/2019 16:34:46:

As to vacuum gauges not being made for more than 1 bar, there are plenty, evey vacuum braked train has at least two and they used to run at 21". Brake cylinders also work on differential pressure between the vacuum developed in the train pipe to hold the brakes off and the atmospheric on the other side trying to put the brakes on!


Not on this planet. The maximum differential you can get with a vacuum is dictated by the local air pressure. This is variable but at sea level is about 1Bar, 14.7 PSI, or 30" of mercury. (Hg) The brake gauges are 21" of Hg not 21 PSI.
30" hg is 407" of water so that is the absolute maximum you can suck fresh water UP with a pump about 30 foot in practice.

Robert G8RPI

Edited By Robert Atkinson 2 on 06/10/2019 16:50:18

Robert, good point well made! I was thinking inches (as I put the symbol) just not enough for an atmosphere! Did cause me to do a quick bit of research though and stumbled across an article from an American University regarding absolute maximum vacuum / minimum pressure where he was claiming -20 atmospheres? This was linked to raising water up trees and another reference to a round board being towed behind a space shuttle that made atomic spacing 10 times smaller giving a 10 times better vacuum. All too much for me!


06/10/2019 15:51:06
Posted by fizzy on 06/10/2019 15:22:29:

The way I thought about it is....if the boiler were just a strong sealed container (which it effectively is) with water in it and heat applied, the water would turn to steam, the pressure would go up. Let it cool down and the pressure comes down to exactly where it was when you started. Nothing can have changed. The only difference when using it for real is that there will be less water in it when it cools down, assuming no more has been added. Ive tested this with a smaller boiler with no clack, running the water level down whilst maintaing 40 psi driving a D10. Closing the steam valve and after cooling there is absolutely no negative pressure that I can detect.

Depends how you try to detect "negative" pressure. It's differential pressure between outside and inside you need to see and that would really need a manometer to determine.

As to vacuum gauges not being made for more than 1 bar, there are plenty, evey vacuum braked train has at least two and they used to run at 21". Brake cylinders also work on differential pressure between the vacuum developed in the train pipe to hold the brakes off and the atmospheric on the other side trying to put the brakes on!


Thread: Electric Traction Engine
29/09/2019 11:02:09


Most full size engines fall into either the three shaft or four shaft configuration. The number of "shafts" in this description includes the crank and the rear axle. Probably the majority are 2 speed but some are 3 speed and fewer 4 speed. I think I can generalise and say pretty well all 3 shaft engines were 2 speed and four shaft 3 speed or more. All sorts of reasons for a fourth shaft and some advantages such as the ability to incorporate the diff on the third shaft rather than the axle which allowed the unit to be smaller. Also there were considerations with springing, ie if the axle moves on springs then the mesh of the gears will change. Various manufacturers had different ways of accommodating this. Avelling rollers used the four shaft method with low speed as a sliding gear on the outside and "high speed" as a sliding gear on the inside (between the horns in the crank pit) this allowed a greater reduction between crank and axle using smaller gears up to keep the road speed low suitable for rolling. Typically slow was dead slow and high was a bit faster than slow! When working low speed would be used and when travelling between jobs high speed (except for hills - rollers with smooth rolls especially didn't have a good grip on the road and many came to grief). So if you look at full size rollers with original gears slow is almost always very worn and high in pretty good nick! 4 speed engines were usually road haulage engines to give greater flexibility of speeds while pulling heavy loads. Most agricultural engines were 2 speed but as they got larger with exception of ploughing engines tending towards general purpose engines some were 3 speed.


Thread: Getting to grips with Autodesk Vred
28/09/2019 21:11:16


Brave man on both counts! I struggle with this computer based drawing stuff, notepad and pencil and sketch as I go is about my level! Also had a few Renk and Reintjes gearboxes to bits in my time and some of them have some really fiddly bits and that is in full size! I have an enduring memory of a hydraulically fitted input flange that we pumped up to pressure (several hundred bar) with no movement whatsoever. We left the pressure on to see if it would co-operate and I went out of the workshop for a break and as I opened the door it let go with the loudest noise I have ever heard! Bent the restraining plate designed to catch it! I reckon the control valves for the clutches will be a challenge scaled down! Good luck and will be interested to see your progress.


Thread: Part built Allchin 1.5 inch
28/09/2019 18:02:02


Short answer is no, not to the extreme ends, there needs to be a little clearance. Much longer answer explains why but trying to keep that short too, most traction engines have top suspended links which amplifies geometric error in the motion and is fairly inefficient, rail loco builders went to great lengths to support the link on trunnions on the vertical centre and the centres of the trunnions just offset from the centre line of the slot to give better valve events but even that does not overcome the fact the link is oscillating and not just rocking so it slides over the die block slightly and through the stroke of the valve the die block will slide towards the extremity of the slot. If you arrange your reach rod and reverser set up so it is already jammed against the end, it has nowhere to go.

That is probably not very well put and about as clear as mud! I am sure others can explain it better.


28/09/2019 00:03:17


Not much wrong with that! Nice and regular impulse on the crank. Well done. Little challange for you, see how slow you can get it to run on your 20psi, good slow running is harder to achieve than having it whizzing round and a very good indication of how good your valve timing is. I reckon you will get that just creeping round!


Thread: Electric Traction Engine
23/09/2019 00:14:19


Ont the rivet snaps, beware, some commercial snaps do not have the cup detail that matches the rivet head! I have various snaps from various sources, one pair if you put a round head rivet in the snap does not fit down nicely over the head and if you use it you get a nice round bit in the middle and an ugly flat ring round the edge! Worth checking before you get a mess!

On the tyres there are three major companies and several smaller ones offering vulcanised tyres for traction engines. This is done in one of two main ways, either vulcanising the rubber which is would on as thin strips directly onto the wheel (if not straked) and then chucked in a giant autoclave. The other is to make a "press on band" that fits over the original steel strakes and then vulcanise onto that. If you go either route you have the choice of smooth circumferential rubber or some companies will mould / cut strakes into it. Believe me it's not cheap! I had my 6" wheels done with smooth tyres by a very nice man but it was still over £1k! Some full size rollers have had rubber faces vulcanised on, that goes into the 10's of 000's! The tractor type tyres are colloquially known as quad tracks. Sections are cut from the tracks using a large angle grinder (they have wire running through the core of the rubber!) and then the sections are bolted through the rims. Usually it's easy to spot ones done like this as you can see the bolts. It's a very messy and tough job to do the latter although a lot cheaper!

All the best,


Thread: Part built Allchin 1.5 inch
22/09/2019 23:59:32


Try twisting some PTFE tape (plumbers use it!) into a string and then wind that round the stud (clockwise) then screw the nut down on it, any that extrudes out past the profile of the nut you can trim off with a craft knife. It's a relatively low pressure so should do the trick.


Thread: Painting and Finishing
06/09/2019 20:59:35
Posted by JasonB on 06/09/2019 19:21:04:

I thought that Neil's models weathered naturally due to the long time it takes him to finish onedevil

In contrast Jason, your's should be covered in finger prints where the paint has not had time to dry...........wink 2

Thread: Electric Traction Engine
06/09/2019 16:26:05


Absolute truth of the rims is not really necessary, they don't rotate fast enough for the eye to discern if they are slightly egg shaped so you shouldn't need to machine the external face. Is important though when spoking up there is as little side to side "wobble" as possible as that is noticiable. I doubt you will find a full size wheel that runs perfectly true. If your rings are rolled well that should be fine without machining. The backing rims for the rubber tyres over the strakes on my Ruston were pulled to shape between two heavy rods mounted vertically in a vice, welded and then adjusted for round against a scribed circle on the bench!

One thought on silver soldering your rings is you will need a lot of heat for that job, welding I think would be better. Needs to be welded in a sequence to minimise distortions though. Starting at one point and following round could give you a very funny shape.


Thread: Why does the micrometer have a second knurled segment
05/09/2019 21:57:45
Posted by Chris TickTock on 05/09/2019 21:30:41:
Posted by David Standing 1 on 05/09/2019 17:39:07:
Posted by MadMike on 05/09/2019 14:42:44:

Not wishing to be controversial, but is this a serious question?

I have suggested useful reading material to Chris on more than one occasion, he has not responded.

Book 6 in the Workshop Practice series, Measuring and Marking Materials, by Ivan Law, would answer this question too.

The preferred option appears to be to bombard the forum with questions instead.

Thanks MadMike, I will endeavor to make all future posts at your elevated level.



With the greatest respect I have followed many of your question posts and the answers which seem to be perfectly valid. However the way your responses read to me seem to dispute most suggestions as not appropriate according to your answers already gained from your valued advisor. I am sure you do not really intend to come across as I interpret your responses and there is nothing wrong with questioning to properly evaluate a method or process but the way you do this perhaps does not encourage people to respond?


Thread: Dumb question from a none driver
05/09/2019 21:34:25
Posted by mark smith 20 on 04/09/2019 20:00:08:

Just an update i yesterday received a receipt in my name as owner so with the facebook conversation and screen shots off the phone showing the seller in the conversation i feel i have enough proof of purchase.

The V5c change of keeper has been done online.

Initial insurance my son took out on the van was wrong due to mix up between comparison site and insurance company not having me as owner of vehicle down on policy and not being covered for commuting to and from work.When contacted they said my son would have to either become the owner or cancel policy .So cancel policy it was.

Cancelled insurance today (within 14 day cool off period) £72 refund given on initial deposit.

Took out new policy today which has me as owner stated on the policy and my son as the keeper, and covers for commuting to and from work.

So everything seem alright i think.smiley

thanks everyone for all the advice


Thanks Mark, glad you got it sorted and pleased what was refused regarding the wife years ago is now possible if you go to the right place. Also pleased my anecdotal evidence proved possibly useful as regards your first policy.


Thread: Fixed steady use
03/09/2019 21:07:31


Simple way I think is make an adjustable holder for a clock that fits over a good running centre in the tailstock. Tailstock is on spindle centre, so set your bar up with the chuck nipped up and bar running true at the chuck. Adjust your steady lightly at t'other end of the bar and run the clock on the centre round the periphery. Adjust the steady fingers until the clock shows the bar running true (remember you are rotating the clock around the bar, not the bar against the clock). Go back and fully tighten the chuck jaws against a clock in the normal way so the bar stays true in the chuck. Job jobbed.


Thread: Dumb question from a none driver
02/09/2019 07:45:03
Posted by Pete Rimmer on 02/09/2019 01:16:06:
Posted by Paul Kemp on 01/09/2019 22:45:57:

Apparently this is a legal principle of insurance that you can't insure something against loss unless you are the legal owner and it is you that will suffer from a loss.


My wife's car that I bought new is registered in my name but my wife is the only driver and she has a fully comp policy on it. It was done like this because I bought it for her as a birthday surprise. The insurer knows this and is perfectly happy with it. I am the owner, she is the insured.

Maybe things have changed now, I remember being pretty annoyed at the time and couldn't understand what the problem was. She tried half a dozen or more companies, all gave the same answer. She also still had contacts in the insurance business as she used to work for a broker so we contacted them and they couldn't help either. Doesn't explain the trailer which was only a couple of years back although I only tried 3 companies for that. Would be interested to know the definitive position.


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