Member postings for Paul Kemp

Derek,

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.

Paul.

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

Ron,

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.

Paul.

Chris,

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?

Paul.

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.

Paul.

Larry,

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.

Paul.

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.

Paul.

Derek,

You look to be making a fine job of that, up and running next year?

Just to show I do make stuff! Couple of shots of my Little Samson 6" scale from last year to spur you on! It has advanced a bit since these but a paying job has hindered progress lately!

Hoping to get it finished over the winter!

Paul.

I don't know if these points have been covered already because I started to lose the will to carry on reading! However;

A good few years back I decided to let my wife use a car that I own but had not used and was in storage and wasn't insured or taxed. She tried to insure it as we thought it would be good for her to gain some NCD in her own right rather than as a named driver on a policy I took out. This proved impossible as no insurer would offer cover unless she owned the car! Situation very similar to your son as I was effectively lending her the car.

Fast forward to a couple of years back and I borrowed a mate's trailer to do a long distance pick up of a machine. He told me he didn't have the trailer individually insured and was worried what would happen if it became a total loss. I checked with several sources including my own car insurer. I was told I could not legally insure said trailer as I had no insurable title in it. Ie if it became a total loss as I didn't own it the loss would not be mine and it could only be insured by the legal owner! It was confirmed as long as it was connected to my vehicle my vehicle insurance would cover any liability or damage I caused with it but would not cover the value of the trailer.

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. Interesting that in the case of the trailer I would have suffered loss as I would have had to pay for a replacement, but apparently this doesn't count!

In light of this it might be worth your son checking the insurance he has arranged and that it will cover the loss of the vehicle or damage to the vehicle as he doesn't own it.

I have no idea how this rule applies to the likes of lease / buy agreements where you pay monthly to use the vehicle or to the HP / Loan scenario other than perhaps under the terms of the agreement you are liable for the whole debt so there is a quantifiable personal loss? Maybe someone knows the definitive answer to this? I can't see how it works with a hire car either as you don't buy the car for a week!

The OP may seem to have posted a simple question but I think the answer is not so simple despite some comments to the contrary.

Paul.

Derek,

Sadly you ask the unanswerable question! Correct answer is tight enough to do the job but not tight enough to strip the threads! Which you won't find particularly helpful I think?

In definitive terms I only know 2 ways to tighten a threaded fastener to achieve the correct tension. First is using a torque wrench which isn't going to be helpful in these small sizes as friction will play as big a part as anything else. Second is by measuring the bolt stretch, this is a much more reliable method than torque on the nut to achieve the pre load but again impractical in this size / application. There is a third way of torque and turn which is a combination of the two main methods and a bit more accurate than torque alone where a set torque is applied to seat the fastening and reach a predetermined frictional / low tension condition followed by turning the nut or bolt a calculated number of degrees to bring to full tension, this is worked out on extension required relative to thread pitch, again not really helpful for you.

So all you are left with is feel! Getting used to the amount of pressure you can apply to the spanner or socket being used. If you are not confident you can 'feel' how tight you are doing them up than I suggest you get a piece of copper the same thickness as the barrel and drill and tap the same size as you are using (do several holes). Drill a bit of scrap steel clearance and put a piece of the jointing you are planning to use between and use one of your bolts. Screw it in so it is seated firmly and then place the spanner on it and turn until you strip the copper thread, noting the angle it passes through. Half the angle would be a good guide to the maximum you can tighten the bolt without compromising anything. That is about as scientific as you can get in practical terms if you are not confident with your feel. It's worth noting what Jason said earlier and making sure the male thread is a good fit in the hole, if it's too small and there is too much clearance all the load will be on the thinner crests of the threads and they will strip easier than if a good firm fit.

its worth developing a sense of how tight is tight enough on these small fastenings and odd (non ferrous) materials for elsewhere on the engine. Good luck.

Paul.

Edited By Paul Kemp on 25/08/2019 23:13:14

I thought I made that clear by implication! I would judge the load on the studs, look at the existing thread engagement and if 2 full threads or more and the stud loading was suitable wouldn't trouble further. In Derek's case he also has half a thread in the extra thickness so it's going to be better than just the barrel thickness anyway. With the csk insert it relies on pure tensile strength of the silver solder? Putting heat into a completed boiler and given the stiffner is silver soldered inside anyway the joint of which will be affected by nature of heating on the opposite side to my mind is not the best overall plan. But each to their own! Was merely pointing out if the numbers stack up there is no great need for a radical solution and any practical boiler inspector should be capable of assessing the risk and likelihood of failure and adequacy of strength. If it doesn't calculate I would look to use carrot bolts as per full size, thread some fuse wire through the holes and fish out the 12mm hole, wrap in the threads of the bolts and send them through the 12mm hole thread wire through corresponding holes in saddle, seat the block, pull the bolt through, grip with tweezers or needle point pliers, remove fuse wire, thread on nut and tighten, trim off spare thread. If you need to relieve the step caused by the existing stiffener use a dental burr in a dremmel from outside. Good enough for full size, good enough for me!

Paul.

Derek,

Can't help feeling there is some "over thinking" going on here. Obviously what you have now is not the design intent in terms of depth of thread but;

i don't know the thickness of the boiler barrel or the intended operating pressure. Given that when a screw thread is tightend the majority of the load falls on the first two threads I assume the thickness of the barrel alone will give 2 threads engagement? If you take the area of the cylinder exposed to boiler pressure (12mm hole?) and multiply the operating pressure by that area and divide that by the number of studs you will have the approximate tensile force on each stud. I think you will be surprised by how low that is. Any mechanical forces generated by the piston against the crank will be mainly shear forces so for the purpose of this question can be disregarded. Back in the days of LBSC several of his designs had boiler fittings attached just by a couple of 6ba screws tapped into the wrapper!

So, ideal? No, Compliant with the design? No. Probability of failure? I would say just from the info in your post, low.

Talk to your intended boiler inspector first.

Paul.

I am not sure what you are trying to achieve or prove here? First off I would be doing your tests using a four jaw direct on the spindle flange and verifying diameter over about 4" length from the chuck that you can turn parallel. That will tell you your headstock / bed alignment is good. Once you have confidence that is correct you can then revert to testing your collets. As others have said the overhang on the collet chuck is not ideal.

On your other point re the bearing fits and preload I would polish the spindle to get an acceptable sliding fit. With bearing inners and outers tight in their locations achieving an accurate preload is going to be impossible.

Finally trying to achieve micron accuracy from such a machine is I think beyond reasonable expectations. If you want to maintain those sorts of figures then the lathe needs to be in a temperature controlled environment and the surface to which it is mounted be free from any possible effects of humidity (wooden bench will move with differing humidity and water absorption)

Paul.

My 040 battery loco runs fine on its C5 motor. Used to pull my kids round the club track and also a car load of kids up and down my portable track at fetes all afternoon without missing a beat on an old Capri car battery!

Paul.

Dave,

i have been on a full size loco fitted with superheaters that had water carry over through the level being too high and that ran away or rather carried on when the regulator was closed. Solution was to wind into mid gear and it stopped but there was still pressure on the steam chest so yes it can happen. Not sure on a miniature it would run very far though, as you say the volumes are small but still in proportion I guess. Any driver that couldn't deal with this is not much of a driver though unless it was pole reverse in which case he may need a bit of help to pull it back to mid gear from the fireman!

Paul.

Is the boiler clean? As previously mentioned what is the water quality? Carry over is not unheard of as steam demand increases. If you imagine the rate you are taking steam off the water if the demand is high then you get vigorous bubbles at the water / steam interface and the more steam you need the more likely it will pick up water with it. If you search spirax sarco on utube you will find some very good videos taken inside an industrial boiler of what happens. Keeping the boiler clean and the TDS down may be all you need.

Paul.

I would guess it's little about the risk of actually making a claim and more about the cost of any claim that is made. Given the disparity in purchase price between an ICEV and EV the financial risk of claim is increased as it seems most vehicles can be written off these days for a moderate sized dent! Writing off an EV is therefore going to cost substantially more.

Paul.

Commercial technical manuals these days are so full of caveats and advise to use gloves, boots, hard hats, not to drink the oil, wear ear defenders etc etc that extracting the actual information you really need is next to impossible! Sadly the expectation now is that the documentation will be used by a child, the office secretary or apprentice and not by a qualified technician that should already be aware of the safety considerations.

Paul.

Hi Derek,

Good to see you are still pushing ahead. Traditionally model injectors seem to be rated in fl oz per minute. So in choosing a suitable one look at the volume of water in your boiler at running level and compare to the volume delivered per minute of any proposed injector.

General comment I would make is a lot of models seem to have injectors that are over capacity and will raise the level in the glass from empty to full in short order, some within a minute! While that may be desirable for some it is not very kind to the boiler as a large quantity of cool water squirted in by the injector knocks the pressure back which puts quite a significant temperature / pressure stress cycle on the boiler. It is kinder and more efficient to have an injector with a lower delivery that can be left on for longer if needed but if used regularly for smaller amounts you can control the pressure water level much better and do not have such wild fluctuations.

Others may well have different opinions but I have never come across a full size boiler yet that you can take from the bottom to the top of the glass in a minute or two! Generally the injectors are matched to balance or slightly exceed the water consumption at full load. Often on railway loco's you have two injectors, one having a higher delivery than the other to better match operating conditions.

Paul.

Michael,

Very nice I am sure and a fantastic piece of kit but I am with John on this one and such an instrument for what I do has no place in my shed lol.

Building a half size version of an early 1900's traction engine and following the prototype where limits and fits were to the closest 5 thou or 1/16" on the cast gears I have no need or desire to work to the tolerances capable of being measured by this!

A common mistake by new builders of steam engines is to make everything to too close a fit and consequently they are so tight they won't run! I have a 5" gauge loco built by an early mentor of mine now long sadly gone which is now 58 years old, on its 3rd boiler and has done 1000's of real miles over the years giving rides on a portable track. Apart from the boiler replacements it has had one set of piston valves and a couple of bushes in the motion to my knowledge and that's it. Yes it clanks and bangs a bit (as does a full size if you get the chance to ride one) but it still goes like the proverbial rocket and I consider it now properly run in. Everything on it was measured with an old manual Moore and Wright vernier and I think it's service record shows that was plenty good enough.

Dont get me wrong, as a time served fitter turner I can make things fit adequately for purpose but I am not going to spend time working to limits that are not required for a decent practical end result. Half a thou is as small as I practically need to measure.

Paul.