Here is a list of all the postings RRMBK has made in our forums. Click on a thread name to jump to the thread.
|Thread: boiler design verification|
Thanks Duncan . I'm not using LBSC out of choice but because it is the closest to the dimensions I am looking for. We have already discussed with BI, the need for changing all direct threads to bushes, increases in safety valve dimensions and firebox crown staying, so the original LBSC design is largely changed anyhow.
If I can get a copy of the necessary design calcs I am already sort of 50 % towards creating a new design as I have the original loco boiler drawings from the NRM . so its beginning to look as though getting a copy of the aussie code and doing the calcs for a copy of the original design and dimensions is going to be the simplest way forward.
Its just that both my BI and I would feel happier if we can get some independent verification of the design and calculations without it costing an arm and a leg, which is why we keep coming back to the grandfather rights vested in some of the older designs , poorly designed as they may be.
PS just looked at PD 5500 - £ 1800 a copy - £ 900 if you sign up for membership of BSI !!!!!!!!!!!!!!!!!!!!!
Thanks Duncan. I, like Steven have struggled to find a copy of the codes other than by outright purchase, which it may come to. I am happy to try and do the calcs if I could get the information to confirm I am doing it properly and this sounds like it will provide that.
To explain a bit more , The design I have in mind has almost exactly the same dimensions as a standard LBSC boiler in terms of length diameter etc, however LBSC's design has a firebox that fits between the frames and the design I am looking at uses a wide firebox sitting above dropped frames. in principle this type of firebox should be inherently stronger and easier to stay but obviously does not constitute an approved design by virtue of grandfather rights. The LBSC design is also reputed to be difficult to fire because of the narrow firebox and hopefully this wide firebox may help to resolve some of these problems.
I would also like to consider adding a baffle ( brick arch type within the firebox) to improve gas flow, which again would be an alteration to the original.
Jason, - Thanks- I will look for those spreadsheets - in this instance 100psi is OK . Grateful for any links you may have.
My BI is fully on board, but quite understandably has asked me to consider getting independent calculations to confirm the design basis.
The boiler test codes accept that previously published designs are considered to be proven and safe even though they may never have been subjected to calculated stress loading.
What is the position if one is working on a model that is not a published design, but a replica of an original. All the boiler dimensions are available for full size and it is reasonable to alter the tube numbers and spacing in the model to accommodate suitably sized tubes that match the design of a similar sized boiler of a published design.
My question is how would one go about proving the design is safe and getting the boiler inspector to agree to that ? The B I can reasonably expect one to provide stress calculations to demonstrate this, but these are not easy to do for an individual, and would cost an arm and a leg to get them done commercially because of the liability implications.
Any thoughts please ?
|Thread: Holbrook 10B|
Hi Pete. I have created an album entitled Holbrook 10B . hopefully you can access it and get a look at the lathe.Enjoy.
I will try and post a photo but it will be a fortnight or so as I am off on the piste tomorrow, and as I have never posted a photo before it should be an interesting experience!! The old e.bay listing is the guy I got the vertical slide from.
I was as intrigued as you as to why virtually nothing comes up on the internet, hence my posting. I do have the original sales details and I bought it from a guy who had got it from the original owner but just passed it pretty much straight on.
Clive- thank you , that info is very interesting and probably explains why it seems that so few were actually produced. Having had an excellent south bend toolroom under drive before this, and given that the boxford is cloned from the SB; I can certainly confirm that these really are - " Boxford done right" It really is a joy to use.
I do have the original manual, and one of the reasons for the originl post, was because it is a bit vague about lubrication of the main headstock bearings, and I was hoping someone else out there may have found an easy solution.
A few years ago I bought a Holbrook 10B 10" swing 20" centres lathe, believed to have been bought new aroung 1983/4; to replace my ageing south bend underdrive. The south bend was a very good lathe but this is even better, much more rigid, metric & imperial gearbox, metric & imperial direct reading dials . However Tony's lathes web site doesn't make any reference to this model, the Holbrook forum seem to take the view that they dont exist , so what is the story behind them? I seem to recall them being advertised or featured in ME in the 1980's but certainly weren't within my budget then! Mine is number 18 and I bought a vertical slide( the only accessory mine didnt have ) from a guy who was selling one numbered in the 20's if i recall. So anybody know anything? how many were built, were they a flop? if so it must have been price because the quality is great. The best bit for me is that the nose is exactly as per the south bend so all my chucks collets etc fitted directly on.
Hopefully somebody can shed some light .
|Thread: TRACTION ENGINE CYLINDER TO BOILER SEALING|
I am looking to seal the same joint on a 3" Burrell which doesn't have the raised pad . I have boss white on stock. is this suitable instead of foliac ?
|Thread: Foam parts storage|
Thanks Everyone for your advice, the pick and pluck has done the job wonderfully and there is an added bonus for a tightwad like me, - if you take all the bits you have " plucked " out and stick them to the bottom of your box, or a baseboard; with spray-mount adhesive you get to use all those pieces as an extra new section of pick & pluck.
Thanks once again.
|Thread: Name plates|
I made up a number of nameplates using the " press n peel " stuff mentioned in John Baguley's website . These were for makers nameplates for a small 2.5 Gauge loco but the definition turned out fine and once the background was painted and the upstand polished, really looked good. There are a number of tricks to getting the photo etch film clearly defined without smudging but once you get the hang of it i suggest the process is very effective. Instead of ironing the film on as many suggest I placed the brass on the iron with the film fixed on top and used a wooden wallpaper seam roller to impress the image on the plate. Also warming and agitating the Ferric solution helps. Think gentle warmth ( airing cupboard top of cylinder ) and an aquarium air pump for example. Its a slow process, a good etch takes a few days, but in my experience the end result is well worth it. Hope this helps.
|Thread: Foam parts storage|
As always a great response from great people. . Thank you all very much - I can now plug on with this years project leaving behind all the others in their usual stages of incompleteness and disarray !!
Kind regards and have a successful 2017
can anyone point me in the direction of a cheap source of the sort of high density foam used in camera cases, airline transport cases etc . I want to create some small ( 1/2" X1"x 1 " up to about 3 x 3 x6 inch cut outs to safely store some wooden patterns for the long term . I would like to get the foam first and then make the boxes from plywood at a size to suit each batch of patterns.
Also what is the generic or trade name of this stuff. I have managed to successfully cut a few storage cutouts in Kingspan type expanded polystyrene stuff but the surface finish is poor because the composition is such that it doesn't come away cleanly.
|Thread: Stirling Single|
Check out the National 2 1/2 gauge website at n25ga.org . I look after the castings stock and someone else our drawings archive. We certainly do have quite a bit of stuff and a number of castings for the Stirling single. A request in our journal Steam Chest to our members may well bring you a bit more more helpful information.
Hope this helps.
|Thread: Spark engraving pen ?|
There is definitely a design for one in ME. I recall seeing it recently when I researched some info from my archive for something else. As I was looking into the southworth duplex feed pump I guess it was about that time , I think it was under workshop wrinkles or something like that rather than being a separate article in its own right.
Hope this helps
|Thread: Boiler design|
Duncan , Brian, David.
Your posts have got to the heart of the matter. I have done the necessary design calcs in the distant past, but its something I would be very rusty on now . Similarly I have every faith and confidence in the boiler inspectors I am talking with but i feel it unfair to ask them to verify calculations for what is essentially an an unproven design. These people are after all mainly unpaid volunteers who already take on a huge responsibility to allow us all to enjoy our pastime.
Brian & Duncan " I don't see how a boiler inspector could certify a boiler is he wasn't able to assure himself that the design was safe"
Whilst I agree in principle with what you are saying, I think most inspectors base assurance of the safety of a design, as being the fact that it is a historic published design which has stood the test of time.
I suggest that LBSC is unlikely to have had boiler stress calculations done and independently approved for all of his designs but they work well enough if properly made.
I have had some involvement of Notified Bodies in the workplace and the experience wasn't particularly convincing and was painfully expensive.
I agree with David that the hoop stress should not alter with length and so modifying a current design is probably the best way to go.
I do have copies of the UK and Australian codes and both of these are very helpful publications. Follow these properly and there is no doubt one will have a safe pressure vessel.
unfortunately some numpty in a London underwriters office will know nothing about them and will rely solely on someones proof signature.
Hey ho - onward and downward to the pits of Valhalla!
Hi All thanks for the info.
I had already spoken with the inspector(s) at my club and there views were much the same . I was considering however making the boiler exactly as per the size and shape of the original but obviously different tube dimensions and layout. It was if I decided to go down this route that although I can do the calcs, the inspectors advised It would be best to provide independent verification for these and so I wondered who might do this?
If someone looked to make a boiler in 3 1/2 gauge for a specific locomotive that is not currently a published design how does one go about getting it proven ? I.e. who can certify the shell calculations to comply with NAME or southern Fed ?
If the design were to use a published design but extended or shortened the boiler barrel & tubes by say 30mm what would the situation be then. ?
I am contemplating an unusual model, although the full size boiler was as used on many similar full size locos but 10% shorter.
As far as I can tell there are no published model designs to match this boiler but there are some that are the right diameter but slightly longer or shorter.
At this stage I would prefer not to discuss what the prototype is.
|Thread: boiler fittings|
Thank you all for the information so far.
Re bronze/ brass. I was lucky enough in a former job to get the task of replacing quite a few old sailboat propellor shafts as I had the facility to machine the tapers , keyways and threads for the new ones. These were mostly bronze and up to 2 " diameter. The owners didn't generally want the old ones and if one asked nicely they would be glad of the offer to dispose of them! I've got a few odd lengths left of various diameter bronze shafting and I keep this stuff exclusively for boiler bushes and fittings . I do agree however that if the part can be removed for examination regularly then brass can be used. De -zincification too the extent where the item would fail, seems to suggest a lack of regular examination.
Nigel - thanks I will try that .
John Hancock I have machined a land on the face of the check nut and I would like to understand better why this method doesn't work as this particular fitting that does have to be in an exact location is the one thats giving me the most trouble. .
Sam I agree about Hemp & boss ! used it for so many years but it just looks so out of scale on a 1/4 x 40 tpi fitting !
Looks like I am going to have to add to the " Lucktite" shareholders dividends !!
Thanks again all and don't let that stop the thread. Others may still benefit from your wealth of knowledge and experience.
Hi gents, rest assured they are bronze ! I used the term brass to simplify matters.
I have made all of the fittings with lands for copper washers, which I have annealed and used. However, making the fittings forces me down the road of parallel threads and also to get the correct alignment of certain fittings they have a separate hex nut on the threaded portion and this allows the fitting to be fixed in an exact orientation.
I think also, I am wary of any further tightening onto the copper washers as the threads are mainly ME 32 or 40tpi which have very limited thread depth, and I don't want to risk stripping the bushes in the boiler . I am coming to the conclusion that I should screw cut the threads instead and leave them a little oversize. This method though then takes me full circle back to using ptfe tape for its thread lubricant properties, which is what I wanted to avoid in the first place.
Is it worth screw cutting onto a 1/2 or 1 degree taper? anybody tried this approach?
Anyone got any recommendations for the best jointing material to use with brass parallel thread boiler fittings. I am struggling to get the boiler with all its fittings in place, to hold the 1.5 times pressure test for any significant period of time. It appears to be just very slight seepage at a couple of the connections between the boiler bush thread and the boiler fitting ( eg gauge glass frame) threads.
Not sure about PTFE tape as I have had experience before of little strands coming off and clogging various items e.g. valves, or preventing them seating properly.
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