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Member postings for Bob Youldon

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

Thread: Bronze for cylinder
13/02/2016 11:30:04

Good morning Gerry,

For gunmetal. try College Engineering, or Macc Model Ltd.

Regards,

Bob

Thread: Re-Building a Simplex Loco
10/02/2016 12:17:00

Good morning Folks,

Jim Ewins would get all upperty at the very mention of Simplex, probably because it wouldn't fit his formulae, but I wouldn't mind a pound for everyone built and furthermore they've brought delight to thousands of both proud builders and their passengers over the years. Jim always maintained the cylinder bores were too large, well according to his calcs they probably are, but when you've only got 20lb on the clock it'll still pull; what it doesn't have is sufficient superheating surface, not helped by the asymmetric tube layout; the best steaming Simplexs I've witnessed over the years had a symmetrical tube layout with pairs of radiant superheaters.

I think today there are better designs for the beginner to cut their teeth on and my advice to anyone starting on building their first locomotive, if not already a member, join a club, listen, look and discuss before making that decision.

Regards,

Bob

Thread: How long is a piece of string
05/02/2016 17:05:27

Good afternoon Michael,

To give an estimate of the time required to build a Springbok is almost an impossibility, there are too many factors that will require considering before any sort of clear picture; a fellow member of one of the clubs I belong to has been on one since the early seventies whereas another member has the ability to turn out first class stuff in next to no time including building a 6" scale traction engine in twenty three months! The quickest I've ever turned out a locomotive was one of Don Young's 4F and that took sixteen months. I think it was old LBSC who said on average it would take something in the order of 2500 hours for the average worker, mind you he always gave instructions for his "two hour" hand pump, it takes me that amount of time to find the materials.

An old departed friend always said you don't need patience, you need grit, grit to hang in there.

Crack on Michael and it'll be in steam all the sooner. the most difficult thing is getting started.

Regards,

Bob

Thread: sealant
02/02/2016 11:13:13

Good morning,

You don't say what size the locomotive it is to be but for the smaller scales, gauge 0 and gauge 1 its possible to get away with a metal to metal joint with a smear of jointing compound, I use a liquid jointing called Heldtite, clean both faces with a drop of meths then apply a very small amount of the jointing compound. A good alternative being the brown envelope with some jointing and some in the smaller scales are using PTFE sheet, but in both cases there is the task of punching out small holes for the bolts etc. Going up to the larger scales, ¾", 1", and 1½" then the use of a gasket paper together with a smear of jointing medium will suffice considering both the temperatures and pressures involved.

Regards,

Bob

Thread: drying out of flux / prefluxing of silver solder.
13/01/2016 13:09:24

Hi all,

There's a distinct difference how the flux will perform when sliver brazing steel than when dealing with copper or brass; copper / brass / unleaded gunmetal/ drawn bronze etc, the flux will all work and react in much a similar manner and the Easyflo type flux is most suitable for the much smaller assemblies, but as Julian has said a more a suitable flux where prolonged heating is required such as boiler construction, mechanical cleaning is the norm, but not emery cloth etc, before the application of any flux. Also it is essential to reflect as much heat back onto the job whilst its being heated, the Themalite or similar block being very suitable. Steel should be treated in a very similar manner, mechanically cleaned but using a flux capable of more prolonged heating is required and plenty of it, remember flux is relatively cheap so don't skimp on it. and when silver brazing steel try to bring the job to the correct temperature as quick as possible, support the job off of the hearth on some odd pieces of fire brick rubble to allow the heat to circulate all around the job. Following any silver brazing job let it cool to black even down to a point where you can comfortably pick it up and let the job soak for a couple of hours in clean cold water, you will find the majority of the flux residue will then just rub off. One thing, avoid Borax etc like the plague, the flux when heated goes like glass and is nearly as hard, you'll spend hours trying to clean the job, use a flux compounded and matched to the sliver brazing process.

Regards,

Bob Youldon

Thread: Fusible Plugs
29/12/2015 19:17:31

Hello,

As someone has mentioned it is essential to use a material suitable for use at your desired working pressure plus a suitable additional additional excess. I would discuss the design and materials with your boiler inspector prior to making the thing. Should it be for a pressure vessel in the UK I'd suggest a look at the green book on the subject of fusible plugs. Ideally plugs should be removed for examination each year, primarily to ensure the waterside hasn't become encrusted with scale as this will act as an insulator and the fill material hasn't started to sink through the plug. I understand following the dropping of a plug the boiler should be subjected to hydraulic test.

All in all, I consider them a damm nuisance in model use but that's only my opinion.

Regards,

Bob

Thread: hand rail stanchion
03/12/2015 18:43:34

Good evening Terry,

I always fit the boiler lagging sheet temporally and carefully set out and lightly scribe the line of the hand rail also marking off the positions of the stanchions, take off the lagging sheet, drill through and it's a simple job to fit the stanchions nutting them on the back, but firstly checking that the hand rail material will pass easily through the stanchions. All that's left is to fit the lagging sheet for final.

Regards,

Bob

Thread: Class 2 Standard 2-6-0 by Don Young
24/11/2015 20:07:55

Good evening Barry,

At the Bluebell Railway there's a team recreating an 84XXX tank, have a look at http://www.bluebell-railway.co.uk/bluebell/locos/84030.html It may be of some help in respect of details etc.

Regards,

Bob

Thread: Cutting through steel/iron round bar
19/11/2015 12:02:00

Hello David,

When I first read your post I though you'd left a nought off and it should have been 160mm, but as many have suggested use a hacksaw, 24tpi X 12" blade, plenty of cutting oil, don't go at it too fast and keep your thumb out of the frame. When it comes to the larger sizes above 2" etc then a steady go with the hacksaw, turn the radio on, get yourself a comfortable stance, an 18 tpi blade, again plenty of cutting oil and away you go, it'll whizz through. My wife can't even cut bread straight, hopeless! Cutting things off straight is one of those aquired arts, me, I hate wood with a vengence!

Regards,

Bob

Thread: Steam oil delivery bore size
12/10/2015 20:41:02

Hello Fizzy,

If your lubricator is about 1/8" bore, generally the normal size for 31/2" and 5" gauge locomotives, then I'd use 1/8" x 26g copper tube with 1/4" x 40 fittings, quite adequate.

Regards,

Bob

Thread: Boiler expansion brackets
06/09/2015 21:20:18

Hello Peter,

Make up your firedoor complete on a frame and attach the the complete unit onto the boiler with a pair of studs; the backhead on the Springbok design is from .125" material so there is adequate material to accept a reasonable thread, make up a pair of studs with the thread for the boiler slightly on the tight side, make them from either drawn bronze or preferably from a piece of monel, drill the boiler right through and tap using a taper tap with plenty of tapping compound such as Trefolex, don't tap right through but leave a nice tight taper thread, wash the area clean with some meths of all the tapping compound, now anoint the threads of your studs with a good sealing compound such as Heldtite and fit the studs using a stud box, Your nice door and frame can now be fitted onto the studs, give them a dab of graphite grease and fix the frame using a couple of brass nuts and washers. Job done!

Regards,

Bob Youldon

06/09/2015 15:06:36

Hello Peter,

Many years ago I came to the conclusion the more holes you drill in a boiler the more chances you have for leakage, so these days I never fit expansion brackets, angles or what ever, Martin Evans and before him LBSC style to a boiler, now I'll always fit a couple of pieces of either suitably sized angle or pieces of square material to the frames and sit the boiler down on it's foundation ring onto the angle; it's a far easier proposition when getting the boiler level in the frames; the boiler will never jump off, it being held in place by the plethora of pipework together with the cab! It's an easy enough task on the full sized locomotive to fit brackets etc but not so simple in our sizes.

As Julian has mentioned there is the odd inspector out there who is adverse to the idea of drilling and tapping into a boiler and although it may be seen by some as not best practice I cannot recall the method being prohibited in the current publication from the Model engineering liaison group.

Regards,

Bob Youldon

Thread: Superfluous copper
04/09/2015 10:12:49

Good morning,

As I sit here tapping away on my machine the connection into the property is via fibre optic cable and we've had a fibre optic system here probably for the last twenty years, originally installed by Nynex who became Cable and Wireless and is now operated by Virgin media. distribution for both telephone and computer equipment throughout the house is by protected wireless connection, no wires involved, although I do have a fibre optic terminal here in the lounge should we need it for a television signal. So yes, there are places here in the UK where the fibre optic system has been installed and into the property to provide a "wire less" system.

Regards,

Bob Youldon

Thread: How to get a better Finish
31/08/2015 13:52:22

Hello Dave,

A couple of points; firstly get yourself a copy of Lathework A Complete Course by Harold Hall This book assumes no previous experience and secondly If you've a model engineering society nearby, make contact and there will be a wealth of knowledge there to tap into. What you really need is to watch someone setting up and using the lathe, you'll learn more in ten minutes watching someone. We all get there in the end, but in the beginning its all a bit of a mystery.

Regards,

Bob Youldon

Thread: Weight and transportability of a Myford lathe
27/08/2015 14:09:08

Hello Roger,

Having recently had the task of removing a Myford S7 from a roof space! down three flights of stairs to a waiting car I can safely say a couple of strong chaps is the essential component; the lathe was stripped of all items capable of being removed easily on site. Get somebody to weld up a "Tee" shaped bar from about 12mm round material with the cross piece approximately 400mm long and a leg about 600mm long, now if you leave the three jaw attached and the back gear locked the tee bar can be fed through the headstock and locked into position using the three jaw, lifting of the headstock end is then much easier when a firm hold can be maintained, the whole lot is then easily lifted by two chaps, the weight being reasonably distributed.

Regards,

Bob Youldon

Thread: Bronze Eccentric Straps
25/08/2015 23:41:01

Ah, a Titbolt Thunderfield, a wonderful little locomotive.

A piece of bronze is always a better bet than a gunmetal casting which inevitably seem to stretch after a period of use, better still cast iron straps running on steel eccentrics. A good friend of mine always referred to eccentric straps as band brakes!

Regards,

Bob Youldon

Thread: Confused by 26, 32, 40 TPI Threads
25/08/2015 14:57:39

Good afternoon,

To be honest, should I be building a half sized traction engine I'd use fittings more suited to the scale, fittings with the BSP taper thread form or from the NPTF range, although I'd advise anyone here in the UK to consult with their boiler insurance provider prior to any decision is made on any particular thread form or fittings, who may have a view on the matter.

Regards,

Bob

Thread: Smokebox to Boiler joint
25/08/2015 14:18:21

Hello Baz,

I wouldn't worry about the 15 thou gap when fitting the smokebox to the boiler; if you intend fixing the smokebox to the barrel, e.g. bolting it or fitting a few screws then most of any gap will disappear. I'd recommend a smear of gasket sealant, Heldtite or similar to both surfaces prior to assembly and that'll do the trick. Some folks will also put a bead of silicon sealant around the joint at the rear of the smokebox as an additional seal, but with only .015" gap I think it is a bit superfluous.

I've used the foregoing method for many years with complete success.

Regards,

Bob

Thread: Dezincification?
14/08/2015 22:14:42

Good evening Dennis,

Looking at an enlarged photograph of your defective check valve, I can say with almost certainly the cause is dezincification, its discoloration to almost a copper colour together with the friable appearance of the remains are consistent with dezincification. The cause being the material the check valve was made from, brass and in all probability what is referred to as screw rod, my advice is for all fittings below the water line to be made from a non zinc bearing material, drawn bronze being most suitable. The process of dezincification is an electronic action where by the zinc becomes the sacrificial anode where the copper of the boiler forms the other component. Filling the boiler with rain water is not advised due to the unknown impurities it may contain and in all probability will be measured as mildly acidic. Boilers should be blown down at the end of the day thus removing any impurities, but importantly removing any dissolved acids that have accumulated during the days steaming.

To sum up then, no brass below the water line and regular blowing down at the end of the day and if a steel boiler it is essential to add a treatment to the feed water.

Regards,

Bob

Thread: brass
05/08/2015 11:10:33

Good morning all,

Re:

Surely the important point here is that any thing that becomes a permanent part of the pressure vessel needs to resist de-zincification. Therefore all the threaded bushes that are silver soldered into the boiler shell need to be made of bronze.

The foregoing is totally correct and for the amount of bronze and work involved, costs in both materials and time add very little to the overall boiler cost. Fittings however below the water line must be able to resist de-zincification whereas those above the water line could be made from brass, but it seems odd not to make all of the fittings from bronze.

There are areas of the country where de-zincification is quite a problem; sadly de-zincification of miniature fittings does give any indication of impending failure until it's too late. I have witnessed a couple of failures due to de-zincification, a bottom fitting on a gauge frame failing and a blowdown valve giving up when being opened at the end of a running session; on each occasion the owners have been relatively lucky to avoid serious scalds. Of more concern was the blowdown failure, the valve being located low down on the side of the firebox, what if a child had been unfortunate to have been in the way when the valve body finally gave up at say in the station area, the consequences could have been horrendous.

No sir, I will always advise the use drawn bronze for all fittings and boiler bushes, for that little extra cost and work I can rest assured any fitting on my locomotives will not give up due to de-zincification, the risk is just too great particularly in todays litigious society.

Regards,

Bob

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