Modded 1″ Minnie Progress

[Billy BeanParticipant @billybean67480]

Absolutely superb.

[Richard S2Participant @richards2]

Now finished all 4 Oil Boxes for the 3rd and 4th shafts. An exercise in silver soldering tiny hinges to the lids of the 1/4" sq boxes. R/H side 3rd shaft was a bit fiddly to make and fit around the standard bearing design and the additional Water Lifter steam valve-

[Richard S2Participant @richards2]

Forgot these bits. Made up a more correct style steering bush and added a tool tray-

[Neil WyattModerator @neilwyatt]

More nice work, Richard.

Neil

[JasonBModerator @jasonb]

Looking good.

Shame the Fowlers had the steering on the other side

[Brian AbbottParticipant @brianabbott67793]

Hello Richard.

Would you be able to post me a picture of how you did the blower valve setup into the chimney saddle ?

Thanks in advance.

[SillyOldDufferModerator @sillyoldduffer]

Posted by Richard S2 on 16/11/2016 18:40:24:

…

As I have messed with the design and reduced the Size of the Cylinder Bolts, but increased the number, I have ensured I have increased, or matched the Core Area Total of the Bolts for the Cyl-Boiler fixing and Chest Covers when compared with the original design..

The holding down bolts (studs) are Phosphor Bronze (PB102/CW451K) machined from Drawn Rod.

I wish to check that my choice of fixings and the quantity are capable of withstanding the apparent extra pressure my boiler is quoted to withstand.

Can anyone offer me the Safe Tensile Strength of this PB (assuming it is in the fully, lowest annealed state)?.

The figures from the PB Specs online vary considerably and seem very high, compared to the example Mr J. Haining used in one of his books where he only uses 3000lbs psi as a SAFE figure for Steel !.

…

By and large maintaining the same core area with more but smaller bolts will be about the same strength as fewer fatter bolts. BUT, in changing the design you have to make sure that the stress remains equal across all the bolts. If the change caused one of the weakened bolts to more highly stressed than the others, it might fail first and cause the others to break in succession as each in turn takes an unfair amount of strain. Likewise, replacing several small bolts with a single big one could fail if the change put undue leverage on the big bolt.

The high tensile strength quoted for Phosphor Bronze compared with those given in the Haining book for Steel is almost certainly because the first is the maximum 'it will break' and the second is adjusted for reliability and safety.

Given the maximum tensile strength of a material a designer will allow a safety factor. If the material isn't structural, cost and weight can be kept low. But for materials under load the safety factor is usually at least 5 times the calculated stress and could be up to 20 times or more in a safety critical application. To calculate the safety factor, the designer takes into account the consequences of failure and the type of stress the item is subjected to – heat, pressure, vibration, stress concentrations, patterns of use and design lifetime etc. Quite difficult to do from scratch, so designers usually follow existing guidelines influenced by practical experience. These are often codified in building regulations and so forth. I don't think anyone on the forum can give a safe tensile strength for your particular application, the alternative is to apply a hefty safety factor. Like as not it's there already – Phosphor Bronze is strong and you're using more bolts to provide the same core area.

A model boiler at 80psi isn't particularly stressed but there is risk of injury if it goes wrong. Blowing yourself up in private is one thing, but a boiler can't be used in public unless an inspector is satisfied with the design, materials, build and pressure tests. It comes down to how the inspector applies his guidance; my guess is he'd be much more impressed by high safety factors (x10) than low ones (x1.5), and even more impressed if the boiler was built to an established design. What might worry him is major constructional changes. A chat with the inspector would probably establish what's needed.

Dave

[Brian AbbottParticipant @brianabbott67793]

Bump.

Hello Richard.

Would you be able to post me a picture of how you did the blower valve setup into the chimney saddle ?

Thanks in advance.

[Maurice Cox 1Participant @mauricecox1]

Richard asked about the tensile strength of PB when annealed . I have seen it stated in M.E. and elsewhere, that annealing copper does not effect the tensile strength, one way or the other. Can anyone say if this is correct and if it applies equally to PB please?

Maurice

[Richard S2Participant @richards2]

Long time, no post!. Well I've had other things on the go and this part of the build makes me go even slower. What with checking, prepping and making bits as I go along, the job of degreasing and etch priming took me ages, as I have to paint outside. It's either the wrong wind direction, temperature, or humidity.

I'm now assembling and top coat painting a few bits at a time, being cautious to get the sequence right to account for all my changes. The pump that I redesigned for an alternative mounting tested fine and have played with piercing the eccentric sheave to look like a casting (lots of knob twiddling on the rotary table in the mill) –

Detail on the motion work finished, but I will probably treat the bright steel parts and dull them off a bit. Having dulled off the pump eccentric strap and rod, I like the look of it and rids the model of the non scale shiny mirror finished steel I initially put on all the bright bits.

I trialled dulling off the steel rim faces on the W & S Water Cart using sulphuric acid and it worked well, so will use that process on the rest.

Among loads of tiny bit manufacturing, I recently spent an evening making up a number plaque for the rear plate. It's only 8mm between fixing centres and the numbers are made from 0.025" tinned copper wire and laid into a bed of solder. The numbers represent the boiller's build/tested month and year. Plate is ready to fit-

Tender has had it's first top coat, along with a few other bits today, so I'm finally making good progress.

Regards.

[Nigel Graham 2Participant @nigelgraham2]

Beautiful work!

(Goes a gentle shade of green with envy at the quality. )

[Jon LawesParticipant @jonlawes51698]

Beautiful.

[Harry WilkesParticipant @harrywilkes58467]

Nice

H

[An OtherParticipant @another21905]

Lovely piece of work.

[Dominic BramleyParticipant @dominicbramley60728]

Wow! That looking like the business!

Dom

[Richard S2Participant @richards2]

Thank you all for the positive comments. If it inspires people to add more detail to their project, then this topic has done the job.

I have finished the front wheels now. Altered the size of the hub caps (reduced) and changed the oiler style-

I decided to stick with a change I considered for the axle and have now finished the Spud ring and pan-

This was straight forward fabrication using visual scale from full size engines. The only problem was finding a way to produce the pan and flange. I found the answer in an old Duraglit tin and used the lid.

I think I have managed to get the final top coat on the tender today, amongst other bits, so proceeding quicker now.

Redesigned reversing lever and motion work pieces have all been fettled now, so ready for assembly-

Layout of the con rod parts following closer full sized design-

Thanks again.

Regards.

[Richard S2Participant @richards2]

Productive weekend with some assembly work. Fittings on the Backhead area installed. Additional floor plate extends to a closer point to the backhead. Oil boxes have filter screens inside –

Rather tricky to assemble and fit the tender what with the additions and changes, but went ok with just a few touch up areas to the black paint. Altered bolting pattern between tender/hornplates and I produced a raised chequer pattern, rather than cut it into the steps-

Tender was made with 20swg steel sheet (from a 1970s fridge freezer back plate) riveted to 5/16" brass angle. The tank is lined with brass sheet and a stainless floor plate. Rivet are 3/64".

Also managed some more painting of parts today, so for me it was productive for a change.

Regards

[Richard S2Participant @richards2]

Well, nearly 2 months of frustrating delays to the painting/assembly due to unfavourable weather conditions.

Finally able to set up yesterday and apply the penultimate coat of semi matt black over hot bits at the front end. The chimney saddle and exhaust pipe were painted separately as it is bolted on. This enabled me to apply a consolidation coat over all the Cylinder block joints, stud heads and nuts without access issues, having satisfied myself with the valve timing setting etc (he says with fingers crossed).

Assembly began today of the respective front end parts, some of which are embellished with a bit more detail like the flanged and bolted exhaust at the cylinder end-

Bolt heads to paint, followed by a final black spray touch in around the saddle/smokebox joint. A Clean up of the raised lettering to do.

I settled for a cylindrical locknut on the valve rod with 2 flats on it, which to me anyway, looks less bulky or obvious than a 5 ba nut. The extended regulator rod and gland at the front of the cylinder is dummy of course. I found that there was so much spare metal on the casting, that I decided to turn and file this bit up to give it some detail. Yet to make 2 14ba studs and nuts for it yet (before I put the chimney on) –

I did manage at least to get the flywheel painted last month and really pleased with the finish. Gib key lightly fitted as it has to come off again –

Boiler barrel cladding (nickel silver) has had the top coat flatted down and ready for clear coat, along with the rear hubcaps. So hopefully more progress soon.

[vic francisParticipant @vicfrancis]

Great work of art ,Richard Forget the mower restoration!let the grass grow long!!

Vic

[Jon LawesParticipant @jonlawes51698]

What beautiful work.

[Former MemberParticipant @formermember12892]

[This posting has been removed]

[Jeff DaymanParticipant @jeffdayman43397]

Outstanding Richard, it looks great!

[Nigel Graham 2Participant @nigelgraham2]

Magnificent! Thank you for showing us.

How did you make the proper chequer-plate profile?

[Richard S2Participant @richards2]

 

Thank you very much gentlemen for the positive responses. It's becoming a race where it's a challenge with the old hand joints locking up and the eyesight needs more assistance-

Posted by vic francis on 31/05/2021 15:49:58:

Great work of art ,Richard Forget the mower restoration!let the grass grow long!! Vic

Thanks Vic, I have avoided them up to last week where the Museum has just asked me to sort 2 engines, one is a Stuart Turner N2 1933 and the other is a little J.A.P 2a 1940s, So my summer has been allocated for me. Be easier to deal with larger nuts and bolts etc though! (then there is also the Treshing Machine).

Posted by Nigel Graham 2 on 31/05/2021 21:02:02:

Magnificent! Thank you for showing us.

How did you make the proper chequer-plate profile?

Thanks Nigel, appreciated. I took the process a stage further and made an embossing block from gauge plate.

Put the diamond hatching in with a slitting saw with 0.025" blade and about as deep. I then used that to press the pattern into well annealed brass sheet pieces by hitting it with a 1.1/2lb hammer on a block of railway track (my anvil, as I didn't have a press then). After the first impression hit, the cuts line up with the impression to get a 'register' for the next hit (again annealed). Had to put a screwdriver slot in the side to prise the plates apart, as the fit is very close. 3 hits and they were of good impression. I also tinned the top of the hatching so that I might wear the paint away a bit and it will show as looking like steel, rather than brass.

I still have the block I made over 30 years ago, as I might need it again-

This is the best shot I can get with my old camera to give a better view of the step(s) –

Thanks again. Regards.

 

Edited By Richard S2 on 01/06/2021 10:40:50

[SteviegtrParticipant @steviegtr]

Absolutely stunning. You should be proud showing that off.

Steve.

[Author]

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