My Minnie

[Nick WelburnParticipant @nickwelburn]

Taking on a part finishing princess

[Nick WelburnParticipant @nickwelburn]

So after a Stuart 10v, and most of an s50 my attention had turned to building a Minnie. Not just a model, but an actual steam engine (albeit a small one)

So after some sage advice in another thread that it is within my capabilities I was looking around and found one part complete local to me at Cinderbarrow.

A chat with the seller and I found out it was a stalled project from the 70’s. Based on a black gates boiler and a set of pre machined gears. It came with a set of full drawings, the book carefully marked to show progress and the engine itself.
The boiler can be certified and to my eye the work so far seems really nice. It’s a significant step up from a Stuart in terms of fineness of details.

[Nick WelburnParticipant @nickwelburn]

[Nick WelburnParticipant @nickwelburn]

[Nick WelburnParticipant @nickwelburn]

All in so far I’m in for £370 which is a chunk of change. But I think the gears, book, plans and wheels have intrinsic value. I’ve got a few bits to do before work begins. A bigger work bench with an area for bits on it. And I need to finish my s50 and Cringle boiler.
It feels a bit like a step up to the big league with this but I’m on for the challenge!

[SteviegtrParticipant @steviegtr]

Bet that will look great when finished. All the best with the build.

Steve.

[Nick WelburnParticipant @nickwelburn]

I’ve made some progress this weekend. Sort of. A new top fitted to the work bench. Just need to neatly run some power to the machines.. also picked up a 2nd hand scroll saw from a chap in Ambleside. Turns out he’s going to move in round the corner from me. Could have saved a trip.

Should help with making the tender sides etc.

I’ve noticed the boiler is very neatly stamped with the markings ‘Tested at 100psi, SWP 50 psi’ on one side and on the front ‘KT 46.2.90’.

Does that mean I’m certified? Right off to the garage to finish a bit of work ok the s50

[Former MemberParticipant @formermember12892]

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[noel shelleyParticipant @noelshelley55608]

Most certainly NO ! You will need to join a club and then follow the boiler inspectors instructions ! If you have the skills and gear you can carryout your own test but this will NOT be a certificate nor will you be covered for insurance. In joining a club you will meet like minded souls and get all the help and advice you need.

You could engage a commercial boiler inspector but then it gets expensive. Good Luck. Noel.

[Former MemberParticipant @formermember12892]

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[Nick WelburnParticipant @nickwelburn]

Ok – when I bought the boiler I spoke to the club and the chap who was selling it. The club think it can be certified. I’m new to model engineering so I was uncertain if the stamping of something had some symbolism or not.

Clearly not so. It’s not clear to me what format a cert takes. I’ll bang a 100psi in it and see what happens.

[Former MemberParticipant @formermember12892]

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[Nick WelburnParticipant @nickwelburn]

Interesting I met the chap whose it was. He reckoned he’d bought the boiler from Blackgates and it was 30+ years old.

I’ll get some pressure it and see what happens

[Former MemberParticipant @formermember12892]

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[JasonBModerator @jasonb]

My '92 vintage Blackgates boiler does not have a serial number with letters as the suffix but would be worth contacting them to check if it was one of theirs.

Stamping only shows that it has been hydraulically tested to 100psi which is twice the working pressure of 50psi. If you are going to put any pressure in it then fill with water and ideally pump water in to test but you could apply air to the filled boiler. Don't just use air as if it did fail it will be a bit more risky.

There would have been a test certificate with the boiler but that only covers the test out of the engine. You will need to test it again when al the holes have been added and also under steam before it can be insured and "certified" buy a club or commercial inspector if you want to use it in public.

Worth talking to whoever is going to test and certify before you get too far as they may want the feed to the waster gauge separate to anything else and not off the manifold.

 

KT is likely builder and the 46th one made in feb 1990

Edited By JasonB on 06/03/2022 13:09:15

[Nick WelburnParticipant @nickwelburn]

Well I'm laid low with COVID, but its given me a bit of time to see what I've got and whats next. I've found my form for joining Cinderbarrow – so that'll get us so we know where we are at with the boiler.

I'm slightly struggling with the comment – the

"… Worth talking to whoever is going to test and certify before you get too far as they may want the feed to the water gauge separate to anything else and not off the manifold…."

I'd expect that it needs to be build as per the design to be signed off – but I'm guessing thinking has changed? But how does it make a difference? simple thinking suggests the pressure through a liquid should be consistent.

So the water level gauge as long as its acting with the same pressure at each end (as it goes in and out of the boiler) the tap off for pressure gauge location shouldn't matter? Does that mean I need to substantially modify the boiler?

So next up on things I can deal with is the tender. The water pocket is drilled inside for filling, but the lid is soldered shut… I guess I could slot it with an end mill to create a filling hole? But I do wonder given its all got to be soldered together if I need to just dismantle the build so far for cleaning and tinning etc. Some of the drillings for made elements of it are also a bit sketchy – photos in next post.

Guidance on moving forward happily received

[Nick WelburnParticipant @nickwelburn]

finally what’s this?

[Dave HalfordParticipant @davehalford22513]

Looks like the brackets for the cable fairlead, goes horizontally above the towing bracket on the back of the tender

[Nick WelburnParticipant @nickwelburn]

Thanks Dave, I’ve messed the order of the photos up. I was asking about the red pipe thingy.

[JasonBModerator @jasonb]

Nick, since the design was first published there have been changes to the boiler test code and one of those relates to separate supplies so the Minnie design that takes them off the single manifold may depending on how the individual boiler inspector interprets them not pass test.

It is also now preferred to have two means of feeding water into the boiler for example if the mechanical pump fails. Not easy to get an injector working on the Minnie so usual way is a hand pump either hidden in the coal space or in a trolley.

Both items are best discussed with the boiler inspector before you get too far down the line have have to redo or alter things. They may well also be happier if a new hydraulic test is done on the boiler as you don't have the paperwork. This would be done if a new self build boiler was being used.

Pipe fitting looks like a clack valve (one way or non return valve) not used on a minnie built to the drawings but if you mount the mechanical pump elsewhere then it screws into the boiler and is fed by a pipe into the nutted union on the fitting. Should be a stainless ball below the cover plug. It goes plug upper most and screw thread horizontal.

Edited By JasonB on 11/03/2022 13:46:50

[Nick WelburnParticipant @nickwelburn]

I’ve done my application for the club. So perhaps something like this with the handle popped out the floor of the tender **LINK**

More concerned about the not sharing the manifold. That sounds like a bigger change to the boiler. Guess we see what has to to be said

[Nick WelburnParticipant @nickwelburn]

Got started tonight. Had a look at the cylinder casting, lots of surfaces out of parallel. So I’ve set a new reference surface up and started to pull it together.

Now the bottom of the casting has been machined, but it rocks on the boiler so it’s clearly not concentric.

it’ll need a recut to put it right. I’m thinking could use my boring head to do an interrupted cut down that’s parallel ti the new reference surface.

Any thoughts?

[Nigel Graham 2Participant @nigelgraham2]

I've not tried it for a cylinder saddle but others have, successfully.

Some use a between-centres boring-bar and set the work on the lathe cross-slide – assuming a slotted cross-slide.

Others use as I take it you mean, a boring-head in a milling-machine.

Either way of course needs a very rigid, accurate set-up; low speed and gentle feed, and to allow for the bar springing.

Unless you have some form of radius-measuring instrument, it would be worth making a radius-gauge from suitable, fairly thick plate (or if you have it, an offcut of the barrel material) to test the surface without disturbing anything.

[JasonBModerator @jasonb]

between ctrs boring bar is more likely to give a parallel cut, unless you have a good rigid setup a boring head tool may deflect in the cut making it a bit smaller radius at the bottom of the cut.

Good thing with a between ctrs bar is you can easily remove it and test the boiler against the cut, unlikely to have the head room to do that on the mill.

What method did you use to end up with the rocking and are you sure there is no distortion in the boiler barrel they can move during construction.

[Nick WelburnParticipant @nickwelburn]

Hi Jason,

The cylinder was part machined when the project was abandoned by the previous owner.I have no idea how but the finish isn’t great.
My lathe doesn’t have a slotted cross slide. It’s an Amadeal 7*14 cj18b not a big machine. Thankfully the material machines easily, I think it’s a gun metal casting.

I’ll have a look at a between centres approach but I can’t immediately see how it could work.

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