Minnie 1″

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Minnie 1″

This topic has 79 replies, 13 voices, and was last updated 28 January 2022 at 09:13 by JasonB.

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20 May 2019 at 20:00 #410142
james huxstep
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@jameshuxstep40895
So I've finally decided on the minnie 1" bought my boiler kit, I have machined my former plates got my burner, can of propane thermiculite bricks and have started to anneal various plates. I have seen vermiculite in garden centres in gravel form. Could I create a sand pit with vermiculite blocks on the outside holding vermiculite gravel inside for the actual boiler cook ups, as I'm paranoid after the horror stories on hear about not getting enough heat.
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20 May 2019 at 20:00 #9674
james huxstep
Participant
@jameshuxstep40895
Beginner minnie 1″ build
22 May 2019 at 18:04 #410430
james huxstep
Participant
@jameshuxstep40895
Also I am reading the hardback book which documents the build of the minnie, and I've noticed he talks about two different types of solder to use on the boiler. Both of the ones he mentions seems to be discontinued as the book was written a while ago when the design first came out. What are the up to date versions of the higher melting point one for the throat plate join, and the solder for the rest of the boiler?

Thanks

James
22 May 2019 at 18:21 #410431
JasonB
Moderator
@jasonb
The replacement for the higher melting point C4 solder would be something like 424. The replacement for the lower melting point "Easyflow" is 455. I would suggest you also yse HT5 flux which will last longer if it takes you a while to get the work upto temperature. Have a look at Cup Alloys for materials and also read their "best brazing practice"

Do not use "soft solder" on your boiler.

Not tried the loose vermiculite so don't know.

Edited By JasonB on 22/05/2019 18:21:59
22 May 2019 at 18:53 #410435
nigel jones 5
Participant
@nigeljones5
Hi James – there is one thing far worse than not enough heat and it is too much heat. Just be careful not to over do it as you will never get 'burnt' copper to take solder. Just had a customer bring me a perfectly made 1 1/2" traction engine boiler which had been severely over heated – leaks everywhere, impossible to fix and now in the scrap bin!
22 May 2019 at 18:59 #410441
MichaelR
Participant
@michaelr
I don't think loose Vermiculite would work it's very light weight, I think the blast off your blow torch would displace it all over the place.

Mike.
22 May 2019 at 20:03 #410466
james huxstep
Participant
@jameshuxstep40895
OK food for thought thanks, so maybe just stick to my blocks and some insulation blanket from cup alloys?

Thanks again
24 May 2019 at 15:47 #410750
james huxstep
Participant
@jameshuxstep40895
So I take it that these cleaning salt solutions, are the new version of the sulphuric acid and water mix? If so how do they compare?

Thanks James
24 May 2019 at 15:52 #410752
JasonB
Moderator
@jasonb
Slow but safe.
27 May 2019 at 20:30 #411231
james huxstep
Participant
@jameshuxstep40895
Thanks.

Ive noticed that the design does not incorporate a injector, but does have a spare feed which is blanked on the manifold.I would rather like to have a small injector on the model for something to tinker with/experience in making. Can i use this spare outlet?

Also im coming round to making the drilling template for the firebox stays which is suggested to be made out of 1/16 steel plate.Can i make this out of 1/8 plate so i can mill it/drill it as its a bit more rigid and my hacksawing skills are not great.

Some photos to come of my small progress so far if people are interested?

Thanks

james
27 May 2019 at 20:37 #411232
JasonB
Moderator
@jasonb
Should be OK to take the injector feed from that. Add an extra bush on the opposite side of the boiler to the pump to take the return clack (non return valve) It's a small size for an injector so may not work well, could always use the bush for a small handpump in the coal space if needed

Template will be fine from thicker material.

On the subject of manifolds speak with your boiler inspector about connection of the pressure gauge as it is not the preferred practice now to take it from the same manifold as the water gauge.
27 May 2019 at 21:23 #411250
james huxstep
Participant
@jameshuxstep40895
Ok food for thought, maybe i should just stick to the design while learning then.Good question about the pressure gauge, if it does not come off the manifold will it just have its own dedicated bush in the backhead?

Also, as im getting closer to annealing the copper plates is there a special type of hammer to do the job?

Thanks

james
27 May 2019 at 22:17 #411263
Harry Wilkes
Participant
@harrywilkes58467
Hi James may I suggest you give some consideration to Jason's suggestion above if you intend to use the engine in 'public' you will need to have it tested and currently the boiler reg's require that the boiler is fitted with two means of putting water into the boiler !

H
28 May 2019 at 17:03 #411364
Nigel Bennett
Participant
@nigelbennett69913
Check the bar litres of the boiler. A Minnie is very small and likely to fall within the “smaller boilers” category specified in section 11.7 of the regs, where only one water feed is required.
31 May 2019 at 12:17 #411906
james huxstep
Participant
@jameshuxstep40895
So after buying one of the cup alloy dvds for inspiration, I am extremely tempted to purchase one of these oxy/mapp brazing kits, and use my propane torch for general heat and annealing purposes. Any thoughts?

Thanks

James
31 May 2019 at 14:29 #411928
Roderick Jenkins
Participant
@roderickjenkins93242
I've got the oxyturbo set. The oxygen bottle only lasts about 10 minutes, so very expensive to run. Great if you need to get some spot heat into an awkward location like inside the firebox but no replacement for a propane torch. A normal propane torch should be fine for a Minnie boiler.

HTH

Rod
5 June 2019 at 17:15 #412782
james huxstep
Participant
@jameshuxstep40895
So, I'm still forming various bits, so far so good. Looking ahead the book mentions securing the first 3 sections together i. e. the barrel, throat plate and outer wrapper with some rivets, either 1/16 or 3/32.

Are these copper rivets?

Are these the type of rivets that you use rivet snaps on?(never done that before)

And what type of screws/nuts can I use before the rivets are finally put in for test fitting etc?

So far I have been scribing on marker blue on the copper boiler parts, I notice some people just scribe straight onto the copper with out blue.

Thanks as always

James
5 June 2019 at 18:30 #412790
JasonB
Moderator
@jasonb
Yes Copper

Yes snap head rivits that need a set and snap. Don't rivit the plates hard together as you want the solder to flow between.

You can use whatever you have to hand for trial fits, when I did mine I used steel 10BA screws and nuts which fit OK in the 1/16" holes. Any screws or nuts that will remain should be bronze.
6 June 2019 at 15:21 #412947
james huxstep
Participant
@jameshuxstep40895
Hi thanks for the info.

How does the set/snap work? I have seen the tool which has both the snap and set on one piece. Surely you need two separate bits? One to seat the already made rivet head and the snap to hammer down a head on the other end.

Thanks

James
6 June 2019 at 16:20 #412958
JasonB
Moderator
@jasonb
Yes you need two, though the set is easy to make yourself being no more than a punch with a hole in it to slip over the rivit shank.

You put a rivit through a hole in the two parts to be joined and with your snap held vertically in a bench vice place the factory head in the hemispherical recess. You then put the set over the end of the rivit and give it a whack with a hammer which will make sure the two plates are close together and the lower plate is up against the rivits head.

You can now change over to your second snap and use that to form the exposed end of the rivit. Do have a practice first on some scrap to get the feel for it and to determine the correct length of rivit to leave above the work so you get a good head, somewhere around 1.4 to 1.5 times the shank diameter will be right but varies depending on how tight the rivit is in the hole and the individual snap.

Where possible have the factory formed head on the side hat shows but that is not always an option
6 June 2019 at 16:53 #412961
Roderick Jenkins
Participant
@roderickjenkins93242
James,

I don't know if you are aware but I believe it is usual these days to use some oversize rivets on the firebox sides to act as anchors for the horn cheeks. This photo from Jason's album shows what I mean

**LINK**

Rod
6 June 2019 at 17:15 #412968
JasonB
Moderator
@jasonb
Not quite Rod.

Common practice now to use copper rivits instead of threaded stays and nuts.

The 5 fixings for the hornplates go into solid bronze stays about 3/8" diameter that are machined true to the barrel after the boiler is complete and then the hornplates are offered up, set to the correct position and the holes spotted through.

As with anything boiler related talk any changes from the drawings through with your boiler inspector first
15 June 2019 at 14:42 #414381
james huxstep
Participant
@jameshuxstep40895
So all good so far, I have 2 firebox plates, smoke box, boiler barrel to size and shape and have done the throat plate. Some 3/32 copper rivets have arrived 1/2" and 3/8" long with two rivet snaps. The hole in which the rivet shank goes into does not bottom out. Is this normal or is the hole too deep. I haven't given the riveting a practice yet but my understanding is this.

Drill hole in both parts to be riveted together

Place rivet through both plates factory head down and lying in the concaved part of the set tool held in a vice.

Get the other tool and place the upturned rivet shank into the hole(not bottoming out/bottoming out?)

Give it a tap

Use other concave part to tap down and form head, but not too tight to allow solder to flow.

Sound good?

Also if I can't get my riveting skills up to scratch, what is to stop me just putting appropriate sized copper bag screws and nuts in and soldering them in and filing flush? Or is it a case of honing my skills with the rivets.

Thanks

James
15 June 2019 at 14:50 #414382
JasonB
Moderator
@jasonb
You want the hole deep as it is the plates you are setting together, you are not expanding the rivit.

All sounds OK

get the practice in now where it does not really show
26 July 2019 at 14:09 #421027
james huxstep
Participant
@jameshuxstep40895
OK first dry assembly done, all good nice and square and level.

1/going to turn the phos bronze bushes for back head. Want to make a hss tool for this job any suggestions on tool/turning phos bronze?

2/turning /milling copper cutting fluid or not?

Pictures to follow
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