Metic Minnie Boiler Materials

[Robert FairbrotherParticipant @robertfairbrother78602]

Wondering how other people have made there boilers. If you have used a coper tube and drilled holes in the tube. Was there issues with the holes not being perfect due to drilling into a tube. Or should it be done on a copper plate and then rolled and soldered togther to form the boiler.

Following these instructions Btw (http://www.modelengineeringwebsite.com/Metric_Minnie_3.html)

And does the engine need to be made in a certain order as at the moment i am making what parts i can with the material at hand (19 Year old student)

[Robert FairbrotherParticipant @robertfairbrother78602]

[JasonBModerator @jasonb]

Although some boilers are made from rolled sheet the Minnie has been designed to use tube, once you start changing the design there are other factors to consider, for example it is generally taken that having a joint in the barrel which you would if rolled will result in a weaker barrel so at the design stage this is taken into account and thicker material specified if needed.

The Minnie was originally designed using imperial measurements and materials and the drawings that Julius has done are in metric, while this makes it easier for someone like yourself who has been brought up using metric it can give problems in practice. Not least that it can't be built as he shows it

You should aim to get the holes in the barrel as accurate as possible as the fit will affect the strength of the silver solder joints as the solder is not a gap filler and relies on a gap of about 0.05mm so that the cappilary action will draw the solder into the joint. A step drill can be handy for drilling the larger holes as they don't snatch as much as a regular jobber drill bit.

You can more or less build in the order that you like, a lot of people start with the front end and then move onto rear wheels. However you will reach a stage where one item will depend on another for its final size and position, for example the cylinder fixing holes shown on the boiler drawing are best drilled using the cylinder strapped onto the boiler as a jig.

I would strongly suggest that you either get hold of the back issues of Model Engineer that covered the construction of Minnie, they can be picked up on e-bay or the ME booksellers. Or there is a book "Model Traction Engine Construction Featuring Minnie" by L C Mason. Both give the order of construction and show how to machine all the various parts.

Also if you intend to run the boiler anywhere in public it should be tested which is best done you a local club boiler inspector, worth having done even if just being used at home. It would be best to print off teh drawings and take them along for your inspector to look at before doing any work on teh boiler as I do not know of any boilers that have been made to Julius' drawing and as they are not teh same as Masons original they will need to be checked which is best done before you cut any metal.

 

J

Edited By JasonB on 05/07/2016 09:55:20

[Neil WyattModerator @neilwyatt]

Hello Robert,

Welcome to the forum.

If you drill holes in stages they are more likely to end up round, I have found that a cone drill or step drill is good for making very round holes in sheet metal.

Use tube as (1) it will be round! and (2) you won't have to make a long seam. It's probably a good idea to find a club near you and get some advice on making the boiler from their boiler inspector.

When making parts, just be aware of how they will fit together, for example its easier to make a piston rod/connecting rod to suit the distance from crankshaft to cylinder than the other way around.

Neil

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