Brian's 1" Minnie Traction Engine

Thanks Jason,

just wanted so see how you had bent the draw strap round the corner into the draw bar.

i've done mine the same.

Thanks again

Hello..

This is a sketch of the by pass valve on the Minnie i am building.

Unsure of the angle of the pipe cones, in the past i have just used the drill angle which seems to work ok, is this right ?

Thanks.

Should be 60degree inclusive, easily done with a centre drill and will then match off the shelf nipples/ferrules

Thanks Jason.

Hello Jason,

Can you remember what diameter pipe you ran from the by pass valve, was it 1/8" OD ?

No can't remember.

But just had a look and its all plumbed in 1/8"

Ok, thanks Jason.

Hello again.

I am in the process of machining the cylinder on my minnie.

I spent the day yesterday boring the radius on the saddle ensuring it was a good fit against an off cut of the boiler tube.

Now complete and tried against the boiler there is the slightest rock, I can only guess that the boiler tube has distorted slightly.

The gap is no more than a paper thickness in on corner so not much.

Should I try and file them in together or will the gasket sort things out.

Thanks.

Brian

You may find that as you tighten the bolts the boiler shell will pull back into shape if its is only a small rocking that you are getting.

Thanks Jason, glad you said that.

Sorry for not getting back to you sooner,

Hello All..

Can anyone tell me what the pocket is for on the underside of the Minnie cylinder block ?

The book calls it a sort of steam dome and according to google this is to prevent water entering the cylinder, is this correct ?

Thanks.

Edited By Brian Abbott on 19/04/2017 16:51:27

You will find it on most traction engines, it does indeed act a bit like a steam dome allowing steam to be drawn off higher above the top of the boiler barrel and therefor the water level which reduces the risk of priming.

Thanks Jason.

One last thing ( for now anyway )

The drawing calls for the bore to be. 0.625" and also for the piston to be 0.625"

Does the piston need to be a really good slide fit or should i have a little clearance ?

I have not noticed in the book what size o rings to order, i will have another look.

Thanks.

Good sliding fit, I think I have the O ring sizes somewhere, will have alook tonight. Think I got them in a set for the minnie from Reeves when I made mine.

Thanks Jason.

Fingers cross i have the bore exactly true and perpendicular to the face that mounts the front flange .

Hello,

When i turned the liner on my minnie cylinder i left it about .001" undersize.

On rechecking now its fitted i have a slight taper, measures 0.624" at one end to 0.625" at the other.

Very annoying, the finish is really good and the plan was to give it a quick polish to remove the last little bit.

Do you think lapping would true this up ?

Thanks.

How are you measuring it Brian? I'm assuming something like a bore gauge than measuring over it with a calipers or micrometer.

Unless you use something that reads to a tenth of a thou. The actual taper could be well below a thou but just happens to straddle the line betwee 0.624 and 0.625. On the other hand it could be nearly 2 thou, but that would probably appear obvious.

As long as your piston doesn't jam at one end or slop at the other, the o-ring should cope with a taper of about a thou.

Neil

Hello Neil, thanks for the reply.

Yes, using a spring bore gauge with a micrometer.

I think i will turn a gauge to pass though the bore to see exactly what is happening and if there is an issue

maybe i could try and pierce of 1200 grit paper on a split mandrel to lighly polish the bore ?

Jason..did you have any luck findind the o-ring size for the piston ?

The closest i can find is a BS111 which has an id of 0.424" and an od of 0.630"

Thanks

BS111 is the correct size for a 5/8" / 0.625" nominal bore.

They have to be oversized by a few thou as they should be compressed when you insert them - that's why they can accommodate slight tapers.

Neil