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Brian's 1" Minnie Traction Engine

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JasonB03/02/2017 15:25:43
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Brian Abbott03/02/2017 17:51:14
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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

Brian Abbott28/02/2017 17:06:43
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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.

by_pass_valve.jpg

JasonB28/02/2017 17:54:08
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Should be 60degree inclusive, easily done with a centre drill and will then match off the shelf nipples/ferrules

Brian Abbott01/03/2017 16:50:50
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Thanks Jason.

Brian Abbott01/03/2017 20:46:18
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Hello Jason,

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

JasonB01/03/2017 20:49:03
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No can't remember.

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

Brian Abbott01/03/2017 21:18:23
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Ok, thanks Jason.

Brian Abbott09/04/2017 07:57:56
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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

JasonB09/04/2017 09:50:10
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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.

Brian Abbott10/04/2017 19:09:36
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Thanks Jason, glad you said that.

Sorry for not getting back to you sooner,

Brian Abbott19/04/2017 16:35:37
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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

JasonB19/04/2017 18:15:11
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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.

Brian Abbott20/04/2017 11:43:33
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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.

JasonB20/04/2017 13:11:15
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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.

Brian Abbott20/04/2017 13:25:27
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Thanks Jason.

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

Brian Abbott23/04/2017 21:01:15
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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.

Neil Wyatt23/04/2017 23:17:43
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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

Brian Abbott23/04/2017 23:46:52
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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

Neil Wyatt24/04/2017 08:25:19
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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

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