Little Wonder

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Trevor Thompson
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Re: Little Wonder

Post by Trevor Thompson » Mon Feb 21, 2022 9:58 am

I have been spending lots of time on K1 recently which explains the lack of activity on this (and 4420). However I have made the frame stretchers for the inner ends of the bogies:
IMG_2119.JPG
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Trevor Thompson
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Re: Little Wonder

Post by Trevor Thompson » Thu Sep 08, 2022 3:20 pm

It has rained here in West Wales for the last few days so I pulled this project onto the bench again.

I have cut out the frames for the boiler cradle, made the stretchers for the cradle and assembled it. I have also put the pivot stretcher onto each bogie, and made the connecting bolts. So here are a few views of the progress:
IMG_2398.JPG
IMG_2397.JPG
IMG_2396.JPG
I suppose that I will have to start on the cylinders if it continues to rain:
IMG_2401.JPG
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Old Man Aaron
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Re: Little Wonder

Post by Old Man Aaron » Fri Sep 09, 2022 4:09 pm

The only thing equal in this thing's size, is the sheer amount of effort you're putting into it. :salute:
Regards,
Aaron - Scum Class Works

Trevor Thompson
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Re: Little Wonder

Post by Trevor Thompson » Sat Sep 10, 2022 9:51 pm

Old Man Aaron wrote:
Fri Sep 09, 2022 4:09 pm
The only thing equal in this thing's size, is the sheer amount of effort you're putting into it. :salute:
Lets hope the end result is worth the effort!

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Re: Little Wonder

Post by Trevor Thompson » Sat Sep 10, 2022 10:17 pm

I have been squeezing in time to work on the cylinders (which I hadn't intended to start straight away) - carried away again!

So 4 sections of the block of brass have been parted off in the lathe and turned to size, width, length and height. I have marked the centre of the bores, and bored and reamed them all. Here are two of them:
IMG_2404.JPG
I am carrying out each operation on all 4, rather than finishing one and then starting on the next. There is better efficiency in having the machine set up to carry out the operation and having the right tools for doing it to hand, and therefor doing it 4 times.

You might remember from my drawings that the valve face is an extension on the inner face of the cylinder which passes through the frames into the valve chamber. So the first operation was to mill 4.5 mm off that inside face to make the valve face protrude:
IMG_2406.JPG
The end result required the sharp edges removing and the opening in the combined valve chamber/frame needed slight filing to get a good sliding fit. This is the first valve face and the hole it fits into:
IMG_2409.JPG
The bolt heads holding the frame to the valve chest prevent the cylinder fitting right down to the frame at the moment - and I intend to mill out a pocket in the inside face of the cylinder to swallow the bolt head. I am going to do all the milling first - and then concentrate on drilling afterwards. So here are the 4 cylinders sitting as far into place as they will go at the moment:
IMG_2408.JPG
I think it will be milling the bottom of the cylinders to make the flange for the bolts which will hold it to the frame next.

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Re: Little Wonder

Post by SimonWood » Thu Sep 15, 2022 2:19 pm

This is really starting to take shape. The boiler cradle frames look superb.

Trevor Thompson
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Re: Little Wonder

Post by Trevor Thompson » Fri Sep 16, 2022 9:36 am

I keep going back to it!

All of the cylinders are now shaped and fitted to the frames. You can see the cutaway around the valve face and the hole in the frame through which it fits on the nearest cylinder:
IMG_2419.JPG
All of the cutouts for the bolt heads are made, and the cylinder is secured to the frame by 4 bolts. From above the bolts fit from the inside:
IMG_2422.JPG
From the bottom they fit from the outside. I had to make cutouts in the bottom of the cylinders to make room for the nut spinner to reach the bolt head:
IMG_2421.JPG
And of course all 4 cylinders are now fitted to the frames.

On to the cylinder end covers, piston and rod next, and then drill all of the holes.

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Re: Little Wonder

Post by Trevor Thompson » Fri Sep 16, 2022 12:10 pm

Four front cylinder covers, and 4 rear covers:
IMG_2425.JPG
The basic shape turned, then milled and drilled in the rotating table. That ensures that the milled faces are perpendicular and centralised. It also makes it easy to ensure that the mounting holes are all 60 degrees apart (and on the same radius).

And now to work on the cylinders one at a time. The first piston is made and in the foreground of this photo:
IMG_2426.JPG
As an aside I am finding that having a digital readout has made my work much more accurate. For example I was able to turn the piston blank to a diameter of 11.95mm and find it was a smooth fit in the bore first time. I then turned the groove for the O ring to 9.15mm diameter and 2.0mm width (for an O ring 12mm diameter and 1.5mm cord diameter), just using the readout - no trial and error. The piston with its O ring just fits first time with a nice smooth movement.

Really satisfying!

Trevor

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