Kerr Stewart 4420 - Live steam and 3D printing

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Re: Kerr Stewart 4420 - Live steam and 3D printing

Post by Lonsdaler » Mon Jan 10, 2022 12:32 pm

That's very impressive Trevor and far beyond my skillset. It's an interesting idea to combine 3d printing and live steam - fingers crossed for you that it works.🤞
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Re: Kerr Stewart 4420 - Live steam and 3D printing

Post by SimonWood » Mon Jan 10, 2022 7:37 pm

Trevor Thompson wrote:
Fri Jan 07, 2022 12:34 pm
I now have a running chassis. The steam motor is easily removable by undoing two nuts and bolts, and the chains are all connected.

I have added video of it running on compressed air at 20psi. The reverser does allow good control of both direction and speed - and I am sure could be controlled by a servo.
Terrific! Very controlled. This whole project just gets more and more exciting.

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Re: Kerr Stewart 4420 - Live steam and 3D printing

Post by Trevor Thompson » Tue Jan 11, 2022 9:59 am

SimonWood wrote:
Mon Jan 10, 2022 7:37 pm
Trevor Thompson wrote:
Fri Jan 07, 2022 12:34 pm
I now have a running chassis. The steam motor is easily removable by undoing two nuts and bolts, and the chains are all connected.

I have added video of it running on compressed air at 20psi. The reverser does allow good control of both direction and speed - and I am sure could be controlled by a servo.
Terrific! Very controlled. This whole project just gets more and more exciting.
Simon

How are you getting on with the chassis?

Trevor

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Re: Kerr Stewart 4420 - Live steam and 3D printing

Post by SimonWood » Tue Jan 11, 2022 12:39 pm

Trevor Thompson wrote:
Tue Jan 11, 2022 9:59 am
How are you getting on with the chassis?
Got my replacement print-bed stickers (also got a new plate just to have a spare) and now printing without issues. Will post a pic once I have it assembled!

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Re: Kerr Stewart 4420 - Live steam and 3D printing

Post by Trevor Thompson » Thu Jan 20, 2022 7:35 pm

I have started to build the boiler.

An unusual design I know. Two tubes one on top of the other with slots to allow steam and water to pass through, as well as to allow for the cross stays:
Screen Shot 2022-01-19 at 16.21.03.png
Screen Shot 2022-01-19 at 16.25.24.png
Rather than cut the copper tube longitudinally as per the drawing above I decided to make 6mm slots across the tubes, to allow for the cross stays etc. Just seemed a "better" way to do it. The end plates are not shown in the views above, but I will describe those later.

Starting with two tubes.

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Re: Kerr Stewart 4420 - Live steam and 3D printing

Post by Trevor Thompson » Sun Jan 23, 2022 10:00 am

Making the boiler.

I have turned lengths of softwood to be a smooth sliding fit inside the two lengths of copper pipe - so that they support the copper while it is being machined:
IMG_2064.jpg
and cut 4 slots 6mm wide in each pipe where the cross stays will go:
IMG_2067.jpg
I also drilled 2 6mm diameter holes in what will be the top of the boiler to take bronze bushes for safety valve and filler.

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Re: Kerr Stewart 4420 - Live steam and 3D printing

Post by Trevor Thompson » Sun Jan 23, 2022 10:04 am

The flat sides of the boiler have been cut from 1.6mm thick plate, and the cross stay holes drilled:
IMG_2070 2.jpg
Test assembling the first parts of the boiler. One of the tubes needs turning round!:
IMG_2072.jpg
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Re: Kerr Stewart 4420 - Live steam and 3D printing

Post by Trevor Thompson » Sun Jan 23, 2022 10:11 am

The side plates silver soldered and the cross stays fitted ready for a second silver soldering:
IMG_2074.jpg
Cross stays silver soldered, and the assembly in the pickling bath to remove the flux residue:
IMG_2075.jpg
As the assembly gets more mass the heat required to solder it increases. I am now having to use my biggest torch, with the gas pressure turned up high to solder it. It took about an hour to get those cross stays soldered up.

Trevor

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Re: Kerr Stewart 4420 - Live steam and 3D printing

Post by -steves- » Sun Jan 23, 2022 11:22 am

Trevor, I am loving these "moving shots" where you show the work being done and give an idea of how these things are made rather than just producing a picture of the part finished, great stuff, keep up the good work.

I often read your posts but don't respond often, but please don't think it's going unnoticed as I look forward to seeing your threads updated :thumbup:
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Re: Kerr Stewart 4420 - Live steam and 3D printing

Post by SimonWood » Mon Jan 24, 2022 9:09 am

Didn't quite get what you meant about the slots from your post on Thurs, but seeing the pics from yesterday that does look like a really good solution.

Clearly the soldering on this is advanced stuff! When I get to this stage I think I will be knocking on your door for some help :lol:

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Re: Kerr Stewart 4420 - Live steam and 3D printing

Post by -steves- » Mon Jan 24, 2022 1:12 pm

Trevor, are you using different temp solder for each stage to stop the pervious solder melting? If so what are you using and where from? If not, how do you do it without the previous solder work just falling apart??
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Re: Kerr Stewart 4420 - Live steam and 3D printing

Post by Trevor Thompson » Mon Jan 24, 2022 7:04 pm

-steves- wrote:
Sun Jan 23, 2022 11:22 am
Trevor, I am loving these "moving shots" where you show the work being done and give an idea of how these things are made rather than just producing a picture of the part finished, great stuff, keep up the good work.

I often read your posts but don't respond often, but please don't think it's going unnoticed as I look forward to seeing your threads updated :thumbup:
Glad you like it! That encourages me to keep going!

Trevor

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Re: Kerr Stewart 4420 - Live steam and 3D printing

Post by Trevor Thompson » Mon Jan 24, 2022 7:05 pm

SimonWood wrote:
Mon Jan 24, 2022 9:09 am
Didn't quite get what you meant about the slots from your post on Thurs, but seeing the pics from yesterday that does look like a really good solution.

Clearly the soldering on this is advanced stuff! When I get to this stage I think I will be knocking on your door for some help :lol:
That was what I was expecting!

Trevor

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Re: Kerr Stewart 4420 - Live steam and 3D printing

Post by Trevor Thompson » Mon Jan 24, 2022 7:38 pm

-steves- wrote:
Mon Jan 24, 2022 1:12 pm
Trevor, are you using different temp solder for each stage to stop the pervious solder melting? If so what are you using and where from? If not, how do you do it without the previous solder work just falling apart??
No I am not using different temperature solders - that is a technique which could be used - but I don't find it necessary.

I suppose a bit more detailed explanation is in order:

When a joint has been silver soldered then the combined materials seem to need a higher temperature for the solder to reflow. I seem to remember reading that somewhere in the distant past. In this case, just to make sure I placed the bare barrel on its side so one flat plate was uppermost. The idea was that if the plate came free I hoped it would stay where it was. I thought the lower plate was unlikely to get hot enough to have any chance of the solder melting. The stays, 3mm diameter, were a reasonably tight fit in the 3mm diameter holes. Sufficiently tight that I hoped they would stay in place. So I tried to concentrate the heat on one stay end at a time - not easy with a huge flame roaring away. Perhaps I should mention that this requires a high pressure torch connected to a calor gas propane cylinder. Such a torch does not have a normal pressure regulator like you get for a BBQ - but something which can be varied - and it really is high pressure. The big cylinder is also necessary because its the only way to provide gas at the required rate for this length of time. Perhaps I should try to get a photo of this for the next stage.

Anyway back to the main point - when it is eventually hot enough - the stays can be soldered one at a time. A matter of getting the solder to flow around the one stay - while the rest isn't quite hot enough. Then move to the next, taking advantage of the whole thing being almost red hot. Then when they have all been soldered, let it cool a little, to make sure nothing is close to the melting temperature, turn it over with tongues, and solder the stays on the other side, trying to take advantage of the whole thing still being pretty hot.

The challenge will be to get the end plates hot enough to solder. Not fear of the rest becoming unsoldered - just straight forward can I get it hot enough!

I am using the silver solder which is sold by Mac Models, they only have the one type on their website, and easy flow flux which they also sell.

By the way, I find the above much more difficult to do with ordinary solder - the type you would use for plumbing joints. A gas torch gets things too hot too readily, and it all falls apart. That is much easier with some form of hot bit.

So for both types of soldering I think it is really about balancing the rate that heat is entering the job, and the rate heat is leaving, so that you can just get it hot enough for the solder to flow, and when you remove the heat it solidifies quickly.

Trevor

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Re: Kerr Stewart 4420 - Live steam and 3D printing

Post by -steves- » Tue Jan 25, 2022 9:07 am

Trevor Thompson wrote:
Mon Jan 24, 2022 7:38 pm
-steves- wrote:
Mon Jan 24, 2022 1:12 pm
Trevor, are you using different temp solder for each stage to stop the pervious solder melting? If so what are you using and where from? If not, how do you do it without the previous solder work just falling apart??
No I am not using different temperature solders - that is a technique which could be used - but I don't find it necessary.

I suppose a bit more detailed explanation is in order:

When a joint has been silver soldered then the combined materials seem to need a higher temperature for the solder to reflow. I seem to remember reading that somewhere in the distant past. In this case, just to make sure I placed the bare barrel on its side so one flat plate was uppermost. The idea was that if the plate came free I hoped it would stay where it was. I thought the lower plate was unlikely to get hot enough to have any chance of the solder melting. The stays, 3mm diameter, were a reasonably tight fit in the 3mm diameter holes. Sufficiently tight that I hoped they would stay in place. So I tried to concentrate the heat on one stay end at a time - not easy with a huge flame roaring away. Perhaps I should mention that this requires a high pressure torch connected to a calor gas propane cylinder. Such a torch does not have a normal pressure regulator like you get for a BBQ - but something which can be varied - and it really is high pressure. The big cylinder is also necessary because its the only way to provide gas at the required rate for this length of time. Perhaps I should try to get a photo of this for the next stage.

Anyway back to the main point - when it is eventually hot enough - the stays can be soldered one at a time. A matter of getting the solder to flow around the one stay - while the rest isn't quite hot enough. Then move to the next, taking advantage of the whole thing being almost red hot. Then when they have all been soldered, let it cool a little, to make sure nothing is close to the melting temperature, turn it over with tongues, and solder the stays on the other side, trying to take advantage of the whole thing still being pretty hot.

The challenge will be to get the end plates hot enough to solder. Not fear of the rest becoming unsoldered - just straight forward can I get it hot enough!

I am using the silver solder which is sold by Mac Models, they only have the one type on their website, and easy flow flux which they also sell.

By the way, I find the above much more difficult to do with ordinary solder - the type you would use for plumbing joints. A gas torch gets things too hot too readily, and it all falls apart. That is much easier with some form of hot bit.

So for both types of soldering I think it is really about balancing the rate that heat is entering the job, and the rate heat is leaving, so that you can just get it hot enough for the solder to flow, and when you remove the heat it solidifies quickly.

Trevor
Thanks Trevor, just the answer I was looking for :thumbup:

I have done lots of silver soldering and have a couple of Sievert torches and a couple of 25kg gas bottles too which I use. I have never silver soldered a boiler, but I do have a couple to do in 3 1/2" gauge, so any advise is more than welcome :D
The buck stops here .......

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http://peterborough.16mm.org.uk/

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