"Stuart" Twin Launch

Rudy from Norway · Dec 27, 2020

First attempt to run my new "Stuart" Twin Launch steam engine!
It didn't turn. Guess it has a timing problem or something. It,s a bit tight too.
Anyway, it's based on plans bought from Stuart. It's scaled up by 1.3 to make it easier to make more detailed parts.
I'll have a look at it and see if I can make it turn.
Rudy

Charles Lamont · Dec 27, 2020

I think you may need to do a bit more work on the finer details before that runs, Rudy! I suggest you try it lying on its side, you might get a bit of movement.

Rudy from Norway · Dec 28, 2020

Found out the block was a bit off so I skimmed a bit of it.

The plan is to make this scratch build look like the original with cast parts. I also want to give it more details so I bought the plans for the Stuart Triple expansion engine to see if there was something there I could use. However, there are plenty of pictures out there I can get ideas from. By staying with the original plans x1.3 for the important proportions I believe I will have a chanse of getting a good running engine.
I see this type of engine construction as a Challenge. Compared to the tubular A-stand frame type, that is easy to make very accurate, this construction has no solid frame and no good way of making the supports for the cross heads with good accuracy. There are simply too many setup steps and parts in between the piston rod axis and the cross head supports axis.
I'm aiming towards a smooth and slow running engine so I will putt my best effort into getting it right.
I will start by aiming for the numbers as close as possible and take it from there.
Rudy

Note the clamps. Just drilled and tapped some M10 holes. The wise is almost always too far from the blade to support odd shaped parts.

I actually got better surface finish with a 10mm carbide end mill than with this.

My Chinese ZX32 bench mill actually does quite a bitt of work here. This 16mm roughing cutter is very efficient.
I also believe I have got my hands on a very good quality chunk of cast iron here.

Now I can imagine the engine block!
As you see I have scaled up by 1.3 and converted all measurements to metric.

Blacksheep · Jan 3, 2021

Good start.
I’ll be watching.

Rudy from Norway · Jan 18, 2022

I´m back in the shop again after a hectic period at work. Had some progress on the major part, the block. Have to say it was a scary time at the end, having invested quite a bit of time on this chunk, a mistake would be hard to handle.
Boring the cylinders was best done in the lathe. My mill is not rigid enough in the quill to give a parallel result. It opens up at the bottom as I feed down. About a thou, but I´m aiming for better than that.

Trying to make it look like a casted part. I will clad the cylinders with mahogany.
Rudy

bufferbrown · May 11, 2022

Wow that's some great milling work. Well done!

Johan Maritz · May 12, 2022

Yes i agree, amazing amount of work into that cylinder block. That wants to be done. Following, great work!

Rudy from Norway · May 12, 2022

The soleplate in the making. Had this aluminum slob laying around. It will be painted, so nobody will know its not cast iron.

This operation was not as staight forward as one may think. I´m aiming for high accuracy and drilling holes is something I never get very accurate. This is the cylinder bottom plate and the hole for the piston rod has to be exactly in the center if the piston rod shall travel along the correct path downwards. Here I turn the register for the cylinder and boring the hole in one operation.

This operation is also an important one. The surfaces where the the cross head guide rail (or whatever its called) shall be attached, has to be exactly the same distance from the piston rods for both cylinders. So I spent some time aligning the cylinder center with the mill X axis. And with the bottom covers already installed, this setup gave me the desired accuracy. Th bottom covers do not turn in the cylinders, so they can be removed an relocated in exaxtly the same rotation.

Johan Maritz · May 12, 2022

You just gave me a great idea. I bought a twin launch from a deceased estate, but once looking carefully I discovered a very badly butchered engine, especially the soleplate. I'm not willing to buy a new casting, but nothing prevent me from doing the same as you. The cylinders are ok ish, the rest are all also badly made/machined but that is all easily machined from barstock. So there is hope for my twin launch. Great work there.

delalio · May 13, 2022

This is proving to be an awesome build, using some enviable skills! Great work!!

Rudy from Norway · May 13, 2022

Johan Maritz said:
You just gave me a great idea. I bought a twin launch from a deceased estate, but once looking carefully I discovered a very badly butchered engine, especially the soleplate. I'm not willing to buy a new casting, but nothing prevent me from doing the same as you. The cylinders are ok ish, the rest are all also badly made/machined but that is all easily machined from barstock. So there is hope for my twin launch. Great work there.

This particular engine construction actually is a nightmare, from a construction point of view. It was cheap to build back then, period. The problem is getting the rail that supports the cross head exactly in line with the imaginary perfect path. There are a tonn of points where we loose the register or reference to the next machining operation. The result is that most of these engines require quite some pressure to runn overcoming tight spots. And when they do runn, they tend to knock. Compared with an engine with a standard, like the Stuart 10V and its many siblings, It can be made very accurate with only a few setups witch all can be registered to each other.
But it is such a beautiful classic type of engine.
Rudy

Charles Lamont · May 14, 2022

Rudy said:
This operation is also an important one. The surfaces where the the cross head guide rail (or whatever its called) shall be attached, has to be exactly the same distance from the piston rods for both cylinders. So I spent some time aligning the cylinder center with the mill X axis. And with the bottom covers already installed, this setup gave me the desired accuracy. Th bottom covers do not turn in the cylinders, so they can be removed an relocated in exaxtly the same rotation.

It's called a slide bar. HTH.

Rudy from Norway · Jan 15, 2024

Finally got some quality time in the shop again. Back on my Twin Launch engine project. Like I have mentioned before, this type of engine is very difficult to make with high accuracy. You are losing the reference points many times from the piston center line and downwards to the crank shaft. Really a challenge for both man and machine.

"Stuart" Twin Launch

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