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RC Model Steam Project

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rleete:

--- Quote from: Bernd on June 08, 2009, 02:58:16 PM ---Maybe I'll have one rolling by winter. 
--- End quote ---

Yeah, but what year?

You're like me.  The phrase I hear most often from the wife isn't "I love you", but rather "when are you gonna finish _________?"

bogstandard:
Bernd,

If you need any help with the engine design, don't be afraid to ask.

Even a humble oscillator can be made into a very good powerhouse.

This is a picture of the oscillators I make for cash exchange, and the one on the right is designed for a paddler, having a 10mm (3/8") bore and 20mm (3/4") stroke. Very compact indeed, under 5" long X 2" high X 2.5" wide (without the lubricator and width of shaft), but because of the 3 to 1 gearing, at 5psi it is impossible to stop the shafts rotating using your fingers. Unlike most designed 'square' engines, this long stroke is slower revving, and usually a lot more economical with steam. It has great fwds/rev and speed control and it can all be done from one servo.



Maybe something to consider if the 'engine' isn't going to be seen.

Bogs

Bernd:
Thanks Bogs,

I was going to tap your knowledge on this one. SO be prepared for an onslaught of questions. I am definatley thinking of reduction. I'm contemplating using one gear set and then a chain and sproket for the final drive.

As I mentioned at the begining of this post I am thinking of using the size of the engine that is being used on that steam roller. It's a square engine, 3/4" bore X 3/4" stroke. I would use the same boiler as he uses for his steam roller.

I see I didn't mention the size of that roller. It is a  1 1/2" scale model. The model has a total length of 19" long by 7 5/8" wide and 14 3/4" tall over the smoke stack. I'm going to use the layout he uses for the frame. I originally thought of using copper tubing and two I beams to hold the tubing apart. The tubing was going to be used as a storage tank for the butane/propane fuel. Some how the very rough sketches I made of using the tubing for the frame just didn't seem to work out somehow.

Here's my thought on the engine. Twin piston somewhere near the width of the frame. Perhaps horizontal or at a slight angle up to 45 degree. The thing that confuses me a bit would be the reversing linkage. I looked at your "Engine built from Junk" and liked the valve you used on that. No need for a Stevenson linkage. That would work nicely. That brings me to some questions I was going to ask you. Does that control valve need a piston valve engine in order to work? Will it work with a D-valve and if yes, how would you port it?

The bad thing about this project John is that I have a complete 3D vision of the finished product in my head but can't for the life of me draw it on paper to show others. This is going to be a tough nut to crack, so bare with me.

My first thought is to get a rolling frame first and then perhaps mock up an engine using some bit's of wood and cardstock to see what will work. Others will then be able to see better what I want to accomplish.

Your input will be highly valued. Although I might not use all you suggestions, they may help in guiding me through this prject.

Nice looking engines you built there. I really like the horizontal one.

Rregards,
Bernd

bogstandard:
Bernd,

If you mean slide valve when you talk about a D-valve, then no, you cannot reverse a slide valve just by swapping the inlet/exhaust over, it is the way the steam is fed into the chest, and requires mechanical means to swap over fwd/rev, it is done by changing the valve timing.

On the oscillator, it uses a very simple swap over plate that changes the in/ex over, while on the piston valve, it uses a rotary barrel to do the same thing.

So basically if you need to easily swap over fwd/rev, your engine will have to be either an oscillator or a piston valve.

Metal chain and sprocket final drives usually cause havoc with radio gear, producing radio spikes that are very hard to filter out. You can buy small, very strong nylon chains and sprockets that overcome the problem, but they are rather expensive.

I personally think that a 3/4" square engine will grossly overpower this small model, and so waste steam, a 1/2" bore X 3/4" stroke twin would be more than enough. But of course the choice has to be yours.

The whole top end of both engines I showed are exactly the same, and can be swapped back from one to another in about half an hour. That design of engine would be dead easy to change to the size you want as it is already 3/4" stroke. Put a 4 to 1 reduction instead of 3 to 1 and that would drive the wheels direct from a slow crawl to a fast blast. You could easily work out the top speed. Say the top speed of the engine is 1500 RPM (about normal for a low loaded steam engine), divide by 4 = 375RPM. Circumference of say a 6" wheel is for approximations sake 20". Multiply 20" by 375 = 7500 inches per minute = approx 7.1 mph (a steady jogging speed). It all depends on how fast you want to go.

BTW, using a tank for gas as you suggest is highly dangerous. In the UK they have to be made to very high standards and undergo stingent tests before they are allowed to be sold. If a small gas tank as you envisage explodes, an area of at least 20 feet across, maybe more, would be ground zero. So I would suggest a little more thought on that one.

Bogs

DeereGuy:
John I am very interested in your geared horizontal model.  They are both very nice indeed.

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