My 2nd LTD engine

[Soeren]

After one year with a lot of breaks and delays finally I got my 2nd DIY project finished. Again it is a LTD gamma engine that runs on a cup of hot water. And again it is made of parts, that you can find in every household. But now it looks much better than the first one (the first one was quite ugly). The used parts are:
* plastic bottle
* several lids of plastic bottles
* lids of gherkin glasses
* ballon
* CD or DVD
* one roulade pin made of stainless steel
* copper wire
* some glas perls
* thick (50µm) aluminium foil (I have tried to implement some kind of regenerator around the displacer plate)
* ... I will write a tutorial how to build this engine and post it here in this topic.

Currently the temperature difference is at least 30 Kelvin. I have started the engine with a cup of boiling water and after the engine stopped running, I have measured a water temperature of 57°C, the ambient temperature was 27°C. Maybe it would be possible to decrease this value with some tweaking - I supect, that the compression ratio is much too large for lower temperature differences.
I was hoping to reach a delta of less than 20 Kelvin, so I am not completely satisfied with the result. But at least it seems to produce some appreciable torque with boiling water, so I am going to try to measure the output later.

And of course I have posted a video on youtube: http://www.youtube.com/watch?v=3JoUVGuIL7k :)

regards
Soeren

[Junkie]

That's a really nice engine. It's inspired me to make one along the same lines, can you tell me what you made the displacer out of ?

[Soeren]

@Junkie: the displacer is made of polystyrene foam.

As promised I have uploaded a detailed description with pictures how to build this engine: http://home.arcor.de/soeren_scharf/Stir ... torial.zip

I think, that the lids of the gherkin glasses are not a good choise, because they are coated with plastic, so heat transfer might be poor. Maybe you would get better results with lids from a cream jar.

regards
Soeren

[jimlarsen]

Your design looks good. You have done well to add the glass bead bearings and put some spring in your connecting rods. It took me a long time to figure out those tricks.

Jim
http://StirlingBuilder.com

[Junkie]

Thanks for the plans really helpful. You should post them on a website like instructables

I will be having a go at building this sometime.

One thing though, I had to rename all of your image files from upper case to lower case to get them to load in the html, could be because I'm using Linux though.

[Soeren]

Hello,

finally I managed to do a small performance test with my engine. I always wondered how much power my engine would produce. So I added a wooden cylinder 6mm diameter to the crank shaft that winds up a thin yarn with a small weight at the end. Then I started the engine and measured the time until the weight was elevated 1 meter. Here are my measurements:
- I started with 5 gramms, it took 20 seconds, water temperature was quit hot (maybe 80°C I guess)
- several minutes later it took 40 seconds, so I refilled with hot water
- when I tried 11 gramms, it was to heavy, maybe the water temp was again too cold at this moment
- I reduced to 9 gramms (and refilled again with hot water), now it took 40 seconds
- The slowest was 60 seconds, but I cannot remember the weight
Ok, now some maths:
0.005 kg * 10m/s² * 1m / 20s = 2.5mW
0.009 kg * 10m/s² * 1m / 40s = 2.25mW

So the engine produced impressive 2mW of output power :-)
I have no idea, if this is good or bad, at least we have some figures now.
The more important point (for me) is, that this kind of power measurement works quit well for these low power engines. The reason is, that I want to make exact measurements with my next engine, where I plan to build the power stroke adjustable. The goal is to produce diagrams about compression ratio, temperature difference, torque and speeds.
The main issues will be to keep the temperatures constant, but that is a different story ;)

kind regards
Soeren

[Doogle]

Only just found this thread. Great intructions on the construction. Many thanks.