large lamina flow build

[vamoose]

Sorry to be a distraction and a diversion once again...

[Geoff V]

It doesn't bother me, I am simply being polite to the originator of this thread.

GeoffV

[vamoose]

Geoff,
I appreciate your knowledge, but don't appreciate your continued opportunistic subtle antagonism..
Sorry to all others concerned for my mini outburst..

[Geoff V]

Vamoose

I'm very sorry if I appear to be a purveyor of 'subtle opportunistic antagonisms', it was not, and is not my intention to be antagonistic and am dismayed that I appear that way.

I am very fortunate to have gained some knowledge from very experienced people on the subject of Hot Air engines and wish only to try to prevent members of the Forum from wasting time and money through being misinformed.

There is an astonishing amount of nonsense transmitted on the Internet and that includes this Forum.

If my contributions are considered offensive then I apologise but rest assured my intentions are honourable.

GeoffV

[derwood]

Good to hear from everyone! As far as the correct name for the engine, any of the three is fine with me. I have learned a lot about these engines over the last three months. All trial and error. I have used miles of ss welding wire. I will share some of the things I have learned based on testing with free piston. Choke size does effect stroke length, the smaller the choke the shorter the stroke is. You can also shorten or lengthen the stoke by adding or subtracting weight, The trick is to find the optimum choke size and weight. Decreasing compression also lengthens stroke but also slows the speed. increasing compression shortens the stroke and increases speed.

The amount of air volume between the heat source and head is also important. This also has a direct relationship to stroke length. I have also noticed that when I thin down the heat tube wall thickness my engine will not run. I have tried to reason this out but the only noticeable difference I can actually see is that the portion of the heat tube that glows red is much larger/longer. This is probably due to my large heat source. It does suggest to me that these engines require a hot spot rather than a hot zone. The thick walled stainless tube (exhaust pipe) does work very good. I have also noticed that a slightly leaky piston performs better than a perfect seal. I have not measured the actual speed yet but I have had the stroke down to about 1/8 of an inch and the piston does not even look like it is moving.


Darren Booth

[vamoose]

Vamoose

I'm very sorry if I appear to be a purveyor of 'subtle opportunistic antagonisms', it was not, and is not my intention to be antagonistic and am dismayed that I appear that way.

I am very fortunate to have gained some knowledge from very experienced people on the subject of Hot Air engines and wish only to try to prevent members of the Forum from wasting time and money through being misinformed.

There is an astonishing amount of nonsense transmitted on the Internet and that includes this Forum.

If my contributions are considered offensive then I apologise but rest assured my intentions are honourable.

GeoffV

'OK' i must admit i dropped my pants on this one..
My apologies Geoff. I will try and limit my brain explosions in future.
vamoose

No more Dummy Spit's..

[DavesPlanet]

Derwood,

any status update? Detailed construction specs of the design you have come up with? The theory and process you used to reach the current state of development?

Thanks!
Dave

[derwood]

I had to put this project on the shelf for a while. I have been thinking about going back to work on it soon. These engines seem simple due to the fact that there is only one moving part but in reality the variables seem infinite. I have had time to think and will start testing again soon. If someone could recommend some fairly easy to use software that I could use to make a scaled drawing, then I would post it on this thread. My original goal was to build an engine using off the shelf parts but the piston has to be custom made. Other than that, all other parts can be purchased or easily made.


Darren Booth

[derwood]

I finally got this engine off the shelf to take one final shot at figuring how it functions. I went back, looked at all of my notes and noticed some correlations. I finally figured out how to manipulate heating delay. Just 1/8 inch in tube diameter made it go from not running with a crank shaft to running strong. 3.36 inch diameter piston and a three inch stoke. I think the stroke can still be increased and many other improvements can be made to increase power quite a bit. Here are some vids. One shows the engine compression when it is cold. The other is of it running at 600 rpm.

http://youtu.be/Fvb9RQ6atBk

http://youtu.be/w1p2fIp4amQ




Darren Booth

[Bumpkin]

I'll have to get down to the library before I can watch a video, but thanks for passing your work along - I think a lot of people are watching this closely. Bumpkin

[derwood]

I tried some new modifications and the results were very surprising. I made a simple heat exchanger and thinned the stainless tubing around the heat exchanger. I also added a heat deflector to contain the heat around the exchanger. The result was more power with less heat. It is now running at 700 rpm with a 4 inch stroke. It seems to love compression after you get the proportions correct. It seems that the stoke could be even longer. With a better heat exchanger and better cooling, the power would increase. Also, I might shorten the heat tube a little to increase compression. My son shot the vid and a bit shaky, but you can see the increased power.





http://youtu.be/pOHJLW1osSM

[derwood]

I have made some changes to the interior design. Aerodynamics are very important. This engine contains no steel wool now. Cylinder stays clean and shiny now. The steel wool compensates for bad proportions. There is absolutely no piston wear now that the steel wool has been removed. The noise you hear is a wrist pin with some slack. The mic on the camera is very sensitive and makes it sound louder than it really is. 950 RPM


http://youtu.be/lu2T3HoIcos

[Ian S C]

Derwood, that's great, don't worry too much about the bearing making a noise, it's better that way than too tight, just a drop of oil on it will reduce the noise a little. Some of my engines are similar, mainly slack big ends. Ian S C

[bladeattila]

Hi there,
The engine increased the speed, but heat exchange now not enough fast. I know it is a big deal to adjusting the ideal air flow, also the best heat exchange, but could be include a good heat exchanger. Now you have a good condition of heat contact surface, but not enough big that surface. If you can mill the cylinder, and the bottom then you can increase the heat contact surface. Other thing, the cold heat exchange is more important as the hot heat exchange, because, in this moment you can heat up more than 600 Celsius that tube, (not any heat trap on) and your engine's cold side is not cooled with water ) with also milled surface), just air, actually this is not the best performance of your engine yet.
Very rooting for you! Never give up! You are on the right side! :) Kind regards! Blade

[derwood]

Yes, The heat exchanger has much room for improvement. I have used a small pump to drip water over the cylinder and It will sustain 950 rpms. Eventually I will make a cylinder with a water jacket. using the vw cylinder makes this engine very easy to build and it does run a very long time without water cooling.