domingo, 8 de junho de 2014

English translation of the video in which the engine reaches 1860 RPM!

The main change made in this engine, was the reduction of the displacer piston stroke of 28 mm to 20 mm! As a consequence, would have an increase of dead area, and so I increased by 5 mm length of the displacer piston (total 25 mm).

It was also possible to reduce 340 grams to 290 grams weight of the engine, shown in figure 1!

Weight, stirling engine Gama in cans, Manual do motor Stirling
Fig. 1

In the first test, the engine surprised me in its speed, reached peaks 1900 RPM and 1570 RPM constant, these tests were performed in a closed no air circulation (no wind).

After 10 days in total rest, back test it again, keeping up with virtually the same results. As I visualized a future problem in the durability of the balloon, the balloon removed and did wear one with the Dremel in the corner of the rubber (camera bike) that is glued to the cold cylinder, shown in figure 2. Thus avoiding a possible friction and premature wear of the balloon . But to remount this power piston (balloon), the engine surprisingly lost 200 RPM, both in peak and in constant rotations (Peaks 1700 RPM and 1640 RPM constant).

Cylinder of the piston power (engine Gama), Manual do motor Stirling
Fig. 2

After 7 days, I installed of the generator support, and was again surprised with a 100 RPM reduction in peak rotation (max. 1600 RPM), already in constant rotation remained the same conditions "1440 RPM".

Another interesting fact, when I tested the motor with a single candle flame, occurred before the engine ran at 940 RPM peaks and constant 840 RPM. After the problem with the same sail, the engine reaches peak 1000 RPM and 860 RPM constates or more! 

So I was left with a huge question. What could be the possible problem??

My first suspicion is increased clearance of the crankshaft bearings (coins) highlighted in figure 3, because premature wear of the bearings, due to the style that these holes were made. When the engine reaches higher revs, excessive vibration not visible to the naked eye and with a single candle as heat source occurs, the engine does not produce this resonance in the shaft, which could eventually prevent the engine reaches back up the initial rotations. But all this is suspect yet to be tested, for the completion of suspicion.

Crankshaft bearings made ​​with coins, Manual do motor Stirling
Fig. 3

The second suspect is a degradation of the displacer piston steel wool, due to overheating of the same, but for that I need to open the engine again, assess the real situation. As can be seen in figure 4, after disassembling the engine.

Displacer piston steel wool of a Stirling engine, Manual do motor Stirling
Fig. 4

When making adjustments, I also discovered a flaw in the construction of this project. There is a dead area inside the hot cylinder to 13 mm, that explains the reason for the abnormal swelling the power piston, while making the first heating the engine before starting the first match! As the plunger stays away from the bottom of the hot cylinder at a distance of 13 mm, all the air located in this space it expands as seen in the video (there is an increase in air volume due to heating thereof)!

So! I disassembled the engine, which I have not found any more serious damage to piston, only half of the displacer piston met with the intemperate wool. I'll redo a new displacer piston, with a total length of 35 mm and remove dead area within the existing hot cylinder. As we already know that the steel wool does not take up space inside the engine, obviously with this change, I will not remove the existing dead area but will assist in the regeneration of hot air.

I also came to audition with the generator, after the problem occurred, the results were not encouraging, the engine had underperformed the latest version (1600 RPM), maximum capacity of electricity production was 0,220 Watts (3,27 V x 0.066 A) at 927 RPM.

At the moment I will reform and in a next video, I share my accomplishments and frustrations of new results, to discover the real problem. With this project, I still have expectations of obtaining a higher power performance than the previous version, ie the expectation of at least 0,400 Watts!

For those who came to this page via Blog, below is the video mentioned in this text:

Thanks to all who follow this my trajectory!
Regards Leandro Wagner.

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