Frequency of a spring?

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sophiecentaur
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Here at TorqSoft we have found that the natural frequency of the reeds should be between the values of 0.75 to 1.25 times the fundamental frequency of the engine peak power speed. Hence if an engine gives its peak power at 12000 revs/min its fundamental frequency is 200 hz. Therefore the natural frequency of the reeds should be between 150 hz and 250 hz”.
That's interesting. Seems to me that it's Rise Time, rather than resonant frequency that counts. The valve doesn't follow the whole or even half a sinusoid. A normal poppet valve doesn't open with a sinusoidal time function, cams have all sorts of strange shapes for power and efficiency.
 
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From my 2 cycle outboard race days reeds were carefully monitored and played with type, thickness, reed stop length and reed max opening as well as reed cage landing surface texture for holding oil for a reed landing cushion. Stock engines were required to use SS modified engines used fibre reeds of different materials.
Although for 2 cycle engines this software may provide information on reed frequency. Purchase required for the software.May or may not not relate to the reed material you are using?Not discussed what frequency formula used for the calculations. Maybe if purchased?Reed valve theory and performance
http://torqsoft.net/reed-petal-design.htmlFrom the program:The stiffness of the reed petals in a high performance reed valve induction two-stroke engine has a dramatic effect on the power output. The stiffness not only influences the amount that the reeds open but also the natural frequency of the reeds. Three main factors influence the stiffnessReed Petal Materia
The Reed Petal Design Programme calculates the natural reed frequency, reed deflection and tip ratio. These values provide a valuable indicator as to the direction that reed development should proceed for optimal performance.Here at TorqSoft we have found that the natural frequency of the reeds should be between the values of 0.75 to 1.25 times the fundamental frequency of the engine peak power speed. Hence if an engine gives its peak power at 12000 revs/min its fundamental frequency is 200 hz. Therefore the natural frequency of the reeds should be between 150 hz and 250 hz”.



I built a go-kart with a 4 cylinder mercury outboard engine these engines have reed valves stronger reeds make higher rpms. I tried the Mark 55 and the 65 hp engines. The 55 is a high rpm racing engine it produces as much hp at the stock 65 engine. The power head on the outboard motor only weights 40 lbs. I built an open exhaust, and mounted the engine on its side behind the seat. Water pump form a toyota truck and radiator cooling system. Disc brakes from a small truck. Gear ratio 3.2 to 1. The 65 hp engine produced about 80 hp using 80% gasoline mixed with 20% diesel fuel it was fast direct drive with no clutch engine idle at 5 mph, punch the gas it go to 78 mph in 3 seconds. G forces made my eyes cross I had to close 1 eye to drive. I built 3 go karts one with 55 hp and 2 with 65 hp engines. I sold 2 and several people in the area built about 18 of these go karts we raced them every Saturday night for 3 years. People lost interest we stopped racing about 10 years then started racing again for 2 years and quit. That was 15 years ago. I sold my go kart i need for floor space in my work shop more than the go kart. I wish I still had it to ride sometimes it sure was fun. I have pics on my computer that crashed. I think I have a pic on photo bucket I will link it here soon as I find it. Photo bucket is not free anymore I have to pay money to look at my own pics or down load my own pics so I took a photo of my the computer monitor with the go kart pic.

00000_jSZHwmXjvaW_1200x900.jpg
 

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