On 1/19/2012 8:03 AM, Dean May wrote: > I'm having trouble understanding so I'm going to risk asking a stupid > question. Could you or someone explain why the too heavy spring could be the > problem? I understood the complaint to be the jack would not slip under the > knuckle. Seems like too much rep spring tension would assist in holding the > rep lever high to make it easier for jack to return, not more difficult. > > Thanks in advance. > > Dean Sorry, been out bustin' inharmonicity. Dean, While there most certainly are such things as stupid questions, this isn't even close. We're talking about spring rate, which is specified as units of deflection per unit of weight, or how much a spring deflects under a given weight. So a high rate spring will will be stiffer than one with a low spring rate. In a repetition lever, we need a specific force over a broad range of spring travel. If the spring rate is too high, the force exceeds what we want as the spring is compressed, and we get the choice of too much spring force at the bottom limit of spring travel, or too little at the top. The power curve is too steep. A lower rate spring (lighter spring) will give a less steep power curve through the spring travel so we can get controllable and adjustable power throughout the stroke. Too low a spring rate may not give you adequate power at the bottom to get things moving, and will over stress the spring. So the spring rate should be chosen to accommodate the power requirements through the range of movement of the mechanism. This gives longest spring life, most dependable function, and easiest adjustment. This is the extremely shortened version, but it's the gist of it. I can get more detailed if you need. Ron N
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