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View Full Version : Klippermate stringer. Doesn't make sense?


Tenny
03-22-2004, 10:16 AM
Hi

I have a klippermate stringer-drop weight system. I don't understand how it works. I am supposed to adjust the tension by adjusting the location of the weight (The bar has marks which shows where I should put the weight). But I am supposed to pull the string by 'dropping' the weight until the bar is parallel to the floor. I just lower the weight-bar.

In my opinion it doesn't matter whether it is 80LB or 40LB if we pull the string to the point-parallel to the floor. Different angle of the bar (extend of pulling) dropped can make the difference but not the weight itself. As a result, all the racquets I strang myself feel similar (like 60-62LB) whether it was 55 or 62. Am I missing something? The machine has been quite popular. Any help will be appreciated!

TENNY

Gaines Hillix
03-22-2004, 10:23 AM
Tenny, you are supposed to let the bar drop until it's parallel with the floor on its own. Do not pull on the bar. The weight controls how much leverage the arm has on the string gripper/tension head.

Grimjack
03-22-2004, 11:42 AM
Simple physics demonstration:

Stick your left arm ram-rod straight out in front of you, and make a fist. Turn your fist sideways, like you would if you were about to hold a candle, or pull a level. Your arm will be straight, and in a very firm position -- just like the rod on your Klippermate.

Now using your right hand, gently but firmly press down on your biceps area, and resist the movement with your left arm. You'll feel a small amount of pressure, but not much. Now, press down using about the same amount of pressure near your elbow. This time, you'll have to resist a little harder to keep your left arm still. Now, once again using similar pressure, press down all the way at the end of your arm, down by your fist. You'll find that the same amount of downward pressure exerted at the end of your arm (lever) requires a GREAT deal more resistance in order to keep your arm still.

Think of your left arm as the lever, and your shoulder muscles/tendons as the string. The amount of weight on the sliding metal counter-weight is always the same, as is the angle. But when the weight is placed closer to the joint, the outward pull on the string is very slight. As it's moved further out, the outward pull on the string becomes much greater. Even though the angle of the lever and string (as with your arm and shoulder) stays the same, the pressure exerted (tension) goes up. 8)

Grimjack
03-22-2004, 11:50 AM
So anyway, it DOES make sense. The thing is, the difference between 55 and 60 isn't all that great, and even if you string very carefully, it will be very difficult to tell the difference by hand.

Use the stringer with confidence, though. The immutable laws of physics are on your side.

Tenny
03-22-2004, 01:25 PM
Hi Gaines Wow you are everywhere giving out your priceless knowledge. Thanks Grimjack. You went through all the trouble typing that detailed demonstration.

I guess it's because I am a biochemist, not a physicist...
Still I don't get it (I am hopeless?).

Whether it's 55 or 65, if we start from same point (I pull the cross string by hand or do it slightly with the stringer until it becomes 'straight'. I also feel how I use string gripper really matters. If my initial pulling to make it straight is too tight, the final tension will be higher), the rotation of the bar with weight and string gripper in terms of ANGLE will be exactly same (like about 100 degree until it reach the parallel point). Whether it is 55LB or 65, the weight will pull the string to same extend if

1. Same starting tension (by pulling by hand to make it straight otherwise there is no way to make all the cross string tension even?)
2. Same starting point of bar
2. Same ending position (parallel to the ground).

I think 'drop weight' is the key as Gains said. Only if we let it drop (I didn't pull to the parallel. I just gently support the weigth until it reaches the parallel position as the manual) until it reaches is 'equilibrum' state. Like... 55LB NATURALLY stops at 30degree from the ground while 65LB NATURALLY stops at (-) five degree past zero degree by gravity. Then I cramp it. Now it makes sense to me. BTW, 'Drop' intrigues me too. Should I let it really drop freely? It can break the string or can reach too far. It's a really heavy piece of metal. :shock: :(

Grimjack
03-22-2004, 02:15 PM
Right. Every string has a natural elasticicy. Since sliding the weight out further creates more downward force, to get the string to stop the fall of the weight at just parallel to the floor, you need to feed in a bit more string to get a higher tension.

The result is that with a higher tension, you feed a slightly higher % of the string's total length through the lever assembly. The string left behind (being tensioned) will be a wee bit shorter for a higher tension, but will be stretched a wee bit more to make up for it.

edge
03-22-2004, 03:13 PM
That's why drop weight sreingers are a PITA and inaccurate.

Tenny
03-22-2004, 04:34 PM
Thanks Grimjack.

Let me use your left/right arms analogy.
I clearly understand that I will need more power to resist the same amound of power if it is applied to the end of my left arm (or closer to my fist). OK.

Let's say I am holding my left arm at 45 degree upward. Now we apply same amound of force (same metal weight) to my left fist or around my elbow. My left arm is now parallel to the ground (This is the point of my mystery). I understand more resistance/more power to resist but anyway, when my left arm "is parallel" to the ground whether the metal is hanging at my fist or at my elbow, the extension of musles around my shoulder should be same...because both started at 45 degree and now parallel to ground. Although I would feel more fatigue with metal at my fist. So my poorman's stringer design is (^^)

Instead of varing the position of metal on the bar, we can use just weight at fixed distance of a metal bar. Then we do the same thing on table not on the floor in case I will have to go further past the parallel because I want 95LB. The machine will have a degree indication like if the bar reaches 13 degree it is 55LB. If it is 0 degree, it is 65LB and so on (actually we pull it down to the point if it doesn't go down naturally and metal is just helping to pulling the string). Or just buy a expensive machine 'pulling' cystem. I think Pulling at a centain tension is the way for sure. Oh, I am confused... thanks Grimjack. I will read your post again very carefully.

Gaines Hillix
03-22-2004, 05:06 PM
It may be easier to understand using a description of how a drop weight machine with a clutch in the tension head works. The arm on these is raised to the vertical position, the string is wrapped around the head and inserted into the jaws of the string gripper and then the arm is lowered. The weight was set to the reference tension to begin with of course. If the arm goes past the horizontal position, the tension head is held and the arm is raised up again, but to a lower angle. Then the arm is lowered again. This is repeated until the arm stays in a horizontal position and the string is them clamped off. The difficulty with a Klippermate is that the head doesn't have a clutch or ratcheting mechanism to allow the head to be held in place while the arm is raised again. On a Klipper, the string has to be released and more tightly pulled and rewrapped if it goes past the horizontal. Conversely, if the bar stays above the horizontal position on the first pull, more slack has to be left in the string while it's be wrapped around the head. There is no question that the arm and weight and head will pull the string the set number of lbs. when the bar is in a horizontal postion with the ground.