Drop Weight: How important is it to parallel the bar?

Xfimpg

Professional
#1
With a drop weight stringer, how important is it to have the tensionning bar absolutely parallel to your table before clamping?
Has anyone ever performed any tests, i.e. Racquettune, to determine if there is some margin for error?
 

BlueB

Hall of Fame
#4
Get it to within few degrees to parallel. Its quite important.
Lesser angle gives you a shorter lever.

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Traffic

Hall of Fame
#5
Another factor to consider is how many iterations of drops does it take to get parallel. If it takes you 4 attempts to get near parallel vs 1 attempt, you will have different final tension as you've completed additional pulls on the former attempt vs the latter.

Also, if you stare at your DW as it slowly moves towards parallel vs hitting it perfectly and clamping immediately will yield different final tension.

So you want to have consistent drop attempts and time from pulling tension to clamping.

In my own stringing, I try to get my bar parallel in 2 attempts. I usually clamp off about 8 sec after I start pulling. And this is repeated each time for consistency.
 

eelhc

Hall of Fame
#7
No math or physics necessary...

When I had a dropweight... I used a luggage scale and Kevlar string to test this. With my machine (Alpha Pioneer DC plus at the time), I really don't have to nail it to perfect horizontal. YMMV with your machine.

That said... with a ratcheting drop machine... it may not be possible to get to spot on horizontal
 

BlueB

Hall of Fame
#8
If it takes you 4 attempts to get near parallel vs 1 attempt, you will have different final tension as you've completed additional pulls on the former attempt vs the latter.
This doesn't stand from physics point of view. You can do 100 pulls at 50lbs, the tension will still be 50lbs... The only thing that changes, especialy with polys, is that you defacto performed a prestretch, so the drop in tension after the stringing will be less.

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#9
Very true. Pulling 1x, 2x, 3x at ref tension can only yield ref tension as a final result. The only thing that changes is the amount of easily plastic deformation left in the string when done. I prefer that amount [static tension loss] to be minimal. I absolutely do not want to guess what's left. To be fair, almost every piece of string gets pulled at least twice using any machine. The piece of string between the clamp and gripper is always pulled again in the next main or cross. So when folks say 'pull only once' gets only a nod from me. I know better.
 
#10
So is there more tension on the string when the bar sits above horizontal or is there more tension when it sits below horizontal?

I would think more tension when it sits below horizontal, but then there is the whole clutch factor going on as well...
 
#13
So is there more tension on the string when the bar sits above horizontal or is there more tension when it sits below horizontal?
Neither. It is an arch, with the "high point" being horizontal (point furthest away from center. Esgee is saying if you are 10 degrees off (+ or -), you are at 98.5% of reference tension. That percent would go down (less tension) the further away from horizontal the bar is. A DW can't tension a string MORE than the ref tension the weight is positioned at. It can only be AT or below, depending on the position of the swing arm.
 
#19
The ML90 is what I would label an Automatic DW. Any angle close to horizontal ±45 degrees is probably going to be correct. Only thing I do not like about them is lack of a scale. You have to measure the distance, then set the weight. What can I say? I am LAZY!
 
#22
This seems contradictory. Shouldn't the resulting weight be off then?
The Stringway system claims to be able to have the tension bar at various angles and still pull the same tension.

I tried the test and it appears their claim is valid. I've had my stringway ML90 about 10 years or so now and have been very happy with it.
Especially love the flying clamps.

I have also used it to string some of my wood racquets. (some with synth gut and some with gut)
 
#23
There is NO CONTRADICTION. Auto DW cost $$ vs regular DW which cost $. The design of the tensioning assembly is totally different. You can look for schematics.

Using consistent technique as well as a "horizontal bar" will yield consistent results. You can have the "horizontal bar", but bad weaving, or slipping clamps etc and your results will not be consistent. The finished product should be at the same DT if stringing up multiples of the same frame at the same ref tension using the same string. If you can't do this, then you need to work on your stringing techniques.
 

max

Hall of Fame
#24
No math or physics necessary...

When I had a dropweight... I used a luggage scale and Kevlar string to test this. With my machine (Alpha Pioneer DC plus at the time), I really don't have to nail it to perfect horizontal. YMMV with your machine.

That said... with a ratcheting drop machine... it may not be possible to get to spot on horizontal
. . . did you have a Gamma DW? I have a Kmate, so there's no ratchet mechanism. I can get spot-on parallel. Does the ratchet gearing mean the weight can't be so micro-adjusted?
 

eelhc

Hall of Fame
#25
. . . did you have a Gamma DW? I have a Kmate, so there's no ratchet mechanism. I can get spot-on parallel. Does the ratchet gearing mean the weight can't be so micro-adjusted?
I've had Gamma and Alpha dropweights. In some instances, the bar will end slightly below horizontal... If one goes 1 more ratchet... the bar will be slightly above horizontal. Does it matter in the end result/tension? In my measurements with a luggage scale, no.

That said, I am of the opinion now that a stringer skilled with the use of the non-ratchet dropweight (Kmate) can actually be more consistent. I've watched a guy string with a racquet and string he was familiar with and basically nailed spot on horizontal on every pull without loosening/regripping. We've discussed this to death here but IMO working the string several cycles on each pull (via ratchet or regrip) will result in inconsistent results. Folks mistakenly equate a dropweight to a constant pull which is not at all true unless it's an automatic (Stringway).
 
#26
It's really not important if you're not concerned with the tension. Too high, the tension is too low. If you let it drop lower than horizontal, the tension is too low also. It just takes practice.
 
#27
It's really not important if you're not concerned with the tension. Too high, the tension is too low. If you let it drop lower than horizontal, the tension is too low also. It just takes practice.
True the closer to horizontal the closer the tension is to set reference.
 
#28
Of course, if it is above horizontal, and you push it down to horizontal, you could see what it feels like when a string breaks while stringing. May even break a racket.
 
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