# Thread: Drop Weight Vs. Crank

1. I question about the TW's test. I just ran a calc on the theoretical tension vs degree from 0. It cam up a perfect match with tension round to 2 decimal pt. I believe physics work, but exact match? I don't buy that. Anyway, I love my drop weight machine over my electric machine for badminton because I don't need to calibrate my drop weight machine. What I did to improve the accuracy is to attach a bubble level like this.
http://www.bhphotovideo.com/bnh/cont...ughType=search
You can get it in hardware store for a lot less. It helps if you really need to get it to exact level.

2. Originally Posted by KooGuy
Someone in TW forum has done similar test and here is the result...

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If you set your reference tension to 60lb and you are off by 10 degrees (above or below horizontal) you are still pulling 59lb of tension. See the table below.

Degrees From Horizontal.....Percent of Reference Tension.....Resulting Tension (60 lb Ref)
1.............................................99.9 8%...................................59.99
2.............................................99.9 4%...................................59.96
3.............................................99.8 6%...................................59.92
4.............................................99.7 6%...................................59.85
5.............................................99.6 2%...................................59.77
6.............................................99.4 5%...................................59.67
7.............................................99.2 5%...................................59.55
8.............................................99.0 3%...................................59.42
9.............................................98.7 7%...................................59.26
10...........................................98.48 %...................................59.09
11...........................................98.16 %...................................58.90
12...........................................97.81 %...................................58.69
13...........................................97.44 %...................................58.46
14...........................................97.03 %...................................58.22
15...........................................96.59 %...................................57.96

A dropweight is about as true as a constant pull machine as exists. you don't need electricity, you don't need and fancy electronics

you will be accurate to +/- 1 lb of reference tension with the arm being off as much as +/- 10 deg from horizontal.

10 degrees equates to the arm being off horizontal by 3 inches up or 3 inches down assuming the arm is about 18" long.
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that isn't a test, he used his calculator to bang out those numbers just like i have in post #26. Just enter degree and press cos (cosine)

3. Originally Posted by silentheart
What I did to improve the accuracy is to attach a bubble level like this.
http://www.bhphotovideo.com/bnh/cont...ughType=search
You can get it in hardware store for a lot less. It helps if you really need to get it to exact level.
If you attach this on the "arm" or the weight, I assume that you need to re-calibrate the machine right after. By attaching additional weight, the original scale will no longer be accurate.

4. Those values have been discussed in this thread,
http://tt.tennis-warehouse.com/showt...rom+Horizontal

I do agreed with the findings (physics or mechanic theory) and certainly can live with anywhere between 0-5 degrees off horizontal which I can eye ball pretty well.

5. Originally Posted by LazyBuddy
If you attach this on the "arm" or the weight, I assume that you need to re-calibrate the machine right after. By attaching additional weight, the original scale will no longer be accurate.
FYI, The one I have weights <10 gram. By attaching it close to the lower weight section (close to the tensioning head) min the issue.

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