[CAUT] F..riction

[Fred Sturm]

Interesting, thanks for posting these. The figures seem to confirm a  
roughly one to one correspondence between hammer flange friction and  
DW. OTOH, they also show something I have noticed about the  
relationship between UW and DW: friction is not symmetrical in real  
life. According to the standard model, add 1 gm of friction and DW  
will go up 1 gm, UW will go down 1 g. But in this example UW is  
affected about half as much as DW, making it appear that BW has  
increased, in every single case. This is in line with my field  
observations, where DW and UW measurements led me to believe there was  
a weight problem (high calculated BW), but when I dealt only with  
friction, I ended up fine and with a significantly decreased  
calculated BW.
	This also occurred when I experimented with clipping weights to  
hammers to try to calculate ratio, adding 1 gm, then 2 gm, seeing what  
my resultant DW and UW were. Inconsistent results, definitely not what  
would have been predicted. This is certainly something to be watched  
for, if you are doing refined touchweight measurements and changes.
	I think that friction at one point probably interacts with friction  
at another, that we can't just look at friction as a monolithic thing.  
For example, flange friction will have an impact on jack to knuckle,  
perhaps, and it might be a different impact depending on direction.  
But that is just speculation.
Fred
On Dec 2, 2010, at 4:15 PM, William Monroe wrote:

>
> I just happened to be finishing repinning a set of hammers, so took  
> the liberty of measuring UW/DW at two different levels of gram  
> resistance in the flange.  FWIW:
>
> Note
> Hammer Flange Friction (g)
> DW
> UW
> Hammer Flange Friction (g)
> DW
> UW
> 3
> 1
> 56
> 34
> 4
> 60
> 32
> 4
> 1
> 55
> 28
> 4
> 59
> 26
> 6
> 1
> 55
> 35
> 4
> 59
> 33
> 8
> 1
> 54
> 32
> 3
> 58
> 31
> 9
> 0
> 54
> 34
> 4
> 57
> 32
> 11
> 1
> 54
> 32
> 4
> 56
> 31
>
> -- 
> William R. Monroe

Regards,
Fred Sturm
fssturm at unm.edu
"Travel is fatal to prejudice, bigotry, and narrow-mindedness." Twain

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