Here's one way to do it
http://www.angelfire.com/ca4/CorvAIRCRAFT/RodBalance.html
. I've had good luck with simply placing the rods on a crankshaft
with no bearing and weighing the small end, then placing the small end
on a wrist pin and weighing the big end. Perhaps because the rods I
use are a smooth enough circle on the outside of both the big end and
small end that as long as the rod is horizontal, I'm probably not
having much variation in the lever length--at least not enough to
measure. But then I never tried to do anything more precise, so I
might be off more than I think.
Seems like using a knife edge and a pivot rod would have the same
inaccuracies--the placement of the knife edge or rod will determine
the length of the lever the weight acts through. I didn't think about
this until Larry talked about his method, but it might be worthwhile
to build the jig shown in the link.
On Oct 26, 2008, at 3:25 PM, Larry Young wrote:
> I should have added that the part which is not on the scale should
> also be resting with the pin center on something that approximates a
> knife edge.
>
> Larry Young wrote:
>> To finish this description. The fulcrum point gives the center of
>> gravity. You then divide the total rod weight by the fraction
>> distance from crankpin (center) to center of gravity and wrist pin
>> (center) to center of gravity.
>> You can also do a direct measurement. Lay a thin rod (I use a
>> finishing nail) on your scale. Rest the small end on a block next
>> to the scale and the big end so that the nail is lined up with the
>> center of the crankpin. This way you know you are measuring the
>> weight at the center of the crankpin. Reverse the ends and measure
>> the small end weight. If you do it right, the two weights should
>> add up to the total rod weight.
>>
>> Both of these methods should give similar results.
>> Larry
>>
>> Steven Preiss wrote:
>>> Probably does it by finding the balance fulcrum and measuring the
>>> distance
>>> from either end.
> _______________________________________________
> Support Team.Net http://www.team.net/donate.html
>
> http://www.fot-racing.com
>
> Fot mailing list
> Fot@autox.team.net
> http://autox.team.net/mailman/listinfo/fot
>
Bill Babcock
Babcock & Jenkins
Billb@bnj.com
503.936.7660
www.bnj.com
Editor
Ke Nalu e-Magazine
Paddlesurfing's Web Journal
Bill@kenalu.com
www.kenalu.com
blog: www.ponohouse.com/ponoblog
_______________________________________________
Support Team.Net http://www.team.net/donate.html
http://www.fot-racing.com
Fot mailing list
Fot@autox.team.net
http://autox.team.net/mailman/listinfo/fot
|