Quote:
Originally Posted by Mark O'Neal
1> Balancing to within one gram. Pretty much no one does that. Even if you do, balance is an estimate. Once oil starts flying around no one really knows what that bob-weight is within a gram........or 20.
2> If you were to balance a rotator on our machine, then go re-do the bob-weights and run it on another machine, you would get a different result. Every time.
It's nowhere near as precise as you fantasize. And yes, I'm certain, having done tens of thousands of balance jobs (and engine builds) over the decades. |
Mark,
I am surprised that you don’t believe it is possible to balance within a gram. I’ll demonstrate for you how the average site member can do this with a rod balancing fixture, a gram scale, and a spreadsheet. The following numbers are the actual weights of the components in my engine.
I used out-of-the-box Manley 14044R-8 connecting rods, out-of-the-box Arias pistons and pins, out-of-the-box TotalSeal AP Steel top rings, Napier cut cast iron seconds and 3mm oils along with double Spirolox® pin locks. The bearings used were narrowed small pin SBC bearings again out of the box from King Bearings.
I start by weighing all the individual components and recording their weights in an XL spreadsheet (see pic below)
Those weights, other than connecting rods, were recorded in columns B through H and rows 7 through 28. Connecting rod weights were recorded in columns I through N and rows 7 through 14, and rings were accounted for in columns B through D and rows 33 through 35.
The next step requires some basic four-function math to find the lightest and heaviest rods by both total weight and end for end weight. I used control letters A through H to identify the individual components and then matched light and heavy components in columns I through N and rows 21 through 28 to get my final bob weights.
I want to draw your attention to the bob weights in the green fields. The heaviest bobweight is 1696.72 grams, and the lightest bob weight is 1695.54. Now I understand you can be math challenged, so I will do the math for you (again). 1696.72 minus 1695.54 is 1.18 grams. Now, again, I do recognize your handicap with respect to numbers. However, 1.18 grams is, you guessed it, 1696.19 grams +/- 0.59 grams or
less than a one gram variation bob weight to bob weight!
The best part is that I did not have to do any barbaric grinding on any component to achieve this end result. Now I recognize this is very different from your experience because you already told us it is.
You might want to be a little more circumspect before you unilaterally toss out someone's freely offered guidance or help for others. You do a considerable disservice to the readership with your uninformed and unfounded proclamations other than your own less than adequate efforts.
The average enthusiast on the site here can obtain all the necessary rod and piston balancing tools for around $300 (maybe a little less) and balance his entire assembly far closer than a guy like you would do (or more likely, by your own personal admission, could do). Even worse you would attempt to convince them that they couldn't do it either.
When Winberg did my crank, I gave them the bob weight to balance the finished shaft to. When they sent the crank to me, they told me they had gotten to within 5 grams (maybe less, I don’t recall anymore) on the flywheel end and zero grams on the snout.
And yes, I almost forgot, I did spin the crank back in California when it arrived, and surprise, surprise, it was within less than a gram of what Winberg told me it would be. So much for repeatability machine to machine.
Now I recognize that comparing this to what you do is not entirely fair. It is more like comparing a butcher to a brain surgeon, but then again, you chose to be what you chose to be. That doesn’t mean the rest of us have to set our sights and standards as low.
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