Vtec44
02-24-2008, 03:05 AM
Center Of Gravity Numbers, And Bike Chain - Ask The Geek
http://images.sportrider.com/images/146_0711_01_z+ask_the_geek+richard_koch.jpgRichard Was Busy This Month
Of the three motorcycle magazines I currently subscribe to, Sport Rider invariably delivers the best comparison information and test data of the three, period. I especially like the performance data you provide with your model comparisons. Rather than a lot of seat-of-the-pants subjective opinions, your staff provides graphs and charts to show why one bike is faster or laps quicker than another. As an engineer, this is the stuff that makes your comparisons meaningful and provides objective credibility to your bike recommendations.
However, there is one bit of data that you and your competitors are woefully lacking, that being the vertical and horizontal locations of the center of gravity of your test subjects as a means of explaining their various handling characteristics. Rather, there will be some type of vague reference to lower center of gravity or weight bias toward the front or rear that really tells the reader nothing. I find this omission very frustrating because it would be so easy to get this information with three scales, a plumb bob and tape measure. As the old saying goes, "data talks, and BS walks," or something like that.
Richard Koch
Keller, TX
We have listed center of gravity numbers in the past-way back in '02 we measured some bikes and printed the results as part of our open-class shootout ("Target Fixation," August '02). Since then, we've sporadically measured and printed CoG numbers, especially if one bike was significantly different from its competitors in that aspect. It's easy enough to find the horizontal position of the CoG, and we often list that as a percentage weight distribution. The trouble we found with measuring CoG height, however, lies in the observer effect. Finding the vertical measurement requires raising one end of the bike on a ramp, hanging the bike from a fixture or laying it down on three scales. Changing the orientation of the bike to take these measurements moves the oil, fuel and other fluids to a different position, which we've found is enough to affect the results.
One solution is to drain the oil and fuel before taking the measurements, but then the numbers don't represent the real world. Each bike would be affected differently, skewing the results to the point that they are unusable for the purposes of comparison. Once we realized we didn't have a reliable, accurate and repeatable way to find a bike's true center of gravity, we stopped running specific numbers in the magazine.
Chain Letter
I have a 2000 ZX-6R, and my chain seems like it wears out quickly. I replace the chain every year and put about 10,000 miles on it each year. This time when I got ready to replace it, the sides of the sprocket were chewed up, and I thought my wheel might be out of alignment; but I checked that and it was fine. I also clean my chain regularly. Should my chain wear out that soon, or could something be wrong?
Tiffany Barlow
Lashmeet, WV
On a bike that is used mostly for commuting and street riding, a well-looked-after chain should last quite a bit longer than 10,000 miles. We've seen chains in great shape with more than double that. Your letter indicates that you are only replacing the chain each year without changing the sprockets, and that is most likely why the chain wears out so soon-worn sprockets will quickly beat up a new chain. Invest in a good-quality O-ring chain in the same 525 size as the original and replace the sprockets at the same time. Be sure to use a steel rear sprocket for the best mileage. Check and set the chain's tension according to your owner's manual and clean and oil it regularly using a cleaner and good-quality lube that are safe for O-ring chains.
Photo Gallery: Center Of Gravity Numbers, And Bike Chain - Sport Rider Magazine (http://www.sportrider.com/tech/146_0711_ask_the_geek)
http://images.sportrider.com/images/146_0711_01_s+ask_the_geek+richard_koch.jpghttp://images.sportrider.com/images/146_0711_02_s+ask_the_geek+2000_zx_6r.jpg
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http://images.sportrider.com/images/146_0711_01_z+ask_the_geek+richard_koch.jpgRichard Was Busy This Month
Of the three motorcycle magazines I currently subscribe to, Sport Rider invariably delivers the best comparison information and test data of the three, period. I especially like the performance data you provide with your model comparisons. Rather than a lot of seat-of-the-pants subjective opinions, your staff provides graphs and charts to show why one bike is faster or laps quicker than another. As an engineer, this is the stuff that makes your comparisons meaningful and provides objective credibility to your bike recommendations.
However, there is one bit of data that you and your competitors are woefully lacking, that being the vertical and horizontal locations of the center of gravity of your test subjects as a means of explaining their various handling characteristics. Rather, there will be some type of vague reference to lower center of gravity or weight bias toward the front or rear that really tells the reader nothing. I find this omission very frustrating because it would be so easy to get this information with three scales, a plumb bob and tape measure. As the old saying goes, "data talks, and BS walks," or something like that.
Richard Koch
Keller, TX
We have listed center of gravity numbers in the past-way back in '02 we measured some bikes and printed the results as part of our open-class shootout ("Target Fixation," August '02). Since then, we've sporadically measured and printed CoG numbers, especially if one bike was significantly different from its competitors in that aspect. It's easy enough to find the horizontal position of the CoG, and we often list that as a percentage weight distribution. The trouble we found with measuring CoG height, however, lies in the observer effect. Finding the vertical measurement requires raising one end of the bike on a ramp, hanging the bike from a fixture or laying it down on three scales. Changing the orientation of the bike to take these measurements moves the oil, fuel and other fluids to a different position, which we've found is enough to affect the results.
One solution is to drain the oil and fuel before taking the measurements, but then the numbers don't represent the real world. Each bike would be affected differently, skewing the results to the point that they are unusable for the purposes of comparison. Once we realized we didn't have a reliable, accurate and repeatable way to find a bike's true center of gravity, we stopped running specific numbers in the magazine.
Chain Letter
I have a 2000 ZX-6R, and my chain seems like it wears out quickly. I replace the chain every year and put about 10,000 miles on it each year. This time when I got ready to replace it, the sides of the sprocket were chewed up, and I thought my wheel might be out of alignment; but I checked that and it was fine. I also clean my chain regularly. Should my chain wear out that soon, or could something be wrong?
Tiffany Barlow
Lashmeet, WV
On a bike that is used mostly for commuting and street riding, a well-looked-after chain should last quite a bit longer than 10,000 miles. We've seen chains in great shape with more than double that. Your letter indicates that you are only replacing the chain each year without changing the sprockets, and that is most likely why the chain wears out so soon-worn sprockets will quickly beat up a new chain. Invest in a good-quality O-ring chain in the same 525 size as the original and replace the sprockets at the same time. Be sure to use a steel rear sprocket for the best mileage. Check and set the chain's tension according to your owner's manual and clean and oil it regularly using a cleaner and good-quality lube that are safe for O-ring chains.
Photo Gallery: Center Of Gravity Numbers, And Bike Chain - Sport Rider Magazine (http://www.sportrider.com/tech/146_0711_ask_the_geek)
http://images.sportrider.com/images/146_0711_01_s+ask_the_geek+richard_koch.jpghttp://images.sportrider.com/images/146_0711_02_s+ask_the_geek+2000_zx_6r.jpg
Read More (http://www.sportrider.com/tech/146_0711_ask_the_geek) | Digg It (http://digg.com/submit?phase=2&url=http://www.sportrider.com/tech/146_0711_ask_the_geek&title=Center Of Gravity Numbers, And Bike Chain - Ask The Geek) | Add to del.icio.us (http://del.icio.us/post?url=2&url=http://www.sportrider.com/tech/146_0711_ask_the_geek&title=Center Of Gravity Numbers, And Bike Chain - Ask The Geek)
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