Weight Distribution

As I discussed in the last post, I am trying to optimize weight distribution for this bike. To that end I need to know where my center of gravity is when in riding position, or at least where a vertical line that passes through my C of G is. I'm not going to worry about the weight distribution of the bike itself since that would add a huge amount of complexity to the process (without actually having the bike yet) and really it would only change the result by a pound or 2 in either direction which isn't enough to matter.

To do this I basically took a mockup bent seat I built previously that is set at 28deg from horizontal when sitting on a flat surface. I put it on a pair of 2x4's that were supported at the ends by a bathroom scale on one end and some scrap on the other to make it level. I put it roughly in the middle but just marked it so it's position is known. I then took 3 sets of readings 1 each with me on the contraption and with me off of it. I then swapped the scale to the other end and did another set of readings. Here is a link to my raw data.


As you can see I had some help with this. Also the living room is not really as much of a disaster as it looks in the pics. I swear!



Looking at the data. We take the average of the loaded measurements and subtract off the average of the unloaded measurements for both front and back respectively. This gives us 102.33 lbs on the front and 81.66 lbs on the back. So 55.62% of the weight was on the front. The 2x4's were 206cm between the measurement points. So to calculate the c of g, we take (100%-55.62%) * 206cm = 91.42cm which is the distance the c of g is from the front of the 2x4. We also know that the seat reference mark was 87.45cm from the front. So my C of G is 91.42-87.45 = 3.97cm behind the seat reference mark. Good to know!