I'm all for a second top tube... just one parallel to the other one. Having laterals just seems like waaaaaay overkill. I guess for heavy-leaded expedition touring to Siberia it makes sense, but for the other 99.5% of the time...
On Sat, Apr 3, 2010 at 7:55 PM, CycloFiend <[email protected]> wrote: > on 4/3/10 5:22 PM, cyclotourist at [email protected] wrote: > > I question how many Bombadil frames are cracking in half due to lack of > stiffness. > > Well.... arguably, "stiffness" is what would cause things to crack in half > - an inability to transfer force so it gets concentrated to one specific > area. In short, a materials introduced "stress riser". > > If I understand GP's comments and thought process correctly, the reasoning > for the second top tube is to create two trusses where there is one. That > stiffens the structure, but doesn't necessarily make an unyielding - i.e. > "stiff" structure - it passes the stresses along the structure. Even if you > use thicker, stiffer tubing, you still join a traditional bicycle frame at > discrete points - the headtube, seat cluster and bottom bracket - six points > to be exact. The stiffer and less yielding the tubes are, the more stresses > are on the connection points. > > I would _suspect_ that adding a second top tube lets you use lighter top > tubes so they can flex and disperse stress, while at the same time you are > stiffening the structure without adding stresses to the joints. > > Since any force is distributed through the frame, then force "X" would be > distritbuted over a greater number of tubes _and_ joints, it would seem to > end up with less stress on each. > > Just thinking out loud here... > > - Jim > > > -- > Jim Edgar > [email protected] > > Cyclofiend Bicycle Photo Galleries - http://www.cyclofiend.com > Current Classics - Cross Bikes > Singlespeed - Working Bikes > Workshops of the iBob's > > Send In Your Photos! - Here's how: http://www.cyclofiend.com/guidelines > > > "My nighttime attitude is anyone can run you down and get away with it. > That's why I don't even own a bike light or one of those godawful reflective > suits. Because if you've put yourself in a position where someone has to > see you in order for you to be safe...you've already blown it." > -- Neal Stephenson, "Zodiac" > > -- > You received this message because you are subscribed to the Google Groups > "RBW Owners Bunch" group. > To post to this group, send email to [email protected]. > To unsubscribe from this group, send email to > [email protected]<rbw-owners-bunch%[email protected]> > . > For more options, visit this group at > http://groups.google.com/group/rbw-owners-bunch?hl=en. > -- Cheers, David Redlands, CA "Bicycling is a big part of the future. It has to be. There is something wrong with a society that drives a car to workout in a gym." ~Bill Nye, scientist guy -- You received this message because you are subscribed to the Google Groups "RBW Owners Bunch" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.
