Tuesday, November 30, 2010
Friday, November 26, 2010
Standard tubes
Most commercial tubes are put together with a 180/90 degree layup which is really strong against bending forces, decent against crushing, but isn't designed to specifically deal with the twisting forces often found in bikes. The down-tube in partciular has a twist-resist function as well as it's bending resistance.
Experimenting
Looking to try some different layups with this latest batch of carbon from Enve Composites. Carl at Enve laid up a goodly set of 45 degree cross ply tubes and I'm going to use those in my next project: a road bike for my teammate Jerry. You can see that the fibers run differently from the previous picture.
Daruma Cross Evaluation
The beta-testing phase of Daruma Cross has been pretty good. Overall, I like the bike much more than my previous too-small cyclocross frame. I think that this hits a bit closer to the mark for "excellent cross bike" than does my road bike. The bike is extremely stable, especially at speed. I'll be looking for a slightly shorter fork to hopefully make things a bit quicker at slow speeds. Ride quality is what I've come to expect from bamboo: silky. I know that low-pressure tires make a huge difference, but even with my Maxxis Mimo's pumped to 55 psi, the bike rides smoothly over road bumps and even turf. I've also decided that I must have done some things right, because I've never been quite so easily able to land every one of my running remounts. I'm also pleased that there has been zero complaint from the seatpost/mast area either. I believe stiffness to be good, though I occasionally do hear some rear brake rub. That could be partly due to flexing wheels, but it's hard to say until I switch those out for something that is known to be super stiff. I'm willing to concede a bit of stiffness for the ride quality though, it's nice not to be pitched all over creation.
Each one of the bikes that I've made for myself could be better in some ways though. I guess it really boils down to needing to get better at bike frame design. When building bikes for myself, I tend to follow my standard recipe technique: look for all of the things that I think are cool, try to slap them all together, and then throw a bit of experimentation in for good measure. Ask anyone that's tried my cooking.
In both of these bikes, I made some really long top-tubes to help accomodate for my preferred mid-foot cleat position. In the case of my road bike, I was pretty much spot-on with the length, but a slight miscalculation in which forks were available to me, left me with a steeper-than-desired headtube. It gets a little quick steering, though still within reason, until you're going at speed. My other miscalculation has more to do with a lack of understanding of the inherent flexibility of bamboo. I got all artsy with the seat stays and picked some nicely re-curving sections, but at the end of the day, I really probably should have gone with some stouter bits to boost the rear-end stiffness a bit.
As far as my quibbles with the D-Cross, it seems that I could have made the top tube about a centimeter shorter, and probably could have done something similar to the chainstays. My design goal was really to make something that would absolutely not have any toe overlap, and given my big hooves and mid-foot cleats, this required some extra length in the front end. I was prepared to run a shorter stem as a result, and I suppose that a 100mm stem is not really short, but I think that I could have easily gotten away with the shorter overall length. I think the next couple of bikes I do will be a bit more stock geometry, so that will help me get my design mojo going a bit: being able to tweak a known quantity is probably a better way to learn than winging it repeatedly.
Dimensions for Daruma Cross:
HTA: 72 deg, should have gone to 72.5 with the fork that I'm currently using. Will look to change that once I can afford a new one.
STA: 73 deg, but who knows with the curvy seat tube that I ended up using. Seems more like a 74 or 75 up towards the top. Fits perfectly though.
BB Drop: 70mm
ST: Virtual 590mm
HT: 180mm
TT: 605mm
CS: 425mm
Each one of the bikes that I've made for myself could be better in some ways though. I guess it really boils down to needing to get better at bike frame design. When building bikes for myself, I tend to follow my standard recipe technique: look for all of the things that I think are cool, try to slap them all together, and then throw a bit of experimentation in for good measure. Ask anyone that's tried my cooking.
In both of these bikes, I made some really long top-tubes to help accomodate for my preferred mid-foot cleat position. In the case of my road bike, I was pretty much spot-on with the length, but a slight miscalculation in which forks were available to me, left me with a steeper-than-desired headtube. It gets a little quick steering, though still within reason, until you're going at speed. My other miscalculation has more to do with a lack of understanding of the inherent flexibility of bamboo. I got all artsy with the seat stays and picked some nicely re-curving sections, but at the end of the day, I really probably should have gone with some stouter bits to boost the rear-end stiffness a bit.
As far as my quibbles with the D-Cross, it seems that I could have made the top tube about a centimeter shorter, and probably could have done something similar to the chainstays. My design goal was really to make something that would absolutely not have any toe overlap, and given my big hooves and mid-foot cleats, this required some extra length in the front end. I was prepared to run a shorter stem as a result, and I suppose that a 100mm stem is not really short, but I think that I could have easily gotten away with the shorter overall length. I think the next couple of bikes I do will be a bit more stock geometry, so that will help me get my design mojo going a bit: being able to tweak a known quantity is probably a better way to learn than winging it repeatedly.
Dimensions for Daruma Cross:
HTA: 72 deg, should have gone to 72.5 with the fork that I'm currently using. Will look to change that once I can afford a new one.
STA: 73 deg, but who knows with the curvy seat tube that I ended up using. Seems more like a 74 or 75 up towards the top. Fits perfectly though.
BB Drop: 70mm
ST: Virtual 590mm
HT: 180mm
TT: 605mm
CS: 425mm
Friday, November 19, 2010
This just in...
Bigfoot was spotted riding his cyclocross bicycle at Belmont Plateau in Philadelphia yesterday evening at approximately 7:30 last night. No clear footage was available, but we got this grainy photograph to prove that he was there. Enjoying himself immensely.
Daruma Cross emerges from the shadows
Ok, Ridiculous to take photos of one's bike at night. But I couldn't resist.
Tuesday, November 16, 2010
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