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Right now I ride a Raleigh to commute back and forth to work. I’ve build a number of frames, yet I don’t ride any of them. Well the big reason is I haven’t built a frame with room for fenders. A CX bike would also remedy that. I used to ride my CX bike every where. I even rode it in a few time trials. I call it the "Do-All-To-All". It’s a CX bike, a road bike, a commuter, just swap the tires, plus it’s also got fender clearance.
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So what am I going to build? Everybody knows I’m not a guy who follows the conventional norm. I’m going to build a frame based on an old school BMX frame. . . . . Surprise! . . . . And the bike of choice . . . Champion.
I guess the question is, . . . is this design going to be a "Shouldering" nightmare.
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Some of you might be asking, what is "Shouldering". During a cyclocross race, sometime you have to put your bicycle on your shoulder to take it up obstacles.
The people in the picture above are shouldering their bicycle. Not that anybody in the KCMO area will see anything like this.
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The only course designer with the imagination to do anything like this is Jeremy Haynes and his Boss-Cross Series.
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http://www.bosscross.blogspot.com/
Saturday, October 31, 2009 Boss Cross #1
Saturday, November 21, 2009 Boss Cross #2
Sunday, November 29, 2009 Boss Cross #3
Sunday, December 06, 2009 Boss Cross #4
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I understand that the majority of CX racers come from the Road Racing discipline, where the major element that determines the race winner is brute fitness, but this is CX. You’re going to have to learn to negotiate obstacles or lose to someone who is not as fit as you. I’ve won a race simply because I could bunny-hop my bike over log, where the faster guy had to dismount . . . Sorry, but this is CX. The added element of superior bicycle handling skill can level the fitness playing field. I know I’m on a rant, but I just hate it when I hear someone at a CX counting the obstacles because he believes there are too many.
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The only course designer with the imagination to do anything like this is Jeremy Haynes and his Boss-Cross Series.
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http://www.bosscross.blogspot.com/
Saturday, October 31, 2009 Boss Cross #1
Saturday, November 21, 2009 Boss Cross #2
Sunday, November 29, 2009 Boss Cross #3
Sunday, December 06, 2009 Boss Cross #4
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I understand that the majority of CX racers come from the Road Racing discipline, where the major element that determines the race winner is brute fitness, but this is CX. You’re going to have to learn to negotiate obstacles or lose to someone who is not as fit as you. I’ve won a race simply because I could bunny-hop my bike over log, where the faster guy had to dismount . . . Sorry, but this is CX. The added element of superior bicycle handling skill can level the fitness playing field. I know I’m on a rant, but I just hate it when I hear someone at a CX counting the obstacles because he believes there are too many.
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OK . . . back to the topic . . . the frame. The first thing you will notice is the extra bar running from the seat-tube to the head-tube . . . and yes I mean head-tube, not Down-tube. Upon inspection of this cut-away picture you will see that tube passes through the down-tube and attaches to the head-tube, for an added element of complexity
. . . . What? . . . Added complexity and over complication . . . I’m in!
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It’s not done to just be different. There is a good reason it was done the way it was done, even if it’s not necessary.
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From the Champion frame review in the 1983, February edition of BMX Plus:
"Over a year and a half was spent in experimenting with different styles designed around one constantly remaining feature: the original Champion's dual front triangle. From a visual standpoint it appears as if the middle-gusset tube is connected to the down-tube and seat mast. Don't be misled. The gusset tube actually extends though and is welded to the head tube. To accomplish this, all the tubes are jigged up in a fixture. A welder then tacks the gusset tube to the seat mast. The down tube is carefully slipped rearward along the gusset tube to expose the head-tube/gusset-tube butt joint. After that joint is welded, the down tube is moved back into its position and welded. From that point the frame is 100% welded in the jig.
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The objective of the dual triangulation is to spread out the concentration of stress loads in the most efficient fashion. To do this, the gusset tube has to be connected directly to the head tube and triangled with the top tube where it ends at the seat mast. Any other arrangement would not fully be effective. Champion's dual triangle gives it perhaps the best strength to weight ratio going."
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The frame designer (Mike Konle) on the Double Triangulation:
"It’s been my experience, in aircraft and in crane booms, the way you get strength is through heavier wall thickness. You can make a frame lighter and equally as strong if it's triangulated correctly. It's the same as a boom on a big crane. They are triangulated all the way out to the tips with small diameter tubing, yet they're as strong as if they were a solid stock six-foot square. But a solid square of solid stock would bend like a garden hose under its own weight if you lifted it from one end. At the same time, your triangulated box section would barley sag under its own weight.
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When you land from a jump, imagine as the front wheel hits the ground it wants to spread the wheelbase apart. That 5/8" tube welded in there gives us a straight-pull reinforcement of the head tube area."
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Cane Booms? . . . Does my frame need to be as stiff as a crane boom? Don’t know, but the prospects have got me all giddy inside with anticipation.
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So what kind of tubing am I going to use? Straight gauge 4130? . . . Heaven forbid a double butted, bicycle specific, tube-set? I do have concerns.
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1. The gusset tube will have to be a 5/8" straight gauge 4130 tube, or a 1" double butted tube.
2. Should I use bike specific chain stays, or use round, 5/8", 4130 to create a rear triangle like the original frame? I would have to fabricate a set of custom dropouts.
I’d have to make them Vertical instead of horizontal, nothing a little 4130 plate and a file can’t handle. Also I’d have to put an S-Bend in the chain stays is order to have the tube parallel to dropout. I like the Surly combo dropouts.
That way I can go gears or single speed, but then cantilever brakes and horizontal dropouts have to go through a lot of adjustments. Eccentric Bottom Bracket? Maybe since I already have a Single speed frame I'll keep it simple amd go with a standard Bottom Bracket
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Well the thing to remember is, I’m not trying to build a Champion, I’m just experimenting with the gusset tube concept . . . and the concept was High Performance. So I believe that if Champion had a chance to use double butted tubes, they would have so I’m going to go that way.
2 comments:
I'd go with bike specific parts where you can - for the weight savings. Cool look so don't let it become a boat anchor. I'd keep that 5/8" "boom" to .035 since it's just under tension. Then again, I don't build frames...... yet. ;) Should be a cool project.
come out for the volker cross races in october, they will be at roanoke park. i think we have enough cynical and sick people on the design crew to make it a ridiculous event.
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