kind'a stupid questions for framebuilders..
I want to re learn this art.. i say re learn because i havent done anything like in 22 years... and in my country my master didnt allowme to do some stuff because i was too young and because of lack of time too... welll i did a frame and my step brother still has it... well my questions are very stupid ok?...
1 - how u guys fix the pins? i saw some people use pins to fix averyting in place... u guys drill a hole and then fix the pin into the hole? or are super special pins that can be set up with a little hammer?..
2 - I have seen straight blades forks since long time ago and i think they look quite cool in some bikes... my questin is this one, how u guys set up the rake on them? i mean... all the for crowns can be used with straight blades? the crown must be modified? the fork blades are cut in angle to fit with the desired rake?????
Im asking about the fork blades because looks like it is easier to do... welll if the fork crown must be machined or something thats out of my league hehehe
Hope somebody could answer me those questins... thanks in advance...
Well, I am not a frame builder but no one has answered yet so I will add my bit. As I understand this stuff a line drawn from where the fork joins the headtube and thru the wheel axle should hit the ground a couple of inches or so ahead of where the tire touches the ground. Something about the caster effect. Helps the bike to steer more easily. How the fork gets from the headset to the dropout isn't absolutely critical. Straight, simple curve, wavey, zig zagged, whatever. An experimenter once built a bike with the line touching the ground behind the wheel. Fiendishly unstable. Just measure a few good bikes to get your angle. Someone check me but I understand touring bikes have more of this "trail" and twitchy( ) criterium bike have less.
Originally Posted by ultraman6970
the shorter the trail, the more "twitchy" or "responsive" the bike will feel, the longer the trail the more "relaxed" or "sluggish" the responsiveness will be.
building straight blade forks, there are two methods that i know of. one is building the fork without lugs(unicrown, welded, etc) the other is getting a crown lug that has built in rake. henry james have i believe 3 degrees of rake built into his fork crowns, not enough for straight blade(maybe a track frame). other crowns have about 7 degrees of rake. when building the fork you have a little bit of play to adjust for the desired rake.
when it comes to using tacks in the frame. you should drill tiny holes first and use tacks that will fit in the holes snug to keep the joint from creeping. the tacks usually become brazed along with the joint, so the head should be filed down till its flush with the frame and is not noticable anymore, also, you dont want it to be too far into the frame because this part of the tack remains in the frame. i mostly do welding, so i am not an expert on the best nails, but i know that you want to use steel tacks.
I'd bend the top of the fork, and then grind the joint in at an angle. I have a belt sander set up with various small wheels that corespond to tubbing fits. I haven't tried it, because I don't really like straight forks (3 out of 4 of my current bikes have them so... what can I say. I would lay the bent blade on my bench and lay out the drops, install them or use a slot in the overlength tube to register the height and square of the leg in a temporary jig so that my grinder would do the rest. I have to hand grind, but as long as the fork angles are there, I can hand feed without much difficulty, just approach the final cut with a a few test fits.
I would probably use roughly the same process without the grinder, just position the blade, next to the head, and splile/transfer in the cut. Then grind and file it till it fit well enough to weld.
Thank u very much
You need a special crown for use with straight blades. Joe Bringeli sell them for cheap so give him a call.