I'm now up to the stage where i thought i better make a start on the front end. I'm going with the leading link design which appears to be a fairly common design amongst trike builders. There are slight variations on the type of leading link designs out there but they all amount to the same principles. When doing research on leading links front ends over the net i didn't really find one specific site that shows or answers all the questions i wanted to know when first looking into it, therefore i hope to cover what i can about this front end, if there is more detailed pictures or something you are wanting then let me know.
|The following info is what i have read about or concluded after several hours of thinking and therefore i do not claim that it is %100 correct because i am yet to test my front end on the road to say if i got it right or not. If there is any info i provide here that is clearly incorrect then feel free to email me and let me know.|
The basic principle :
Picture is from http://www.carbibles.com/suspension_bible_bikes.html
The steering of a trike has a few geometry angles which are shown in the above picture.
The Rake : is the angle (measured in degrees) of the steering neck from a vertical line. The larger the rake angle the further forward the front wheel will sit which gives it the "chopper" look
Offset : is the distance between the centre line drawn through the steering neck to a line drawn through the centre of the fork tubes.
Trail : If you were to draw a vertical line through the front axle to ground and a line through the centre of the steering neck to ground then the distance between the two lines is the trail. ( as pictured above). Please note that there are some sites out there that have miss leading diagrams and the diagrams show the trail as being the centre line through the fork to ground which is not the case, it is the centre line through the steering axis IE: steering neck to ground.
The main angles you have to worry about when designing or building a front end is the trail. You can make the rake angle what ever angle cranks your handle ( although i commonly read that up to 45 degrees is ok and after that is less desirable) but its the trail that will determine how the bike steers and handles. Rake angle does have a effect on handling cause the more rake provides greater straight line stability, less rake makes the bike more responsive but.... with too little or negative trail (steering axle mark behind the front axle mark), the bike will handle with unbelievable ease at low speeds, but will be completely out of balance at high speed. It will easily develop a fatal high-speed wobble. NOT A GOOD THING.
Normal trail is somewhere between 2 and 4 inches. The bike will handle easily at both high and low speeds. Flowing smoothly through curves without swaying or wobbling but too much trail and the bike will handle sluggishly at high speeds. It will seem almost too steady. You will have trouble balancing the bike at lower speeds or on winding roads. It will feel generally sluggish and clumsy. so the idea is to make it right the first time and understand the rake and trail concept.
If you, for example, plan on using the front end off a standard road bike on your trike then you will want to make sure that the frame of the trike has the same raked steering neck as the original donar bike otherwise your likely to end up with a trail measurement that is a mile out which is why most people that increase the rake angle end up making a leading link front end because as you'll see later re adjusting the trail measurment on a leading link design is as simple as redrilling the axle holes in the front rockers and shifting the wheel backwards or forwards to suit.
There are plenty of web sites out there that explain the principles of rake and trail so i won't go into any more detail on that side of it and will start putting up picturs of my progres in designing and building my leading link front end. I just wanted to mention the above info so that your aware of the rake and trail concept ( IE: you can't just bolt on a GSX1100 front end to a 45 degree raked frame and expect it to steer )