Design and Development of a Fork Bridge
Background
I bought a used, rebuilt Aprilia RSV Mille R 2002 years model. It is converted into a street fighter motorcycle.
However, turned out, after I started to check out the bike, I found lots of errors, cut wires, short circuits, erosion of the contacts, the wrong measure of the parts replaced, aso.
My goal is to make every wrong right. I have started with the electrical system, built back to the original wireing and replace of all parts that are damaged.
But in this post I will present the new steering crown (upper fork bridge). I design and mill out with laser cuter and CNC-miller. This is due to the replaced sitting on the bike at the moment, you can not get fully steering, the fork bridge scrapes in to the tank. One can not lift up the tank and can not use the steering lock. Many errors at one point!
Existing vs Original Fork Bridge
As you can see there are no alternative to adjust the handles on the fork bridge. The old owner used a hammer to fit the fork bridge on the motor bike, due to the fact that it did not fit well at all, and to losen it was a mess…
Compare it to the original you can see that the outer lines are totally different, With the original all the mechanics freedom of degree works. So the one that I will design will look more like the original in the lower outer line that the existing one.
Existing
Orignal
Construction of a new fork Bridge
Im a developer an Engineer, Master of Science in System Control and Mechatronics, Chalmers.
I use Autodesk Fusion almost every day. Im starting to learn the program quite well. So to design a fork bridge, which according to me is a simple geometry is just a few hours work.
The steps in this project.
- Measure the physical dimensions
- Make a simple CAD for the three holes
- Laser cut a plastic version of the simple cad
- Verify the laser cut part, se if it fits
- Adjust, the simple model
- State what I want on the new fork bridge
- Create the complete CAD that is going to be milled out.
- Sen the CAD to a company that can deliver my design
1. Measure the physical dimensions
I was naive or really bad on geting information on the internet. But the fact remains, I did not manage to find any drawing or dimensions of the original fork bridge (FB). This ended up using the old-ways, measure every thing by hand. But what I needed was just the placement of the three cylinders, (Left suspension, Right Suspension, Center attachment). With this I can make a simple design and verify it with ease.
Now, due to the fact that I didn’t find any drawing I will post my here and feel free to use it however you want!
One of the things that I notice was that the holes for the shock-suspensions was not in center of the suspension, it was tangent to the inner side of the suspention [Image below]. So in this model I moved it down 1.3mm, and lets se if it will fit better.
2.Make a simple CAD for the three holes, and first test outline
Presentation of the ”simple design”, the part that Im going to laser cut out in plastic.
Feel free to download the drawing!
3. Laser cut a plastic version of the simple cad
So today att work I Laser Cut the ”simple model”. Im using 5mm Akryl plastic. Ohhh how I love to se the laser smoothly cut through the plastic.
4. Verify the laser Cutted part, se if it fits
So, the fork and the center part fits like a charm. But the key-egnition part was to far away to use the steering lock, so it has to be adjusted. Ca 3mm closer to the center. I will cut out another part in plastic before I am satisfied with the measurements.
One can now lift upp the tank without any problems.
Finaly I can use the full steering !! The existing fork bridge got in contact with the tank, and therefore, damage the tank, and I could not get full steering.
