bottpower

Lately I am spending some spare time designing a tool that will allow me to measure chassis and swingarm stiffness. My intention is to design something relatively simple and cheap, but that will allow me to obtain precise data. The images that you can see below are just sketches, the final design will be probably quite different.
First image shows an arrangement to measure the chassis stiffness regarding torsion. The chassis is clamped in the swingarm pivot area, and a torque is applied around the steering head. The torque value is adjusted in a precise way adding steel discs (blue color in the drawing). A digital inclinometer will be placed over the lever arm to measure the torsion angle.
In order to measure the chassis stiffness with the engine assembled on it, it is possible to locate the green clamping parts in the external faces of the chassis.

Second image shows an arrangement to measure the lateral stiffness of the chassis (flexion). In this case we just pull from the steering head, hanging a weight that is converted in lateral force through a pulley. Here it would be necessary to put an object under the chassis to avoid it to fall over the table (rotating over the swingarm pivot).

Third image shows an arrangement to measure the swingarm torsional stiffness. The arrangement to measure lateral stiffness would be similar to the one used for the chassis, using the same pulley.
I also want to use this tool to measure transversal torsional stiffness of the chassis, I mean, the stiffness that it has when we apply a load similar to the one that appears when we use the front brake.

I think that it is impossible to build a tool that could give you absolut stiffness values, the objective is to build a device to achieve values that will allow me to compare different chassis.

I want to use this table also to meassure chassis (general dimmensions, geometry, etc) and also to build chassis, using it as a base for my jigs.

Regarding stiffness meassurement, appart of general meassurement, I want to use extensometry to meassure local deformations on the chassis, in this way it will be possible to know the influence of each area of the chassis in the stiffness of the whole chassis. This could be very useful to validate and improve FEA models, trying to make these models more similar to reality.
I will keep you informed of this project progress in the blog.

Tags: bottpower, other projects, chassis, swingarm, stiffness, tool, extensometry, FEA

Some days ago, reviewing the last posts of The kneeslider, I arrived to 95Racer’s blog, and I found a project with a very interesting approach, and moreover, very well carried out by 3Up-Racing, a group of people who have been involved in club racing in the UK for many years.

Lately a lot of people is talking about the new course of current 250 GP category. The only thing we know for sure is that the new category will use 4 strokes engines. 3Up-racing planned to design and build a 4 strokes motorbike, with a performance level similar to a 250 cc. 2 strokes GP motorbike. They chose “95Racer” as a name for the bike because they wanted to build a bike with a dry weight of 95 kg. and 95 HP at rear wheel.

After analizing several possibilities, they chose a Kawasaki ER-6 650 cc. paralel twin. They designed and build a steel trellis frame. The design of the swingarm is very interesting, they made an aluminum tubular structure, and after that they covered it with aluminum sheetmetal. The front suspension comes from a Yamaha R6, and the bodywork from a Honda RS-250RW Speedfiber kit.

As you can see in the photo, they also built their own carbon fiber airbox, with a single central intake that goes through the headstock.

In their blog you will find very interesting stuff, for example they removed the start engine, it allowed them to reduce the battery size and weight. They created an external starter that acts directly on the engine’s crank. With these modifications, they saved arround 10 kilos..
You can see it in the following video and, by the way, enjoy the sound…

Photos and vídeo: copyright 3Up-Racing.

Tags: 95Racer, prototype, 3up-racing, ER-6