Suomeksi Image Map



MAKEUP

I did also some painting.


I painted the seat matt black and running boards, front suspension swinging arms
and "rear rack" with aluminium email paint.


I painted the skis gloss black to get more metallic look
and the loops I painted orange.


I also put some paint to handlebars.



REAR SUSPENSION SYSTEM

My happines didn't last too long. There was still two major problems: The slipping drive wheel and rodeo-horse-type rear suspension. The rear suspension was really bumpy and in the matter fact, it was useless. Only the rear of the track moved and it didn't handle the bumps in the terrain. Even a small bunch of snow stopped the sled because the front of the track suspension couldn't move. To pass the snowball the whole sled had to "climb" over the snowball. This was too much for the drive wheel and it couldn't move the track. It just started to slip.


This picture tries to explain, how the original suspension worked.
The front of the track suspension only turns, it doesn't "sink". Track system is mounted to the driveshaft.

At the end of the march it was time to lift the sled to the table and start to build a better rear suspension. My goal was a similar track assembly than in real sleds.


Old track suspension system


Here you can see the idea of the old suspension. There was one torsion spring.



There were tall "paddles" inside the track. I thought first these were for the drive wheel.


Drive wheel. When I saw this I understood meaning of the "paddles". These were for keeping the track in the line.
The tiny dots in the side of the track were for drive wheel.

There was three things I had to notice:

- The paddles inside the track
- The rubber of the track was totally non-slipping. This prevented me doing a real sliding track. I had to use wheels.
- What kind of dampers and springs I could get.

The only thing I had something to say about were the dampers, but it was not so easy to find dampers by measure. When I went to a shop to buy dampers, the first question was: "What car do you have?" "No kind of car". I had to buy dampers randomly until I noticed there were dampers by measure in the RC-Mart. Then it was easy to order what I wanted.




Part of my damper collection

I had also no idea what kind of tension there should be. That's why I have great collection of different kind of springs.

I had to find out what kind of track suspension systems there were in real sleds. I had great inspiration from Seppo's Art Attack-snowmobile -pages.


My first idea was to build M-10 -type suspension because there were coil springs. The more I learned about track suspension and suspension geometry, the better I understood why torsion springs are so common in real sleds. It takes a lot of effort to make progressive system with coil spring dampers.


Fast M-10 track system


First tests.



JJS-TRACK SYSTEM EVO1

My self confidence as a sled engineer raised, when after a long engineering period I noticed that I ended up a same kind of system than Finnish BRP sled manufacturer Lynx with their PPS-Suspension. I really have to say first I engineered mine and then I saw PPS (Pauli Piippola Suspension) in sledfair in Helsinki faircenter. (Pauli Piippola is a Finnish sled cross legend)

I wanted rear and front arms of rear suspension to work as independent as possible, and I succeeded in this.



First working version. It's made of 0,8 mm and 2 mm aluminium plates, carbon fibre and aluminium tubes
and M2, M3 and M4 thread bars.


Because I didn't find hard springs enough, I decided to use two short dampers from a touring car.



I had to mount dampers this way, because otherwise they would touch the track wheel.



I had to use small airplane wheels. The "tunnel" in the middle is for
the inner "paddles".


There was a some kind of limiter strap in the front arm.

The most delaying problem was the winter in southern Finland - or actually lack of the winter. The important test drives were impossible to do without snow. Winter 2007-2008, when I made most of this project was the lousiest winter of my life. I was only able to test the sled when I went to visit my parents-in-law at Keuruu, 300 km north from here.


This picture will tell everything about the winter 2007-2009 in Helsinki, Finland.