is a wheel fastened so that it is free to move up and down the wheel rolls on the moving belt rising and falling whenever it strikes the bow the platform fasten solidly to the wheel carries a tracing panel and when the wheel moves up bend though the tracing pen draws a line which shows the movement of the platform to get a true picture of the up and down movement tracing paper moves at the same speed as the moving ground the bell will start the model running now but priceline gives us an exact picture of the up and down movements of the wheel and platform let's see what happens when we use more speed at high speeds the effect of a bump is considerably greater influence in photography we can see that the wheel primes the bump and bounces into the air of course this jolting is passed on to the platform we can mount a fairly stiff spring underneath the platform to see how it will affect the joining now let's watch it in slow motion photography shows that we have cut down the jolting because the spring absorb some of the effect of the bow let substitute a stronger spring for the stiff spring that we have been using a softer spring gives a smoother line will bounce harder and faster we can see that this on the equal springy step springs in front and soft springs in rear causes pitching when the wheels strike  the trace grind shows this clearly the only way to eliminate this on equal spring and make the front springs solved if to give them only one job to perform the job of absorbing problems suppose we replace the bouncing axle with a rigid immovable beam now the wheels can be fastened to the beam by two parallel swinging arms the wheel is pivot so that even when the arms are tilted by a joint or blow the wheel remains vertical and in perfect alignment and so no in place of a stiff spring we can use a soft spiral spring to absorb the joints and level out the ball since the rigid b and the swinging arms get the front wheels in line there is only one job left for our springs to do with both front and rear springs equally strong the platform is held in balance but not at the front and rear springs are strong we have another problem springs that are soft enough to level up the ball will compress too rapidly under a heavy shot and springs that are soft enough to absorb smaller shocks have a tendency to continue abounding after they have been compressed or stretched so to help the springs up storm every shot we can slow down their action by means of shock absorb the shock absorber acts like a break in delaying the movement of the spring and it prevents bone thing when the spring is compressed and then released we can make the severest kind of test to see whether we have a method that will really iron out the ups and downs we use a lot more bombs of different size and we'll run them under our wheels the full speed now watch the race blind but brake line seems to be pretty smooth let's watch through the slow motion camera and see just what's happening no more pitching than the small spring where the shock absorbers spread out the effect of any bumps that they can completely absorbed of course in actual practice where strength and safety maximum important engineers up made use of the same bump but so are being roped leveling principles with a much stronger and more durable construction the parallel swinging are the swinging arms and the rigid crossbeam do all the work of keeping the wheels in perfect alignment so the genuine soft knee action spring has only one job to do double action shock absorber control or the compressing and stretching of the spring as a that sort of heavy jolt this combination of soft questioning spring together with positive double action control on the front wheel smoothly over the way while the wheels do all of them once the trace line and the pain in the next has been taken out of ordinary drive giving a truly level ride