Saw this Harley on the back of a 5er yesterday
Does this belong to a member? Looks good. Looks HEAVY.
Forum Discussion
Just for the sake of discussion, what is being missed in the back and forth regarding reduction in pin weight is the fact that there are springs between the load and the ground. These springs have a "spring rate" in which they compress a distance per specified amount of load (leaf or torsion, the effect is the same). The spring rate is also usually variable, usually increasing as the spring is compressed (i.e. engaging more leafs).
Given the example where the pin is twice the distance to the lift, using statics shows the pin will decrease 1/2 the load on the lift. In addition, statics shows the load bearing on the fulcrum (axles) increases by the summation of the new load on the lift and the load removed from the pin. So for 600 lbs on the lift, the load on the fulcrum (axles) would increase by 900 lbs. However, all this is true ONLY if the fulcrum is fixed (i.e. supported by stands at the frame)
But of course, in fact, the axles are NOT fixed in relation to the load, and thus this is not a simple statics problem. When you place a bike on the lift, a good deal of that force goes into compressing the springs rather than lifting the pin. The instant you apply the load, the spring can't resist and begins to compress. As the springs begin responding to the new load, they begin increasing the resistive force and acting somewhat as a fulcrum and removing some pin weight, which then travels back and goes into compressing them further before they resist more. The overall effect is much of the weight on the lift will go into compressing the springs, and how much is removed from the pin due to the partial fulcrum effect is actually COMPLETELY DEPENDENT on the spring rate (which is usually itself variable). So it is entirely possible for fj12ryder to see only 40lbs removed from his pin and someone else to see more on a different trailer. To mathematically solve for the weight removed from the pin would either require the spring rate, or the distance the spring was compressed.
Given the example where the pin is twice the distance to the lift, using statics shows the pin will decrease 1/2 the load on the lift. In addition, statics shows the load bearing on the fulcrum (axles) increases by the summation of the new load on the lift and the load removed from the pin. So for 600 lbs on the lift, the load on the fulcrum (axles) would increase by 900 lbs. However, all this is true ONLY if the fulcrum is fixed (i.e. supported by stands at the frame)
But of course, in fact, the axles are NOT fixed in relation to the load, and thus this is not a simple statics problem. When you place a bike on the lift, a good deal of that force goes into compressing the springs rather than lifting the pin. The instant you apply the load, the spring can't resist and begins to compress. As the springs begin responding to the new load, they begin increasing the resistive force and acting somewhat as a fulcrum and removing some pin weight, which then travels back and goes into compressing them further before they resist more. The overall effect is much of the weight on the lift will go into compressing the springs, and how much is removed from the pin due to the partial fulcrum effect is actually COMPLETELY DEPENDENT on the spring rate (which is usually itself variable). So it is entirely possible for fj12ryder to see only 40lbs removed from his pin and someone else to see more on a different trailer. To mathematically solve for the weight removed from the pin would either require the spring rate, or the distance the spring was compressed.
