billbedford wrote:Lord Colnago wrote:The popular method of springing any buffer usually involves placing a small spring over the buffer shank, inserting the buffer into the housing and then securing the buffer at the end of the shank in such a way as to leave the head the correct distance from the housing. I do use this method, but I cut the springs in half and stretch them out to their original length, as I find that the spring is too strong otherwise.
Cutting springs in half with double the spring rate, i.e. it will take twice as much force to compress the spring the same distance. This can be experienced by bending a long and short piece of wire. The longer one will alway be easier to be, presuming they are of the same diameter. What I suggest is happening is that the counter bore in the buffer guide is not long enough and the longer spring is partly compressed while the buffer is at the extended position.
I design printed buffers to have a deep bore for the spring, to soften the stroke. Frequently, the bore for the spring goes right through the buffer guide into the spigot behind the headstock.
This buffer, which worked OK when assembled, was bored 4.25mm deep and I've adopted that as a standard.
I think one needs the springs to be slightly compressed when the buffers are fully extended. If there is no compression, then slight friction in the bore may stop the rams extending fully.
EDIT: urk, too early in the morning for coherence. What I should have said was that this buffer is 12" from headstock to front of guide and 18" from headstock to buffing face. That gives a distance from buffing face to the back/bottom of the spring bore of 6.25mm and that is my standard dimension. It happens to give a bored depth of 4.25mm on this one because the guide is 4mm long.