Reply To: Huben Hammerless K1
I have been unable to access the photos from River Devil’s post but I can imagine the structure of the Huben valve working from the Patent Drawings and also because in my home workshop I have a prototype airgun that works in exactly the same way, except that I do not need the constant pressure valve so I do not infringe the Huben Patent.
The forces on the firing valve are much more complicated than River Devil’s formula would suggest and I would not expect the power dissipated in the movement of the valve to be anything like as high as he suggests.
Remember that the Huben valve is a double ended spool valve, a smaller end of which closes the port leading to the magazine and a larger end of which is slideable in the valve housing. The smaller end would not need to be any larger than the bore of the barrel so we can guess that that is about 5.5mm. Therefore it is the other end that is about 8mm. Thus in the static state the gas pressures on the two ends will partially balance one another and the resultant force need only be sufficient to overcome the force of the return spring and the friction on the valve. When the valve is released the force will stay the same during the initial opening movement until the port is fully opened and the balancing effect of the front end of the valve is lost. But then the pressure will be dropping in front of the valve and the force on the valve will depend on how fast the pressure drops and how fast the valve moves. The mass of the valve is relevant here but we don’t know what that is.