Hi all, don't know if this is correct area for this but I'm having a hard time locating a replacement spring for the pump body. I disassembled my pump and found the spring broken in 2 pieces. any ideas?
phone ahead, Motion Industries doesn't always carry the complete line of products from a company, or may impose a quantity restriction (for example, I wanted a specific type of grease nipple, they carried it, but I couldn't just order 2, I had to order at least 25 (and they were about $2/each)... It turned out to be cheaper and better to just buy new u-joints.
I checked bijur website for replacement parts and they dont have springs listed. just fittings, gaskets resivoirs and the like. same with H&W machine and icai-online. Bijur site recommends sending in pump to them for all internal isssues. I'll give motoin a call today but im sure thats a dead end. Thought someone may have a secret source.
As chips&more stated, making one is my best option. Easy enough to measure OAL, diameter, wire gauge and pitch. I would like to know the compression force in lbs/in so I get the correct pressure without having to lean to hard on lever, or wait forever for plunger to travel its stroke.
I have a Bijur pump on a 1997 Bridgeport mill. The type with the spring loaded T handle that you pull up. I accidentally lost the reservoir cap a couple of years ago, possibly vacuumed up. Called Bijur directly. They only sold these in boxes of multiples, probably to distributors. Lady was very nice and shipped me one for free. Might be worth a call.
Here's where I'm up to. The spring is 3 " long with an OD of 0.56" and a wire size of .072. I can only find Dia of .5 or .6 in various compression strengths. I'm choosing to go with .5 od as the .6 has the potential to rub up against the piston bore (.75") when deflected under compression as the piston rod may not engage the inner diameter of the spring keeping it away from the bore. This would score the bore and is obviously bad.
Now how I am choosing the compression strength. When assembled and at rest, the spring is compressed 1 inch. Engaging the plunger stroke compresses it an additional .8 inches for a total compression of 1.8 in. Bijur specs the pump max pressure at 5 Bar or 72 PSI. So calculating the surface area of the piston to .44 sq in I would need a force of 32 lbs at max compression of 1.8 inches to achieve 5 Bar. this gives me a spring force of 17.7 lbs / in.
Your math is correct, but I'm not sure of your physics. Any knowledge I had of Hooke's law is gone but the name. If the physics works, then do you really need max pressure? Or is max pressure the design limit, and the spring should be spec'd at a lower pressure. 72 psi will move a lot of lube through a very small orifice.
I believe max pressure is the design limit and is peak Static PSI on a full length stroke. The kinetic PSI will be slightly less depending on orifice resistance and it will have a linear drop throughout the entire travel of the piston stroke and should finish around 36-38 PSI right before the piston bottoms out in the bore. For this reason I don't think its a good idea to go with a lesser spring.
Considering the volume of lube per stroke is finite, the pressure only regulates the speed at which the lube is distributed. A 2 psi spring will push the oil through since there is no seal to stop the oil from seeping past the ways contact surfaces but may take 10 minutes to complete the stroke.