Designing a Piston Pump

Mrezazaeemi,

The cam profile will derive from your stroke, but foregoing a crankshaft in favor of a cam for the application you describe makes no sense to me. Using a cam you will need to provide a restorative force to keep the piston's cam follower against the cam during the volumetric expansion stroke.

Will this be water pressure, a spring, or weight? There are inefficiencies with all of them compared to using a crankshaft.

Please provide more information, and why you feel a cam is better for your application.

Regards, Greg

That's right.

Why cam?

If cam, you need to have a spring to assist suction stroke. The work needed to compress this spring will add to the work needed for discharge stroke. In crank arrangement these works are distributed.

Besides, 2.6 GPM is fairly a high rate of flow for cam actuated plunger pump.

If oil, high speed, multi plunger pump could be an option.

Since water is the pumpage, to me it looks like 'double acting piston pump with crank arrangement' is more a compulsion than an option…

http://www.lcresources.com/resources/getstart/2b01.htm

hi

thank you so much for your help. if you see the link at the above. i want to go for a just one piston (simple plunger)and single acting because in double acting we should have four valve so i reduce the volumetric efficeincy. to be honest with you i want to go for a cam instead of crankshaft because it s more simple in calculation and i dont know what s the proper formula for dimater and lenght of crankshaft.and also please tell what s piston speed(piston pin)?is this true Average piston velocity v = 2 * stroke * rpm ? do nt you think that it should be v=the lenght of piston rod*2*rpm and what should be the diameter of my cam

Are you just transfering fluid or, are you trying to supply a "constant" pressure or flow to a process?

With simple transfer, are pressure fluctions a problem?

If supplying a process, is pressure a requirement or volume or both.

Not certain why you want to use a cam, with all the setup and bother of designing it.

If you don't want to run off the crankshaft (would that be a gear drive?) or you are using an electric motor, why not just use a disc, or an arm run directly off the motor with a pin at the large diameter side/end connected to the pump's piston?

Mark

hi

you suggest me a good design because i do want to go for crankshaft .so you tell me that instead of connecting directly cam to the piston rod i use a dish with a pin for converting the rotating movement so in your scheme there s no need for shaft for putting disk or how do u couple disk to electric motor? with shaft or directly?

what should be the diameter of the disk and the lenght of piston rod?

i prefer just to use one piston.in this scheme what should be the diameter of the cam and the lenght of piston rod and what kind of spring i should use with what constant how much is the valuse of the load on the spring?

Animation of a Pump Working

do u have better suggestion instead of crankshaft and cam except solonoid? which one is better and more simple design but with high effecinecy? probably u should say crank shaft... !!!!!!! if you say cam is not good please give me the propwer formula for crankshaft

Mrezazaeemi,

Google "slider crank", or "slider crank mechanism" and you will be presented with ample information on how to design the crankshaft and connecting rod portion of your pump.

A crank is a much preferred method of design over a cam. they have been made this way in one form or another for hundreds of years!

Don't do things the hard way.

Regards, Greg

The spring is only necessary as an aid to overcome the inertial forces when the piston changes direction, thus reducing the force applied against the pin on the slider mechanism. Its size is not important, unless there is a friction problem in the fit of the piston to its chamber size, creating additional forces against the piston movement. With good sizing, a spring is not necessary at all, since the slider does all the work.

The diameter of the slider's rotation will give you the length of stroke of the piston. But in designing the pump this is not as relevant to the piston's overall length as the distance between the inport and outport connections of the pump manifold.

The throughput of your pump will depend upon the inside diameter of the manifold and the number of strokes per second/minute of the piston, less the upstream (datum/head/viscosity) and downstream (system) resistance forces in your total system design.

Mark

Oops! Small correction here.

"The throughput of your pump will depend upon the inside diameter of the manifold"

should have been:

The througput of your pump will depend upon the inside volume of the manifold between the pump's inport and outport...

Sorry for any confusion I might have caused.

Mark

Your statement in#10 is more correct than #12

Try modifying as , "The throughput of your pump will depend upon the inside diameter of the manifold/piston, stroke length and the number of strokes per second/minute of the piston ..."

It is 'swept volume that matters' not the total chamber volume which, includes dead pockets (clearance volume). This clearance volume is functional only when fluid is compressible.

mrezazaeemi, are trying to invent the black string???

Try as I might, I was unable to make the connection between ol' mrezazaemi's simple pump question and black strings. I sure would like to know how they are connected in your mind, though; since the stuff I'm learning about black holes and black strings, etc. is amazing. Now as Wikipedia defines it,

A black string is a higher dimensional (D>4) generalization of a black hole in which the event horizon is topologically equivalent to S² × S¹ and spacetime is asymptotically M^d−1 × S¹.

Perturbations of black string solutions were found to be unstable for L (the length around S¹) greater than some theshold L′. The full non-linear evolution of a black string beyond this theshold might result in a black string breaking up into separate black holes which would coalesce into a single black hole. This scenario seems unlikely because it was realized a black string could not pinch off in finite time, shrinking S² to a point and then evolving to some Kaluza-Klein black hole. When perturbed, the black string would settle into a stable, static non-uniform black string state.

So you can see how fascinating any possible connection between the two ideas becomes.

Mark

"please tell me the proper formula for my question or give me useful web site relevant to my question?"

What is it you want? A solution to a schoolwork assignment or a PISTON WATER PUMP? A catalog of water pumps to fit yous specifications is readily availabe on the web. Selection of the appropriate pump is merely scanning the tables and picking out the best unit.