Hydraulic pump and motor sizing for a DIY 36-inch stone saw

[Whitewolf4869]

Im planning to build a stone saw with a 36 inch blade and plan to use a hydraulic pump and motor to power the saw blade The hydraulic pump will be driven by a 50 hp diesel motor Now the hard part i need to figure out flow rates pump and motor sizes and basic saw design
i have been looking on the internet for years and hevent found much until i stumbled on this forum there seems to be a lot of down to Earth people here with good info and just a few that say why do you want to do this? and you can't do that lol . I have built a 12 kw generator from parts i had collected and wasted a lot of money and time trying to go direct drive before i figured out that belt drive was absolutely the best way to go
So is there anyone out there whit any suggestions?

 

[Baluncore]

Sorry about the delay...
Firstly; you need to know the saw blade speed, RPMs, and the diesel engine speed, RPMe.
Secondly; select a pump and motor with displacements per revolution of Vp and Vm.
Aim for RPMe / RPMs = Vm / Vp. That is the effective gear ratio of the hydraulic drive.

Now come at the problem from the other direction...
The diesel is 50HP = 37 kW. I guess the operating hydraulic pressure will be agricultural, say 2,200 psi, = 15.17 MPa.
Power = flow * pressure; Flow = power / pressure; So flow rate will be 37 kW / 15.17 MPa = 0.00244 m3 per second = 2.44 litre per second.

The motor is turning at say 1200 RPM so it will do 20 revs per second. The required pump displacement will therefor be 2.44 litre / 20 = 122 cc per rev. Now you can do the same computation for the hydraulic saw motor displacement.

Select the hoses and port diameters based on a flow rate of 2.44 litre per second * 60 sec/min = 146.4 litres per minute. Find a hydraulic “Hose size selection nomogram”. I looked one up earlier … the pressure hose will need to be 1”, the return line will be 1.5”. You might get away with 3/4” and 1” lines if you avoid continuous maximum power.

Assume 20% of your diesel HP will go to generating heat in the hydraulic oil. You must provide an oil cooler / radiator capable of dissipating that heat. You may need to arrange forced air cooling, or a large surface area reservoir tank.