displacement of hydraulic gear motor?
displacement of hydraulic gear motor?
(OP)
Hopefully I can explain this...
I have a hydraulic gear motor, which has two spur type gears that mesh with each other inside the housing. The dimensions are:
O.D of each gear=.858" dia.
thickness of gear=.625"
# of teeth= 11 teeth per gear
distance between centers is .750"
flow= 7 gallons per minute..
The formula for finding RPM is= N=231(GPM)/displacement
How do I figure out the displacement? I am totally stumped here...this is a motor that I have made, so I can't go to a manufacture for this..
thanks,
Brent
I have a hydraulic gear motor, which has two spur type gears that mesh with each other inside the housing. The dimensions are:
O.D of each gear=.858" dia.
thickness of gear=.625"
# of teeth= 11 teeth per gear
distance between centers is .750"
flow= 7 gallons per minute..
The formula for finding RPM is= N=231(GPM)/displacement
How do I figure out the displacement? I am totally stumped here...this is a motor that I have made, so I can't go to a manufacture for this..
thanks,
Brent





RE: displacement of hydraulic gear motor?
I think it will be difficult to determine the displacement without knowing the speed (or the speed without knowing the displacemnt)
That will give you gal/rev, and a simple conversion to in^3 per revolution (or any other volume unit)
Doing the math would require much more exact gear information. There are quite a few different gear profiles.
RE: displacement of hydraulic gear motor?
there are two flow paths of dimension .625" x .108", and the length of a circle at the pitch line is 2.3562", so the displacement per revolution would be:
.625 x .108 x 2.3562 x 2 = 0.318087 in^3,
if the teeth were of zero thickness. Assuming as a w.a.g. that the teeth occupy half the swept volume, the displacement per rev is then
0.318087 / 2 = 0.1590435 in^3.
There are 231 in^3 in a gallon, so this motor would displace
231 in^3/gal / 0.1590435 in^3/rev = 1452 -ish rev/gal
revolutions to displace a gallon. Pushed with a flow of 7 gallons/ minute, the motor would then spin
7 gal/min * 1452 rev/gal = 10167 rev/min
... again, ROUGHLY, and that's assuming I haven't left something out completely, which does happen.
Since that's about five to ten times the speed at which gear pumps are normally happy, I'd expect durability problems.
For a more accurate answer about the displacement per revolution, slowly pump a known volume of grease through it and count the rotations.
Mike Halloran
Pembroke Pines, FL, USA
RE: displacement of hydraulic gear motor?
RE: displacement of hydraulic gear motor?
where W=Width of gear, D=diameter of diameter of gear housing and L=Length of gear housing (for the two gears, roughly 2xgear diameter minus tooth height)
Hope this helps
KRB
RE: displacement of hydraulic gear motor?
As soon as I get a free second, I'll calculate and see if the #'s are reasonably accurate..
I very much appreciate the advice..
thanks,
Brent