The Hawaiian gazette. [volume] (Honolulu [Oahu, Hawaii]) 1865-1918, 1885-06-10
Mcdonald Hydraulic Pressure Regulator.

DR.. J. Mot, Smith has kindly forwarded the fol
lOwiI g account Of the Mcdonald Hydraulic Pres
sure Regulator. The remarks were made at the
regular meeting of the Louisiana Sugar Planters
Association, April 10th. The paper was read by
Mr.. Dymond who said
Nm. PBEsIDENr:-In accordance with your re
quest, have prepared some more specific notes
concerning tue Mcdonald hydraulic pressure reg
ulatOr for cane mills, concerning which made a
few rewarks at our December meeting.
While this device has met with general favor
among our planters, believe its great merit Is yet
scarcely appreciated. Its capacity for improving
the work OF the most ordinary cane mill becomes
so obvious after careful study Of the case, that
we are led TO wonder why the device was not sooner
discovered.
A few leading points IN the expression of the
juice from sugar cane seem to be indIsputable:
l. The limit Of the Capacity of a cane mill must
pressure used, the momentum of the fywheel, the
strength of the gearing and mill housings and the
diameter of the roller shafts.
,. The usual pressure exerted by the mill is all
that should be exerted by It, proper regard being
had for such contingencies Of breHkage as axDeri-
euce seows probable from any excess of pressure.
8. Ihe ordinary steam engine depends entirely
upon the momentum of its hy-vheel for the power
20 pass the dead centres.
/. The capicity of the 1y-whee is dependent
upon the weight of the rim and its speed, and if at
the top and bottom centres it acquires Just enough
speed 10 enable It to pass the dead centres the ac-
non OF the engine would be irregular, and hence
an excess OF capacity II the ny-wheel is found
necessary 10 induce regularity of motion.
From these data may then conclude that an
engine built to exert one hundred horsepower
must exert that power when II passes the dead
centres and that when 1t passes the top and bot
tom centres It gets impulses above the one hun
dred horsepower then using, and If brought to
sudden halt on the top or bottom centre, there
would be exerted at least two hundred horsepower,
and with ordinary heavy hy-wheels three hundred
OF four hundred horsepower; and herein lies the
fertile cause of cane mill breasages. A mill built
for one hundred horsepower is called upon 10 re-
sist strain of two hundred TO four hundred horse
power, ard It naturally gives way.
The late Mr.. Longacre one of the most accom-
plished sUgar-house engineers we have ever had in
this STATE, proposed remedy for this, that our
cane mill engines should have double or triple
cylinders and cranks and no hy-wheels, and then
the capacity OF the cane mill to resist strains could
be calculated and never exceeded. This proposed
remedy would certainly have been effective, but
its considerable cost, the necessity for new out
mt, etc, prevented its application, and our plan
tiers generally followed the old method, and ruin
Gus breakages of machinery occurred every season:
and still the expression Of juice with single
mills fell under SIXTY per cent, and with double
mills under seventy per cent
During all this time the question of slow running
and fast running mills excited considerable discus
sio1, and the conclusion seemed to be arrived at,
that with given pressure the slower the speed the
greater the per cottage Of extraction but there be-
came evident also the following conclusion, viz:
That with a given pressure the thinner the feed
the greater the per ceniage of extraction. Here
We're embarrassing conclusions. Slow speed Civ
ing better extraction thar fast speed. the cane
planter slowed his mill down, but found no i'm
prOYeTuent IN the extraction, and doubted the &C
Curacy of the theory overlooking the fact that to
accomplish his usual quantity Of work he had in