102 
American Agriculturist, August 18,1923 
Perhaps You Will Find the Answer Here 
Mechanical Problems and Troubles of A. A. Readers Answered Briefly 
An Ohio reader asks the following: “I would like 
to know if there is any kind of oil I could use for 
painting rough out-buildings besides linseed oil, 
something that would come cheaper. What is the 
name of such oil and where can I get it.” 
ISH oil has been used for this purpose 
either alone or mixed in varying propor¬ 
tions with linseed oil. The impression is, 
however, that in general the use of this oil 
is not satisfactory. Personally we would pre¬ 
fer to use linseed oil entirely even though it 
costs a little more. 
* * * 
Grounding a Metal Roof 
I am contemplating rebuilding my barn. What 
bothers me most is what to use for the roof. Would 
you please give me your opinion about galvanized 
steel roofing? If properly grounded, will it take the 
place of lightning rods? What would be the proper 
way to ground it? It may interest some other read- 
‘ ers of American Agriculturist if you should give a 
a little article about it.—C. K., New York. 
ETAL roofs have in general, proven to 
be very satisfactory. But a»metal roof 
in itself is no protection against lightning. It 
must be well grounded from at least two 
corners and preferably from four. Either 
lightning-rod points must be spaced along 
the ridge about twenty feet apart or a sharp 
edged or notched metal ridge-board must be 
placed on top of the ridge. If lightning-rod 
points are used, they must be connected with 
the roof, but need not be connected to the 
ground wires. Under no conditions should a 
round-ridge roll be used unless points are 
provided. 
Ground connections for lightning conduc¬ 
tors are of vital importance and must be 
properly made. These ground connections 
should extend down to permanent moisture. 
This depth, of course, will vary in different 
localities. In deep soils, in many locations 
eight feet is sufficient. In deep soils, a hole 
may be dug, drilled or driven the desired 
depth and the cable run down in it. In shal¬ 
low soils the grounding is necessarily a little 
more, elaborate. * * * 
Engine Needs Reboring 
I have a gasoline engine in which the cylinder is 
worn so it throws oil on the spark plug; new rings 
do not seem to help it. I would have it rebored and 
a larger piston put in, but a garage man tells me 
that the inside of every gasoline and automobile en¬ 
gine cylinder is case-hardened or glazed over to pro¬ 
tect against wear, and by boring it it cuts this hard 
surface, and the cylinder will soon leak worse than 
ever. He said a better way is to use emery cloth and 
smooth or even up the cylinder in that way. Please 
let me know which would be the best, boring, emery 
cloth, or a new engine? The engine is otherwise in 
good condition.—H. G., New York. 
E are very much inclined to believe that 
your garage man is misinformed about 
the condition of the interior of the cylinder 
of a gasoline engine. We have never heard of 
the interior cylinder walls being case-hard¬ 
ened. It is true that sometimes due to long 
wear they become very highly polished and 
have a glazed appearance, and there may be 
some slight oxidation which causes a scale to 
develop somewhat harder than the metal 
itself, but of this we are doubtful. 
When the cylinder of a gasoline engine be¬ 
comes so badly worn that new rings care¬ 
fully adjusted do not aid in the compression, 
then the only thing to do is to rebore the 
cylinder, putting in new oversize pistons. 
The amount of metal that must be removed 
will vary according to the amount of wear, 
but no more should be removed than is neces¬ 
sary. Sometimes this reboring is done on a 
lathe, or a special reamer may be used, par¬ 
ticularly if the cylinder diameter is small, 
There are, also grinding machines which will 
do this work, but this process is more ex¬ 
pensive. 
The method suggested by your garage 
man; that is to use emery cloth is impracti¬ 
cal. If you really want to get your cylinder 
put up in good shape, we would advise you to 
seek the services of some other mechanic, 
because judging from the misinformation 
which has been supplied by the one you have 
already consulted, he is not particularly safe 
to trust with a good piece of machinery. 
* * * 
Building a Concrete Reservoir 
Please tell me what will be the cost of building a 
reservoir 10 x 10 x 8, walls 8 inches, top 6 inches 
thick? Do you think this thick enough? Cement 90 
cents per hundred, sand and gravel cost nothing. 
Will twenty feet of fall be enough pressure for 
range boiler and other fittings? Would like you to 
tell me number of cubic feet of each material heeded? 
—W. L., New York. 
T HE materials required for constructing a 
concrete reservoir 10 feet square and 8 
feet deep with walls that taper from 8 inches 
to 6 inches at the top will be approximately as 
follows: 66 bags of cement 3.8 of a cubic 
yard of sand, and 3.4 of a cubic yard of 
pebbles or crushed stone. This is on the 
assumption that a 1-2-4 mixture will be 
used, which if properly handled will give 
good results. 
A 20-foot fall should give you sufficient 
pressure to run water through the range 
boiler and other fittings. Each foot of eleva¬ 
tion will give you a pressure of .434 pounds, 
so that even allowing for reduction because 
of friction, you will have 7 or 8 pounds pres¬ 
sure available. 
* * * 
Timing the Valves and Spark 
The crank shaft in our truck broke, causing the 
cam and crank shaft gears to get out of “time.” We 
retimed them and set the breaker points to separate 
just after dead center on retard spark. In going up 
a hill on high, running the engine slow, it runs bet¬ 
ter on the advance spark than it did formerly on re¬ 
tard and it appears to have more power. How far 
ahead of dead center can the breaker points part 
before it causes the engine to kick back in cranking? 
—E. B., New York. 
W HEN you retimed the motor you very 
likely got it just about right. This motor 
is timed so that the platinum points just 
break when the motor is slightly past top 
dead center. The greater the advance the 
better the engine will run up to a certain 
point. When advancing the spark too far 
the engine will kick back. However, it runs 
most economically when the spark is ad¬ 
vanced as far as it will go without causing 
a pound. 
To time the magneto, turn the engine over 
until number one piston is 1/32 inch past 
top dead center on the power stroke, retard 
the contact breaker and move the armature 
either to the right or left until the platinum 
points just break with the "cylinder in this 
position. You will see that the power engine 
is not far past dead center if the piston is 
moved only 1/32 inch on the power stroke. 
Do not set the spark too near dead center on 
a high-speed motor. In some motors the 
spark occurs 45 degrees before the piston 
reaches dead center on the compression 
Determining Speed of Saw 
How fast should the edge of a circular saw blade 
travel? What diameter saw would a 12-22 tractor 
handle to the best advantage?—E. H., New York. 
T HE average rim speed of a circular saw 
is about 9,000 feet per minute. The rim 
speed of a saw operated by steam feed may 
be increased to 12,000 feet per minute. To 
obtain the rim speed of a saw multiply the 
diameter in inches by 3.14 which will give 
the circumference, and divided by twelve 
will give the answer in feet, and multiply the 
figure obtained by the speed at which the saw 
is operating; the answer is rim speed in feet 
per minute.' For example, assume that we 
want to know the rim speed of a 20-inch saw, 
running at 1,800 R. P. M., multiply 20 by 
3.14, divided by 12, equals 5.23, and this 
times 1,800, equals 9,414, which is the rim 
speed of the saw. 
A 12-22 tractor ought to handle a 36 or 40- 
inch saw very easily. So far, there are no 
saw attachments on the market for this 
tractor. 
To find the diameter of the driven pulley, 
knowing the diameter and revolutions of the 
driving or engine pulley, multiply the di¬ 
ameter of the driver by the number of revolu¬ 
tions, and dividing the product by the 
number of revolutions of the driver. As¬ 
sume, for example, a 10-inch pulley on an 
engine running at 900 R. P. M., and the 
revolutions of your driver is to be 1,500, 
multiply 10 by 900, equals 9,000, and divid¬ 
ing this by 1,500 will give 8, which is the 
diameter of the driven pulley. 
* * * 
Straightening Saw Mandrel 
I have a 4-horsepower sawing rig on which the 
saw shaft is bent. Would the shaft keep its shape 
after being straightened? Would you advise getting 
a new shaft?—E. P., New York. 
I T depends on how much a new mandrel for 
the saw would cost, whether it would be 
better to get a nev one or have the old one 
straightened. Straightening a shaft is not 
a very difficult proposition, and if you have 
a good mechanic available and if the mandrel 
is not sprung too much, there is no reason 
why the straightening could not be accom¬ 
plished without any trouble. But if the bend 
is very bad and tiiere would be danger of 
cracking, the mandrel in the straightening 
process, it would naturally be sensible to get 
a new mandrel. The best thing to do would 
be to write to the manufacturer of the saw 
and find out how much a new mandrel would 
cost and compare it with the estimate of 
straightening the old one. 
* * * * 
Water Wheel to Generate Current 
I intend putting in a small water-power electric 
plant this summer. As a rule I have about fifty 
cubic feet of water flowing and can obtain fall 
enough to install about a seven-foot overshot wheel. 
I am making the wheel myself, and would like to 
know, with a two-foot head behind the wheel, about 
how many lights I could have and about how much 
power I would have? Would you advise putting in 
wide blades in the wheel? I am making it with 
three-foot buckets, that is, the wheel will be three 
feet wide. I am making it wide on account of hav¬ 
ing so much water, at certain times the creek will 
stay up for a week or two at a time.—H. H., New 
York. 
I F the 50 cubic feet of water you mention 
is the amount that flows per minute, you 
will have power enough to make a very nice 
installation with your 7-foot wheel, and with 
a 2-foot head behind it, you should develop 
something pretty close to % H. P., or con¬ 
sidering loss of power, the resulting effi¬ 
ciency of the wheel will give you not less 
than !/2 H- P- This in itself will operate a 
generator large enough to give you current 
sufficient for a number of lights, and for 
small motors such as are included among the 
various items of equipment commonly used 
around the house, such as washing machines, 
churn, vacuum cleaner, etc. 
If you want to include in your installation 
a storage battery, which of course will add 
something to the expense, you will have an 
even larger amount of current available at 
least part of the time. Whether this addi¬ 
tional outlay of money will be profitable or 
not can only be determined by a careful 
analysis of your power • requirements. It is 
advisable to make the wheel rather wide. 
