Page:Motoring Magazine and Motor Life February 1915.djvu/17

, 1915.

A. C. Briggs, Esq.,

Sec'y Automobile Club of Northern Cal. Mills Building, San Francisco, Cal.

Dear Mr. Briggs:

I enclose an article on the subject of an automobile formula which is based on pure science, combined with practical experience in testing gas engines, and which I believe will be fair to the automobile owner, while at the same time placing a premium on brains and honest effort of the automobile manufacturers.

Trusting that the enclosed will be satisfactory, I beg to remain.



On account of the agitation caused by the apparent injustice of the present automobile formula used by the engineering department of the State of California, the writer begs to offer the above as the solution of the problem.

As an example take the case of a Pope 4-cylinder 1912, 50 h. p. 4&frac14; bore x 5&frac12; stroke, the State formula gives the following:

Bore + Stroke &#10799; Bore &#10799; No. Cylinders &#10799; .224&#65309;4&frac34;, + 5&frac12; &#10799; 43&frac34; &#10799; 4 &#10799; .224&#65309;43.624 horsepower.

Then take the Pierce Arrow 1911 six-cylinder 36 h. p. 4 Bore &#10799; 5&#8539; Stroke, the State formula gives the following:

It will be noted that the cubic inches of space in the cylinders in the case of the Pope is 389.864, while in the case of the Pierce-Arrow it is only 386.406, while at the same time the formula gives a horsepower for the Pierce-Arrow 5.426 greater, a manifest injustice.

We will not discuss the question of making the tax in proportion to the horsepower beyond saying that the intervals between the horsepower ratings which is used as a basis for the tax appear to the writer to be altogether too great.

The formula suggested by the writer is based on the one used by the steam engineering profession for arriving at the horsepower of steam engines, and has been thoroughly tried out in practice and found correct. The only difference is that he has simplified it so it could be used by one not having an engineering training. It is as follows:

The meanings of the letters follow:

P&mdash;Mean effective pressure of the explosion of the gas in the cylinder.

L&mdash;The length of the stroke.

A&mdash;Area of the cylinder&mdash;Bore &#10799; Bore &#10799; .7854.

R&mdash;Revolutions of the motor.

N&mdash;Number of cylinders.

2&mdash;Factor caused by the fact that an explosion occurs in the cylinder on alternate revolutions only.

33000&mdash;Number of foot pounds of work in a horsepower.

For the Pope engine the formula works out as follows: where the mean effective pressure is taken as six to correspond with the other condition of taking the stroke in inches instead of feet which the engineering profession does.

For the Pierce-Arrow the formula would be as follows:

It will be seen in the above formulas that the revolutions are taken as 1500 in each case, and as the revolutions of an automobile engine vary considerably, this is a fair average upon which to base our calculations.

Let us assemble some of the factors of the formula and it automatically simplifies itself as follows:

By taking out the number

the formula takes the form

Bore &#10799; Bore &#10799; Stroke &#10799; No. Cyl. &#10799; .1071

The number .1071 can be taken as 1-10, which is near enough for all practical purposes, and by doing this the formula takes the form

While the formula does not agree with the manufacturer's ratings of the above machines, it does give a horsepower which closely represents the true horsepower which the owner is paying for when he buys the machine, and the pardonable pride on the one hand or the modesty of another manufacturer should have nothing to do with the tax rate which the automobile owner should have to pay.

If the ratings were based on the next lowest horsepower to that given by the formula, each owner would be paying in direct proportion to the amount of service which he gets out of his machine, assuming of course that the elegance of fine equipment gives the owner either service or pleasure in proportion to the amount of power which his machine actually has.

It is also true that, with a given bore and stroke, ft is possible by superior design and close attention to refinement in minute detail for one man to get more power than another out of the same dimensions, and accordingly the formula suggested acts as an incentive for a high grade man to aim at high efficiency.

The present method of rating with such large intervals leaves an opening for a manufacturer to make a lower grade article and advertise it as being better than it is, without there being any public display of the fact.

Anybody familiar with the subject knows that in some of the lower priced cars that just come under 30 h. p. the hill climbing and speed possibilities are greater than some of the better priced cars rating 20 h. p. higher according to the State formula, a difference that does not look to be just, and does not appear to the writer to be necessary when the matter can be adjusted so simply.



A method by which streets and boulevards in cities may be beautified despite the backwardness of property owners is provided in a bill introduced in the Senate by Thompson of Los Angeles.

The bill gives the city council or board of supervisors the power to decide what streets shall be beautified by the planting of trees, flowers and grass along the parkways, and that this work may be carried out by the city at the expense of the property benefited. A special tax assessment is provided. This work is to be under supervision of the superintendent of parks.