Chapter II: Part 2

The designers considered it necessary to adopt unusual but
admittedly clever expedients to counteract the great torque
irregularity caused by the excessive maximum pressure. The adoption
of the lower pressure of 800 lbs. would have eliminated the
necessity for the pivoted spring-mounted counterweights and the
shock-absorbing rubber propeller-drive.... The use of such high
pressures is in reality the quick and easy way to secure high-speed
operation and can be justified only from this standpoint, although
the resulting increased difficulty in keeping the engine light
enough was a strong offsetting factor.[36]

Insofar as the engine life was concerned it is true that 1,500-psi
peak pressures were observed but the engine was so developed to
withstand these pressures.... One of the most severe problems
connected with the development of this engine was the piston ring
sealing. Special compression rings were made with no gaps and
further work in this respect could have been used to advantage had
the engine been kept in production.[37]

It is significant that in 1930 the Packard diesel had a compression ratio of 16:1, whereas in 1931 it has been reduced to 14:1. This was probably done to reduce vibration and the problem of piston-ring sealing.[38] The exhaust products had an unpleasant odor which was particularly objectionable during taxiing. Professor C. Fayette Taylor, writing in the January 1931 issue of _Aviation_, remarked about this fault: "One is inclined to question whether the disagreeable escaping of exhaust gas from the intake ports can be overcome, while still retaining the obvious advantages in weight and simplicity of the single valve." The engine exhaust deposited a black oily film. In fact some airplanes fitted with the Packard diesel engine were painted black, so that soot deposits from the exhaust would not be noticed.[39] Since the passengers' and pilots' compartments were generally located behind the engines, and were not airtight, damage to clothing resulted. This fault could have been eliminated by the use of separate valves for the intake and exhaust systems.

It was not possible to start the engine when the temperature dropped much below 32 deg. F unless glow plugs were used. These spark-plug-like devices, which were only used for starting, had resistance windings which glowed continuously when turned on. The additional heat glow plugs provided made starting an easy matter in the coldest weather; however, they complicated the design of an engine noted for its simplicity, and they used so much electricity that only a long flight would allow the generator to fully recharge the battery.

H. R. Ricardo, writing in the June 4, 1930, issue of _The Aeroplane_ said: "Referring to the very fine achievement of the Packard Company of America in producing a small radial air-cooled heavy-oil engine, a petrol engine of similar design and with the same margin of safety would weigh less than 1-1/2 lbs. per hp." The important point made is that a gasoline engine designed along the same lines as the Packard diesel would weigh considerably less, but would then suffer from the Packard's reduced structural safety factor. It is significant that as the Packard developed, it became heavier.[40]

Like other diesels, the Packard cost more to build than a comparable gasoline engine, because of the type of construction required for the diesel's higher maximum cylinder pressures and the difficulty of machining the fuel injectors. Having fuel injectors, the engine was more sensitive to dirt in the fuel system than a carburetor-equipped gasoline engine.[41] The fuel injectors were "a crude and deficient mechanism" subject to rapid wear, and often these injectors caused smoking exhausts and high fuel consumptions.[42] In the event of battery or starter failure, a comparable gasoline engine could be started by swinging the propeller. Because of the engine's high compression, it would have been impossible to have hand-started a Packard diesel this way.

In a letter to the Air Museum, January 15, 1962, Dorner commented: "During my first demonstration (of high-speed diesel engines) in 1926 in California and later in Detroit I learned from Capt. Woolson that the large transport airlines were controlled by oil companies which were not interested in (supplying) two different kinds of aircraft fuel, and in savings of fuel." The May issue of _Aero Digest_ had a full-page illustrated advertisement titled "Announcing National Distribution for Texaco Aerodiesel Fuel." Although distribution was limited, the American oil industry did not prevent the airplane diesel from becoming a success in the civil market. However, it is significant that the advertisement was placed by Frank Hawks of the Texas Company largely as a gesture of friendship to Woolson.[43]

The situation in the military market was different, however, as testified by this quotation from the same letter. "The military administration, having paid all of the expenses for the testing period to that date (1931), came after the tests to the conclusion that the advantages of the diesel as compared to its disadvantages did not justify the great risk to procure and distribute two different kinds of fuel in case of war."

Two accidents, which received wide publicity and no doubt did considerable harm to the entire project, occurred to Packard diesel-powered airplanes. The following quotation is from the _Herald Tribune_ for April 23, 1930: "Attica, New York--Losing their bearings in a blinding snowstorm and mistaking the side of a snow-covered hill for a suitable landing place, three men, one of them Capt. Lionel M. Woolson, aeronautical engineer for the Packard Motor Company and adapter of the diesel engine to airplanes, were killed here today."

The second of these accidents is described in the September 1931 issue of _U.S. Air Services_:

Columbus wanted to sail west beyond the limits set by the learned
navigators of his time, and in much the same consuming fashion
Parker D. Cramer wanted to show his generation and posterity that
a subarctic air route to Europe via Canada, Greenland, Iceland,
Norway, and Denmark was feasible.... On July 27, without any
preliminary announcement, Cramer left Detroit in a Diesel-engined
Bellanca, and following the course he took with Bert Hassel three
years ago, he flew first to Cochrane, on Hudson Bay. His next stop
was Great Whales and then Wakeham Bay. From there he flew to
Pangnirtum, Baffin Land, and across the Hudson Straits to
Holsteinborg, Greenland. He crossed the icecap at a point farther
north than the routes that have been discussed heretofore, but
almost on the most direct or Great Circle route from Detroit to
Copenhagen. He was accompanied by Oliver Paquette, radio operator.
They were on their way more than a week before they were
discovered. To Iceland, to the Faroe Islands, to the Shetlands.

They were taxiing across the little harbor of Lerwick, Shetland
Islands, when a messenger from the bank waved a yellow paper. It
was a warning of gales on the coast east to Copenhagen. Cramer
apparently thought it was an enthusiastic bon voyage, and, after
circling the town, flew away. A Swedish radio station reported a
faint "Hello, Hello, Hello" in English, but the plane was not seen
again.

As the result of a personal conversation with his brother, William A. Cramer, in 1964, the author learned that the fuselage and floats of the airplane were found six weeks later. Since there was no indication of a heavy impact (not a single glass dial on the instrument panel was broken), a successful landing must have been made. Several weeks later, a package was found wrapped in a torn oilskin containing instruments, maps, and a personal letter, all substantiating the evidence that the landing was successful. It can only be surmised that there was engine failure, probably due to a clogged oil filter.[44]

Once before during the trip a forced landing had been made due to engine malfunctioning, and a successful takeoff was accomplished in spite of a moderately rough sea. This time, however, storm conditions probably made the takeoff impossible.

As a final summary of the author's analysis of the Packard diesel engine, it must be emphasized that although the engine burned a much cheaper and safer fuel more efficiently than any of its gasoline rivals, it was too unreliable to compete with them. Even if it had been reliable, it was too small to be useful to the large transport operators, to whom its fuel economy would have appealed. In addition, this mechanism operated on the wrong cycle: 4-stroke, rather than the lighter, more compact, and more efficient blown 2-stroke cycle. Lastly, it was doomed by the advent of high octane gasolines, first used while it was still in the development stage. These new fuels reduced the diesel's advantage resulting from low fuel consumption, and, in addition, gave the gasoline engine a definite advantage from the standpoint of performance. The Packard diesel was a daring design but, for the reasons analyzed in this chapter, it could not meet this competition, and therefore failed to survive.

Appendix

1. Agreement between Hermann I. A. Dorner and Packard Motor Car Company

THIS AGREEMENT made this 18th day of August 1927, by and between HERMANN DORNER, of Hanover, Germany, hereinafter referred to as "Licensor", and PACKARD MOTOR CAR COMPANY, a Corporation of the State of Michigan, United States of America, of Detroit, Michigan, hereinafter referred to as "Licensee";

WITNESSETH, that

WHEREAS, Licensor owns certain Letters Patent of the United States and other countries relating to oil burning engines under which he desires to license the Licensee;

WHEREAS, Licensee desires rights under said Letters Patent;

NOW, THEREFORE, for the mutual considerations hereinafter set forth, the parties have agreed as follows:

1. Licensor warrants that he is the inventor of an oil burning engine, is the sole owner of United States patent Number 1,628,657, dated May 17, 1927, and United States patent applications, Serial Numbers 46,383 filed July 27, 1925, and 88,409 and 88,411, filed February 15, 1926, relating to such engines and is joint or sole owner of patents or patent rights relating to said engines in England, Germany and Sweden.

2. Licensor agrees to furnish the Licensee at cost price but not exceeding Thirty Dollars ($30.00) cash, as many pump and nozzle units as are needed for use in building one or more experimental engines.

3. Licensor hereby gives and grants unto Licensee an exclusive license for the manufacture, within the United States and its dependencies, and a non-exclusive license for the use and sale, of engines for aircraft, and a non-exclusive license for the manufacture, use, and sale of engines for motor vehicles and motor boats, under said United States patent Number 1,628,657, under all after-acquired patents and under all patents that may result from said patent applications, and from all other patent applications pertaining to his present oil burning engine or reasonable variations thereof, such licenses to extend for the full life and term of all such patents, provided however, that there is specially excepted from this grant--stationary engines, tractor engines, and engines for agricultural purposes.

4. Licensor further hereby permits said Licensee to export to all other countries and sell and use there, without further royalty, all engines made by Licensee in the United States under this license.

5. Licensor acknowledges receipt of One Thousand Dollars ($1,000.00) in payment of a portion of the expenses heretofore incurred by him and as one of the considerations for this agreement.

6. Licensor agrees to devote all time necessary from this date to November 1, 1928 to supervision of the design of an engine and construction thereof at the plant of the Licensee and will in his absence furnish the services of a competent assistant, the expenses of Licensor and assistant to be paid for by Licensee at the rate of One Thousand Dollars ($1,000.00) per month for the first three (3) months, and Five Hundred Dollars ($500.00) per month thereafter until the decision in paragraph eight has been made by Licensee.

7. Licensee agrees to build and test at least one experimental aircraft engine with special Dorner features, and to take all reasonable measures to reach the stage of final test. All Dorner feature engines made by Licensee will be marked "Licensed Under Dorner Patents."

8. Within one year after the completion of tests of the aircraft engine built by Licensee hereunder, or in any event not later than November 1, 1928, Licensee will decide whether it will proceed with the manufacture of engines hereunder, or not. If Licensee decides in the affirmative then it will pay Licensor forthwith the sum of Five Thousand Dollars ($5,000.00) as advance on royalties and as minimum royalty for the first production year. If Licensee decides in the negative for reasons which are under the influence of Licensor, then Licensee will give Licensor notice and sufficient time to try to correct possible imperfections, and the time for final decision will be correspondingly extended. If the reasons for the negative decision are under the influence of Licensee, then Licensee will grant to Licensor an oral conference at Detroit and explain the reasons in detail. In event a negative decision is finally rendered by Licensee this agreement may be terminated at any time thereafter upon sixty (60) days' notice in writing to Licensee and both parties released from all further obligations hereunder.

9. Licensee agrees that if after three (3) years from the date hereof Licensee is not manufacturing and does not contemplate the manufacture of, a certain size and type of aircraft engine which Licensor would like to grant another manufacturer the right to build and which would not reasonably compete with anything manufactured by Licensee, Licensee will release such size and type aircraft engine from the exclusiveness of this license and thereby permit Licensor to grant a license to such other manufacturer to make, use and sell such engine and such engine only.

10. Licensee agrees to pay royalty on all engines manufactured and sold or used under this agreement, based on effective brake horsepower under normal load, as follows:

On each of the first Five Thousand (5,000) such engines produced
and sold in any one calendar year, the royalty shall be at the rate
of Twenty-five Cents ($.25) per horsepower; and on all over Five
Thousand (5,000) in such calendar year, at the rate of Ten Cents
($.10) per horsepower;

provided that, after a total of Fifty Thousand Dollars ($50,000.00) has been paid in royalties the royalties shall be reduced one-half (1/2).

11. After the beginning of the second year of production, Licensee agrees that if the royalties under the above schedule amount to less than Ten Thousand Dollars ($10,000.00) per year then the royalty shall be Ten Thousand Dollars ($10,000.00) per year payable in quarterly instalments of Two Thousand Five Hundred Dollars ($2,500.00) each, or in other words, the minimum royalty payable shall be Ten Thousand Dollars ($10,000.00) per year.

12. Royalties shall continue only during the life of said patent Number 1,628,657, and when a total of Two Hundred Fifty Thousand Dollars ($250,000.00) has been paid by Licensee to Licensor, all royalties shall cease and the license hereunder shall be free thereafter.

13. Licensor agrees that Licensee shall have the benefit of any more favorable royalty rates that may be hereafter granted to or enjoyed by any other manufacturer of engines other than aircraft engines.

14. Licensee agrees to keep proper books of account showing the number of engines manufactured and sold or used under this agreement and to report quarterly to Licensor.

15. In case of suit against the Licensee for infringement of patents by any of the Dorner features built under this license Licensor agrees to assist in the defense of any such suit and pay the expenses thereof up to an amount equal to Ten Percent (10%) of all royalties paid by Licensee to Licensor hereunder.

16. In event of default of the Licensee in the payment of any of the sums herein provided for, Licensor may terminate this license agreement by serving upon the Licensee Sixty (60) days' notice in writing of its desire and determination so to do and stating the default upon which the notice is based, and at the expiration of such Sixty (60) days this license shall thereupon be terminated, provided however that such termination shall not release the Licensee from obligations already accrued hereunder and not performed, and provided further that if, during said Sixty (60) days' notice period, the default named in said notice shall have been made good then this license to continue as if no default and notice had been made or given.

17. At the expiration of any one year from November 1, 1929, Licensee may terminate this agreement upon Sixty (60) days' notice in writing to Licensor of its desire and determination so to do, provided however, that such termination shall not release the Licensee from obligations already accrued hereunder and not performed.

18. In case of differences of opinion regarding any of the terms of this agreement, the dispute shall be submitted to arbitration. Each party shall select one arbitrator and if they, after five days, fail to agree upon a third, the United States Court for the Detroit District shall be asked to appoint such a third arbitrator, and the decision of a majority of the arbitrators shall be binding upon both parties.

In witness whereof, we have hereto set our hands and seals at Detroit, Michigan, on the day and year first above written.

Witnesses--(Signatures):

Hermann Dorner
L. A. Wright
Adolf Widmann

PACKARD MOTOR CAR COMPANY
Alvan Macauley
President

(Seal)

Attest: Milton Tibbetts
Assistant Secretary

2. Packard to Begin Building Diesel Plane Engines Soon

_Will Start Construction at Once on New Three Story Factory to Handle Work_

[From _Aviation_, March 2, 1929, vol. 26, no. 10]

DETROIT, MICH.--Indications that the Diesel type airplane engine, recently developed by Capt. L. M. Woolson, chief aeronautical engineer of the Packard Motor Car Co., will become a commercial reality and possibly a revolutionary factor in airplane engine design, is seen here in the announcement of the concern that it will begin construction immediately of a $650,000 plant to produce the engines in large quantity for the commercial market.

The new plant, according to the announcement by Hugh J. Ferry, treasurer of the Packard firm, will be completed and in operation within five weeks. Between 600 and 700 men will be employed and, according to expectations, production will be carried on at the rate of about 500 Diesel engines per month by July.

The Packard Diesel was announced first in October, following experiments covering several years. The original engine was placed in a Stinson-Detroiter, which was flown successfully by Captain Woolson and Walter Lees, Packard pilot. Since that time Captain Woolson has built four of the engines, all of 200 hp. capacity, developing 1 hp. for every 2 lb. of weight.

The Diesel, installed on the Stinson-Detroiter, it was said, now has had 200 hr. flying time, and gives not the slightest indication that it will need an overhauling for some time. The other three engines have been tested on the block in the company's research plant.

It is claimed by the builders that the Packard Diesel will produce a saving of about 20 per cent. in fuel consumption as compared with engines using gasoline. It is claimed further that the Diesel will prove far more reliable in construction than any airplane engine yet developed. Evidence of this, it was pointed out, is seen in the performance of the initial Diesel.

DETAILS NOT ANNOUNCED

Although neither Mr. Ferry, nor Captain Woolson, would disclose any technical details as to the engine's construction in making it applicable to airplane use, the secret of its success was reported to be an especially designed pumping device creating high compression necessary for Diesel firing.

Since announcement of the engine, the Packard factory has been literally a Mecca for engineers from many parts of the world wishing to see the engine. The Crown Prince of Spain, in Detroit last fall, was given a flight in the Diesel powered Stinson. None of the construction secrets, however, have been divulged, it was said.

The Packard announcement set at rest rumors that the company planned construction of a plant costing several million dollars, as well as reports that the company was going into the production of airplanes. "Our efforts," Mr. Ferry said, "will be confined to the engine, or power plant end of the aircraft industry. We will continue to build the water-cooled type we have been producing for years." The new Diesel plant will be primarily an assembly plant, although some machine work will be done there. The bulk of the machine work, however, will be done in the present Packard machine shops.

Although no approximation of selling price on the new Diesel was divulged, it was intimated that the engine will retail at a price competitive with or slightly under the price of present gasoline consuming air-cooled engines of that horsepower range. Captain Woolson will have complete charge of the Diesel plant, it was announced.

3. Effect of Oxygen Boosting on Power and Weight

[From P. H. SCHWEITZER and E. R. KLINGE, "Oxygen-Boosting of Diesel Engines for Take-Off," _The Pennsylvania State College Bulletin_ (April 1, 1941), vol. 35, no. 14, p. 25.]

_Practical Conclusions_

Airplanes require about one third more power during the take-off than in flight. In diesel-engined airplanes the size of the engine could be reduced by 25 percent by feeding oxygen into the intake air during the takeoff. Applying the results of the experiments to a transport plane, Fig. 31 shows the possible weight saving with various oxygen boosts. The curves are based on 6000 cruising horsepower and an estimated engine weight of 2 lb per hp.

For the take-off 8000 hp are necessary. To supply the additional 2000 hp, 200 lb of oxygen are fed into the intake air during the take-off. The volume of 200 lb of liquid oxygen is approximately 20 gal. Standard liquid air containers of 55 litre capacity weigh 75 lb. Therefore the weight of the oxygen and container is 350 lb while the possible saving in engine weight is 4000 lb. The weight per take-off horsepower is thereby reduced from 2 to 1.54 lb. The calculation is shown in Table 1.

Oxygen addition may be used for starting diesel engines. The raising of the oxygen concentration from the normal 21 per cent to 45 per cent was found to be equivalent to a raise of approximately 10 cetane numbers as far as starting is concerned.

Five per cent increase in oxygen concentration eliminated exhaust smoke completely.

TABLE 1

Normal horsepower 6000

Take-off horsepower 8000

Normal fuel consumption 0.4 lb per hp-hr, or
53.5 lb per min
Normal air consumption 900 lb per min

Normal oxygen consumption, 21 per cent oxygen 189 lb per min
concentration

Boosted oxygen consumption, 32 per cent oxygen 289 lb per min
concentration

Oxygen to be supplied 100 lb per min

Weight of 8000-hp engine 16,000 lb

Weight of boosted 6000-hp engine 12,000 lb

Weight of oxygen for 2-min boost 200 lb

Weight of container for 29 lb of liquid oxygen 150 lb

Net weight saving by oxygen boost 3650 lb

Weight per horsepower, nonboosted engine 2 lb

Weight per horsepower, boosted engine 1.54 lb

Footnotes:

[1] Appendix, p. 43.

[2] Letter, Hermann I. A. Dorner to National Air Museum, March 3, 1962.

[3] See p. 20 ff.

[4] Appendix, p. 46.

[5] _Aeronautics_ (October 1929), vol. 5, no. 4, p. 32.

[6] _The Packard Diesel Aircraft Engine--A New Chapter in Transportation Progress_ (Detroit: Packard Motor Car Co., 1930), p. 5.

[7] A memorial to Woolson who was killed in the crash of a Packard diesel-powered Verville "Air Sedan" on April 23, 1930.

[8] _Packard Inner Circle_ (April 18, 1932), vol. 17, no. 6, p. 1.

[9] _Aero Digest_ (February 1932), vol. 20, no. 2, p. 54.

[10] Letter, Richard Totten to National Air Museum, January 28, 1964.

[11] _Instruction Book for the Packard-Diesel Aircraft Engine_ (Detroit: Packard Motor Car Company, 1931), p. 3.

[12] _S.A.E. Journal_ (April 1930), vol. 24, no. 4, pp. 431 and 432.

[13] Letter, Richard Totten to National Air Museum, January 28, 1964.

[14] Letter, Hermann I. A. Dorner to National Air Museum, December 16, 1961.

[15] _The National Aeronautic Magazine_ (April 1932), vol. 10, no. 4. p. 18.

[16] _Aviation_ (May 1931), vol. 30, no. 5, p. 281.

[17] _The Packard Diesel Aircraft Engine_, p. 5.

[18] _Instruction Book for the Packard-Diesel Aircraft Engine_, p. 3.

[19] "Test of Packard-Diesel radial air-cooled engine," Navy Department, Bureau of Aeronautics, Report AEL-335, July 13, 1931, Bu. Aer. Proj. 2265.

[20] _Aviation_ (May 1931), vol. 30, no. 5, p. 281.

[21] Letter, Clarence H. Wiegman to National Air Museum, November 1, 1961.

[22] Letter, Dorner to National Air Museum, January 15, 1962.

[23] Letter, Hugo T. Byttebier to National Air Museum, October 20, 1961.

[24] Letter, Clarence D. Chamberlin to National Air Museum, February 8, 1964.

[25] RUTH NICHOLS, _Wings For Life_ (Philadelphia and New York: J. B. Lippincott Co., 1957), p. 205.

[26] Letter, Richard Totten to National Air Museum, January 28, 1964.

[27] Letter, Richard Totten to National Air Museum, January 28, 1961.

[28] _Aero Digest_ (February 1931), vol. 18, no. 2, p. 58.

[29] "50-Hour Test of Packard Diesel Aircraft Engine," Packard Motor Car Company, Detroit, Michigan, serial no. 426, test no. 234-73, February 19, 1930.

[30] Blower in this sense refers to a low-pressure air pump (supercharger) designed to increase cylinder scavenging efficiency by blowing out exhaust gasses. In doing this it also increases somewhat the amount of fresh air introduced into the cylinders. Woolson invented a 2-stroke cycle blown engine; the patent was issued in 1932 (patent 1853714) with rights assigned to the Packard Motor Car Company. (Woolson himself died in 1930.)

[31] A 2-stroke cycle engine completes 360 deg. of crankshaft rotation in what it takes a 4-stroke cycle engine 720 deg. to accomplish. A 3-cylinder two-stroke cycle engine therefore has the same capacity to do work as a 6-cylinder four-stroke cycle engine. For this reason the former type of engine is both more compact and lighter than the latter type.

The above advantages, plus the increased efficiency of the blown 2-cycle diesel, are discussed in _Flight--The Aeronautical Engineer Supplement_ (December 26, 1940), vol. 19, no. 11, pp. 545 and 552.

[32] Packard advertisement--_Aero Digest_ (June 1930), vol. 16, no. 6, p. 23.

[33] _Aviation_ (March 15, 1930), vol. 28, no. 11, p. 531.

[34] _The National Aeronautic Magazine_ (April 1932), vol. 10, no. 4., p. 18.

[35] Appendix, p. 47.

[36] See Woolson's patent 1794047, issued in 1931 and assigned to the Packard Motor Car Company. "An object of my invention is to automatically regulate the compression ratio in an engine inversely to the speed...." See also his patent 1891321, issued in 1932 and assigned to the Packard Motor Car Company. It describes a similar but nonautomatic system. Woolson therefore fully realized the disadvantages of the high cylinder pressures his engine developed at high rpm's.

[37] Letter, Clarence H. Wiegman to National Air Museum, November 1, 1961.

[38] Ibid.

[39] Major George E. A. Hallet, U.S. Air Service, former director of engineering division, McCook Field, Dayton, Ohio.

[40] "Test of Packard-Diesel radial air-cooled engine," Navy Department, Bureau of Aeronautics, Report AEL-335, July 13, 1931, BuAer Proj. 2265.

[41] _Aviation Week and Space Technology_ (February 19, 1962), vol. 76, no. 8, p. 101.

[42] _Aeronautics_ (October 1929), vol. 5, no. 4, p. 31.

[43] Letter, Richard Totten to National Air Museum, January 28, 1964.

[44] According to Frederic E. Hatch of the National Air Museum, it is possible that the engine failed because the fuel injectors became clogged. He notes that the airplane refueled at several fishing ports, and therefore must have used diesel oil set aside for fishing boats. This oil was generally quite dirty. As a result it was routine for the fishermen to have to clean engine oil filters frequently enroute. The oil filters of the Packard diesel could not be cleaned in flight.

Transcriber's Notes:

Passages in italics are indicated by _underscore_.

Passages in bold are indicated by =bold=.

The following misprints have been corrected:
"crackcase" corrected to "crankcase" (page 16)
"is is" corrected to "it is" (page 36)

Other than the corrections listed above, printer's inconsistencies in spelling, punctuation, and hyphenation usage have been retained.