BOSCH High Tension Magneto

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Osborne Benjamin Lucas
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1 FEG - Archiv L El h*. TRADE JR/ßQVL MARK BOSCH High Tension Magneto Type "22 For One Cylinder Stationary Engines o! Compressions up to Six Atmospheres. (Patented and patents pending.) BOSCH MÄGNEJO COMPANY West 46 th Street, New York City, N. Y. CHICAGO :: DETROIT :: SAN FRANCISCO :: TORONTO Factory: SPRINGFIELD, Mass. R. 19o5-2. Second edition.

2 BOSCH MAGNETO COMPANY. 3 Selection of Magnetos. In ordering magnetos, it is necessary to give full information regarding the engine in question, in order that the proper type of magneto may be selected. Spare Part Orders. In ordering spare parts, the type and number of the magneto should be stated, and this will be found engraved on the base plate of the instrument. BOSCH High Tension Ignition for Stationary Engines. Bosch magneto type "22" is intended for stationary engines of compressions not exceeding six atmospheres, and its construction is such that it produces a high tension spark without the aid of batteries or coils, so that the entire ignition system is self-contained and of a very limited number of parts. It is necessary to drive the magneto in absolute synchronism with the engine, in order to obtain the best results, and this is arranged for, not by rotating the magneto armature, but by oscillating it. As the piston rises on the compression stroke, a simple mechanical device draws the armature to one side, and at the moment when ignition is desired the armature is released. The helical springs then cause the armature to return abruptly to its normal position, and it is at this instant that the ignition spark is produced. The speed of the engine is not a factor in the production of the spark, and ignition will therefore be produced at the lowest number of revolutions at which it is possible to crank the engine. The limit of speed of the magneto is 250 trips per minute. DD Chief Advantages. Inexhaustible The current is produced mechanically by trans- Source of Current, forming mechanical into electrical energy. The magnetic field is formed by permanent steel magnets and is practically of unlimited life. No Coil. The Bosch high tension magneto generates its own high tension current directly in the armature winding, and without the use of an induction oil. No Battery. The Bosch high tension magneto is absolutely selfcontained, and no batteries arc required for its operation. Hot Sparks. The sparks produced by the Bosch high tension magneto differ from the short sparks and the sparks of brief duration produced by other systems of ignition. The Bosch high tension magneto sparks appear as small arcs, which endure for a considerable time. _ These arcs are of such intensity that they will ignite much poorer mixtures than can be ignited by the usual battery spark, or by the spark produced by the low tension magneto with transformer coil. High Engine The Bosch high tension magneto produces its spark with Efficiency, absolute accuracy at the determined point in the stroke; this fact, together with the extreme intensity of the spark makes it possible to operate the magneto with much less advance than is required with other ignition systems. The efficiency of the engine is consequently very high Simple Connections. Apart from the cables connecting the magneto to the spark plugs, the Bosch high tension magneto requires^ no external connections. The complication of the electrical system resulting from the numerous connecting wires used with other systems of ignition is entirely absent in the Bosch magneto type "22", which fact greatly reduces the possibility of trouble. Moisture Proof. The construction of the magneto is such that it is impossible for moisture to enter any of the bearing parts. The high tension

4 BOSCH MAGNETO COMPANY. Longitudinal Section. Rear View (End cap taken ojf). 1. Helical springs. 2. Screw bolt. 1. Contact block. 4. Armature shall 5. Long platinum screw. 6.

3 4 BOSCH MAGNETO COMPANY. Longitudinal Section. Rear View (End cap taken ojf). 1. Helical springs. 2. Screw bolt. 1. Contact block. 4. Armature shall 5. Long platinum screw. 6. Flat spring lor magneto interrupter lever Magneto interrupter lever. 8. Condenser. 9. Collecting ring. 10. Carbon brush lor brush holder Brush holder. 12. Flattened interrupter [lange. 13. Short platinum screw. 14. Dust cover. 15. Eccentric bolt. 45. Interrupter housing. 54. Bosch plug terminal. terminal^ is provided with a bell-shaped ebonite cover, the oil holes arc automatically closed by small covers, and the dust cover and end caps are provided with oiled felt strips. The magneto may therefore be used in exposed locations without suffering any injury due to the entrance of moisture or dirt. Description and Operation of the Magneto. Generation A shuttle armature is arranged to oscillate between the of Current, poleshoes of two powerful steel magnets, the armature being drawn to one side by means of a trip lever; and when released by the tripping device, it is returned to its original position by helical side springs 1. 'For four-cycle motors, the tripping device is operated from the cam shaft. Armature Winding. The armature winding is in two parts, one being the primary winding, consisting of a few layers of coarse wire, and the other the secondary, consisting of many layers of fine wire. The circuit-breaking device is connected into the primary winding, and the voltage of the current produced in the secondary winding is greatly increased by the operation of the interrupter at the appropriate point in the movement of the armature. The ignition spark occurs at the instant when the interrupter operates. Primary Winding. The primary winding is grounded on the armature core, and the live end is connected to screw bolt 2, which attaches condenser 8 and contact block 3 to the armature core. Screw bolt 2 and contact block 3 are insulated from the armature shaft 4 and from the metal BOSCH MAGNETO COMPANY. 5 Front View. of the magneto. Platinum tipped screw 5 is supported by contact block 3, and against its platinum tip is pressed the platinum tipped screw 13 attached to the end of interrupter lever 7. Interrupter lever 7 is grounded on the metal of the magneto, and the platinum contacts arc brought together by the pressure of spring 6 when the flattened interrupter flange 12 permits lever 7 to move. The firimary winding is thereore grounded on closed circuit as long as the platinum point on interrupter lever 7 is in contact with the platinum tip of screw 5. The primary circuit is broken when the armature 55. Protecting cap (or 57. Fastening screw lor is being returned to its norinterruptcr housing. mai position by the helical plug terminal Holding spring with 58. Pointed screw «or spring. The condenser 8 post lor interrupter safety spark gap. js conncctcd in parallel _. housing. with the interrupter gap. Secondary Winding. The grounded end of the secondary winding is attached to the live end of the primary, so that one winding forms a continuation of the other. The live end of the secondary winding leads to collecting ring 9 on which slides carbon brush 10 that is supported by brush holder 11 and thus insulated from the metal of the magneto. The spark plug cable is attached to the top of the brush holder 11. A safety spark gap is provided to protect the insulation of the armature and of the current-carrying parts of the magneto against excessive voltage, which would be generated should the secondary circuit be broken when the magneto is oscillated. The safety spark gap is the gap between the point of screw 58 and collecting ring 9. The high tension current discharges across this gap should its normal circuit be interrupted while the magneto is operating. Magneto Interrup- Setllng of steel flange 12 with f* - pftrts.ofthc the oil hole marked A" on top. interrupter are attached Ti } e steel flange 12 with le marked B" on top

6 BOSCH MAGNETO COMPANY. Diagram for Tuning Type (seen from drioing-end). 1. Trip leocr and armature in resting position. to the end of the armature shaft and therefore oscillate with it.

4 6 BOSCH MAGNETO COMPANY. Diagram for Tuning Type (seen from drioing-end). 1. Trip leocr and armature in resting position. to the end of the armature shaft and therefore oscillate with it. A stationary interrupter flange 12 serves as a bearing for the armature shaft and also as a cam for the operation of the interrupter lever 7. For this purpose the steel flange is given a flat at such a point as to permit the interrupter lever to move and the platinum points to come into contact when the armature is under the influence of the tripping device. When the fibre block of lever 7 is in the ii. Trip lever and armature immediately act of passing from the flat to before sparking. the rounded surface of the bearing, the lever is moved and the platinum points arc separated. These parts are so arranged in relation to the armature, that at this instant the voltage of the current induced in the secondary winding will be sufficiently high to cause a very intense spark tojpass between the points of the spark plug. The distance between the platinum points when the lever is depressed must not exceed 35 mm and as a gauge for this distance a metal blade is BOSCH MAGNETO COMPANY. 7 pivoted to the adjusting wrench that accompanies the magneto. When the platinum points are separated by the action of the cam, it should just be possible to slip the gauge blade between them. The adjusting of the steel flange 12 is in accordance with the direction in which the armature is oscillated. It will be noted that four holes are drilled for the fastening of the steel flange, which arc accessible on the removal of end cap 45, and by means of these the bushing may be set in either of two positions. In determining the direction of oscillation, the magneto is to be viewed from the tripping end. If the armature is moved in a right hand or clockwise direction when the springs arc returning it to its normal position, the magneto is known as of clockwise rotation; if the armature is moved to the left hand or in an anti-clockwise direction when it is being returned to its normal position by the action of the springs, the magneto is known as an anti-clockwise instrument. It will be noted that the steel flange 12 is provided with two oil openings marked "A" and "B". For a clockwise magneto, the oil hole of the flange marked "B" is to be placed on top; for an anti-clockwise magneto the flange is to be set with the oil hole marked "A" on top. This setting and the explanation indicating clockwise and anti-clockwise magnetos are illustrated. Attachment of Springs. The springs arc attached and drawn into position by means of eccentric bolts 15. The removal of the nuts on the back of the end plate will permit the bolts to be drawn forward and they may then be rotated so that the bolt heads owing to their eccentricity are a minimum distance from the armature shaft. With the bolts in this position, the springs may usually be attached without exerting force. The bolts are then to be rotated through an angle of 180 by the aid of a bar applied to the holes provided for the purpose, and the springs are thus drawn to the proper tension. The heads of the bolts arc provided with two flats, which fit into the corresponding curves in the end plate when the bolts are pushed back into position. When this is accomplished, the bolt nuts arc to be tightened. Attaching the tripping lever. To attach the tripping lever, end cap 45 must be removed and also dust cover 14. This latter is accomplished by removing the cover screws and pulling the cover upward. The armature should then be brought into the position shown in sketch I, and it is in this position that it will be held naturally by the effect of the magnetic field. With the armature in this position, the platinum tipped screws 5 and 13 and the interrupter should be visible through the recess in the end plate; if they should not be visible, the armature must be given a half turn so that what was formerly the lower head of the armature now becomes the upper head and is visible between the pole shoes. This will expose the platinum points. With the armature in that position, and the springs attached to the tripping lever, the latter should be tightened on the cone of the armature shaft; the dust cover and end plate should then be replaced. Oscillation. The tripping device should be so arranged that the armature is rctatcd through an angle of.30. Spark Plug. The type "22" magneto is to be used in connection with a high tension spark plug, and it is recommended that Bosch plugs be used. The intensity of the spark is such that the points arc subjected to intense heat, and if they

5 8 BOSCH MAGNETO COMPANY. Side View. Mechanical Varying of Ignition. are not made o! proper material, they will burn away rapidly. The points of the Bosch high tension spark plugs are made of nickel alloy and constructed to withstand the heat of the magneto spark. Furthermore, the insulation is of unbreakable steatite and the plugs are so assembled as to make a practically gas-tight joint. The spark plug gap should be about 1/2 mm. Variation of Timing. It is occasionally necessary to provide a means for changing the timing, which will permit starting to be effected with a retarded spark and the spark to be advanced when the engine is in operation. This can be accomplished by the tripping device, so that the instant at which the tripping lever is released may be varied. The arrangement should not alter the angle through which the magneto is oscillated. Such an arrangement is here illustrated and described. Two trip cams are mounted on the engine cam shaft (c) one of them (a) being used for starting and the other (b) being used for normal operation. These cams are placed in such relation to each other that (a) produces a spark in retard while (b) causes an advance of ignition, the latter being for the normal operation of the engine. BOSCH MAGNETO COMPANY. 9 The cams arc mounted on a sliding collar, which may be moved longitudinally on the shaft, and which is caused to rotate with the shaft by a key (e). By sliding the collar either one of the two cams may be caused to operate the trip lever. Between (b) and the fixed collar (fj is a helical spring (g) which tends to hold the collar in a position of advance ignition. On the other side of the collar is mounted a bushing (h), which is mounted on the cam shaft, and over it is fitted a movable hand wheel (i). These form a stop for the collar and hold it in position with the advance cam operating. For starting, the hand wheel is pushed forward to bring the cam (a) under the trip lever and is secured in this position by the bolt (k) dropping into the head (1). When the motor is operating the hand wheel may be held to cause it to slide on bushing (h). The bolt (k) will travel in the curve (I) until it registers with the slot (m). When under the influence of the spring (g), the cam and hand wheel will be pushed outward, the cam (b) then coming into operation. Detection of Faults. Should irregularities in operation occur, the setting of the trip lever on the armature shaft should be verified. In order to test whether the magneto is giving current, the spark plug cable should be removed from its terminal, the cable detached from the spark plug and brought into such* a position that there is a gap of about one millimetre between its end and the metal of the engine. The trip lever should then be operated by hand or by turning the engine, and if the instrument is in good condition, a brilliant spark will pass between the cable and the metal. If this spark appears, it indicates that the magneto is in good condition, and the fault must be looked for in the cable or spark plugs. The cable should be examined for assurances that it is not broken and that the insulation is in good condition. The spark plugs should be seen to be clean and in good condition, and the gap between the points should not be greater than 1/2 mm. If the magneto test docs not show a spark, flat spring 56 should be turned aside to permit the removal of end cap 45. On operating the magneto slightly it should be seen that the platinum points are making contact when the armature is under the influence of the tripping device, and that the platinum points separate when the reflex action of the spring throws the armature past its normal position of rest. Theoxtrome separation between the platinum points should be 35 mm, and this may be ooserved and tested while the trip lever is being held froni 30 to 40" from the vertical in the opposite direction to that in which the cam normally moves. The platinum points may be adjusted by means of adjusting screw 5 and its lock nut, and they should be kept clean. Should the contacts be uneven but only in that case they may be trued with a very smooth flat file. On the completion of the inspection, the end cap should be replaced. Care and Maintenance. The magneto requires no attention other than lubrication. f\ few drops of oil should be injected daily into the holes marked "Oil", and once a week the oil cups should be washed out by the introduction of kerosene. Subsequent to the washing, fresh lubricating oil should be put in. The interrupter should occasionally be cleaned, as has been described. It is of great importance to lubricate the rollers on which the helical springs operate and also the loops of the springs bearing on these rollers. For this purpose heavy oil should be used, or preferably heavy oil made into a paste with flaked or powdered graphite. The breaking of springs 1 is almost invariably due to the lack of lubrication at these points.

6 10 BOSCH MAGNETO COMPANY. 11 Spare Parts for Type "22" Magneto. 49 T Ö. 50» 1 p I. Helical spring. 5. Long platinum screw. (>. Flat spring for magneto interrupter lever Magneto interrupter lever with platinum screw a. Magneto interrupter lever without platinum screw Carbon brush with spring lor brush holder II. 11. Brush holder with carbon brush and spring a. Hiu-.li holder without carbon brush and spring Flattened Interrupter Hange. 13. Short platinum screw. 14. Dust cover with carbon holder II and lock nut 51. Ha. Dust cover only. 15. Kcccntric bolt with annexed parts. 15 a. Eccentric bolt only. 10. Roller lor holding helical spring I. 17. Washer on eccentric bolt Split pin on eccentric bolt Fastening nut tor bolt 15 shalt end plate. 20. Fastening screw for interrupter flange Lock nut for platinum screw 5. 2b. Fastening screw for spring Hexagon nut on front shaft. 33. Washer on front shalt. 40. Fastening screw for shaft and interrupter end plates. 45. Interrupter housing with oil hole cover. 47. Oil hole cover for shalt end plate. 48. Oil hole cover for interrupter housing Fastening screw for'oil hole covers 47 and Spring for oil hole covers 47 and Lock nut for brush holder IIa. 52. Cable with Bosch loop terminal on one end and Bosch plug terminal on other end. (State length of cable ) 53. Bosch loop terminal. 54. Bosch plug terminal f Protecting cap for plug terminal Holding spring with post for interrupter housing Fastening screw for interrupter housing Pointed screw for safety spark gap. 59. Fastening screw for dust cover 14 a. When Ordering please stale besides indicating the number and designation of the desired parts, that they are [or type,,22".

7 12 BOSCH MAGNETO COMPANY. Dimensioned Drawing of Type "22" moisture proof. I - p O^öRo) t- -u- Partly machined trip leoer. Dimensions in millimetres. a! b c d e f g h i k I m n 0 p q r s t « lb IS »]"." %«"J 75 t>

Chapter 4 Ignition & Electrical Systems

Chapter 4 Ignition & Electrical Systems Chapter 4 Section A Study Aid Questions Fill in the Blanks 1. Ignition systems can be divided into two classifications: systems or systems for reciprocating engines.