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Show 8 Atitmmfrlk Mfimkd By an Automobile Expert. If there is anything not clear to you, ask the automobile editor about it. An answer will be published on the completion of tho articles pertaining to each section under discussion. Oylmderllol Tld Tlo3 Tto FrH """"h S. rvn L . ED LESSON" NO. 9. The Four-unit System. In this lesson we are to see how the vibrator coil, explained in the last lesson, les-son, is used with a four-cylinder engine. "While practically all other ignition systems sys-tems have but one coil, where the vibrator vi-brator coil is used, there usually is a coil for each cylinder. For this reason this system is called the ''Four Unit System. ' In the last lesson we saw how the spark was timed by timing the vibrations vibra-tions of the coil. Obviously if we have four cylinders and four coils all that will be" necessary in order to time the four coils and four cylinders will be to have four segments on the timer instead of onlv one. Such a timer in connection connec-tion with the four coils is shown in the illustration. Fig. 1. Instead of having a wire to go to the battery from each of the four coils, thev are connected together by a wire or bar of copper, and a single wire is run from this bar to the battery, or magneto. This bar, which is shown in the illustration, is called a buss-bar. Let us now trace the primary current and. for a change, let us do this backward. back-ward. Thus the current will start at the battery or magneto, then go through the "grounded wire D to the engine, en-gine, "then through the engine to the rotor, through the rotor to the segment seg-ment with which the motor is in contact, con-tact, then to the coil connected to this segment, through the coil, then vibrator, vibra-tor, then to the buss-bar by wire B and so to the switch and back to the battery. bat-tery. You will notice that the current goes only through the coil connected to the segment with which the rotor is in contact, con-tact, so that the secondary current will be produced only on this coil and there will therefore be a spark only in the cvlinder to which the secondary wire of this coil is connected. As the rotor revolves it will come in contact with the next segment, the vibrator cf th1 coil connected with this segment will vibrate, and a spark will be produced in the cylinder whose spark plug i? connected to the secondary of this coil. Thus we get the sparks in the cylinder; one after the oth-r, the order in which thev come depending on the order in which the wires are connected to the coils. In wiring a four-unit system it is the practice to connect the secondary wires from the enils to the pings in numerical, numeri-cal, or 1-2-3-4, r.rdr. and to connect the prirr.arr wires to the timer in the firing fir-ing order, as is shown in the illustration. illustra-tion. As to the so'jrre. of current. Tn the Ford cars the current generally ron' from a magneto. hut to facilitate starting start-ing the enginp, a battery U alo ofen u?ed. a switch being used to switch 1 from the one to the other. Such a switch is shown in the illustration. The Coil Box. The practice is to carry the four coils in a coil box. which box has the binding posts for the wires, so that the coils can be takeu out or put in without touching the wiring. If you will examine ex-amine one of your coils you will find on the one side of it two brass srrews as A and B. Fig. 2. and in the coil box two brass springs in each compartment, which springs can press against the brass screws mentioned above. When the coil is in the box one set of these springs are connected to the buss-b3r which is set in the box. and to which the wire from the switch is connected, while the other set is connected to the binding posts for the wires which must go to the timer. Thus the current instead in-stead of going to the arm Z. as shown in Fig. 1, will first go to the springs mentioned and then to the screw and through a wire hidden in the coil to the arm Z. The current, After passing through the primary coil, will go to the other screw then through the spring pressing against this screw to the binding bind-ing post connected to it and then to the timer. The secondary coil is connected to the piece of brass at the bottom of the coil, marked C in Fig. 2. You will see at the Dot torn of the coil box a piece of carbon which will press against this piece of brass when the coil is in the box. This piece of carbon is conneete-i to the binding post for the secondary wire which is to go to the plug. Timing and Wiring of Four-unit System. The steps to take to time and wire a four-unit pystem are as follows : 1. By turning the engine over bv hand, determine the direction in which the rotor rotates when the crgine is running. 2. Set the firing ordnr. 3. Set the engine so that cvlinder No. 1 ("the cylinder m-.are.r. the rail 1 a tori, is at top dead center between t:ie compression and power stroke. How to do ihh wa explained in detail in the second les nn. 4. Connect the peeoridarv wires in numerical order to the spark pings. . Connect up the battw. One wire will go to the ground the other to the bin 'ling po?t for it on the coil box. 6. Connect the primarv wire's which connect the roiis to the rimer, to their binding post? on th coil box. 7. Ke'rtrd the spark control lver fully and then advance it about a hri.'f inch on its s-egrr.pnt. 5. Determine, which e r 1, o f the tn p augment in the timer wii he fi. -t hit bv the rotor, when it revolving jn direction of roi.-itior., and uith a pencil mark on the outride of Mm tiirer the position of the rnd nf the Kt-gnin t . Then put thr timer in jdaen on th. Pn! Initio an-1 transfer the rnsrk tn the cn I (JiriP. Hcrnnvp the timer. I !. Sf-t thf rotnr so that n line ilrawn i fro'n tii" mar,; you have .H t inri-le to J the rejit- r f.f the rntiir shrift, w-iil i n- I throrh the point nf the rotor which I wfjiil-l first tmich the .';:n-"!!t nf th"j t iuif-r nii'l fa ten it. (Mi I'or't rnr.i it i ii rie ' t'.;trv to rninprrs t),p rntnr a l't-t l't-t le n :iin t i i n .ri nr. n th in the fioi 1 1 rn it will take when in the tirn'T. i I't. I'ln-'e the timer on the engine nnl fonn't (ho wire from roil No. 1 to the top liin'hn '04t. Wher the wire ore in a r,T-i n. o that t lie v ran not tie easily trneei, yon run tell which m eon neite.l to enil No. 1 .y I'linmif the pwit'h nnd th"ti t mir h i n g th wire to, the f ni;ine one ftfu-r tli1 nther, until t.Iin wire wlii-'h will mukrt roil No. 1 vilrn t i q 1 01 in . 'I' he other wire ran he foiinrl lilwif.e ! 1 1. Te-t the netting S'hen the wit-'h in rVne( roil No. 1 MmuM i brat'-, hnt if the ;ark mntrol lever I Im hfc'htlv retar'leo! it. nhnul'l 5 top vi ; br.ititi. If it tniN to ft op th rotor fnnf l;e tnrnerl bn'. a little. Failure of tho roil to vihrate a "ik'n that the rotor Millet, lie rnovnel a little in the n1' 1 i'i t i n of rotation. I'.v not irj n the amount, the p;-m rk entl! rol lexer muni hn r-tnr'l'''i l"fore th1 roil f ri 'i bra 1 in?, or n'lvan'r before it f(arti to i brat'1, vhi ra tt jini t"' 1 he amount t lio rot or muM be movril one way or the other. 2. Af'-r th" rotor han Keen properly p-t, atia-'li the rtt of th" prinuiri' in the firinp nrler, that . if the firing or-i.T i I 2 .'I 4. enil 2 will be nUaehe.l J t h ' frroiul fie'.'Micrit. llit bv the rotlTp four to the third find three In the fourth. t The above, hoinfj t'ivrn In frent do tail, iiinv M'M'rn to be more .liftifull than it n-nlly i'- H would be well for l-'ord owriern to ort of 'ii e-'k up t lie wiiin of their c;t th b v 1 i 11 nvpr the ! 1 -1 , I'i'.en above, without, lakitj off an v ot th v i Ti'-i. I In eitr next bonn I will InVe up the tiiniri of n i 1 -it r i bu t er t, v t 1 1 1 . |