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Show 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 the articles pertaining to each section under discussion. LESSON NO. 41. The Disc Clutch. The numhi-r of makes of cars whinh are equipped with the ' cone dutch and the number equipped with the disc clutch are. a hout equal, i he two making" about DO per cent ol the makes or" cars on the market. A cone clutch wilt be found on one of our hUtvst priced cars and also on some of the lowest priced; the same beim; true of the d isc clu tcii. Thus the question, oftn asked, as to which is the bci tcr. is di f lieu it to answer, and is entirely en-tirely a matter of the opinion of engineers. engi-neers. A jrood cone. clutch will pive little trouble, trou-ble, the same being true of a disc clutch. of the discs, so that we will get what is shown in Fig. ih Here J is the one llanse and K the other. Our next step is to supply some method of pulling or pushing these two ilang.es. (,r and K) toward one another, so as to exert a pressure between the discs. This, we know, must be done by a spring, and so, by putting a spring in the driven drum and then having a spider (Ij, Fig. T) in back of this spring, and then running run-ning bolts from this spider to the flange K, our purpose will be accomplished. In Fig. T you will notice that the spring tends to push the drum K to the riulit, and spider h to the left. As the spider h is pressed to the left, it will pull on the bolts M, and so also pull the flange Fi4. OF WW but ir" either is poorly designed or built it will give trouble, and much trouble. "We have seen the design of the cone clutch: let us now take up the design ol the disc clutch. hike the cone clutch, the disc clutch depends de-pends upon friction for its holding power. In the cone clutch the materials used have a very ki'n coefficience of friction or holding power, and I he surfaces are so shaped that there is an inclined plane or wedqe action, which will allow for a great pressure between the surfaces, with a comparatively small snrinir pressure. The clutch spring must not be too powerful, pow-erful, as drivers of little strength must be able to compress it by pushing on the foot pedal, and they must he able to hold it in t lie compressed position for gome time without becoming tired. Thus 1 lie designers of the disc clutch have the problem of designing the clutch to -give a great holdine power, with a comparatively weak spriusr. without bavins bav-ins the wedge action of the i one wiii-'h will give a leverage to the spring. 1 low can this problem be overcome? It ran be overcome hv having a number of friction surfaces, or. in other words, a number of clutches, all pressed together! by the same spring. Thus, while eam j surface will not hold enough to pull the car up a steep hill, each will hold sumo, and by havi ng from two tn twenty-one surfaces a clutch which will hold sufti-cienUy sufti-cienUy to pull t he ear up the si ee pest grade can be designed, using, a comparatively compara-tively weak spring. 1 laving decided to use a number of surfaces, let us proceed to design a multiple multi-ple disc clutch. We rind that one set of the discs will have to be driven by the engine. whilr the ot'.er set will have to drive the rear wheels (through transmission, transmis-sion, et -. ) : so let us fa s ten a drum to the i nside of which are keys, to the (1 v , wheel. This is shown in Fig. 1, In which' A is the drum and Ti the keys. We can then notch trie d Iscs hi the outside fir-r-umference so as to fit on the keys, and he s hie to siide bark a nil forth in the drum. Kis. 2 show: this novhed disc, C being the notches, or keyways. PiM'-ticallv t': e same tiling can he done with the driven member and driven dis',s i Those att:r h'"-'l ro the rear wheels through transmission. et). Thus, by fas'ning a drum on the shaft which co'-to co'-to the rear, with keys on the ouisiu'e irs: rircurnference as shown in Figs. .1 and .j. in which P is the shift, K til1 drum and F the Revs, and then having inf-rnal keyways on The d:s-s h'-j shown in Fir. 4, in which H Is ihe keyways. If we a-sern1 ; en- clutch as deignM so fur, we will 2r what is shown In Fig. .. il-re you will not ice t na t the dlM-s f2 w:d itviip with the fly wl-.el. and the dis-s Mi with the drheii shaft and dfUi -.). This is a 11 r i r. t so fa r, hi 1 1 we li ;i v e no way of compressing the d's-s. ro"-'her. so let us p-t a thmge on the drum at-rr"-bcd to the rd;a;.t T and s' ide another flange over the s..;;i't on the other hide. K to t'ne left. Thus the spring messe? the tlange J to the right, and 'flange 1C to the left, in this May pressing the discs together. We now have the clutch so that the dises will be pressed together with such force as to malic the ti y wheel and all the parts of the clutch travel together as though they were one piece. Our net problem is to arrange some means for disengaging rhe cluteh, or for taking the pressure of .the spring from ,t he diy.:s. This can be done as shown in the right of Fig. 7. Here tiie sleeve P is alt. i bed to th.e flange K, so that when it is pulled to the right I he flange also is so pulled against the action of the spring, thus t iking ik-ing the piessure oT the diss. The sleee 1 is also furnished with a tlange against which the thrust i-nilar TI can ne pressed by the yoke S, uhich yoke is operated by the fool pedal. The action of the chit-h will t'i"n be as fcl'ows: 'When the foot pedal Is up. the spring v. 11! pull the flanges J and K together sn t ho t the pissuie on the dises wiil make Ibeni revolve as thougn thev were one s-lid piec... When the ped ,1 is depi-ssvl the spring pressure" will be taken off the dises. and y only those discs kee,l to the fly wheel drum will revolve, the o:b-r porhons of the clu I eh remaining pr at uinarv. Iai;e t'ne eone cluteh. t he disc cluteh must have a nrake to stop it from spinning spin-ning when throw n out. Fv h.i vmg t ; e fla nge Q of rhe sieev p srrikf a st a -tionary disc, this braking action c.tn mui-ph- be accomplished. T shows the ch.t h brake. Vhi!o some chitehes have the discs all of steel only, most of them have ope set of discs faeed wit h smne high' friction material. su h as ravht'stos, tncrnioid, or 1 the like. Pise clutches might sa id to rnm-UT.ih'T rnm-UT.ih'T two t ypes -d r y fb- t..- a nd wet nlat. . The wot plate clutch run-' in oil. while tiie dry plate ehihh runs Hi v. To the eve there is t'tlle difOrt r.:-e between the two, t'ne dlferi-iee being in the pro-port pro-port h mi re,- of the spring, to tue n Jinbcr , of dis- s. I |