Popular Science Monthly 



(J05 



Loading Small Luggage on the 



Outside of the Car 

 CONVENIKXT ••carry-ail" may he 

 constructed in the followint; man- 

 ner and attached to any automohile. 

 Obtain two strips of board i-in. thick and 

 2-in. wide and cut them to the shape of 

 the front and back fenders respectiveh'. 



N 



The carry-all takes up the space on the 

 running board on the left of the car 



Then purchase 20 ft. of blind stop and 

 from that make a frame as indicated 

 by the dotted lines in the illustration. 

 This frame should be covered with black 

 fiber board on the outside. 



Drill six H-'m. holes through the frame 

 and then holding the frame up to the 

 proper position on the car, drill corres- 

 ponding holes in the shoulders on the 

 fenders and running boards on the left- 

 hand sidcof the car. This leaves the "side- 

 walk" side of the car free for entrance. 

 The holes are practically invisible when 

 the ■•carry-all" is removed. Six 3 i6-in. 

 stove bolts 2 in. long with split washers 

 complete the device which gives sufficient 

 room to store luggage. Camp equipment 

 for ten people can be carried without 

 loading the inside of the car. 



A black oilcloth tucked in over the 

 equipment keeps rain and dust from the 

 contents and takes away the "bag and 

 beiggage" appearance. It requires only 

 five minutes to take off or put on the frame. 



Its cost is as follows: 



2 curved pieces and blind stop. . S.40 



Covering by trunk maker i.oo 



6 stove bolts 05 



Total $1.45 



It takes about two hours to make it. 

 The entire contrivance can scarcely be 

 noticed at a short distance from the 

 automobile. A large quantity of dutTel 

 can be carried in it where it may be 

 easil\- obtained when wanted. 



How Piston-Ring Defects Have 

 Been Overcome 



THE highly successful behavior of 

 the average autoniotjile and motor- 

 boat engine is due in large degree to the 

 present state of development of the 

 piston-ring. The function of the piston- 

 ring is to form a vapor-tight chamber in 

 which gas may explcxie. impounding its 

 freed energy upon the i)iston-head which 

 transmits this energy to the working 

 parts of the engine. It is evident that 

 the piston-rings must be as vapor-tight 

 as it is possible to make them. 



The earliest type of piston-ring was 

 round, of the same thickness throughout, 

 and was slotted to allow for expansion 

 and contraction of the engine as it be- 

 came hot or cold. The concentric ring 

 was soon followed by the eccentric ring. 

 The eccentric ring had a slot similar to 

 the concentric type, but it overcame, one 

 of the defects of the older type — an un- 

 equal distribution of friction against the 

 cylinder-wall. This was accomplished 

 by tapering the thickness of the ring to 

 the point at which the slot was cut. In 

 overcoming the defects of the concen- 

 tric ring, however, the eccentric ring 

 acquired disiidvantages almost as unde- 

 sirable. One of these was that the un- 

 equal thickness of parts of the ring caused 

 carbon to collect in the grooves on the 

 piston-head into 

 which the rings 

 fitted. The great 

 disadvantage of 

 both these types 

 of ring was their 

 loss of energy, 

 which resulted in 

 their inefficiency. 

 High compres- 

 sion was i m - 

 possible, as the 

 gas would escape rapidK- into the crank 

 case below the cylinder. This defect, 

 together with the undesirable features of 

 the two types of rings, has been over- 

 come in a new ring that is now in use. 

 Two of the eccentric-type rings are 

 grooved in such a way that they fit each 

 other perfectly. Vapor cannot escape 

 through cither slot because a thin steel 

 wall pre\ents it. Consequently, while 

 the compression is high, the friction is 

 ecjually clistributed and the wear reduced. 



The rings are grooved 

 to fit perfectly 



