HARDWOOD RECORD 



31 



Cedar 218.000 



Chestnut 200.000 



Hemlock 20.".000 



Elm 140.000 



Cottonwood 101.000 



Walnut 32,000 



Sycnmoie 2S,U00 



Beech IS.OOO 



Birch 2.000 



All others 101,000 



Total 584,872,000 



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Protecting Ties Against Wear 



Editor's Note 



At the annual mivtiu;; of the .Viuerieaii Wood I'reserveis' Association at New urkaus January 20-22. the 

 following paper enlitliKl. 'The I'rotection of Tics from Mechanical Destruction. " was read by Howard P. Weiss. 

 director of the Forest Products Laboratory at Madison, Wis. Pictures, diagrams and tables are omitted. 



In 1907 the American Railway Engineering Association sent 

 out a number of letters asking various railroad engineers what 

 per cent of their ties failed from decay and what per cent from 

 mechanical destruction. The replies in general were that about 

 ninety per cent of oak ties failed because of decay, as against 

 twenty-five per cent of cedar. In other words, the mechanical destruc- 

 tion of the ties varied from a minimum of about ten per cent for 

 oak to a maximum of about seventy-five per cent for cedar. The 

 many good results which have been and are being secured by tim- 

 ber treating engineers in protecting ties from decay are placing 

 each year a larger per cent of our ties in the cedar class in so 

 far as their mechanical life is concerned. This means that the 

 problem of mechanical protection is one of increasing importance. 

 It is a waste of preservative, effort and money to inject into ties 

 an amount of preservative which will protect ties beyond their 

 mechanical life because after the tie has once failed mechanically 

 it is removed from the track and destroyed. With costly treat- 

 ments, particularly such as are given by the full-cell creosote 

 process, this problem is of immense importance to railroads, as it 

 may mean a waste of hundreds of thousands of dollars yearly. If 

 the tonnage of the road is light, as with many traction com- 

 panies, the arguments here advanced for tie plating and more 

 expensive fastenings are not of such immediate importance. In 

 fact, in such cases it may often prove inadvisable to tie plate, 

 especially if the ties are made of a hard wood. In this paper I 

 wish to discuss briefly the protection of ties from mechanical 

 sauses of failure and will not go into the subject further than to 

 indicate certain points of interest to timber treating and railroad 

 engineers. By the mechanical destruction of ties I mean rail wear 

 and spike cutting. 



The protection of ties from rail wear is secured bj' means of tie 

 plates. These serve two primary functions: (1) The protection 

 of the tie from the crushing and pounding action of the rail due 

 to the passage of rolling stock; and (2) the protection of the tie 

 from the grinding action of the rail caused by its tendency to 

 creep and vibrate. 



A great variety of plates has been advocated to protect ties 

 from destruction. They may be classed, however, as wood and 

 metal plates. The former are rather extensively used abroad, and 

 are also under test in this country. From the experience which 

 we have had with then in different test tracks laid in co-operation 

 with American roads, the results have not thus far been satis- 

 factory. Wood plates offer little or no reinforcement to spikes 

 when these are subjected to a lateral thrust; consequently, spikes 

 are more likely to bend and rail spreading is likely to occur. Fur- 

 thermore, the plates often tend to work loose from under the rail 

 and if spikes are driven through thom they split badly. In some 

 of our tests, where wood plates were attached to the ties, they 

 actually became imbedded in the ties. If the tie is slotted so 

 that the plate can be inserted in such a manner that its upper 

 surface will be level with the top of the tie many of these ob- 

 jections are overcome, but this method of treatment increases the 

 cost of preparing ties for service and also weakens them. 



More satisfactory results have thus far been secured, in our ex- 

 periments at least, with metal plates. These vary considerably in 



form, but may be classed into two tj'pes, viz., pronged or ridged 

 plates and flat plates. The object of the former class is to imbed 

 the plate in the tie, thus making it a part of the tie and assisting 

 the spikes in resisting rail spread. The chief disadvantage we 

 have noted to this type of plate is its tendency to gouge into the 

 wood and at times completely destroy it. The untreated interior 

 of the ties is thus exposed to the weather and decay is readily 

 admitted. Flat plates do not have this objection, but are trouble- 

 some at times in that they become loose and rattle under the rail. 

 Furthermore, they simply rest upon the tie and offer no reinforce- 

 ment to the spike against lateral thrust. 



A feature in tie-plate construction which has perhaps not been 

 given the serious attention to which it is entitled is the size of 

 plate for the kind of tie on which it is to be placed. A light, 

 small tie-plate is of little or no value in protecting the tie from 

 destruction. It is necessary to have the plate of sufficient surface 

 area so that the crushing action of the rail will be distributed as 

 widely as possible, and to have sufficient thickness, so that no 

 buckling will occur. As is generally known, the various woods 

 which are now manufactured into crossties differ very appreciably 

 in hardness and in crushing strength. Cedar, loblolly pine, etc., 

 are considerably weaker than black locust and white oak. for ex- 

 ample. If cedar ties are interspersed in a track with white oak 

 ties and the same sized tie-plates are placed upon both, the cedar 

 ties are going to fail from mechanical destruction far more quickly 

 than the white oak ties. That track is best laid which makes each 

 tie carry its proportionate share of a passing load; therefore, to 

 secure best result, tie-plates should be so designed that the unit 

 loads placed on various kinds of ties will be approximately the 

 same. Perhaps best results are secured by placing in the track ties 

 .of uniform hardness, at least in given stretches. 



The Forest Products Laboratory has made over 2,000 tests on 

 about seventy species of timber to determine their resistance to 

 crushing when the force is applied at right angles to the grain 

 as in the case of crossties. 



I have taken as my standard for comparison with other woods a 

 white oak tie. A number of woods are stronger than white oak, 

 and hence the size of tie-plate which they would require would be 

 smaller than that required by white oak. On the other hand, 

 most of the ties have a less crushing resistance than the standard 

 white oak tie, and for this reason require larger plates. There is 

 a fixed relation between the specific gravity or dry weight of the 

 wood and its strength; in other words, woods which are light in 

 weight are low in crushing resistance, while woods heavy in weight 

 offer considerable resistance to crushing. It might be claimed 

 that this property of hardness or strength should be considered in 

 fixing the price of crossties; that is, ties which have a low crush- 

 ing strength, and which consequently require a large-sized tie- 

 plate in order to be protected from mechanical destruction, should, 

 other things being equal, sell at a lower price in an untreated con- 

 dition than similar ties which are heavier and which offer greater 

 resistance to mechanical destruction. If this principle were car- 

 ried out in practice it would result in some cases in a readjust- 

 ment of tie-plates. It is felt that such a readjustment is war- 

 ranted from the standpoint of efficient track maintenance. 



