WHEEL. 



ftould be made thinner in the middle, and fattened to the 

 fellies with nails of fuch a kind, that their heads may not 

 rife above the furface of the rim. The fellies on which the 

 rims are fixed fhould, in carriages, be three inches and a 

 quarter deep, and in waggons four inches. The naves 

 (hould be thickeft at the place where the fpokes are inferted, 

 and the holes in which the fpokes are placed (hould not be 

 bored quite through, as the greafe upon the axle-tree would 

 infinuate itfelf between the fpoke and the nave, and prevent 

 that clofe adhefion which is neceffary to the ftrength of the 

 wheel. 



The track in which the wheels of every carriage are to 

 run is generally the fame, except when intended for par- 

 ticular roads, where waggons and other heavy carriages are 

 principally ufed, and leave very deep ruts, in which hght 

 carriages mud likewife run, or be liable to accident, and are 

 alfo fare to be heavy in draught. All four-wheel carriages 

 (hould have the hind and fore wheels regulated to roll in the 

 fame track. The ordinary width of the wheels is four feet 

 eight or ten inches ; that of waggons or carts generally mea- 

 fure five feet two inches ; chaife-wheels, as being princi- 

 pally intended for the country, are adapted to this width. 

 It is immaterial to what width wheels are fet if ufed for run- 

 ning upon ftoncs ; but on marfhy roads, if their exaAnefs is 

 not attended to, the draught is confiderably increafed. We 

 have feen a carriage of which the iron axle-tree is made in 

 two pieces, overlapping each other in the middle where they 

 are joined, and fccured by proper bands to the wood-work of 

 the carriage, fo as to admit of Aiding in the direction of the 

 axle-tree. Thefe parts are cut with teeth like racks, and a 

 pinion is applied between them ; fo that by turning this pinion 

 round, the two parts of the axle-tree are made to Aide one 

 upon the other ; and the wheels which are fitted upon the two 

 extreme ends of the axle-tree can at pleafure be fixed at 

 greater or lefs diftance, as the roads require. 



The different heights'of hind and fore wheels make alfo a 

 difference in the length of their axle-trees, agreeable to 

 the proportion they bear to one another ; the fore-wheel 

 has the longed axle-tree by one or two inches between the 

 fhoulders. 



The nave of the wheel is pierced through the centre, with 

 a large hole to introduce the box, or iron tube, for the axle- 

 arm, as this tends to weaken the wood. It has been fre- 

 quently propofed to make metal naves, or centre-pieces for 

 wheels, which (hould contain the box for the axis, and the 

 mortifes for the fpokes of the wheel all caft of one piece of 

 metal. Meffrs. Dodfon and Skidmore had a patent for this 

 in 1799. The objeftion toitis, that.if thewoodof thefpokes 

 (hrinks, they become loofe in the mortifes, whereas a wooden 

 nave (brinks at the fame time with the fpoke. This defeft 

 has been fince remedied by making the metal wheel-ftock 

 in two parts ; one with receffes, or fockets, to contain the 

 fpokes, and the other a flat plate to fatten againll the former 

 with fcrew-bolts, and prefs the fpokes into their cavities. 

 Mr. Plucknet had a patent for a metal wheel-ftock of this 

 kind in 1805, which anfwered extremely well for carts, 

 waggons, and artillery. The fpokes were made to fill up 

 all the fpace in the nave or (lock, fo that each fpoke touched 

 its neighbour. The metal ftock was only a flat circular plate, 

 or flanch, projefting from the box which received the axle, 

 and another flat plate fitted upon it, and bound againft the 

 former by fcrew-bolts, one palling through each arm ; thefe 

 rendered the wheel very ftrong. 



Mr. Wilks took a patent in i 8 1 3 for a metal ftock, in which 

 there are complete cells for each fpoke, and the cells are 

 dove-tailed ; that is, they are made larger at the central part 

 than at tiie outfide, to prevent them from drawing out, and 



9 



they are firmly preffed into the dove-tails by the fcrew-bolts 

 which confine the moveable plate. 



Wheels for railway-waggons are made of caft-iron, and 

 iifually all in one piece ; but this is objeftionable, becaufe 

 the unequal contraftion of the arms and rim of the wheel in 

 cooling, after the wheel is caft, puts the different parts on a 

 ftrain, and they frequently break without any adequate 

 force. It is better to caft the rim in one piece and the arms 

 in another, and put them together with fcrew-bolts, or rivats. 

 Mr. Hawks had a patent for this in 1807. In this way, the 

 rims may be replaced when worn out. 



The Axle-trees for Wheels of Carriages. — The ftrong iron 

 bar which extends acrofs beneath the wood-work of the 

 carriage, is called the axle-tree ; the round parts at each 

 end, on which the wheels run, are called the axle-arms ; and 

 the part or item between them, which is fixed beneath the 

 wood-work of the carriage, is alfo called the axle-tree. In 

 the form of the latter parts there are but two forts, the 

 one made flat, and called a bedded axle-tree, it being 

 funk all its length in the under fide of the timbers of 

 the carriage ; the other is made of an o^agon form, and flat 

 only at the ends where they are bedded. 



The axle-arms on which the wheels turn (hould be made 

 perfeftly round, and fomewhat ftronger at the fhoulder than 

 at the extreme end, which is fcrewed to receive a nut, 

 through which and the axle-tree the linch-pin paffes, to keep 

 all tight. The nuts are made with a collar at the face ; and 

 a temporary collar, or wafher, is driven on the back of the 

 arms, which form two (boulders for the wheel to wear 

 againft, and helps to preferve the greafe from running out, 

 and to prevent dirt from getting in. 



As the axle-trees are the principal or only fupport of the 

 carriage, every attention and care (hould be fixed in the 

 feleftion of good iron ; and to fee that they be well wrought, 

 and of fufficient ftrength, rather going to the extreme of 

 ftrength, than ri(]<ing the life of the paffenger by the over- 

 fetting of the carriage, which moftly happens when an axle- 

 tree breaks. 



By the bend of the axle-trees, the wheels are regulated to 

 any width at bottom, to fuit the track of the roads in which 

 they are to run, and are confined in the carriage by means 

 of chps, hoops, and bolts. The (hape of the axle-tree be- 

 tween the (houlders varies according to the fituation they 

 are placed in, or the form of the timber of the carriage with 

 which they are united ; thofe are the moft firm that are flat, 

 bedded in the timber. Axle-tree boxes for wheels are of 

 various kinds ; thofe which are frequently called long-pipe, 

 or wheel-boxes, are long tubes fitted accurately to the arms 

 of the axle-trees, and fecurely fixed in the wheel-ftocks, or 

 naves; they are ufually made of wrought ftieet-iron of afub- 

 ftance proportioned to the weight of the carriage ; their ufe 

 is to contain a fupply of greafe, and to prevent the effefts of 

 friftion, whereby the wheels are much affifted in their mo- 

 tion. Thefe are now ufedinftead of the old caft-iron boxes, 

 which for quick travelling-carriages are totally out of ufe, 

 being found injurious to the axle-trees, by cutting them at 

 thofe parts they wear againft, fo as to occafion a frequent 

 lining of the arms ; but with the wrought metal boxes this 

 is feldom neceflary. 



There are many forts of axle-trees and boxes invented 

 various ways, with a view of attaining the following ad- 

 vantages ; viz.. To contain a longer fupply of greafe or 

 oil, to be more durable, to fecure the wheels, and to lefTen 

 the draught. Thofe are all certainly great advantages, 

 and though the expence is great, the utihty of either of 

 ihem mutt be more than adequate to it, and merits more 

 general notice. 



Some 



