DETAILS OF (PADDLE-WHEEL)
230
turned periphery of the disc. It will benoticed that a projection is formed with thedisc on one side, and a wrought iron sepa-rate portion secured on the other, by whichmeans the ring is retained on its bear-ing—an enlarged section of the connectionbeing shown between the elevations. Thecrank pin—flattened at the sides—is held inits bearing by a separate brass bush, having aflange and eight screw pins to secure the sameto the ring. At the opposite side a separatering is similarly secured : an enlarged sectionof this is also shown between the elevations.
The means adopted to fix the ring on thedisc is by keys, located below the crankpin; each key being retained in its bearingby studs—shown by the enlarged section. Towithdraw these keys, the nuts are removed,and wedges driven in under the gib endscause the keys to loosen, when their removalcan be readily effected. The ring can thenrevolve independently of the disc, and thusboth are separated. It is obvious from thisde cription, that the cranks are disengagedsimply by the withdrawal of the disc keys,—the connection of the cranks by their in-sertion ; and such is the efficiency of thismode, that it has become universal.
The dimensions of the details under noticebeing worthy of due attention, the followingcompilation is given from a late example inactual practice :—
Ft. In.
Radius of Crank Pin Circle
. 2
3
Diameter of Crank Pin
. 0
8i
. 1
0J
Thickness of Boss for Shaft
. 0
2£
Length of Boss
. 0
Hi
Diameter of Disc .
. 3
2|
Width of ditto
. 0
7
Depth of Projection
. 0
A3
u- 8 -
Width of Bing
Ft. In.
. 0 2f
Radius of Boss for Crank Pin .
. 0
8
Radius of Connecting Curve
. 3
0
Diameter of Bush .
. 0
H
Width of Shaft Keys
. 0
2*
Thickness of ditto
. 0
Width of Disk Keys
. 0
2
Thickness of ditto .
. 0
1
Diameter of Bush Pins
. 0
0i
Diameter of Ring Pins .
. 0
0.1
As the crank is in immediate
connection
with the above, the following is added :—
Diameter of Crank Boss .
Ft. In.
. 1 71
Width of ditto
. 0 in
Diameter of Pin Boss
• 1 21
Width of ditto
. 0 91
Maximum width of Web .
. 1 2
Minimum ditto
. 0 10}
Thickness of Web .
. 0 6f
Width of Pin Key (across kxs)
. 0 21
Thickness of ditto .
• • 0 li
These dimensions, and the illustration of the
disconnecting ring and disc, are in commonwith the piston rod and piston, alreadyalluded to in pages 227, 228, and 229.
In some instances the crank pin is separatedand connected by a link or loop, and in suchcases, when disengaging is requisite, one ofthe crank pins must be withdrawn. Toobviate this latter cause, we have designed aconnection, illustrated by Fig. 61—page 231.With this example, the connection is attainedby a strap, gib, and cotter, or if not alike themin general design, the principle is the same.The disengaging of the detail is effected byfirst knocking out the key and withdrawingthe strap. Secondly, the paddle-shaft crank isallowed to pass from the loose or interveningportion between it and the pin. Thirdly, theremoval of the portion mentioned permitsthe crank pin to be entirely free from theremaining portion of the crank.