WHEEL TRAINS 391 
due to throwing the tumbler gear in is diminished. The particular 
example illustrated in Fig. 609 is from a radial drilling machine by the 
Bickford Drill and Tool Co. of Cincinnati. The gear shown is placed on 
the base of the machine, and the shaft H drives a vertical shaft in the 
pillar through bevel wheels. 
332. Epicyclic Wheel Trains.—In an ordinary wheel train the axes 
of the wheels are fixed, while in an epicyclic 
train at least one axis revolves about another axis a A 
which is fixed. aie k 
The first point about an epicyclic train to  -~% “4-}- x 
be thoroughly understood is that if a wheel B ‘3 Se) ae )1 
(Fig. 610) be attached rigidly to an arm EF, and ¥ ‘¥-77- 18 
the arm is made to rotate once about an axis 
at E, the wheel B will turn once on its own axis 
in the same direction in which the arm rotates. A 
This is made clear by an inspection of Fig. 610, 
where the arm and wheel are shown in four differ- 
ent positions during one revolution. The arrow on the wheel is 
supposed to be fixed to it. 
_ Examples of epicyclic trains are shown in Figs. 611 to 616. In each 
of these examples A is the first, and L the last wheel of the train, and 
ai Ne 2 ek 
¢ 4 Sw ab 
! 4 om 
‘ Gy: ‘ 
‘ Bove = 1 
Se Sat ; 
Ba. ' 
phe =, * ie? 
OT TT — 
 — ree MT a nnn MU L 
E = —— F aM YT NO ULE 
UL UT | SS 
= = L D 
Fig. 611. Fig. 612. Fig. 613. 
EF is an arm carrying certain of the wheels and rotating about an axis 
CD. The arm may be straight, as in Figs. 611 and 612, or bent, as in 
Fig. 613. In Fig. 615 the arm 
takes the form of a spur wheel. 
In Figs. 614 and 615 the axes of 
the first and last wheels of the 
train coincide, and these trains are 
called reverted wheel trains. 
' The gear shown in Fig. 615 
is the well-known differential gear ¢ 
used on the driving axles of 
motor cars to permit of the : 
driving wheels rotating at different =, g14 Fic. 615 
speeds in going round a curve. > gy : ba 
The driving axle CD is divided, the part C carrying one driving wheel 
and D the other. The wheels A and L are fixed to C and D respectively, 
and the wheel EF is driven by the engine. 
