Modified Stock Gearing - Boston Gear

The Boston Gear Series 50 Tensioner is a screw-adjustable tensioner with
a spring-loaded pivot arm. The arm maintains tension on the chain and
automatically takes up the slack due to cycle loading or wear. It offers all
the advantages of the screw adjustable tensioner plus the automatic takeup
feature, which substantially reduces maintenance. The double-coil
spring is loaded by turning the adjustment screw in the base of the unit,
forcing the idler arm against the slack side of the chain.
The Series 60 Tensioner has a spring-loaded pivot arm but does not have
the screw-type adjustment. It is used in lighter applications (#35-#60 chain)
when automatic take-up is desired. Since the pivot arm must be adjusted
by hand, the mounting location of the tensioner is important.
On both the Series 50 and 60 Tensioners, the pivot arm swings 90° from
the center line in either direction, however, it must be positioned to swing
in the direction of chain travel.
Roller Chain Drive Tensioners
Type BG
Spring Adjustable
ORDER BY CATALOG NUMBER OR ITEM CODE
Suggested
Chain Number*
Available
Load at Idler
Shaft @90°
Catalog
Number
Item
Code
Series 50 dimensions
40, 50, 60 63 Lbs. 51-BG 48883
80, 100, 120 105 Lbs. 52-BG 48884
35, 40, 41 32.2 Lbs. 60-BG 48886
50, 60 33.3 Lbs. 61-BG 48887
*Single-strand chain. For multiple strand chain, use large tensioner.
G
B
L
DIRECTION
OF CHAIN
TRAVEL
M
5/16"
E
MAX.
IDLER
SHAFT
H
K
Available load at idler shaft is the maximum amount of force on the chain
developed by the spring loaded arm when deflected 90° to either side of
the neutral position.
The basic spring preload is 20% of the total capability. The load curve is a
straight line proportion of load to angle of deflection. Upon request, lighter
springs can be supplied for all units. Heavier springs (to 150% of above
capacity) can be furnished for all units except #60BG and #61BG.
Depending on application, please allow a service factor for spring capacity.
Springs are shot-peened for longer life.
ALL DIMENSIONS IN INCHES
F
MAX.
G
PIVOT
ARM
J
RAD
2G
C
A
1/4"
GREASE
FITTING
D
GREASE
PORT
COLLAR
COIL SPRING
ADJUSTING SCREW
Size A B C D E F G 2G H J K L M Wgt.
51BG 9 2 8-1/8 .875 1-3/4 2-1/2 11/32 1/2 5-3/8 4-1/4 3 1 1/2 5 Lb.
52BG 13 3 11-7/8 1.125 2-7/8 4 9/16 3/4 7-13/16 4-3/4 3-7/8 1-1/2 5/8 10 Lb.
H
Series 60 Dimensions
H
E
MAX.
F
DIRECTION OF
CHAIN TRAVEL
5/16"
COLLAR
PIVOT ARM
D
B
RAD.
IDLER
SHAFT
GREASE
PORT
K
G
C
A
J
COIL
SPRING
ALL DIMENSIONS IN INCHES
Size A B C D E F G 2G H J K L M Wgt.
60BG 4 4-3/4 3-3/8 .500 1 1-3/8 7-3/8 — 2-7/8 9/32 1/4 — — 2 Lb.
61BG 5-1/2 6 4-3/4 .875 1-3/4 1-7/8 9-1/2 — 4-1/4 13/32 5/16 — — 5 Lb.
P-1930-BG 04/10 Boston Gear 800-825-6544 295