• In certain applications it is advantageous to curve tracks either horizontally (‘A’ Curve) or vertically (‘B’ Curve).
  • Curved track may be needed to give a traveller car a required path of movement or to match the mounting surface to which it is fixed. It can also ensure maximum performance is obtained from a traveller car by ensuring load and connection remain vertical. Or that tension in an attached purchase system or linkage remains constant.

HORIZONTAL PLANE - 'A' BEND

In situations where cars and fittings are required to rotate around a central pivot point, horizontal ‘A’ curving of the track will ensure the load applied to the car remains vertical. This results in maximum strength and free rolling ability being maintained by the car. Maintaining this vertical alignment also ensures tension in an attached purchase system remains constant, a feature often sought after in sailboat mainsheet and boom vang traveller systems.

VERTICAL PLANE - 'B' BEND

Traveller tracks can be curved vertically to fulfill certain requirements.
They can be top mounted or underhung mounted with either concave or convex track curves.
‘B’ Curves are often required to match the mounting surface to which a track is to be fixed; as when matching deck camber on a sailboat.
‘B’ curving can also be used to maintain constant tension in a rotating purchase system mounted on a traveller car. This application is very popular on sailboat mainsheet and self-tacking jib systems where the increased load applied to the car during tacking or gybing may affect sail trim or cause the car to stick.

CURVED TRACK SPECIFICATION REQUIREMENTS

Specifications are required for each type of curve, including two critical dimensions (three if possible), and clear drawings where possible.

Critical Dimension Required

Radius R and Offset O
OR
Radius R and Length of track L
OR
Radius R and Chord Length C
OR
Offset O and Chord Length C

In many ‘B’ curve situations, the radius R is not known and it is easiest to specify the curve by C (chord length) and O (offset) values. In these cases, the radius the track is to follow MUST be constant.

MINIMUM BEND RADIUS

TRAVELLER SERIES CAR LENGTH MIN. HORIZONTAL
"A" CURVE RADIUS
MIN. VERTICAL
"B" CURVE RADIUS
  mm (in.) mm (in.) mm (in.)
BALL BEARING            
SERIES 14 47 (1 27/32)  1300 (51 7/32) 800 (31 17/32)
  68 (2 11/16) 2000 (78 13/16) 2000 (78 13/16)
  78 (3 1/16) 3500 (137 29/32) 4500 (177 5/16)
             
SERIES 19 50 (1 31/32) 1500 (59 3/32) 1500 (59 3/32)
  57 (2 1/4) 1500 (59 3/32) 1500 (59 3/32)
  70 (2 3/4) 2500 98 1/2) 3000 (118 3/16)
  85 (3 11/32) 3500 (137 29/32) 4500 (177 5/16)
  100 (3 15?16) 5000 (197) 5500 (216 11/16)
  148 (5 27/32) 11000 (433 13/32) 15000 (591)
SERIES 22 60 (2 3/8) 1500 (59 3/32) 1500 (59 3/32)
  75 (2 31/32) 1500 59 3/32) 2000 (78 13/16)
  125 (4 15/16) 5000 (197) 5000 (197)
  130 (5 1/8) 5000 (197) 5000 (197)
  165 (6 1/2) 7000 (275 13/16) 7500 (295 1/2)
  175 (6 29/32) 9000 (354 19/32) 13000 (512 3/16)
  180 (7 3/32) 9000 (354 19/32) 13000 512 3/16)
             
SERIES 26  120 (4 23/32) 4000 (157 19/32) 4000 (157 19/32)
  180 (7 3/32) 8000 (315 3/16) 8000 (315 3/16)
  200 (7 7/8) 8000 (315 3/16) 8000 (315 3/16)
  205 (2 1/16) 9000 (354 19/32) 9000 (354 19/32)
             
             
SERIES 30 77  (3 1/16) 2500 (98 1/2) 2500 (98 1/2)
  100 (3 15/16) 2500 (98 1/2) 2500 (98 1/2)
  150 (5 29/32) 8000 (315 3/16) 8000 (315 3/16)
  165 (6 1/2) 8500 (334 29/32) 8500 (334 29/32)
  175 (6 29/32) 9000 (354 19/32) 9000 (354 19/32)
  185 (7 9/32) 9300 (366 13/32) 9300 (366 13/32)
  200 (7 7/8) 10000 (394) 10000 (394)
  215 (8 15/32) 11000 (433 13/32) 11000 (433 13/32)
  225 (8 7/8) 16000 (630 13/32) 16000 (630 13/32)
  230 (9 1/16) 16500 (650 3/32) 16500 (650 3/32)
  300 (11 13/16) 15000 (591) 15000 (591)
  375 (14 25/32) 18000 (709 3/16) 18000 (709 3/16)
Please contact our sales team for minimum bend radius requirements for Series 42 and 55 traveller cars
-
I-BEAM            
SERIES 19 51  (2) 400 (15 3/4) 400 (15 3/4)
   86 (3 3/8) 1200 (47 1/4) 1200 (47 1/4)
  106 (4 3/16) 400 (15 3/4) 400 (15 3/4)
             
I-BEAM            
SERIES 32 76 (3) 600 (24) 500 (20)
  157 (6 1/5) 600 (24) Not Suitable Not Suitable
             

It should be noted that:

  • Although track curves may appear desirable to provide ideal alignment and avoid angular loads being applied to the car, in a ball bearing system this same curve will actually reduce the load capacity of the system by loading the balls unevenly throughout the length of the car.
  • Not all track types are suited to both types of curves, and some tracks cannot be curved at all.
  • A minimum track radius is specified for each length of traveller car. This is the tightest curve a car will run around freely. Refer to the recommendation table above for each track type regarding suitability and minimum radius values.
  • Light curves can be ‘sprung in’ sometimes when mounting track, however considerable care must be taken to ensure that the curves are even with no tight spots and that the track is not kinked (permanently deformed) during installation. For the best results, track should be ordered pre-curved from Ronstan.

Ordering

  1. Specify the type of track profile (by product no.)
  2. The type of curve required ‘A’ Curve (horizontal) or ‘B’ Curve (vertical) Concave or Convex.
  3. Provide the appropriate dimensional specifications as described above.