Bellcranks Made in the USA

Our bellcranks are designed to provide an assembly that will not flex or bend while in use, and still be compact and light in weight. A ridged bellcrank is very essential to prevent control surface flutter on larger and high speed R/C aircraft. Our new unique single truss design places all the linkage movements on a central axis thereby reducing torsional moments which can lead to control surface flutter at high speeds.

L350B 3 1/2" 180° double ball bearing bellcrank. Two ball bearings are utilized. A 3/16" bolt securely attaches the bellcrank to the mounting structure in the aircraft.

The bellcrank arm is manufactured from aircraft quality 2024T-3 1/16” thick aluminum. The arm and bearing holder are also plated for durability and appearance. Two precision ball bearings and heavy duty 4-40 ball links provide the user with an durable, low friction bellcrank. Subminiature 2-56 and 4-40 elastic stop nuts with phillips head screws are used to assemble the unit. A sturdy 3/16” cap screw with an elastic stop nut attaches the unit to a suitable customer supplied plywood attach plate.

32 Parts make up the bellcrank assembly. Two ball bearings are used to assure minimum friction. Bearing holder is an accurately CNC machine unit. Subminiature elastic stop nuts are employed to keep unit securely assembled.

The NELSON ball bearing bellcranks are first class units suitable for any sport or competitive aircraft.

60 and 90 degree bellcranks are available. These bellcranks are commonly used for aileron control systems. The lever arm (legs or size) is 1 1/4 inches on each side. Two sets of output holes are provided. Additional holes can be drilled as required.

L125B-90 90° Bellcrank with ball link attach points of 1 1/4" and 1". Supplied with two ball links.

The 180 degree bellcranks are typically used for pull-pull cable applications. Instead of using a single pushrod to drive the rudder or any other control surface, two parallel light weight stainless steel cables are used to operate control systems. Pull-pull systems on the rudder are quite common. The bellcrank will be normally located near the servo which is typically located in the fuselage area under the wing. A short 4-40 threaded rod pushrod provides the linkage from the servo to the bellcrank. Many times two pushrods are used.

An advantage of using a 180 degree bellcrank instead of using a double output arm on the servo, is to eliminate the problem of keeping the pull-pull cable tight. If the cables are tightened too much, the cables will pull the servo against the mounting grommets. One can never really tighten the cables properly. With the 180 degree ball bearing bellcrank used as an idler bellcrank, one can tighten the cables without causing the servo to move and still keep the friction on the bellcrank pivot point to a minimum.

Another reason for using a 180 degree bellcrank is to relocate a pushrod away from the direct position of the servo. In some applications it is not practical to locate the servo in-line with the pushrod. Having the servo located elsewhere can solve the problem. A short pushrod would go from the servo to one end of the 180 degree bellcrank. The opposite end of the bellcrank is where the regular pushrod is attached.

Any of the 180 degree bellcranks can be used to reduce or increase linkage travel. Another application would be to break a pushrod into two short lengths instead of one long length. In this situation the bellcrank would be in between the control arm and the servo.

L400B375 Offset bellcrank is 4" wide and has an offset of 3/8". The offset will provide for a pull-pull cable system that maintains proper cable tension regardless of control travel deflection. Many different offsets amounts are available to fit the individual aircraft requirement. Custom offsets available as well.

The offset series of bellcranks (for example the L400B375 unit shown above) are used when the rudder control horn pull-pull cable fitting attach points are not lined up on the center line of the hinge. Sometimes it is not practical to have the attach point on the hinge center line. This is especially so with thick rudders found on 1/3 to 40% size aircraft that are using the 8-32 screw swivel type rudder horn units.

The correct offset bellcrank will be one that has the same offset from the rudder horn cable attach pivot point to the hinge line of the rudder. This offset distance is duplicated on the offset bellcrank. The correct offset will provide for a smooth working pull-pull rudder system that will maintain correct cable tension regardless of the amount of the rudder deflection.

Several sizes of offset bellcranks of are offered. Offset distances are available from 1/4” to 3/4” and in widths from 3” to 5”. Custom bellcranks are available on special order.

 

NELSON Ball Bearing Bellcranks
ITEM NO.	DESCRIPTION	QTY. PKG.	PRICE
180° (Double) Standard Bellcranks
L220B	2 " 180° Bellcrank	1	$22.95
L225B	2 1/4" 180° Bellcrank	1	$22.95
L250B	2 1/2" 180° Bellcrank	1	$22.95
L275B	2 3/4" 180° Bellcrank	1	$22.95
L300B	3" 180° Bellcrank	1	$22.95
L325B	3 1/4" 180° Bellcrank	1	$22.95
L350B	3 1/2" 180° Bellcrank	1	$22.95
L375B	3 3/4" 180° Bellcrank	1	$22.95
L393B	3 15/16" 180° Bellcrank	1	$23.95
L400B	4" 180° Bellcrank	1	$23.95
L420B	4.2" 180° Bellcrank	1	$23.95
L425B	4 1/4" 180° Bellcrank	1	$23.95
L450B	4 1/2" 180° Bellcrank	1	$23.95
L475B	4 3/4" 180° Bellcrank	1	$23.95
L500B	5" 180° Bellcrank	1	$23.95
L550B	5 1/2" 180° Bellcrank	1	$24.95
L600B	6" 180° Bellcrank	1	$24.95

 

NELSON Ball Bearing Bellcranks
ITEM NO.	DESCRIPTION	QTY. PKG.	PRICE
180° Offset Bellcranks
L250B250	2 1/2" Bellcrank with 1/4" offset	1	$23.95
L250B375	2 1/2" Bellcrank with 3/8" offset	1	$23.95
L300B250	3" Bellcrank with 1/4" offset	1	$23.95
L300B375	3" Bellcrank with 3/8" offset	1	$23.95
L300B500	3" Bellcrank with 1/2" offset	1	$23.95
L350B250	3 1/2" Bellcrank with 1/4" offset	1	$23.95
L350B375	3 1/2" Bellcrank with 3/8" offset	1	$23.95
L350B500	3 1/2" Bellcrank with 1/2" offset	1	$23.95
L375B250	3 3/4" Bellcrank with 1/4"offset	1	$23.95
L375B375	3 3/4" Bellcrank with 3/8"offset	1	$23.95
L375B500	3 3/4" Bellcrank with 1/2"offset	1	$23.95
L375B625	3 3/4" Bellcrank with 5/8"offset	1	$23.95
L400B250	4" Bellcrank with 1/4" offset	1	$24.95
L400B375	4" Bellcrank with 3/8" offset	1	$24.95
L400B437	4" Bellcrank with 7/16" offset	1	$24.95
L400B500	4" Bellcrank with1/2" offset	1	$24.95
L400B562	4" Bellcrank with 9/16" offset	1	$24.95
L400B625	4" Bellcrank with5/8" offset	1	$24.95
L450B375	4 1/2" Bellcrank with 3/8" offset	1	$25.95
L450B437	4" Bellcrank with 7/16" offset	1	$25.95
L450B500	4" Bellcrank with 1/2" offset	1	$25.95
L450B562	4" Bellcrank with 9/16" offset	1	$25.95
L450B625	4" Bellcrank with 5/8" offset	1	$25.95
L500B375	5" Bellcrank with 3/8" offset	1	$25.95
L500B437	5" Bellcrank with 9/16" offset	1	$25.95
L500B500	5" Bellcrank with 1/2" offset	1	$25.95
L500B562	5" Bellcrank with 9/16" offset	1	$25.95
L500B625	5" Bellcrank with 5/8" offset	1	$25.95
L550B375	5 1/2" Bellcrank with 3/8" offset	1	$25.95
L600B375	6" Bellcrank with 3/8" offset	1	$26.95

 

NELSON Ball Bearing Bellcranks
ITEM NO.	DESCRIPTION	QTY. PKG.	PRICE
Angle Bellcranks
L125B-45	1 1/4 " 45° Bellcrank with 1 1/4" Arm	1	$20.95
L125B-60	1 1/4 " 60° Bellcrank with 1 1/4" Arm	1	$20.95
L125B-90	1 1/4 " 60° Bellcrank with 1 1/4" Arm	1	$20.95
L125B-135	1 1/4 " 135° Bellcrank with 1 1/4" Arm	1	$20.95
L125B-150	1 1/4 " 150° Bellcrank with 1 1/4" Arm	1	$20.95

 

Revised 3/24/04

Our ball bearing bellcranks are available from

NELSON Hobby Direct or at hobby dealers.