Dynaflex LCR Selection Guide, Torsional Flexibility, Example, Recommended Misalignment Limits

DYNAFLEX ELASTOMERIC FLEXIBLE COUPLINGS Page 100 of 124

Selection Guide

Compression bushing-type couplings are assembled by pressing the elastomeric bushings into sockets of a coupling fl ange. Once assembled, the coupling can be used two ways:

•Parallel Arrangement

The driving shaft can be connected to all of the bush- ings, and the driven shaft connected to the coupling fl ange. This arrangement loads all bushings in parallel and produces maximum torque capacity and a less resilient coupling.

•Series Arrangement

This arrangement requires an even number of bush- ings per fl ange. Mating fl anges of the driving and driven shafts are attached to alternate bushings. This arrangement transmits the torque through the bush- ings in an N x N series arrangement, thereby making the torque capacity one-half of the parallel arrange- ment. The coupling is also more fl exible.

When high torque and small space are the control- ling factors, the parallel arrangement is recommended. When misalignment is the controlling factor, the bushings should be applied in series arrangement.

Table 1 provides selection criteria for parallel arrange- ment, Table 2 provides data for the series arrangement. Bushing selection is dependent upon torque require- ments, angular, parallel and axial misalignments, as well as bolt circle diameter, number of bushings and bushing size. The torque values shown on the charts are nominal. The bushings are capable of withstanding higher torques due to the shock loads or other short duration surges.

Torsional Flexibility

Bushing-type couplings are relatively stiff torsionally compared to other elastomeric couplings. The torsional spring rate of a coupling assembly can be calculated by using the equation and data provided on the curves.

Example

Required torque capacity – 3400 lb-in

Misalignment – Angular – 1.75°

Axial – 1/8 in

Parallel – 1/32 in

Proposed Coupling – 7 x 7 Series, J-5737-1, (N = 7) 8 in bolt circle

Torsional Spring Rate, Kθ = N R2 KR 2

Kθ = 7 (4)2 4000 = 224,000 lb-in/rad. 2

Caution: Shaft length must be considered for potential whirl problems.

Recommended Misalignment Limits

	Misalignment	Bushing Arrangement
		Parellel	Series
	Angular	1°	1.75°
Single
	Parallel	1/64 in	1/32 in
Coupling
	Axial	±1/16 in	±1/8 in
	Angular	2°	3.5°
Double
	Parallel	3/16 to 1/2 in*	3/8 to 1 in*
Coupling
	Axial	±1/8 in	±1/4 in

* Dependent on shaft length (10 to 30 in).

Figure 1 – Parallel Arrangement Figure 2 – Series Arrangement

A part’s listing in this catalog does not guarantee its availability.
To download/print the most current catalog, go to www.lordfulfi llment.com/upload/PC7000.pdf.	Rev.1 10/08