There are a number of reasons for using a Ringfeder(Rf), Bikon,

B-Lok, Tsubaki, et al type such as:

1. Uniform clamping between hub and shaft with a known stress field analyzable by typical triaxial stress/ strain mechanics such as FEM. Lames equations is often used, in the classical mechanics approach, to quantify the locking device triaxial strain in transfering the bending, radial, and tangential principle stresses. Show how such a procedure can be applied to the keyway. We have been designing Triaxial stress/strain software codes for pulley stress analyses since 1985 and have not been able to find a representative procedure for the keyways. The methods exists but have too many qualifyiers and correction factors based on experience.

2. Rf eliminates the use of a keyed hub and consequential weldment between hub and end disk.

3. Rf improves the connection between end disk and shell by forcing/preloading the connection into compression thereby reducing the tensile fatigue factor induced from bending as will ocurr withe the keway design.

4. Keyed shafts have many problems in defining the true contact mechanics especially as the shafts become large (> 300 mm) and when to use multiple keyways, the shape of multiple keyways, the tolerances of keyways and the separation of bending and shear in the axial and radial planes for stress limiting criteria.

5. Apllication of stress concentration factors or stress riser factors for keyways as you try to apply it to FEM procedures - taking extreme precautions in defining the probelm and degrees of freedom on the contact/slip elements within the FEM setup. Take note not all FEM codes can even analyze the contact mechanics of the keyway designs.

Other will have more to offer -- read the locking device catalog from the suppliers to get their view and analyses. ■

Dear Mr. Singh,

The Rf type clamping device is placed between shaft and hub which often is also the end disk. The end disk is widened to accomodate the locking device. Therefore, as you note, the hub also is/becomes the end disk. In the event there is a need for a higher level of radial strain, a hub is engineered for the ocassion per the manufacturers instructions.

There are varying designs of locking devices. The typical Rf compression device is one. As you note it can be expensive. Your claim that it equals the cost of the shaft, I believe, is an exageration. Locking devices and cost./performance also vary and should be design for purpose and cost. As I noted, below 300 mm shaft diameter, at the hub bore, there may be other methods including a keyway which should be considered. ■

The internal locking element (Rf's etc) is very common.

The external locking device ...shrink discs is not common on pulleys at all...never seen one..except for large rotary (heated) valves where external locking elements were the only way to transmit power.

Some people use sinle wedge type locking elements eg taperloack...for small pullies but I do not like them as they pull up the end discs and are prone to loosening/fretting.

Ringfeders are used where synchronisation and safety is not paramount.

Keyed hubs are used on scraper chain reclaimer ect where both chain strands need to be in sync. with each other.

Keyed hubs - with heavy shrink fits - are typ used on one side of winch drums in critical applications as they are seen as a positive PT device over the ringfeeder locking element.

Cheers

James ■