SIDE AND END CHOCKING, POURED RESIN CHOCKS

The lateral and transverse location is maintained by side and end chocking.The number of side chocks depends upon the length of the engine.

It is extremely important that the engine is properly installed during building. 

The consequence of poor initial installation are extremely serious since it may lead to fretting of chocks, the foundation and bedplate, slackening

and breakage of holding down bolts and ultimately in a worsening in the alignment of engine.To maintain engine alignment it is important to inspect the bolts for collect tension and the chokes for evidence of fretting and looseness.

 An alternative to the traditional choking material of cast iron or steel is epoxy resin. This material, originally used as an adhesive and protective coating,

was developed as a repair technique to enable engine to be realigned without the need for the machining of engine seatings and bed plate. It is Claimed that the time taken to accomplish such a repair is reduced so reducing the overall cost although initially developed as repair technique the use of epoxy resin chocks is becoming widespread for new buildings. 

Resin chocks do not require machined foundation surfaces does reducing the preparation time during fabrication. 

The engine must be correctly aligned With the propeller shaft without any bed plate distortion.

This is done in the usual way with the exception that it is set high about 1/1000 of the chock thickness to allow for very slight chock compression when the installation is bolted down.

The tank top and the bed plates seating surfaces must then be thoroughly clean with an appropriate solvent to remove all traces of paint, scale and oil. 

Because resin chocks  are poured it is necessary for "dams", made from foam strips, to be set to contain

 liquid resin. Plugs or  the holding down bolts are now inserted. Fitted bolts being sprayed with a releasing agent, ordinary bolts being coated with the Silicon grease to prevent the reason from adhering to the  to the metal. The outer sides of the chocks are now dammed with thin section plate,  fashion as a funnel to facilitate pouring and 15 mm higher than the bedplate to give a slight head to the resin. This is also coated to prevent adhesion. prior to mixing and pouring of the resin it is prudent to again check the engine alignment and crankshaft deflection. 

The resin and activator are mixed thoroughly with equipment that does not entrain. The resin is poured directly into the dammed off sections. Curing will take place in about 18 hours if the temperature of the chocking area is maintained about 20 to 25 degree Celsius. The curing time can be up to 48 hours if the temperatures of a substantially below this. During the chocking operation it is necessary to take a sample of resin material from each batch for testing purposes.

The advantages claimed for "pourable"  epoxy resin chocks over the metal chocks include:

- Quicker and cheaper installation. 

- Lower Bolt tension by factor of 4 when         compared to metal chocks.

-  Elimination of misalignment due to              fretting and bolt slackening. Because          ofthe intimate fit of resin chocks and          the high coefficient of friction between        resin and steel the trust  forces are              distributed to all chocks and bolts thus       reducing the total stress on fitted Bolt         by about half.