Today we are highlighting ball bearing blocks as part one of our three part discussion on blocks, their characteristics, and uses.
So, what is a Ball Bearing Block? In its simplest form, a ball bearing block it is a housing containing a rolling sheave with balls lining the race on the either side of the sheave. The balls reduce friction by minimizing bearing surface and roll between the moving surface and the non-moving part of the block. Because of this, lines are able to slide through the block with ease. For example, when you want to turn downwind and quickly ease the mainsheet, the less friction there is on the line, the faster the boom will swing outward.
What types of ball bearings are there?
The main differences you will see in performance come from the types of material the ball bearings are made of.
Delrin is the most common material found in blocks. It has very smooth running characteristics and is appropriate for low to moderate load applications. It is not as hard of a material as the other options and in applications where the block is loaded up for long periods of time, the balls can flatten, decreasing the performance of the block.
Torlon is the most common choice of material for high load applications, and is a self-lubricating material which reduces maintenance. These characteristics also mean it comes with a higher price tag. Stainless steel balls are capable of withstanding the highest loads and are also found in ball bearing blocks, but since they are heavier and require more maintenance than the other two, they are less common.
What types of applications are ball bearing blocks appropriate?
Anything where you need low friction with low to moderate loads, meaning just about everywhere. These are definitely the most common blocks you will see on a boat. For dinghies, you will almost exclusively see ball bearing blocks. As you get into larger boats (30’-35’), ball bearing blocks are still the most prevalent, especially in applications where low friction is desired, but you will also start seeing plain bearing and/or roller bearing blocks in high static load applications, where the line is set under load and not frequently adjusted. The diagram below gives a good “rule of thumb” look at the selection process for the different types of bearings and materials.
Maintenance for Ball Bearing Blocks
If your ball bearing block is not running well, you can try a drop of McLube OneDrop. If that doesn’t work, you probably need to replace the block. Above anything, absolutely never use Sailkote on your roller bearing blocks, or tracks. This will over lubricate your bearings thus preventing them from rolling properly and causing flat spots, which then impair the functioning of the block. Of course we still love McLube SailKote, but just not on ball bearings.