BICYCLE CHAIN BASICS TUTORIAL
Figure 1 - Two different sizes of bicycle chain
When creating your own human powered vehicles, a chain drive will likely be your chosen power transfer system, as it is an inexpensive, easy-to-install and highly efficient drive mechanism. Bicycle chains are fairly simple, requiring only one inexpensive tool to remove and attach links. Since a recumbent cycle will often require a chain that is one and a half to 3 times the length of a regular upright bicycle chain, some basics should be known, as you will probably need to create the chain for your vehicle.
There are two basic types of bicycle chain: single speed chain and multi-speed chain. Single speed chain is mainly used on kids' bikes, BMX bikes, coaster brake cruisers, and heavy cargo bikes. Multi-speed chain is used on standard speed bikes and mountain bikes that require the use of a front and rear derailleur to change gears. Both types of bicycle chain have a pitch of 1/2 inch (ANSI standard #40). This measurement indicates the length of the links. Although every type of bicycle chain and freewheel have a 1/2 in pitch, the width of chain varies quite a bit, from 3/32" to 1/8".
Single speed bicycle chain is wider, having a width of 1/8 inch. This type of chain will not fit a multi-speed freewheel nor will it fit properly through a derailleur cage. Multi-speed chain comes in various widths, with 3/32" being the most common size. Multi-speed chain is designed with a lot more side-to-side flex to allow it to function properly with a derailleur system. Flexibility is very important in a multi-speed system as the alignment of front and rear chain rings could be off by as much as 3 inches, depending on which gears are being used. Figure 1 shows the two common sizes of bicycle chain; 1/8" on the top and 3/32" on the bottom. At this angle, both chain types look very similar since you can only see the pitch, not the width.
Figure 2 - Single speed (top) and multi-speed (bottom)
Figure 2 gives you a much clearer view of the difference between a 1/8" single speed chain (top) and a 3/32" multi-sped chain (bottom). The multi-speed chain is obviously narrower to fit the narrower chain rings on a multi-speed freewheel, and it also includes a beveled edge on the inner link to allow for better meshing with the teeth when switching gears.
Figure 3 - A bicycle chain link tool
When bicycle building becomes your hobby, one of those "must have" tools will be a chain link tool as shown in Figure 3. For under $20, this small tool will give you a lifetime of service, able to break and rejoin any size of bicycle chain in a few seconds. The other method involves using a punch, a hammer, and a finishing nail, but I assure you, the chain link tool is so much easier and makes a worthwhile investment. To open a link, place the chain into the holder as shown in Figure 3, and then turn the vice handle clockwise to press out the link pin.
Figure 4 - Removing the link pin
Figure 4 shows the link pin pushed out by the chain link tool after turning the handle around a few times. This tool makes adjusting a chain pretty much effortless which is a good thing since you may have to adjust a long recumbent chain on a new project several times to get it right.
Figure 5 - Separated chain
After breaking a chain with the link tool, it will look like the one shown in Figure 5, with the link pin pressed through the roller to the outer plate. The pin only needs to be pressed far enough out so that the roller can be released. Notice that the pin has been slightly flattened at the end. This helps to ensure that it does not slip out of the plate hole, which is only holding it there by friction. I have broken many chains over the years, but it has always been a plate that has snapped, never a pin that has failed.
Figure 6 - Parts of a chain link
The two outer plates, pins, and rollers with inner plates are shown in Figure 6. Normally, you would not need to pull a chain apart like this, as there are no wear parts that can be replaced. When a chain fails or stretches, the damage is always throughout the entire chain, which needs to be replaced. For this reason, you should never join together chains that are from different manufacturers or may be years apart in wear. Often, the outer plates will have the manufacturers code stamped on them.
Figure 7 - A stiff link causes problems
After pressing a link back into a chain, the pin will have forced the plates together, causing a stiff link as shown in Figure 7. This stiff link will cause a skip or jump every time it passes through the rear derailleur, and must be fixed before use. A stiff link will always be created when first joining a chain, but it can easily be relaxed.
Figure 8 - Relaxing a stiff link
To fix a stiff link, hold the chain so you can work the links side to side as shown in Figure 8. Press your thumbs against the plates on each side of the stiff link and force it back and forth until it no longer sticks when you bend the chain. Once the link has been relaxed, it will act like every other link without causing the problem shown in Figure 7.
Figure 9 - Multi-speed freewheel and chain
Figure 9 shows a common 6 speed freewheel and the 3/32" chain that fits into it. Although the larger single speed (1/8") chain will also fit into the teeth, it will be too wide to fit properly through the rear derailleur. You could get away with the larger chain on a multi-sped freewheel if you plan to make your bike single speed (fixed gear).
Figure 10 - Chain and a rear derailleur
The 3/32" multi-speed chain is not only designed to fit properly between the rear derailleur cage as shown in Figure 10, but it is also designed to flex side-to-side, allowing some misalignment between opposing chain rings at the front and rear of a bicycle.
Figure 11 - This chain is too thin for the teeth
Multi-speed chain will not fit into the teeth of a single speed freehub or coaster hub as shown in Figure 11, so you don't ever have to worry that you may have the wrong chain there. The width of the teeth makes it impossible to seat the rollers properly.
Figure 12 - Single speed freewheel and chain
The 1/8 single speed chain is shown meshing with a BMX freewheel in Figure 12. A coaster hub will have the same width of chain ring, requiring the 1/8 wide chain.
Figure 13 - Garage door opener chain
Sometimes, you may require a very long chain when making a long cargo trike or even a very tall bike. The chain shown in Figure 13 is standard 1/8 single speed chain, but was taken from a discarded garage door opener, a good source for a very long length of single speed chain.
When working on recumbent cycles and creative human powered vehicles, you will likely need to join together two or more bicycle chains, so consider purchasing an inexpensive chain link tool, and be mindful of the different widths of bicycle chain. Rusty chain should always be discarded. Oiling a chain is a matter of choice. I have never oiled a bicycle chain, and the current school of thought is that an oiled chain is less efficient and will wear out sooner due to trapping dirt between the links. Maybe if your bike lives outdoors and is exposed to a lot of moisture, then a light brushing of light oil may be a good thing.
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