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When you are designing your own DIY human powered vehicles, you will likely be using standard bicycle transmission components to transfer your leg energy to the drive wheel. These standard bicycle transmission components consist of a crank set, a rear freewheel, a set of derailleurs to change gears, and of course, the bicycle chain. Recumbent bikes and trikes are longer than an upright cycle, so they require a chain that is also longer. Some recumbent cycles are so long that they may require a chain of more than two times the length of a standard bicycle chain, so you are faced with the challenge of joining one or more chains together to create the necessary long recumbent chain.

This tutorial will demonstrate the use of a chain link tool, which will make your job of lengthening or shortening a bicycle chain extremely easy. If you only purchase one inexpensive bicycle specific tool, then make it this one because it will save you so much effort when joining up chains. The only alternative method to using this tool involves hammering the link pin out with a punch and a finishing nail. That process is so annoying that I am not even going to demonstrate it.

You can purchase the small hand held chain link tool from any bicycle shop for about $20 or less. This tool will last a lifetime and can be used to open up any size bicycle chain as well as garage door opener chain, which is the same pitch and width as single speed BMX chain. You will probably use this tool several times during a bike build as you find that optimal chain length.

Like most mechanical parts, a bicycle chain is a roller chain consisting of many alternating inside and outside links joined together by link pins. A roller chain is a very effective method of power transfer, with efficiency as good as or better than 95% in some cases. A chain drive is also much simpler and certainly lighter than a gear drive system, and it offers the ability to change gears using another lightweight mechanical device called a derailleur. A derailleur simply forces the chain from one chain ring to another, so there is no efficiency lost in the transmission as there would be with a gear driven multi speed transmission.

To open a bicycle chain using the chain link tool, insert the chain into the tool's cradle with the link pin that you want to remove positioned under the tools link pushing pin. Press the chain into the tool using your thumb as you spin the lever in the clockwise rotation to set the tools pushing pin up against the link pin. The pushing pin must contact the link pin directly on its face or else you could damage the link plate as the pin is forced through the hole. Ensure that the pushing pin is directly over the link pin before you start cranking on the lever to separate the chain.

With the tool's link pushing pin lined up directly over the chain link pin, start cranking on the lever, turning it in the clockwise rotation to force the pushing pin onto the chain link pin. As you turn the lever, the pushing pin will be threaded downward onto the chain link pin, and it will begin to slide away from the link plate. Keep turning the lever in the clockwise rotation until it completely locks out. At this point, the chain link pin will be pushed all the way through the center roller and will be sticking out of the far side of the other link plate. The tool is designed so that the link pin is not pushed all of the way out of the far link plate. If the link pin were completely removed, it would be extremely difficult to reinstall it into the link plate again.

To open the chain, just bend it at the open link point and it will come apart. The fact that the open link pin is still installed a small bit into the link plate will work to your advantage when you are reinstalling the chain in your bike because the chain can be snapped back together to allow you to install the chain tool. This means that you can install a chain on the bike through the derailleur and check it for length without having to push the pin all the way back in each time. It may take two or three tries to get the optimal length chain, so this does make the job much easier.

One thing to note is that you cannot shorten a chain by only a single pin. Well, you can actually remove the pin next to the one you just opened, but if you did that, then you could not rejoin the chain because you need an inside link at one end and an outside link at the other in order to make a join. So, look at the links to ensure that you will end up with the same type of link at the end of the chain you are removing links from. In this image, I started with an inside link, so I removed the pin that would once again leave an inside link at the end of my chain.

Rejoining a chain section is just as easy as removing a link. Place the inside link into the open outside link so that the open link pin holds the chain together. If you are doing this on a bike with a rear derailleur, then the small amount of link pin that remains on the inside of the open link should be able to hold the chain together even under the force of the rear derailleur tension spring.

Open the tool all the way by spinning the lever in the counter clockwise direction until you can insert the open link with the pin facing upwards towards the link pushing pin. Press the chain down into the tool's cradle with your thumb as you crank the lever in the clockwise rotation, pushing the pin back into the other link plate.

When the pin begins to enter the other link plate, watch carefully to ensure that the pin has been pressed through both plates at the same distance. When the link pin appears to be installed through both plates evenly, remove the tool from the chain.

At this point, your newly joined chain will have a very stiff link that will refuse to bend where the link was pushed back into place. If you tried to use this chain on your bike, it would cause your rear derailleur to skip and jump all over the place each time the stiff link was forced through the cage. To repair this stiff link, you need to open the gap between the link plates ever so slightly. This can be done by grasping the chain in both hands and bending it sideways back and forth around the stiff link. When I say "bending it sideways", I mean against its natural angle of rotation so that you are forcing it to bend in a way that will help open up the link plates a bit.

When you are adjusting the length of a chain that is already installed on a bike or trike, there are a few tricks you can use to make the job easier. If you need to pull the chain through the rear derailleur, then you will need to push out a link that leaves an inside link on the side of the chain that will go through the rear derailleur cage. If you tried to fit an outside link through the derailleur cage, then it would get stuck since the link pin is pushed out through the opposite plate. Of course, the opposite is true if you want to pull the chain forward through the chain guide tube; you need the inside link on that side.

If you just need to pull or add a link or two in your chain, it is best to break it on the lower side just ahead of the rear wheel. This area is easiest to reach on most bikes, and will allow you to rejoin the chain with minimal fuss. To open the chain, place the tool on the chain so that the cranking lever is facing away from you on the other side of the chain. This will allow you to use the tool facing you when you put the chain back together, which is more difficult than pulling it apart.

Push the link out using the tool and then snap apart the chain to release the two halves. The rear derailleur spring will push the derailleur cage backwards and pull the chain halves apart. Because of the ratchet installed in the rear freehub, the chain will not slide off the rear freehub, but you may need to place something through the crankset chain ring to keep it from moving. A screwdriver placed through the front chain ring will hold the cranks from spinning the chain off while your make adjustments.

To remove the chain from the rear derailleur, pull down on the cage and then slip the chain through the lower side, along the lower idler pulley. If you took out the wrong pin and ended up with an outside link here, then you may still be able to twist the link pin through the derailleur cage by twisting the chain. If not, then you will have to remove both of the bolts that hold the idler wheels in place to open up the derailleur cage. The other option is to unwind the chain all the way around the other side of the bike first.

Now, slide the chain through the derailleur cage over the top idler pulley while you lift the chain up over the rear freewheel chain ring teeth. Be careful not to scrape the chain along your frame or you will likely scratch or chip your paint. This is especially true when you are assembling a new bike that has just been painted and the paint has not cured for more than a week.

To reinstall a chain through the rear derailleur, repeat the last steps in the reverse order. Feed the chain over the top of the rear freewheel towards the left and then over the top derailleur idler towards the right, pulling the chain all the way through. Because the freewheel will turn in reverse, this part is easy. Now, wrap the chain around the bottom derailleur idler so it forms a backward S around both idler wheels.

Pull the chain so that all of the upper slack is picked up and so that the derailleur cage begins to move forward towards the front of the bike. You can now clip the chain back together using the open link to hold the chain together while you get ready to use the chain link tool. If the rear derailleur pulls so hard that the chain won't stay together, jam a board or something between the spokes to keep the derailleur from pulling back while you set up the chain for rejoining.

The properly installed chain will form a backward S as it travels around the rear derailleur idler wheels as shown here. Now, you can use the chain link tool to reinsert the open link pin back into the chain.

The reason the chain link tool was placed with the lever facing away from you when you opened the chain is so that you can use it facing you when you rejoin the chain. Rejoining the chain is a bit trickier since the rear derailleur is trying to pull the chain back open, so it's just easier to handle the tool this way.

There will always be a stiff link after you reinstall any link pin using the chain tool. Sometimes the stiff link will be obvious like the one shown here, but often you will not be able to see it. A stiff link running through the rear derailleur will cause it to jump and possibly throw the chain off the chain ring and onto the next one for a short duration. This will be noticeable as a "poing" sound as you ride or it may be more dramatic, causing a gear change every few seconds.

To locate a stiff link that is not visibly obvious, turn the cranks in reverse and watch the rear derailleur for any jumping movement. If the rear derailleur pops forward every few seconds, then this is the stiff link that's causing friction as it's forced to bend around the small diameter idler wheels. Stop right after the movement and bend each link by hand to locate the offending stiff link.

You can easily fix the stiff link while the chain is still installed on the bike thanks to the slack given by the rear derailleur. Grasp the chain on both sides of the stiff link and bend it from side-to-side. Force the chain using a lot of strength, but don't worry, you won't be able to permanently damage the chain because it can take a lot of force. Do this a few times and then flex the link by hand to ensure that they all move with no friction. If the link is still stiff, then perhaps the chain is rusted or damaged. In that case, you need to replace the bad link or the entire chain.

After relaxing the stiff link, spin the cranks quickly in reverse and keep an eye on that rear derailleur for any skipping or jumping. The rear derailleur should remain almost perfectly still no matter how fast you turn the cranks in reverse.

When you are building up a new long chain for a recumbent bike, start by placing the chain on the largest front chain ring and around the middle rear freewheel chain ring. Install the chain through the rear derailleur to form that backward S shape and then pull the lower halves of the chain together until the rear derailleur cage is in the position shown here, with the two idler wheels sitting in a line with the rear axle. This is a good place to start as it will allow enough slack in the chain to reach the larger rear chain rings, but will also let the rear derailleur cage pick up the slack as the chain shifts onto the smaller chain rings.

The two derailleur idler pulley axles form a line with the rear axle is what I call the "default position". The chain on the largest front chain ring and the middle rear chain ring is probably the gear you will use most often, so this position will give the tension spring in the rear derailleur the most movement in either direction as you shift. Of course, you will need to experiment on your own bike because there are a variety of different crank sets and rear freewheels available with a wide range of gear sizes.

So, if you plan on building your own chain driven human powered vehicle, then consider purchasing an inexpensive chain link tool as it will make working with bicycle chains very easy.

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