TerraCycle Idlers and Your TerraTrike’s Chainline
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By Ashley Guy of UtahTrikes.com
If you are looking to increase the performance and speed of your trike the best place to start is by decreasing the rolling resistance. A trike that rolls well will go faster, so start by fixing your alignment and consider faster tires. Once you've decreased your rolling resistance the next step is to make the pedaling as efficient as possible. The first thing to be addressed should be eliminating as much drag as possible in the drivetrain. This article discusses chain management and available idler solutions utilizing the TerraCycle idlers.
Your Chain’s Path
Driving a rear wheel with pedals that are in front of you requires that the chain be routed from the front chainring to the rear sprocket. Because of the seat position and bottom bracket position on most recumbent-style pedal vehicles, the chain typically needs to be routed at various angles. There are two chain paths to be considered, each with their own special considerations.
Power Side - The power side of the chain route is the route the chain takes from the top of the chainring to the rear sprocket. This is the most important part of the chain path as it is this portion of the chain that actually propels the wheel. While pedaling, the power side of the chain is always under tension. The harder you pedal the more tension is placed on the power side of the chain path.
Return Side – On the return side the chain travels back from the drive sprocket to the bottom of the chainring. Depending on your drivetrain, the return chain may travel through a derailleur or chain tensioner. Even considering this tension on the chain, the return side of the chain’s path has much less tension applied to it than the power side.
Chain Routing Methods
How we direct the power and return sides of the chain’s path can have a dramatic effect on the drivetrain’s efficiency. The most popular ways to route the chain are as follows:
Direct – A chain that runs directly from the chainring to the drive sprocket in either direction will be the most efficient. If you take a look at a single-speed bike you’ll see what I mean. A direct chainline has no drag imposed by routing mechanisms. It is possible to have only one side of the chain’s path be direct.
Sprocketed Idler – A chain is in effect a series of round bearings that are designed to ride on toothed cogs that match the chain’s bearing diameter. This is seen as the chain wraps around the chainring and drive sprockets. Whenever the chain is under high tension a sprocketed idler should be used to change the chain’s drive angle. This becomes increasingly important as the chain’s angle (and wrap around the idler) is increased. Chain paths that are not under tension should not use a sprocketed idler as there is risk the chain will come off the cogs.
Smooth Idler Pulley – As mentioned above, the return side of the chain path is typically under a lower tension than the power side. For this reason a sprocketed idler is not recommended for the chain’s return path. A pulley that guides the return path of the chain will provide a minimum amount of resistance provided that the chain does not bump across it. This is because the idler pulley will smoothly rotate as the chain moves across it. A pulley that can maintain positive contact with the rolling chain will have less surface friction between the chain and pulley surface.
Chain Tubes – The least efficient way to route a chain is to run it through a tube. While better tubes will have a low friction surface like Teflon, there will always be some friction as the chain rubs along the tubing. This friction increases dramatically when tubing is actually used to change the chain's direction. On straight tubing runs (typically used to protect clothing from chain grease) there will still be friction at any point the chain touches the surface of the tubing, and this friction increases with the length of the tubing.
Another major consideration that should be given to chain routing is that of the chain’s position perpendicular to the movement along its path in relation to the chainring and sprocket being driven. In other words, if you look down on the chain’s path the most efficient route will be a straight line from the chainring to sprocket. While modern 8-speed and higher chains have some sideways flexibility, keeping the chain aligned between the chainring and drive sprocket maximizes efficiency. The tricky part here is that a typical cycle drivetrain requires the chain to move sideways as it moves across different chainrings in the front or sprockets in the rear. To keep the chain’s path efficient the routing system should be allowed to move sideways as gears are changed to maintain the straightest line possible. An idler that moves laterally with the chain will be the most efficient. In addition to promoting a straight chainline, it will not cause friction along the side of the pulley as the chain goes through the idler/pulley. The idler’s ability to move freely with the chain is what we call “float”. A floating idler will also improve shifting in a derailleur system, as there will be less sideways force on the sprockets.
The TerraCycle Solution
TerraCycle manufactures performance upgrades for recumbent bikes and trikes, and their specialty is idlers. They work with many makes of cycles and their idlers are even OEM on some models. Since no two vehicles are the same they have created kits for the most popular cycles. While all the kits vary depending on the specific model, they all share TerraCycle’s idlers in common. TerraCycle builds these idlers in Oregon and they come with a five-year warranty.
|The TerraCycle Power Idler|
The TerraCycle Power Idler is a finely machined component that will provide years, and many thousands of miles of service. The Power Idler can be taken apart and rebuilt should it ever need serviced or cleaned. The best way to appreciate the TerraCycle Power Idler is to dissect it and evaluate each piece.
Bearing – The TerraCycle Idlers use 8mm ABEC 7 sealed bearings. While it is debatable if ABEC 7 bearings are faster than the ABEC 5 bearings used with most OEM idlers, they are manufactured to a stricter tolerance. These bearings will provide years of service, and because they are sealed they require no further lubrication. Should a bearing ever fail, replacements are easy to find as this is a common size used in roller blades and other skates.
Side Plates – The side plates of the Power Idler are made from 6061 machined aluminum. Since the chain actually rides on the idler's sprocket, the side plates are merely needed to keep fingers out. The craftsmanship of the TerraCycle machining process is immediately noticeable.
Sprocket – The idler’s sprocket has 15 teeth (some other sizes are available), and is made out of either titanium or aluminum depending on the version. TerraCycle cuts these sprockets themselves. The sprocket’s inner teeth are designed to lock onto the idler housing. While very similar to a sprocket you would find on a rear-wheel cassette, the TerraCycle sprockets do not have the beveled edges found on a typical PowerGlide-style sprocket. Since the sprocket is the part of the idler that maintains constant contact with the chain this part has the potential to wear out, although you should easily get tens of thousands of miles from this sprocket.
Idler Housing – The Power Idler’s housing is machined from aluminum and comprised of two sides. Each side clamps all the other pieces together. The housing is held together by three stainless steel bolts.
Rubber O-Rings – An interesting feature of the TeraCycle Power Idler is that the toothed sprocket is sandwiched between two rubber o-rings. These o-rings keep the sprocket centered in the idler and keep the chain from rubbing the side plates.
Titanium vs Aluminum – The TerraCycle Power Idlers can be purchased in either aluminum or titanium versions. All of our High Performance Idler Kits include the titanium idlers, with the standard front and rear kits are available with either metal. Generally, the titanium sprockets will last longer than the aluminum. According to TerraCycle’s own website: “When deciding between a Titanium or an Aluminum cog, we advise that stronger riders or any rider doing high mileage go with Titanium. The Aluminum cogs will give a long useful service life but will show more wear after thousands of miles. We generally recommend a titanium cog for trikes since the angle of the chain line tends to be larger putting more stress on the idler.”
|The TerraCycle Return Idler|
The TerraCycle Return Idler is immediately recognizable by its orange urethane bed. The outside diameter of the Return Idler is the same as the Power Idler, and shares similar composition with exception if the urethane bed. Let’s take a look!
Urethane Bed – The orange urethane idler bed is made from the same material as used in industrial conveyor rollers found in highly destructive places like mines. Incredibly resilient, this material has the perfect combination of flexibility and low resistance. It is this flexibility that allows the Return Idler to maintain positive contact with the chain. As the chain passes around the Return Idler, the bed is allowed to compress just enough for the chain to smoothly turn the idler. The urethane material then rebounds without damage. Cleaning the bed is easily done by wiping it down. Even after thousands of miles there is no noticeable wear on the bed.
Side Plates – The side plates of the Return Idler are made from an ultra-strong polycarbonate material. While primarily designed as a guide to keep the chain on the Idler’s sprocket, the side plates are strong enough to help route the chain where float is not possible or minimal.
|The Over/Under Idler|
In some cases there are chain routes that require the power side and return side of the chain to run next to each other. The TerraCycle Over/Under Idler combines the Power Idler and Return Idler into one unit. It has all the features of those Idlers. The main reason to use the Over/Under idler instead of a Power Idler and Return Idler next to each other is that the power and return portions can be closer together. This is especially important when both idlers need to move together to promote chain float.
The Stock TerraTrike Chain Management
The chain management system on most of the Wizheelz TerraTrikes routes the chain along the bottom of the frame in a side-by-side manner. This chain route has the main advantage of keeping the chain away from the rider. The disadvantages of this routing solution are:
Hard Idler Pulleys – There are four idler pulleys in total that the chain must pass through. Because these pulleys are hard, the chain must bounce over the pulley’s inner bed. As the chain bounces over the pulley it will slowly cut into the Delrin material. Friction increases for the life of the idler as the surface of the pulley gets gouged. This is especially noticeable on the front power side idler where the chain’s angle is most severe. The main advantage of the stock WizWheelz idler is that it is very inexpensive.
No Float – The stock idlers run side by side and are bolted solid to the frame. The power side of the chain is ran along the inside while the return side runs along the outside idler pulleys. This means that the chain must bend sideways to accommodate different gear choices. As the chain is bent sideways through the idler it rubs on the side of the idler resulting in chain drag.
|TerraCycle Front Idler Kit|
The TerraCycle Front Idler Kit includes one Power Idler, one Return Idler, chain keeper, and spacers. It uses the stock idler axle bolt and mounts in the stock idler position. The performance difference with the Front Idler Kit is immediately noticeable with a quicker feeling acceleration. The TerraCycle Idlers are also much quieter than the stock idlers therefore providing a more pleasurable riding experience. Since the Front Idler Kit mounts in the stock position, the same clean chainline is maintained, keeping the chain away from the rider.
|TerraCycle Rear Idler Kit|
The TerraCycle Rear Idler Kit includes one Over/Under Idler, Idler clamp, bolt, spacers, and chain keeper. This Idler Kit mounts onto the frame tube and moves the idlers from their stock position. The clamp and special axle bolt are designed to allow the idler to float. Since the power and return sides of the chain run across the same idler, the idler position will slide to a middle point between the two chains. While not perfect, this setup markedly improves the shifting of the rear derailleur and decreases friction along the chain.
|TerraCycle High Performance Idler Kits|
Utah Trikes has worked with TerraCycle to create the High Performance Idler Kits and they are available exclusively through us. These kits are designed with maximum performance in mind. Since these kits do not follow the stock chain routing they require more time to install, possible modifications to other portions of the drivetrain, and in some cases move the chain higher and closer to the rider. As a performance-oriented upgrade the use of these kits should be carefully considered versus using the standard TerraCycle Idler Kits. The main features of our High Performance Kits are:
Maximum Float – Highest priority has been given to idler float on the power side of the chain’s path. The High Performance Idler Kits provide the maximum efficiency by promoting the straightest possible chainline.
Chain Alignment – In addition to power side float, the High Performance Idler Kits reduce or eliminate the side-by-side chain routing. This allows the chain to maintain the maximum efficient alignment between the drive sprocket and chainring on the return side.
Reduced Idler Count – In most cases we’ve been able to eliminate an idler with our modified chain routing. This decreases friction along the chainline and results in more power being delivered to the wheel.
Currently we have the following High Performance Idler Kits available:
High Performance Idler Kit for Cruiser, Tour, Access, Sport, and Race TerraTrikes
High Performance Idler Kit for Tandems
We currently have prototypes and will soon release the following kits:
High Performance Idler Kit for the Edge
High Performance Idler Kit for the Zoomer
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