Monday, April 28, 2014
I've been working on a new location, for a new edition of these pages, centered around the new business. It still has elements of a blog, but is also more of an informational web-site, with pages providing details about the business itself.
Please head over to the new Artispin Design page.
I am gradually moving relevant articles from here, with some editing, over to the new site. This old blog site will be removed in the not-too distant future.
I see too [through the neglect of this blog] there are some unaddressed comments. I'll be taking care of that too, one way or another.
Monday, October 15, 2012
Note that if you intend to switch to another brand or type of lube, the chain should be quite clean to start. Some lubricants very much prefer to start on bare metal, so this may require removal and soaking in biodegradable degreasing solution. Hopefully you’re happy with the lube you’ve been using, so you can simply add oil and clean all in one process without removing the chain.
Rather than allow old and dirty or excess lubricant to overspray or drip inside your house, this is best done outside, or at least in your garage. Hanging your bike, using a repair stand or car-trunk/hitch rack, works great. All you really need though is to lean the bike, standing on its wheels, fairly straight and upright against something solid. The drive-side should face you, and pedals and chain can spin freely backwards without striking anything. If you’re feeling especially clever you might find a way to secure the bike so it leans toward you slightly, helping to prevent excess lubricant from spattering onto your rim’s braking surface.
You probably have two options for application: drip and spray. Drip is usually more economical, is certainly less wasteful, and easier to control. With spray you’re paying more for the propellant and spray mechanism. Although spray is faster to apply, it is also messier, and probably requires more time and effort to clean up afterward. For either option you will also need a dry shop rag or a couple paper towels.
Using a drip:
Choose an easily identifiable link, such as the reinstallation pin or "master" link, if possible and position it on the lower section of chain just behind the front sprockets. Carefully drip one drop of your favorite lubricant on each roller all the way along the lower chain until you’re as close as you can comfortably get to the derailleur pulleys beneath the rear cogs. Stop, and rotate the crank backwards just enough to move the most recently lubed link forward to behind the sprockets again. Repeat beginning from there, applying along the chain until you reach the pulleys. After doing this about 3-4 times you should be able to tell that you’ve reached the first link you lubricated, the entire chain is oiled, and there’s no need to go further.
Put the bottle of lube down and spin the crank backwards several times with your right hand, allowing the chain to flex over the gears and through the pulleys, permitting the fresh lube to penetrate the tiny rollers in the chain. Now pick up a rag or paper towel and, gently wrapping your left hand around the lower chain, continue rotating the crank (with your right hand), drawing the chain through the rag in your left hand. You can stop and re-situate the rag as many times as you like. If it becomes saturated before you’re satisfied, switch to a clean rag, spinning while you wipe off the excess. What you’re trying to do is wipe off any lube from the exterior surface of your chain. Don’t worry… you’ll never get it all, and what you do get should not be there anyway. The lube that will make your chain run smoother has already penetrated and you can’t wipe it off. What you are wiping away however includes lots of road grime and abrasive dirt, so you’re lubing and cleaning simultaneously, and minimizing the excess that could attract more grit, which wears your chain and gears as you ride. All the lubrication your chain needs will remain inaccessible beneath the rollers.
This is nearly identical to the above procedure except that you simply spray the chain, with your left hand, just as it passes over the rear cassette cogs while you rotate the crank in your right hand. This generates quite a bit of over-spray, and you’ll want to be careful not to get much on the braking surfaces of your rim, or rotor if you have disc brakes. One nifty thing about doing it this way however is often you may feel in your hand a noticeable drop in resistance, especially if some time has passed since the last time this was done, serving as a demonstration of how beneficial a lubed chain can be. Again, when you’re finished, be sure to wipe off all the excess you can with a rag or paper towel. This keeps the chain relatively clean, which is just as important as keeping it lubricated.
Tuesday, January 26, 2010
Monday, February 09, 2009
- Fine handling is not only subjective, but also largely a function of a particular bicycle’s intended use. A variety of purposes and even wider range of rider experience and opinion invalidates any idea of targeting a single precise value for a design parameter (trail), especially without regard for all the others.
- Trail is a function of exactly 3 dimensional values: head-tube angle, fork offset (rake), and overall tire diameter. While trail is a strong indicator of handling characteristics, all three of these affect how a bicycle handles, independent of the trail they generate in combination. Additionally, there are several other dimensional and non-dimensional factors to affect handling characteristics, none of which are related to trail or its components.
- Experience has shown how it is surprisingly difficult to build an un-ride-able bicycle (with respect to handling geometry). Experience also indicates which controllable factors have the greatest effects, and within only a narrow range. For example: head angles for road bikes rarely run outside the range of 71 to 74 degrees (generally in half-degree increments). It should then be easy to imagine how a builder can quickly develop a seemingly fundamental “knowing” for how to combine head-angle and fork offset options to consistently produce an experience of optimal handling characteristics. While this builder likely knows what trail is, he or she finds little reason to care.
So, why the occasional fuss about trail? My best answer for now is… because at the very least, it is interesting to some of us. We find the complex theory and math behind why single-track vehicles operate the way they do fascinating. In fact, to me one of the most interesting things about bicycles is the dichotomy of simplicity (as the simplest and most efficient mode of transportation known – even more than walking) and complexity (our limited understanding of the finer points for how they steer and stay upright remains largely theory – explored by physicists and mathematicians). That said, interested physicists, mathematicians, and builders alike generally agree that trail is a dependable value as representative of, at least in large part, a bicycle’s basic handling characteristics. The term representative of however is unfortunately often confused with meaning responsible for.
What Is Trail?
Most simply, trail is the horizontal distance along the ground separating the points of intersection of each, the steering axis and a vertical line through the front axle, with the ground. That is, extend to the ground the axis about which the fork rotates and note the point where it strikes ahead of the tire’s contact point on level ground. The distance between the center of the contact patch and the point we just located is trail. A formula for trail is provided in the diagram. See if you can tell, by looking at the picture, what happens to trail as we adjust the variables. Does trail get bigger or smaller as the head-tube angle is made steeper, or shallower? How about as we shorten or lengthen the fork rake? As we change tire sizes?
Actually, I prefer to distinguish this as Ground Trail, and here’s why:
What trail is really meant to represent is the arm of a moment, or an applied torque. The moment we refer to here is that applied by the frictional force between front tire and the ground about (relative to) the steering axis. Effectively this is the force you experience as your bike self-stabilizes coming out of a turn. This effect is also related to what castors do on shopping carts – they roll in the direction you push the cart. (I say related because the cause and effect have actually switched places in this example.) Notice however that the Ground Trail in the picture is not perpendicular to the steering axis, as it must be to accurately represent a moment arm. This is okay for design purposes, as Ground Trail is always proportional to our true Mechanical Trail. They are not close enough to be used interchangeably, but Ground Trail does quantitatively indicate the castor effect generated by the combination of steering-axis inclination and fork offset (assuming tire diameter as a constant design parameter).
The question was, “How do you design for neutral trail?”
The issue I have with using the term neutral is that its common use implies too much subjectivity. Handling characteristics are subjective enough already without us tossing in further ambiguous descriptions. It is however common to hear references to neutral steering and neutral trail. So, what do they mean? It is because nobody seems to have clearly defined their meanings that I avoid using them. Once we have a mutual understanding of meanings, I am happy to use them too. So then, what does neutral mean?
What is neutral gear? Neither forward nor reverse. That works – it’s stationary, but it doesn’t translate well into handling characteristics. Well, what is neutral temperature? Neither hot nor cold. Hmmm… you see the problem here? We have not established exactly where the threshold lies between hot and cold. What is neutral steering? Neither twitchy nor sluggish. Same problem… too subjective. How about, neither understeer nor oversteer? That’s better, but why not just say predictable steering, and avoid all the confusion? Neutral position – neither left nor right – straight!
Okay then… what is neutral trail? I have read some strange definitions, and here’s one (roughly, from memory since I can’t recall exactly where): Neutral trail occurs when the top-front of the bicycle neither rises nor falls when the handlebars are turned. This actually never happens, but I think what the writer meant was when trail and fork offset are equal. This is certainly possible, but generally will not create favorable handling characteristics, and neutral so often refers to a “sweet spot” of perfect handling – stable but responsive, predictable but agile, etc. Even here, that sweet spot is subjective. It’s different for everyone, especially with so many possible riding disciplines with widely varying handling requirements. So maybe what was meant by the question was…
So, how do you use Ground Trail to design a bicycle’s geometry for an individual’s preferred handling characteristics?
Now we’re cookin’ with gas! The answers however will probably double the length of this already too-long post, so I will discuss overall handling geometry in the near future.