Wednesday, June 19, 2013

Bicycle Chains and Oils

As you can see by this article the bicycle industry will never give you the bad news.

Viscous oil verses Dry Wax lubes:

To make oil viscous enough to stay in the links for several months, you need a soupy like substance such as aluminum oxide, STP uses zinc oxide. I thin it with Naphtha to flow it into the links from an eyedropper, let it evaporate overnight! Then wipe all excess off. Covering it with a hard wax lube (which must also evaporate), can help keep the oil from sucking grit into the links.

Actually it is not advisable to apply wax over any kind of oil, it is hard to dry.

Tungsten Disulfide or Molybdenum Disulfide is a little cheaper than Teflon but they will turn oil black and will stain your clothing and possibly your skin.

PTFE is inert to virtually all chemicals, it is a white, waxy solid with the coefficient dynamic friction of wet ice on wet ice. And maybe better mixed into a paraffin wax solution with Naphtha solvent, than in oil.

Paraffin wax has been reported to last only about 300 miles (possibly less if you are a strong cranker with cargo), while the viscous oil mixture had been reported to last up to 1000 miles in dry conditions. But for wet conditions the wax should be more water resistant and have less chance of sucking road grit into the links. But it is hard to clean off the chain; I do not know how well the penetration would be when adding more without cleaning it out of the links; it depends on how the chain is made.

The most important part is to not dribble the mixtures on your chain! Use small drops on each link and let the solvent evaporate, or you will end up with a mess.

The wax will be squeezed out except for a thin-film layer at 4,000 psi on the link pins.

Light oils are all made from sewing machine oils and cost much more than anything else because they have to be applied very often. Dumond Tech does not last much longer than any of the light oils.

PTFE Molecular Structure

    From Cost-Benefit Comparison: Electric Bike Chain-Suck"

      With oil as a lubricant, the abrasiveness of the sandy road grit has hardly any physical effect because the particles that can get into the chain links are very small.

      Particles already in the link can hardly be removed by any cleaning method (not even with an ultrasonic bath). In order to prevent particles being transported into the link in the first place, the chain should be kept dry and clean on the outside by wiping it regularly with an oily cloth. Additionally, sprockets, pulleys and chain-rings should be kept as clean as possible because these parts are in direct contact with the rollers of the chain.
      Cleaning solvent will mix with the lubricant which in most cases destroys its lubricating feature; cleaning liquids which do not have 100% degreasing effect, such as diesel fuel are recommended.

Even so called lubes with a noticeable white wax film do not actually stay in the links long enough to lubricate your chain for more than a few days, and should only be used after lubrication. Dry-wax film reduces the amount of dirt sticking on the chain and partly protects the link against dirt and water.

This chain wax lasts only about one hundred miles when used to lubricate the links, but is very good for protecting the chain's outer surfaces from rain. Spray it on lightly to keep it from building up. And only after lubricating the links with viscous oil! 

chain construct: 

Pins inside full bushings of (six element) chains are well protected against lubricant depletion because both ends were covered by closely fitting side plates.

Some motorcycle chains have O-ring seals at each end. In the swagged bushing design where there is no continuous tube because the side plates are formed to support the roller and pin on a collar with a substantial central gap; In the wet, lubricant is quickly washed out of pin and roller then the smaller bearing area of the swagged bushing for the pin and roller can easily gall and bind when lubrication fails.

If I had enough money I would convert to a timing belt and internal gears.

Old chains lasted longer than the new narrow chains because they had more to wear away and because the amount of sprockets was less. Chain rings lasted longer also!

The friction savings would be minimal either way, since friction relates to the materials, and lubrication and not to surface area. Since the material is steel both ways, any difference would be tiny. But the bearing grade bushing provided for longer wear life.

 You wouldn't want a bushing chain these days (even if you found one) because your derailleur system wants more side flexibility than is possible with this design. Also, it would be difficult to produce a bushing chain narrow enough for today's requirements.

When it comes down to it, buy a decent (mid-quality) chain, keep it reasonable clean and lubricated, and replace it as necessary. With decent choices, drive-train maintenance costs will not be a major factor either way.

If you get a lot of mud and crud build up on your sprockets, you may as well take it to a car wash then use WD40. Then keep applying it every week, wiping off the extra.

For a typical large motor you need a 12-114 chain and sprockets which can only be found with go-cart sized chains. (#35)

E- Bikes:

     Ten speed cassette cogs are 1.6-1.7 mm thick, 9 speed 1.75-1.8 mm, 8 speed 1.8-1.9 mm, 5-6-7 speed 1.85-2.0 mm, BMX 3.2 mm thick.

The upshot is that a ten speed cog will wear about twice as fast as a BMX cog. The chains themselves, on new cogs, will wear internally at the bushings and pins, based on the quality of the chain. But since the narrower cogs wear faster, this will indirectly accelerate chain wear.

I have said this too many times. Somebody needs to produce a drive-train for high powered (over 750 watt) mid-drive bikes. A five speed cassette with cogs and spacers twice as wide as ten speed, wider idler spacers for the dérailleur, and a shifter with every other detent missing/filled to use BMX chain.

A 14-42 cassette gives nice even spacing, a 3:1 or 300% or 8-24 mph range (however you want to think about it), and a minimum of seven teeth engaged.

"Bushingless" chains have bushings; they're just stamped into the side-plates and therefore not a separate subcomponent. Bushingless chains are easier to lubricate, and allow the chain more side flex, so they're generally better for pedal bikes with dérailleur shifting.

Traditional chains with bushings have a lot more projected area in the bushing-to-pin interface, so they last a lot longer in single speed applications with good sprocket alignment, like track bikes or industrial equipment. You have to lube them through the gap between sideplates, which is sometimes tricky. That is one reason that they invented thin oil.

A BMX chain is basically what was used for dérailleur bikes for decades. My first road-bikes all had 5 speed rear freewheels. They shifted just fine with stiff, bushed chain that was basically indistinguishable from BMX chain. 

Modern ramped cogs would make that chain shift even better. Cog center-to-center spacing on those bikes was 5.5 mm. The center-to-center spacing of 5 cogs on a current cassette would be 7.9 mm. A chain as stiff as rebar would work with that much space.

Chains wear out sprockets, rather than the other way around. Once a sprocket is badly worn, then it can wreck a chain. So the thickness of the sprocket is much less important than the width of the chain bushing surface.

A narrower sprocket leaves more room for a 1/8" chain to deflect sideways before contacting the adjacent sprocket. So a wider sprocket isn't necessarily an advantage.

What is chain suck? The chain will try to cling to the sprockets causing the whole drive to bunch up and crash the bike. So it really is good to keep the chain very well lubricated.


No comments: