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Perhaps about as exciting as PAC10 football for some, but I found these chain-related videos interesting.........


 

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1. "How It's Made." The industrial-strength chain manufacturing process was interesting. No O-rings or X-rings on these chains, I imagine because . . . at the beginning of every shift, someone must anoint the chain runs by pouring 5-gallon buckets of foul-smelling green lubricant on the entire run. No O-rings/X-rings necessary with such periodic total immersion lubrication. Leastwise, that was my job each day while working on a steam-powered oil drilling rig . . . the chain shown in the video clip appears rather huge, but . . . imagine the chain size necessary to pull 10,000 feet of drill pipe from the earth!

2. Drag-racing Motorcycle Chain. Fascinating! Might be adjusted correctly for the straight-and-level drag strip, but . . . statically, looks kinda TIGHT in the view shown, to me, in comparison with a street/trail bike configuration.

Thanks for sharing, planalp!
 

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I searched but couldn't find any videos of o/x-ring chain production. Easy enough to envision how those extra steps occur, I guess.

I found the chain video interesting. I'm still trying to figure out if that rear sprocket has some kind of intentional sawtooth design or if the camera angle just makes them appear to be curved. I'm sure a chain probably does the same thing to a lesser degree on the motorcycles we all ride but it shows just how dynamic a chain can be. Maintain That Chain!

As Damocles noted, when sitting still that chain looks like it's very tight but once stuff start's happening, it's flailing around like one of these:

(Drag Racer in the foreground. Planalp in the background.)

 

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I'm still trying to figure out if that rear sprocket has some kind of intentional sawtooth design or if the camera angle just makes them appear to be curved.
I, too, noticed the saw-tooth appearance of the rear sprocket; and, like you, discounted the image as an optical illusion/distortion of some sort.

In my opinion, one wouldn't want to drag-race with a sprocket actually having a saw-tooth profile. Throwing a chain at full power and 100-or-so miles-per-hour could result in unhappy outcomes, IMHO, especially considering the barrier and/or the vehicle in the adjacent lane!
 

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Fascinating that the chain looked tight when stopped, yet like it was going to jump off the sprocket under power.
 

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Fascinating that the chain looked tight when stopped, yet like it was going to jump off the sprocket under power.
Not to wander too far into the realm of my own FANTASY, but . . . could the phenomenon be a function of CHAIN STRETCH? Under power, the elasticity of the upper chain run might create a little slack; resulting in the video image of the flopping lower chain run.

That said, the chain stretch mentioned above might NOT exceed the elastic limits of the chain, thus permitting return of chain to its original length at rest.

Again; postulation only; no observations/measurements/references available.
 

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Not to wander too far into the realm of my own FANTASY, but . . . could the phenomenon be a function of CHAIN STRETCH? Under power, the elasticity of the upper chain run might create a little slack; resulting in the video image of the flopping lower chain run.

That said, the chain stretch mentioned above might NOT exceed the elastic limits of the chain, thus permitting return of chain to its original length at rest.

Again; postulation only; no observations/measurements/references available.
I'll suggest that the drag bike has a very limited amount of rear suspension travel and it is ALL above the center line of Front sprocket, Swingarm pivot & Rear axle centers.

So 'normal' chain tension with the bike elevated would be near 'zero slack'.

With no load on the bike but with wheels on the ground there would be some slack. When launched & accelerating the rear suspension would compress, the wheelie bar would contact the ground and nearly 100% of the bikes weight and therefore traction would be on the rear tire.
As the acceleration tapers off the suspension would start to re-extend and the slack would be lessened.
When the front brake is then applied at the end of the run the slack would again return to 'zero'.

The sides of the rear sprocket tooth valleys are 'fluted' to reduce weight. Some dirt bike sprockets were 'fluted' to allow mud disbursement and reduce weight.

Welcome back, Planalp. I enjoyed the clips.
 
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I'll suggest that the drag bike has a very limited amount of rear suspension travel and it is ALL above the center line of Front sprocket, Swingarm pivot & Rear axle centers.

So 'normal' chain tension with the bike elevated would be near 'zero slack'.
Agree!

In fact, SOME drag bikes have swing arms that do not SWING; true "hard tails" with solid struts replacing rear spring-and-shock assemblies.

CAVEAT: Neo-off-topic comment follows: Ain't sure, but . . . I think some sport ATVs featured geometrical design with "constant radius" geometry between front and rear sprockets, wherein chain slack remained the same throughout suspension compression/extension. Maybe not, but . . . would be a difficult trick anyway with conventional motorcycle front and rear sprocket placement, IMHO.
 

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I'll suggest that the drag bike has a very limited amount of rear suspension travel and it is ALL above the center line of Front sprocket, Swingarm pivot & Rear axle centers.

So 'normal' chain tension with the bike elevated would be near 'zero slack'.

With no load on the bike but with wheels on the ground there would be some slack. When launched & accelerating the rear suspension would compress, the wheelie bar would contact the ground and nearly 100% of the bikes weight and therefore traction would be on the rear tire.
As the acceleration tapers off the suspension would start to re-extend and the slack would be lessened.
When the front brake is then applied at the end of the run the slack would again return to 'zero'.

The sides of the rear sprocket tooth valleys are 'fluted' to reduce weight. Some dirt bike sprockets were 'fluted' to allow mud disbursement and reduce weight.

Welcome back, Planalp. I enjoyed the clips.

ditto; and there is no such thing as chain stretch. the dirt sprockets with the flutes were Sidewinders

Dave
 

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ditto; and there is no such thing as chain stretch.
Then, my kindly old professors who insisted, "For every stress there's a strain," lived (and died) in vain!

Comforting to know, a TOTALLY INELASTIC material has been discovered/invented for the manufacture of chains!

:)
 

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As a term relating to wear, there is no such thing as chain stretch, true, but in terms of strength of materials there is true chain stretch when under load. This is a true stretch or elongation of material, and it is temporary (unless, of course, the yield strength of some component is exceeded. In that case there is a less-than-graceful-degradation event.)

That would be an interesting exercise in relatively simple math. If you knew the torque produced at the crank, first gear ratio, and the sizes of the sprockets, figuring out how nearly the load on the chain approaches the yield strength of the material should not be hard. Thus the amount of load-induced elongation the chain would see. I guess we would have to ignore possible pin bowing, though at a couple hundred links there is a multiplier to the effect.

Or perhaps not, on second thought. The side plates should be quite stout, perhaps pin bowing is a major element of load-induced chain elongation.
 
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The load induced temporary stretching would only involve the top half of the chain run, as the bottom half would be in its normal relaxed state (no load). So IMO, that could not account for the amount of slack seen in the bottom run of the chain in the video.

One might suggest that the drag bike might run up to a 200 link chain. So if each link had a possible elasticity (before failure point) of say .001 inch x 100 links that would only account for 0.1 inch of chain slack. Far short of what is seen in the drag bike video, IMO.

Hardened steel parts have little elasticity. They either hold the applied load or fracture catastrophically.

One should not allow the vent hose from a flooded cell (conventional) battery to vent or worse, possibly drip on the hardened steel drive chain. It will cause 'hydrogen embrittlement' of the hardened steel which can cause the side plates or rivets of the chain to crack under lighter than normal loading.
 
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Paul, I think your original hypothesis was spot on. Our discussion of stretch is akin to talking about how many angels can dance on the head of a pin. Remember, Damocles started the discussion with "FANTASY" ;^). That, and we are differentiating the term "chain stretch" mainly as an exercise in mental gymnastics.
 

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I must defer to the metallurgy/chemistry/strength-of-materials knowledge, and calibrated-eyeball video viewing, of this august forum membership!

:)

Otherwise, I have evidence supporting PROOF of solid-strut hard-tail dragstrip motorcycle modification; and . . . I may be in error, but I honestly believe common radius (with the suspension) chain drivetrains exist/existed on certain ATVs . . .
 

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Take notice of the suspension link under the drag bike. Play the video thru the 1:20 mark. Pause it. Put your cursor on about 1:02 - 1:04 and move the preview image back and forth to watch the front tire lift and chain slack increase as the suspension compresses and the bike rocks back onto the wheelie bar. It's impossible to see it in-motion, but the still frames show it, IMO.
 

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We can debate the subject till the cows come home but a chain doesn't "stretch"....i.e. the sideplates don't elongate and then snap back to their normal size after the force is removed. As Paul said, there isn't much elasticicty to steel. Chains are said to "stretch" when their bushings/pins wear, effectively increasing the overall length.....they do not and cannot EVER get shorter. If you managed to really stretch or distort a chain side plate, it would stay that way.....or break if it went too far. Metal CAN stretch by applying a force to the yield point.....but for practical purposes, this simply doesn't happen when it comes to motorcycle chains.



Cheers,
Dave
 
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