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I noticed while at an amusement park that on the roller coaster, each link of the chain has what can be considered a combination inner and outer plate. The side plates are somewhat diagonal so they start as an outer then become an inner. So my question is if these work well for roller coasters which have a lot of load, why not use a similar scaled down design for bikes so that odd length chains are possible?

Here is a pic of a roller coaster chain so you can see what I am talking about: (you can click on it for a more detailed larger pic).

Roller coaster chain

Maybe this design wont shift well? I wonder what the main reason is. Motorcycles also do not use it. Maybe large pitch chains require it cuz being 2 links too long or short is a big difference but with a short pitch chain (1/2 inch or so), it is not so critical?

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...or you use a half link chain? – Batman Feb 19 at 5:32
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Mainly because it isn't necessary, and using the sort of links shown in your picture unnecessarily complicate things and would muck up modern indexed shifters. – Daniel R Hicks Feb 19 at 13:07
    
Seems kinda odd that bikes don't normally use this type of chain, I have never seen this on any motorcycle, yet roller coasters DO use it. If this design requires thicker side plates, why even use it on a chain that already is very heavy? I wonder which design has more strength and if it is better to use the design like in the pic or have the side plates straight (slightly diagonal). Very interesting from a mechanical viewpoint. Maybe a Mechanical Engineer can chime in and explain that. That chain is on a 48"x40" pallet so look how few links it takes to span it. Impressive. – David Feb 19 at 13:46
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Rollercoaster chains don't have low weight nor efficiency as their design goals. – whatsisname Feb 19 at 17:18
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@whatsisname - So how is the inner and outer alternating chain design more efficient than the "diagonal" design? Where is the proof to back up that statement? – David Feb 19 at 18:02
up vote 15 down vote accepted

Bike chains have to have some other method to take up the error (like horizontal dropouts or tensioners even on a single speed).

They'd still need this if the maximum error was halved, so you wouldn't really gain anything. Chains would need thicker walls as the walls would no longer be in pure tension (the force would tend to straighten them). This would make the chain heavier and wider, neither of which is desirable. It would also be more expensive as parts would have to be stamped then bent rather than just stamped.

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But there are 1/2 link bike chains kmcchain.us/chaintype/half-link-series-12x18 – Paparazzi Feb 19 at 11:02
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@Frisbee true. They're all 1/8" chains as you say in your answer, which are heavier to start with than 3/32" and not so fussy about external width, therefore the plates can be a touch thicker. They also don't have to handle shifting. But they're still (from a quick search) a niche item and even the manufacturer doesn't give any real reaosn to use them. The Q and my A should probably have been about "rare" rather than "never". – Chris H Feb 19 at 11:25
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Actually you can get them in 3/32 kmcchain.us/chain/hl810-gold Manufacturer does not list a reason to use any of the series – Paparazzi Feb 19 at 12:54
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@David for manufacture, the alternating design is considerably easier. The bent-plate design is only conceptually simpler. – Chris H Feb 19 at 18:38
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@whatsisname Those statements are not true. When a 1/2 link is used they typically have the option for a full adjustment. The main use is BMX, trick, street, trials ... that want an exact set up (it may or may not be of real value). It would not be completely useless on a derailleur as there could be an edge case of you could get the range with an odd number. But the edge cases in no way justify the down side of the design in a derailleur application. David seems to have this concept of anything that can conceptually be done should be done. It is not worth debating with him. – Paparazzi Feb 19 at 20:28

But you do see it in BMX, track, and fixie
You don't see it in narrow chians as have a derailleur to take up slack

half link design

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I don't see how this design would interfere with shifting as a "standard" chain has alternating inner and outer plates so the maximum width of the chain should be about the same for both designs. – David Feb 19 at 14:25
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@David Chalk it up as yet another disappointment in modern bicycle design for you. Could and should are not the same. So you don't like the term half link - stackexchange cannot fix that. – Paparazzi Feb 19 at 16:07
    
Sure they could. Don't use a term if it is not accurate and/or it is misleading. Use better names. – David Feb 20 at 3:56
    
@David I get "could and should are not the same" is foreign logic to you. Can't help you. I could fly east to get from NY to LA. And could is verb. – Paparazzi Feb 20 at 4:59

My guess is there is no technical reason one way or the other. Its likely a light weight half link will actually stretch while under tension unless its more expensive or heavier than a full link chain. (Roller coaster chains don't have to be light weight so its less of a problem.). If its a material difference in performance I do not know. Its entirely possible to engineer a half chain to work with derailleurs, so that is not a reason not to do it.

What I do know s half link chains cost more. Maybe they only make high quality Half Links, and you cannot buy cheap versions, or maybe they cost more for the same quality. However many people buy on price. On one web site I looked at, Half link chains start at $25, Full link chains start at $8. Manufacturers don't use half link chains, and most people faced with that difference would need a fairly compelling reason to change to a different chain type from manufacture given the price difference. This could be more about inertia in the supply chain rather than manufacturing cost.

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Yeah, it's a good point about the half links stretching, due to the bend in the plates. – Daniel R Hicks Feb 21 at 14:08
    
"Entirely possible to engineer a half chain to work with derailleurs"? That would introduce a few non trivial challenges. – Paparazzi Feb 21 at 17:00
    
Technically chains do not stretch, rather they elongate due to wear. They are not rubber bands. – David May 7 at 12:43
    
@David. A normal bike chain the plates are flat, so at their maximum tensile strength. The 'stretch' I refer to would happen, as the bent plate under tension will straighten out under tension, depending on the metal and thickness will depend if it fully returns to its original form or eventually it becomes permanent – mattnz May 7 at 19:59

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