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According to Wikipedia:

Giant Möbius strips have been used as conveyor belts that last longer because the entire surface area of the belt gets the same amount of wear...

(No citations given.) In fact, a Google search reveals that such a conveyor belt was patented by the "B. F. Goodrich Company".

Möbius strip conveyor belt

For me, this raises an alarm bell. Compare the situations:

  • a normal conveyor belt has wear X on one side,
  • a Möbius strip conveyor belt has wear X distributed over both sides.

What difference does it make? It seems (to me) that if a Möbius strip conveyor belt had a longer life, it would only be trivially longer. (In fact, the Möbius strip design itself might increase wear and tear.)

Question: Do Möbius strip conveyor belts last (non-trivially) longer than their conventional counterparts?


Addendum: It was mentioned (thanks to cbeleites) that the linked Wikipedia page on "conveyor belts" comments:

In 1957, the B. F. Goodrich Company patented a conveyor belt that it went on to produce as the Turnover Conveyor Belt System. Incorporating a half-twist, it had the advantage over conventional belts of a longer life because it could expose all of its surface area to wear and tear. Möbius strip belts are no longer manufactured because untwisted modern belts can be made more durable by constructing them from several layers of different materials.[8]

and following the link [8]:

Incorporating a half-twist, it had the advantage over conventional belts of a longer life because it could expose all of its surface area to wear and tear. Möbius belts are no longer manufactured because untwisted modern belts can be made more durable by constructing them from several layers of different materials.

Goodrich Turnover Conveyor Belt System

[Picture source: http://www.daviddarling.info/encyclopedia/M/Mobius_band.html]

(Meta comment: Not including these comments was simply an oversight on my part.)

A similar claim is made here:

Giant Möbius strips were once used as conveyor belts (to make them last longer, since each “side” of the strip of material gets the same amount of wear), but nowadays, better materials are available, so this isn’t necessary.

However, I still don't feel particularly satisfied with this state of affairs, as neither link provides evidence for their claims. Nor does it really address whether or not the Möbius strip design indeed saves (or did save in the past) the wear and tear (as they claim).

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    I am stumped on how to tag this question. Ideas? – Sklivvz Oct 13 '12 at 22:53
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    Much depends on the wear the belt will receive. If it wears out because of surface degradation on the belt, then doubling the surface are would seem to double the life. But if the wear comes from internal stresses in the bending of the belt, then the extra bending may cause more damage. So the design use/purpose of the belt is crucial to any answer. As well, the material the belt is made of will factor in greatly in that life. – user3344 Oct 14 '12 at 1:16
  • @Sklivvz I added a tag for you. – Paul Oct 14 '12 at 1:36
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+50

Usage

There are many uses of conveyor belts, the one relevant to this question is probably the types of long conveyor using in mining, rather than conveyors used for less abrasive loads such as manufactured goods.

Belt Durability

According to Bridgestone

Life of a typical conveyor belt is dependent on top cover wear and cut damage

Their diagram shows that a belt has laminated layers with a strengthened core covered by a carrying surface layer.

belt construction

It seems obvious that if you can utilise both sides of a belt, you are doubling the surface area of the belt and halving the rate at which each section of belt surface is abraded or cut by the materials it carries.

Return Roller Durability

In fact modern belts are often twisted but for a different reason.

According to manufacturers KRK

Depending on the properties of the material handled, residues can still adhere to the top side of a conveyor belt despite the use of scraper systems. As time passes, these residues settle on the idlers in the return run, causing wear, and can affect the straight tracking of the belt and spoil the system. Under this aspect the possibility of turning over the conveyor belt in the return run, where conventional belt cleaning does not produce the effect as desired, is important.

Belt turning specs

and Sandvik

Belt Turning is a solution where the lower belt is turned dirty side up as soon as possible after the drive pulley so that the return rollers will carry the belt touching the clean side

...

Thanks to Belt turning, areas where spillage occurs can be limited to the start and end of the conveyor.

conveyor belt

Conclusions

For certain types of belt, twisting (for whatever reason) confers advantages that can outweigh any problems due to stress during twisting.

If the life of a belt is limited by abrasion of the carrying surface (by the carried material), doubling the material-carrying surface must halve the rate of such abrasion.

  • I'd say: if you take the effort to turn the dirty side up so that the dirt doesn't fall into the machinery then you definitively don't want to use a Möbius-version, as there the (one and only) dirty side is in contact with all idlers. Very nice answer! – cbeleites supports Monica Oct 16 '12 at 21:09
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    +1: This answer is indeed helpful. However, given that each surface patch has halved wear, it doesn't necessarily follow that the conveyor belt itself has halved wear, since the surface patches are on top of each other. It's like burning a candle at both ends (except each end is half as intense). – Douglas S. Stones Oct 16 '12 at 22:36
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The next 2 sentences in the Wiki article are

Incorporating a half-twist, it had the advantage over conventional belts of a longer life because it could expose all of its surface area to wear and tear. Möbius strip belts are no longer manufactured because untwisted modern belts can be made more durable by constructing them from several layers of different materials.[8]

The whole section seems to come literally from the linked web page (scroll to practical applications).

Also: if turning is an option (i.e. both surfaces are the same - which is the case anyways for the one-sided Möbius version) you could turn the belt (periodically; like changing front and back wheels of a car).
That gives the same benefit of wearing both sides, but without the strain of twisting.

Edit to Sefan's question:
sure you can make them layered. But the layers are only of indirect importance here, I think. The important consideration is that you can avoid the wear due to the twisting. And you can make more lasting constructions if you don't need to twist. One example (without layers) where this is immediately clear are hinge chain conveyors, that can basically just go straight (if you look at how curves become possible, you'll see that the constructions are inherently weaker).

The other thing is: turning the belt meant that both sides could be worn down without the strain due to the twist. If the wear of the surface did limit the life of these belts, then this other option

  • did cost the additional work for turning
  • but did avoid the additional wear due to the strain from twisting

There is another wear-related problem with the Möbius-band: conveyed material rests getting between belt and the rolls (e.g. if you convey sand or stones, you will get little grains in between there, and that will cause lots of wear)
So you probably could use it only for certain applications, because for other applications you may end up with even more wear than not turning the belt at all.

Note that if the surface wear does limit the life time, but is different on the material and on the machine side of the belt, you may not get any benefit from turning - but then it is questionable, whether the Möbius-band helps at all.

However, I'm not sure at all whether this kind of surface wear was/is really what limits the life of these belts. Maybe someone else can add wisdom?
I have a bit of experience with flat transmission belts in "ancient" machinery. They don't get "thin" at the surface, they will usually rip across (the old leather belts regularly needed to be repaired), maybe because of a little cut at the side that propagates quickly.

  • Still does not answer the question, because why cant you make a Möbius strip belts with layers then? – Stefan Oct 14 '12 at 15:45
  • @Stefan: please see my edit. It's not really because of the layers. E.g. flat transmission belts are layered, and they sometimes need to be crossed (which is extremely bad for lifetime and for max. transmitted power). – cbeleites supports Monica Oct 14 '12 at 16:40
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    This gets back to my comment above. A twisted belt will show greater wear at the edges, because the edges must travel a greater distance than the center of the belt. Therefore the edges will repeatedly be stressed, so probably developing cracks as the belt ages. If those cracks happen more slowly than the surface of the belt wears, then by using both surfaces of the belt you might potentially see a near doubling of the average belt life. This makes sense if the belt is used as a conveyor (thus abrading the surface.) – user3344 Oct 15 '12 at 9:24
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    Also I would expect a layered belt to be harder to twist... – JNK Oct 16 '12 at 19:09

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