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# Chain Gear

Resembles a tank tread, with different primary purpose
 (+1) [vote for, against]

Consider a rack-and-pinion system. One version of such might be part of a "cog train", where the toothed rack is a sort of "third rail" and the pinion is turned by the train engine to let it climb a rather steeper-than-usual grade.

There is a thing about a rack-and-pinion system that has always bothered me, and that thing is the fact that, at various points during its rotation, all the force between the two must be borne by a single gear-tooth on the pinion.

This Idea has the purpose of allowing more force to be applied, without breaking off a gear-tooth.

We start with a simple drive-chain loop and two same-diameter sprockets. Now we make them super-heavy-duty with the widened chain going around multple sprockets on each drive shaft (exists). Finally, we attach to the chain-links at regular intervals a thing that looks a bit like part of a tank tread, but is actually a single gear-tooth designed to mesh with a rack-"gear".

Since the chain loops around the sprockets, there are multiple places where force is transmitted to the chain. And since the gear-teeth on the chain mesh with the rack at multiple points between the sprocket axles, quite a load can be hauled along the length of the rack.

It occurs to me that the above description assumes that the chain gear is fully taut and is only to be used in conjunction with a rack-gear.

But a chain gear is potentially more versatile than that. For example, if the chain is not taut between the two sprocket axles, then the slack in the chain gear can be taken up by curving the chain gear around part of a large regular gear. That means you can solve the problem of two regular gears meshing with just one tooth contacting the other.

Of course, it would be more efficient if the large gear was a sprocket that the drive chain surrounded, making the chain gear Idea unnecessary in that situation, but, hey, this is the HalfBakery, so... :)

 — Vernon, Nov 20 2011

Hyperbolic worm gears http://www.zakgear.com/Wormoid.html
scroll down for some hypnotising animations [mitxela, Nov 20 2011]

Elevator Idea Multiple-Cab_20Elevator_20Loop
Uses large helixes and a kind of "rack" made of bearings. [Vernon, Nov 21 2011]

A really heavy-duty chain http://i01.i.aliimg..._Conveyor_Chain.jpg
Suitable for attaching gear teeth! [Vernon, Nov 21 2011]

While a chain solution might be effective, I can't help but feel there must be a solution possible involving hyperbolic gears... <link>
 — mitxela, Nov 20 2011

The problem with worm gears, (and all gears where there is considerable planar slipping action between contact surfaces), is all of the sliding action, which is difficult to keep well-lubricated and wears the surfaces down.
 — RayfordSteele, Nov 20 2011

Indeed. Clearly the construction has to be big enough that the entire worm gear can be covered with bearings.
 — mitxela, Nov 20 2011

[mitxela], or you can cover the rack with bearings. See the "elevator" link for details.
 — Vernon, Nov 21 2011

 Just out of curiousity, how is this functionally different between have two or more gears driven by a chain? You know, other than being more likely to fail.

 The only thing forcing the teeth to engage is the tension on the chain. This means that the first flight on the chain will take most of the load, and reduce tension on the remaining teeth, making them likely to slip.

The standard solution to the "single tooth" engagement issue is either to beef up the tooth, make the gear wider (more engagement surface), or if you really need smooth, multiple tooth engagement, go with a helical gear (or a double helical/herringbone) to avoid side loads.
 — MechE, Nov 22 2011

[MechE], tension doesn't have to be the only thing holding a chain gear against a rack. There could be an idler sprocket in-between the two end-sprockets, for example. Or some kind of roller pressing the chain-loop from the inside, toward the rack.
 — Vernon, Nov 22 2011

Sketch those out, and tell me how they're any better than an extra gear in each of those positions instead.
 — MechE, Nov 22 2011

My scrolling finger doesn't hurt. What have you done with the real [vernon]?
 — AbsintheWithoutLeave, Nov 22 2011

He has been Assimilated into the Collective.
 — 8th of 7, Nov 22 2011

 [MechE], it should be obvious. A sprocket and chain system usually has a driver sprocket and a driven sprocket. Here the driven sprocket is just an idler, because the thing that is actually driven (or reacted against) is the rack. So, if you want to apply force to the rack in multiple places using multiple gears, you need to transmit power to those multiple gears that are contacting the rack.

Here, the length of chain gear in contact with the rack is appling force in multiple places between the two. (Pushing the chain against the rack, when tension alone may not suffice, is a separate force which I've mostly ignored here, as being relatively minor.) But still only one driver sprocket is needed in this situation.
 — Vernon, Nov 23 2011

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