chain design (slack chain) question

[wangp1283]

In an chain drive I'm design, the majority of the length of the chain will be slack and under no tension. In another word, between the driving sprocket and the driven sprocket, the chain the is under tension (load), but for the rest of the chain, the chain is slack.

But the slack chain is very long and will tend to drip. I cannot shorten the chain because it's essential to the application. I can "take up" the slack chain with some idler sprockets.

So my question is this: since the chain is under no load, the design of the idler sprockets or its placement isn't that important right? (from an efficiency point of view). For example, I don't even need the idler sprocket to have teeth to perfectly mate with the slack chain. I can just use a bare cylinder to "take up" the slack chain. Even though this will create some noise when then chain is running. But because its the slack part of the chain, it virtually has no effect on the efficency?

The reason I'm asking this is because it's hard to design an suitable idler due to the unique geometry of this special chain.

Thanks.

 

[evelrod]

Having done several chain drives for conveyor systems for several notable companies---I tried a couple with the "nylon/teflon" (read that synthetic)type tensioner block very similar to what is used on motorcycles---with limited success. They worked quite well and were relatively quiet---just needed frequent maintenance.
Most all systems did not use tensioners, but the most successful applications that did,(usually higher speed) used a proper sprocket mounted as close to the down side of the drive sprocket as practical. Most high speed systems, at least in my area of expertise, were in the process of being converted to Gilmer type, "cogged tooth" belt drives when I retired. Some were fairly large, 5" X 30'---a high dollar cure for a non existant problem, IMO.

Rod

Rod

 

[patprimmer]

Rod

The compound is probably Graphite and Molybdenum Disulfide filled Nylon 6.6. That was extensively used in automotive timing chain tensioners and guides, but in some critical applications Nylon 6.6 has been replaced with Nylon 4.6, as it has about a 50 deg C higher melting point, and good abrasion resistance right up to it's melting point.

Hydrocircuit.

Have a look at some plastic timing chain tensioners. They are used by many motor companies, including some top end names like Saab, Volvo, MB, BMW etc.

In fact, on thinking about it, they are more often used by top end manufacturers as they are more likely to use a chain rather than a belt.

Regards
pat pprimmer@acay.com.au
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