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roller chain efficiency

roller chain efficiency

roller chain efficiency

(OP)
It's generally conceived that roller chain typically have an
efficiency of around 98%. Out of all the different types of losses,
does anyone know which one is the most significant?

There are primarily:

1. Sprocket tooth/chain sliding friction (engagement/disengagement)
loss

2. Chain segment bending loss.

3. Bearing loss.

The joints in the chain are bushings. But is it possible to
substitute it with bearings? It may get larger and heavier, but what
if I need a chain that has the ultimate efficiency, but weight and
size are not as important? Can that be done? With bearings at the
joint, it should have a higher efficiency.

The sprocket tooth sliding friction isn't very big from what I
heard. This is because the chain segment interface is "free to
roll". You can literally touch the tooth interface on the chain and
rotate it with your fingers.

I need a chain that can get an efficiency of 98.5%. Can I replace the bushings in the chain with bearings?

RE: roller chain efficiency

I'd just use the largest dia. sprockets I could fit, and make sure they're aligned well.  Do NOT run an "O" ring type chain.

RE: roller chain efficiency

That number only applies to low speed applications with well designed components.

I would guess it is more of an upper limit than an average.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

RE: roller chain efficiency

(OP)
Greg,

it's generally conceived that spur gear have an efficiency of 99%. Is that an upper limit or is that an average also?

Thanks

RE: roller chain efficiency

I don't know. If a gear set were designed for one load and speed, to reduce slip at the interface to a minimum, I'd have thought better than 99% would be achievable.

I normally use 98% for gearsets in good condition, but that falls to less than 90% in some (common) circumstances. designing gearboxes to work efficiently over a wide range of torques is very difficult.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

RE: roller chain efficiency

At higher pitchline velocities the losses from lubricant churning can be immense.

http://www.zf.com/zf-n/defaultz.asp?id=652&lang=1

Maybe 10 HP on this pup.  If the max power delivered is around 50 HP, then the how in the world can the "efficiency" ever exceed 80% ?

RE: roller chain efficiency

You might want to check out Morse Hyvo chain. It does not use rollers in the joints. The joints are rocking pins so do not have the sliding friction of roller chain. Roller chains have chordal motion lifting each roller over the top of the sprocket arc causing vibration. The drawback is if you need a sprocket with a different number of teeth than what Morse makes available, it is virtually impossible to get anything made. It took six months just to get an "off the shelf" sprocket.
Also, there are two flavors of "Morse", Borg-Warner Morse who make the automotive chain and only talk to you if you want 100,000 pieces and Emerson-Morse that sell the chain for every other application but will sell single pieces.

RE: roller chain efficiency

(OP)
why is the Silent Chain so much more efficient?

It seems chain drives are usually single speed only. The only
multispeed chain drives are used on bicycles, and it uses the
derailleur mechanism.

But on motorcycles, industrial power transmission, conveyors, ect... it
seems to be single speed. I'm not sure.

Are there any non-bicycle applications that utilizes a multispeed chain
drives? Does it use a clutch or derailleur?

Thanks.

RE: roller chain efficiency

Agricultural machines often use interchangeable sprockets or sprocket clusters to change shaft speeds.  For example, a planter when ground driven will use different sprocket ratios to set seed population in the field.  To my knowledge all applications require the machine to be stopped and manually reset the ratio.

RE: roller chain efficiency

Roller chain has friction when bending each link pin at the sprockets. Hyvo chain uses rocker pins that roll against each other. It also keeps the pins at the pitch line of the drive whereas roller chain goes through a chordal motion with each roller contacting the sprocket.
If by "single speed" you mean it does not have variable ratios, then you are correct, the same as a gear drive. Since the number of teeth around the sprocket has to be an integer and nobody has built phase shifting sprockets as yet, the only ways to change the ratio is by changing sprockets. Variable ratio belt drives trap a Vee belt between moveable conical plates, usually one spring loaded, the other mechanically driven. A lot of friction pulling the belt into the groove and pulling it out again.
Transmissions could use multi-speed chain drives but there probably is no advantage over a gear cluster. Heavier and more parts. Bicyces only transmit 1/3 HP or less. I suspect the latest 27 speed designs are close to a trade-off with a variable planetary system. The derailluer system has the big advantage of no neutral between gears.

RE: roller chain efficiency

(OP)
Does the efficiency of the chain decrease as it elongate/wears? If so, how much?

Thanks

RE: roller chain efficiency

(OP)
Are there any applications for the chain drive in construction/offroad/earth machineries?

RE: roller chain efficiency

Check the Morse website. I believe that Hyvo chain is used in high speed highway snow blowers, rear wheel drive of some off road trucks, et cetera.
I believe earth moving trucks use hydraulic drive. through a planetary drive in the wheel hub.

RE: roller chain efficiency

There aren't many applications using chain drive in offroad/mining, actually I can't think of any modern applications, other than Caterpillar-type crawler tracks.  Earth moving trucks are either gear driven or electric drive.

RE: roller chain efficiency

I was a little slow this morning.  I've thought of a few applications using drive chains, however the are low speed and I suspect not very efficient.  The tandem drive units on motorgraders use chains, as well as most of the small skid-steer (bobcat) type loaders use chain drive to power the axles.

RE: roller chain efficiency

(OP)
Back to my original question.

Which type of loss is more significant for a chain drive?

1. Sprocket tooth/chain sliding friction (engagement/disengagement)
loss

2. Chain segment bending loss.

or are they about equal?

As a follow up question, can you tell me if the following type of analysis is valid:

a gear pair is inheritantly more efficient than a chain drive because there is only ONE teeth to teeth interface for a pair of gears. In another word, one gear can drive the other gear DIRECTLY.

A chain drive requires TWO interface. First the sprocket drives a chain, then, the chain drives a different sprocket. So in another word, a sprocket cannot drive another sprocket directly. Since there is 2 interface/steps, I think a chain drive (even those silent types) should be at least twice as inefficient as gears.

And that's not counting the bending loss at the links.

That means, if the gear pair has an efficiency of 99. Then the chain can not have more than an efficiency of 98. Of course this is assuming there is no bending loss at the links and the sprocket to chain meshing is just as efficient as the regular gear tooth meshing, which is unlikely.

Is that correct?

RE: roller chain efficiency

The torque is the important consideration, not the hp. Having said that, I don't know how powerful or torquey it was. Derailleur chains are less robust than standard ones, for sure, but that is partly because on a pushbike you are trying very hard to minimize space and weight, whereas for a gas powered vehicle you've got a lot more space.

I don't know if you can make a power assisted derailleur work with a standard industrial chain, I'm sure the sprocket design is important as well.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

RE: roller chain efficiency

Engine braking will not be usable with a derailleur.

An overrun clutch will be necessary to avoid the chain going slack on overrun

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

RE: roller chain efficiency

There is something missing here. The efficiency of spur, and all other gears, goes down significantly with increased load and speed. In support of this, any gearbox that is transmitting high loads either needs huge amounts of air or auxilliary cooling. Increased lubrication and even forced oiling are often needed. Gears also need to be housed in a very stout structure. This also increases rapidly with torque at any speed.

Roller chain is not nearly as efficient as Morse Hy-Vo. The Hy-Vo chain experiences far less increase in friction with increased speed or power. All load bearing parts roll in place, no sliding. The "pins" are really two pins that are slightly "C" shaped and placed back to back. This makes for very long life with minimal lubrication. Very different from average silent chain found in transfer cases and cam drives.

Nothing beats a roller chain for long shaft center distance and low cost. Many big road graders are roller chain drive. Most street bikes, most cars, are silent chain drive. So was the PJ Indy Turbine car (Morse Hy-Vo).

RE: roller chain efficiency

(OP)
Fabrico, you mentioned the "rocker pin" joints the Morse chain uses. It uses 2 "C" shaped pins that rolls instead of sliding. But it seems they are only used on silent/inverted tooth chains. You never a roller chain with the "C" shaped joints. Why is that? Is it something that can only be used on the silent chain?

Thanks

RE: roller chain efficiency

(OP)
Actually, Magnograil, thanks for bring up the Morse chain. But how come the rocker pin joints are only used for silent chains and not regular roller chains? Is it because of inheritant design limitations or is it cost?

Thanks

RE: roller chain efficiency

It is something that can only be used on silent chanin. But it is only used on the Hy-Vo chain not typical silent chain. That and the special tooth shaping is what makes the HY-Vo so different from other silent chains.

RE: roller chain efficiency

(OP)
Thanks.

Got another question.

You know when the roller chain is wrapped around the sprocket, theoretically the load should be shared across all the teeth on the sprocket. Theoretically.

I really doubt that's the case in real life. The chain and the sprocket are not machined to exact specification like gears so it's unlikely that the pitch of the chain will exactly match the pitch of the sprocket. Also, once the chain starts to wear and elongate, things get worse.

Therefore, I think maybe only one or two teeth is bearing the load at any instant. There will be a small "gap" between other teeth and their corresponding chain roller that prevent them to transmit power.

What do you think?

RE: roller chain efficiency

It would be good if you and others can read up the Hy-Vo design. It's really quite interesting. The development of this particular chain allowed things to be done that were not done before. As this type of chain wears and rides farther out on the sprocket. The teeth literally open up and widen to take up slack and spread the load to several rows of teeth. The "pins" roll only during the transition from straight to bent and visa versa. But it is a constant process and all ads up, especially with so many links. NASCAR type racing only recently discovered the substantial advantages. Many "Super Bikes" are Hy-Vo chain driven. With the need for vehicles to be more efficient, I think you will be hearing more of Hy-Vo chain. http://www.theautochannel.com/news/press/date/19990602/press024377.html  

RE: roller chain efficiency

(OP)
"As this type of chain wears and rides farther out on the sprocket. The teeth literally open up and widen to take up slack and spread the load to several rows of teeth. The "pins" roll only during the transition from straight to bent and visa versa"

Thanks for the help Fabrico.

But I don't understand why the chain will wear and rides farther out on the sprocket if the joints "rolls" rather than slide. That means there should be essentially no wear or elongation. Or is there? Maybe it's not perfect rolling?

RE: roller chain efficiency

Perhaps the easiest way to see it is to look at a silent chain laying flat on a table with the teeth facing up. If you set a sprocket on it, the teeth won’t be able to fully engage each other because the teeth of the chain are not lined up but more in a crossed position, making the gaps too small. In operation, the larger the path radius, the more the teeth head toward that position. The chain teeth literally get wider and essentially fill the wider gap between the sprocket teeth.  

As far as no wear or elongation, they are close, but nothing is perfect. Roller and needle bearings don’t slide either but they do wear.

RE: roller chain efficiency

(OP)
I heard the silent chain is about 5 times as expensive as a regular roller chain? What do you think it's the main reason for this price difference? Is it because of the special roller joint? Or do they require more accurate machining of the teeth?



 

RE: roller chain efficiency

"Therefore, I think maybe only one or two teeth is bearing the load at any instant. There will be a small "gap" between other teeth and their corresponding chain roller that prevent them to transmit power.

What do you think?"

I think that's why MC chain OEM's advise (and experience demands) that the chain & sprockets be replaced as a set- they wear complementarily and spread the load, but are never ideal whether new or old.

What about periodicity?  If the chain length and number of sprocket teeth are matched so that the teeth always contact the same rollers is that better or worse for wear?

RE: roller chain efficiency

"What about periodicity?  If the chain length and number of sprocket teeth are matched so that the teeth always contact the same rollers is that better or worse for wear?"
 
It is highly recommended that a "hunting tooth" ratio be used so the chain does not contact the same teeth.

Hy-VO chains are installed in what might be considered virtually permanent places, such as in the deep center of superbike engines, FWD transaxles, etc. They generally outlast the parts around them. I used some 3" wide 1/2" pitch 10 years ago and it costs $100 per foot.

RE: roller chain efficiency

(OP)
I wonder if the sprocket tooth profile is formed such that it meshes with the rollers in a way similar to gears? (with very little slippage)?

RE: roller chain efficiency

There is very little friction and the teeth do "roll" into place.

Magnograil mentioned that Morse is difficult to work with for the little guy and he is right. Ramsey makes what they call the RPV line and claim it to be equivalent and fully interchangable with Morse Hy-Vo. http://www.ramseychain.com/prod_power_trans.asp

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