Does the angle of a drive train effect the efficiency of energy transfer

[jamdaaman]

If the angle of a drivetrain in a bicycle becomes steeper - ie 65degrees, will it become less efficient in comparison to normal flat drivetrain?

 

[drawoh]

jamdaaman,

Draw a free body diagram and work out the forces. There should be no difference between two chain drives as shown. These look like bicycles. That second one either has a tiny rear wheel, or the rider is perched way high up on a weirdly configured bicycle. These could affect speed and efficiency.

--
JHG

 

[jamdaaman]

These arent bicycles they are the chainsets. The bicycle is on a flat surface but the chainset/groupset is at an angle and thus the chain is at an angle.

 

[jlnsol]

Why do you think that the efficiency will change?

 

[rb1957]

well there is a small amount of work done against gravity which would imply a small amount of lost energy so horizontal should be better than inclined (but probably by an unmeasurable amount).

another day in paradise, or is paradise one day closer ?

 

[BrianPetersen]

... and do you not think the side of the chain that's going back down the other side precisely counterbalances the side of the chain that is going uphill, thus resulting in "no difference"? If not, why not?

 

[Nescius]

I do not believe that there is any theoretical difference. By "theoretical", I mean using principles of work, energy, etc. without friction. The original post asks about efficiency. So, I'm assuming jamdaaman agrees that there's no theoretical difference.

If somebody presented experimental data that showed a measured difference in practice, I could be convinced.

How? Chain tension, sag, and related things would be different, depending on the direction of gravity. Imagine a very lightly loaded drivetrain, with an extremely heavy chain. I could be convinced that all the minute frictional losses would change with gravity direction in a measurable way.

Edited to add: Similarly, I could be convinced that frictional losses differ in the case of a horizontal arrangement, depending on which span of chain is driving the load, top or bottom.

 

[rb1957]

@Brian ... of course I realise that there is an off-setting motion, and so in a frictionless ideal world with a perfect set up there'd be no losses (and no net work). However in the real world there are always losses (and imperfections). Any, and every, time you do work there are losses. In this case you're doing work (lifting the chain) so there are losses there; and I'm certain that you don't recover 100% of the nett work done on the down-going side, so more losses.

another day in paradise, or is paradise one day closer ?

 

[BrianPetersen]

The chain would have to be very heavy compared to the load in order for any such differences to be meaningful.

I have a 200 hp motorcycle with a chain drive. In neutral, I can spin the rear wheel and its associated chain drive with one finger and that includes whatever bit of friction is associated with the brake caliper, the wheel bearings, the output shaft seal of the gearbox, and whatever bearings are inside the gearbox that spin with the output shaft.

 

[rb1957]

ok, consider adding a vertical chain-set, so that the diagonal is accomplished by two components, horizontal and vertical. still no (not small, but no) change ??

another day in paradise, or is paradise one day closer ?

 

[JohnRBaker]

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[rb1957]

no, I don't think we've strayed into the realm of PM ... but it is "other world"ly enough to suggest that output torque = input torque; the 2nd law of thermodynamics ... "you can't break-even".

another day in paradise, or is paradise one day closer ?

 

[Compositepro]

The simple and best answer is:

No, there is no difference between the two configurations.

 

[rb1957]

I disagree

another day in paradise, or is paradise one day closer ?

 

[BrianPetersen]

In what way?

Friction because of going over extra rollers and bending the chain elements (which have internal friction) more times? Sure.

In the idealized frictionless world? The forces all balance. They MUST.

 

[rb1957]

"The forces all balance. They MUST." ... of course, so long as you include all the forces ... all the small friction forces, all the inefficiencies due to chain slack, etc, etc. But not all forces are doing productive work.

At a fundamental level, the inclined chain-set is doing more work than the horizontal one ... not much, but more.

At a fundamental level, the inclined chain-set is equivalent to a horizontal one and a vertical one.

Say you had two horizontal chain-sets, aligned opposite to one another so that the output shares the same axis as the input. You are not going to get 100% of the input torque at the output ... you CAN'T.

This has been "fun", but now we're just repeating our positions.

another day in paradise, or is paradise one day closer ?

 

[Compositepro]

"At a fundamental level, the inclined chain-set is doing more work than the horizontal one ... not much, but more."

I do not think so. Everything is symmetric (what goes up must come down) so gravity has no different effect in the two cases, even though the effect of gravity is insignificant in the first place. Why do you think there is a difference?

And you have not addressed the time dilation effect of the chain moving at differing velocities above and below the sprockets.

 

[rb1957]

the amount of work done to lift something is more than the work released when you lower it ... due to losses.

and I don't think the problem leaves the Newtonian world, but if you want to include relativistic effects ... "fill your boots".

another day in paradise, or is paradise one day closer ?

 

[Compositepro]

There is an equal amount of of net lifting in both case.

This discussion takes a very simple question and just introduces unnecessary and confusing information that not does not help the OP the slightest bit.

 

[jamdaaman]

Thanks for all the answers.

So what I can take that there is a difference however it is negligible.

I appreciate all the comments. Thanks