Drivetrain Power Loss

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ghostrider

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Re: all inefficiency becomes heat.

technically true, but difficult to measure sometimes. The noise of a gear train isn't heat, at your ear, but eventually dissipates as heat in the larger environment. So there's a efficiency percentage lost that isn't measurable by putting a thermometer on the noisy gear case.

I freely admit I don't know the correct number, percentage of loss here! I can only point out false assumptions.

Not every energy loss is easily measured as heating the gizmo. In the real world, these things exist, work, and don't vaporize when in use. So X kilowatts of lost power isn't all in one place.
Agreed, noise though is not very energy dense. The amount of energy dissipated as noise (which eventually becomes heat) is vanishingly small compared to the frictional heat dissipation.
 

Protech Racing

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Being a little hard on terminology when everyone here knows what he is saying. It’s about loss of energy and there is a disagreement on how much. It’s been a long time since I had a bike. My 73 Yamaha 750 3 cylinder probably waisted a lot of hp in the final drive, where my 92 Honda CBR600F2 was at the height of the horsepower racing wars. Every trick counted. I believe the SCCA stopped people from using motor oil for wheel bearings in the Spec Racer class, because it was an advantage. Gear oil, as necessary as it is , is a power loss. Weight of components are a loss in power, configuration is a loss in power. It all adds up. Quality of manufacturing adds up. Person designing adds up. The math might be right, but the quality is usually not there. Surprisingly, not to someone really building it. There is always a tool, shape, coating that is just not obtainable at whatever price level you are at. Something at a volume of 10-20 a year and has to support a shop is going to trade high tech for it works. Consumer really doesn’t know in general.
My Son won a lot of Kart races with Mobile one engine dripped into his hub bearings, 22# of air in the tires, and a loose chain ,oiled with mobile one engine oil .
The SCCA F4 cars have a Honda leased , spec engine . Some winners have been found to have cut the oil pressure spring to reduce the running pressure and pick up a couple of HP.
Some Mini cars have a solonoid that does the same thing over a certain RPM . reduces oil pressure . gains MPG.
Toyota and others now use 0-16 wt synthetic oil , right , not zero 20 .
 

Vigilant1

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Toyota and others now use 0-16 wt synthetic oil , right , not zero 20 .
I'm sceptical about this trend toward very low viscosity motor oils. The interests of manufacturers are not entirely congruent with my interest as a car owner. Manufacturers want high MPG to meet fleet CAFE standards (or at least minimize their pain) and they want all engines to last through the warrantee period. As an owner who doesn't trade cars often, I want the engine to last at least 300k reliable miles and I don't much care about getting that last .05 mpg. These water-thin oils certainly meet the goals of manufacturers. I know today's engines have tighter tolerance bearings, etc, but I can't help wondering if slightly heavier oils wouldn't produce better films where sliding is occuring, cling a little better to reduce corrosion and startup friction, etc.
P.S. Same thing with bodywork metal thickness. I want a few extra years before it rusts through, would like a little more protection in a crash, etc. 100 lbs heavier is okay, and dip it again in the zinc, please.
 
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Dan Thomas

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Final Drive Unit.
Because it's the last link from engine to output/wheel/propeller.

Or 90 degree gear case.

Both are correct, descriptive, and in common use by the manufacturers.

Differential is a different critter.

I can't apologize for guys on E-bay who use the wrong words. They are in error.
Even the car guys get the terminology wrong. They call the entire axle housing a differential, from wheel to wheel. The differential is the collection of gears, not the housing. The housing just holds the gears, shafts and bearings all in the right relationship.
 

Aesquire

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31%??? ( power loss for shaft drive motorcycle )

I'm not sure how much I'd rely on these numbers. But the comment on replacing a belt is true, even understated.

On my particular bike, availability is... I can order one. The brand is gone, thanks to ( insert rant on bean counter New management decisions, with swearing ) but they are available. Otoh, belt replacement requires a LOT of disassembly. Removing engine, rear wheel, and unbolting the swingarm pivot... & a big pry bar to spread the frame the 1/2" required to slide the belt in & out. Nightmare applies. There's no way to separate a belt, unlike a chain, so it's very labor intensive. ( and in one of those "quirks you hate or love" engine removal is best done with lifting the frame off the engine & working on the frame suspended from above ) The good news is I expect at least 50,000 miles before needing replacement, and maintenance is near zero. I'll go through a dozen pairs of tires by then, at least.

The above may be very important to homebuilder design choices! Belt drives need a clear path to change belts. It's a topological philosophy/math design challenge. Some Low Aspect Ratio designs discussed here, especially offer cool features like a wing/fuselage tip mounted prop with inboard engine. So I'd suggest watching YouTube videos on lawn tractor & motorcycle belt replacement to get a feel for the TOPOLOGICAL NIGHTMARES you want to avoid.
 

TiPi

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These "efficiencies" are simply not possible as the heat generated would be impossible to remove without a dedicated cooling system (even for the belt drive).
This is straight from the horses mouth (Gates): 2-5% loss on a toothed belt drive. V-belts can be up to 10% depending on slip, but then they have very short lives as the belt gets overheated and will fail.
 

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Aesquire

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I asked a pro mechanic buddy about the question.. He says 3% for shaft drive 90 deg. drives, and that 31% is absurd.

Anecdotal, but agrees with some...
 

DangerZone

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Ok, grand. How do the losses that are not heat dissipate?

Why dont harleys overheat? Really? Is this a serious question?
No. That is a rhetoric question. Google rhetoric or logic.

Your asumption "All loses are heat" has a serious problem with Harleys having a less than 19% efficient internal combustion engines. A Fat Boy has around 50kW of power. If your asumptions were correct, there would be around 200kW of heat losses two feet from a rider's crotch. That would melt the rider's balls, and fry the whole person riding a Harley. I rode Harleys across a couple US States, and my balls are still fine. Just like the balls of many other Harley riders. Can you understand now why most of your conclusions which are based on wrong asumptions simply don't have to be right? No matter how "right" they might seem to you.

Torsional vibrations? Really? What does that generate? Oh, that would be heat. But parts can fail before they overheat, especially if they resonate.
Again, this is your asumption. And this is exactly why people fail at understanding torsional vibrations, inertial vibrations, and vibrations generally. Some vibrations have no heat effect at all. In aircraft applications, this can lead to devastating results in a simple shaft conversion. This is a German site with a very clear document in English demonstrating some vibrations in homebuilt aircraft. I suggest to anyone who want to know more about shaft drives to read this just to get an idea about what one can expect:

http://ibis.experimentals.de/downloads/torsionalvibration.pdf

Re: all inefficiency becomes heat.

technically true, but difficult to measure sometimes. The noise of a gear train isn't heat, at your ear, but eventually dissipates as heat in the larger environment. So there's a efficiency percentage lost that isn't measurable by putting a thermometer on the noisy gear case.

I freely admit I don't know the correct number, percentage of loss here! I can only point out false assumptions.

Not every energy loss is easily measured as heating the gizmo. In the real world, these things exist, work, and don't vaporize when in use. So X kilowatts of lost power isn't all in one place.
This is exactly the problem of this whole thread. People usually try to calculate the exact numbers so there would be least losses and unexpected issues, and I just follow this practice. You don't calculate, but you are sure that the methods I showed/linked are false. This leads you to a blind alley, this is not a zero-sum game or zero-sum thinking. If you don't read the links I provided and don't try to understand, you will still be at the same spot - unable to calculate the correct number. So if you already went through so much time to write on this thread, why skip the good read and see how this can be calculated? This is also rethoric, I hope you understand.

I just came back to see if there's anything interesting or new to learn here, but the "torsional vibrations would be heat" stories don't seem to be promising.
 

ghostrider

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Well, you are assuming that said Harley rider is riding full throttle the whole time. If he were the result may very well be the one that you describe.
 

Dan Thomas

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Your asumption "All loses are heat" has a serious problem with Harleys having a less than 19% efficient internal combustion engines. A Fat Boy has around 50kW of power. If your asumptions were correct, there would be around 200kW of heat losses two feet from a rider's crotch. That would melt the rider's balls, and fry the whole person riding a Harley. I rode Harleys across a couple US States, and my balls are still fine. Just like the balls of many other Harley riders. Can you understand now why most of your conclusions which are based on wrong asumptions simply don't have to be right? No matter how "right" they might seem to you.
You're still wrong. Look at this:

1620000367751.png

That loss out the exhaust is actually conservative. For an aircraft engine it's more like 50%. Coolant takes another big chunk, in this case it's the cooling air, whether it's a Lycoming of an LS engine or a Harley or a liquid coolant radiator on any engine. The friction losses are also expressed as heat and often show up in an oil cooler.

Most folks totally underestimate the heat lost out the exhaust. The old WWII bomber pilots knew it, as did the piston airliner pilots; they could see the exhaust stacks at night and would set their mixtures by the length of the flame leaving them.


You don't see it with cars because of the long length of exhaust piping that cools it. Same with most Harleys. Cut a Harley's stacks off under the footpegs and see some flame.

Blaming efficiency losses on vibration is poor science. All losses end up as heat.
 

Aesquire

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so out of the 25% left, how much is lost in a 90 deg. gear drive unit?

Re: testicular heating

On my bike there's a massive welded frame member between my tender bits and the rear Valve cover. The valve covers get hot enough to give you a first degree burn. But they are not where the heat is mostly lost from, that's a few inches closer to the crank where all those cooling fins are, and they can raise blisters after a long ride in hot still air in a traffic jam. ( been there ) While there was a fad a few years ago to make bikes more aerodynamic by routing the exhaust system under the seat and out the back, I suspect the buyers at least temporarily removed themselves from the Gene Pool by overheating the seat.

And the exhaust pipe on my bike can start fires. I'm careful when I park on grass that it isn't too close to the pipes. High dry grass will catch on fire. ( I've lit cigarettes off my buddy's Norton Comando pipes )
 

mcrae0104

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If they hang low enough to be in danger, maybe you should see a doctor about that.
 
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