Drivetrain Power Loss

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DangerZone

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sorry, you missed Billskis' point: there is no way a transmission set-up on a bike (or car/truck etc) can have more than a few % of power loss. There is simply no capacity to shed that generated heat without a cooling circuit and forced cooling. The only transmissions that do have forced cooling are automatic transmissions and some heavy-duty pullers. Most electric kettles are 2.4kW, I use that often to get the message across about heat energy and power. Having several of those kettles in your transmission system would cook the whole lot in no time.
Billski's point: a few % of power loss - all convert to heat (only 1% to 2% losses).
My point: a lot of % of power loss - some convert to heat others are different (two figure % losses).
No, I am not missing that some losses turn to heat. Am I missing something?
 

AdrianS

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Ok. According to your experience, do you think the same dynamometer could be so inaccurate to read 10% to 20% power difference for the same bike which has gone through a modification or engine/drive conversion?
No, the same (chassis) dyno run under the same conditions should be repeatable to within 1% percent.

I am saying that there are a lot of inaccurate power figures out there.

The number of times I've had to deal with customers complaining that their dyno is wrong because the measured power is less than their engine builder / tuner claimed is depressing.
 

DangerZone

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Nope. I talked about the highly different power outputs in the second and third paragraphs of post 105, above. Here is some of the source data I found online:

Suzuki GSX1100G

Same base engine, greatly different state of tune. GSXR has much more peak horsepower and at much higher rpm while GSX has a wide torque band for easy riding. Those are tuning choices made to suit the product.



I told you what I suspect based upon a long history of both seeing good data and seeing how some will embellish. There could be other sources... The rear wheel dynos could be way off too, but I am leaning more to the engines not making advertised numbers.



I spent 23 years in vehicle powertrain engineering. I do understand this topic. The overwhelming result is that the physics works just like they taught us in school. The folks that ignore that get surprises of the bad kind. I understand very well how horsepower can be lost between crank flange and wheels. I also understand that lost horsepower must show up as some other kind of energy. Take your pick: raised temperatures, sound, light, electro-magnetic effects, lifting weights. You have to put in fancy machines to do everything except convert energy to heat, lost energy goes into heat real easy.

As for dyno measurements being exact, please give it a rest. More than once I have received data from a purportedly well maintained million dollar double ended dyno cell calibrated within the previous three months that showed me over 100% efficiency for transmission stuff in between. One other time I saw test results from a transmission with pinned torque converter and pinned clutches locking the tranny in one gear, and the speed ratio reported from the dynos did not reflect the speed ratio of the gear locked in. We confirmed the gear ratio by hand before and after the test... Dynos are no better than the design and maintenance. They can be crappy indeed if the wrong numbers are put in the calibration files.



So, tell us, just where does this large amount of lost energy go? Even when it propels the vehicle, it shows up as heat by churning the air that the machine just ran through. So what do motorcycles have that they can make power one place, express a bunch less of it someplace else and not be warming something in the middle?

You are not citing your sources and you are making outlandish claims that are unsupportable by even a basic energy balance. Citations are needed...

Billski
Billski, you made a mistake when comparing the GSX1100G and GSXR1100 (same engine, up to 1992/1993) to the GSXR1100 of 1993 onwards (different engine). In 1993 the Suzuki GSXR1100 came out with a new engine and crankcase which was water cooled, the WP stands for water cooling. The water cooling was introduced to dissipate the heat generated by the powerfull engine.

What you are clearly missing is that in shaft driven bikes, not all losses turn to heat. Besides friction losses, there are drivetrain losses, parasitic losses, slippage losses, idling losses and some others specific to this kind of system. The shaft driven bikes have more loss from work. This is elementary physics, energy-power-work. A system needs more enrgy and power to turn a heavier load due to Newton laws.

When people convert their shaft driven bikes to a chain drive, all the mentioned losses are reduced and some losses are even removed from the system. There is no sudden "power increase", it is simple physics, the bike accelerates better because there is less work needed to drive it so the engine runs into higher rpm just like when you accidently hit idle and the engine revs up easy like a rocket.

I respect your experience and I can accept the idea that not all dynos perform the same. I thank you for this input and all other stuff you wrote, which is good and kind of you to share. However, it seems we have different experience in engine drives. Specifically motorcycle drives, and the GSXR engine series which are often used as aircraft engines in conversions.
 

DangerZone

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No, the same (chassis) dyno run under the same conditions should be repeatable to within 1% percent.

I am saying that there are a lot of inaccurate power figures out there.

The number of times I've had to deal with customers complaining that their dyno is wrong because the measured power is less than their engine builder / tuner claimed is depressing.
Ok, so this is my experience too, the same system should be within 1% tolerance otherwise it would be flawed. I would not trust any measurement tool with more than 1% inconsistency.
 

TiPi

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Billski's point: a few % of power loss - all convert to heat (only 1% to 2% losses).
My point: a lot of % of power loss - some convert to heat others are different (two figure % losses).
No, I am not missing that some losses turn to heat. Am I missing something?
Well, if the losses don't turn into heat, what do they turn into??? Noise? Vibration? That would be a miniscule amount of the total power. 99% of mechanical transmission losses turn into heat, and that heat needs to be removed. If a shaft drive bike would be only 80-90% efficient, you would need to remove 10-20% as heat! The whole drive train would be glowing red hot after a run up a mountain.
I had a couple of BMWs with shaft drive. The rear wheel hub (angle drive & reduction) got max of 70-80deg C after many hours of cruising in 30-35deg heat.
 

Pilot-34

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Ok, so this is my experience too, the same system should be within 1% tolerance otherwise it would be flawed. I would not trust any measurement tool with more than 1% inconsistency.
Lol you may have to give up flying I’ve never seen a fuel gage in a small plane that I would trust to be accurate to 1%.
 

TFF

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A shaft bike is driving the mass of the drive shaft, coupler and gears along with a direction change in power over a chain. Depending on style swing arm, I bet the wheel is heavier too.
 

DangerZone

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Lol you may have to give up flying I’ve never seen a fuel gage in a small plane that I would trust to be accurate to 1%.
You'd better give up flying if you'd depend on your trust of any fuel gauge without checking the physical amount of fuel in the aircraft tanks. Or at least read a freaking POH (Pilot Operating HAndbook) from a simple Cessna 172 to see that fuel must be physically inspected during PFI (Pre Flight Inspection). Too many pilots trust their instincts instead of simply following common sense.
 

Vigilant1

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Most electric kettles are 2.4kW, I use that often to get the message across about heat energy and power. Having several of those kettles in your transmission system would cook the whole lot in no time.
Must be nice! Here in 120VAC-land, electric kettles, portable heaters, etc typically max out at about 1500 watts.

After ironing my shirt in a German hotel room, I got quite a surprise when I unplugged the iron that I thought I'd turned off. 220VAC is more "impressive" in this regard than 120VAC.
 

DangerZone

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I feel I need to point out that fair rules of debate are part of what we do here on homebuiltairplanes.com
Well, if the losses don't turn into heat, what do they turn into??? Noise? Vibration? That would be a miniscule amount of the total power. 99% of mechanical transmission losses turn into heat, and that heat needs to be removed. If a shaft drive bike would be only 80-90% efficient, you would need to remove 10-20% as heat! The whole drive train would be glowing red hot after a run up a mountain.
I had a couple of BMWs with shaft drive. The rear wheel hub (angle drive & reduction) got max of 70-80deg C after many hours of cruising in 30-35deg heat.
Work.

And other stuff, like I already wrote. It's simple physics.

Work (physics) - Wikipedia
 

Toobuilder

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What you are clearly missing...
Quote of the week right there!

Do you not recognize the credentials and real world experience of the individual your are trying to "school" here?

This is your opportunity to learn a thing or two... But you need to read more and type less.
 

Dan Thomas

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Most electric kettles are 2.4kW, I use that often to get the message across about heat energy and power. Having several of those kettles in your transmission system would cook the whole lot in no time.
That's an awesome kettle you have there. In North America the typical electric kettle won't be more than 1.5kW. The household circuits are usually 110VAC, on a 15-amp breaker, meaning that we can't draw more than 1.65kW.
 

TiPi

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That's an awesome kettle you have there. In North America the typical electric kettle won't be more than 1.5kW. The household circuits are usually 110VAC, on a 15-amp breaker, meaning that we can't draw more than 1.65kW.
The advantage of 230V AC (dropping from 240 to align with the European 220/230 standard), our power points are 10A with 20 or 25A CBs. The 15A outlet has a larger earth pin, A and N are the same. I have power tools rated at 2,400W (garden shredder) and 1,800W (thicknesser, bore pump). My cylinder head flow bench is powered by 2x 1,200W vacuum cleaners off the same plug.
 

Pilot-34

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Excellent. I still own the 1979 chain driven croch rocket Z1000 in mint confition. It starred in an old movie called Mad Max in the 1970s. The chain drive allowed it to get more acceleration and outrun even more powerful shaft driven bikes, on less crankshaft power.

Some Yamaha XS1100 owners made shaft to chain conversions to get more acceleration and power. Just google XS1100 chain drive conversion. There are even companies which produce chain drive conversion sets. Ever wondered why would people go through so much hassle to convert an XS1100 to a chain drive?

http://www.motionlogics.com/contents/media/l_xs1100 chain drive main case 1.jpg
Lol the term Crotch Rocket was coined by “Cycle” magazine in a review of the XS1100.
Sorry but in 79 if you didn’t have a XS1100 you didn’t have a crotch rocket .

I enjoyed pointing out to my son-in-law when he bought a new crotch rocket a couple years ago that that granddad old machine of mine was the original.
Both he and my son who is a Harley guy made fun of that machine but I noticed it takes them about 15 to 20 miles to move it from one side of the driveway to the other must be more fun than you would think !
 

PredragVasic

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If you can't understand why a motorcycle engine can have 156HP at the crankshaft and only 138HP at the rear wheel, that is also fine.[ ...] Shaft drives on motorcycles have huge losses, and all do not turn to heat as you speculated. It is supririsng that you worked in the automotive industry for so long and never had any experience with motorcycle power and torque transmission (losses).
This particular claim seems to be in direct conflict with known laws of thermodynamics. If shaft drives have “huge losses”, and these losses don“t turn to heat, exactly where does that energy go?? The 22hp difference is an enormous amount of energy, so exactly where does it go (because, as we know, it cannot disappear into thin air; it must be converted from the kinetic energy we have at the crankshaft to some other form).

Science isn’t really complicated at all. I’m not a physicist, but this much I remember from the 8th grade physics classes: energy cannot come from nothing, nor can it disappear into nothing; for a closed system, it remains constant (the law of conservation of energy). In our example, some of that energy is converted to sound (a few thousands of a horsepower), but where does the rest (almost 20kw) go? If it is heat, it is massive amount of heat, enough to get the entire motorcycle to red heat. Clearly, something is profoundly wrong with the idea that a simple shaft drive would lose 22hp.
 

jedi

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Sorry, I have seen enough of this back and forth. Both are right to a degree. Yes, all the losses go into heat but the heat is not all contained or easily measured. It does not all show up in the 90 degree gear box.

A high power "Crotch Rocket" on a dyno loses a lot of power to the wheel losses, windage to the tire and spokes for example. That heat will not show up in the bike. Tire flexing heat is largely disipated into the air also. What is the roller (road speed) of a "Crotch Rocket" on the Dyno? If it is 100 mph that is a lot of tire and wheel windage.*

I do not have the automotive experience of others on this list but I do have enough to know that manufacturer published horsepower numbers are not the same as installed power in most cases. The engine on a dyno for engine development and test are generally done without waterpump, or alternator. Automotive engines are not tested with a fan or air conditioner, etc. There are lots of things to suck up power that someplace down the road turns into heat.

Still, it looks like that shaft drive could use a little more development work if it has as much loss as was "measured".

I can see dyno power being measured at a lower gear to keep wheel speed within acceptable limits. Were the "Crotch Rocket" and shaft drive tests done in a side by side direct comparison with the same conditions and accessories or are the numbers quoted taken from unrelated testing? The numbers are not meaningful if they are from unrelated independent tests.

*With reference to post #36 "because, as we know, it cannot disappear into thin air"; These loses do appear and dissipate in the thin air.
 
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Doran Jaffas

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This has got
Before anyone else reads this pack of comparisons and thinks it actually means shafts and gears just waste energy by the ton, let's look a little deeper.

I looked up these bikes. GSX1100G is an upright posture cruising bike with big performance. Engine makes 98.1 hp at 7500 rpm, no rear wheel output in the lists I looked at. And the articles even mention the low max rpm and wide smooth power curve that suits easy riding styles. And it has a shaft drive so you do not have to fuss with keeping the chain lubed and regular replacements of chains and sprockets. This bike is not a canyon rocket, it is intended to be fun, but can be lazily ridden, two-up and go places. Suzuki sold fairings and bags for it so you could travel comfortably on this machine.

Then there is the GSXR1100, a faired sport bike requiring racing posture, and not really intended for more than one lucky individual at a time. Engine makes 156 hp at 10,000 rpm. To do that with the same basic engine means cams, induction, and exhaust tuning all aimed toward maximizing specific output, and usually drives torque way up the rpm band. Yeah, a peaky powerplant. Is this intended for easy riding? Nope. All out performance? Yep. Then the rest of the bike... much more compact set up, clip on bars, racing style fairings, yeah, a place is provided where a second person could ride along, but that is not what this bike is for. Looks more like a road racer than anything else. And you know what, the same spec sheet that says 156 hp engine also says 138 hp at the rear wheel. Somehow it is supposed to lose 18 hp or about 12% getting the power to the road.

So let's do what in the engineering world we used to call the laugh check. Let's see if that makes any sense at all.

First off, yeah, one engine is for cruising on a bike that will go when the throttle is twisted, and the other is intended to absolutely wow the bike geeks at the motorcycle magazines and turn in some impressive lap times at their usual race courses. And the difference shows, one has generous power for all around riding about with a passenger and bags, enough weight and length to make it cruise nice, and a power curve that makes for comfortable riding. The other, well, weight is driven down, the engine power is made at high rpm, and ultimate acceleration, braking, and cornering are optimized like a race bike. So let's not chalk up all that weight difference to excising a couple gear sets and a shaft and replacing them with sprockets and a chain yet. There are a bunch of differences between these bikes besides the final drive arrangement...

Next, do any of you have a concept of how much heat energy 18 or 30 hp is? If we lost 30 hp in a shaft drive system, which has a bevel gear set and CV joint at one end, another bevel gear set at the other, and maybe a rubber or spring isolator someplace, it would be a bunch. How much? splitting it to 15 hp on each end, one horsepower is 746 Watts, that is 11,190 Watts at each end of the shaft. Now let's get scale - a 60 Watt incandescent light bulb disappates about 90% of that 60 Watts as heat in a volume smaller than your fist, and it is too hot for you to hold in your hand. Maybe 50-60 F hotter than your hand. And that light bulb is about the same volume as the front gear set. 11,190 Watts divided by 54 Watts is 207. So that gear set would have to be disappating 207 times the heat of a light bulb out of about the same volume and across about the same surface area as your 60 Watt bulb. An 11000 F temperature rise! Yeah, it is attached to the metal housing of the engine/gearbox housings and will probably disappate heat more effectively so the temp would drop to a red glow instead of a white hot plasma, but still several times the temperatures that oil and seals and even heat treated steel gears and cast aluminum cases will stand. Simply put, exceeding about 1% losses has trouble living at high power.

Now let's look at the GSXR more closely. 18hp is still 12%, which is still an immense amount of heat concentrated on the chain and sprockets, the o-rings and lubricants will disaapear fast if that heat is even half going into the chain and then the air. Maybe some of it is going into the gear box. One or two meshes and four little bearings will use some energy, but we are proposing an order of magnitude more loss than is realistic. That is even a lot of heat lost to tire slippage on the typical dyno, but maybe a decent dyno session does cost a rear tire among other things.

What do I suspect? I think that marketing departments use horsepower of a perfect prototype engine on a dyno with cool air in, big suction on tuned pipes without mufflers, and fully warmed up systems for minimum viscous losses in both engine and gearbox. Maybe they even skip the gearbox. Then independant testers roll a complete motorcycle onto a dyno, fire it, and as soon as the oil temp gets off the peg, they run a couple speed sweep pulls. The engine and gearbox are still warming up, the tires slip a few percent on the roller, and they get a perhaps realistic number for this bike if you rode it fast right out of your garage on a steel roller instead of on flat pavement. Is 18 hp going away in that GSXR's drivetrain and at the tires? I highly doubt it. I suspect most of it was lost between marketing's brochures and getting a whole bike manufactured in volume and to the independant test lab. That's what happens with cars (23 years in the business of automotive powertrains). But losing that kind of power in a couple gear meshes and a cush joint or even on a chain drive? They would burn up the drive systems...

The claim fails at the laugh test level. Widely use engineering approaches are 1% or less loss of rated power per gear mesh or chain mesh. Belts run around 1% losses of rated power too. Well designed and developed systems can run quite a bit lower than 1%. Any system losing 2% per mesh or more is either:
  • Using sliding surfaces (worm gear drives and the like) or;
  • Is intended to self lock if input shaft rotation is lost, or;
  • The design team screwed up big, or;
  • Running really cold (think Antarctic ground vehicles);
  • Combinations of the above.
Billski
This has got me wanting the GSX 1100 all over again. It was a great ride back in the day and still is.
 

Doran Jaffas

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On another note but still along the same lines here...has anyone converted a Honda Goldwing powerplant ?
 
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