crank bhp to rwhp losses

This is often quoted as a number somewhere around 12%. I have long wondered if that could be true, given the heat that would be generated by such losses, especially if you consider the HP outputs of modern MC engines. Is the 12% figure just a way of explaining why many engines do not put out there "brochure horsepower" as Phil Irving called it?

I found this interesting bit of info via Roland Pike, the BSA Goldstar development man. Roland and his coworker in the BSA test department found just 2% power loss in high gear. This seems more reasonable than the 12% -15% often stated today. How much power loss should there actually be in a strong shaft running on two sturdy roller bearings bathed in oil, plus the primary chain, also run in oil?

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Worntorn, the excerpt you provided above only discusses gear box loses. There are also primary and secondary chain drive losses as well as the tire rolling resistance.

As a swag example, if we use 3% loss for rolling resistance, primary chain drive and secondary chain drive and leave the gear box at 2% loss we calculate:

1 - (0.97x0.98x0.97x0.97) = 10.56% drive line loss which is a reasonable number.

Since most of these components are wagging in the wind they get pretty good cooling so the heat dissipation may not be that apparent. There are also noise and vibration pathways for the energy losses to travel.

Since only you and Glen have posted here, I fail to see where I have said ANYTHING ??? !!!
Of all the things I have lost, its my brain that I miss the most ?

Apologies accepted, send $$$....

Corrections made. Somehow I made the connection. Apology.

Just send $$$? What about lawyers and guns?

My dyno says about 10%. Jim

Damn, I pulled those numbers out of my major pore (from recollection) ................. and was off by 0.56%.

I think I will have a(nother) home brew.

If I understand his description properly, they connected a short chain to the engine crankshsft and measured output, then connected a short chain to the output sprocket of the gearbox and measured outputs in various gears and got 2% loss in direct drive.
So they included the primary chain loss in the transmission output test.
First test, one chain, second test two chains plus gearbox.

Glen

Their indicated measurement of crankshaft power (first measurement) would be lower than actual crankshaft power by around 3% since their measurement is through a chain drive at 3% loss. Lock up (top gear) on the Norton gear box should really take little to no power so more or less 0% loss; that leaves the rear chain and rolling resistance, both at an estimated 3% each.

The point is, from crankshaft to tire patch on the rolling road dyno is around 10% power loss.

Ugh its meaning-less to use percentage of drive train drag unless the shaft power is known for each state of an engine rwhp dyno'd. Comnoz nailed down AMC+primary total drag as less than 6 hp but more than 4 hp. So its about 10% for a 50 hp engine but only 5% of a 100 hp Maney engine even with idential drivetrain. TTI tranny has more mass to accelerate but its got needle bearings instead of plain bushes so may have less drag than quaint AMCs. If an eletctric motor put in place of engine then wattage per axle rpm would give pretty accurate report of power drag to plug in equation to calculate what percent it is in each tested engine.

No numbers but I think this will be an issue where belt drive will win over primary chain.

Imagine a chain rotating over two sprockets. Centrifical force is going to want the chain to move in a circular motion. But the sprockets are constraining it to move in an an oval shape. Energy is spent doing this - and a chain is heavy.

Then imagine a belt doing the same thing. It is lighter and less energy is required.

So losses with a belt could be significantly less I think. (Just noticed. This thread is next to one on belt drive failure . I use a dry belt drive (with replacement each season and inspection each meeting) on my race bike but chains on my street bike )

On a related subject in the early 1950s, NSU (arguably the worlds leading motorcycle 4 stroke engine designers at that time) did a large number of experiments to determine the percentage of energy losses from the different components of 4 stroke engines. (From memory rings scored pretty high). But I have searched and cannot find the published results !! :-(

johnm said:

No numbers but I think this will be an issue where belt drive will win over primary chain.

Imagine a chain rotating over two sprockets. Centrifical force is going to want the chain to move in a circular motion. But the sprockets are constraining it to move in an an oval shape. Energy is spent doing this - and a chain is heavy.

Then imagine a belt doing the same thing. It is lighter and less energy is required.

So losses with a belt could be significantly less I think. (Just noticed. This thread is next to one on belt drive failure . I use a dry belt drive (with replacement each season and inspection each meeting) on my race bike but chains on my street bike )

On a related subject in the early 1950s, NSU (arguably the worlds leading motorcycle 4 stroke engine designers at that time) did a large number of experiments to determine the percentage of energy losses from the different components of 4 stroke engines. (From memory rings scored pretty high). But I have searched and cannot find the published results !! :-(

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Although in the test done by Roland Pike he only finds a total of 2% loss in the primary chain and transmission shaft, it does seem that a belt might cut losses a tiny amount. According to Bob Newby, on the question of vented or non vented primary for a belt, his answer is. "A belt will always run cooler than a chain on the same primary".
Less heat generated indicates less energy loss.

On the question of centrifugal force, that gets tricky. We were shown early on in Physics that centrifugal force , a force away from the centre of a rotating object, is a non existant force. The proof is evident when the rotating object is released. It doesn't fly away from centre, instead it travels in a straight line on a tangent from it's point of release. This is how David took out Goliath!

But it does take energy to make the heavy chain reverse it's direction over the sprockets.
Glen

The old Brit (and many other) bikes had that efficient direct top gear, but the lower gears were sort of doubly indirect, transmitting drive to the layshaft and then back to the sleeve gear.

The same drive train will have same drag loss no matter what power is turning it so total drag factor per rpm remains constant but the percentage of engine power will change with every engine and every change on each engine. Belt drive has some less maintenance and less mass inertial advantage but less drag is not one of them. Lube in chain is mainly to flush internal produced and external induced grit out to reduce wear but does not reduce friction but adds friction d/t oil shearing though can help spread heat and many oil layers help cushion combustion spikes. Belts therefore transmit more shock loads than oiled chain. Going by couple decades of Norton power reports and recent summary by comnoz implies we can use 4.5 hp drive train loss at peak power/rpm to add back to rwhp for shaft power bragging rights.

Is belt more efficient than chain? Realize peddle freaks can tell if their water bottle or hair is not aligned well.
http://www.bikeradar.com/us/road/news/a ... ter-36074/
According to Jason Smith at Friction Facts, the answer is no. By his measurements, a conventional chain drive consumes 2.92 watts on average, while the belt eats up 3.93 watts. Although the difference is just 1 watt – not enough for most people to care – this works out as a substantial 34.6 percent.

hobot huhu or honest facts?
http://www.borgwarner.com/en/enews/Asse ... 202012.pdf
Conclusions Chains are often the best solution for timing drives due to:
 Minimized Package
 Optimized Efficiency
 Robustness Against Dynamic Instability
 Proven Long Term Field Durability
 Proven Adaptability Across Multiple Variants

save hu huing hobot on real reason-function of lube in chains - notice no mention of friction reduction just grit flushing for less wear and maybe secondary heat conduction away but can just a well carry more engine heat into chain, which is more what happens in Norton primary. Peel rear drive chain got hotter faster oiled than dry, but who would believe it here. .

There is mention in this article of significant drag reduction using thinner oil but no dry chain comparison.
http://www.machinerylubrication.com/Rea ... lubricants
Need for Lubrication
Chain lubrication is needed mainly to slow the wear between the pins and bushings in the chain joints, to flush out wear debris and foreign materials, and to smooth the chain’s engagement with the sprocket. Additionally, lubrication may be needed to inhibit rust and corrosion, to carry away heat, and to cushion impact forces.

hobot and others have tested dry vs oiled final drive chain to know that if not flooding chain with constant bath or splattering constant effective drip like factory oiler then mainly wasting time money and environmental pollution than anything else. To contest my statement just reveals common sense ignorance on chains.

Importantly, both chains have stiff links, those of the dry lubed chain being less obvious because it is fitted to a fixed wheel bike and cannot articulate to the same degree between sprocket and chainwheel. However, the dry-lubed chain ran much more smoothly afterwards with no “gritty” feel and even without the further application of lube soon freed off. The wet-lubed chain felt awful and needed a good clean before it would run smoothly.
Read more at http://roadcyclinguk.com/blogs/davids-b ... vQAVV8T.99

Yeah, maybe.

Except not a lot of flushing occurs in a sealed chain, but lube is still used, in fact it keeps the chain alive. Pretty sure it reduces friction between moving parts as well.

Glen

We are free to believe in what ever Glen but main benefit of sealed chain is the grease can flush the internally produced metal grinding grit out of interfaces and keeps external grit out, otherwise it adds drag and lube shearing and rubber seal rubbing heat. Still so little loss compared to power driving it its mainly academic Tribology detail vs the benefit of cleaner low or no maintenance chain - which benefit is slightly interfered with by using solvents like wd40 or detergent for clean looks as tends to seep into links to dilute and wash out the grit flushing trapping grease. I have a new 520 chain to use up on next Peel but plan to buy a spool of plain chain as more cost effective d/t similar chain slackness showing up in sealed or dry chain on same mileage. Both types of chain get about 8000 miles before able to lift 1/3 out of valleys but I usually extend to 10-12K miles slowly reducing my throttling to ease teeth wear. I doubt many but Andy the Chain Man would replace at 2% stretch as all references say past limit of manufactures wear life. hobot has tested this over some years but free to double check yourself.

Btw I treat snowmobile racers that reviewed me on the tract slinging outward over 100 mph and told they modify the track supports to let the track assume a more wheel like round shape.

worntorn said:

Although in the test done by Roland Pike he only finds a total of 2% loss in the primary chain and transmission shaft,

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As recently previously commently somewhere here, Joe Craig (?) (Norton Race Shop) had commented that oiling the chain to the jackshaft immediately just prior to a dyno test produced 2 or 3 bhp more. That sounds like a lot more than 2%. And is still not going to make the chain frictionless....

In Sport Bike Performance Handbook by Kevin Cameron he states that "each mesh of gears, and each chain drive causes a typical loss of 2-3 percent"

Assuming we are running a rolling road dyno in third gear and accounting for the rolling resistance at 3% power loss the 2-3 percent calculates out to a 8.7% to 11.5% power loss which averages out to 10.1%.

If we assume the gear box is 100% efficient in top gear (no power loss) we get 6.8% to 8.7% power loss.

In my opinion, these are all somewhat ideal and so dependent upon chain condition. Over tensioned, under lubricated and/or dirty chains - your results will vary dramatically.

A fair median estimate is 10% loss between crank bhp and rwhp.

Dances are you stating that by using yours or anyones percentage figures means a 100 hp road bike would expect to loose 10 hp to drive train on dyno while a 1000 hp on same dyno would loose 100 hp?

I do not think you really think that some how the same drive train and tire on dyno would suddenly require 90 more hp and its excess heat just because bigger engine could spin accelerate it better. Got me stumped as kid learning about thermos bottles keeping some things cold and others hot, how do it know? How does the drive train know its got to develop more resistance with a bigger engine? How does drive train develop different drag factors? Going by percentages is just convenient rule of thumb guesimating when not actually measuring drive train drag in fixed units like watts or hp.

hobot said:

Dances are you stating that by using yours or anyones percentage figures means a 100 hp road bike would expect to loose 10 hp to drive train on dyno

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Yup, as is Kevin Cameron.

hobot said:

while a 1000 hp on same dyno would loose 100 hp?

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Yup; but it would probably go BOOM first and destroy the drive train. See below.

hobot said:

I do not think you really think that some how the same drive train and tire on dyno would suddenly require 90 more hp and its excess heat just because bigger engine could spin accelerate it better.

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A 1000 hp scenario would require substantially heavier chains and gear and the loading (and likely speed of components) would be significantly greater. It scales up.

hobot said:

Got me stumped as kid learning about thermos bottles keeping some things cold and others hot, how do it know?

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Explains a lot.

hobot said:

How does the drive train know its got to develop more resistance with a bigger engine? How does drive train develop different drag factors? Going by percentages is just convenient rule of thumb guesimating when not actually measuring drive train drag in fixed units like watts or hp.

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The drive train "knows" through a little magical thing called coefficient of friction. This is primarily within the pin articulation. Work to bend the chain (into the sprocket) is a function of this coefficient of friction and the tension on the chain. More tension means more work. More tension for a given speed means more power into the system and more power lost to the chain by some percentage (which is a function of coefficient of friction).

Is it fair to say that when you increase the power you are either increasing chain tension or speed or both. So greater tension at greater speed (more overall power) will require doing greater work on the chain at a greater rate (power loss)?

The above is a bit of a simplification as there are issues as the chain speed increases there are centripetal forces increasing tension on the chain.

A 1000 hp scenario would require substantially heavier chains and gear and the loading (and likely speed of components) would be significantly greater. It scales up.

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OH alright Dancer I will put out the light in the old lamp I pulled out the lake and reduce hp to only twice as much say 200 but sticking to my story > there is essentially same drive line drag factor regardless of the power turning it till distorting like you say, which is completely different situation than your misunderstanding of chain tension vs its efficiency till breaking of course. Chain friction pin on plate will some what increase but there is just not much surface translation speed in the links, especially the loaded ones so what would matter more if over powered would be shaft bending binding in bearing supports. If Kevin was reporting race bikes of similar class power plants then its valid to speak of percentage loss per item as hp will all be similar but put a Norton on same dyno and fat tire will skew computing real shaft power. Anyway please never say you learned your current power transmission concepts form hobot. Safe Journeys and soft landings.

http://forums.tdiclub.com/showthread.php?t=75062