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Old 03-02-2012, 07:46 AM   #1561
precarious
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Quote:
Originally Posted by Portchy View Post
At this point I am probably the real weak point in the system off road
I hear that. My Strom has suffered a fair amount of "User Error" related scuffs and bangs.
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Old 03-02-2012, 08:16 AM   #1562
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Originally Posted by littlefield View Post
'A shaft drive delivers the power via a single-sided swingarm which will reduce output in the neighborhood of 15-20%.'
Reduce output? Surely that's not the gear losses. Must be the ratio.
Yep, parasitic. 110 to 115 to the rear wheel would be on the high end of what to expect.

Sad, in a way, that the desire/need to serve the shaft lovers has essentially neutered any gains they made with the new 1215cc motor.

Here's hoping they use that powerplant in a chain-driven platform as well, where it can really shine.
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Old 03-02-2012, 08:56 AM   #1563
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Quote:
Originally Posted by littlefield View Post
'A shaft drive delivers the power via a single-sided swingarm which will reduce output in the neighborhood of 15-20%.'
Reduce output? Surely that's not the gear losses. Must be the ratio.
Power losses in a gear assembly are always related to mechanical losses. Power in different transmition ratios is always constant, what changes is the momentum aplied on the secoundary cog/wheel/whatever.

Imagine that you are pedaling on a bicycle, transmitting 1KW to the cranks. If you are on the granny gear at front and the 32t cog rear you are apling 1KW (ignoring mechanical losses) to the rear wheel. as well as a reasonably big momentum. If you change to the big chainring at front and the 11t cog rear you'll be apling the same 1KW to the rear wheel, only with a much smaller torsional momentum.
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Old 03-02-2012, 09:20 AM   #1564
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Originally Posted by Bundu View Post
nope, a shaft drive is only about 80% efficient - think chain is 90%
They must be using some crappy gears. One extra right angle to get out of the transmission and then a spiral bevel at the rear.

Gear Efficiency Comparison Table

NoTypeNormal Ratio RangeEfficiency Range
1Spur1:1 to 6:194-98%
2Straight Bevel3:2 to 5:193-97%
3Spiral Bevel3:2 to 4:195-99%
4Worm5:1 to 75:150-90%
5Hypoid10:1 to 200:180-95%
6Helical3:2 to 10:194-98%
7Cycloid10:1 to 100:175% to 85%
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Old 03-02-2012, 10:52 AM   #1565
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20% overall loss in a modern shaft drive system sounds like a high estimate to me. I'd guess it would be more like 12-14%, compared to perhaps 7-9% for a brand-new, well-lubed chain. Unless your chain maintenance is rigorous, you're, on average, not going to do that well with the chain, so the actual advantage of the chain is probably going to be less than the 5% between these numbers, perhaps 3-4% on average. On a 120 RWHP bike, that's 4 hp or so. Not insignificant certainly, but not a deal breaker either.

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Old 03-02-2012, 11:41 AM   #1566
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Originally Posted by markjenn View Post
20% overall loss in a modern shaft drive system sounds like a high estimate to me. I'd guess it would be more like 12-14%, compared to perhaps 7-9% for a brand-new, well-lubed chain. Unless your chain maintenance is rigorous, you're, on average, not going to do that well with the chain, so the actual advantage of the chain is probably going to be less than the 5% between these numbers, perhaps 3-4% on average. On a 120 RWHP bike, that's 4 hp or so. Not insignificant certainly, but not a deal breaker either.

- Mark
Thing is, with a modern chain, there's very little power delivery delta between a "well maintained" and a neglected chain. Even if the chain is more loose than it should be, it's still a direct mechanical connection and once it's fully loaded and in a steady state, losses are barely worse than with a properly tightened and lubed chain. For that matter, external lube has almost no impact on efficiency, just durability...modern chains are internally lubed, you know.

15-20% is still a realistic loss percentage on a shaft drive. Part of that is the extra gearing needed to couple the crank to the drive shaft and then to the rear hub, but the biggest parasitic losses come from weight. The mass of a shaft drive and associated gearing is many times greater than a chain drive, there's simply no getting around that.
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Old 03-02-2012, 12:09 PM   #1567
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Quote:
Originally Posted by markjenn View Post
20% overall loss in a modern shaft drive system sounds like a high estimate to me. I'd guess it would be more like 12-14%, compared to perhaps 7-9% for a brand-new, well-lubed chain. Unless your chain maintenance is rigorous, you're, on average, not going to do that well with the chain, so the actual advantage of the chain is probably going to be less than the 5% between these numbers, perhaps 3-4% on average. On a 120 RWHP bike, that's 4 hp or so. Not insignificant certainly, but not a deal breaker either.

- Mark


Old school bicycle racers will tell you that a well oiled chain makes a tremendous difference in power output.
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Old 03-02-2012, 12:22 PM   #1568
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Originally Posted by PirateJohn View Post
Old school bicycle racers will tell you that a well oiled chain makes a tremendous difference in power output.
But they don't use O ring chains on bicycles do they ? I think that's the key when talking modern motorcycle chains.
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Old 03-02-2012, 01:11 PM   #1569
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Originally Posted by Mercury264 View Post
But they don't use O ring chains on bicycles do they ? I think that's the key when talking modern motorcycle chains.
I have no idea, just that there can be significant friction in a chain drive train, so the implication that a driveshaft sucks up even more power has plenty of merit.

And I think that what you are saying is that a modern motorcycle chain works better than the old chains, which makes sense.

Another thing, while we are on the subject, is that although modern road bicycles have a simple automatic chain tensioning device in the gear change mechanism, track bicycles are the old style bikes with a single gear in the front and a cog in the back and you adjust chain tension by sliding the wheel back and forth and tightening it with a wrench (obviously something that shouldn't be done while riding). There is a point of least friction where the chain is slightly loose but not so floppy that it will come off while you are racing. A chain that it too tight really binds things up.
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Old 03-02-2012, 01:14 PM   #1570
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shaft losses

Check out this site, they make ecu chips for boxers. According to them, combined transmission and final drive losses are of the order of 10%. However, they use this estimate without any further explanation.
http://www.bbp.homepage.t-online.de/r15gs2e.htm
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Old 03-02-2012, 01:26 PM   #1571
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Originally Posted by PirateJohn View Post
I have no idea, just that there can be significant friction in a chain drive train, so the implication that a driveshaft sucks up even more power has plenty of merit.

And I think that what you are saying is that a modern motorcycle chain works better than the old chains, which makes sense.

Another thing, while we are on the subject, is that although modern road bicycles have a simple automatic chain tensioning device in the gear change mechanism, track bicycles are the old style bikes with a single gear in the front and a cog in the back and you adjust chain tension by sliding the wheel back and forth and tightening it with a wrench (obviously something that shouldn't be done while riding). There is a point of least friction where the chain is slightly loose but not so floppy that it will come off while you are racing. A chain that it too tight really binds things up.
That really was my point. I have to think that modern O and X ring chains are much more efficient than the older 'non-ring' chains.
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Old 03-02-2012, 03:04 PM   #1572
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Originally Posted by Croak View Post
....the biggest parasitic losses come from weight. The mass of a shaft drive and associated gearing is many times greater than a chain drive, there's simply no getting around that.
Drivetrain losses are calculated in steady state (not accelerating or decelerating) so I don't see how weight/mass would affect drivetrain losses.

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Old 03-02-2012, 05:14 PM   #1573
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Originally Posted by ray_rev View Post
Yes. 135bhp is good for about 140mph on the bike, afaik. I can't remember from the blurb whether the top speed is limited electronically.
I would think so Ray. With 135 HP on tap ... figure 125 HP at the wheel ... the bike should touch 150 mph if gearing is reasonable and aerodynamics aren't too bad.

Even my DL1000 V-Strom (92 RWHP measured) went a real 130 mph once the 5th and 6th gear elec. limiters were by passed. With limiters working the motor would not rev beyond about 6000 rpm in 5th and 6th gears. De-restricted, it was still pulling at 130 (142 indicated) ... but began to weave ... The Vstrom was NOT stable over 120 mph and I very rarely went over that speed. I'm sure the Tiger 1200 is safer and more stable, with better suspension and a very good chassis ... but still.

Riding on public roads a lot changes once up over 120 mph. I'm too old for that now! But good for crossing Nevada on Highway 50. (bring tires)
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Old 03-02-2012, 06:02 PM   #1574
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Originally Posted by Adv Grifter View Post
I would think so Ray. With 135 HP on tap ... figure 125 HP at the wheel ... the bike should touch 150 mph if gearing is reasonable and aerodynamics aren't too bad.

Even my DL1000 V-Strom (92 RWHP measured) went a real 130 mph once the 5th and 6th gear elec. limiters were by passed. With limiters working the motor would not rev beyond about 6000 rpm in 5th and 6th gears. De-restricted, it was still pulling at 130 (142 indicated) ... but began to weave ... The Vstrom was NOT stable over 120 mph and I very rarely went over that speed. I'm sure the Tiger 1200 is safer and more stable, with better suspension and a very good chassis ... but still.

Riding on public roads a lot changes once up over 120 mph. I'm too old for that now! But good for crossing Nevada on Highway 50. (bring tires)
+1. I hit a GPS 120 mph crossing the desert on my DL1000, and it was SKETCHY! Plenty of pull, but it started shaking its big head around.
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Old 03-02-2012, 11:14 PM   #1575
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Originally Posted by Croak View Post
Thing is, with a modern chain, there's very little power delivery delta between a "well maintained" and a neglected chain. Even if the chain is more loose than it should be, it's still a direct mechanical connection and once it's fully loaded and in a steady state, losses are barely worse than with a properly tightened and lubed chain. For that matter, external lube has almost no impact on efficiency, just durability...modern chains are internally lubed, you know.

15-20% is still a realistic loss percentage on a shaft drive. Part of that is the extra gearing needed to couple the crank to the drive shaft and then to the rear hub, but the biggest parasitic losses come from weight. The mass of a shaft drive and associated gearing is many times greater than a chain drive, there's simply no getting around that.
I really think that 15-20% is a smidge high man. Modern cars with manual trannys have loses in that range or less {many in the 10-15% range}. Modern autos often return loses in the 15-25% range with the lower numbers being econo type cars with tight converters and the higher loses being associated with performance autos with looser converters {higher stall}. As an apples to apples example, most sources put my 04 FJR's hp at roughly 140-145hp at the crank and most sources list RWHP in the 125-130 range. That sounds like 15% to me worst case and around 10% in most cases so,,,, 10-15%. Not alot in argument's sake but it does mean alot in terms of outright power loss comparison. If my 98 Camaro with a 4 speed auto can return 20-25% loss numbers and my old 2000 Firebird with a M6 can return 10-15% numbers I find it hard to believe a modern motorcycle shaft would lose the same much less double?????

But who knows, maybe you are dead on with that 15-20% number but we should find out soon. My guess would be well under that 15%, probably right around 10%. You are absolutely right in that higher rotating mass hurts acceleration{hp} but once again this shouldn't be a huge factor and man,,,,,,, diss ain't no repli-racer and ultimate performance is less important in this class than low maintenance especially considering the miles many will be laying down. In any event, we are only talking what, maybe a 10-15hp difference between the two {chain vs shaft}if that? I consider that more than a worth while trade for no maintenance. I absolutely love the shaft drive on my FJR and my wife's Ascot. The FJR has over 75K miles on it without a single issue. I changed out the oil at around 25K miles for some synthetic and I lubed the pumpkin splines at the same time. Took what, maybe 30 minutes extra to do while changing tires?The Ascot going on 25K and it's going on 30 years old with nary and issue. Maintenance??? I did change the oil in it at around 25 yrs and 7K miles. In contrast, I have averaged a new chain and sprockets every 10-20K miles {just depends on the chain and how much I play} on my DL at a cost of around 150-200$ so each time so I'm looking at around 500$ just in crappin chains so far.

On the other hand, I've had to gear the piss outta the DL to get the off road performance I want and had that bike been a shaftie, that wouldn't have been an option so there are advantages and disadvantages and I and most others understand that. My FJR's gearing is spot on if a bit low but that's Yamaha's fault for not building enough gearing spread and hopefully Triumph will learn that these type bikes really need a nice wide tranny spread. At least a nice tall and lazy OD 6th gear anyway.
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