| Author |
Message |
    
Joey
| | Posted on Friday, February 07, 2003 - 10:28 am: | 
|
I'd like to know more about this cush drive thing, too. I get the idea, but can someone give me details on what it is? Really, I want to know. |
Mikej
| | Posted on Friday, February 07, 2003 - 10:41 am: |
|
If you look at some chain-drive motorcycles they may have rubber cushioning to smooth out the interplay between the sprocket and the wheel hub. I believe this is another form of cush-drive thinking. Takes the sharp/harsh edge off of the power impulses. |
Hootowl
| | Posted on Friday, February 07, 2003 - 10:43 am: |
|
I was also unaware that the XB has a cush drive.
Joey,
A cush drive, as most Japanese sport bikes are equipped with, is a rubber spline (I say spline for lack of a better term) that connects the rear sprocket to the rear wheel. The rear hub is hollow, and the rubber spline fits into it.
I don't feel like I'm 'splaining this very well. |
Joey
| | Posted on Friday, February 07, 2003 - 10:55 am: |
|
So, the XB, having a belt instead of a chain, could be considered as having a cush drive, as mentioned earlier. The kevlar/rubber belts should have some give. That would mean my Blast! has a cush drive! Or, are we reaching here? |
Davegess
| | Posted on Friday, February 07, 2003 - 11:34 am: |
|
The older chain drive Buells had cush drive donuts in the rear sprocket mount. They were some sort of hard plastic thingies, not at all rubber like.
Dave |
Rick_A
| | Posted on Friday, February 07, 2003 - 01:37 pm: |
|
I didn't know that either.
Joey...the belt wouldn't be considered a cush drive in itself...but it serves about the same purpose. |
Sparky
| | Posted on Friday, February 07, 2003 - 01:38 pm: |
|
XB cush drive = sprung clutch basket.
Sparky |
Steve_A
| | Posted on Friday, February 07, 2003 - 01:48 pm: |
|
A Gates belt might be a little softer than a chain (as measured in amount of elastic stretch, say, per 1000 pound load.) But it hardly makes it a cush drive. A cush drive is essentially a spring added to the power transmission path to soften peak loads. Japanese engines typically have cush drives in the clutch hub (steel springs) and at the rear wheel (rubber biscuits). Cush drives can contribute to drive-line lash, and have to be well engineered because you start to encounter resonance effects if they're not.
Harley historically ignored cush drives, and has had to over-design its gearbox to compensate. The first big Harley to have a primary cush drive -- I think -- was the first Sturgis with the Gates belt primary, and that was required to keep the primary belt alive for awhile. But Harley has caught on, and its new engines all have some type of cush drive. The XB9 has a primary cush drive -- built into the front sprocket, I believe, and you can assume all future Buells will have something that reduces driveline shock loads.
Large flywheels can actually increase driveline shock loads, particularly if you do something stupid like downshift from fourth to second with the clutch lever pulled in and then let it snap out. Buell peak driveline loads are actually less than Harleys because of the lower intertias in both crank and rear wheel, and the lighter weight of the bike. |
Imonabuss
| | Posted on Friday, February 07, 2003 - 07:51 pm: |
|
My understanding is that cush drives in rear wheel = more unsprung weight (a Buell no-no), hence the reason for using a primary cush drive in the XB. |
Blake
| | Posted on Saturday, February 08, 2003 - 08:43 am: |
|
Someone show a picture!
When will Buell give us a slipper clutch? ![:]](http://www.badweatherbikers.com/buell/clipart/proud.gif) |
Jrh
| | Posted on Saturday, February 08, 2003 - 11:11 am: |
|
How much unsprung weight would be in a rear hub cush drive?How much does 3.5 quarts of oil weigh?
I'm confused. |
Benm2
| | Posted on Saturday, February 08, 2003 - 11:16 am: |
|
The oil's near the pivot, where it has less of an effect on unsprung weight. The cush drive (would be) right in the wheel, except its not there either, apparently |
Imonabuss
| | Posted on Saturday, February 08, 2003 - 01:36 pm: |
|
BenM2 is correct about the location. Weight at the swingarm pivot is not unsprung, weight halfway back from the pivot counts as half unsprung, and weigh at the rear axle counts as fully unsprung.
Also, oil is a liquid, and one of some viscosity, therefore it does not act the same as solid unsprung weight. The issue with unsprung weight is the ability of the suspension to return the wheel back to the ground after it is driven off the ground by an impact. When the shock pushes the XB swingarm back down the oil floats up off the surface and virtually doesn't act as unsprung weight at all. Also it acts like a damper by damping out the bounce of the swingarm. According to Buell engineers the real value of this system is even greater than it first appears.
Another interesting oil related thing I was told is in regards to the cooling fan that runs on after the bike shuts off. According to these guys, one of the greatest damaging effects on motor oil is when the engine shuts off hot and the oil is no longer circulating. By continuing to run the fan, the engine is continuously cooled off instead of heat soaking, and thereby the oil is kept fresher. Running a fan on a water cooled engine only cools the water in the radiator, whuich is no longer circulating, therefore there is no cooling to the oil.
Interesting stuff, isn't it? I wish more of this stuff would come out in the technical magazine articles on the bike. Steve A. seems to be one of the only magazine guys who has delved much into the engineering on the bike; I wonder why more don't?
When they do do tech articles it's negative BS stuff like the Motorcyclist article that had the chassis review by a guy from Computrack that said the chassis geometry couldn't work...right, it's only significantly better than a 748, which is a darned good handling bike.
How do you all think the XB technology would have been received by the press if it was on a Honda? Oh, that's right, we Americans are technical idiots, right? |
Court
| | Posted on Saturday, February 08, 2003 - 02:55 pm: |
|
>>>Americans are technical idiots, right?
That's an inaccurate statement.
The problem I submit is the way American motorcycle technical achievement is reported, not the quality of the work. Think of Beethoven played on a crystal radio set from Heathkit.
Over the years, I've come to discount most the American magazines technical opinions. I've never arrived at the reason "why"; some argue ad revenue, loyalties, even how ritzy the press intros are. Fact is there are few facts.
I agonized while one American magazine knowingly and intentional destroyed a Buell and "created" a woe is us tale of innuendo and sleight of word.
I've let many of my subscriptions lapse and view most domestic rags a picture books and venue appropriate material for a bathroom.
Many of these low paid non-engineer moto-journalists fail to ASK and instead simply look and write from the hip. I'm convinced there are few among there number capable of truly appreciating the skimpily and effectiveness of some of the Buell systems, as intuitive as those systems may be. If it ain't the V-Rod engine or water cooled they don't want to talk about it.
The Buell XB has done more to raise the engineering bar than any motorcycle in my time. It alone incorporates more simple, yet advanced, technology of any motorcycle available to the public. Yet, the journalists seemed to be poised in the shadows waiting for a glitch to occur. It's easier to yell, "Aha, recalls, we knew it" than it is to appreciate simple and elegant systems that work.
I predict that time will be the ally of the XB platform. Owners, now getting some miles on the bike, report a love affair that is flourishing, not diminishing, with the passage of time and miles. My sincere hope is that by the time a sufficient sample size of quality data is in hand that the XB will have silenced it's detractors by posting some unheard of quality numbers.
I spent the day yesterday with 3 acoustic engineers visiting from Europe (www.bksc.co.uk)who had never heard of a Buell. As I shared background, literature (Thank you Dave Stueve for providing Buell sales material) and information these guys were amazed and will be heading "straight away" to check out the Buells on their return to London on Monday.
It fascinates me that the "clean slate" well educated engineering mind is absolutely in awe of what Buell engineers have done, as by the way, in the European press.
I hope the talented folks from Buell (and it's be inaccurate, given the diversity of Buell talent, to call them "American Engineers) stay the course, follow their passion and "the light".
The current line of Buell XB's are destined to make motorcycle history.
Court |
S320002
| | Posted on Saturday, February 08, 2003 - 10:56 pm: |
|
Amen.
G |
|
