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Post by bnc on May 25, 2014 18:52:51 GMT -5
Isn't this variator belt slip under load causing the initial higher rpm?
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Post by alleyoop on May 25, 2014 19:57:50 GMT -5
No
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Post by oldchopperguy on May 25, 2014 21:03:54 GMT -5
Yep that is how the variators work, like I said the belts climb the highest at around 40mph and you can easly verify that, then once the intial weight is rolling the rpms start to climb and the speed starts to increase. But again I will say it is not because the belt has climbed any higher it is because now the weight is moving forward and the motor does not need so much power to keep the already moving object. That is why the RPMS climb it is less of a load on the motor and it gets to pump out the rpms now. Then once the speed you want to cruise out is reached you can back off the throttle and it will hold the speed there at much lower rpms. Same with my trike I start off and the rpms climb right around 7200 and as I reach say 50mph I can back off the throttle and I am now running 5100-5200 rpms and cruising at that speed, at 60 it will cruise at 6100--6200. Same with a car you hit the pedal to get to the speed you want then you can back off the pedal and your rpms will drop and cruise at that speed. It takes more power to move a dead weight but once you get the weight moving forward all that power is not needed. I have experimented with my cvt so much I used to only put the 4 center bolts on because I would take it off so much. Then I used to run it without the cover on I got tired of taking even the 4 center bolts off and on. I have tried different gram roller weights different gram sliders, different variators, clutchs, springs, longer belt even cut down a boss. But I always marked my variator to see what was happening to see what the belt was doing at different rpms and where it was climbing or not climbing on the pulley face with what I had in there. Alleyoop
Thank you Alleyoop!
Now, you explained it better than I could... Even after ENDLESS experimentation with the variator on my old Chinese 150... LOL! Oh yeah, I can TOTALLY sympathize with that "leave the dang cover off 'til you get it right" syndrome... HeHeHe. And probably, the larger the displacement, and the more "torquey" the engine, the more this phenomenon seems to exist. No matter HOW it works, I do LIKE it! I'm becoming a BIG fan of the CVT tranny, and even if I could climb onto a regular motorcycle, I believe I'd now go with a big scooter, or one of the CVT motorcycles. Some of this modern technology is finally "getting to me"... LOL!
They are SO "convenient"... but the steady, mundane "drone" of a CVT bike will never quite replace that sweet pop n' cackle from straight-pipes on a hot V-twin as you lazily shift gears... LOL!
Again, thanks for the good explanation. I know WHAT happens, but you know WHY it happens.
Sincerely,
Leo |
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Post by alleyoop on May 25, 2014 21:32:38 GMT -5
Of course I know why it happens , and if you know what happens it should be clear as to why it happens  That is why I said if you understand what happens and what your really doing when you back off and then hit it again you would know WHY it happens. And I can add a BUT to the happening after it happens  Alleyoop |
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Post by bnc on May 26, 2014 2:13:35 GMT -5
Sorry to be the Devil's advocate but straight from the,
IACSIT International Journal of Engineering and Technology, Vol.4, No.4, August 2012
regarding design of CVT's and belt slip during acceleration,
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Post by ng5y on May 26, 2014 7:30:36 GMT -5
I only tried on one trip home but I was not able to fully duplicate your results. May be I am just not able to find the sweet spot on my little china scoot. Taotao Evo 150 ATM
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Post by oldchopperguy on May 26, 2014 12:26:56 GMT -5
I only tried on one trip home but I was not able to fully duplicate your results. May be I am just not able to find the sweet spot on my little china scoot. Taotao Evo 150 ATM
I'm not surprised, my Chinese 150 did exhibit a similar phenomenon, but NOT nearly to the extent as with my 250. I DID experience it to a noticeable extent on a Kymco "People 200" (actually a 160) though, and that scooter is a close cousin to the Chinese 150's. Alleyoop explained the "why" but I think the quirks probably vary in their "manifestation" considerably from one scooter type, wheel-size, engine-size, etc. to another. Apparently, possibly more so with Kymco designs. At any rate, it's something worth playing with.Leo in Texas |
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Post by oldchopperguy on May 26, 2014 12:31:32 GMT -5
I only tried on one trip home but I was not able to fully duplicate your results. May be I am just not able to find the sweet spot on my little china scoot. Taotao Evo 150 ATM OOPS... Sorry, I posted twice... no message here. |
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Post by alleyoop on May 26, 2014 13:43:50 GMT -5
Sorry to be the Devil's advocate but straight from the, IACSIT International Journal of Engineering and Technology, Vol.4, No.4, August 2012 regarding design of CVT's and belt slip during acceleration, You questioned why starting off the revs climb and according to you the speed should jump in relation to the RPMS, and if NOT in your mind the belt must be slipping( HAVE I GOT THAT RIGHT)? If so your completely WRONG. And for those that tried the backing off and hitting it again and it did not work, there is NO MAGIC, backing off a little and then hitting the throttle wide open again there "MAY" be a little more kick in the behind on some motors and not others, this it happens for a reason and I already explained why it may happen and not happen. Alleyoop |
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Post by urbanmadness on May 26, 2014 14:49:29 GMT -5
Not gonna try it on my bike.... I won't do a top speed run on it, because, not only would I get the speeding ticket, get hauled off to jail and the bike towed, I won't because I'm not interested in becoming a street pizza at over 90mph. So count me out for this one. but then again, it's a fuel injected 500cc..
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Post by bnc on May 26, 2014 15:53:00 GMT -5
Maybe I am the Devil. Haha.
I own a motorcycle and a scooter. The motorcycle has a steel chain and steel gears. This phenomena does not happen because the steel chain and gears cannot slip so there is a fixed relationship between the engine rpm and the rotation speed of the rear tire.
One difference between the motorcycle and scooter is the transmission. As the referenced article states, the people who design these CVT's say the belt slips more when applying more torque. So under acceleration the belt slips more resulting in a higher rpm for the same 50 mph speed. Backing off the throttle and reapplying to maintain the 50 mph means applying less torque to maintain the same speed resulting in less slip so a lower rpm results in the same 50 mph.
This is no different than using a wrench to loosen a nut. When the nut is not loose, you have to apply a lot of torque to loosen it, but once it is loose the amount of torque required to continue turning it is much reduced. On the other hand wrenches like strap wrenches based on a belt can slip under torque.
This explanation also explains why this is less likely with smaller engines. Smaller engines have less available torque so they cannot cause as great an increase in slip. It also says that if you increase speed very gradually which applies less torque over a longer period of time the phenomena is less likely to occur.
If you have a scientific explanation or a scientific paper to explain the process I am willing to listen.
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Post by alleyoop on May 26, 2014 15:55:19 GMT -5
GOOD ONE Urbanmadne, STREET PIZZA, beside you have more than enough to spare and riding at those speeds is really just asking for trouble or a coffin.  |
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Post by alleyoop on May 26, 2014 16:04:17 GMT -5
Bnc, Keep reading articles is what I say, little of what you said is true a lot not true, but you will learn, I am tired of trying to explain  Alleyoop |
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Post by bnc on May 26, 2014 18:52:24 GMT -5
No problem. I am only the messenger applying what engineers and scientists designing CVT's have said in their published papers.
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Post by oldchopperguy on May 27, 2014 3:21:11 GMT -5
No problem. I am only the messenger applying what engineers and scientists designing CVT's have said in their published papers.
Bnc,
By the way, WELCOME to the site!
Back in the sixties, I was a very competent Harley man. Between the cantankerous clutch, and that Rube Goldberg "mousetrap" hand-clutch makeover of the foot clutch, there were actually several DIFFERING factors which could indeed cause similar symptoms from the kick-starter slipping, to clutch grabbing, to not fully-disengaging. You COULD absolutely know WHAT was going on, but NOT necessarily know WHY it was happening without a LOT of wrench-time.
Alleyoop's explanation makes perfect sense with MY individual scooter. The feel of the drive-train tells this old geezer the belt is not slipping, but the variator is quite active from one rpm to another... Especially since my scoot appears to have taller-than-stock final gears. At speeds as high as 55mph I can actually drop enough rpm to open the variator a tad. Goose it a little and it's like passing-gear in an automatic car tranny.
If a scooter CVT DOES experience some slippage, YOUR information makes perfect sense. Now there cannot be excessive slipping, or the whole thing will overheat, and, the belt won't last long, but with a 400 pound scooter, that might not be as critical as with a larger vehicle.
My Harley days are now in the past, and I'm learning these scooters. So far, I'm fairly handy with them, and really do like them. Personally, while I'm always interested in the "why" of a phenomenon, I'm more interested in mastering this novelty of the CVT and what benefits it offers in overall performance and gas-mileage.
I think Alleyoop knows what he's talking about with a CVT that is not slipping. I think you know what you're talking about when there is slipping involved. I think you're both in the same book, but on different pages... LOL!
You'll probably never agree with each other, but I agree with both of you. Simply put, it GREATLY depends on the individual scooter... Now, if both of you disagree with me, that's OK too... LOL!
If there's one thing I've learned about Asian scooters, what applies to one may or may not apply to another like it. I could write PAGES on the GY6 150 air intake phenomenon... Six years of careful experimentation showed me just HOW differently the SAME action would react totally DIFFERENTLY from one "identical" scooter to another.
No sense arguing about them, just enjoy them!
Ride safe!
Leo
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..BAD TO THE BONE..
