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About SD12

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  1. SD12 added a post in a topic Variator Performance   

    Here's a debatable opinion involving the GY6 type variator.  Roller vs sliders.
    The rollers fall into what I would call bad engineering design. Using a roller as a wedge between two ramps.
    I haven't used sliders. I think the rule of thumb is that a slider generates the cg force of a roller approx. 2 grams heavier. I think that is because the sliders work way more efficiently than rollers. More of the cg force gets transferred to the pulley sheave whereas some of the rollers cg force gets wasted in scuffing and binding.
    I believe that while a slider works as a wedge and forces the ramps apart reasonably well, a roller is also used as a wedge in trying to force the ramps apart but doesn't work very well. The roller would have to roll on one ramp and skid backwards on the opposing ramp. At some point the roller eventually just stops rolling and skids on both ramps. That is where the flat spots come from.
    The flat spotting isn't consistent either. I have had roller sets where one roller had flat spotted down to the metal and another of that batch had much less flat spotting, maybe several small flat spots. I think that is because one roller locked up sooner than the other.
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  2. SD12 added a post in a topic Variator Performance   

    I want to honor your request to keep this thread on the variator. I am pretty knowledgeable on the Torque Sensing function of the driven pulley and I can throw in my 2 cents if you intend to make a thread covering that.
    I tend to use analogies a lot on this sort of stuff and I like to do some comparisons to snowmobile CVT's and even car auto transmissions. I try not to go too deep so as not to cause confusion but I think it can help. The snowmobile world has quite a bit written up on this and can be very helpful if you learn up on the basic functions and understand the differences. Even the owner/service manuals might include a pretty nice theory of operation.
    One of the differences to snowmobile CVT's is that they tend to make a lot of use of the  mid range of throttle and performance.  With the larger pulley diameters (more range), higher hp, faster speeds and the road conditions (scooters on smooth pavement vs. sleds off road / varied terrain), I think even the no-fear squids would be surprised at how much they are actually off the throttle on a snowmobile. Not sure how much of that compares to a scooter with the performance range being much smaller on a scooter between no-throttle and full-throttle.
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  3. SD12 added a post in a topic Variator Performance   

    Good stuff.
    I'm with you on some of your misconception 1 and on some not so much.
    Lighter flyweights do make more acceleration. It has to do with a different misconception.
    Most if not all of the CVT discussion in these scooter forums is oriented around max performance, WOT, highest top speeds. But the CVT is designed for more than that.
    I'll use an example using made up numbers:
    Engine rpm at clutch engagement - 3000 rpm
    CVT "tuned" engine rpm - 7000 rpm (This is a maximum rpm that the CVT trys to limit by upshifting.)
    CVT controlled engine rpm operating range - 4000 rpm (7000-3000)
    The operating range is a big part of the CVT that tends to be ignored by these scooter forums. I'll wager there are scooters all over the world that the operators seldom use full throttle or run the engines up to "tuned" rpm. They aren't getting to top speed of course but the machines are upshifting to some extent and the folks are puttin around just fine.
    If you impose the ground speed through the drivetrain up to the drive pulley, you can look at it as engine rpm - mph. Lightening the flyweights equates to a higher engine per mph. That's the same effect as the lower gearing, better engine torque that you describe.
    So at takeoff your rpm's are closer to the 3000 than the 7000 (not much hp) and the lighter flyweights allow the engine to use that lower gearing effect to increase rpm's - mph a bit.
    The speed part I agree with. Different flyweights effect the upshift of the CVT. Once the CVT up shifts to full shiftout then the flyweight's job is essentially done and different flyweights won't matter.
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  4. SD12 added a post in a topic eZuma   

    Well yeh on a load circuit you get what is needed, larger voltages will increase power. That would be similar to the starter circuit on a "normal" vehicle using heavy wires between the battery and the starter.
    I was referring to your complaint about running 72 volts to the handlebars instead of a relay setup on what I assume would be a control circuit. Engineers do that because they want to and its not just the Chinese.
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  5. SD12 added a post in a topic eZuma   

    Engineers love voltages above 12v. Lets them use smaller wires (higher gauge) due to Ohm's law. Smaller wires are cheaper, less weight, take less space, etc.
    I had several debates with engineers at a US based world recognized company that were betting that basic automotive electrical systems would be replaced with 48v dc systems by    2015. We weren't directly in the automotive industry but they had associations. And that wasn't with electric cars or even hybreds, just basic vehicles. With tiny wires all over the things that are fragile as hell.
    They would come up with all of these hair brain ideas and poor bastards like me would have to try to implement them.
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  6. SD12 added a post in a topic Shocked this actually worked / Tire replacement   

    Good job. Your video's are nice and clear - good lighting, Wish I could manage that.
    I noticed you shamelessly cast aside your rim protectors pretty quickly in the task, been there. I think every tire I ever changed required a 15 minute fight and then it would just about fall on. Craziest thing.
    I cut some pieces of garden hose and would slide them on the tire spoon. They would cut through after a few uses but the good news is that you get a lot of pieces from a garden hose.
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  7. SD12 added a post in a topic Final Drive Gear questions?   

    The torque sensing is in play from bottom to top.. Physics would dictate that the load presented to the driven pulley would increase with speed.
    I actually find it easier to think of it as load sensing rather than torque sensing. But either way the amount that the load is leveraged against the driven pulley movable sheave is affected by the  angles of the slots. So if  the slot angles vary (curved) then the sensing impact will change throughout the CVT shifting.
    Basic CVT tuning can cover up some of the torque sensing parameters and I think that some folks may be "washing out" some of the TS benefits by over tuning the flyweight/contra spring setup.
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  8. SD12 added a post in a topic Final Drive Gear questions?   

    Something to keep in  mind is that these sorts of gearing charts and calculators work quite nicely in manual geared systems. You record the various gear ratios along the drive train along with the drive wheel OD, calculate and have a accurate answer - if the engine is spinning x rpm's then the machine is going y mph. But these GY6 machines have basically a second transmission, the CVT, which has infinite gearing. That can schew the math.
    I used to have a calculator that I made up for snowmobiles, same sort of thing, but I couldn't get any where trying to include the CVT ratio's.  I decided to consider the CVT only at the 1:1 ratio which essentially ignores it from the equation. But if the CVT can actually up shift beyond the 1:1 (I don't know if these can or not) that will add to the top speed if it can pull it.
    The other thing with the CVT is the Torque Sensing feature of the driven pulley (angled slots) . For example the Torque Sensing will see a higher geared gearbox as an additional load and try to counteract it by forcing a lower gear ratio within the CVT.
    Of course this is theory and how much of it translates to real world I don't know. I'm not sure if these smaller CVT get as much impact from the Torque Sensing as the larger CVT's.  That's why testing is so important.
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  9. SD12 added a post in a topic Belt Buster   

    If was nice to see you riding reasonably in the video. Too many show the rider acting like a dildo. Kudo's
    Speaking of dildo's, the driver in the white SUV gave you maybe a whole foot of space during your ordeal. Buck say's they were riding you before the incident as well.
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  10. SD12 added a post in a topic How does this happen?   

    The US scrapper's have been accepting crap that they never would have taken in the past. That's  because the Chinese would buy it. There's your result.
    On the axle, I have a ASW (name changed to ALM - American Land Master ) 200 UTV. The 7150, 6150 and 200 have some similar parts.
    I think they have some good tech folks there, just might not be the one that takes your call. They may be able to sub a different part number for you.
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  11. SD12 added a post in a topic Scrappy dog anyone?   

    I included a video of my GY6 150 in a four wheel cart, ASW / Menards YS200, hope it shows up.  I hooked up a tube to the crankcase breather going into a cup of water with the engine idling . 
    That is a totally stock healthy engine. No oil usage at all.
    You can get an idea of the amount of air movement / turbulence .
    I'm curious, with all the head replacements going on with these powerplants, do the new heads come with the vent baffleplate installed or do you use your old one, or have to fab something to fit?
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  12. SD12 added a post in a topic Low RPM @ takeoff, runs fine at speed   

    MJSfoto1956, you make mention of doing a uphill standing start to tune your cvt. I'm still trying to get a handle on these smaller cvt's (I'm pretty well versed on larger snowmobile cvt's. 
    Generally "normal" loads would be dealt with by the basic cvt tuning and "abnormal" loads (uphills , unusually hard acceleration , extra weight such as a passenger or cargo) would be dealt with by the Torque Sensing function.
    Even though the cvt functions have a combined effect and multi-run comparisons are very important, you may be better off doing your base tuning on flat and level with "normal" throttle.
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  13. SD12 added a post in a topic Engine Design and modification   

    Here's another "outside of the box" design.
    Arctic Cat use's this piston in their 600cc, 2 cyl, 2 stroke direct injection engine.
    The slot allows one of the fuel injectors to spray directly on the piston pin bearing.
    Compare this to the photo Pistonguy provided and notice the difference in skirt lengths.
    His racing piston is crazy short and this is plenty long in order for the slot to be safely enclosed..
    Now this piston isn't in a factory race engine, but AC claims it has 600 class leading 120+ hp.
    I've always wondered how much skirt to cylinder rubbing goes on and how these different respective lengths would affect that.

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  14. SD12 added a post in a topic How does this happen?   

    That's the first thing I thought of also. Does someone like to reach for the impact driver whenever they are spinning hardware off and on?
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  15. SD12 added a post in a topic Typical 150cc GY6 Switched 12v DC Circuits   

    Oop's, miscommunication alert.
    My point there was with the unregulated vs. regulated. I think there are far more scooters with AC  headlights than with DC headlights although DC systems seem to be getting more common.
    You can't rely on headlights being on or off as a method of determining AC or DC.
    As far as the diagram you presented, I thought you were using that to modify your machine. That diagram has DC headlights. I don't think it is as similar to your machine as you may think. Or maybe not?
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