New project! ( I’m getting excited about this on)

[ratdog]

Benji

OK, I think I figured out what you are talking about!  I think you are referring to the action of the Torque driver in the clutch The torque driver effects how easy or hard the rear drive disks are to separate There are groves cut at an angle that increase the force required to to “open up” the rear drive disks. If these are at a lower angle, its harder to open the drive disks and keeps the CVT effectively in a “lower” gear longer. (makes the variotor have to spin at a higher speed so the weights can "push harder")  On some torque drivers, these groves have two different angles. So the gear ratio will start low and move up fairly easy, until it hits the change in angle. That change in angle will slow down the opening of the the drive wheels, making it feel like a “shift”. Of course its not a shift in gear ratios, its just a change in the rate the hub can open.

I guess some torque drivers can develop a indent at the angle change making it even harder to “get over the hump” so to speak. I'm guessing this is the problem with your bike. And from what you say about it sometimes getting stuck, like when you use lighter weights, that would keep the CVT in a medium “gear” I would be like leaving a manual trans in 2nd gear. Your revs would continue to climb, but the belt would be prevented from changing positions because the weights cant transfer enough force to push the rear drive wheels apart.

of course if your torque driver has straight slots, all that dosn't apply and there is something else creating what you call a shift

I think this is where you misinterpret the power curve of the engine. it has nothing to do with the torque from the engine, its that the CVT can't advance to the higher ratios and of course if you doesn't have the gear, you are limited in how fast you can go.

This has nothing to do with the power of the engine, its just that for some reason, the rear drive disks cant be forced "open" with the force that the weights up front are generating

That's the so called "torque driver" in the CVT clutch, has nothing to do with the Torque of the engine

[benji]

Actually, I do have straight slots on my rear pulley. I have a malossi overrange. I don't "sometimes experience flat spots when shifting", I was referring to when I was tuning it. my CVT has no problem shifting, it holds RPM all the way until the rear pulley is completely open and then raises RPM to redline like it should.

The shift occurs during acceleration; you "feel it" by watching the rpm on your tach stay even until the rear pulley is open. This is shift point is set by the roller weight and rear contra spring tension. The slots and there angles have more to do with the actual shifting itself, as in how fast or slow the pulley moves open or closed, not only as it upshifts but also when it down shifts when you reach a hill.

Too light of rollers won't allow the rear pulley to shift all the way because the TORQUE SPRING won't allow it too. this is the same Principle as when you start going up a hill and this CVT down shifts.

[benji]

If you would like to hear my bike accelerate and it's shift point, there are plenty of videos I've posted. Some even show the tach as it accelerates.

[benji]

Here ya go. This should help ya.

49ccscoot.proboards.com/thread/8213/cvt-operational-theory

[benji]

[ratdog]

So you are still insisting that there is some how a “shift” in the CVT. Where is there anywhere that changes gear ratios in the CVT other then the variable size of the pulleys?

I dont understand hoe your description of how the CVT works is different from mine.  I guess I'm not explaining it so you understand what I'm saying

so now I understand what you think of as a “shift” that’s fine.

but once again, that is how the CVT works, has nothing to do with engine torque or horsepower.  Once into full lock up, your are at higher RPMs and at higher RPMs its HP not torque that makes you go faster

Do you understand why changing weights effects RPM?  I know you know cause and effect (lighter weights higher RPM) but do you understand why that is?  Just wondering.

many many years ago people saw the sun always came up in the east, and always went down in the West.  So of course that ment the sun rotated around the earth.

[benji]

Dude.... You need to stop writing these novels and do some reading haha.

Yes, I know what the weights do. I know because I've read the posts and watched the videos of the experts who came before me instead of coming up with my own homebrew theories.

Instead of assuming you know more than everyone, consider that you may be (probably are) wrong and that you could learn something on here if you listen and read and learn.

[ratdog]

Benji



I wish you where the one that was open to “learning something”



First, when you talked about a “shift” I thought you actually meant there was a shift. If you are driving a car with an automatic trans, the car takes off and the RPMs build to a programmed “shit point” Lets say 4000 rpm. Then the car shifts to a higher gear (actually lower final drive) from the seat of the car we might feel a little hesitation, the the RPMs drop to say 2500 and start increasing all over. This is what I thought you were talking about when you said “shift” the whole point of a CVT is that it doesn't do this. What does happen in these CVTs is that the rear drive plates become harder to force apart, so the RPMs have to increase to create more force to separate the rear drive plates. To the rider, this feels like a “shift” but it really isn't. In fact, the RPMs go the wrong way to be a shift. The RPMs increase instead of decrease.



But I now understand what you are talking about. That “feels like” a shift to you, so that's what you call it.



Remember this all started because you “proved” that torque makes you go faster because when you lowered the weights in your CVT the engine no longer had enough torque to pull higher speeds But when you changed to a heaver weight, suddenly the engine had enough torque to pull higher speeds. That just doesn't make any sense at all. The power curve of an engine is not effected by how you tune the CVT.



Tuning the CVT effects how fast you accelerate and how fast you can go, If the engine make 5 hp and 4 ft lbs of torque at 6000 rpm with 6 g weights it will still make 5hp and 4 ft lbs of torque with 9 g weights in the CVT



think about this. I can buy a pick up with a turbo charged diesel that has 500 ft lbs of torque and 260 HP. I can buy the same pickup with a turbo charged gas engine. That pick up has 360hp and 300 ft lbs of torque Pick up 1 has a lot more torque and will pull heavier loads better. But pickup 2 is a lot faster. Less torque, but faster.



Have you ever talked to racers? You will never hear a racer say “ I need to build more torque into my engine so I can go faster” depending on the weight of what he is putting the engine in, more torque might give him a quicker 60 ft time, but if he wants to increase his trap speed, he builds for HP.

[Moat]

Aug 22, 2018 11:21:18 GMT -5 ratdog said:

Quote; "This is what I thought you were talking about when you said “shift” the whole point of a CVT is that it doesn't do this."

But the thing is, they do do this. Many/most CVT's have a definite "shift" during acceleration, where at some point as road speed is increasing, there will be a distinct, rather sudden drop in RPM's as the rollers/sliders "shift" into their (more) outer location in the ramps (and just the opposite "shift" happens on deceleration - such as when encountering a hill). AFAIK this has to do with the angled slots in the rear TD's sliding sheave, their "sensing" the torque being transferred by the belt, their influence on/against the torque spring, and - importantly - the effect/counter-effects of the division of that torque as applied to the road at the rear wheel (meaning; the torque @ a given engine RPM decreases at the tire-to-road footprint as wheel speed increases - as per torque application cycle, it's being spread over a longer distance [as in leverage]).

I myself don't quite fully understand what all of the finer details of scooter CVT operation are, but there's definitely more there than meets the eye on what, at first glance, appears to be a very simple drivetrain design. Mathematics could describe/define it, I'm sure... but I suck at math!

Bob

[ratdog]

Moat,

Thanks for that. As I stated above, it depends on what you define as a “shift”. What makes this statement confusing is the discussion of torque. He is not discussing ENGINE torque, but the torque inside the trans. I think this is where the confusion came from. The other poster made the jump from torque to engine torque. It a little like saying the “torque converter” in an automatic thans changes the torque curve in the engine in you car.

Maybe it was missed in what I said, but I was talking about what happens after what I call full lock up. Not a term others may use, but it is how I describe the point where the rear pully is as low as it’s going to go, and the front is as big as it’s going to get ( and we can assume the clutch is locked up solid). At that point, for practical purpose, we have a direct drive from the engine to the rear wheel. That’s the point where the engine power band effects the top speed. And at that point what determines the top speed is the engines HP, not the engines torque. HP peaks at some RPM and more RPMs give you less power.  I have never seen any power band charts on these little guys, but I would guess the power peak on a stock engine is around 7500 rpm. When we modify these little engines we do two things. We increase displacement and compression so we have more power at the same 7500 rpm and we increase breathing and timing to move the power peak higher up the RPM scale.

what the other poster may be calling a “ shift” is what I call “full lockup”.  Again it’s terminology, what is a “ shift”. To most people out side the CVT scooter world, a transmission “shift” would mean a change in gear ratio.  To the other poster a “shift” is when the transmission stops changing ratios.

This is another quote for the stuff the other poster linked to


"I've even seen pictures of torque drivers that use curved grooves so the angle would be different all along the path. With the two-angle grooves you could probably say that C-D would be angle one and D-E would be angle two and E-F would become the over-rev portion after belt travel completes. It can at times be a very pronounced "shift" when the CVT moves from one angle to the next and seem very much like a geared transmission shifting.
"


So once again we have something that "seems like" a shift but there is no change of gear ratio.  personaly. i think calling these events "shits" is very misleading.  

[ratdog]

So, back to the earsplitingloudenboomer.

Many parts have come in and we have been having some fun. Among the new goodies is a 52mm piston that is much better quality the the original “kit” piston. When we were putting the kit together we measured the bore and found it had a good deal of taper. The bottom of the bore was larger then the top of the bore. There was no way to “add in” metal so we put that cylinder aside, and bored the stock cylinder and fit the piston. (the advantages of Walt owning a machine shop) We had also cleaned up the top of the piston and cut it into a nice dome. This is a very simple thing to do with a cnc machine, as I just have to pass a radius and length to a function. We had “ cleaned up” the cylinder and head to get them flat and parallel to the crank. Then I set up the head in the CNC machine center (Mill) and cut a squish area on the head to exactly match the dome of the piston. We also cut some base gasket “spacers out of some thin copper sheet so we could use them as spacers to adjust deck height.

So now we have this shiny new 52mm piston. The piston top did not need to be cleaned up, but we decided to machine a dome to exactly match the junk piston (and head). We took the cylinder with the tapered bore, and bored it and fitted the piston and did a very fine hone job on it. How we have two bored out cylinders, one with a fitted 50mm piston the other with fitted 52mm and we cut the second cylinder to give the same deck height as the first.

Of course the big item we were waiting for was the new final drive gears. We pulled the variator and clutch assembly. We opened up the gear box and removed the gears. While we were here, Walt removed all the bearings, and sent one of his gofors out to get high quality replacement bearings. (One of the few advantages of living near Detroit, there are places that have a ton of different size bearing in stock!)

We put the intermediate gear in the powdercoat oven and the new intermediate shaft in a small cooler full of ice. ½ hour later, the heated stock shaft almost dropped out of the gear when we put in in the press. Flipped it over and dropped in the new intermediate shaft. Very little pressure was required to seat the shaft.

We put it back together and installed the new High performance variator and Erlandson drive belt I have no idea if there is anything special about this belt, but I guess it was what the guy that sold him the other stuff recommended. There was nothing wrong with the original belt, so we kept it too. We put it all back together and it fired right up.

We had discussed polishing down the cam circle (but not the lobes) while we were in the shop. I wanted to take a couple thousands off, which meant when the valves were re adjusted it would give us more lift. Walt decided he would just order another cam and do that later. So good news, the project will continue!

We took turns for about the next hour “breaking in” the engine. The only change I noted was there was a very noticeable “slip” time increase, When you first take off, there is a short time when the clutch slips with the lower final drive, the “Slip” time is a good bit longer Basically when you first take off, it takes longer to get going. The other thing I thought was happening, was the it felt like it was accelerating faster from 20 to about 35. we never ran any benchmarks for that, so its really just a seat of the pants feeling.

After a plug chop and deciding the jetting was still good at “95” Walt took it out for some high speed runs. With a slight tail wind, he got 57mph and going the other way he got 55 mph. So we are going to call it “56” top speed. The 0-30 times are actually longer (worse) with the taller gear. The 0-40 time is about the same. Top speed is 3 mph faster but with a lot less RPMs this is a good thing because now if we can find some more HP up in the 8500 rpm range, we can get more speed without tearing the engine apart.

I think a stroker crank is next! Walt is talking to some sellers of strokers to see if the cranks are pressed together, or welded up. His plan is to get a stroker crank that is pressed together, pull it apart, and replace the rod big end and main bearing with some good American bearings! I'm sure we will be replacing ALL the bearing in the not to distant future. Walt HATES Chinajunk bearings!

Update. These runs have been done using my 22mm carb. He also go in a 23 mm carb. We stuck a 95 main in the 23mm carb and ran some more runs. According to the GPS, he got 57mph in both directions.

We are going to do some work on this carb to see what we can get. Right now the pilot jet is way too lean and the needle is too low. After we adjust those to get better driveabiity, Id like to try going up to a 100 main to see if she isn't just a tad lean. At any rate the 23 mm seems to be a winner

[benji]

Okay, now you're just putting words in my mouth.

I never "confused engine torque w with torque inside the trans".

I don't really have the time or the care to go into all the other stuff that you got wrong, but it was plenty haha.

Seriously, you should be reading instead of writing. Go learn some shit before you start some shit.

[ratdog]

well Thank you Benji, as usual I was looking forward to your opinion. It will be a pleasure to see you go. As it happens, I do read , a lot. The difference between me and you is I understand what I’m reading.

i teach some programming courses over at the CC.  Every new class will have some script kiddies in it.  And these people are so impressed with their selves, they think I should give them an A+ and they shouldn’t have to do all the class work.  They kinda remind me of someone that I see posting on this board from time to time

[ratdog]

More fun! Walt just stopped by and dropped off some more parts! He dropped off two more “A9” cams! They are made by different companies and are different from the cheap A9 cam that came in the kit. Our grand plan is to try screwing with one to get higher lift to see if that helps any. I’ll let you know how these cams compare.

[ratdog]

Comparing the 4“A9” cams
I do not know who made these cams. Walt didnt let me know. Two of the cams are made in China the other is made in Taiwan. Cam #1 came as part of a low priced BBK. Cam #4 is the one made in Taiwan.

I mounted each cam between centers, then setup a dial indicator to measure the “lift” of the lobe. I was only concerned with the duration of the cams. I was to lazy to mount the cams in a head and measure valve movement to get the real 

                ******** THE BATTERY WAS NEAR DEAD IN MY INDICATOR. *********
                                 I’m going to redo these when I ge back in town (Monday)
                                 Sorry, just don’t want to post inaccurate data
                 ***********************************************************

now these are all supposed to be a “A9” cam. While 1 and 2 are close enough for government work to call the same, Cam # 3 is a very different cam.

Now my original plan was to modify one of these cams by grinding off a little of the cam circle, I'm going to put that on hold until we see how cam #4 effects the bikes performance.

So, at least based on these three samples, all “A9” cams are not created equal.

If you've read the previous posts, it may not come as a surprise that Walt is picking up some new bearings for these cams too!