|
|
Post by dexameth on Jun 17, 2017 7:16:25 GMT -5
So I've been tinkering with my CVT some more... Grease this, swap that, fun stuff. I just pulled my aftermarket springs out of the spare parts bin and noticed the difference in the coil direction. The two on the left are coiled clockwise, the right two are opposite. I wonder how much this affects the operation on the tourqe driver? Ive been running the yellow spring on the left and I've been getting wicked vibrations. Today I put a stock contra in and the rpms drop way too fast but the vibes went away. I'm installing the yellow spring on the right, coiled opposite and I'll see how it feels.  |
|
|
|
Post by oldgeek on Jun 17, 2017 12:56:56 GMT -5
Glad I am not the only one that ponders that question! I really dont know the answer, and I have not NOTICED a difference if there is one...There may indeed be a difference though. The physics (is that the right word?) that allow a CVT to operate are really something. There is much more going on than meets the eye. The contra spring, the angle of the grooves in the contra pulley and the torque that the belt applies to the contra pulley all have a role in how the CVT operates, not to mention the variators role in all of this!  The CVT is one of the things for me that every time I THINK I understand more about them, I just end up with more questions. Performance gains are there, and it is the little things like you are pointing out that can have major impact in the CVT. Happy Tuning! |
|
|
|
Post by greggkinney on Jun 24, 2017 20:09:39 GMT -5
it looks like if there is a difference that having the spring end going in the direction of the wheel revolution would have an unwinding effect and having it the other way would wind it tighter? maybe if the diameter was small or the spring weak. good observation guys ive never noticed they were made different
|
|
|
|
Post by benji on Jun 25, 2017 1:50:17 GMT -5
I've noticed the paint can be too thick and make it stick to the torque driver. Oh been sanding the inside of mine to get the paint off and get smoother operation.
|
|
|
|
Post by oldgeek on Jun 30, 2017 23:08:09 GMT -5
So I sat down with a torque driver and a contra spring to try and learn more about how it works.
I observed that when the pulley spreads apart and compresses the contra spring, the movable sheave rotates in a clockwise direction in relation to the fixed sheave. Another way to say it is the sheaves rotate/twist in opposite directions from each other as the contra pulley opens up. The twisting is only about 1/2" of an inch when measured near the center of the contra pulley hub.
With that in mind, a clockwise wound contra spring's opposing ends will be twisted by the sheaves in a direction that UNCOILS it as the pulleys move apart.
Likewise a counterclockwise wound contra spring's opposing ends will be twisted by the sheaves in a direction that COILS it up further as the pulleys move apart.
Therefore IMO you would NOT want to use a CCW wound contra spring because the twisting action of the sheaves will tighten the coiled spring more causing the center diameter of the spring to become smaller, which will cause the spring to bind up on the hub of the pulleys as they move apart. At least that is what the CCW spring I have was doing.
A bearing base of some type or another on one end of the contra spring may make all of this twisting irrelevant. But you cannot always use a BBbase with the long contra springs because it could restrict the contra pulley from opening all of the way.
|
|
|
|
Post by greggkinney on Jul 2, 2017 17:51:15 GMT -5
thanks for taking time to look at one working oldgeek. i thought rhat either one way or the other would have that unwinding affect. glad dex brought this to my attention, like i said i had never noticed they are made differemnt. thanks guys
|
|
|
|
Post by gsx600racer on Jul 2, 2017 22:16:45 GMT -5
There are some contra springs I think that use spring windup and unwind in conjunction with the spring stiffness.  Notice the ends of this spring. 
2nd, I don't think the friction(at the ends of the spring) and coil direction has much effect on the overall performance of the rear pulley. When the rear pulley opens, its about 3/4 to a inch movement laterally and like oldgeek mentions about 1/2 inch in rotation. I know Hoca makes a ball bearing setup and Malossi makes a torsion control bushing/washer that's supposed to help with the springs performance. Without any "true" dyno testing with these upgrades or spring coil directions its really hard to say if there are gains or losses. I have used the Malossi torsion controllers on several of my scooters, and to be honest I really don't see the the difference. The placebo effect thinks there is a difference because i'v added to the list of the other go fast goodies. Great topic, but I am on the fence if there any pros or cons to the above mention items/scenarios. |
|
|
|
Post by spaz12 on Jul 3, 2017 3:08:59 GMT -5
Think about an abused TD and how they effect "gear" changes. They're terrible. The opposite is true of a well maintained one that is lubed properly and has little friction. Add a torsion control and you have even less friction. And also, friction creates heat, which we all know is bad.
About the malossi torsion control. It's meant to sit in the spring cup on the TD, but you'll notice that it sits high and puts more tension on the spring. If you stick it on the clutch side you don't lose as much space and, for me, has worked better.
|
|
|
|
Post by oldgeek on Jul 3, 2017 5:07:59 GMT -5
...............2nd, I don't think the friction(at the ends of the spring) and coil direction has much effect on the overall performance of the rear pulley. When the rear pulley opens, its about 3/4 to a inch movement laterally and like oldgeek mentions about 1/2 inch in rotation. ............... My point is, on the minarelli TD's, the contra spring is usually a fairly close fit to the center of the pulley. So using a contra spring that is wound in a counterclockwise direction could easily cause binding of the spring on the center hub because of the noted twisting and coiling effect. The Kymco ZX TD and the GY6 TD use a larger diameter contra spring. IIRC the spring fits a little looser on the Kymco so a bit of extra coiling may not really affect them at all. I have noticed performance CHANGES using BB bases, but the changes may have been mostly caused by the increased contra spring pressure created when using the BB base. As a matter of fact one of the best stock Mina CVT setups I ever had used a short contra spring (1200) and a BB base. Like spaz said. Anything that helps smooth out the CVT is a welcome addition. |
|
|
|
Post by greggkinney on Jul 7, 2017 8:44:40 GMT -5
Think about an abused TD and how they effect "gear" changes. They're terrible. The opposite is true of a well maintained one that is lubed properly and has little friction. Add a torsion control and you have even less friction. And also, friction creates heat, which we all know is bad. About the malossi torsion control. It's meant to sit in the spring cup on the TD, but you'll notice that it sits high and puts more tension on the spring. If you stick it on the clutch side you don't lose as much space and, for me, has worked better. the directions that came with my malossi said to install it on the clutch side. |
|
|
|
Post by 90GTVert on Jul 7, 2017 8:49:50 GMT -5
I've always installed them in the spring base/TD cover. They wouldn't fit in the clutch anyway with mine.
|
|
|
|
Post by spaz12 on Jul 7, 2017 18:38:49 GMT -5
Haha I've never read the directions, but have seen others install it on the TD.
It wouldn't fit in my clutch either and I had to modify it slightly by trimming a bit off the outside edges.
|
|
|
|
Post by gsx600racer on Jul 8, 2017 23:24:49 GMT -5
Think about an abused TD and how they effect "gear" changes. They're terrible. The opposite is true of a well maintained one that is lubed properly and has little friction. Add a torsion control and you have even less friction. And also, friction creates heat, which we all know is bad. About the malossi torsion control. It's meant to sit in the spring cup on the TD, but you'll notice that it sits high and puts more tension on the spring. If you stick it on the clutch side you don't lose as much space and, for me, has worked better. I totally agree. A sloppy or worn TD will effect the CVT's overall performance. A maintained TD using quality performance parts will perform better than stock. The true litmus test would to be to get a scooter on a dyno to measure the performance gains/losses between coil direction, ball bearing vs plastic torsion controllers, ect. Compare 0-10, 0-20, 0-30, ect to top speed times, seat of the pants dyno's are not the same as the real data. |
|
The CVT is one of the things for me that every time I THINK I understand more about them, I just end up with more questions.
