Hello, my name is John Kelly and this is the weber auto youtube channel. Today we
are going to look at the construction of a CVT, Continuously Variable Transmission
push belt, the belt that goes between the two pulleys, that I have back
here, on a continuously variable transmission. I get a lot of questions
for my students and and other people asking how can a belt be made out of
steel and still be flexible and hold up? So I've got a belt that is all taken
apart right here on this bench and we will put it together to make a full belt
right here today. These belts are directional, there's an arrow on the belt
you can see right here that points in the direction of rotation, and this is called
a push belt and that means that the pulley, which is this one right here, that
connects to the engine through the torque converter, is going to push this
belt rather than pull it, and push it to the other pulley, the driven pulley, to
make the vehicle move. So i'll show you what a push built means, but let's
look at the construction of this belt first.
if we look real closely here you can see that there are some, what are called ring
packs, this is a ring pack, and there's one on this side of the CVT belt,
there is one over here on this side of the CVT belt. These ring pacts are made
of individual little rings, and you can have 9 rings or you can have 12
rings the more rings there are the more torque the CVT belt in the transaxle
can handle. People ask me all the time how come
CVTs can't handle much power?
Well, they can handle more power depending on how many rings they have in
the ring pack. These rings hold a whole bunch of what are called elements. If we
look closely here you can see there is a whole bunch of these little elements
here, and right here on this table I have a single element sitting here. In this
belt right here there are 399 of these little elements sitting in here; they are
directional, they have a little bump on them that forces it to go in in one
direction. So these elements sit on the ring back like that, and then there's
another ring that sits in that upper groove and holds the elements in place.
So there is two sets of ring packs. There is 399 of these elements, and on the
edge of these elements there are a whole bunch of little ridges that help it
grab the pulley sheaves, the surface of these pulleys, they're actually called
sheaves, or variators on some CVT transmissions, they are referred to, to
vary the pulley drive-to-driven pulley ratio, So there is 12 rings in a ring pack.
So there's the first, or the outermost one, and i have it labeled as the 12th
one. Each one of these is a slightly different diameter so that it
can fit inside of the previous one, so then we just come in, put the 11th,
10th, 9, 8, 7, 6, 5, 4, 3, 2, and 1.
So now we have another complete ring pack. Here is our 2 ring packs, and as I
said the little elements sit in between those ring packs, they are held in
place, they are guided by the the ring packs. When a CVT belt fails, a lot of
times one of these rings has cracked and broken and it no longer can hold the
elements in a straight straight line. Alright now, I mentioned that this is a
push belt and all 399 of these elements are put on these ring packs, as I
mentioned, but what i want to show you is that I have four rows of these elements,
obviously I would have three rows of 100 and 1 row of 99. But you will notice that if I
hold them together and push then it is like a solid bar and that solid bar is
what connects the drive pulley to the driven pulley in a CVT, it pushes like a
big solid bar that connects at each pulley with the 700 psi of fluid
pressure and all that force or all that area, the square inches, the
square centimeters, of area in there, it
puts a lot of downward force on these elements, and so when you put all of
these together it just ends up being a push belt on the one side that pushes
and then the other side there is no force are all, it just comes back it is guided
back on these ring packs for the next turn around the pulley to push the belt,
to push the pulleys some more, so as you can see here there is the arrow, there is a
part number, the arrow of a rotational direction.
Okay, so i am just going to start with a couple of stacks of the elements, set it
on the ring pack, of course that happens, makes a big mess, these are directional
as i said, so you have to make sure they're all facing the same direction
it is quite easy because they have this bump on the end of each element that
aligns the elements. These
be very clean, you don not want any dirt dust or anything interfering with the
fit of these elements, these elements are tapered a little bit so that they can
also turn the corner or go around. The pulley has an arc; almost half of it
together. These individual elements are not purchasable you have to replace the
entire belt, but when you are disassembling the CVT you really
should put some zip ties around the whole ring back assembly and all
the elements to hold them, both ring packs in place, so the elements can not
fall out. If you take one of these apart and it just suddenly falls all over
the place you can reassemble it, like I said it needs to be very clean and you
need to pay attention to the proper orientation of every single, of the 399,
elements. But it can be done. The part number and the arrow on here, if you mix those
up, it will be difficult to determine which direction it is supposed
to turn although you can look at the edge of these elements, there is a slight
taper to the edge, they are not at a nice square edge with a 90 degree end. I do not
know what angle it is but it is
not 90 degrees.
Okay we are just about done with all the elements, getting the last couple of ones
in can be a challenge. Okay, so I have got all the elements installed but if i try to
pick this up it is just going to fall all over the place, so we need the other ring
pack to go down on the other side of all these elements to hold it in place, and
this can be sort of interesting to install. It has to go down evenly, if one
side drops more than the other
it is that tight of a tolerance, it does not want to go down, if you try to lift one
of these ring packs up and it stuck in the groove, rotate it while you are
lifting and that will help get it back out. just about there. there we go.
Okay. so i pushed I am going to keep force on both ring packs, but we have now taken
399 elements, we have got our arrow of directional rotation,
we have got 2 ring packs of 12 little thin, they are 0.0075" (0.19mm)
thick each one, so 0.090" (2.286mm) for 12 of them put all together thick for these
ring packs, so that is 24 and 399, that is 423 pieces just in this flexible the CVT
belt. So that is the construction of a CVT belt, and like I said put some zip
ties around it as you are removing it and reinstalling it in the transmission so
that it does not scatter and fall over the place.
Thank you for watching.