Hello everyone and welcome! In this video we're gonna be talking about how rotary
engines work and in front of me I have a 13B Wankel engine out of a 1985 Mazda RX-7.
So to start things off we're just gonna be talking about all of the
different components in here then we'll be talking about how the combustion
cycle works and then from there we'll talk about some of the different unique
features on this engine and then get into the advantages of this design.
So just starting on the right here and then working our way across this is the
front plate, here we have the rotor housing for the first rotor, we've got
the centerplate, the second rotor housing and then the rear plate. Now the 13B is
a two rotor design so here we have the two rotors, these are the rotary
equivalent of pistons. And finally we have what is called the eccentric shaft
and this is essentially the crankshaft, but for a rotary engine and so this is
where your two rotors are gonna be connecting up to
and ultimately trying to rotate. So getting into how combustion works we're
gonna be looking inside of this rotor housing and what we have here are the
intake ports so as the rotor rotates over this it's gonna be drawing of
vacuum and pulling air out from these ports and it's important to realize that there's
ports on both sides so both the back plate and the centerplate have ports,
so air will be drawn in from both sides into the combustion chamber.
Moving right along here you have the two holes for your spark plugs and there's gonna be two
spark plugs used which will get into it a bit but basically it's because the
rotors gonna be rotating and the combustion chambers really long so
you're trying to speed up the process of combusting that air-fuel mixture and
then finally as that rotor rotates it will press the gas fell through the
exhaust port which you can see here. So now let's work our way through the four
cycles which need to occur for combustion so first we're going to be
starting with an empty pocket so as you can see the rotor's completely up against
the rotor housing and there's nowhere in there as it begins to rotate however it
starts to open up a pocket and this creates a vacuum and as it continues to
rotate that vacuum opens up to the intake ports allowing you to draw in air
and fuel that continues to rotate and then eventually you start to fill up
this entire chamber and then you close off the intake ports and now you've
begun compression so now the
this chamber is going to start squeezing down that air until mixture into a
smaller chamber until it reaches the equivalent of top dead center which is
about right there and so you so you can see you've got this really small pocket
and so now you're two spark plugs are going to fire and it's going to continue to
rotate and combustion is going to force this rotor to rotate in this direction
as you can see expanding that pocket and then finally you will open up to the
exhaust port where that exhaust can then dump out and the rotor continues to
rotate forcing out all of that exhaust and then the cycle repeats itself.
So looking on the side of the engine you can see the intake ports so in the
center for the centerplate it's going to divide between them so this will go to
the rear housing and then this one will go to the front housing and then
you've got these two intake ports on either side which will also feed into these
rotor housings now as you continue down you've got the exhaust port so one for
each housing now it's important to realize that at any moment within this
rotor housing you have multiple stages of combustion occurring so you've got
the initial cycle right here we've got intake you've got compression happening
right here and then you've got your exhaust stroke occurring right here and
all of these are occurring simultaneously when the rotor's in this
position. Now if you were to continue to rotate it here you're gonna be having
your spark they're going to have the exhaust and here you're going to be
having your intake stroke as you continue to rotate that rotor here you
can see combustion occuring we have our exhaust occurring and then we're
starting to exit the intake stroke and start to get into the compression stroke
and when the rotors in this position here we have our compression occurring
here we have our combustion and the exhaust is finishing up and then the
intake is just beginning
know it's also important to realize that while all this is occurring in one rotor
in the other rotor the rotor is exactly a hundred and eighty degrees offset from
this rotor and so the opposite going to be occurring in here so you're about to
start your combustion with the sparks firing you're ending your exhaust stroke
over here and you're starting with your intake stroke over here.
So here we have the eccentric shaft and as you can see
these rotors are gonna be placed at a hundred and eighty degrees apart and
that's done so that it balances on that axis so as this rotates its going to be
well-balanced rather than if it was offset it wouldn't be balanced.
Now you will still have a moment occurring because you've got one rotor going this
direction in other going this direction simultaneously but because all of this
is rotational and because it's balanced vertically along the axis it's gonna be
a very smooth very low vibration running engine so let's see if we can make sense
of how this will work out so here we have a rotor which will be on one end
and then are eccentric shaft which will go inside of that and then our other
rotors going to go on to the other lobe and of course it's going to be a set of
agrees it's gonna look something like that and see you can see that the inside
of this rotor has this gear and so this gear is actually gonna mesh up with this
stationary gear and so as that rotor rotates it's going to force the
eccentric shaft to rotate because this is stationary so that gear's gonna mesh
with this gear and then force that lobe to turn as you can see demonstrated
somewhat there now this stationary gear's gonna go on the outside of the
front plate and so there it's going to be bolt up so it's not gonna move and
then on the other side you can see that gear will come through and mash up with
that internal gear up the rotor ok so now that we understand how combustion
works in a rotary engine lets take a look at some of the unique features to
this engine design so you'll notice right here on the intake side of the
rotor housing this little hole in this isn't actually for fuel in fact it's for
motor oil and the reason this is done is to inject oil in here in order to help
lubricate the seals unlike a piston cylinder engine you can't spray oil up
on the bottom of the pistons to help create a seal there and help lubricate
things so it's actually done directly within the housing and you actually have
injectors that also inject in oil with the air-fuel mixture as well so looking
at this on the other side that's what I'm showing right here so this is where
oil injector and this is the pump which would be hooking up these oil injectors
to these certain locations where they be injecting oil and this is essentially
throttle control so as you press on the gas it opens up and injects more oil so
by design you're going to be burning oil so one of the other unique challenges to
the Wankel engine is how to seal it and so you have to keep in mind you want to
keep the combustion chamber from crossing over from one side to another
from here to here but you also don't want any crossing over this direction
outside of its you have to seal it this way and you have to seal it at all these
three edges and so the way they do that is the use these apex seals and so these
apex seals it's actually a two-piece design for this 13B engine and
so it'll be something like that and these will slide in here and they will
press up against the housing and so the way that it continues to be pressed up
against that housing is using this spring so this is essentially like a
leaf spring and it goes on like that there's a little not true to hold it in
and then you can slide that down in there and that spring will press this
apex seal out against the housing so you maintain a seal as this rotates around
and so here's a little bit of a better view you can see you've got the apex
seal it's got a little notch there at the bottom and so that spring will line
up with that notch and then you've got the top piece of the apex seal and
that'll be right there on the top and it also has a notch to hold the top of the
spring in and so you'll have your apex seal there you can slide that spring
down and with it and that will help keep it pressed out then you've got the top
portion of the apex seal and then you have this little piece right here which
will hold that all together now as I mentioned you also have to seal off so
that nothing comes over this side so you have these side seals which can get
inserted into these little grooves here and so the way that those are maintained
up against the housing is that you have this spring you can see it's rounded if
you look at it from one side but it's actually a spring if you look at it from
the side so that we get placed down into that groove and then your place the side seal over that
and that will maintain pressure up against the housing and then finally you
have your face seals which will be resting in here somewhat similar in idea
to piston rings and of course you have to maintain pressure against the housing
as well so you've got this spring right here you can see a perfect circle but if
you look at it from the side it's got these bins in it so that it creates
pressure that will slide in there and then you put your ring on top of it and
it maintains pressure against the housing.
Now one of the things you may have noticed are these drill holes and so
after the rotor has been manufactured, you want to make sure it's balanced
and so you'll put it on a machine, you can spin it and see how it balanced it is - and then you can drill holes accordingly in order to make sure it's balanced
you can see that on both sides being done in order to balance out the rotor. Another interesting thing you'll notice
on the rotors are these con que pockets and so with these do by removing material from
the rotor you increase the displacement of the engine now I'm going into the
various advantages of using a rotary engine versus using a piston cylinder
engine and so were the first things you probably notice is that there's very few
moving parts 1-2-3 that's it - three moving parts it's an extremely simple design
which has its own benefits of being simple because it's very simple it can
also be made very reliable. Another advantage is the fact that there's no
reciprocating mass all of this is always rotating so one of the disadvantages
with piston cylinder engines is that when you have a reciprocating mass such
as the valves which are going up and down you can have valve float and because of
the valve float you can't rev to higher rpms so an engine like this can rev extremely high
because it's not limited by reciprocating mess the other thing to
know with rotational mass versus having reciprocating mass is that it's going to
be very low vibrations with a very smooth running engine one more advantage
is that has extremely smooth power delivery and that has to do with the
fact that there's one powerstroke for every revolution of this eccentric shaft
for each rotor and so let's kind of look at a demo how this works
now one thing you wanna notice is that when this rotor the way it's geared to
the eccentric shaft is that for every full rotation of this rotor it's going
to rotate the eccentric shaft three times and that's just simply based on
the gearing now the other thing we wanna understand is that for
every time this roto rotates one full time around
you're going to have combustion occur three times so let's take a look at it
here you can see we've got these two parts drilled out in here it's a flat
surface certainly paying attention to this spot and rotating around one
full-time and see how many times combustion occurs so right here we have
our two spark plugs so this is going to be our first combustion which is going
to be occurring in here as that rotates and so there you have that and then you
press that out there as you can see is our second combustion and so that's
continuing on and then we're going to get into our third combustion so here we
are igniting our third combustion here's that F
that we were paying attention to so we're marking when this gets back to here
and so as you can see it finishes up back on that spot and you've had
combustion occur three times now this is different from a piston cylinder
design with four strokes because with a four-stroke engine for every two
rotations of the crankshaft you're only gonna have one combustion cycle so for
this for every rotation of the eccentric shaft you're gonna have combustion occur
as a result of this power delivery is going to be much smoother and finally
another huge advantage of the Wankel engine is just how compact it is so as
you can see it's about a foot long it's about a foot wide and it's about a foot
tall so all of this occurring within about one cubic foot a very compact
engine and you can fit a lot of power in a very small life form and that gives
you a lot of options for packaging so it's great
from that sense as far as how small it is and also want to say thank you to
Shawn for letting me borrow his rotary engine thank you guys for watching if
you have any questions or comments feel free to leave them below