Rotary engine in a dirt bike

[Todd Ogle]

Does anyone know if an attempt to develop a rotary(Wankel;RX-7) engine
for a dirt bike. I have seen a rotary engine from a Mazda RX-7, and it
was small. These engines are similar in theory to a 2-stroke. Light,
high-HP to weight ratio.

Todd Ogle
CR250

[Mike King]

I have never heard of a dirt bike application, but I remember a street bike
from Suzuki in the 70's.
--
_____________
Mike King email: mi...@hpdmd48.boi.hp.com
Hewlett-Packard Disk Memory Division

[Will Pattison]

Puch used to make one. don't know if they still do. My brother is
hip on rotary engines and he has cobbed one into an old kdx175 frame.
the power is soft, very linear, and they use tons of gas. this is
not to say that they don't have potential, especially for off road.

will pattison

[RPFirley]

When you (Will Pattison) use the term"rotary engine" are you referring to
the Wankel rotary engine design made popular in Mazda RX-7 automobles or
engines that use rotary valve induction like the Rotax engines (Can-Am
two-strokes, Ski-Doo snowmobiles, and Sea-Doo watercraft)?

[Pete Plassman]

In article <DItvw...@boi.hp.com>, mikek says...

I have an old Dirt Rider (not the current mag) from the '70's that has a
picture of an Air-cooled Hercules rotary dirt bike at a two-day
qualifier.

Pete P.

[Todd Ogle]

I personally am referring to a Wankel, not a rotary valve 2-stroke, Ala
GP roadracers or Suzuki from late 70's. I am fascinated by the idea of
a rotary in a MX bike because of the power to weight ratio. There are
people who feel that rotaries are the future and reciprocating engines
are dinosaurs becouse so much energy is wasted converting linear
motion(piston and rod) into circular motion(crankshaft, tranny,
rear-wheel(s). I have heard that there may be a rotary in a street
Beemer but this is all conjecture.

[Wallace Tam]

Todd Ogle (og...@wpi.org) wrote:
: a rotary in a MX bike because of the power to weight ratio. There are

: people who feel that rotaries are the future and reciprocating engines
: are dinosaurs becouse so much energy is wasted converting linear
: motion(piston and rod) into circular motion(crankshaft, tranny,
: rear-wheel(s). I have heard that there may be a rotary in a street
: Beemer but this is all conjecture.

If rotaries are so good, why do RX7's have such bad mileage? They don't
get any better mileage than small block V8's in mustangs and camaros.

--
world wide tam
ww...@ucdavis.edu
(916) 759-2297

[Pete Plassman]

In article <4a1h78$f...@solaris.cc.vt.edu>, og...@wpi.org says...

>
>I personally am referring to a Wankel, not a rotary valve 2-stroke, Ala
>GP roadracers or Suzuki from late 70's. I am fascinated by the idea of

>a rotary in a MX bike because of the power to weight ratio. There are
>people who feel that rotaries are the future and reciprocating engines
>are dinosaurs becouse so much energy is wasted converting linear
>motion(piston and rod) into circular motion(crankshaft, tranny,
>rear-wheel(s). I have heard that there may be a rotary in a street
>Beemer but this is all conjecture.
>

There have been several street bikes with Wankel engines. The most
numerous were the Suzuki RE-5's of the mid '70s. In addition, Wank-bikes
were produced by Simpson, Van Veen, and Norton (yes, Norton). In fact,
Norton (or their namesakes) campaigned a rotary road racer in the late
'80s with some limited success in British events. I saw one race at the
Isle of Mann in 1989. At the time, the Norton rotary was seen to be
approaching solutions to the problems surrounding wankel implementation
on two wheels. I guess they just ran out of money, or the cooling,
weight, and fuel consumption problems became too much to overcome. If
you know Kevin Cameron's email address, I'm sure he can shed more light
on the subject.

Pete P.

[Eric Murray [TEMP]]

In article <4a1h78$f...@solaris.cc.vt.edu>, Todd Ogle <og...@wpi.org> wrote:
>I personally am referring to a Wankel, not a rotary valve 2-stroke, Ala
>GP roadracers or Suzuki from late 70's. I am fascinated by the idea of
>a rotary in a MX bike because of the power to weight ratio. There are
>people who feel that rotaries are the future and reciprocating engines
>are dinosaurs becouse so much energy is wasted converting linear
>motion(piston and rod) into circular motion(crankshaft, tranny,
>rear-wheel(s). I have heard that there may be a rotary in a street
>Beemer but this is all conjecture.

I've seen that bike, it's a Mazda rotary in a "BMW" sidecar rig.
The rotary is in the sidecar and drives both the sidecar wheel
and "motorcycle" wheel. It's a BMW only in appearance, the "BMW"
engine is really a fuel tank. The bike was built by a local (SF bay area)
guy.

Mazda builds the only production rotary, in the RX7, and production
will stop this year. The rotary is for most purposes dead. It's
downfall is the poor combustion chamber shape. The chamber
is wide and thin, which makes for poor combustion and much heat loss.
Rotaries throw so much heat out the exaust that it has to be made
of stainless steel. The Suzuki RE5 had to have a double-wall
exaust pipe and an air scoop to direct air in between the two pipes
to cool off the inner one.

The bad combustion chamber shape makes the rotary less fuel efficient
and dirtier. I think it will only be used in a few applications where
light weight is of paramount importance and fuel efficiency and emissions
aren't a concern. Like aircraft target drones for example. The
Air Force doesn't care about fuel costs for target drones, and they're
not subject to EPA restrictions like ordinary citizens are.

--
eric

[Dirk C. Wehrmann]

In the late 70ies Hercules built some "works"-bikes for enduro races with
a rotary (wankel) engine, built by Fichtel & Sachs. That engine was
normally used for snowmobiles.
The wankel dirt bike was not very successful.

DCW

[Jeff Dunham]

In article <4a1h78$f...@solaris.cc.vt.edu>, og...@wpi.org (Todd Ogle) writes:
|> I personally am referring to a Wankel, not a rotary valve 2-stroke, Ala
|> GP roadracers or Suzuki from late 70's. I am fascinated by the idea of
|> a rotary in a MX bike because of the power to weight ratio. There are
|> people who feel that rotaries are the future and reciprocating engines
|> are dinosaurs becouse so much energy is wasted converting linear
|> motion(piston and rod) into circular motion(crankshaft, tranny,
|> rear-wheel(s). I have heard that there may be a rotary in a street
|> Beemer but this is all conjecture.
|>

I used to snowmobile in the mid-70s and remember reading tests on
a few rotary powered sleds. They were very fast but had extremely
poor fuel efficiency. Is this inherent in the design?

jeff

--
jeff dunham 1994 KX250-K1
jdu...@wv.mentorg.com 1995 XR250R
(503)685-4835