interesting engine...

[DummyLoad]

5 cyl.,axial sine, reciprocator, port valve engine - reads to have promise... the down side, piston speed is about 20% faster than conventional 4 stroke. see the vid on the "coin test" relating smoothness.

https://rideapart.com/articles/duke-engines-interview?utm_source=zergnet.com&utm_medium=referral&utm_campaign=zergnet_349080


--pete

[Ritchie200]

Yeah, there are all sorts of old designs like that wobble plate that folks seem to resurrect every few years. 

Here is a cool aviation engine that I thought held a lot of promise, but was never produced.

Jim

https://www.youtube.com/watch?v=uJSLDq7MkhQ

[PRR]

> axial sine, reciprocator, port valve

A lot of freon compressors have been built this way. If your Chevy has a long round A/C compressor, it is probably the swash-plate job.

> piston speed is about 20% faster

For a hypothetical RPM which they have not hit in testing.

MPS is a traditional measure of piston engine abuse, but is also relative to implementation. My bro's 1941 Plymouth ran higher MPS than my 1967 Mustang because the teeny pistons didn't cause much strain, and the poor breathing at high MPS was acceptable for the driving of the day.

To my eye, the fatal flaw is the seal between the rotating cylinders and the fixed ports-head. Bore-head seals have always been critical; many high-pressure engines avoided them (head built as part of cylinder, or bores shrunk into the head).

Swashplate shaft loads can be quite high. A steep angle means a long length between bearings, which leads to secondary resonances and mystery break-up.

The rotary cylinders *may* have a vibration advantage. Un-fold from axial to radial, you have the WWI-era Rhone rotary (not simple radial) airplane engine, where the crank was stationary and the cylinders went around. An often missed point, which explains why these were so popular, is that the pistons do not reciprocate, they follow a circle offset from the crank axis. Shake is MUCH lower than a comparable size of any other mechanism. Airplane design is often dominated by shake, since you need a high-power engine in a very light frame. I am not convinced the axial form is as good. I note there is a coin-stand video; several conventional engines will do that, many fail because there are more important design problems than coin-standing.

Doug Self has pages and pages of "clever" engine designs which have vanished, sometimes with the reasons they were failures or just not-good-enough.

And..... why do you want a teeny engine in a motorcycle? Isn't a hulking V-Twin or wiiiiide I-4 or HO-2 part of the charm? As long as it has pull to match its bulk, nothing wrong with antiquated agricultural designs.

[DummyLoad]

And..... why do you want a teeny engine in a motorcycle? Isn't a hulking V-Twin or wiiiiide I-4 or HO-2 part of the charm? As long as it has pull to match its bulk, nothing wrong with antiquated agricultural designs.

to go faster dodo!~ ;-)

--pete

[kagliostro]

This remembered me the Hercules with Wankel engine

I've seen a real one some years ago

do you remember it ?






Franco

Franco

[DummyLoad]

never even knew it existed, cool looking bike for it's day. thanks for sharing, k.


--pete

[Ritchie200]

That would be killer looking in a retro bike today!!!  That would be one REALLY smooth bike too!  So Sachs licensed the Wankel design?  I do not remember that?  Seals have always been notorious for failing, especially the older ones.  Maybe that's why it didn't make it to mass production.


Jim

[kagliostro]

On the web you can find photos of the same motorcicle under DKW brand, but I don't know more



Franco

[Ritchie200]

Is that a puddle of oil under that engine?  That could be a "check the gas and fill the oil" project!


Jim

[kagliostro]

Is that a puddle of oil under that engine?

I didn't recognize before, but ... yes, so seems


Franco

[PRR]

> Hercules with Wankel

Norton derived several bikes from that. One saw significant use as a police bike.

http://en.wikipedia.org/wiki/Norton_Classic
http://en.wikipedia.org/wiki/Norton_Commander_%28motorcycle%29
http://en.wikipedia.org/wiki/Norton_Interpol_2

A friend of a friend found a Suzuki Wankel in his girlfriend's dad's garage.

"The styling of the bike is very '70s or early '80s, which is when the Wankel was hot, but it has some odd features even for that time period.  Look at the tail light and the housing for the instruments.  The green lid flips open when you turn the key, exposing the speedometer and tachometer.
"It is a large machine, and the engine really doesn’t seem compact, even compared to an inline-four.  I don’t think the engine is much smaller than the Wankel used in Mazda cars.  It looks very compact under a car hood but it makes the bike very wide and the radiator is not trivial."

[DummyLoad]

for the time period that was very decent power to displacement ratio: 600cc w/ 85HP.


--pete

[PRR]

> decent power to displacement

The displacement of a Wankel is debatable.It has three chambers, a spark every revolution, a 1:3 rotor:shaft ratio.....

There are various methods of calculating the engine displacement of a Wankel. The Japanese regulations for calculating displacements for engine ratings use the volume displacement of one rotor face only, and the auto industry commonly accepts this method as the standard for calculating the displacement of a rotary. When compared by specific output, however, the convention results in large imbalances in favor of the Wankel motor, an early approach was rating displacement of each rotor as two times the chamber.
http://en.wikipedia.org/wiki/Wankel_engine

It also has different problems at high RPM, and to some degree usually "turns faster". With clever design, breathing can support a lot of airflow. It will burst by beating its gears or burning its seals, not by throwing a piston.

[PRR]

Chapter Eleven in the Herschel Smith book Aircraft Piston Engines touches on this topic.

Aircraft versus motorcycle---

Both want high power-to-weight.

So first-guess, motocycle and aircraft engines are similar. Indeed many of the best of early aircraft engines were derived from motorcycle mills, notably Curtis.

P/W can be high if you accept blow-ups. When a cycle blows up you usually roll to the side of the road then walk home. Aircraft users do not have this option, and are traditionally more adverse to blow-ups. Here Curtis' short-track background showed: his flyers flew real fast but not for long.

While trucks and sedans prefer a wide range of workable RPMs to reduce gear-shifting, airplanes and high-power motorcycles can be tuned to a narrow RPM band.

Between blow-ups and broad RPM, if you have an engine design which falls short, motorcycles are a logical way to get a foot in the market.

Smith makes the point that Government funds can be found for aircraft engines; I'm not aware of much tax-loot going to motorcycles.

I would think an analysis of aircraft engine types would be applicable to motocycles with a few reservations.

I like Smith's "third problem".

[Ritchie200]

Point well taken - especially when the Ultralight craze of the late 70's - 80's hit.  PW was gold.  Early designs featured McCullough chainsaw engines, Sachs motorcycle engines, and Rotax snowmobile engines.  Then Rotax grabbed the bit and designed purpose built aircraft engines that they are still supplying today - even a four cylinder 4cycle turbo that is used in several general aviation designs.  Giving Continental and Lycoming a run for the small aircraft market. 

Speaking of narrow RPM range, there is a company that takes a small APU turbine that runs at a constant speed and connects a variable pitch prop for a BD5 power plant.  A very slick design as the APU is very small yet produces lots of PW.  95 SHP at 6,000RPM.  27" long, 16.5" high, and 13" wide.  All this in a little 75lb package with a bow on it!  I would LOVE to build this one....

Jim

https://www.youtube.com/watch?v=3qB6UOwGNDA

[Ritchie200]

True, that seems to be the nemesis of the RX7 rotary conversions, the gear drives are also rob HP.  Although many are also being used along with a few small block chevys. 


The turbine conversion I was talking about uses a cog belt reduction drive to the prop shaft, so not much loss there.  Prop RPM around 4K.  The custom prop is small so tip speed is well below sos.  208 knots or 240 mph, not bad...not bad at all!!  The problem I see is if you have a belt failure, the BD5 is nothing like a glider.  Kind of like the description of the space shuttle in the movie Space Cowboys, a flying brick....   Even though full flap stall speed is 63mph, your glide ratio is crap - you are just falling gracefully.  There is also not much material between your butt and the ground and those little wheels will only roll on pavement.  The wings are wet so a cartwheel in a field might have toasty consequences.   Hey, cant be any more dangerous than riding your Harley in traffic!


Jim