General Cycling Discussion - biking is like a rotor. (rx7)

have you heird about the rx7 engine? its a rotor, it has no pistons that go up and down.


well a bicycle is like a rotary engine, goes around and around. walking or running is like a piston engine up and down or back and forward, less efficiently. rotor (http://static.howstuffworks.com/gif/rotary-engine-intro.jpg)

Yeah,
I had one of those a million years ago. It was in a Mazda sedan. Crappy handling, pathetic brakes, and an engine with a 5 speed that just wouldn't quit. It looked like a large, ugly, bright yellow potato.
Unfortunately, you have the analogy backwards. Your legs are just like the
piston/crankarm assembly. Pistons go up and down over a rotating crank. Your legs go up and down over a rotating crank.

Just like a piston engine our legs have a power zone at middle of power stroke and a no power stroke at top and bottom center. This why Shimano tried Biopace.
The rotary, however, is a great little motor. It is funny to see a carbed one sitting all alone in the engine compartment. Looks like you could just reach in and pull it out with your hands.

I heard that the rotary is really expensive to hook up becuase it has to run extremely rich. Aftermarket intakes, exhaust, all run the risk of making the engine run too lean, and therefore causing detonation, and in the rotary, detonation is fatal.

Also the rotaries of the past burned oil like crazy.

The new rx-8 is also a rotary...with undoubltely the same troubles. I think I'll stay away...

Baloney,
Phatman, I had a rotary sedan, my stepdad had a rotary station wagon.
Neither burned oil; the bodies rusted away but the engines stayed strong. We didn't hot rod the engines. Back in the 50's and 60's poorly designed aftermarket hot rod parts destroyed a lot of engines. With experience, guys will learn to make hot rod parts, but it takes time. It's a gutsy little engine, I never felt a need for more power.

Don't forget, the rotary is an eccentric engine-it takes 2 revolutions of the shaft to get 1 rev of the rotor.

FWIW, the "Wankel" rotary engine is a powerful, compact engine best suited to high-performance cars. Mazda (and previously, NSU) tried to use it in all kinds of vehicles that it wasn't suited for: luxury coupes, station wagons, even pickup trucks. Rotaries are not fuel-efficent, and never will be.

If a rotory is burning oil, there's big problems inside.

These little motors are actually quite fastinating.

Mazda uses a patent of the American designer, Wankel.

Chevrolet has experimented with three rotor (as opposed to the usual two rotor) Wankels with extremely high horsepower output.

As for the analogy, it works for me. Power in 360 degrees.

The Wankels were great engines if you just allowed them to warm up before pushing hard. My mother (who has the soul of a race care driver) had one, which I installed a turbocharger on. It seems she couldn't beat out a buddy with a turbo Nissan Z. She drove it, equiped with Pirelli P7's until back trouble made it difficult to get in and out of.

In the hands of an unenlightened driver (like my wife), who will just 'pop & go' in a cold cold car, a Wankel dies an early death. Pity.

I want a Wankel.

see the rotor motor didn't have as much time to develop as the piston engine. the piston engine had much much more time to develop and to fix the problems. if you were to give to rotary engine as much time as the piston engine then it would have better fuel consuption etc..

as the analogy, a piston engine has to go down then stop completly and then acelerate back up, which creats stess. a rotary just has to turn and turn. in biking you are just turning and turning the crack. in running or walking you have to acelerate your foot forward to a stop and back. thats why in running you can't go too fast.

the fastest rotary engine went 25000rpm and the only limitation to that speed was fuel suply.

no rotor no motor.

Years ago, when Mazda was racing an RX-7 in IMSA races here in the US, I had the chance to observe the mechanics in the paddock overhauling one of their race motors. From what the head mechanic told me, the actual motor was nearly bone-stock, having only had some machining to the edges of the ports. A huge turbo with a computerized wastegate was the only real difference between a stock RX-7 motor and this 600 hp engine.

Oh, another advantage Wankel rotary motors have: they have only 1/4 the moving parts, and are very easy to overhaul once removed from the car. A decent mechanic can completely disassembe one in an hour, and be completely finished with an overhaul in one afternoon.

I like rotaries, so I'll let the analogy stand on that basis.

In WWII, a P47 pilot took a bunch of anti-aircraft fire and his (2100 hp rotary) engine starting sounding funny, so he turned and headed back across the Channel as fast as he could. He made it fine and on landing found two of his cylinders had 20 mm diameter holes in them. That plane was a beast.

The Jug (P47) was an amazing piece of hardware. I have read many stories; and I would bet a lot of them are true, of it's unbelievable toughness. While it had a rotary engine, it was a typical aircraft rotary design. The pistons were arranged in a circle around a crank. Quite different from the Wankel. One guy coming back damaged from a flight overflew American AA ahead of schedule. The full battery of AA opened up on him, ripping his plane stem to stern. Somehow, he got the plane down ; and as he was taxiing down the runway, the entire tail of the plane fell off. Someting I find even more remarkable was the the main gun of the FW190 was designed to rip a bomber to pieces. A single cannon shell could rip a wing off if it hit in the right place.Jugs routinely took hits from 190's and went on to finish the mission. In simulations I never warmed up to the plane; it can't turn for beans. But I was part of a massive week long argument once as to what the best plane of the war was.
The Jug guys pretty much won the argument.

So if we are making equals of engines and our legs to the pedals...
Then would gatorade and powerbars be Octane boost?

And breath right strips be Cold air intakes?

Going from platform pedals to SPD be like changing out the differential with a Ford 9"?

A computer with cadence be like a tachometer? Too bad the cyclo computers don't com with shift lights, that would make it easier to teach someone how to shift.


Cycling is my first love, with hot rods being second.

Ride on.

The P-47s actually used radial engines... not rotaries. One of the keys to the Thunderbolt's robustness was the fact that the engine was air-cooled (and huge). It could absorb hits without failure. There was no coolant system to rupture. pieces of the engine could be popping out and the thing would still run.

In WWII, a P47 pilot took a bunch of anti-aircraft fire and his (2100 hp rotary) engine starting sounding funny,

Strange, since the first Wankel rotary engine wasn't built until 1957. I believe you are confusing a radial engine with a rotary.

Originally posted by Dave Stohler
Strange, since the first Wankel rotary engine wasn't built until 1957. I believe you are confusing a radial engine with a rotary.

Yes, I think that poster meant radial. A radial engine has its cylinder assembly fixed while a rotary engine has the crankshaft fixed and the cylinder assembly rotating. The advantage of course was cooling.

The rotary aircraft engine predates the Wankel rotary. The most famous of these were the Gnome engines used during the biplane era. Ever wondered about the origins of the flying scarf? Scarves were primarily worn by early pilots to wipe off the oil (castor) from their goggles that spewing out the ends of the rotating cylinders in rotary engines. Also, it was often said that the endurance limit of an aircraft back in those days was governed by the pilot's ability to withold his/her bowel movements due to eventual ingestion of the castor oil. Hmmm... now that I mention that, I think we've found a certain commonality to biking. :D

i had a 86 rx7 and a 93 rx7 tt and they were both pieces of ****, more the 86 than the other, every little thing goes wrong with those cars.

The rotary is a port valved motor much like a two stroke and there are issues with comprimising on effeciency and power as well as not getting optimum cylinder filling and scavenging at all rpm's. There was also the need to protect the apex seals that do not like lean running (heat) or detonation. There is also the need to inject oil into the chamber to lube the apex seals. The rich running, esp. carbed cars, combined with oil injection not always at optimum gave the cars a reputation for being smokers. As most people were used to piston motors where smoking indicates worn rings or valve guide seals, the average person figured the motors wore out easy when they were just doing what they were supposed to.
The new motor in the RX8 uses an altered port setup, on the side of the chamber rather than in the area swept by the apex seals, to give room for a better shape (This has been a hotrod trick on the exhaust port for a long time.). The engine is also fuel injected so the precise amount of fuel is entered for that rpm.

BTW, in case it wasn't clear what I was trying to say earlier. The aircraft rotary engine is not the same as the Wankel rotary engine. They are based on totally different design principles.

Just to confuse things, I once read about a 2-stroke Wankel rotary. I guess it ran, but I can't find anything online about it.

All rotarys are "two stroke" in that they fill/compress/combust/exhaust in one cycle like a two stroke. It is not actually two strokes as the motor spins rather than pumping up and down.

Sorry, you are wrong. All Wankel rotaries use the same common 4-stroke principal (actually a 6-part process in thermodynamics, but I don't wish to confuse the matter..) as the vast majority of piston engines. A few piston engines use the 2-stroke principal (such as certain motorcycle, outboard, chainsaw, etc. motors), incuding the formerly very popular Detroit Diesel truck motors, which used a blower to scavenge the cylinder on each power cycle.

The motor I was referring to used sparkplugs on each side, and had port top and bottom. It relied on blower scavenging, was very small, light, powerful, and noisy. I also assume it was not economical.

Rev chuck-you seem to know only a very little about these motors, so I'd suggest you quit while you are behind. In fact, a Wankel does require 2 revolutions of the crankshaft for each power stroke, just like a piston engine.

Dave can you be any more of an anus in your reply?

If you feel he's wrong.. you can say you feel he's wrong. No need to make it an attack.

Attack, you mean like describing someone as an unpleasant body orifice? Perhaps you should heed your own advice.

Originally posted by late
Attack, you mean like describing someone as an unpleasant body orifice?

Are anuses unpleasant?

I remember going 140 mph stop light to stop light in a RX4 when I was in high school. The guy driving was a real unpleasant anus.

I'm sorry if I came off as a prig, but this happens to me all the time, especially concerning automobile engines. I've spent the better part of a decade as an automotive engineer, but anytime I go to a party there's always some guy who "knows more than me". Of course, he doesn't know anything, but I have to keep listening, biting my tongue, and looking for a way to slip away. Ugh!

Originally posted by Dave Stohler
Strange, since the first Wankel rotary engine wasn't built until 1957. I believe you are confusing a radial engine with a rotary.

My bad. To think I went all these years thinking radial and rotary were the same. I'm heading over to google right now to fix that deficit of knowledge.

Dave is right (no reason to be a jerk, thats ok tho, his name is taped to my heavy bag right now.) The wankel does have four distinct phases so it does not work like a two stroke(Something I am familar with, certified by Echo/Kioritz, Kawasaki, and Suzuki, since '85) Still looks a lot like a two stroke cycle and one revolution: apex passes intake port opening chamber, the chamber fills til the second seal closes the port, the chamber moves into the compression area of the housing, the plug fires and the chamber moves into the mirror image expansionarea of the housing, the first seal passes the edge of the exhaust port and spent gasses start to egress urged on by the trailing apex. Is that correct? I have never had my hands on a rotary while I have worked on thousands of two strokes (Including Detroits, my first job out of tech school) and many hundreds of four stoke gas and diesel motors.

For the record, all 2-strokes have one thing in common, and that is a pressurized intake. Without some form of blower (or even, as in a simple 1-cylider, crankcase pressure), a 2-stroke will not run. This is not the case with a Wankel rotary. It does not need pressurized intake to work.

Originally posted by late
Attack, you mean like describing someone as an unpleasant body orifice? Perhaps you should heed your own advice.

Perhaps I should, but sometimes to get a point across, it takes a slight jab to get the attention.

Now that Dave and Rev. Chuck have leveled it out, it's all fine.

Ironically, at least the three of us use our real names.

It may be coincidence but Dave Stohler is the name of Dennis Christophers character in "Breaking Away"

How Rotary Engines Work (http://travel.howstuffworks.com/rotary-engine.htm)

I had to join and make a comment here and set u all straight

a rotary engine does use the phasing of a four stroke engine suck/push/bang/blo but its processes are much different due to the movement of the rotor......but it isnt technically a 4 stroke because there are no strokes

a rotaries rotor tips(apex)and seals to housing and end plate lubrication works just like a 2 strokes lubrication system but around the figure of 100 to 1 ratio of oil to fuel due to the inner surface being chrome plated it doesnt require the amount of oil to keep it going usually its administered one of 3 ways ,either 2 little pipes that feeds into fuel float bowl from a small pump connected and driven from the front of the eccentric shaft(crank shaft)or it feeds directly into rotor housing or directly into inlet manifold

The people that dont like them and have had trouble with them generally dont know how to treat them as they are different and require different attitudes (like diesels need the glo plugs warmed up before starting)and rotaries need to be warmed up before driving them ..ive had my rotary powered car for 15 years nd the motor has never been touched other than the routine maintenance and is driven every day!!!
and on the economy issue the rotary engines design was actually originally a supercharger and redisgned into an internal compustion engine so its just a big pump but when u compare an engine of the equivalent power it aint all that bad but what other engine can rev like it does???
So basically u both were right in your own way but didnt realise it !!!!!!!

http://members.dodo.net.au/~quickservice/index.html

Ray ...My 2 bobs worth

Oh yea i forgot
and there is 2 power strokes per revolution on a 2 rotor engine!!!!!

The RX7 cars are fast. But engines are no good after 100K miles.

If a rotory is burning oil, there's big problems inside.

These little motors are actually quite fastinating.

Mazda uses a patent of the American designer, Wankel.

Chevrolet has experimented with three rotor (as opposed to the usual two rotor) Wankels with extremely high horsepower output.

As for the analogy, it works for me. Power in 360 degrees.

Actually, Fritz Wankel is German and the rotary engine was first built in 1957 in Germany (read on the Antique Autombile Club of America website).

These Germans have invented it all (4 cycle engine, aircraft jet engine, diesel engine), haven't they?

These Germans have invented it all (4 cycle engine, aircraft jet engine, diesel engine), haven't they?

Well, technically Sir Frank Whittle just edged out Dr. Hans von Ohain by a nose as the inventor of the jet engine. Whittle also claims first place for filing the patent and working prototype but Ohain's design was the first to actually fly in an airplane. Both worked on their relative designs independently and without knowledge of the other. I guess it's sort of like how calculus was invented independently by both Newton and Leibniz although some people have argued that Fermat was the real inventor of calculus.

The RX7 cars are fast. But engines are no good after 100K miles.

Wrong.

Tell that to my 1988 GXL RX-7 that had 130K on it when it was rear-ended by a semi, and thusly totalled.

Or my 1989 GXL autocrosser that had 189K miles on the original engine when I blew an oil seal while shifting at 8K RPM.

Or my friend's 1985 GSL-SE that has well over 200K on the original engine, and still drives great.

Or a gentleman from the Cincinnati RX-7 club that replaced the original engine in his 1993 twin-turbo RX-7 at 140K miles.

Wankel motors aren't timebombs. :)

The RX7 cars are fast. But engines are no good after 100K miles.

Don't be silly.
My 160K 86 RX-7 is rinning fine. It needs some lovin' but, then, so does my 160K Civic and IT is nine years newer...

Another post said that a rotary that uses oil is in trouble. A point of clarification on that: All the 12A and 13B engines are designed to use oil. They actually have a mechinism that injects oil into the intake charge to help cool the rotors and apex seals.

Like all cars of their age, these RX-7s have their issues but the longevity of the engine isn't one of them.

Cory

You guys should lighten up...whats wrong with american muscle? it moves my bike and my car.

Quote:Originally posted by late
Attack, you mean like describing someone as an unpleasant body orifice?


Are anuses unpleasant?

I remember going 140 mph stop light to stop light in a RX4 when I was in high school. The guy driving was a real unpleasant anus.

Speaking of backsides.

Truthfully I have seen FAR more RX-7's that need a new engine at 80-120k mi than any other car I have considered buying. I wanted one for a long time but couldn't find one that was running right. No one will work on them anymore, and all the ones I looked at burned oil or were in need of a rebuild

So if we are making equals of engines and our legs to the pedals...
Then would gatorade and powerbars be Octane boost?

And breath right strips be Cold air intakes?

Going from platform pedals to SPD be like changing out the differential with a Ford 9"?

A computer with cadence be like a tachometer? Too bad the cyclo computers don't com with shift lights, that would make it easier to teach someone how to shift.


Cycling is my first love, with hot rods being second.

Ride on.


i'd hate to know what to do to have a freer flowing exhaust

Geez, I just read some old posts on the Spinergy Rev X wheels I've been riding, and now all this stuff about my '93 TT RX7 being a timebomb...what's a guy to do? Actually, I did blow the motor at 33,000 miles, but I was putting 15 lbs. of boost into it, and well, I learned the hard way that octane boosters that claim to raise the octane numbers by 2 points actually mean .2 points, as in 93.2...not 95! So, these days, my streetported RX7 feasts on a diet of 100 octane unleaded, and it's bulletproof.