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Anonymous Poster

DMM Better than Wankel?

07/28/2007 12:33 AM

De Moura Motor "DMM" is a rotary engine, like most efficient than any other, very simple to manufacture, must have high torque, and low weight to power ratios.

Why it is not in the market yet?

Am I wrong?

Icementor

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#1

Re: DMM Better than Wankel?

07/28/2007 9:49 AM

Both Honda and Mazda, built a rotary engines in 1998, for high performance bike and car racing. Is this it?

Mazda 262 was an adaptation of original Wankel design.

Please provide some links or other readable or photographic reference.

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#2

Re: DMM Better than Wankel?

07/28/2007 11:37 PM

Like MANY ideas, R&R to reach perfection-of-design takes some time... and then, to reach production requires acquisition of financial backing, etc.,etc.,etc....

One of the greatest minds in automotive design (Carroll Shelby ~ the reknowned and much beloved philanthropist) has been working on an idea that will truly revolutionaize the I.C. engine industry for many years ... see :

http://www.ox2engine.com/boardofdirectors.html

http://www.ox2engine.com/revealed.html

and watch a stunning animation of it in operation at :

http://www.ox2engine.com/animations.html

"...the times, they are a-changing..." (!)

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Associate

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#3

Re: DMM Better than Wankel?

07/29/2007 5:50 AM

did u know that mr vincent designer of the legendary motor cycles designed a rotary engine .he was developing it with b.s.a when bsa ran out of cash.another company took up the idea with vincent but all came to no avail.i have no more detail as to the actual design but as it was built in prototype form there must be drawings somewhere.

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#4

Re: DMM Better than Wankel?

07/29/2007 8:00 AM

Can you give us all more details of why the DMM engine differs from Wankel? I have been watching this vehicle engine technology for many years but I have no knowledge of the DMM

Thank you

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#5

Re: DMM Better than Wankel?

07/30/2007 2:21 AM
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#6

Re: DMM Better than Wankel?

07/30/2007 10:35 AM

I think the main reason why it is not in the market is:

this engines present high wear in the seals buecuase as you can see in all rotary engine cofigurations, seals have to go a long way for each turn (mutilied by tree in the case of wankels). So regardless of the number of lobes or chambers working in them, distance traveled by seals compared to the distance piston seals ("rings") have to go per turn mostly in modern piston engines (which have short srtokes) is much longer.

Besides it is difficult to control emissions when you have to add oil to the fuel in order to reach good lubrication of the moving parts.

We will have to wait a while to see a real good rotary engine in the market.

Only aiming to help!.

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#7
In reply to #6

Re: DMM Better than Wankel?

07/30/2007 1:12 PM

Wankel was in the market for at least forty odd years, and ever since NSU Ro-80 (1967-1977, and later Audi's 1982) it has not only proven very efficient, but also very low subject to amortisation, due to the typical low rev in the high power band.

Should DMM be any different?

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#8
In reply to #7

Re: DMM Better than Wankel?

07/30/2007 3:11 PM

I agree! they had been on the market, but haven´t sold many pieces compared to piston engines so far. So I don´t consider rotary engines a success until they sart selling at least as piston engines do.

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#9
In reply to #7

Re: DMM Better than Wankel?

07/30/2007 10:15 PM

I bought a Mazda RX-2 when it was first introduced into the USA in 1970. (Their earlier R-100 was not sold here, although a handful were brought in after-market.) Very small 2-rotor engine in that engine compartment, with two distributors timed about 3 or 4 degrees apart and 2 spark plugs per rotor. They did this to ensure complete combustion. Exceptionally quiet and smooth running--when idling the only way to know the engine was running was to look at the tachometer. Very low internal mass in the motor, so you could red-line it in first gear in less than 1 second. Sound was like a very quiet airplane turbine. After over 100,000 miles, the seals were still OK, but the O-rings between the housings had "gone" -- apparently because of overheating once. Red line was 7,000 rpm. 70 cubic inch displacement, 120 Hp. Fuel efficiency was not very good, probably because of the gear ratios and four-barrel carburetor. It could run on a wide range of gasoline quality, from near 80 to 100 octane. I even ran it once with a kerosene / gasoline mix.

At the same time, Mazda was marketing a racing version of the same engine, with different bearings, turbocharger, and a 10,000 rpm red line. I think it was rated for over 200 Hp.

Wankel engines were also marketed in snow mobiles, lawn mowers, air compressors, portable generators, and probably other products also.

JMM

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#10
In reply to #9

Re: DMM Better than Wankel?

07/30/2007 10:50 PM

Very informative first-hand J. Thanks. I have always been interested in this concept, ever since the first I read about it, in the early sixties, as a kid.

The first owners were NSU who sold it to Audi who sold it to Mazda. Honda had their own design, not a Wankel-clone with-a-twist.

According to both Mazda and Honda who invested fortunes in further development, the secret to making the rotary concept reliable is in both alloys for bearings, and compounds for gaskets ans seals. In short - state of the art chemistry.

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#11
In reply to #10

Re: DMM Better than Wankel?

07/30/2007 11:31 PM

Yuval---I didn't know about (or remember) Audi's presence. The Wankel has 3 major moving parts (the two rotors and the output shaft), but has at least 18 seals (3 on the lip and 6 on the sides of each rotor). There were no valves or related valve train, because all intake and exhaust functions were done with ports that were exposed or covered by the motion of the rotors. A benefit of this is that the exhaust ports and even the entire engine can be operated at a higher temperature because there is no risk of "burning" the valves or their seats. This could yield a higher thermal efficiency.

The link to the DMM showed two rotating valves and a single rotating central shaft. The claim of only 3 moving parts is not clear to me, because the animated view showed two pieces attached to the central shaft, which were sliding back and forth as the shaft turned. The DMM appears to operate such that the two chanbers made by the rotating shaft and its reciprocating sides have their power strokes on one revolution and then the intake strokes on the following revolution. I think this would introduce a lot of vibration, but would be less with a second rotor with opposing power and intake strokes.

My semi-educated analysis is that the Wankel design is simpler and lighter than the DMM design. I don't know about fuel efficiencies, but am skeptical about DMM claims.

JMM

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#12
In reply to #11

Re: DMM Better than Wankel?

07/30/2007 11:45 PM

Audi bought it in the eighties, tried to fiddle with it, and handed it to Mazda for partial development. Mazda took it into deeper R&D commitment than both parties expected, then offered Audi to buy it from, in some sort of a shady deal.

Aren't the two holding mutual shares or partners of some sort?

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#16
In reply to #12

Re: DMM Better than Wankel?

08/01/2007 1:32 PM

Since I bought my RX2 in 1970, and Mazda had a previous R-100, I suspect you are referring to a subsequent product development or modification, not Mazda's initial foray into the Wankel engine. I believe Mazda is still offering the Wankel engine in some of its cars.

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#17
In reply to #16

Re: DMM Better than Wankel?

08/02/2007 11:04 PM

The RX8 is still available.

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#13
In reply to #11

Re: DMM Better than Wankel?

07/31/2007 12:29 AM

Apparently (I didn't know this, just found out), the Citroen GS French sedan, and the Norton Commander bike, had Wankel engines.

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#14

Re: DMM Better than Wankel?

08/01/2007 1:40 AM

The DMM looks to be an ingenious design. But the major problems would be (a) the number of seals required - Sliding on the lobes to engine wall (2), sliding on the lobes to central shaft (2), rotating inlet/outlet (2). and (b) the mechanism on the central shaft that keeps the seals pressed up against the outer wall.

These must be high precision and take high temperatures/pressures in an agressive environment (this means expensive) What makes you think such an engine would be more efficient, simpler to manufacture and have a lower P-W ratio. Jeff

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#18
In reply to #14

Re: DMM Better than Wankel?

08/03/2007 10:35 AM

I agree whit you!. Besides if you take a good look at the animation in the follwing link http://meditronica.com/dmm/ you will find that the DMM engine has a great disadventage compared to Wankles (which perform equally spaced explosions) because it performs two explosions in one turn follwed by none of them in the next which in my opinion means lots of undesirable vibrations.

Aiming to help!.

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#19
In reply to #18

Re: DMM Better than Wankel?

08/03/2007 10:43 AM

The Wankel has a very low rattle, and very low noise. This is very good news for engines in general. It means low amortisation and low maintenance cost, not to mention user comfort.

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#20
In reply to #14

Re: DMM Better than Wankel?

10/12/2007 3:20 PM
[quote]

These must be high precision and take high temperatures/pressures in an agressive environment (this means expensive) What makes you think such an engine would be more efficient, simpler to manufacture and have a lower P-W ratio. Jeff

[quote]

I think the higher efficiencies might be claimed because it seems, at least from the animation to be pure rotary output, it does not work on an eccentric as the Wankel does. But the sealing problem still remains unsolved, so it has to be quite fuel intensive I should think.

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#15

Re: DMM Better than Wankel?

08/01/2007 8:50 AM

There was even a Wankel engine for model aircraft I remember, and for motor bikes....

Also, I do believe that some small airships used modified motorcycle Wankel engines....

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