Article On New Diesel Technology

[justlearnin]

I wonder if there are any of those wankle gas jobs still on the road?

[nimblemotors]

Originally Posted by justlearnin

I wonder if there are any of those wankle gas jobs still on the road?

fewer and fewer every day. I have an 81, this is now a "classic".
In today's standards of all-aluminum blocks and heads, the rx7 engine isn't all that light. While physically small, it has iron rotors and iron sides.

The 2 strokes are both light and compact. What concerns me about them is they make a lot of noise, both the exhaust and the roller bearings in the crank.

JackB

[K_V_B]

Originally Posted by GaryMayo

The navy is sitting on an engine from the 70's that uses no fuel. Documentary on you tube convinced me.

Such documentaries are very poor means of educating yourself. You're at the mercy of the maker, who can choose to show or withhold information at will. You can prove anything you want on the screen, something William Karel very effectively demonstrated in his documentary "Dark Side Of The Moon"

[Dockhead]

Originally Posted by Cotemar

At 13.5 hp I think this OPOC (Opposed Piston Opposed Cylinder) diesel has all those other ones beat.
1) No vibration
2) Small
3) Light weight
4) Fewer parts
When have you seen a 5kw generator thats the size of a brief case and light enough to carry.

Well, they don't claim no vibration. There will be some, of course. But two strokes are inherently smooth.

Can't wait to see if that will make it to market or not. It is incredibly compact. I don't know how you even make the alternator part of a 5kW that size.

[mcarling]

The key to making a very small alternator at 5KW is to spin it very fast. That's one reason why I think microturbines are more promising for small light gensets than OPOC engines.

This 4.5" microturbine can produce 100 lbs of thrust, which means it can generate at least 100KW on a shaft. Getting 70KW of electricity out of this should be easy. Spinning above 50,000 rpm, the alternator would be small and light:

5 Stage Axial-Flow Micro Turbine - The Worlds Most Advanced Micro Jet. - YouTube

[K_V_B]

Of course if you really want it quiet, how about a fuel cell...

[Pete7]

Originally Posted by nimblemotors

My plan is to put the kawasaki jetski direct injected 2 strokes in my cat. The 2-cylinder motors are so simple and light, you can lift them out by yourself.JackB

Thread drift but that sounds interesting, are you intending to use the jet drive too or via propellors? If your using the jet drives then is there the opportunity to pipe the jet up to the bow as a bow thruster? some interesting possibilities. Only downside is petrol vapour, but the jet sky manufactuferes must have solved the problem, unlike my little Suzuki trials bike which leaks fuel overnight without the fuel tap being turned off.

Pete

[Irish rambler]

I worked in miltary engine R&D and was involved with Rolls Royce Diesels (taken over by Perkins,Perkins later by Caterpillar) who researched in the late 50's & by the 60's were mass producing multi-fuel,two stroke opposed piston diesel engines for use, among others, in the APC 432( Brit equivalent of the M113). We ran them on anything from whisky to maize oil in demo's.
The electric motor/dynamo principle was used I believe in Wartburg engines in the 60's.
Queens University in Belfast also make a gas turbine that fits in a suitcase as well as the engineering design/development for the Rotax engine. The problm with the rotary engine is really the that rotor tips burnt out fairly quickly but this has now been solved with the development of advanced ceramics.
There were many quite brilliant engineers in the past who didn't gain world acclaim for their inventions, many 'New' inventions are in fact plagiarism, they didn't have the luxury of computer programmes or simulators and were engineers in the true sense of the word.

[dennisail]

I had a schematic of a Napier Deltec engine. I am also familiar with turbocharging as I have built a turboed 10 second street drag car. The thing which had me stumped was although the charger on the Deltec appeared to be a turbo with a compressor and a turbine, the assembly was not designed to spin interdependently of the engine like a normal turbo. It was connected by a shaft the engine. That would make it a supercharger, but then again superchargers dont have a turbine! Weird. Its like the turbine was used to recover lost energy which added shaft horsepower to the engine itself rather than for the sole purpose of spinning the compressor like a regular turbo.

As for this new amazing engine. It appears to be nothing more than a diesel rotary which even in diesel form is not new. Petrol rotarys are not know for reliability. But with the slower RPM and cooler exhaust temps the apex seals may last longer in a diesel.

[mcarling]

Originally Posted by nimblemotors

My plan is to put the kawasaki jetski direct injected 2 strokes in my cat. The 2-cylinder motors are so simple and light, you can lift them out by yourself.

Waterjet/pumpjet propulsion is efficient at high speeds (30 to 70 knots), but a propeller is more efficient at the speeds at which sailboats motor.

[Cotemar]

Originally Posted by Dockhead

Well, they don't claim no vibration. There will be some, of course. But two strokes are inherently smooth.

Can't wait to see if that will make it to market or not. It is incredibly compact. I don't know how you even make the alternator part of a 5kW that size.

When they test them they actually put a wine glass full of water on the motor to check the vibration. The wine glass stays put because the opposing forces cancel out

[Dockhead]

Originally Posted by Cotemar

When they test them they actually put a wine glass full of water on the motor to check the vibration. The wine glass stays put because the opposing forces cancel out

That was the old Rolls-Royce marketing trick.

Well, it is not quite true that the "opposing forces" cancel out, at least that's not the whole truth -- in any reciprocating engine, there are more forces than just the pistons moving in and out. There are primary, secondary, tertiary and so forth balances. The con rods move back and forth as well as up and down, creating certain forces. Also, the cylinders are slightly offset, so even the forces resulting from the pistons moving in and out are not entirely eliminated. You've also got the impulses from combustion. I don't think it's possible to cancel out all of the "opposing forces" on a reciprocating engine, unlike the case with a turbine. An inline 4 cylinder, 4 stroke engine is also in primary balance -- the piston forces are balanced -- but this is a notoriously shaky configuration due to the heavy secondary imbalance. There are a number of 4-cylinder car engines (like the Porsche 944 engine) which have balance shafts, trading horsepower for better secondary balance.

A very smooth engine is a horizontally opposed 6, like a Porsche 911 engine. You can certainly balance a wine glass on one of those, as you could on the radiator cap of the old Rolls 6-cylinders. 6's and 12's are especially good in this respect because the crank phase can be 120 degrees (or some variant in case of a v engine) so you get combustion impulses smoothed out. Horizontally opposed (VW 4-cylinder, Porsche 911 6, Ferrari Boxer or Porsche 917 12) is also good because you get much better balance of the piston forces. But no reciprocating engine can be perfectly balanced and vibration-free.

[dennisail]

The engine in my street drag car was a normal inline 6 with around 600hp. I could balance a coin on the rocker cover and rev it until it would finally fall off when the engine hit the rev limiter at 7000rpm. The engine was a standard 20 year old engine from a Toyota. (with large turbo etc) So this wine glass trick does not impress me.

[DeepFrz]

Yes, but these engines do not have offset cylinders, they are horizontally opposed and they have counter rotating crankshafts, so they are inherently smooth. Not to say there wont be any vibration but they are very easy to balance.

[dennisail]

This is my friends car with the same 20 year old engine.

2JZ Turbo E30 BMW engine smoothness test - YouTube