A new Oz engine on the way?

[ozbear]

One explosion that's twice as big ...Actually it is technically more efficient as there is one less combustion chamber surface to be absorbing heat but minus the less efficient inlet and exhaust flow so ends up at a balance somewhere.

 

The secret parts. They are actually called "non-obvious" claims - obviously working!

 

2 of 4 are done and in Pending status, I will let you know when all are as they are related if you don't mind. They are in the Chinese system so they are effectively still a secret.

 

It's actually pretty boring method stuff though, no "super X3000 rocketboosted world saving" exciting stuff.

One small problem with the design is only 3 power pulses for the six cylinder version and 4 for the 8 cyl per 2 revolutions of the engine making it a bit on the rough side at lower rpms

Im guessing your using Suzuki or Daihatsu cylinder heads the porting will be the limiting factor if you are because if your using off the shelf heads they will need double the flow because you are in effect feeding 2 cylinders with one inlet port.

 

 

[damkia]

One small problem with the design is only 3 power pulses for the six cylinder version and 4 for the 8 cyl per 2 revolutions of the engine making it a bit on the rough side at lower rpmsIm guessing your using Suzuki or Daihatsu cylinder heads the porting will be the limiting factor if you are because if your using off the shelf heads they will need double the flow because you are in effect feeding 2 cylinders with one inlet port.

Remember that the "drive" is from the camshaft, at a 2:1 ratio, every pair of pistons makes it up and down the cyl twice per CAMSHAFT (output) revolution. This makes it exactly the same as a standard 6 or 8 cylinder four stroke. Having opposed pistons in close proximity in the same cyl should make it smoother. Compare that with slightly offset pistons in their own cyls all pushing their own little bit of a crankshaft.

 

Porting will only be an issue depending on total displacement of the individual cylinder. From what has already been written, (IIRC) then it is a 3 "cyl" 2.4l engine = 800cc/"cyl". If the heads can flow the required volumes at 6000 rpm of the pistons (ie 4800 l/min at 300 rpm OUTPUT speed) there should not be an issue.

 

 

[facthunter]

Ozbear is right about the power pulses. With paired pistons it is effectively a 3 cylinder engine as regards the number of power pulses. One firing sequence every 240 degrees ( with a four stroke engine) Nev

 

 

[damkia]

Ozbear is right about the power pulses. With paired pistons it is effectively a 3 cylinder engine as regards the number of power pulses. One firing sequence every 240 degrees ( with a four stroke engine) Nev

That would be at the pistons crankshaft, NOT the output off the camshaft... I understand what you mean, but you haven't taken your thinking through to the power output end. I agree 1 pulse per 240 degrees of the piston crankshaft, divided by two due to the camshaft "output" gearing equals 1 pulse per 120 deg of output off that camshaft, and that is the same as a normal 6 cyl engine.

Think of it as a three cyl (as you have correctly) with integral 2:1 gearbox to the only output available.

 

 

[facthunter]

A car engine has smoothness roughly related to the number of cylinders power pulses,and the RPM it is doing more power pulses. When this engine is idling it will be the engine RPM that counts . What the prop does is about as relevant as what the rear wheels are doing on a car. Off idle it won't be noticed probably. It will sound as though it is not revving much..generally. Nev

 

 

[geoffreywh]

It all sounds very interesting. I know how smooth a 120 degree triple can be (at speed) and the delicious sound they make. I'll tell you what though, the crankshaft to camshaft gears are going to have to be very very good...The load as far as camshaft drive is nothing compared to transmitting 100hp to a prop. There's going to have to be a very sturdy casting carrying some really good bearings (plain I guess) to make it work safely.... that's going to be a very difficult part of the design....Although that big gear will give you somewhere nice to mount the starter!...Hmmm, maybe not, just put a ring gear out in the open at the other end??

 

 

[turboplanner]

These are some of the characteristics of the Commer TS3

 

 

[damkia]

A car engine has smoothness roughly related to the number of cylinders power pulses,and the RPM it is doing more power pulses. When this engine is idling it will be the engine RPM that counts . What the prop does is about as relevant as what the rear wheels are doing on a car. Off idle it won't be noticed probably. It will sound as though it is not revving much..generally. Nev

Measured from where?

As I stated earlier it should be smoother anyway due to the opposed pistons in a single cyl due to the almost perfect balance of internal forces (some very minor cyclical harmonic mass issues from the conrods aside). The comparison to a standard triple is probably not valid in relation to smoothness.

 

 

[damkia]

The load as far as camshaft drive is nothing compared to transmitting 100hp to a prop. There's going to have to be a very sturdy casting carrying some really good bearings (plain I guess) to make it work safely.... that's going to be a very difficult part of the design....

This I think will be one of the biggest challenges, isolating the prop torsional vibrations (differing air densities through the arc of the prop swing due to AoA of the aircraft) of from affecting the cam timing.

 

 

[turboplanner]

As I stated earlier it should be smoother

The Commer TS3 was not smoother, nor was it quieter.

 

 

[damkia]

The Commer TS3 was not smoother, nor was it quieter.

http://en.wikipedia.org/wiki/Commer_TS3

No diesel is smooth or quiet...

 

 

[turboplanner]

Well let me put it another way - after 40 years experience with diesel engines, I haven't found any which have managed to beat the Commer knocker for noise or vibration.

 

Still have some doubts - run the youtube video of the TS3 in the mini and watch carefully as the car jumps and lurches around.

 

 

[Head in the clouds]

Remember that the "drive" is from the camshaft, at a 2:1 ratio, .....

This engine is being discussed on another forum as well and, although it is partially shown here in post #107, it hasn't been quite as well pointed out that the output shaft is NOT from the camshaft at 2:1. There is a large gear on the front of the engine which times the two cranks together and which determines the prop speed reduction ratio, and different reduction ratios are provided by using different gear pairs (triples?) of the same pitch circle diameter (PCD), just like changing ratios in a Hewland gearbox.

 

The cam is actually driven off either crank at the back of the engine by another gear pair or toothed belt.

 

 

[bexrbetter]

This engine is being discussed on another forum as well and, although it is partially shown here in post #107, it hasn't been quite as well pointed out that the output shaft is NOT from the camshaft at 2:1. There is a large gear on the front of the engine which times the two cranks together and which determines the prop speed reduction ratio, and different reduction ratios are provided by using different gear pairs (triples?) of the same pitch circle diameter (PCD), just like changing ratios in a Hewland gearbox.The cam is actually driven off either crank at the back of the engine by another gear pair or toothed belt.

Red Ribbon for the kid in the back row

 

Measured from where?As I stated earlier it should be smoother anyway due to the opposed pistons in a single cyl due to the almost perfect balance of internal forces (some very minor cyclical harmonic mass issues from the conrods aside). The comparison to a standard triple is probably not valid in relation to smoothness.

Correct. For a number of reasons TVs should be lower as well, shorter stiffer cranks, no crank pressesion and close to zero primary and lower secondary harmonics.

 

Im guessing your using Suzuki or Daihatsu cylinder heads .

You obviously forgot all about V6 engines didn't you, the heads were designed and developed in England not Japan

 

The Commer TS3 was not smoother,

I'm sorry you seem to have had a bad run with them, yes they are noisy, most 2 stroke diesels are, GM Jimmy etc. but I have different versions of the engine's smoothness from my best Mate who did his apprenticeship on them in NZ (they were big sellers there) and my Dad who has worked on many as well as owned one. Sometimes individual engines stand out from others for various reasons.

 

 

[bexrbetter]

Ok Guys, lovely chatting about this but I myself am going to knock it on the head for about a month till I get my casing molds and the first crankhousing samples back. They said 40 days but most companies in this area overquote time so hopeful for a month.

 

I just don't have more info to offer at this point and might start to frustrate those looking for further info.

 

Thanks for your participation

 

 

[ozbear]

Good luck Bex I hope it all goes well clear sky's .

 

 

[Deskpilot]

Good plan Bex. I personally think that you've already given out too much info on a new design. I sure wouldn't have. As far as my design are concerned, I'd be happy if some-one else want to copy/improve on them, but then, I'm not in it for the money.

 

 

[pog5757]

Bexrbetter,

 

It'll be fascinating to watch this thing take shape.

 

I am curious, though--and perhaps you've looked at it already and have sound reasons--but why not make it a 2-stroke, using one of those electric/hybrid turbos (or whatever they're called) for external scavenging and, perhaps, direct injection for good efficiency? Looks like you could knock the parts count way down that way and save a few pounds as well.

 

Please keep us posted on developments.

 

Pog

 

 

[facthunter]

I spent years designing an opposed piston two stroke with variable port timing and compression ratio. and finally decided someone might find some patent I had unwittingly infringed. It was ( for what it was) quite simple. Simplicity of design is important otherwise we would just go and put a Hyabusa motor with a good redrive in. Car adaptions come and go. Plenty of famous brands have tried and failed to build a successful aero motor. Nev

 

 

[bexrbetter]

I am curious, though--and perhaps you've looked at it already and have sound reasons--

Investment risk, like any manufacting startup, our first model needs to be as simple and as economical to develop as possible.

 

 

[bexrbetter]

Anyway, the mold company are getting along nicely with my finalised crankshaft housing design.

 

 

 

[eightyknots]

Any further news BRB?

 

 

[bexrbetter]

Any further news BRB?

Hi Mate,

 

Just waiting for some castings to be done (drawings above), they said a month but I never really believed it but for various reasons I have no need to be contacting them until after the 20th (July) so I'll let you know after then

 

 

[bexrbetter]

I have been told I have to visit the casting works some time this week to check and approve what they have done - I know nothing other than that but look forward to getting there.

 

 

[gareth lacey]

Good work Bex , give Rotax a run for the money ,we in the light plane sector need an engine we do not have to re mortgage the house for

 

Good luck and i wish you well in getting it out and make lots of money

 

cheers gareth