A new Oz engine on the way?

[geoffreywh]

the same will happen with Chinese manufacturing as happened with Japanese manufacturing in the early sixties. It was know as Jap Crap then. (Ridiculous, I know, I bought a Yamaha YDS3 in '65 and blew all my mates into the weeds) People Will find out, and they will be converted.................

 

 

[geoffreywh]

any updates or news for us?

 

 

[Russ]

I'll recap for you as well camel and others, after 13 pages or so things can get lost .. 

 

THE ENGINE: The engine concept is quite simple but for a variety of reasons has had no purpose until more modern era. The design is of a twin crankshaft, opposed piston (OP) engine of 3 cylinders which contain a pair of pistons each aiming at each other.

 

 

 

Why: Balance and compact are the main reasons. It's not hard to imagine even for the non-mechanically minded. When you catch a ball you feel the kinetic force strike your hand pushing your hand backwards, now imagine if 2 balls from opposite directions hit your hand at the same time, yes it would hurt, but your hand wouldn't move being pushed back and forward at the same time.

 

 

 

It's similar in an engine, when the piston reaches the top of the cylinder and the crankshaft tries to force it downwards, the piston doesn't want to change direction and tries to lift the crankshaft up with it and the opposite when it reaches the bottom off the cylinder, each time this happens you get a small jolt - this is a very simplistic explanation of what causes primary vibrations in engines and the reason your car has big rubber engine mounts to absorb them even after the manufacturer has designed and balanced the engine to the best of their ability.

 

 

 

In an opposed piston engine such as I am aiming for, the forces created by one side of the engine going one way are equalled by the other side of the engine going in the opposite direction so you have zero jolts, i.e. zero primary vibrations in theory in much reduced secondary vibrations.

 

 

 

Also with the simple layout of a OP, the design allows a standard 'off the shelf' automotive head to be used and as that is the single greatest expense of an engine, costs can be cut dramatically.

 

 

 

So an OP engine with a common automotive head afixed on top will take something like this basic form (sample only, not indicative of actual engine) ...

 

[ATTACH=full]23554[/ATTACH] [ATTACH=full]23555[/ATTACH]

Common knocker was the term used 40plus yrs ago, theses engines were quite common ( English made )

 

 

[facthunter]

Commer Knocker had different crank arrangements. The Junkers Jumo aircraft engine is similar., with geared cranks Nev

 

 

[JabSP6]

Hi Bex

 

Great to see things progressing for you on this motor.

 

Now that you have the 2 crank case halves, cranks, bearings, oil pumps etc i was just curious if your target of 70kgs for the complete motor is still within reach?

 

Do you have an update on the cylinder casting yet?

 

Can't wait to hear your results of the first run of this great design.

 

Keep up the great work Bex

 

Safe Flying

 

JabSP6

 

 

[Bandit12]

I'm really interested, because I think it is rare for the public to actually see how it all is developing. I need to pick something to build that needs an engine of this size.....

 

 

[bexrbetter]

Now that you have the 2 crank case halves, cranks, bearings, oil pumps etc i was just curious if your target of 70kgs for the complete motor is still within reach?

Do you have an update on the cylinder casting yet?

Weights are on target but I reckon there's always something you miss so may end up a little over.

 

I've just been knocking up some variations for the center casing both in real material and in CAD and waiting to talk to a few component suppliers which has been difficult for the last month with all the holidays we've had here. I'm not going to show what I'm doing there just yet until I decide if it should be protected or not.

 

The Junkers Jumo aircraft engine is similar., with geared cranks

Yes, does offer some visual reference but of course the Junkers is a 2 stroke diesel.

 

 

 

[DrZoos]

Can i first say man you have guts and balls taking this on and i absolutely apluade you and encourage you to continue on irrespective of what the critics say. Well done

 

My my concerns would be.

 

Two cranks, two crankcases, two lots of bottom end bearings, if anything does go wrong. Also the heads or lack of heads looks mighty difficult to do a top end job of any sort.

 

I would encourage you to put thousands of hours on a few test engines in jigs first rather then take on the liability and bad feedback of having customers test the engines for you with their lives, like a few others seem to do.

 

 

[bexrbetter]

My my concerns would be - 1/

Two cranks, two crankcases, two lots of bottom end bearings, if anything does go wrong.

Or a lot more bearing area spreading the loads and heat.

 

My my concerns would be - 2/

Also the heads or lack of heads looks mighty difficult to do a top end job of any sort.

The cylinder head will be a common OEM product straight off the shelf and is one of the reasons the engine will be cheap and highly serviceable/repairable by the owner.

 

I just had a forum visiter from Oz last week and he was quite encouraged with it all and thanks for your kind words too.

 

 

[DrZoos]

What about getting to replace a piston / rings

 

How is that done, do both cranks have to be removed ???

 

In regard to two cranks sharing the load / heat. I personally have never had a crank or bottom end bearing fail, but i have had lots of top ends let go and destroy the bottom end surfaces...

 

So im not convinced on that one, but hey, i know not much compared to you on this topic

 

I guess at least only one crank will get damaged since they are separate...

 

 

[Yenn]

G'day Bex. I havn't really watched all this about your engine but are you correct when you say the loads from piston reversal will cancel out. i woul have thought that each big end bearing would have the loads and they would not cancel. Both crankpins on the one cylinder would be reversing at the same time so therefore double the load. A standard cylinder head at the centre would be wider than your sketch shows. How would it all fit together?

 

 

[bexrbetter]

G'day Bex. I havn't really watched all this about your engine but are you correct when you say the loads from piston reversal will cancel out. i woul have thought that each big end bearing would have the loads and they would not cancel. Both crankpins on the one cylinder would be reversing at the same time so therefore double the load

Hi Mate,

 

I was refering to the primary forces cancelling each other out, the 2 bottom ends won't see any difference in loading than usual and there is certainly not "double the load".

 

A standard cylinder head at the centre would be wider than your sketch shows. How would it all fit together?

There's plenty of room.

 

 

[Guest Maj Millard]

Bex, I own a little Hirth F23 which I did about 275 hrs with. Has a similar 'boxer' type operation but with the two cylinders firing at the same time, on the out stroke. The timing on each cylinder is staggered about 5 degrees from memory from one side to the other.

 

I once asked the dealer why this was necessary, and his reply was to smooth things out a bit...if both fired at the same time it wold tear the engine apart in a short time.................Maj.....

 

 

[bexrbetter]

Bex, I own a little Hirth F23 .. Has a similar 'boxer' type operation .

Hi Maj,

 

Not even remotely similar, mine is an "opposed piston engine" not a horizontally opposed engine, common mistake.

 

 

[Guest Maj Millard]

Doesn't matter, you may still want to stagger firings to achieve smoothness................Maj......

 

 

[geoffreywh]

Err? stagger the firings? " an opposed piston engine has ONE combustion chamber per two pistons. What is there to stagger?

 

 

[Old Koreelah]

Only slightly-related, but when racing Ducatis started using twin-plug ignition in the 70s, a slight delay between the two sparks was found to be advisable.

 

 

[Guest Maj Millard]

Err? stagger the firings? " an opposed piston engine has ONE combustion chamber per two pistons. What is there to stagger?

Well if it's an aviation engine it'll have two plugs won't it ?.......Even radial engines which are smooth to start with, stagger the firings a little.......Maj.......

 

 

[DrZoos]

I remember some le mans cars in the 90's going for 3 plugs in the pursuit of hp and fuel efficiency. It didnt last long, they found better ways of producing power from chamber dynamics and flow. They seem to use the offset to manage intake and exhaust flows more then anything. They found pretty significant power increases , especially in some motorbikes and i think its real benefits are only just being realised now, especially by bmw who seem to have managed to get huge power increases and fuel efficiency from their bike engines without wholesale changes, using mapping to improve flows and burn characteristics and if you read some of their sales blurbs they are definitely relying on some offset of ignition timings to achieve it.

 

 

[Guest Maj Millard]

The term for it is 'prolonging the burn', with no unburnt fuel present in the exhaust gasses....................Maj......

 

 

[Robert]

Maj "I own a little Hirth F23"

 

What do you think of the Hirth F23 motor any good ????

 

 

[DrZoos]

I think "complete shaped burn" is a better way to describe it. just sayin

 

 

[facthunter]

The dual plug concept with aircraft was for reliability.( Supposedly you could keep running with one plug or magneto out). Most of them ended up at opposite sides of the combustion chamber. An effect of this was to reduce the "advance" of the ignition timing the engine needed, but modern head design gets far less advance today usually with one centrally mounted plug which suits a four valve head very well. Some engines fire simultaneously and others have a small lead of one over the other. ( one or two degrees with a nominal timing of around 28) The idea of running with one plug out should be considered fairly unusual as the engine runs retarded and hotter. That's why you get a rev drop when you check your magneto's. When the plugs are closer together (as in a Jabiru) the normal rev drop should be less. Nev

 

 

[Keith Page]

Sum Yung Gai coloured in the engine using the recent screenshots[ATTACH=full]23270[/ATTACH]

Hi Bex

I was having a thought and some thing may have been said somewhere else and I have missed it.

 

Could the head go on the bottom of the block as this would help with the plumbing of the exhaust when installed in the aicraft.

 

With the head on top of the block what a pain getting the exhausts under the fuse when one could start with the pipes at the bottom.

 

Regards

 

Keith Page.

 

 

[geoffreywh]

well, let's have a much smaller head on the top with one valve (inlet) and one on the bottom (ex). more expensive but I do like symmetry