... perhaps the question should be what exactly can and should be done to the half-VW to create a better 80 pound 40HP HBA engine?
Yes, the heads. I know, and appreciate, the well-founded desire of HotWings to address the other issues of the 1/2 VW, but heads optimized for aircraft would seem to be the low-hanging fruit that could make a very big difference without taking on a boatload of additional work. Better cooling, valves and ports appropriate for 20hp/cyl at 3600 rpm, optimized location for a second plug, and even a standard spot for a CHT probe so we can all finally be talking about the same thing when we refer to CHT. Extra credit if we can get the induction and exhaust ports a little more conveniently located.Now that would be a worthwhile project - to design new heads for VW's that help solve the heat problems once and for all.
^ This. Emphatically this.Yes, the heads. I know, and appreciate, the well-founded desire of HotWings to address the other issues of the 1/2 VW, but heads optimized for aircraft would seem to be the low-hanging fruit that could make a very big difference without taking on a boatload of additional work. Better cooling, valves and ports appropriate for 20hp/cyl at 3600 rpm, optimized location for a second plug, and even a standard spot for a CHT probe so we can all finally be talking about the same thing when we refer to CHT. Extra credit if we can get the induction and exhaust ports a little more conveniently located.
A (big) bonus from the business perspective: the flying full VW market can use these, and the number of those is probably always going to be larger than the 40 HP market. Heads don't last forever, so planes now flying may soon be your customers, too.
IMO, optimized heads look to be the "70% of the result, 10% of the effort" proposition when compared to a clean-sheet engine. But, I'm no expert (and not the guy doing the work!)!
HotWings has already been stewing on this for quite a while, so I'm just piling on.
The (smaller) valve and port sizes we need compared to normal street/racer heads won't make most car guys happy. If anything, make the fins the size we need but maybe easy to trim off to fit within the standard tin if a car guy wants to do that. (Or, if Hot Wings wants to chop them and sell them).If you could make those magic Hot Heads™️ fit under the standard VW cooling tins a bunch of car guys would want them too.
Definitely an engine needed in that space, but I think that's a lot smaller than Hot Wings had in mind.Off topic but something might be nice for Part 103
Much simpler two stroke motorcycle parts if it's in line.
Press/bolt on a flange and somehow get hp at low rpm. 20 hp 20 lb?
Everything but prop and exhaust ready to hang on a motor mount. I'd be happy with hand prop but most probably would not. No integral electrics so the builder can stay clear of FAA requirements for airplanes with electrical systems. Alt/gen can be added later.But what does it include?
De-rail away! If there is a better way it is probably best to figure that out early in the process?Yes possibly, but it would de-rail the concept of this particular thread.
significantly better than the Casler?
Better VW heads would be a smart business, and engineering, move but:would seem to be the low-hanging fruit
My current selection of OTS parts gives 1.6L (98 in^3) with a big bore and 1.44L (88in^3) with small/stock bore. This is with an offset ground 89mm (3.5") VW crank - so not totally OTS. The nice thing about an offset grind is we can use cranks that are otherwise unusable due to a spun bearing if cheap is the goal for a scrounger.No combination of these will get you to the required 1.2-1.3lt displacement in a 2 cylinder boxer
That's true. And making a (significantly) improved cylinder head for the existing engine won't be as rewarding as any eventual "closer to perfect' clean sheet design of your own. OTOH, a commercially successful product could fund the more perfect engine. Even if funding isn't a concern, the HotHead would get your company established as a player in this business space (with all the reputational, retail channel, and manufacturing advantages that has). It could be a stepping stone, and also do a lot of good.Better VW heads would be a smart business, and engineering, move but:
I probably sound like a stuck record - even VW with the Tp IV and Chevy with the Corvair recognized there is a better way to design the cam and moved things around. A head that works better with the stock cam is possible but it also locks that head into being used only with the current VW.
Even earlier Douglas motorcycles in Britain made motors for aircraft and drones.The past 40 years are a chronical of failed small 4 stroke engine projects:
Global 7892 (2 Cyl, 32 hp, 76 lb) - based on VW parts with new case etc but claimed to be about 10 lb lighter. Hundreds made.
Mosler MMCB (2 Cyl, 38 hp, 85 lb) - further development of the global engine (more than 1000 made)
Hapi Hornet (2 Cyl, 35 hp, 74lb) - small number made. Basically a better 1/2 VW using the Scat individual heads
Aeromotion Twin (2 Cyl, 52 hp, 100 lb)
Emdair Weslake W40/50-73-02 (2 Cyl, 50 hp, 85 lb)
Emdair Weslake W44/60-77-02 (2 Cyl, 60 hp, 85 lb) saw limited production (I have seen one)
Technopower II Twin (2 Cyl, 50 hp, 77 lb)
KFM 105 (2 Cyl, 40.5 hp, 88.1 lb)
KFM 112 (4 Cyl, 50hp, 99 lb) - limited production - this is the engine that the Jabiru was inspired by when KFM stopped production
Jabiru 1100 (2 Cyl, 40 hp, 88 lb) - only prototype made
Lotus Magnum 2.25 (Eipper) (2 Cyl, 25 hp, 31 lb) - prototypes only - the project died with Colin Chapman
Lotus Magnum 4.50 (Eipper) (4 Cyl, 50 hp, 56 lb) - prototypes only - the project died with Colin Chapman
Pong Dragon 35-1.4 (6 cylinder, 2 row radial, 35 hp, 46 lb) - prototypes only
Rebel Twin 2-45 (2 Cyl, 50 hp, ??lb) - prototypes only
HKS-700E (2 Cyl, 60 hp (55 cont), 121 lb) - 1000+ produced.
PAL-95 (2 Cyl, 65hp, 137 lb) - small number produced
and I am sure there are more ....
Also remember the conversions of 2 cylinder DAF and Citroen auto engines ....
The Franklin 2A-45 etc is probably the most recent certified production engine in this class. A few might still exist if they haven't shaken themselves to death !
Every single one of those projects failed. Some of them had significant resources behind them (Lotus, HKS, Jabiru). I would start by asking why they failed and what is it about a new project that will succeed where all these previous projects failed. A better 1/2 VW has already been done (Global --> Mosler + Hapi Hornet) so why reinvent that ? Someone was selling the manufacturing drawings for the Mosler engine recently.
Why did all these projects fail ? Failure to read and understand the market ? Did the cost of manufacture not meet what the market was willing to pay for a 40-50 hp engine ? Vibration ? Under resourced ? (clearly not in some cases). Bad layout - not suitable for installation in an aircraft ? Reliability ? Market resistance to new engines ?
Also designing and producing a new engine is not easy. Jabiru and Rotec have had significant issues and Jabiru has produced something like 6000+ engines (hopefully the Gen 4 engine has fixed the issues).
The most successful conversion of an industrial engine for aircraft use is one that no one has mentioned. This is the Bailey V5 paramotor engine. 20.5 hp, 35 lb including re drive. This is a very extensive modification of an industrial engine with new case etc.