The rise of FrankenEngine - An engine for the VP-21

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Tiger Tim

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Oh, and for those of us woefully unqualified to design an engine, if we’re locked on two cylinders what are the advantages/disadvantages of opposed versus vee versus inline engines?
 

Vigilant1

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... 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?
Now that would be a worthwhile project - to design new heads for VW's that help solve the heat problems once and for all.
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.
 
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Topaz

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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.
^ This. Emphatically this. 😊
 

Vigilant1

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If you could make those magic Hot Heads™️ fit under the standard VW cooling tins a bunch of car guys would want them too.
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).
 
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Victor Bravo

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HotHeads ! That's it, Tim you're a marketing genius!

The bit about these being relevant to the trillions of automotive VW users, who would also love to solve the well documented cooling issues, is probably a BFD.

'Wings, if you needed a kick in the pants to do this, I think a much bigger opportunity and paycheck than you imagined is a-knockin' on the door.

(edit) the performance car guys would probably buy new cooling shrouds to fit the larger fins if it kept their engines running better at high power.
 

TiPi

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I have pondered the same/or a similar engine built from OTS parts for a long time as well.
To make this "40hp" engine attractive to a wider user group, a direct-drive engine with 3,600rpm max speed is not suitable. Many of the potential users fly slowish aircraft (Part 103). Europena countries are introducing (or have already) SSDR-style regulations (Germany, UK with 120kg max empty weight). They do require 4-strokes due to environmental (noise) regulations.
To make it appealing to a much broader fleet of aircraft, this engine needs to be able to swing a 1.5-1.6m (59-63") prop, limiting the rpm to maybe 3,100 redline. This requires more displacement or a re-drive (avoiding that for TV reasons at this stage).

Comparing a few industrial & converted engines (incl discontinued aircraft engines) and the O-200 shows that you need about 1.2-1.3lt displacement to achieve that (40hp at 3,100rpm). As a side point, the O-200 has one of the highest power/cm3 for that rpm, same level as the B&S 993cm3 engine with EFI!

Now, what is available in engine parts suitable for this engine? If it is not OTS, it would have to be custom made = increased cost (selection limited to OHV engines).

Cylinder/cylinder heads:
Jabiru Gen 4 (alu, 97.5mm)
VW (steel & alu cyl, 87.5-94mm, alu head)
Honda iGX700 and iGX800 (alu cyl & head, 78 & 83mm)
Harley???
BMW R100 (alu, 94mm)
O-200 (alu cyl & head, 103.2mm)

Crankshafts (only considering forged/billet):
VW (69 to 78+mm stroke)
Vanguard (73.4 - 86.5mm)
Honda iGX700/800 (72mm)
Jabiru (74mm)
Kohler (Midwest forged 70-79.3mm)
BMW R100 (70.6mm)

No combination of these will get you to the required 1.2-1.3lt displacement in a 2 cylinder boxer or V-twin configuration other than the Jabiru, BMW R100 or O-200 with a B&S crank (V-twin).

Looking at costs & availability, the only cylinder that sticks out is the Honda iGX800. One-piece cylinder and head casting with cast-iron bore.
I would design a simple engine around the Honda cylinder with either a VW crank (for a 4-cylinder boxer) or a Kohler/B&S crank (3-cylinder radial).
 

proppastie

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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. Or use a small prop at higher rpm. 20 hp 20 lb?
 

Topaz

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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?
Definitely an engine needed in that space, but I think that's a lot smaller than Hot Wings had in mind.
 

proppastie

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As to a homemade case I have often thought about one made from bolted together aluminum plate. ...stack drill and ream for press fit crank bearings....just a drill press.
 

WonderousMountain

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The best configuration for a DA-21, is a regular three cylinder.
Straight, with removable head AND cylinder bank, ladder case,
Single Cam, bell housing - Planetary Reduction unit - Balance
shafts (2). Just get it very very light.

IF you went to four Cylinders, these could be used.
OTS part for 250cc Moto Engine. How many lbs?
HTB1qBs3HpXXXXXZaFXXq6xXFXXXJ.jpg
 
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Hot Wings

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But what does it include?
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.
The rest are just details needed to make the whole...........IMHO

Yes possibly, but it would de-rail the concept of this particular thread.
<< >>
significantly better than the Casler?
De-rail away! If there is a better way it is probably best to figure that out early in the process?
<< >>
Significantly better?
As far as sustainability - Yes, I think we can do much better.
Performance - maybe a little better. We can build with more displacement if we look a little outside the VW realm.
Cost - in the near term, probably not. Once the good VW parts start to really dry up then maybe.

would seem to be the low-hanging fruit
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. A 2 piece head, similar to the 911 heads or the scat 2 piece heads, would help make the base head work for both the VW and for a clean sheet case/cam.
I don't have the imagination needed to design around the cam architecture. Maybe someone else does............

No combination of these will get you to the required 1.2-1.3lt displacement in a 2 cylinder boxer
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.

I am kind of surprised that no one has used the Honda aircraft style cylinder/head for something like this. It just looks so much like 'aircraft'.
 

Vigilant1

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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.
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.

Anyway, this is off topic for this thread.:(
 
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Hot Wings

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I like the name HotHead! Brings to mind some interesting related artwork for the 'brand'.

When I first started this project I did have intentions of making it a for profit enterprise. Life has changed and I doubt I'll ever be in a position to make any money from this. At this point money is not my goal.
The VW has been improved about as much as it can be to make it into an aircraft engine. I think it's time to take the next step in the evolutionary process. The Mosler/Global were on the right track but only went half way down the road.
 

Geraldc

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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.
Even earlier Douglas motorcycles in Britain made motors for aircraft and drones.
https://www.douglasmotorcycles.net/aa-files/images/aero-nut/2014/identify-engine-01-900.jpg
1626406013485.png
 

EzyBuildWing

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VW 1834cc Industrial Engine is rated at 42hp continuous at 3000rpm. or 46hp at 3600. Compression ratio 7.7 : 1
Max permissible oil temperature: 120 degrees C.
Source: VW Germany. DIN Rating.
For a 3000rpm propeller, that's about 46cc/hp for continuous operation ........or 2.8 cubic inches per hp, which is about the same the Lyc in an R-22. is de-rated to.
Maybe a 40hp VW culd power a Moni motor-glider ok?
 

Pops

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The max torque of the 1200 cc, 40 hp engine is at a lower rpm than the 1600 cc engine. When going from a 1200 to the 1600 with a prop, the difference is not as great as you think.
In the VW bug, with a 1600cc and dual port heads, VW got the advertised 60 hp at a higher rated RPM. The reason for the dual port heads. On a straight drive VW engine, we can't turn those rpms for the airplanes we fly.

The 42 hp continuous of the 1835cc industrial engine at 3000 rpm is about right. I cruise my 1835 at about 2700 rpm and by the fuel burn it making about 33-35 hp .
 

Vigilant1

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Just going back to the B&S parts bin: The single-cylinder 33 series engines (their biggest singles) have a bore of 93.9mm and a stroke of 77.7mm, for a displacement of 540cc per jug. The official gross (i.e. "exaggerated") HP chart lists 19 HP at 3600 RPM and 18 HP at 3200 RPM (to accommodate the longer prop cited by Tipi). If we knock off 10% for an air cleaner and exhaust, that would give a two cylinder 1080cc (66 cu in) engine 34HP at 3600 RPM and 32 HP at 3200 RPM. That's a pretty conservative HP/displacement value, enhancements might be possible (flow, CR, etc) while still maintaining good reliability. After all, the heads on a flat twin are easier to cool than those on a 4-cylinder engine.

If the forged crank from the Vanguard 54 series (896cc) (78mm stroke crank) can work with the available conrods, then that would be one less thing to scrounge up or make. The tapered shaft PTO cranks are offered on the gasoline 54 series engine, so should be easily available.

Clearly, this is the most superficial look, but an engine built around these parts (or similar ones) would appear to be capable of meeting the criteria of 30+ HP at 3600 RPM (preferably less RPM) as given in the first post. Still, even with OTS heads, cylinders, pistons, conrods, crankshaft, bearings, etc, designing and building an engine would obviously be a ton of work.

Mark
 
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DaveK

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I think making a “reversed” new head for the half VW with better fins is the way to go. Individual heads that place the exhaust port pointing to the back or angled down, but in the back. Would need a custom cam, but that shouldn’t be difficult as the lobe locations along the shaft would remain the same. Intake coming from top as usual, just towards front of head. I’d think that would help with cowling.
 
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