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

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Hot Wings

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A bit of background:
A little more than a decade ago I decided I needed an engine for my Quickie project because the Onan was no longer available. I built a ½ VW with the intention of using that. Ultimately I decided that it wasn’t a good choice. This lead to thinking about building an engine from scratch and make it a for profit project. At the time I had access to the equipment and time to do just that. To keep it all manageable I decided to use as many off the shelf parts as I could to keep the custom work, and cost/time to a minimum.
Life changed for me and Pete introduced the O-100. The O-100 was so close to what I had designed (market niche, not design) I decided the project was no longer a commercially viable one. I no longer have the resources to build such and engine - but I haven't given up. I'm still working on an inverted 810 B+S, even if it ends up being just for my Quickie
With the O-100 in limbo and supply of the little v-twins looking a little precarious maybe it’s time to resurrect that old project? Thus, this new thread.

Objectives:
Gather ideas, in the spirit of the VP-21 and Motorcycle Of The Air threads, to design an engine suitable for this class of EABs. Project is to be open source so individuals can build from scratch, use cottage industry parts or buy complete FWF packages.

Controlling parameters:
Opposed 2 cylinder.
4 stroke direct drive
Maximum RPM = 3600 ………… less is better.
30+ Horse power. 40 would be better. This means 60 cubic inches (1.0L), or more, if we use 0.5 Hp/cu/ in. as a base line.
80 pounds maximum weight ready to bolt to the engine mount, minus prop and exhaust.
Should run on 85 octane E10 or low Sulfur Diesel (not both – pick one)
As many off the shelf (OTS) parts as possible. Minor modifications acceptable. This means those that can be done with hand tools or at ANY machine shop.
The OTS parts should be sourced from current production or past vehicles that have been produced in million+ quantities.
Simple. No dual OHC, VVT, variable compression, 12 valves per cylinder or antimatter containment fields.
Unless someone comes up with another option it will be presumed that this will mean a clean sheet engine case/block is needed along with either clean sheet heads or those built in the fashion of the ½ VW or ½ Corvair.
Past engines to use as templates:
Onan
1/2 VW
1/2 Corvair
Aeronca E-113
Conteniental A-40
O-100
Franklin 2 cylinders
 
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Hot Wings

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Just to get this rolling my past project started with the VW. Mostly because that is what I had around the shop, was familiar with, and had parts in hand to measure.
A cut down VW counter-weighted crank (Force One style prop flange), VW cylinders and Rabbit rods (Offset ground 69mm stroke crank) were used for the base.
Case was designed for the separate Force One style prop flange.
Chevy small block timing chain, hydraulic roller lifters and a custom camshaft were used in the valve train.
The oil pump innards were from a Chevy transmission.
Heads were to be typical ½ VW. I bought some Harley heads to evaluate…..WAY too heavy.
Cam bearings were stock VW – later changed to OTS chevy.
Main bearings were stock VW except for the prop flange/thrust bearing which was GM.

I’ve had a decade of time to think about this at night when I should have been sleeping and I’d change a few things now because of what I’ve learned and how the automotive market has changed.

Don’t let my starting point inhibit the free flow of ideas!!
 

blane.c

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I have thought for some time that a two cylinder Flathead would be perfect. The trade off of weight for more cubic inches and a flat head with relatively low compression also lowers the parts count. It also makes two plugs per cylinder easy and is narrower than a overhead valve engine. The D-motor flathead is enjoying some success in the eu.
 

Hot Wings

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The trade off of weight for more cubic inches
There may not be an increase in weight over a typical OHV system. We don't have to use iron like the A-40.
a-40.jpg
Flat head won't work with stock VW cam layout, but if we move the cam it starts to look very attractive and compact.
 

blane.c

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All I know is that the 4 cylinder 90hp D-motor weighs about the same as a VW has water cooled cylinders and turns about 3,000rpm max.
So two cylinders smaller could weigh around 80lbs?
 

Hot Wings

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We are never going to be able to cut the weight in half by just lopping off 2 cylinders. Picking smaller support parts for the 2 cylinder can save a little.
80# is still going to be a tough number to reach.
 

Topaz

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So this question isn't skepticism or negativity, because I absolutely and wholeheartedly agree that we need more and different engines in the 35-45hp category. Just want to make that clear up-front.

Because my question is this: What's different here than, say, one of the larger 1/2VW or 1/3 Corvair engines that already exist? What does this project provide that they don't?
  • Just another engine option? We do need that, but another solid 1/2VW supplier in addition to Scott Casler would also solve that problem and provide redundancy in the small-engine market.
  • Cheaper somehow? We'd all love that, but I have a feeling that Scott Casler's margins aren't gigantic already.
  • Using parts off certified engine? Taking over/buying the O-100 project from Pete's estate would give the project a gigantic head-start, as Pete had already wrung the issues out of the O-100 and was in the process of getting ready for production.
What's the benefit of starting another engine development project?
 

ToddK

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The big lesson from the O-100 is to not go it alone. Have an 2nd party involved in terms of development and ownership so that if the unthinkable happens, the family can’t scuttle years of work.
 

blane.c

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The six cylinder D-motor is advertised 163lbs and the four cylinder 128lbs so two cylinders weigh about 35 lbs and so a two cylinder might be around 93lbs. That would be around 1350cc/82ci. So a smaller version could be close in weight.
Also the weights include quite a bit of stuff so would be fair to compare to equally equipped other engine. Baffles to cooler, exhaust or no exhaust etc.
 
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Hot Wings

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Praga B2 is pretty close.
Was not aware of this engine. Very close to meeting the parameters. thanks for the imput!

What's the benefit of starting another engine development project?
Maybe none. But there wont be an option unless there is a project started.

I like the VW, but the truth is it is just a cobbled together conversion that has over the years managed to 'patch' a bunch of problems that weren't problems for a ground bound vehicle to make an acceptable aircraft engine. It's basic architecture is........not aircraft.

Pete's O-100 was a very good project. It could have probably revived a whole segment of EABs and was a natural for the VP-21. 2 problems: Pete is going to be hard to replace and the engine is built around parts that are in limited production.

I've edited my list of parameters to include parts to be sourced from current production vehicles, or past vehicles that were produced in million quantities. This can both reduce cost and assure future part sustainability.

The big lesson from the O-100 is to not go it alone. Have an 2nd party involved in terms of development and ownership so that if the unthinkable happens, the family can’t scuttle years of work.
Quite true. but it took ONE motivated individual to guide/force the project to the point of viability. A team will generally produce an acceptable product but it will never match the effeciency of a motivated and knowledgeable individual.
 

Topaz

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The big lesson from the O-100 is to not go it alone. Have an 2nd party involved in terms of development and ownership so that if the unthinkable happens, the family can’t scuttle years of work.
I wasn't nearly as "in" as some other people on this forum, but I knew Pete, spoke with him deeply about the project both by e-mail and across a coffee-shop table more than once, visited his shop, and watched the pre-production engine take flight in his Cracker Jack for the first time, having flown up to Shafter that morning with a friend.

His family hasn't "scuttled" years of work. That's not being fair. I can't say exactly what happening with regards to the engine, both because I don't know the current details and I have promised not to talk about it, but the characterization here is incorrect.
 

Topaz

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Maybe none. But there wont be an option unless there is a project started.
Fair enough.

I like the VW, but the truth is it is just a cobbled together conversion that has over the years managed to 'patch' a bunch of problems that weren't problems for a ground bound vehicle to make an acceptable aircraft engine. It's basic architecture is........not aircraft.

Pete's O-100 was a very good project. It could have probably revived a whole segment of EABs and was a natural for the VP-21. 2 problems: Pete is going to be hard to replace and the engine is built around parts that are in limited production.
Okay, those are two good reasons. You've answered my question, which was meant only to help focus on the "why." Thank you.
 

Vigilant1

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Don’t let my starting point inhibit the free flow of ideas!!
Just to ask: Why the opposed twin rather than opposed 4? Simplicity, weight vs smoothness, TV?

Not to derail the discussion, but FWIW, a direct drive 993cc B&S V-twin totally optimized for flight (flywheel entirely gone, etc) would likely weigh about 95-100 lbs and be good for 40 HP all day long. Unlike a 1/2 VW, it would have electric and starter at that weight. No big mechanical mods needed (i.e. no new case, crank, cylinders, head, etc) but a new ignition, new carb/EFI, new starter/alternator. Doesn't fit most acft cowlings as well as a flat engine, but turned over...

Good topic, thanks.

Mark
 
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TFF

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Off the shelf parts should come from two camps. Harley and Chevy. Both have just about an infinite catalog and custom parts.

Simplest on paper, turn a Harley Evo from a V to a flat engine. New Crank case and custom cam, and use everything else off the shelf… hopefully. 100 cubic inches is doable.

Chevy parts are such high volume, race parts are cheaper than many stock parts of others. Lots more needs to be done going this way. The thing with Harley and Chevy is you should be able to get stuff custom made with a phone call.

The O-100 could be the grail. Should be. I saw it at Oshkosh. But now it’s not the designers dream anymore; it’s a commodity. I hope the family can come out on top with it for themselves, but the second owners are surly investors. Even if they are enthusiastic, you are betting against the house that it’s not going to turn into a other dream engine company. No matter how hard the family tries to stop that.

Too bad that raw castings of the crankcase were not available. Yes it’s not a bolt together project then, but it would not be any worse off as a home 1/2 VW. Yes only a few could personally machine one, but 3-4 could have made a paying hobby with finish machining. Everything else left to the owner. No it would not have been the gem it hopefully will be, but it would have been a game.
 

Victor Bravo

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I hate to rain on Hot Wings' parade, but I don't think that anything other than a 100% new custom-designed and rather high tech engine will meet his configuration/size/weight/power/drive/RPM parameters.

The smaller industrial V-twins could be bumped up to 40HP fairly easily, but will not meet RPM and configuration targets.

ALL of the "aircraft designed" opposed twins (Aeronca, O-100, Franklin) are 20-25% heavier. Some lightening can be done with a bunch of new castings and better alloys, but that's a new custom engine pretty much.

The half-VW is close to the weight, some work could be done to shave off that 5 pounds without too much aggravation, but you'd be making a new case casting, oil pan, rear case, etc. just like Pete did with his project.
 

Topaz

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... The half-VW is close to the weight, some work could be done to shave off that 5 pounds without too much aggravation, but you'd be making a new case casting, oil pan, rear case, etc. just like Pete did with his project.
Now that would be a worthwhile project - to design new heads for VW's that help solve the heat problems once and for all. Even if you just removed the max-rated/continuous power limitation it'd be a huge step forward. You could keep everything else on the VW - case, crank, rods, pistons, cylinders, valve train, and just focus on the heads themselves.

It's a worthwhile project, but not really the one HotWings is looking to do, which is also worthwhile.

Sorry for the topic diversion.
 

Victor Bravo

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You can weld additional cooling fin area on aluminum heads, y'know. T'aint rocket science. Another 40-50 square inches of total fin area near the exhaust port might solve the entire VW CHT issue.

ALSO, designing a lighter and more aircraft-y case and oil pan (with fins in the oil pan) would be a neat thing too, still allowing all of the reciprocating and rotating parts to be VW based.
 
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