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

[Vigilant1]

I was thinking something like a 3:1 PRSU from a small automatic trans, 3 AL/Nik chainsaw cylinders, some magic small 4 or 5:1 planetary driving a centrifugal blower rotor (OTC from somewhere) that would be direct driven from a PM DC starter motor. For the kind of simplicity I am imagining, a single carb is a must. Can see the major elements in my mind, but have no idea where to get existing components.

You are okay with scratch designing a 3 or 5 cyl rotary engine (from available bits), working out the details of an electric blower from stock bits (that would need logic circuits to keep i sync'ed with engine demand), scratch designing a PSRU...but an EFI system is right out of the question because it is too complex? That would seem, to me, to be among the simpler things (design and operationally) of the whole undertaking.

 

[Hot Wings]

2 stroke radials can do that.

Is this kind of what you were thinking?

Brushless electric for the blower would save weight - but make the engine electric dependent.
If I were to go to all the trouble of designing this I'd have to seriously dig into spark ignited diesel research.

 

[Kiwi303]

Easiest approach I can think of for spark ignition diesel is the old Diesel+Propane trick in reverse. It just means double the fuel system.

In the classic system the compression ignites the diesel, which lights the propane which carries the flame through the chamber more efficiently allowing better consumption of the diesel droplets (diesel atomises into droplets, propane is gaseous vapour) ensuring better utilisation of the fuel and less unused hydrocarbons going out the tailpipe.

in a spark ignition diesel, the spark would light the propane, which would light the diesel...


what was a workaround to improve power and efficiency in 70's and 80's diesels could be a useful system for a 2020's engine, and with the low propane consumption, possibly even just utilize those single-use small camping stove cannisters.

 

[Vigilant1]

Easiest approach I can think of for spark ignition diesel is the old Diesel+Propane trick in reverse. It just means double the fuel system.
...
in a spark ignition diesel, the spark would light the propane, which would light the diesel...

Pretty cool. Does the lowered CR (since no need for compression ignition) reduce the required mass of the metal bits, putting things closer to a gasoline engine than a typical diesel (for the equivalent HP)? How about the expected torque/RPMs? It would be nice to run slow with high torque to improve prop efficiency.

As a bonus, I'd think there'd be an overall improvement in crash safety compared to gasoline. The higher flashpoint diesel is a huge plus, and the small propane tank is strong and easily made stronger. "Shut off on open line" valves are available. Inverted flight would require some adaptations when using LPG.

 

[PMD]

You are okay with scratch designing a 3 or 5 cyl rotary engine (from available bits), working out the details of an electric blower from stock bits (that would need logic circuits to keep i sync'ed with engine demand), scratch designing a PSRU...but an EFI system is right out of the question because it is too complex? That would seem, to me, to be among the simpler things (design and operationally) of the whole undertaking.

Wasn't thinking of electric blower, but more like a 20VDC brushless drill motor connected directly to blower shaft being used as both starter and generator. The tech actually exists at TURBO speeds, but would be adapted from hardware store bits for 4 or 5 x crank speeds (meaning a fairly large diameter compressor wheel but a custom housing to allow full perimeter feed as each cylinder in rotation demands). Big truck and marine turbos have enough impeller to do that, but shaft ends inside instead of passing through.

Personally, I understand the need for electronics, but in a backyard level of build it screams for simplicity of all mech tech.

 

[PMD]

Is this kind of what you were thinking?
View attachment 115738
Brushless electric for the blower would save weight - but make the engine electric dependent.
If I were to go to all the trouble of designing this I'd have to seriously dig into spark ignited diesel research.

Yes, sort of scaled up Ross with a blower (not shure how these were charged and scavenged nor started, but the one bottom left wheel is interesting.

Spark ign diesel does NOT need a WMD profane bomb to ride along. It is already in use in some multi-fuel designs for military purposes. Going 2 cycle and diesel is of course my personal preference, but I can't think of any 2 cycle chain saws that are diesel powered.

I should mention: with modern HPCR you can shape MEP curve of cylinder pressures so as not to need much/any more mass of material vs. gasoline to contain same. Definitely NOT mech tech but requiring the very latest and best of electronic engine management and hardware to pull it off.

 

[Hot Wings]

but requiring the very latest and best of electronic engine management and hardware to pull it off.

Not so sure about the 'very', but for a small high rpm gear reduced 2 stroke engine multiple injections are likely to be limited with current piezo injectors and cpu speed......I haven't' done any math.

Did a search for diesel chain saw.
Jonsereds XA back in 1954 to 1060 is the only one I could find. Not exactly user friendly.

 

[PMD]

Not so sure about the 'very', but for a small high rpm gear reduced 2 stroke engine multiple injections are likely to be limited with current piezo injectors and cpu speed......I haven't' done any math.

Did a search for diesel chain saw.
Jonsereds XA back in 1954 to 1060 is the only one I could find. Not exactly user friendly.

Piezzo injectors promised more than they seemed to be able to deliver, but current solenoid-type HPCRs can manage as many as 9 cycles at something like 3,000 RPM. Varying the pulse width is of course how "rate shaping" is accomplished (moving the peak of cylinder pressure curve into an area where it is more advantageous re: rod and crank angle.

I wonder if there was a Tim Taylor episode featuring a 5.9 Cummins powered chain saw??

 

[Aviacs]

Spark ign diesel does NOT need a WMD profane bomb to ride along. It is already in use in some multi-fuel designs for military purposes. Going 2 cycle and diesel is of course my personal preference, but I can't think of any 2 cycle chain saws that are diesel powered.

Jonsereds XA back in 1954 to 1060 is the only one I could find.

Rasmus Wiig in Norway, late 1940's, tried like heck to get people to buy into diesel saws. His Comet was actually lighter weight than most gas saws at the time. With fuel injection instead of a carb, it could run, as he often demonstrated, after being dunked completely under in a barrel of water. The saw used a tandor heated with propane stored in the handles and lit when the operator wanted to start the saw. Once started, the tandor continued to glow from the heat of combustion, and the propane was turned off.

Initially Wiig produced them himself in his "Norwegian Saw Blade Factory", later licensed them to Como as well.
Cold weather = lower pressure propane in the small handlebar reservoirs, so they were hard to start when temperatures dropped.
Wiig & Como combined may have sold almost a couple thousand saws, but they threw in the towel in 1954. They designed a new model and contracted the textile company Jonsreds to manufacture them. That's how Jonsreds got into the saw business.
Jonsereds eventually bought the designers out. Jonsreds then struggled along with several differen models of diesel saws including a few hundred for export with glow plugs, until 1957, when they too gave up on diesel & brought out their first gas saw.

With the right contacts in Scandanavia, there may still be enough parts saws in sheds and such for a few engines as you envision. All the saws (engines) seemed to work well & reliably. Just not convenient to start, and the marketing juggernauts of established gasoline saws over ran them, essentially.

smt

Edited: "Alternate option" - Buy the plans and kit from Metal Lathe Accessories, and scale it up.
These run beautifully. I never made one, but the designer demonstrated one on the table in his kitchen for me, once.

MLA Diesel (MLA-17)

mlatoolbox.com

 

[Aviacs]

This post got me curious again, i've been trying to stay away from antique saws 'cause there's too much to do on my airplane.
It looks like someone put a Comet up on youtube.
They have to have run cleaner than this one, Rasmus Wiig seems to have been a pretty serious designer & really thought diesels would be better. But if this is an examply, your airplane would not need a smoke system.



The early saws were 3in ^3/ 48.5 cc
Can't find much on the later versions, but there is a lot on the web about them.
Also seems to be a fair amount of scuttlebutt/"iffy" info & opinions on the saw forums

& of course as i trip through the cellar over parts of my 250cc Disston twins, the idea of a flat 4/500 does come to mind.

No, seriously, there are better modern engines to start with.

smt

 

[Highplains]

I am curious why you only mention an odd number of cylinders for a two stroke engines?

 

[Kiwi303]

Pretty cool. Does the lowered CR (since no need for compression ignition) reduce the required mass of the metal bits, putting things closer to a gasoline engine than a typical diesel (for the equivalent HP)?

I don't know about that, when i was dealing with that it was the early 2000's and was just an electrical solenoid downstream of a regulator rigged to a relay on the alternator output. If volts = 0 relay closed, if volts >0 relay open. Open relay = solenoid open and propane flowing into the manifold. So if the alternator was turning (engine running) the propane was flowing at a single set rate into the engine.

It was a workaround for resetting old mechanical injection diesel pump engines with bad smoking under heavy throttle. The better combustion cleaned up the tailpipe, and there was a small but noticeable boost in power. Weight etc wasn't a consideration, CR was still the same.

 

[PMD]

I am curious why you only mention an odd number of cylinders for a two stroke engines?

Not sure who you are asking, but in my case, 3 is the magic number for 2 cycles and 5 for 4 cycles. These are engines with overlapping power pulses that don't have torque reversals (in the case of 2 cycle triples, they actually do, but very small) to "ring" the propeller - making for a lighter prop and PSRU.

 

[akwrencher]

Anecdote on spark ignition diesel:

A number of years ago I lived more off the grid. Loaned my Mom and her late husband a small Honda generator, a 650 watt unit if I recall. Came and got me one day because it would not start. Well, we often had to refuel these little things in the dark, halfway through a movie or something, and Doug filled it with #1 diesel instead of gas. Kept right on running while hot, just wouldn't start when cold.

 

[TFF]

A proper Russian runs their Trabant on stolen diesel. A friend told me that as of the 1990s the police checked cars in traffic for full fuel tanks. Full tank meant you stole fuel because it was more than the ration you were allowed. A friend ran jet fuel from sumped planes mixed with gas and always had a full tank. He got stopped in traffic for a check. He only got to drive away because he had an uncle in the KGB.

I have another friend who was putting about 10 % jet A in his Taurus. We will call him frugal. Trying to drop his fuel cost with free sump fuel. He did get a n old Mercedes diesel and ran jet but he was going through injection pumps yearly.

 

[Twodeaddogs]

Amateur. Shudda mixed some oil in the Jet A and saved his pump. Allegedly.

 

[PMD]

I have another friend who was putting about 10 % jet A in his Taurus. We will call him frugal. Trying to drop his fuel cost with free sump fuel. He did get a n old Mercedes diesel and ran jet but he was going through injection pumps yearly.

When I was in the aircraft repair biz, many decades ago, we had an office (spelled TRAILER) at the airport and got the daily flush fuel from the jet A pumps - kept us heated throughout the rather cold sub-arctic winter. It was before VW diesels, so I didn;t have a car or truck to burn it in.

 

[mm4440]

Was the Weslake mentioned the same as the Hexadyne P60?
Had forgotten about the Pong. That was a while ago............
Not sure you can call a 1000+ production run a fail in the aviation market? The fact that they are no longer around is significant.

Weslake designed it for Hex, different engine.

 

[mm4440]

I just skimmed this but unsure if the Citroen 2CV was mentioned. Its been proven to work well with a PSRU and the plans can be had from the guy who sells the ULF-2. I always thought that a smaller O-100 type engine could be made from the 2CV pistons (Visa has higher CC) and they are cheap and Nikasil.

Also I just ran across this and it looks promising but its way too big. Wonder if a smaller .75L engine is in the works. Radial Motion – manufacturing light, powerful radial engines in South Australia

Also to address another post on here that mentioned the O-100 would rely on legacy parts with limited supply and production I know that no longer to be the case. I met with Pete 2 weeks before passing and he showed me an engine on a table with all the parts laid out ready to assemble. It had custom Carrillo Rods & Pistons and a few other bits to get away from being tied to Continental. He was looking into certification and that engine would likely have used legacy parts but for the Experimental kit the Carrillo option was there.

RM too big and expensive for this power.

 

[mm4440]

While the Neander (developed BEFORE involvement with Yanmar - but Yanmar dropped their own diesel outboard design and went with Neander) is extremely interesting, and two cycle diesels ARE the absolute best answer to powering boats and airplanes (what makes a good boat engine happens to make a good airplane engine) the things missing on the Shark are the simplicity of what CAN be done and what is there that adds a bunch of weight and costs a bunch of efficiency is the cylinder head. This is from a world of alternative designs that goes back over a century, but the ideal way to do it is with opposed pistons, opposed cylinders (OPOC) as did Hugo Junkers many moons ago. THAT allows for a gear train that can easily deliver whatever RPM drive you want/need and since it has no cylinder head, the parts count is considerably less, thus less weight and no thermal loss through cylinder head.

Just sayin'.

I think the Neander is a four stroke