jbirnsch

I bought this on feebay last week. It doesn't run for long and I knew that when I bought it. It is just cool. I know that is lost it's pumping action due to the multi cylinders in the same crank case at different timings. If I add a supercharger to the input do you think it would keep running? RB Innovations makes them for small glow engines. Basically forcing air/fuel mix into the CC should keep it running right?

Jason

wolfy888

One would think so, and I, like you, might be inclined to try to pressurize the intake tract. However, I think that the trouble might more possibly be attributed to timing troubles, meaning that the thing is trying to feed the wrong cylinder at the wrong pulse-point, particularly if the cylinders are fed via reed valves. Seems to me I saw something like this years ago, but the cylinders were governed by a disc-valve setup. Don't know how you would accomplish that, unless you know a good machinist. I'd be curious to see the insides to see what's going on in the crankcase. Remember that two-strokes are a bit funny, since the mixture enters through the crankcase and is sent to transfer ports to enter the combustion chamber, and timing is a function of the ports' depth in the stroke. You knew all this already, right? Very interesting machine, though.

Toad

Super charging wont do it. the case has to be able to draw the fuel mixture in, then compress it to get it go up the transfers. the only way this thing would run a full tank is if all three cyl/ fire at the same time.. that would take a staggered crank with three different crank pins 120 deg from each other. looks like you bought just a novelty engine

Toad

Could be also that only one of the cylinders is "live".. most likely anyway.
I dont see evidence of a piston in the cyl on the right..

R Barnette

My Feedback: (2)

E-MAIL ME IF YOU WANT THE ENGINE TO RUN. You may try typing Barnette Radial in the search, At one time there were several pictures of my engines in the 1/2 A form
[email protected]
Ralph

Mr67Stang

Make it run? Who would want to do that and take away all the mistique[sm=bananahead.gif]

C'Mon Ralph, tell us what it's missing.

OzMo

My Feedback: (3)

UNFIRING minds want to know

jbirnsch

The engine has 3 compression strokes per revolution. I am uploading more pictures of the insides. even if I don't get it to run it is still a cool engine to mount on a static display.

Jason

longdan

I've seen a similar setup (maybe on here or in a magazine) where a guy built a similar one that did use a supercharger. It had a sliding vane pump attached to the back of the crankcase. Worked well, but the power/weight was pretty poor.

controlliner

Ya know what I think it is? This engine has a displ of .147 and the sure start backplate has too small of an intake.

build light

I noticed that first thing but didn't say anything till now because it can be drilled/reamed for greater flow volume. I am not sure if there is room to allow form flow for three cylinders. The hole in the spraybar would need enlarging as well but I think that would be no problem.
Doing this I think would make it more difficult for the oversized crank case volume to provide adequate vacuum for fuel draw.

I hope I am on target with my thoughts. Most of the specifics like how much to enlarge the spraybar and the like are a little beyond me.
I do enjoy following these discussions hoping to learn more.

"I've seen a similar setup (maybe on here or in a magazine) where a guy built a similar one that did use a supercharger. It had a sliding vane pump attached to the back of the crankcase. Worked well, but the power/weight was pretty poor. "

I really think this is more about cool factor than performance and the cool factor is very high on this one! The fact it runs at all is a testament to the builder.

Robert

wolfy888

Hey, guys:
Just a thought to start an argument: If you look at all the other multi-cylinder engines on the market, you might notice that they're ALL four-stokes. I can't quite get my pea-brain around the two-stroke application here. Try Rossi, OS, Ross,and I'm sure there are others, plus all the fantastic home-machined models we've all seen on posts here, like that awesome blown V8, and the V12 that are linked through youtube. I do recall Ross made a flat-four that looked like four .60 cylinders that was a two stroke, and I wanted (dreamed) of getting two of them to put in a Cessna 310, but that's well into turbine-price territory, as the airframe would have been monstrous, like 16 foot wingspan instead of Bud Nosen size. That Tower Hobbies ARF is starting to look really good.....

controlliner

One thing to be aware of with the sure start intake, the plastic that these are molded from is real brittle. I tried to enlarge one I have and the intake shattered.[:@]

combatpigg

My Feedback: (3)

A small venturi will allow the engine to produce good steady runs, just not max power.

hfenn

G-Mark made two stroke radials.

BMatthews

There's nothing magical about the problem. There's no crankcase pressure when running a common case on a radial. The pistons are all moving in a way that there's never any suction or compression of the crankcase charge because the volume of the case never changes due to the way the pistons are all moving. So regardless of the intake size or anything else the engine will never do more than run out the prime as it sits now. You're right in that it needs some sort of compressor to force the charge into the crankcase. A compressor would take the place of the usual crankcase compression we see in single cylinder or opposed twin setups. There was a commercial two stroke radial a few years back that used the rotary vane pump mentioned above. Yeah it did look a bit unweildy and was likely heavy but engines of this sort are done for their own magic instead of high performance.

So the key to making this run will be if you have the tools and knowledge or can find someone to take up such a challenge and come up with the right size of pump to make the engine run. One option that would avoid having to get into a lot of mods to this engine would be to make an external vane pump that is run by a brushless motor. The engine carb throttle and pump motor ESC could be Y'd together to work in unison. And since it's not attached to the engine itself it could be made form easier to work with plastics. All of this kludge up may not be the sort of stuff you'd want to stick into a model but it would be slick to see it running on the bench. How big a motor and how big a pump for this? I have no idea. Some engine logic and number crunching would be needed.

On a stock engine the volume being pumped is the same as the volume swept by the piston. So .049 cu inches. Times this by three for it being a triple makes it .15 cu inches. Toss in a little for a fudge factor and call it .20 cu inches per revolution to allow for any overlap leakage or other factors and get yourself a worst case number. So if you have a vane pump that delivers .20 ci per rev then you need to match the 12K to 15K that the engine will be turning. That's quite doable with many brushless motors but the vane pump may not agree with us. So lets make the pump so it delivers .30 ci per rev. That'll reduce the required rpm of the pump to 8K to 10K and likely make the pump happier. If the motor used to run the pump is running with a 3S pack at 11.1 volts nomimal you'll want one that has a Kv value of 10K/11.1= 901 rpm/volt. Again to allow for speed reduction due to load and other factors lets call this an even Kv value of 1000. How much wattage you'll need I don't know. This would depend on pumping losses in terms of air resistance and mechanical friction. But I suspect that it won't be all that much. Now you just need to get someone that can design and make the pump.

combatpigg

My Feedback: (3)

Here's my idea.

Seal off the transfer ports from the crankcase.
Tap the transfer ports [sleeve valve style] and run individual lines back to a common plenum. A check valve will be needed in each line to establish one way flow towards the engine.
Have a .10 to .15 sized venturi "party bowl" mounted to the common plenum to feed all six intake ports.
If nothing else, this thing could end up looking pretty cool....[8D]

Mr Cox

These tiny radials tend to pup up now and then, below is a picture of the g-mark with individual crankcase spaces and a gear system (no compressor needed). There is also a video of one running [link=http://www.youtube.com/watch?v=d28vqW8pJlQ]HERE[/link].

I've also attached a pdf file (not sure if that works) of a compressor driven engine from germany.

CKLLOYD

THANK YOU MR. COX I WAS GOING TO TRY TO EXPLAIN A VANE SYSTEM THANK YOU FOR COMMING UP WITH THIS PIC.

build light

Bruce thank you again for your explanation. I believe you have told us before but I for one forgot the most important detail of why it won't run as seen.
it is so massively clear to me once again.
Just a couple of nights ago I was explaining to a friend how the reed valve functions and how it relies on both vacuum to pull fuel/air mixture into the crank case past the reed valve and also pressre from the downstroke of the piston to both seal the reed and then force the mixture through the cylinder ports for firing. And yet I looked at this multi and all of this just flew out the window apparantly.

I hope I can retain this in the future.

If the pistons were aligned to fire simultaneously the vacuum would be no problem, but you would lose the super cool alternate firing sound that a good multi provides and that we enjoy so much.

I was thinking about how an aquarium type pump that uses a reed valve could be adapted for this use. lots less machine work required. The electromagnet actuator could be replaced with an electric motor.

Robert

BMatthews

An aquarium pump won't produce anywhere near the volume needed to keep the crankcase charged properly. The engine needs somewhere between .15 and .2 cubic inches of air per revolution. Multipy that by the RPM value at, say, 13K and you have it requireing .2 x 13,000 = 2600 cu inches of mixture per minute. That's just over 1.5 cu feet per minute. You won't find an aquarium pump this side of Marine World that will provide that much air. Or rather you'd need a pretty major pond pump to do the job. Here's a $54 pond pump that won't even make it at only 1.34 cu feet per minute. And I don't know what it weighs but it's got a big handle on it and the pump makes it look small.

http://www.aquariumguys.com/superluftpump.html

OK, here's one that'll work. 2900 ci per minute so you'll be able to either supercharge the engine or allow for a small amount of air bleed. And a bargain at only $111 ! ! !

http://www.aquariumguys.com/pondmaster-air-pump.html

See why I'm suggesting that a brushless motor hooked up to a home made vane pump is a far better option? The good news is that the second 2900 CI/min pump only uses 40 watts. So all indications are that making up an onboard brushless motor supercharger won't be difficult and you can expect a Lipo pack to easily run the supercharger motor for at least one flight and likely two.

jbirnsch

I bought some aluminum stock today and am going to make a new front that will save some more weight. I am also going to make a new back cover and it will have a PTO with pully to drive a RB Innovations supercharger. I will use an off the shelf carb and most likely port that in between the cylinders. The output of the supercharger will go directly to the carb intake. The supercharger also has a tap to pressurize the fuel tank. Can't hurt to experiment. Once it starts off the prime the supercharger should be enough to keep it running by forcing air into the carb and pressurizing the crank case.

The vane pump looks a little too difficult for my machining experience. What is the vane material made of?? We had a vane vacuum pump on the farm for milking machines. I understand how they work but looks difficult to build. IIRC the precision clearance between the sidewalls of the pump was critical. If the side got scored the pump would be shot.

Jason

dennis

My Feedback: (90)

I ran the G Mark 30 radial when it was available. Ran like a sewing machine and produced the power of an 09. Nice mantle piece but I got rid of it.
Dennis

BMatthews

These are more of a novelty than a serious engine. I wouldn't bother with trying to reduce the front end weight. At least certainly not at this point. First is to get an air pump on that puppy. You may want to consider altering your plan for where to put the carb. If it is downstream then the inside of the carb body is under pressure and it'll force air along with any fuel in the line back up the fuel line to the atmospheric vented tank. So no fuel. At least not without a fuel pump. It's far, far easier to put the carb onto the intake of the supercharger and pump the fuel air mixture into the supercharger and then on to the crankcase. That way your carb works like it was intended under normal atomospheric pressure at all points. As a bonus the fuel will provide lubrication to the supercharger.

If you have a lathe available a vane pump is actually fairly easy to make. Look at this sketch. Nothing but regular round turnings with one offset hole. And the slots could be cut using your lathe with a slitting saw blade in a mandrel you can make along with some form of jig that replaces your tool post to hold the armature. Or with some care and a little jig you could even cut the slots with a common hacksaw. Just smoothen up the tooth set with a sharpening stone to get smooth sides to the slots. The vanes should fit decently but don't need to be precision. A couple of thou clearance at all points would be fine and would actually be just what you want. Brass for the vanes with slightly rounded and then polished edges to avoid digging into the side walls would provide the running fit and promote a good oil film to avoid metal to metal or metal to plastic contact. No need for springs, once running at even a moderate speed the centrifugal force on the vanes will hold them tight to the chamber wall. They really are low tech. And at the RPM it would be running at the leakage past the non precise fit wouldn't really be an issue.

Boomerang1

A work friend was converting a coach to a camper & had the engine in pieces.
It was a V6 GM diesel, 2 stroke, supercharged but it did have heads with valves.

A similar idea? Being an injected diesel I suppose it would inject fuel at just the appropriate time but would the crankcase be pressurised?

Or would it be like a conventional 4 stroke with the valves operating more often to fire every stroke? - John.

Should have known!, Google it!

http://wiki.gmnext.com/wiki/index.ph...ropulsion_Game