2 cycle radial

[Dagger]

http://rad-cam.com/

here is the link..this is a 8 cylinder, 2 cycle engine that has a power/weight ratio that is STUNNING.

The next new design for a HOTSAW?
You racers better check it out.

 

[bwalker]

Dagger, I noticed they claim low emmisions. How do they accomplish this with a loop scavenged, non direct injected two stroke BTW notice the cylinders appear to be Stihl pieces.

 

[mikey]

To aid in the visual aspect I would have 8 carbs with a collected exspansion chamber.Wound't it be fun to tune!

 

[Dagger]

Good question BWalker, according to what he told me, Due to the cam instead of a crankshaft, he is able to increase the dwell time at TDC to get a more complete burn. Also the jugs are lower preformance..well, according to what we are used to..from a Zenoah model airplane engine of 3 cube each i think, ported for a much lower rpm level than a saw. He claims the fuel is COMPLETLY burned by the time the exhaust port opens. (so no scavenging effect from a good pipe to help) now keep in mind, the cam/crank turns at 1/2 speed of the pistons...or better said the pistons recip 2 times per revolution of the output shaft. So you might say the piston speed is similiar to a 6,000 rpm engine at 3000 on the output shaft. This design is for an aircraft, and he is trying to keep the rpm 's down so he wont have to use a reduction mechanism and have to deal with the weight. Did you see that 2 pistons fire at the same time, exactly opposite of one an other? , he claims the torque goes sky high due to this. And if ya just coulda seen it..a little bigger than a basketball! cutest thing ive EVER seen

So....how bout 8- 6 cube jugs from a top of the line chain saw I'm thinking!! and yes..8 carbs and a a good pipe! OH YA..look out Robert!

 

[eyolf]

Dagger, thanks for posting. I did enjoy seeing the photos. Sure not letting anybody in on any secrets, though!

I've been racking the old brain trying to think of how he's getting the linear motion (piston) transformed into rotary.

There were some oil-field engines made around 100 years ago, built on the model of the steam engine, with a two piece connecting rod; think large hydraulic ram with the clevis attached to a connecting rod. Is there a situation like this here?

Low rpm, OK. Long rod length/stroke ratio can somewhat increase the effective "dwell" at TDC, but severely limits rpm. Some power spent on excess friction, but probably less, overall, than 1/2 the output of one cylinder, leaving 7 1/2 to output force and heat alone. 4 hp/ cyl? Maybe.

 

[Dagger]

Eyolf, after reading you post , i wondered why you were not getting the motion figured out, so I went back to the Rad-cam site and discovered the movie doesnt work anymore, which was an animation of the principle..I will try an explain it.
It is a variation of the Scotch-yoke principle, which maybe what you are describing in that steam engine, as i am aware of that design being used long ago.
In the Rad-cam, the rod is round and has no rocking motion, like a scotch yoke, it goes straight in and out of the crankcase. Their is a cam inside to take the place of the crank journal..but not a cam like a V-8 camshaft, but what he calles a rotor design.
The bottom end of the rod has a round bearing that rides in a track, captured on both top and bottom by this cam/rotor. the center of the rotor being the longitudinal axis of the output shaft.
TDC dwell time is therefore not a function of rod angle and rod length, but the radius of the track in which the bottom rod bearing follows. In the rad-cam design this enables a dwell time many times longer than a conventional crank and rod.
Picture 2 horeshoes placed feet to feet..sort of a double U shape..or a circle with flat sides, with the track for the rod bearing to follow on the outer edge of the rotor. This is the shape of the cam/rotor in the RAD-CAM, so that pistons 180 degrees apart are on the SAME stroke ...both down or both up you might say, so you have 2 pistons fireing at the same time, directly opposite of one an other. It is not complicated..in fact VERY simple with few moving parts.
I believe The scotch yoke design, like a Bourke-cycle design, or a De-Vaux engine design are all similiar to this theory, and in discussions with the inventor of this Rad-Cam design he admits as much. He told me that he first actually built a scotch yoke style but couldnt make it satisfy him so , with the advent of Computer-controlled machining centers..this cam/rotor design was made possible.
Here are a couple of links to some more current scotch-yoke designs, if it interests you.

http://devauxengines.com/

http://bourke-engine.com/ani.htm

 

[eyolf]

Thanks for the explanation and the links, Dagger. I understand the principles pretty well from your description, thanks. Some of those same oilfield engines I've seen used a similar system (in reverse) to operate valves...kind of a low-moving-part-count desmodromic system.

I noticed that the animations on both pages were attributed to a fellow named Wolfe; assumption is that there is a relatively small cadre of folks playing around with this stuff, most are aquainted with each other.

Another interesting point I gleaned ( I think) from the Bourke site was the claim of the engine being self-supercharging. Since the volume of the space behind the piston must necessarily be reduced by the volume the piston rod displaces, the engine will never be truly supercharged, will it? "X" volume of air at a certain temp and pressure, forced into a larger space will reduce pressure. Since conventional methods of scavenging and intake "ram effect" are negligable at the speeds we're discussing, total BMEP will be pretty low, I'd say.

On the other hand, having so many power stokes/ firing cylinders per revolution probably really makes up for it.

Again, thanks for sharing.