Just a quick question as to wich one of these cylinders would have more power and or better performance.There the same size,bore,stroke,ect...The only difference is that the base flange is a little bigger on the one.They are both off a 14cc echo.

Well Buck, my gut feeling is the one on the right. But then who knows, maybe those transfer port dividers point the flow more efficiently and make more power?? It also appears there is a difference in the exhaust ports, and that perhaps the one on the right has a slightly higher compression ratio. (Hard to tell in the pics....)

Unfortunately, you won't know until you do a back to back comparison. (times 2)

BTW, it's not too tough to change that engine over to a 21cc cylinder if I'm not mistaken...


AV8TOR

I knew youd be the first to respond.I sent the other cyl"s(2) to frank for new rings since he didnt have the correct size so hes fitting the rings to my pistons and cylinders.I have 2 echo hedge trimmers with 21"s on them that run so i might pull one apart and see if the pistons will fit rod and cyl case..I bought 3 14cc from indiana but unfortunatly the base is smaller so the cyl bolts dont line up.So im trying my own twin.I tried to drill the crank like you guys did on your bme"s but i dont have a carbide bit or boring bar(my bar is HSS).
On another note,if im right.If the pin for the ring rides in the corner of a cylinder between the ports,ect,then the bridges arnt needed because the pin(ring end gap) is in constant contact with the cylinder wall.The piston on the right has no bridges where as the one (2) that came with my twin have a full bridge on exhaust and only have a half of one on intake.Well,ill see how it runs with franks upgrade.Who sells carbide bits for less?

It is tough to tell by the pictures... But the one on the left to me seems to have the smaller combustion chamber.
and the bigger ports.

I copyed them and made them full screen.

The smaller the combustion chamber the higher performance they ususlly are.

I once converted a 16cc to a 21. If one searched hard enough, you might even find comments about it here in the forum. I had to do something about a mismatch with the wrist pin, but I just can't remember now what it was. If I have time later I'll try to research it here in the forum for my old posts. But anyway, it worked!! (At the time I was trying to come up with something lightweight to use on .60 size planes, and the 3 bolt 16cc crankcase was lighter....)

AV8TOR

Thanks Ralph.Thats what i was thinking,when ya look at the base its bigger.Thats why the cylinder looks smaller.There both 14cc because the pistons from either engine fit the other.The one on the left also has the bridges in them.
I know what ya mean Av8tor,i have the 16cc with the 4 bolts and right now with the engine all converted RTF without a prop or ign it weighs 2.5lbs.It has a stock carb but kens muffler.Dont know what im going to do with that yet,it has the nice stock round cyl fins.unless i get another and see if theyll fit my 14cc parts.

AV8TOR

Didn't you make bushings for the wrist pin?

Av8tor,do you remember any words you used in the opening title,ill go look.Maybe echo wrist pin,echo rods,anything.If they needed bushings would some of the thin walled K&S brass tubing work or any thin walled brass tubing.I have different sizes of that right now for making sensor tubes.

He did this a few years ago, but the way I remember it is that he
made a bushing for each end of the piston.
Put the smaller wristpin and bearing in and inserted the new bushings
so they would make up for the smaller wrist pin in the larger piston.

This was before he moved to Arizona and after he crashed his first big stick.

The engine did well at lower elevations but was weak at the new elevation.

I can't believe I remember all of this.

Av8tor does this help you remember the rest of the story?

Yeah, I'm surprised you remember all that as well!! You jogged my memory somewhat. I do vaguely remember making some bushings for the piston. I think I made them out of aluminum tubing. I'll try to search some for the thread tomorrow if I can. It is definitely several years ago that I posted about that conversion.

AV8TOR

Here it is.... A copy and paste of the original post from 2003:

Well, as I had mentioned, my 16cc Kioritz powered Big Low Stick was a little underpowered here at my new location with a field elevation of 4200' and temps near 100 degrees. Engines lose power at the rate of about 3.5 per cent per thousand feet elevation. That was enough to take my Stick from being a nice flyer to being rather doggy.

So....

I had a Kioritz 21 cc cylinder lying around, and I decided to adapt it to my 16cc crankcase. The bolt patterns, crank stroke, rod lengths, and piston compression heights are all the same. The only difference is the wrist pin sizes, (and of course the bore size). The wrist pin in the 21cc piston is about .060" larger. I used some 6061 T-6 aluminum tubing to make bushings for in the wrist pin bosses in the piston. This would have enabled me to use the stock, 16cc wrist pin, except the pin was a bit too short. So I used part of a drill bit to make another wrist pin with the original diameter, but the longer length of the 21cc wrist pin. The wrist pin retaining circlips were a bit narrow to retain the smaller diameter wrist pin so I added washers trapped between the new bushings and the keepers to be sure the wrist pin was well retained. I also had to make up a couple of small spacer washers to place on either side of the con rod for spacing. The only other modification was to bore out the crankcase where the cylinder fits in a very small amount. This was only about .030" and only about 1/4" deep, and I did it with a dremel and a drum sander tool.

All in all, it was fairly complicated and I don't recommend it unless you are very handy, or a machinist, but it turned out really well. I rather did it as a challenge, and because I had the parts and the need. It turns the same prop 800 rpm's faster than the 16cc did. That definitely makes the difference in how the model flies!! Hope you find this all interesting...

Take care,
AV8TOR

Thanks to Av8tor and Ralph,im going to see what happens when i get my items back from Frank and see how it runs first.But i would be jumping from 14cc to 22cc.Or i could go from 14 to 16 but thats not much to mess with.Im going to pull the cyl off of my 16cc and see what the base size is and what the ports look like in there.(think i need a new ring(s) anyway).That is an excellent idea,i would have never thought of a drill bit.Good memory Ralph,ive been in this conversion forum for so many years and read i belive all of av8tors,yours,captjohn,bme,ect...all the regulars i dont remember you all but i dont remember that one.Im gonna have to go check my profile and see how long ive been here.
Well,im on my way now,here goes the memory!

You joined 10/16/2002 if I remember right ... LOL.

The date is under your name by your posts.

I've been wondering ....

In a milti cylinder gas-glow engine.

How far a part, in degrees, could the first cylinder and the last cylinder fire

and not effect the intake of the last cylinder.

I've been thinking twin or even a 3 cylinder engine.

I was thinking the same thing along the lines of a 3 cyl radial but i dont think it could be done as a 2 stroke.I went to--- howstuffworks.com---and put in radial engine in the search bar and looked at the working diagram.But it was a 4 stroke.Could somone use a master rod and 2 articulating rods and all 3 cyls would fire at the same time so you would still have negative pressure in the crankcase.Then use a reed carb on back of engine like ryobi.The back of ryobi would be back of engine so all ya would need is a round stock of aluminum,flatten on 3 sides,mill a simple round housing that looks like a prop hub and turn it backwards to bolt onto the case.This would hold the front bearings and seal.Maybe i could find a way to draw one up.

Forgot,3 axisis on the same plane cant fire at the same time.(along with other desighns).Right?

If I knew for sure how many degrees between the intake closing and ignition and the exhaust opening
that would determine the angle, or placement of the cylinders and when the last cylinder could fire.
They would share the same intake stroke.

I remember reading somewhere that it is easier to build an engine with 7or9 cylinders than it is for 7 and smaller.Must be for the reason your stating.The more cyls in a circle would mean the degrees apart from one another would be closer or less.Plus if your making articulating rods and only 1 master rod,the master would be the hardest.The articulating rods would all be the same and would look like a normal rod.After the first one,you could use it as a pattern or like i was thinking just use weedie rods already made up.Im going to look in my WWI encyclpedia and read the descriptions on the early radial engines.I do remember they had a Rotham air pump on the wing strut with the little propeller to pressurize the fuel tank.There was also a hand pump on the right side of cockpit in case the outboard pump failed.Oops,where getting of topic,maybe we nead a thread started (scratch built multi-cylinder),we"ll see if it gets as long as the echo thread.

Well, here's one way to do it.

I can't think of any practical way to make a radial two stroke, unless you cheated like the pictures shown of a four stroke radial...

AV8TOR

I love this engine. I wish it had audio to go with it.

I was actually thinking about a single crankcase set up like the BME twins we made.

How many degrees apart could those cylinders fire with out adversely affecting the second cylinder's performance?

This is a 5 cylinder engine made up of OS 70 engines.
And it turns a 22x10, same as my G-62.

I wonder how fast it turns it?

I was also thinking about that also.im on the lookout for 3- 22cc echos,short blocks.Ill have to give farley9n a call.