MR Flyer57

Every time your on I get more useful info,,, thanks again
MR Flyer57

MR Flyer57

Hey again Tim,
I will ask you but if Dickybird or anyone else knows this please jump in. How do you separate the piston from the rod without damage to the components?

I was reading about the piston being shaved to make it lite and I didn't think that could be done with the unit in one piece.
Am I missing something again?
Marshall

DICKEYBIRD

Actually Tim, you grind a little off the top of the crankcase where the cylinder seats, ie: you're lowering the entire cylinder, not just the lower edge of the exhaust port. This of course requires more plug gaskets to keep the compression the same. There may be Cox hotrodders that grind & lower just the exhaust port but I've never tried it myself.

Mr Flyer, you can't separate the piston from the rod and put it back together. I hold the rod off to one side with a piece of 3/32" music wire that fits down into a brass tube positioned in the table of my "lathe." This gives just enough room to grind some metal off with a 1/8" carbide "pea" cutter in my Dremel. I'll try to get some pictures together to make this clearer.

Again, I strongly caution you against trying this if you don't have a bunch of old parts to learn on. I'd hate to see you guys ruin your favorite engines. We're talking somewhat smoother running and maybe a few more rpm....not a huge speed secret at all. Not that I'm special or anything, but it does require some finesse and practice to do it without ruining the piston. I also use a slip on magnifier to get REALLY close to the job so I can REALLY see it clearly.

Good luck!

prole

My Feedback: (3)

DB,

Oh, I thought that you were taking the material off the cylinder, not the cranck case. I wasn't saying to open the exhasut ports more, I was saying that if you take a little off the bottom of the cylinder you are lowering the entire cylinder, which in effect lowers the bottom edge of the exhasut port in relation to the piston.

Since the piston and rod are the constant, the cylinder threading deeper into the crankcase because of the material removed from the bottom makes the whole cylinder/glowhead unit drop down.

We are saying the same thing, only you are taking off material from the crank case, I am taking material off the bottom of the cylinder.

Mentioning the exhasut port was just to show where the difference would be measured. As you gaskets would have to be substitued on the top for what you are removing from the bottom.

This comes from combatalbert, he was heping me with finding the cylinder and giving me tips as well. He is a C/L combat dude and from what I understand, is pretty bad a#s at hot rodding these little engines.

...but he thought what I was doing was a waste of time because it didn't get me more RPM's

at this point I am more stoked about the low throttle than the screaming hi-end.

MR Flyer57

More good stuff,
thanks again guys
Marshall

ajcoholic

My Feedback: (10)

This is all very very interesting to me guys - Andy Woitowitz wrote an article about two years ago for FM in which he tried some different throttling options on various engines, and basically came to the conclusion that engines like the VA, norvel, etc have much better throttling than the Cox Td series. Now I am very much interested to see if the Cox TD can indeed be made to idle as low as the others and most important transition back to full rpm after extended idle, and do it neatly.

I have a spot in my heart for Cox engines, allways have and allways will!

I bought a few more (3 actually) Tarno carbs while in Toledo. I was flying my simple 400 with a home made exhaust and a tarno on my td 051 a few years ago with OK results but now I think combining a throttle sleeve with the carb may be something else to try?

AJC

prole

My Feedback: (3)

Hey Andrew,

What exactly are the Tarno Carbs? and where can I get one and/or read some info about them?

Are they the ones that are on the Cox RC .05? And how about those, a TD with a real muffler and a fully functional carb? Do they work really well and that is why they are so expensive? Or do they not work well so not many were made so they are just rare and that is why they are so expensive?

they never really come up around here...

you know, why shouldn't a TD work well with a muffler and a carb? what is the difference? Why is it so hard to throttle the TD's?


????

wild fred

My Feedback: (3)

prole; tarno's look a little like the 05 carbs, but were done by a guy from canada named tarnowfski, I beleive. had one years ago, never really got a low idle, but I think a.j. on right track w/ coupled exhaust throttle; I think back pressure would help a lot on them. tarno's come up from time to time, you just gotta know what to look for! they came in a clear plastic case like fishhooks used to come in if I remember right.

av8rsodt

My Feedback: (23)

Ajcoholic -

I have been using throttle sleeved TD's for a quite awhile and still am amazed at how low they can idle. According to my flying buddies it is even lower than many Norvels they have seen.

The modifications, primarily the venturi and type of cylinder type, I am sure help even more.

Most of the planes I have been flying also only use 10% Cool Power - the main driver I was taught to use this fuel was for saving the engine (very high rpm's not needed for 3 channel scale models vs the scream'n pylon racers).

These throttled TD's also start very easy - very rarely need to use a starter, and in most cases the carb either needs cleaned out (3 small holes in the venturi) or a new glow head.

Av8rsodt

av8rsodt

My Feedback: (23)

Dickeybird -

Have you had many problems with tank location?

In the past, I have had problems with fuel draw. The engine would run great level, but when the plane would climb it would sag and die.

I am hoping the venturi mod will help the situation.

Brian

ajcoholic

My Feedback: (10)

Tim,
The 1/2A Tarno carb was indeed made by a fellow Canadian back inthe 1970's. Its a mini air bleed carb designed to thread right into the TD housing. I have 4 of them now and two are on my VA's. They NEED to be run with some kind of exhaust restriction, either a muffler or something like I made up, a collector. I will attach a piccy of my simple 400 with the VA/tarno on it...

I also flew a small seaplane (Ken Willard design) back in the early 90's with a throttle sleeve'd TD 051 and I was amazed at how low it went on idle and would just not quit. If your mods are making that even better, well thats pretty amazing!

Dickeybird I know Cox made some pistons lighter for the Venon and Killer Bee series, but I never even thought of grinding my own.... Cool!

AJC

DICKEYBIRD

Take a look at the picture....this works well. I make tanks from Fuji film canisters and contact cement them in a block of foam before shoving them in the tank compartment. Set it so it's even with the needle valve. Works every time.

Yes, the smaller venturi bore AND the cylinder without S.P.I. both help make the engine far less attitude sensitive,

DICKEYBIRD

I took a few pix over the weekend to clarify some of the engine questions. You know the old saying: "One picture is worth a thousand words."

Let me preface this by saying that these are my own general observations and you'll find Cox engines through the years can have many different combinations of porting configurations. The 1st pic is of a standard dual bypass port cyl. You see them on most Black Widows, (I think) Babe Bees, a lot of "product" engines and Medallions. Usually, Black Widows have S.P.I.; the others may or may not!

DICKEYBIRD

This pic shows S.P.I (Sub Piston Induction or Free Porting) ie: space under piston skirt at TDC. The one shown has about .012" You have to have the slop adjusted out of the piston/rod socket to accurately measure this. Up to a point, the more S.P.I., the higher the rpm potential. You need less prop load to take advantage of this effect and S.P.I. usually screws up exhaust throttle sleeve equipped engines.

DICKEYBIRD

This shows (what I call) the "Twin Slit" exhaust ports. It's seen on most all modern era product engines, Babe Bees and others.

DICKEYBIRD

A "Twin Slit" cyl. with the center bridge ground off. I think this adds a little top end but is difficult to do with hand tools.

DICKEYBIRD

This pic is of a dual bypass cyl. with one extra small milled port at the side of each bypass. This config. is seen on the later TD's, Killer Bees, Venoms and Sure Starts. The TD's, Venoms, and (I think) Killer Bees all have S.P.I. The Sure Starts and most "product" engines I've come across don't have S.P.I. The non S.P.I. cyl. with the extra small bypasses is what I've come to like the most for my exhaust sleeve throttle equipped TD's for general sport use, ie: good idle and transition plus good top end. The cyls. without the 1 extra small bypass and without S.P.I. idle and throttle great but the top end may be reduced somewhat. I say MAY because there are some cyls. that defy logic and seem to be possessed by black magic even though they don't have all the right traits. On the other side of that coin, there are some that won't do right for no measurable reason!

DICKEYBIRD

This is an older TD cyl. with 2 extra ports milled in on either side of the bypass. These (I think) all have S.P.I. They work best for high speed, pressurized fuel system racing use.

DICKEYBIRD

This shows a "bushed down" (reduced ID) venturi. The darker bands are the layers of JB Weld between the 2 pieces of alum. tubing added. I use a final bore ID of 3/32".

DICKEYBIRD

This is the setup I chuck into my "poor man's lathe" to lighten pistons. A slit piece of brass tube protects the piston surface.

DICKEYBIRD

Chucked and ready to grind with a Dremel and small carbide cutter. Don't chuck too tightly, just enough to keep things from moving around. Note the 3/32" music wire slipped through the rod down into a short length of brass tubing glued into the table top. This keeps the rod out of the way when grinding. I use a magnifier and a strong light so I can see well enough inside to prevent grinding on the ball socket boss. Man, I'm giving away all the "Collierville Cadre's" secrets! Ya'll need to fax me $20 bill!

Gotta take wifey for tests tomorrow so I won't be online 'til Tuesday. Happy Easter ya'll.

ajcoholic

My Feedback: (10)

Dickeybird,
The babe bee uses a #2 single bypass cylinder as did the golden bee.

The Medallian #3 cylinder does have an extra groove and the TD's two of these along side the main large bypass groove. I know there was a good pic of all these in one of my books I can dig it up if needed...

Andrew

MR Flyer57

Thanks for the great info guys!!
If you run across those pictures, please send them long ajcoholic.
This is the information you can't get anywhere, if I weren't so darn cheep I just might have sent ya that $20 Dickybird,,,
Dickybird,,, I read the post with only one eye,,, so I'm only into you for $10.

MR Flyer57

MR Flyer57

Well I got the bug and started a Dickybird engine. And now I am really confused! I have a lot of strange stuff. It seems that cox had a passion for changing things. This may be good but it throws me off.

The first problem, and question for ya is: I have many cylinders that did not come with an exhaust sleeve. It seems that no sleeve will fit them. Do you have a picture of a sleeve that will fit a standard cylinder?
Maybe you can show me a close up of a sleeve and cylinder that is different than the ones that I have here.

These sleeves are not the same inside diameter, two will fit the same one and one is just a little bigger. But they are all to small to fit a normal cylinder.

MR Flyer57

I put this one on the cylinder and it has such a small hole that I doubt that it would work. Do you carve out the holes in the sleeves, or does yours look like this when you use them?