Request For Tee Dee Help
02-02-2016, 05:39 PM
#1
Request For Tee Dee Help
I have a Tee Dee .049 with Kustom Kraftsmanship needle, crankcase pressure backplate, and cylinder shims installed in a GLH. When I was flying it last summer, I was unable to get a steady needle setting. Whenever I thought I had a good needle setting, holding the nose up just a few degrees prior to launch would cause the engine to slow down (leaning out?); when returned to level, engine would resume "normal" operation. Same happens while flying, hence climbing was very difficult and engine would usually quit at about 1/2 tank.
The airplane is using a 2 oz. hard tank, 30% heli fuel w/ some castor added, and a Cox 5X4 nylon. I'm pretty sure the tank and plumbing are sound because I set up two different Tee Dees for a friend w/o pressure and they both pulled the airplane (used as a testbed) along much better thru an entire tankful than what I can achieve with my modded engine. I have a piece of fuel tubing over the union of the needle and plastic fitting because I'm leery of air leaks. Plastic carb body was replaced because it cracked causing a previous problem. I checked the pressure backplate fitting for daylight when sighting thru hole when I tore down engine to clean it up. New plug - same problem.
Hoping someone recognizes symptom described and can suggest remedy...
The airplane is using a 2 oz. hard tank, 30% heli fuel w/ some castor added, and a Cox 5X4 nylon. I'm pretty sure the tank and plumbing are sound because I set up two different Tee Dees for a friend w/o pressure and they both pulled the airplane (used as a testbed) along much better thru an entire tankful than what I can achieve with my modded engine. I have a piece of fuel tubing over the union of the needle and plastic fitting because I'm leery of air leaks. Plastic carb body was replaced because it cracked causing a previous problem. I checked the pressure backplate fitting for daylight when sighting thru hole when I tore down engine to clean it up. New plug - same problem.
Hoping someone recognizes symptom described and can suggest remedy...
02-02-2016, 07:02 PM
#2
Seems that pressure wasn't enough I have the same back plate the hole is very small.
If I recall I was able to pass #30 gage motor winding wire through.
Things to check
Tank looking horizontally to the NV is level to or splitting above and bellow the NV.
Fuel line is true 1/2A size
Fuel line on the needle to avoid air leaks / loss of pressure
Prop to big not enough rpm for good crank case pressure.
All lines as short as possible
Fuel tank volume is too big at 2oz perhaps 1oz tank should yield 3.5mins flights at full throttle.
If I recall I was able to pass #30 gage motor winding wire through.
Things to check
Tank looking horizontally to the NV is level to or splitting above and bellow the NV.
Fuel line is true 1/2A size
Fuel line on the needle to avoid air leaks / loss of pressure
Prop to big not enough rpm for good crank case pressure.
All lines as short as possible
Fuel tank volume is too big at 2oz perhaps 1oz tank should yield 3.5mins flights at full throttle.
02-02-2016, 09:04 PM
#3
More considerations...if all else checks out OK.......
Engines that are overly sensitive to the usual changes in head pressure as a tank empties in flight aren't pumping efficiently. There just doesn't seem to be a needle setting that will keep them running for the entire tank.
In other words, crankcase pressure can be leaking out the front / back / top of the case or the piston isn't pumping up enough air to begin with.
Changing the plug is of course the easiest thing to do first. Sometimes the old copper head shim is leaking.
In general it is good to have a gun cleaning kit with a plastic bristle bore brush and Hoppes solvent to keep these Cox engines devarnished.
Trouble is, a little varnish might be a beneficial "bandaid" on a worn engine.!
You can use a cheap magnifying glass and a flashlight to inspect the P/L surfaces to see some pretty revealing flaws sometimes. You can also pressure test 2 cycle engines under water while looking for air bubbles leaking out of nooks and crannies. I've never tried this with a Cox engine, but with clay, duct tape, a drinking straw, you can give it a try.
The replacement P/L set I got recently from Cox International was a good one and reasonably priced if you determine it's time for a new set..
Engines that are overly sensitive to the usual changes in head pressure as a tank empties in flight aren't pumping efficiently. There just doesn't seem to be a needle setting that will keep them running for the entire tank.
In other words, crankcase pressure can be leaking out the front / back / top of the case or the piston isn't pumping up enough air to begin with.
Changing the plug is of course the easiest thing to do first. Sometimes the old copper head shim is leaking.
In general it is good to have a gun cleaning kit with a plastic bristle bore brush and Hoppes solvent to keep these Cox engines devarnished.
Trouble is, a little varnish might be a beneficial "bandaid" on a worn engine.!
You can use a cheap magnifying glass and a flashlight to inspect the P/L surfaces to see some pretty revealing flaws sometimes. You can also pressure test 2 cycle engines under water while looking for air bubbles leaking out of nooks and crannies. I've never tried this with a Cox engine, but with clay, duct tape, a drinking straw, you can give it a try.
The replacement P/L set I got recently from Cox International was a good one and reasonably priced if you determine it's time for a new set..
02-03-2016, 07:11 AM
#4
Maybe the carb was opened up which makes it more sensitive. 1/8" is about the max that I found to work. Maybe the tank is back too far. Maybe the clunk line is leaky, detached or pushed forward from a hard landing. Air leaks are magnified a lot when using pressure. Maybe it is just too lean to start with as a normal test is to raise the nose to set the needle. It should work well on suction if the carb is not drilled out. Try it without the backplate pressure, and plug up the nipple.That is about all I can think of that has not been mentioned.
Last edited by aspeed; 02-03-2016 at 07:14 AM.
02-03-2016, 10:43 AM
#5
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Set the needle at peak with the nose
pointed up. The prop will unload a
bit when it gets moving so it needs to
be a little rich.
You could try a 6x3 prop. It will unload
a little less than a 5x4, though you won't
have the top speed GLH implies.
If you aren't using a muffler, you can take out
the shims. They probably aren't causing the
problem, but they will decrease the power
when used without a muffler. Running
without them will give back some of the
power you lose by running a bit richer.
Finally, you can block the crankcase pressure.
I always found pressure to be finicky.
Running stock is the most reliable, though
not the most powerful. For competition, go
for all the mods on multiple engines to find
one that is great. For fun, stick to reliable
stock setup.
Jenny
pointed up. The prop will unload a
bit when it gets moving so it needs to
be a little rich.
You could try a 6x3 prop. It will unload
a little less than a 5x4, though you won't
have the top speed GLH implies.
If you aren't using a muffler, you can take out
the shims. They probably aren't causing the
problem, but they will decrease the power
when used without a muffler. Running
without them will give back some of the
power you lose by running a bit richer.
Finally, you can block the crankcase pressure.
I always found pressure to be finicky.
Running stock is the most reliable, though
not the most powerful. For competition, go
for all the mods on multiple engines to find
one that is great. For fun, stick to reliable
stock setup.
Jenny
02-03-2016, 02:33 PM
#6
I really appreciate all the help. Other useful/useless info: This engine/airframe setup once did run well. I forgot to mention that I did in fact open up the carb (venturi) back during my racing days some 25 years ago and perhaps exceeded specs (part of the problem?) by the time I got done filing and polishing out drill marks. The 2 oz. tank has fixed pick-up for inverted shut-downs during races. I substituted a C/L remnant piston that is not OE because I trashed the original when I went to reset the rod. I lapped P/L w/ compound and this engine once turned at best, a reliable 24K with cut down Cox grey and MA props of various sizes. With a thinned down wing, it was better than some stock GLH's but couldn't hold a candle to Undertakers and Taperwings at the time and I think those super, competitive guys were turning in the upper 20K's. The cylinder shims had something to do with SPI (sub port induction) and I either forgot or never really understood concepts here...
I have a new Cox Int'l P/L set intended for this engine so maybe now is the time to install. Since I don't race anymore, perhaps I should in fact go to a stock set-up because all I'm looking for is reliability for nostalgic sport fun. Though, still wondering if there is any blockage in pressure fitting or high pressure leakage based on all the feedback.
I have a new Cox Int'l P/L set intended for this engine so maybe now is the time to install. Since I don't race anymore, perhaps I should in fact go to a stock set-up because all I'm looking for is reliability for nostalgic sport fun. Though, still wondering if there is any blockage in pressure fitting or high pressure leakage based on all the feedback.
Last edited by H5606; 02-03-2016 at 03:01 PM.
02-03-2016, 06:19 PM
#7
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The enlarged venture will cause the engine
to not suck as hard at lower rpms, so the
engine will be more sensitive to fuel level
being lower when the nose is up. It should
be easy to get a stock venturi to replace
your enlarged one. A smaller propeller will
also get the rpms up where the large venturi
wants them.
You should try to get a new "old stock" piston/
cylinder set at a flea market. They are much
better than the later production ones. There
is a flea market coming up in Westminister
on Feb 13, where you might find one. The
chances are much better on finding good old
parts at the Lebanon flea market in March.
The sub piston induction allows fresh air
to enter under the piston at TDC. This assures
that no vacuum remains from the engine
sucking through the carb during the upstroke.
This in turn allows the maximum transfer
when the piston reaches bottom.
The shims raise the cylinder so there is no
gap under the piston at TDC. It is important
with a muffler because it would let in exhaust
with very little oxygen instead of fresh air.
Since the cylinder is raised, there is more
combustion chamber volume, and thus lower
compression. To compensate, shaved heads
are used to get back the normal compression.
There is still power loss with the muffler, but it
is less than using a muffler without the shims
and shaved head.
Jenny
ps. I think the old stock in blister packs is the
best. They probably have an address as
Corona California. After cox moved they still
made good stuff for a while. I think the new
address was Warner California.
The newer parts came in plastic bags with
red, white design and black printing. Some
are good and some not so good. I can't remember
how to tell the lower quality ones, except that
the dual slit cylinders are all the crummy ones.
It might be that the cylinders that are wide all the
way from the base to the fins are the crummy ones,
and the ones that have a narrow neck are the good ones.
to not suck as hard at lower rpms, so the
engine will be more sensitive to fuel level
being lower when the nose is up. It should
be easy to get a stock venturi to replace
your enlarged one. A smaller propeller will
also get the rpms up where the large venturi
wants them.
You should try to get a new "old stock" piston/
cylinder set at a flea market. They are much
better than the later production ones. There
is a flea market coming up in Westminister
on Feb 13, where you might find one. The
chances are much better on finding good old
parts at the Lebanon flea market in March.
The sub piston induction allows fresh air
to enter under the piston at TDC. This assures
that no vacuum remains from the engine
sucking through the carb during the upstroke.
This in turn allows the maximum transfer
when the piston reaches bottom.
The shims raise the cylinder so there is no
gap under the piston at TDC. It is important
with a muffler because it would let in exhaust
with very little oxygen instead of fresh air.
Since the cylinder is raised, there is more
combustion chamber volume, and thus lower
compression. To compensate, shaved heads
are used to get back the normal compression.
There is still power loss with the muffler, but it
is less than using a muffler without the shims
and shaved head.
Jenny
ps. I think the old stock in blister packs is the
best. They probably have an address as
Corona California. After cox moved they still
made good stuff for a while. I think the new
address was Warner California.
The newer parts came in plastic bags with
red, white design and black printing. Some
are good and some not so good. I can't remember
how to tell the lower quality ones, except that
the dual slit cylinders are all the crummy ones.
It might be that the cylinders that are wide all the
way from the base to the fins are the crummy ones,
and the ones that have a narrow neck are the good ones.
02-04-2016, 08:44 AM
#8
The 5/32" TD venturi mod and backplate pressure is what 100% of the local pylon racers have used for years. The size of the pressure orifice makes no difference except that large pressure taps [like 1/16" or even 3/32"] are more prone to accidental backflow into the engine while starting.
02-04-2016, 09:13 AM
#9
Thanks again for info - I miss-labeled SPI in my previous post. I want to make sure I understand sub-piston induction correctly: you would use cylinder shims to eliminate the gap below the piston skirt to optimize pressurized systems AND/OR when using a muffler? Otherwise for stock config, you want SPI? I'm lazy but it'd probably help for me to just read the instructions that come with the shims and besides, its more fun to ask here...
I have two more untouched Tee Dees and KK parts, so I can rob or swap parts if needed. I plan to go to the Lebanon flea market; I'll try to keep my eyes open, but will primarily be trying to sell stuff.
BTW, I always thought (perhaps incorrectly) that the narrow neck cylinders were necessarily single port style and the thick ones were dual port bypass based on the Cox stuff I have and that Black Widows and Tee Dees used the dual port ones.
I have two more untouched Tee Dees and KK parts, so I can rob or swap parts if needed. I plan to go to the Lebanon flea market; I'll try to keep my eyes open, but will primarily be trying to sell stuff.
BTW, I always thought (perhaps incorrectly) that the narrow neck cylinders were necessarily single port style and the thick ones were dual port bypass based on the Cox stuff I have and that Black Widows and Tee Dees used the dual port ones.
02-04-2016, 09:26 AM
#10
The 5/32" TD venturi mod and backplate pressure is what 100% of the local pylon racers have used for years. The size of the pressure orifice makes no difference except that large pressure taps [like 1/16" or even 3/32"] are more prone to accidental backflow into the engine while starting.
02-04-2016, 12:54 PM
#11
Yes, if you can push air or fuel through the nipple, you are good to go.
SPI works great with pressure delivery. KK used to recommend no more than .010" if I remember correctly. I never paid much attention to it. If you are running small props like a 5 x 3, or 4.2 x 4 you need all the compression you could get, so I'm in favor of setting the liner as low as it will go. A real good engine will spin a 5 x 3 at 24,000. A mediocre engine 22,500..which was hardly enough ooomph to keep the lines tight on a windy day in the combat circle.
These engines will begin to fail soon if you run them above 24,000, so I never felt my approach left anything on the table.
Friction proofing the crankshaft and lightening the inside of the piston is where it is worth to spend time. When the piston is flying up and down 400 times per second, micro grams of weight shaved off the piston has to be a win - win for both performance and longevity.
SPI works great with pressure delivery. KK used to recommend no more than .010" if I remember correctly. I never paid much attention to it. If you are running small props like a 5 x 3, or 4.2 x 4 you need all the compression you could get, so I'm in favor of setting the liner as low as it will go. A real good engine will spin a 5 x 3 at 24,000. A mediocre engine 22,500..which was hardly enough ooomph to keep the lines tight on a windy day in the combat circle.
These engines will begin to fail soon if you run them above 24,000, so I never felt my approach left anything on the table.
Friction proofing the crankshaft and lightening the inside of the piston is where it is worth to spend time. When the piston is flying up and down 400 times per second, micro grams of weight shaved off the piston has to be a win - win for both performance and longevity.
Last edited by combatpigg; 02-04-2016 at 12:59 PM.
02-04-2016, 05:37 PM
#12
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OK. So I got out my old stash of Cox engines and
parts. The good stuff came from Santa Ana California.
The crummy stuff came from Corona California. (Warner
was the name of the road in Santa Ana where they
were located prior to moving to Corona).
The Tee Dee .09 had a neck at the base of the cylinder,
as did the reed valve .049's, but the Tee Dee 049 did not.
The way to tell a good cylinder/piston set is that when
the piston is pushed up into the cylinder, it can come
part way (maybe half) out the top before it gets too
tight. The crummy ones may go farther or all the
way out the top. Occasionally one would not go
out the top at all or just a smidgen out. These could
be mixed an matched to get at least one better
performing engine.
On the earlier engines there were ladies who did
this matching in the factory, so you always got
a good set. After moving to Corona, they stopped
doing this. I believe Kustom Kraftmanship would
buy lots of parts and do this matching, so what
you got from them was still good.
Some time after the Santa Ana days, parts bags
had a square Cox logo and the address on the
back was for Leisure Dynamics in Minnesota.
These parts were questionable, some good,
some crummy. Some had poorly matched
cylinders, some had crankcases assemblies
with the drive plate pressed on crooked, etc.
As far as I know, all the blister packs were
good stuff from Santa Anna, but I'm not
sure about the really REALLY early stuff.
The clear plastic boxed engines were also
really good.
Jenny
parts. The good stuff came from Santa Ana California.
The crummy stuff came from Corona California. (Warner
was the name of the road in Santa Ana where they
were located prior to moving to Corona).
The Tee Dee .09 had a neck at the base of the cylinder,
as did the reed valve .049's, but the Tee Dee 049 did not.
The way to tell a good cylinder/piston set is that when
the piston is pushed up into the cylinder, it can come
part way (maybe half) out the top before it gets too
tight. The crummy ones may go farther or all the
way out the top. Occasionally one would not go
out the top at all or just a smidgen out. These could
be mixed an matched to get at least one better
performing engine.
On the earlier engines there were ladies who did
this matching in the factory, so you always got
a good set. After moving to Corona, they stopped
doing this. I believe Kustom Kraftmanship would
buy lots of parts and do this matching, so what
you got from them was still good.
Some time after the Santa Ana days, parts bags
had a square Cox logo and the address on the
back was for Leisure Dynamics in Minnesota.
These parts were questionable, some good,
some crummy. Some had poorly matched
cylinders, some had crankcases assemblies
with the drive plate pressed on crooked, etc.
As far as I know, all the blister packs were
good stuff from Santa Anna, but I'm not
sure about the really REALLY early stuff.
The clear plastic boxed engines were also
really good.
Jenny
02-04-2016, 07:58 PM
#13
The very narrow cylinders were early. About the 1960s. I bought new ones that were slightly smaller around the port in the early to late 1970s, and the newer ones were solid all the way up, and some had the two slits. I have a few of those but do not know the exact years that they changed, as I bought them used, or they were in boxes with other things. I found they all went about the same pretty much. The single bypass, and twin bypass TD type being the most difference. The crankcases got fatter at about the same times that the cylinders got fatter. I don't believe I have any without the SPI, but think it was likely because of the mufflers. I think shimming the cylinder was only done to make the exhaust ports face forward to get the gasses out. At least with the people I hung around with. I guess it would get a higher power band, and would lose the SPI if it is too high. Then the top step of the liner would need machining to get the compression back.
02-05-2016, 09:30 AM
#14
While driving into work this morning, my carpool-mate was talking something about taxes to me and I was daydreaming about Cox engines. Caution: the following is personal opinionated info based only on observation, speculation, and poor memory... I may at one time have been concerned over the piston hitting the glowhead at TDC and perhaps this had something to do with using the cyl shims (not head shims [for clarification]). One of the late C/L toys from my youth - I remember as having a metal screen spot welded to the cylinder around the exhaust ports like a spark arrestor? I think this was done to try to prevent fires because liability issues were becoming more prominent in the culture at this time (mid-70's). If you've ever had an alcohol fire on an airplane, they are very difficult to see. Funny things start happening before you realize what's going on. I think the narrow exhaust slits in cylinders showed up shortly thereafter to try to perform the same function(?)
CP, forgive me if a really dumb question but do you separate the conrod from the piston to facilitate shaving it and what is "friction proofing"?
CP, forgive me if a really dumb question but do you separate the conrod from the piston to facilitate shaving it and what is "friction proofing"?
Last edited by H5606; 02-05-2016 at 03:58 PM.
02-05-2016, 08:41 PM
#15
H506, take some wire and secure the rod off to the side. You want good, strong light to see in there.
Besides that, the back side of a #11 xacto blade shaves the leadloy metal nicely. I don't recall the turning speed...just feel it out for what works for you. Make the walls as thin as a playing card if you are having a good time at it.
The only caveat ..two possible negatives is if you make the piston too light then the engine will obviously let you know and you might have to grind a divot out of the crank's counterweight. I've never had to do this with a TD.
The other caution is the piston is easier to make out of round while doing a rod reset.
You'll want to make a nice little holding fixture out of hardwood or aluminum to hold the piston in the jaws of a lathe chuck.
If you ever get a chance to look at a "real" Killer Bee .049 they have a thin wall piston, but not quite as thin as you can go.
Besides that, the back side of a #11 xacto blade shaves the leadloy metal nicely. I don't recall the turning speed...just feel it out for what works for you. Make the walls as thin as a playing card if you are having a good time at it.
The only caveat ..two possible negatives is if you make the piston too light then the engine will obviously let you know and you might have to grind a divot out of the crank's counterweight. I've never had to do this with a TD.
The other caution is the piston is easier to make out of round while doing a rod reset.
You'll want to make a nice little holding fixture out of hardwood or aluminum to hold the piston in the jaws of a lathe chuck.
If you ever get a chance to look at a "real" Killer Bee .049 they have a thin wall piston, but not quite as thin as you can go.
02-06-2016, 08:28 PM
#16
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Wondering if you have had any luck yet. I love running them on pressure with a hard tank. I have only used a one ounce tank, though. I have had my best luck letting the engine run long enough to warm up, tilt the nose up about 60 degrees then lean it out to a slightly rich setting. The pressure keeps the fuel flow pretty steady. My tee dees (.049 and .051) have an aluminum carb body, bored venturi, hole in back plate pressure tap drilled with a #70 bit and Galbreath head with Nelson plug. I run Sig Champion 25%. I like to use an APC 5.7x3 that I cut down to a 5x3. I don't know what kind of RPM I get in the air. But, it is enough to have broken the crank pin. Good luck.
02-08-2016, 04:37 AM
#17
Haven't tried anything yet as no flying allowed in this area for time being but wondering if source for aluminum carb body exists. I see a webpage for Halfa Works; are they still active?
02-08-2016, 12:26 PM
#18
http://www.ebay.ca/itm/Cox-020-Tee-D...item564905cb4e
The only aluminum carb bodies left are for the TD .020 and when they go that may be it as no one is making
aluminum carb bodies currently. The guy that use to do it has stopped over a year plus ago -medical issues was told.
The guy from HalfA Works has been selling off his parts and engines on Ebay. I would call him soon as
you can. 704.701.3436 / [email protected] / note he wasnt making them only buying from
the following guy:
The guy that use to do it has stopped over a year plus ago I bird dogged his offerings each time on Ebay and manged
to snag .010 / .020 / .049 / .09/ .15 aluminum carb bodies enough to out fit around 30 engines.
Aeromodel Retrofitter 8333 Halstead Rd. Blossvale, N.Y. 13308. Mike is the name - he sells on ebay last
time was a few years ago. - messaged Mike on ebay over a year ago for a pre order he said he wouldn't
be making any for awhile. I would buy the .020 while you still can not many left after that it will be hard
to source by the looks of things.
Items for sale from ridenfligh - 0
ridenfligh (1153
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| Add to my favorite sellers
The only aluminum carb bodies left are for the TD .020 and when they go that may be it as no one is making
aluminum carb bodies currently. The guy that use to do it has stopped over a year plus ago -medical issues was told.
The guy from HalfA Works has been selling off his parts and engines on Ebay. I would call him soon as
you can. 704.701.3436 / [email protected] / note he wasnt making them only buying from
the following guy:
The guy that use to do it has stopped over a year plus ago I bird dogged his offerings each time on Ebay and manged
to snag .010 / .020 / .049 / .09/ .15 aluminum carb bodies enough to out fit around 30 engines.
Aeromodel Retrofitter 8333 Halstead Rd. Blossvale, N.Y. 13308. Mike is the name - he sells on ebay last
time was a few years ago. - messaged Mike on ebay over a year ago for a pre order he said he wouldn't
be making any for awhile. I would buy the .020 while you still can not many left after that it will be hard
to source by the looks of things.
Items for sale from ridenfligh - 0
ridenfligh (1153
) | Add to my favorite sellers
Last edited by Pond Skipper; 02-08-2016 at 12:28 PM.
02-13-2016, 07:23 PM
#19
Hi H5606,
With my limited experience running TD .049's with my friends, we found it was simpler to leave the pressure tap sealed and run pen bladders for fuel tanks. Even if you had a slight "leaker" , the engine would run consistently and make good power. You had to be careful starting the engine with a bladder or you could easily flood it or hydraulic lock it. I have an old collection of TD cranks with the crank pins missing from those fun times. Anybody have or know of a source of TD .049/.051 crankshafts?
Ah the good ol' days of half A racing !
Carlos G
With my limited experience running TD .049's with my friends, we found it was simpler to leave the pressure tap sealed and run pen bladders for fuel tanks. Even if you had a slight "leaker" , the engine would run consistently and make good power. You had to be careful starting the engine with a bladder or you could easily flood it or hydraulic lock it. I have an old collection of TD cranks with the crank pins missing from those fun times. Anybody have or know of a source of TD .049/.051 crankshafts?
Ah the good ol' days of half A racing !
Carlos G
02-16-2016, 11:42 AM
#20
TeeDee crank shafts in both LH and RH are usually on e-bay----- the hard part to find anymore is the main crank case---- second hardest to find are new .051 Piston cylinder sets...almost all other bits are found from several sources...MECOA, Cox Intentional, Ex-model engines, and several e-bay sellers
I have enough new parts from Cox international and e-bay to build about 5 new TeeDees or Medallions....I think all were Buy It Now sales and no auction non sense
IN fact I bought several of the so call high performance TeeDee crank shafts and my testing did not show them to be any better than the stock crank shaft
I use a lot of TeeDees on combat plane for personal fun fly and training saving the more expensive FAST engines for competition, That and the fact that a TeeDee in the dirt is no big deal while a ball Bering .049 engine must be well cleaned before re-starting
In my opinion the ONLY reliable way to run a TeeDee with opened up venturi is on bladder pressure
I have several with the factory port opened Or a back case cover port into hard tanks....and they are finicky, usually requiring a starter motor
But the bladder fed engines fire off prime by finger just fine and scream to life once the pinched fuel line is opened
I have enough new parts from Cox international and e-bay to build about 5 new TeeDees or Medallions....I think all were Buy It Now sales and no auction non sense
IN fact I bought several of the so call high performance TeeDee crank shafts and my testing did not show them to be any better than the stock crank shaft
I use a lot of TeeDees on combat plane for personal fun fly and training saving the more expensive FAST engines for competition, That and the fact that a TeeDee in the dirt is no big deal while a ball Bering .049 engine must be well cleaned before re-starting
In my opinion the ONLY reliable way to run a TeeDee with opened up venturi is on bladder pressure
I have several with the factory port opened Or a back case cover port into hard tanks....and they are finicky, usually requiring a starter motor
But the bladder fed engines fire off prime by finger just fine and scream to life once the pinched fuel line is opened
02-16-2016, 01:56 PM
#21
I worked at Cox in customer service during 1980 doing engine and radio repairs. Dale Kirn, Roger Theobold and Kit McNorgan trained us on how to service the engines. We had service parts dating back to the 1950s and often built older "Hopper" series engines using new old stock parts left over from the original factory that was on Pointsetta St., in Santa Ana. We also had three test booths we used to run-in and test customers engines. In our spare time we would hand fit and build engines as replacements for customers, mainly because we had better old stock parts in customer service than the ones being produced in the factory that reflected the cost cutting measures implemented by Leisure Dynamics management. In this way, we were assured of the customer getting a good engine because it was hand bui lt and test run before they recieved it.
Some TD tips: Stock venturi required for suction (non-bladder set-up) We used a Uni-flow tank when using backplate pressure, basically the vent (line to the pressure tap) goes to the bottom or the tank. Best performance is with a bladder. Shims are to "synch" the exhaust ports fore and aft so the transfers line up with the rotating crank, good for about 750 RPM. After shimming, check your deck height, you may need to remove a head gasket or two. If running high nitro, you need less compression, or TDs become very hard to needle consistantly and overheat. We added extra head gaskets when using 25% or more nitro.
The cylinders you see with two exhaust slits were done that way to save a machining step. The slits are cut first, then they are cut free in the next step to form the rectangular port. Under Leisure Dynamics, they eliminated cutting out the full port and left it with the two slits because it was not only cheaper, but also served to reduce problems with accidental fires. Most of the later Cox cylinders and pistons, even ones made at Cox Santa Ana (Warner St.) lack any taper, and althought they run fine and break in quickly, they wear out quickly. During 1979-80, under Dale Kirns direction, the tapers were put back on the TD .049 and a short run of about 800 engines were hand fit and assembled. These were some of the best TDs ever made by Cox and built by Kit McNorgan. The early thin wall cylinders are not as strong, and due the way they are tapered and fit, can take a long break-in. Despite what people have done, it is best to never swap pistons, epecially used ones into a used Cox cylinder. If you have a new piston, that is your best bet. The cylinder number indicates the port configuration on the .049 as follows: 1 is dual bypass, 2 is single bypass, 4 is TD. other numbers are for the cars and Medallion series.
Some TD tips: Stock venturi required for suction (non-bladder set-up) We used a Uni-flow tank when using backplate pressure, basically the vent (line to the pressure tap) goes to the bottom or the tank. Best performance is with a bladder. Shims are to "synch" the exhaust ports fore and aft so the transfers line up with the rotating crank, good for about 750 RPM. After shimming, check your deck height, you may need to remove a head gasket or two. If running high nitro, you need less compression, or TDs become very hard to needle consistantly and overheat. We added extra head gaskets when using 25% or more nitro.
The cylinders you see with two exhaust slits were done that way to save a machining step. The slits are cut first, then they are cut free in the next step to form the rectangular port. Under Leisure Dynamics, they eliminated cutting out the full port and left it with the two slits because it was not only cheaper, but also served to reduce problems with accidental fires. Most of the later Cox cylinders and pistons, even ones made at Cox Santa Ana (Warner St.) lack any taper, and althought they run fine and break in quickly, they wear out quickly. During 1979-80, under Dale Kirns direction, the tapers were put back on the TD .049 and a short run of about 800 engines were hand fit and assembled. These were some of the best TDs ever made by Cox and built by Kit McNorgan. The early thin wall cylinders are not as strong, and due the way they are tapered and fit, can take a long break-in. Despite what people have done, it is best to never swap pistons, epecially used ones into a used Cox cylinder. If you have a new piston, that is your best bet. The cylinder number indicates the port configuration on the .049 as follows: 1 is dual bypass, 2 is single bypass, 4 is TD. other numbers are for the cars and Medallion series.
Last edited by jaymen; 02-16-2016 at 02:21 PM.
02-18-2016, 10:03 AM
#22
Appreciate the interesting and informative material from all... I performed a search for some thread - I could have sworn Bernie at Cox Int'l announcing Tee Dees soon being available again going back a year or so but a cursory search of RCU didn't show any results. Only found some thread requiring $150K in capital to possibly get started producing some.
03-19-2016, 04:03 PM
#23
I can fly again but so far have not...
I pulled the KK pressure back-plate off and held it up to the light and it looks clear to me. Just to confirm, passed a toothbrush bristle through the crankcase side until I could see it come out the end of the nipple. Just now tried blowing air into supply line of tank and pinching off while sealing pressure line and counted to 30 - could hear air rush out when released. Not saying the tank's good, just what I've observed so far...
I went so far as to create a crude insert by turning down a piece of 1/8" ID aluminum tubing for a tight fit in the venturi and followed through with drill for the three fuel delivery holes. The venturi now has a step because of this mod. I don't know what's changed so I may be going nowhere here but I'll try it. Edit: Actually, from memory, something has changed: I am using stock rubber ducky 5X4 props vs cut down MA and Cox comp props and 30% heli Nitro vs 25%.
Is it possible I opened it up way, way, way too much? A 5/32" bit used to pass through with slop; an 11/64" bit was no-go. Now, with the insert, an 1/8" bit passes through with slop; a 9/64" bit does not.
Hate to ruin a new glowhead with a lean run but will give it a try.
I pulled the KK pressure back-plate off and held it up to the light and it looks clear to me. Just to confirm, passed a toothbrush bristle through the crankcase side until I could see it come out the end of the nipple. Just now tried blowing air into supply line of tank and pinching off while sealing pressure line and counted to 30 - could hear air rush out when released. Not saying the tank's good, just what I've observed so far...
I went so far as to create a crude insert by turning down a piece of 1/8" ID aluminum tubing for a tight fit in the venturi and followed through with drill for the three fuel delivery holes. The venturi now has a step because of this mod. I don't know what's changed so I may be going nowhere here but I'll try it. Edit: Actually, from memory, something has changed: I am using stock rubber ducky 5X4 props vs cut down MA and Cox comp props and 30% heli Nitro vs 25%.
Is it possible I opened it up way, way, way too much? A 5/32" bit used to pass through with slop; an 11/64" bit was no-go. Now, with the insert, an 1/8" bit passes through with slop; a 9/64" bit does not.
Hate to ruin a new glowhead with a lean run but will give it a try.
Last edited by H5606; 03-19-2016 at 04:23 PM.
03-20-2016, 11:59 AM
#24
It ought to run fine with a 1/8" venturi.
I've got a Super Tiger .35 Stunt engine that uses a 1/8" venturi...[.just to illustrate a point about how much power a 1/8" orifice can support.]
5/32"+ is a big jump in total area...it might even match the hole size that passes through the crank, which doesn't give much of a pressure drop at the spray bar.
The smaller [1/8"] orifice will decrease the chances of having a lean run and it ought to make the engine less sensitive to fuel level in the tank.
I've got a Super Tiger .35 Stunt engine that uses a 1/8" venturi...[.just to illustrate a point about how much power a 1/8" orifice can support.]
5/32"+ is a big jump in total area...it might even match the hole size that passes through the crank, which doesn't give much of a pressure drop at the spray bar.
The smaller [1/8"] orifice will decrease the chances of having a lean run and it ought to make the engine less sensitive to fuel level in the tank.
03-21-2016, 12:56 PM
#25
I have one or two TeeDee that I went TOO far with the ventrui size....they will only run on bladder
crank case off the front or off the back plate has ALWAYS been a problem for me to needle even with Texas Timers fine thread...but pressure bladder ALWAYS works
I run ONLY Galbreath heads and Nelson Plugs...
I ONLY use red cap or Texas Time Tubing bladder
I can start and run any TeeDee with this set up reliably
I have never got a good full tank run from a crank pressure set up no matter what venturi diameter I tried
I NEVER found cylinder shims to make any better RPM ( trying to align exhaust ports)
The only reason in my opinion to use cylinder shims would be to eliminate SPI of a muffler....... I do nor use mufflers and I have spent hours trying to get exhaust ports aligned to no apparent increase in RPM
crank case off the front or off the back plate has ALWAYS been a problem for me to needle even with Texas Timers fine thread...but pressure bladder ALWAYS works
I run ONLY Galbreath heads and Nelson Plugs...
I ONLY use red cap or Texas Time Tubing bladder
I can start and run any TeeDee with this set up reliably
I have never got a good full tank run from a crank pressure set up no matter what venturi diameter I tried
I NEVER found cylinder shims to make any better RPM ( trying to align exhaust ports)
The only reason in my opinion to use cylinder shims would be to eliminate SPI of a muffler....... I do nor use mufflers and I have spent hours trying to get exhaust ports aligned to no apparent increase in RPM