Cox Tee Dee 049 High Performance Cylinders
#26
RE: Cox Tee Dee 049 High Performance Cylinders
ORIGINAL: GeorgeG97322
I think Bernie and his support group have the metalurgy better accounted for now.
I think Bernie and his support group have the metalurgy better accounted for now.
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RE: Cox Tee Dee 049 High Performance Cylinders
Back from holidays
I have read the thread and agree that the desscription of the cylinderis ambiguous.
I have therefore amended the listing details to more clearly reflect the product description:
http://coxengines.ca/product.php?pro...&cat=13&page=1
Bernie
I have read the thread and agree that the desscription of the cylinderis ambiguous.
I have therefore amended the listing details to more clearly reflect the product description:
http://coxengines.ca/product.php?pro...&cat=13&page=1
Bernie
#28
RE: Cox Tee Dee 049 High Performance Cylinders
Thank you for clarifying the text.
It would be good if you could update the image too so that it shows the actual product fort sale, rather than the classic #4 TD cylinder.
It would be good if you could update the image too so that it shows the actual product fort sale, rather than the classic #4 TD cylinder.
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RE: Cox Tee Dee 049 High Performance Cylinders
Wow, you have good eyes lol.
As I did not think there was a visible difference from the outside, I took the easy route and used an old TD cylinder picture. But, I'll take a pic on Monday of the actual part
Bernie
As I did not think there was a visible difference from the outside, I took the easy route and used an old TD cylinder picture. But, I'll take a pic on Monday of the actual part
Bernie
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RE: Cox Tee Dee 049 High Performance Cylinders
I suppose I’m missing something, but it seems that Bernie’s image could very well be a reworked SS, while it certainly can’t be mistaken for an original TD #4. See photos.
Al
Al
#31
RE: Cox Tee Dee 049 High Performance Cylinders
The first image is an original TD #4 cylinder, you can see the lower part of the number that is stamped in the port on the right, rather than below the port as it is on some other models.
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RE: Cox Tee Dee 049 High Performance Cylinders
Mr. Cox, I should have acknowledged in my previous post that your ascertain that the images were of a TD #4 was of course correct and moreover it was confirmed by Bernie. It’s just that I can’t see any semblance of a ‘4’ in either of his two images. And of my several TD 049/051’s the external configurations are all identical to the one in the photo, (other than being stamped with a 4 or a 5). Mine are obviously a different (earlier/later?) configuration. You do in fact have a keen eye.
Al
Al
#33
RE: Cox Tee Dee 049 High Performance Cylinders
I don't know about the keen eye, but I do have newly prescribed glasses...
The reduction of the outer cylinder diameter was on the earlier version I believe. Not sure about the purpose of the reduction, reduced weight perhaps, it was dropped on later models perhaps to reduce the number of machining steps. You'll find similar shape changes on the early Pee Wee and Babe Bee engines too.
The reduction of the outer cylinder diameter was on the earlier version I believe. Not sure about the purpose of the reduction, reduced weight perhaps, it was dropped on later models perhaps to reduce the number of machining steps. You'll find similar shape changes on the early Pee Wee and Babe Bee engines too.
#34
RE: Cox Tee Dee 049 High Performance Cylinders
Started thinking about the history behind the cylinder outer shape. I guess they started with a thin wall all the way apart from a lower lip to seal against the crank case. Then came the version where it is thicker around the ports, either to reduce distortion when warmed up or/and to reduce distortion when using the dis-assembly tool in the ports, and/or enabling a throttle ring around the exhaust ports. Then finally the latest version with thick walls all the way. I think all engine sizes underwent this development, all the way up to the .15.
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RE: Cox Tee Dee 049 High Performance Cylinders
Alright, new pics are now shown of the actual product and, yes Mr. Cox, you do have keen eyes
The #4 cylinders we received from Cox a couple of years ago are 100% identical inside and out compared tothe Surestart ones with the following exceptions:
- [*]#4 stamped inside one of the exhaust ports.[*]Open exhaust ports as opposed to the slit version. Also, the port was cut a bit bigger (deeper); inducing SPI
[/list]Hence my logic for being lazy and using photos from an old TD cylinder listing.
Bernie
www.coxinternational.ca
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RE: Cox Tee Dee 049 High Performance Cylinders
I just got back from holidays on the weekend and there is a box of carb parts waiting at the office that my competitor Matt sent me (we split the loot). However, I believe there are no servo arms andwe will need to source them first. I`ll have a look later today when I get to the office.
Bernie
Bernie
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RE: Cox Tee Dee 049 High Performance Cylinders
Thats ok Bernie, I understand. I however don`t need the control arm to survive, a carb without the control arm will do nicely. I retrofit a control arm for an 05 not long ago and would be more than hapy to do it again for my own so I can get some testing in.
I have been holding off ordering the other parts I need from you guys so I can minimize shipping.
Hook me up please...................
I have been holding off ordering the other parts I need from you guys so I can minimize shipping.
Hook me up please...................
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RE: Cox Tee Dee 049 High Performance Cylinders
I have not yet had time to go through the box of parts to see what part(s) is/are missing. Once that I am caught up with my current backlog I will do so.
The price of lying on sunny beaches for 3 weeks lol.
Bernie
The price of lying on sunny beaches for 3 weeks lol.
Bernie
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RE: Cox Tee Dee 049 High Performance Cylinders
OOOOOOh the dreaded woeful sunny beaches are to blame eh.....chuckle...........everybody deserves a break every so often, .........forgiveness pending backlog time delay`s endurance,,,just kidding lol
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RE: Cox Tee Dee 049 High Performance Cylinders
Bernie and other COX .051 TD Cobblers
The information in the attached Web Page may provide some food for thought about Exhaust ports, SPI, Bypass and booster ports. http://www.ancientalley.com/ancient/...nome/gnome.htm
Just kidding! Enjoy!
The information in the attached Web Page may provide some food for thought about Exhaust ports, SPI, Bypass and booster ports. http://www.ancientalley.com/ancient/...nome/gnome.htm
Just kidding! Enjoy!
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Large SPI gap
I know this is an old post.
When the "SPI" is too large, the manifold vacuum that was built up inside the crankcase is released,
and airflow through the venturi significantly decreases.
If the engine uses a venturi to draw the fuel into the engine, there is an insufficient amount air being pushed
through the venturi to create the low pressure used to draw fuel inside the venturi, unless an electric starter
is used. (In some cases an electric starter will not help).
If the engine uses a bladder, too much fuel will be delivered to the venturi, and not enough air will be pushed
through the venturi, unless an electric starter is used.
SPI or "Free Porting" works on all 2-stroke engines. It works because of outside pressure being exposed
to the crankcase. That outside pressure pushes inert gas into the crankcase and prevents the loss of fuel-
air mixture out the exhaust port, that 2-stroke engines are famous for. With SPI more fuel is burnt and converted
to power.
Without a muffler it works with atmospheric pressure, and requires the piston to momentarily expose the crankcase.
With a muffler, the pressure is greater, and so it may require the piston to overlap the bottom of the exhaust port.
But just because the exhaust port is closed, doesn't mean that the bottom of the piston is sealing the crankcase
from the pressurized exhaust.
Bill M.
The SPI piston was very hard to start and didn’t compare with the stock piston BECAUSE it was cut too short.
The SPI gap with the modified piston in either the stock or modified cylinder was almost “three times” greater than
that of the stock TD piston and cylinder. Too much air was allowed under the cylinder. I also think the large gap
affected the engine’s timing.
I am not sure SPI actually does much based on my testing.
The SPI gap with the modified piston in either the stock or modified cylinder was almost “three times” greater than
that of the stock TD piston and cylinder. Too much air was allowed under the cylinder. I also think the large gap
affected the engine’s timing.
I am not sure SPI actually does much based on my testing.
and airflow through the venturi significantly decreases.
If the engine uses a venturi to draw the fuel into the engine, there is an insufficient amount air being pushed
through the venturi to create the low pressure used to draw fuel inside the venturi, unless an electric starter
is used. (In some cases an electric starter will not help).
If the engine uses a bladder, too much fuel will be delivered to the venturi, and not enough air will be pushed
through the venturi, unless an electric starter is used.
SPI or "Free Porting" works on all 2-stroke engines. It works because of outside pressure being exposed
to the crankcase. That outside pressure pushes inert gas into the crankcase and prevents the loss of fuel-
air mixture out the exhaust port, that 2-stroke engines are famous for. With SPI more fuel is burnt and converted
to power.
Without a muffler it works with atmospheric pressure, and requires the piston to momentarily expose the crankcase.
With a muffler, the pressure is greater, and so it may require the piston to overlap the bottom of the exhaust port.
But just because the exhaust port is closed, doesn't mean that the bottom of the piston is sealing the crankcase
from the pressurized exhaust.
Bill M.
Last edited by wmazz; 12-31-2018 at 07:01 PM.
#43
049 Black Widow tuning
Engine used was my stock TD.049 with stock Hi-Comp Cox Glow Plug and Cox 5x3 “flexible” Black Prop. Fuel was Wildcat 25% Nitro
1) Stock Cox TD .049 (this is with the original Cox #4 TD cylinder)……….19,650 RPM
2) TD .049 with stock piston and modified cylinder….………………………20,000 RPM
3) TD.049 with SPI piston and modified cylinder…….………………………18,600 RPM
The SPI piston was very hard to start and didn’t compare with the stock piston BECAUSE it was cut too short. The SPI gap with the modified piston in either the stock or modified cylinder was almost “three times” greater than that of the stock TD piston and cylinder. Too much air was allowed under the cylinder. I also think the large gap affected the engine’s timing.
I am not sure SPI actually does much based on my testing. The modified cylinder with a stock piston, gave the best performance, even better than the TD cylinder.
1) Stock Cox TD .049 (this is with the original Cox #4 TD cylinder)……….19,650 RPM
2) TD .049 with stock piston and modified cylinder….………………………20,000 RPM
3) TD.049 with SPI piston and modified cylinder…….………………………18,600 RPM
The SPI piston was very hard to start and didn’t compare with the stock piston BECAUSE it was cut too short. The SPI gap with the modified piston in either the stock or modified cylinder was almost “three times” greater than that of the stock TD piston and cylinder. Too much air was allowed under the cylinder. I also think the large gap affected the engine’s timing.
I am not sure SPI actually does much based on my testing. The modified cylinder with a stock piston, gave the best performance, even better than the TD cylinder.
Troubleshooting the dud, a friend showed me how to lap sand the case at the carb/tank mount (1500 grit sandpaper put on glass and sprayed with wd40 and sanded in a figure 8 pattern), it knocks off the bulge of the 4 course carb/tank mounting screws (a black sharpie put on before the sanding will show the progress). This did not seem to help the dud motor,,,,but I got an idea.
Why not try it on where the cylinder screws in (effectively changing the timing). I passed my idea by a buddy that road raced the two stroke Yamaha RD400 (and was a auto/diesel mechanic), he said I should raise the exhaust ports (so not remove material, but add to it), so I made a 0.010" base gasket, this made it a super dud motor, lol.
To scientifically gauge what I was about to attempt I measured the height of where the cylinder screws in to the case (see picture of the red lines where I measured - from case to where cylinder screws in), I call this deck height, my normal two good motors was 78 thou (0.078"), the dud was 84 thou, instantly a big grin appeared. With the precision these cox motors are built to, wth was going on with this spec, 0.006" too tall.
I started by taking 5 thou off (glass/sandpaper/wd40, same as I mentioned above) and retesting, result was better, another 5 thou, even better, another 5 thou and was getting hard to start. Then I thought why it was hard to start, hmmm, way to much compression, perfect, the head gaskets were 5 thou, I can compensate with head gaskets, so for every 5 thou I removed from the deck, I added 1 more head gasket.
After continuing this process a few more times (I went down to 53 thou from 84), it turns out, 15 thou off the good motor (was 78 thou, now reduced to ~63 thou with 4 head gaskets (1 original +3)) was the best.
Results are with 10% nitro, Thimble Drone 5" balanced prop and plastic reed valve.
Bone stock good motor with 78 thou deck height = 17-18K rpm,
Bone stock dud motor with 84 thou deck height = 14K rpm,
Best was reducing to ~63 thou deck height (on all motors), with a total of 4 head gaskets, 25Krpm and one hit 26Krpm.
I have read this great motor tuning guide about 4 years ago (Rusty Knowlton linked it in my rcg thread), he mentioned spi, but never talks about lowering the cylinder to adjust it and compensate with adding head gaskets like I did, or hit the rpm's I did (with only 10% nitro) DELETED link, wont allow me to post it.
I see they make shims to go between the cylinder and case, this of course moves the cylinder up, so seems common knowledge since these parts were for sale. Moving the cylinder up on any of my 3 black widow motors tuned them into duds.This is the "deck" height, its the height of the case where I reduced to gain 7Krpm from stock (or 11Krpm from the dud).
I was fine tuning with a large hammer (0.005" at a time), I would think optimizing the cylinder height and compression on a finer scale could help. 25Krpm on a reed motor with 10% nitro was not bad, but, we always want more.
Deleted picture, wont let me post a picture, lol.
Last edited by --Oz--; 08-07-2019 at 03:40 PM. Reason: Formating nightmare :)
#46
So if I dropped from 5" to 4" prop I would be getting ~30Krpm on 10% nitro. Yea, I know its not linear. Have you ever checked thrust difference (thrust stand) or top speed difference with the 4 and 5" props"
Thanks, I read that 5 years ago when I posted lowering the cylinder in RCG, Rusty Knowlton linked it in my rcg thread, great info, but never talked about lowering the cylinder.
P.S. what up with it not allowing to post links? (it wasn't even my link I had to delete)
Last edited by --Oz--; 08-08-2019 at 12:09 PM.
#47
I do not know says I am a premium member perhaps that is why I was able to post the link?
I use Windows 10 and keep it updated.
Engine was using 25% nitro / 20% oil.
Thrust stand would be nice I do use a thrust calc to monitor how
much static rpm it will take to obtain useful thrust with the smaller props.
I use Windows 10 and keep it updated.
Engine was using 25% nitro / 20% oil.
Thrust stand would be nice I do use a thrust calc to monitor how
much static rpm it will take to obtain useful thrust with the smaller props.
#48
I do not know says I am a premium member perhaps that is why I was able to post the link?
I use Windows 10 and keep it updated.
Engine was using 25% nitro / 20% oil.
Thrust stand would be nice I do use a thrust calc to monitor how
much static rpm it will take to obtain useful thrust with the smaller props.
I use Windows 10 and keep it updated.
Engine was using 25% nitro / 20% oil.
Thrust stand would be nice I do use a thrust calc to monitor how
much static rpm it will take to obtain useful thrust with the smaller props.
#49
I do not know says I am a premium member perhaps that is why I was able to post the link?
I use Windows 10 and keep it updated.
Engine was using 25% nitro / 20% oil.
Thrust stand would be nice I do use a thrust calc to monitor how
much static rpm it will take to obtain useful thrust with the smaller props.
I use Windows 10 and keep it updated.
Engine was using 25% nitro / 20% oil.
Thrust stand would be nice I do use a thrust calc to monitor how
much static rpm it will take to obtain useful thrust with the smaller props.
#50
A thrust stand is not a really good gauge. A high pitch prop like an oversquare one, will not pull well but hooks up in the air later when it unloads. Often they barely survive a hand launch, but get some great speed. Best thing to do is fly and time it/measure it. All the calculators I have seen just multiply pitch by 1056 which is " per minute converted to mile/hr. Skinny blades and 1" diameter don't enter the equation. Bernie doesn't have any stock of TD style cylinders right now.