The Best Vintage Cox Engine

mitchg95 wrote:the teedee's are faster

Thanks for the suggestion.

Regards
Giuseppe - Italy

no problem

Depends what you want it for.

duke.johnson wrote:Depends what you want it for.

I have use the only Cox Black Window, that i have buy around 40 years old.
I don't know the use of others 'vintage' models, but i want buy or Medallion or Tee Dee.

Thanks
Giuseppe - Italy

The .049 and .051 engines are so close in displacement, there is no measurable difference in performance. Of all the .049/051s, the Tee Dees are the fastest, but don't run as well on suction fuel feed. They will run on suction, but are just very particular about the fuel tank position. If you use one of several methods of pressurizing the fuel, the Tee Dee .049/.051 is by far the easiest, most dependable, and fastest Cox engine.

The Medallion, while very similar to a Tee Dee, is much more user friendly and runs very well on suction. It shares the same crankcase with the Tee Dee, but the carburetor and crankshaft are different, and the cylinder porting is much milder. One can be easily made faster with a different Piston/cylinder.

Of the Reed valve engines, there are so many variations of piston/cylinder and fuel supply configurations, that it depends on your specific need. The Reed valve engines with external tanks are much less finicky, other than tank positioning, than the tanked variety. If I plan to go fly a tanked reed engine, I always test run it in the shop before I take it to the field, because there are more things that can affect their performance.

Like Duke said, it's all about your application.

Rusty

RknRusty wrote:The .049 and .051 engines are so close in displacement, there is no measurable difference in performance. Of all the .049/051s, the Tee Dees are the fastest, but don't run as well on suction fuel feed. They will run on suction, but are just very particular about the fuel tank position. If you use one of several methods of pressurizing the fuel, the Tee Dee .049/.051 is by far the easiest, most dependable, and fastest Cox engine.

The Medallion, while very similar to a Tee Dee, is much more user friendly and runs very well on suction. It shares the same crankcase with the Tee Dee, but the carburetor and crankshaft are different, and the cylinder porting is much milder. One can be easily made faster with a different Piston/cylinder.

Of the Reed valve engines, there are so many variations of piston/cylinder and fuel supply configurations, that it depends on your specific need. The Reed valve engines with external tanks are much less finicky, other than tank positioning, than the tanked variety. If I plan to go fly a tanked reed engine, I always test run it in the shop before I take it to the field, because there are more things that can affect their performance.

Like Duke said, it's all about your application.

Rusty

Hi Rusty, thank you again for this long explanation, i have understand all very well, you english is very clear.
I not have great experience with this engines, and you suggestions is very important for me.

Regards - Giuseppe / Italy

Thanks about my English, Giuseppe. We have several members who's primary language is not English. When I write to them, I try to avoid slang and contractions (combining two words, such as "you are=you're," etc.). We're glad to have you with us.
Rusty

RknRusty wrote:Thanks about my English, Giuseppe. We have several members who's primary language is not English. When I write to them, I try to avoid slang and contractions (combining two words, such as "you are=you're," etc.). We're glad to have you with us.
Rusty

Thank you again Rusty and congratulations you is very kind and available. I'm glad the same.

Regards
Giuseppe - Italy

If your looking for performance, go with a Tee Dee.
Shawn

The more exotic engines have more power _potential._ To tap that potential, you need to allow these engines to rev and that means running a smaller prop.

If you load the engine down with a 6x3 or worse, a 6x4, then you can get nearly as much power out of a baby-bee as a tee-dee.

The idea is that you can get only so much torque out of a given displacement. If you have the port area to fill the cylinder at a given rpm, then you don't gain (and may even lose) torque by increasing the flow area. If you want more power, you need to increase rpm, and then you may need some more cross section to handle the greater air flow. Too much port area leads to lower gas velocity, which can hurt scavenging. The main reason a baby bee has only a single port probably IS to save production expense, but it also makes for an engine that works well at modest rpm.

If you put a smaller prop on a baby-bee, then the single transfer port and smaller venturi limit the airflow and torque falls off, so you don't get much more power, even if you are able to get the rpm up with a tiny prop. The reduced airflow lowers TDC pressure, which retards ignition, so you lose even more power.

The higher power engines are set up for freer breathing, and high compression heads advance the ignition timing, so you don't lose torque as the revs come up. But you won't get to the point that these features matter much if you are trying to swing a big club, and if the compression is too high, you might actually end up with less power that you'd get from a milder tuned engine, due to excessive ignition advance. The fixed intake timing on a tee-dee doesn't work so well at lower rpm either. Automatically adapting to lower rpm is one advantage of the reed engines, even if they are a bit restrictive.

On edit: I have always lived at high altitude 5000'MSL. Prop sizes and rpm will probably be different for sea level folks, but the basic principal remains: The path to more power is higher rpm, and the path to higher rpm is a smaller prop.

Also on edit: Adding nitro allows you to make more torque, (and thus more power and rpm for a given prop) and also advances ignition (unless you head gaskets to compensate). I have not played much with nitro content, so will leave discussion of such to those with more experience.

kevbo wrote:The more exotic engines have more power _potential._ To tap that potential, you need to allow these engines to rev and that means running a smaller prop.

If you load the engine down with a 6x3 or worse, a 6x4, then you can get nearly as much power out of a baby-bee as a tee-dee.

The idea is that you can get only so much torque out of a given displacement. If you have the port area to fill the cylinder at a given rpm, then you don't gain (and may even lose) torque by increasing the flow area. If you want more power, you need to increase rpm, and then you may need some more cross section to handle the greater air flow. Too much port area leads to lower gas velocity, which can hurt scavenging. The main reason a baby bee has only a single port probably IS to save production expense, but it also makes for an engine that works well at modest rpm.

If you put a smaller prop on a baby-bee, then the single transfer port and smaller venturi limit the airflow and torque falls off, so you don't get much more power, even if you are able to get the rpm up with a tiny prop. The reduced airflow lowers TDC pressure, which retards ignition, so you lose even more power.

The higher power engines are set up for freer breathing, and high compression heads advance the ignition timing, so you don't lose torque as the revs come up. But you won't get to the point that these features matter much if you are trying to swing a big club, and if the compression is too high, you might actually end up with less power that you'd get from a milder tuned engine, due to excessive ignition advance. The fixed intake timing on a tee-dee doesn't work so well at lower rpm either. Automatically adapting to lower rpm is one advantage of the reed engines, even if they are a bit restrictive.

On edit: I have always lived at high altitude 5000'MSL.  Prop sizes and rpm will probably be different for sea level folks, but the basic principal remains: The path to more power is higher rpm, and the path to higher rpm is a smaller prop.

Also on edit: Adding nitro allows you to make more torque, (and thus more power and rpm for a given prop) and also advances ignition (unless you head gaskets to compensate).  I have not played much with nitro content, so will leave discussion of such to those with more experience.

Many congratulations on this important report.
I must say that i'm learning a lot about these engines Cox, enriching my knowledge, very poor so far.
I really thank you very much for the time you have dedicated to these my requests.

Regards
Giuseppe - Italy

I'll argue power a little.  RPM does not create more useful power.  In fact at a certain RPM available power falls off.  This is true of all engines.

A larger diameter prop will produce much more thrust than a smaller diameter prop at a given RPM.  That larger prop will still make more thrust even if the RPM is reduced some.  Yes, there is a limit to reducing RPM and still getting improved thrust when going to larger diameter props.

In short every system has an ideal operating state.  Switching props, changing the number of gaskets under the head, switching plug temperatures, switching fuel...all this may (or may not) improve the performance of the engine and plane.

Phil

pkrankow wrote:I'll argue power a little.  RPM does not create more useful power.  In fact at a certain RPM available power falls off.  This is true of all engines.

A larger diameter prop will produce much more thrust than a smaller diameter prop at a given RPM.  That larger prop will still make more thrust even if the RPM is reduced some.  Yes, there is a limit to reducing RPM and still getting improved thrust when going to larger diameter props.

In short every system has an ideal operating state.  Switching props, changing the number of gaskets under the head, switching plug temperatures, switching fuel...all this may (or may not) improve the performance of the engine and plane.

Phil

Thank you very much for all this informations and explanations, i have understand very well all.

Regards
Giuseppe - Italy

For me the best "Vintage" Cox engine and my favourite is the 049 Space Hopper.

I am jealous of Ron after seeing one mounted in his Veco/Dumas

https://www.coxengineforum.com/t5088-next-up-veco-dumas-scout#67211

but



for me they have character!

ian1954 wrote:For me the best "Vintage" Cox engine and my favourite is the 049 Space Hopper.

I am jealous of Ron after seeing one mounted in his Veco/Dumas

https://www.coxengineforum.com/t5088-next-up-veco-dumas-scout#67211

but



for me they have character!

Hello But is the first time that i to see this model of Cox 049 Space Hopper. i like very much.
Thank you very much for this picture and for you reply.

Regards
Giuseppe - Italy

RR-1 ranks up there in performance.

Jason_WI wrote:RR-1 ranks up there in performance.

Very Very beautiful, this is the first time that i to see this Vintage model.

Thanks and Regards
Giuseppe - Italy

The RR 1 is definitely the best looking "Bee"! ( My opinion anyway)

It is charcterful!

ian1954 wrote:The RR 1 is definitely the best looking "Bee"! ( My opinion anyway)

It is charcterful!

Thanks, you have picture of this Cox Engine ?

Regards
Giuseppe - Italy

jorigger wrote:

ian1954 wrote:The RR 1 is definitely the best looking "Bee"! ( My opinion anyway)

It is charcterful!

Thanks, you have picture of this Cox Engine ?

Regards
Giuseppe - Italy

It is the one that Jason posted.

pkrankow wrote:I'll argue power a little.  RPM does not create more useful power.  In fact at a certain RPM available power falls off.  This is true of all engines.

A larger diameter prop will produce much more thrust than a smaller diameter prop at a given RPM.  That larger prop will still make more thrust even if the RPM is reduced some.  Yes, there is a limit to reducing RPM and still getting improved thrust when going to larger diameter props.

In short every system has an ideal operating state.  Switching props, changing the number of gaskets under the head, switching plug temperatures, switching fuel...all this may (or may not) improve the performance of the engine and plane.

Phil

Yes and no.  What we call "horsepower" (hp) is in most cases actually "brake horsepower" (bhp).  Aircraft engines (real ones that is) usually have their "shaft horsepower" (shp) quoted - that's a different thing and doesn't really concern us here.  Usually, for any given engine, the shp figure will be less than the bhp figure.  Bhp is entirely a calculated number, NOT a measured number, and it is nothing more than a function of (measured) torque and (measured) rpm (and a constant - k (bhp = torque x rpm x k).  I'm too lazy to Google what "k" is so you can do that for yourselves - it's a VERY small number, <1.)  All sorts of things can be changed to change the rpm at which the engine produces its max torque - ports, carburettor, exhaust, fuel, etc .  

If you can produce the SAME torque at MORE rpm then you will be producing MORE bhp.  
If you can produce MORE torque at the SAME rpm then you will be producing MORE bhp.
Plus any combination/permutation of that.
There is a limit, eventually, to how much torque you can extract from any given engine, as there is a limit to how many rpm you can make it do before it self destructs.  (In real engines piston speed is the major limitation to rpm.  A shorter stroke will give a slower piston speed at any given rpm.  This is why high performance engines are well over-square, and why Hardly Driveables wear out so quickly.)

Large trucks regularly produce similar bhp to many high performance cars, yet the truck can haul a road train and the car can't.  The car can do 200mph but the truck can't.  A 600bhp truck engine will produce around 2,500ftlb of torque, but at <2,000rpm.  A 600bhp sports car might produce 500ftlb of torque, but at maybe 10,000rpm.  (Just figures plucked from an arbitrary bodily orifice, but you get the idea.)

To achieve max thrust from any given model engine you need to play with prop diameter and pitch to have the engine run at the rpm where max bhp is achieved, which will be a little above the rpm where max torque is achieved.  Any more or any fewer rpm will result in less power and therefore less thrust.  QED!!

At this point I get out of my depth.  I don't know specifically how you balance diameter and pitch, because you can control max rpm using either.  Perhaps someone else can inform us.  I'd really like to learn how they interact.