A prototype Cox Reed-valve marine engine

roddie Mon Apr 15, 2024 4:58 pm

So... I'd been thinking about a different approach to powering a 1/2A glow-engine powered speedboat. I've got the "jet-pump" drive in the works.. with a venturi-throttled Babe Bee engine for input-power. This combo needs to be tested.

A throttle is desired.. and I've been working on a custom exhaust-throttle ring for .049/.051 Cox cylinders. More on that later.....

I knew that I had an OEM/Cox .049 throttle-barrel and matched cylinder that I'd had for decades....... and never set-up. It was now time to try a configuration.

I cleaned/oiled the cylinder and found a random loose piston and crankcase assembly.. installed X2 used head gaskets with a glowhead.. to find really good compression. Very Happy

I had a plan for the back-end...as well as for the output-shaft.

The back-end would consist of the late horseshoe backplate/choke-tube combination with an added "snorkel" to raise the air-intake a little higher to help keep any bilge-water or spray from entering the venturi.

A prototype Cox Reed-valve marine engine Cox_ex12

I put a silicone tube-seal over the needle-shaft.. and I think that it will also help to keep the needle-setting from drifting.

A prototype Cox Reed-valve marine engine Cox_ex10

The 4 supplied screws are a good length. You can see that once I tighten them up; there will be ample threads.. but not such a length as to bottom-out in the case holes.

A prototype Cox Reed-valve marine engine Cox_ex11

One of my custom flywheels to accept a starting-belt.

A prototype Cox Reed-valve marine engine Cox_ex15

I'm looking for an old broken air-conditioner.. to cannibalize for its small diameter copper tubing to make a water-cooling coil for this one.

A prototype Cox Reed-valve marine engine Cox_ex14

rdw777 Wed Apr 17, 2024 12:55 pm

Roddie wrote:I'm looking for an old broken air-conditioner.. to cannibalize for its small diameter copper tubing to make a water-cooling coil for this one.

Nice project roddie…. Most small copper tubing in small AC units is considered capillary tubing and the id would be too small to pass much water…. Not sure if you have Hobby Lobby craft stores in your area but those around here carry K&S soft brass tube that bends easily….. If you find some stuff it as full as possible with thin stranded wire like from a lamp cord before bending, Prevents kinking…. A couple of bent pieces I did for a balloon tank….

A prototype Cox Reed-valve marine engine 3889f510

roddie Wed Apr 17, 2024 1:59 pm

rdw777 wrote:

Nice project roddie…. Most small copper tubing in small AC units is considered capillary tubing and the id would be too small to pass much water…. Not sure if you have Hobby Lobby craft stores in your area but those around here carry K&S soft brass tube that bends easily….. If you find some stuff it as full as possible with thin stranded wire like from a lamp cord before bending, Prevents kinking…. A couple of bent pieces I did for a balloon tank….

Thanks for that advice Robert. I actually ordered (Amazon) a small coil of soft copper tubing that has a 1/8" OD and 5/64" (.075") ID. I hope that's a big enough inner diameter for this app.

HalfaDave Thu Apr 18, 2024 12:05 am

Hi roddie.
I had a 'similar' GoldenBee setup with some 'Octura 1/2A prop stuff ', I got from the LHS.
Wrapped some 1/8th soft brass KS tube around the head with proper intake/exhaust to water cool it.
Hard part was, string starting it, setting the needle before it over heated.
The only way the water cooling works, is if it moves through the water...
Somehow,
I traded/snagged a busted up front end Cox SandBlaster power plant, and put it in.
(I wonder how many Cox cars have hit curbs ! Smile

)
The pull start was nice !
The big heatsink allowed me to set a good needle setting.
Full throttle worked good.
As soon as I throttled down, it quit. Something to do with prop/pitch perhaps...

If you don't mind a true story...
This was the first boat I built. And designed. (DeepV with 45deg deadrise Smile

)
Very fast on paper, fast standing still. 100mph tied to the dock.
Unfortunately, the Heathkit R/C gear of the day,
Ballasted it down to Crusier/Battleship manouverability.
Balsa planked with the latest then, polyester resin.
Cox engine and R/C moved on to other projects.
Here is the fun part,
One of our 'Cox Gang' got some 'Serious Fireworks'...
My boat got a 'Viking Funeral'.
A splash of gasoline in the bilge.
A bunch of cool fireworks, set off by a 3ft tall wick...
Obviously, you had to be there,
No Cox Engines were harmed that day...
Take care,
Have fun,
Dave

roddie Thu Apr 18, 2024 6:43 am

HalfaDave wrote:Hi roddie.
I had a 'similar' GoldenBee setup with some 'Octura 1/2A prop stuff ', I got from the LHS.
Wrapped some 1/8th soft brass KS tube around the head with proper intake/exhaust to water cool it.
Hard part was, string starting it, setting the needle before it over heated.
The only way the water cooling works, is if it moves through the water...
Somehow,
I traded/snagged a busted up front end Cox SandBlaster power plant, and put it in.
(I wonder how many Cox cars have hit curbs ! )
The pull start was nice !
The big heatsink allowed me to set a good needle setting.
Full throttle worked good.
As soon as I throttled down, it quit. Something to do with prop/pitch perhaps...

If you don't mind a true story...
This was the first boat I built. And designed. (DeepV with 45deg deadrise )
Very fast on paper, fast standing still. 100mph tied to the dock.
Unfortunately, the Heathkit R/C gear of the day,
Ballasted it down to Crusier/Battleship manouverability.
Balsa planked with the latest then, polyester resin.
Cox engine and R/C moved on to other projects.
Here is the fun part,
One of our 'Cox Gang' got some 'Serious Fireworks'...
My boat got a 'Viking Funeral'.
A splash of gasoline in the bilge.
A bunch of cool fireworks, set off by a 3ft tall wick...
Obviously, you had to be there,
No Cox Engines were harmed that day...
Take care,
Have fun,
Dave

Hi Dave, Yea.... this will be my first time trying a self-made water-cooling coil. I haven't run a glow-engine set-up for a marine application either. I am concerned about the engine's top-end overheating before I can get water flowing.. but I'm wondering if the reed-valve engines tend to run a little cooler than their high-performance/high-rpm big brothers? I think that most boat modelers who have run Cox engines in their boats have run the higher-performance Tee Dees. The Cox "Sea Bee" V-hull/shaft-drive model is powered by their .049 reed-valve engine which is not water-cooled.. and most that I've seen do not have the Cox heat sink installed either. The Sea Bee did have that recoil type pull-starter that you mentioned though. I've set my engine up to use a starter-belt via an electric starter.

I enjoyed your "first boat I built" story Dave.. Laughing

I don't think I could ever resort to a viking funeral for any of my models though.

davidll1984 Thu Apr 18, 2024 9:15 pm

Roddie It would be my pleasure to make you a cooling jacket of course you will have to wait a bit as I have limited time while the working season is starting again for me I work a lot but I still have the project of making some piece for you friends be patient I I will have a part available to resolve this overheating problem. The first prototype that I made is functional but too complicated to manufacture. I have to change the tool. I am waiting for a smaller boring bar.

A prototype Cox Reed-valve marine engine Img_2461

I really like your turbine idea and I think there is a good chance it will work very well. I almost bought one too but came with the hull I put it in my list of possible model for .049 Small Cox Logo

1/2A Nut Fri Apr 19, 2024 3:39 pm

"Jeffry Wohlt"
https://www.rcraceboat.com/

Will be using his .062 drive line in nylon tube with outer aluminum tub to save weight.
On weds he sent out .062 x 2mm couplings, 2 wire drives with drive dogs and fresh nylon.
I will tap the 2mm out for 5-40 thread.

- see weight mass load on the ball socket:

A prototype Cox Reed-valve marine engine Resize23

Goal will be a 30 mph with a TD .051 outrigger hydro based on known field data.
I have a handful of metal props to try this one will be use first to do test laps / trim and
compare to the Picco .05 that unloaded the prop to 39.72k rpm pass in a larger hydro.

A prototype Cox Reed-valve marine engine Imag4314

27 mph will be about all the Oct. 0924 prop can do if at 33k in a leaner TD size outrigger.

Small Cox Logo

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