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"Cox Tee Dee .051 RC Marine"



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Post  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
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Post  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….

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Post  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.
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Post  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




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Post  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 ! 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

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.





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Post  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 Babe Bee .049
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Post  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.

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Post  roddie Tue May 07, 2024 10:50 pm

I'll probably try to run this engine/O-Ring starter-belt combo tomorrow.


A prototype Cox Reed-valve marine engine _187_o10


I increased the diameter of the O-ring from 1/8" to 3/16".


A prototype Cox Reed-valve marine engine _187_o11


The 1/8" O-ring was slipping and will require a flywheel assy. rebuild to narrow the groove.. but going with a larger diameter O-ring won't bottom-out in either the starter or the engine pulleys.. but also wont stick/snag/jam. The O-ring is basically riding-on-rails. Applying tension grips the idlers positively. It's the way you'd want it to crank your engine.

I made two different water-cooling coils; one of 1/8" Copper.. and one of 1/8" aluminum thin-wall tubings. I'll rig-up a 2L. gravity-feed water bottle with a pinch-off valve for testing.
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Post  F4D Phantom II Wed May 08, 2024 2:22 pm

Hello Roddie
                   I was thinking what was I going to use to start the marine engine and I thought that maybe a drive belt from a car might work. I went to the hobby shop and bought a Traxxas toothed belt to try. here is a pic.
                                                                          Juan

A prototype Cox Reed-valve marine engine Img_7323
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Post  F4D Phantom II Wed May 08, 2024 7:21 pm

Hello

               I modified a pulley I made to test the toothed car belt and It doesn`t Work The belt doesn`t have enough grip on the pulley and slips. back to the drawing board. Pic.                                                          
                                                                                  Juan

A prototype Cox Reed-valve marine engine Img_7324
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Post  1/2A Nut Wed May 08, 2024 9:06 pm

For boats the pully and flywheel needs to have a V groove for the belt to work.
I use the RC car small 4.5mm wide belts and they work fine with V grooves.
Turns over high compression Picco .05's and SH .07. If need be can back off
the glow plug then tighten once the engine is started.
A prototype Cox Reed-valve marine engine Img_2910

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Post  F4D Phantom II Wed May 08, 2024 10:24 pm

Hello 1/2anut
                    I had a V groove on my pulley but it was not wide enough to fit the belt so I decided to modify it to test and made a square groove. I will make another pulley with the information that you have posted and will widen the V groove on the flywheel to 3.5 mm also.  In my pulley I had installed a one way bearing from a pullstar unit from a model engine and made a stub with a C clip to install in my starter .So as the engine starts the pulley doesn`t load the engine as it freewheels. I just remembered that I had bought a sawing machine belt when I was working on the engine years back and it was a V belt. need to look thru my boxed stuff before I do anything. here are pics.
                                                                                       Juan

A prototype Cox Reed-valve marine engine Img_7327
A prototype Cox Reed-valve marine engine Img_7326
A prototype Cox Reed-valve marine engine Img_7328
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Post  roddie Wed May 08, 2024 11:51 pm

F4D Phantom II wrote:Hello Roddie
                   I was thinking what was I going to use to start the marine engine and I thought that maybe a drive belt from a car might work. I went to the hobby shop and bought a Traxxas toothed belt to try. here is a pic.
                                                                          Juan

A prototype Cox Reed-valve marine engine Img_7323


Thank you Juan. A toothed-belt would be the ultimate.. but there's the issue of a flywheel to mate with it. You will surely find that weight "adds-up" really quickly in a micro-scale RC model. There's a reason why there aren't more 1/2A glow-powered boats on the water. They're temperamental.

You and Brad touched briefly on flywheel weight/drive-mass. I don't know anything about that.. but I know that it must matter when attempting to get it all to work.

I thought that going with a larger diameter O-ring would be the answer to the belt-slipping issue. but I reexamined the physical properties of the pulley-system that I was using.. and reconfigured my flywheel pulley's width to be narrow enough to keep the O-ring from binding/catching. This required reworking the pulley-system on my elec. starter as well as the one on the engine. I'll be staying with the 1/8" diameter O-ring/belt.


A prototype Cox Reed-valve marine engine Cox_ma12

A prototype Cox Reed-valve marine engine Cox_ma11

This is the fly-weight/mass of my current drive configuration... for what it's worth..

in grams..

A prototype Cox Reed-valve marine engine Mass_i10

in ounces..

A prototype Cox Reed-valve marine engine Mass_i11

On the weight-scale was my flywheel assembly and drive-coupling(s). I'm putting together a 2mm wire-drive.. but actually more like a solid-shaft configuration.
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Post  F4D Phantom II Thu May 09, 2024 3:57 pm

Hello Roddie
                      I don`t know much about boats but I`m learning on the job. I don`t know if a light flywheel will work with the cox.049,that is I think that I might need  in my case to make one heavier than what I have. I`m placing a carburator and need to make sure the engine work properly at a lower RPM and at full power. So is going to be a trial and error job.
        Do you have a Boat for your engine or are you building one ,What is your boat choice for your engine? I will be reading your thread to learn.
                                                                              Juan
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Post  rsv1cox Thu May 09, 2024 5:07 pm

What Juan said, and you have got it going on this project. I'm watching.

Bob
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Post  F4D Phantom II Thu May 09, 2024 7:00 pm

Hello roddie
                 My sherline lathe doesn`t want to turn on so I took the motor off the lathe and it drives the lathe with a toothed belt  with 80 teeth the number on the belt is MB330 and is made in japan. I decided to try it on my starter and it grip real good. The belt is like the ones used in sawing machines. My mother had a Singer electric sawing machine and this belt looks the same. I will have to modify my flywheel by making a wider groove for the belt. I tried it on and the slot needs to be wider.

                                                                                    Juan

A prototype Cox Reed-valve marine engine Img_7330
A prototype Cox Reed-valve marine engine Img_7331
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Post  roddie Fri May 10, 2024 9:02 pm

F4D Phantom II wrote:Hello Roddie
                      I don`t know much about boats but I`m learning on the job. I don`t know if a light flywheel will work with the cox.049,that is I think that I might need  in my case to make one heavier than what I have. I`m placing a carburator and need to make sure the engine work properly at a lower RPM and at full power. So is going to be a trial and error job.
        Do you have a Boat for your engine or are you building one ,What is your boat choice for your engine? I will be reading your thread to learn.
                                                                              Juan

Hi Juan, Thank you so much for your interest in my marine model project. I don't know much about boats either. I'm literally floating by the seat of my pants.. Laughing so.. don't put too much stock in my methods.. because they're not proven yet. I'll be learning from you, David and Brad. I feel that I have a good sense of the way things work; enough to put me in the ball park.. when designing a model.

I have two boat projects that I'm working on.. but one needs to have its drive-system "proven-out". It's a jet-pump drive designed to use a brushed electric 380 series motor. I built a "test-tub" fixture to see how the drive behaves when submerged.. and if the engine will actually run when connected to it.

The other model is a self-designed outrigger hydroplane with a surface-drive that I've actually been spending more time on.
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