Cox powered jet-pump for model Sprint Boat

This is a plunger/needle for the Ace/Cooney venturi-throttle designed for the Cox Bee (.049 reed-valve) engines. The backplate has an air-intake, consisting of a .063" diameter hole which is directly on-center with the engine's four tank-screws; making it easier to drill a guide-hole through the firewall for the .062" diameter plunger to pass through and into the backplate.

I want to be able to throttle the engine while the pump/drive is submerged.. to see "if" and "how far" I can throttle-down.

Here's a YouTube video of a full-scale jet-pump powered boat.. with twin supercharged Corvette engines..

That was a CRAZY GOOD Jet-Boat Vid.............. really

We had been experiencing a mild transition into spring; weatherwise.. here in New England.. but a recent couple of cold (32F) nights here in Northern Rhode Island spanked us... (where's the spanked us icon?)............. currently raining heavily.. at 02:07 am

davidll1984 wrote:It's a special project I can't wait to see the result and on what type of boat it will be used I hope it works it would be the first time that tubine of this type would be used on a Cox engine. This is really cool stuf

Thanks David. I'm watching your outrigger project with anticipation too! I've been distracted from this project for the last few weeks.. but it's kept me from making hasty decisions with it.

My power-panel battery needed charging.. which has since been taken care of. The pump test-fixture needs some attention. I want the first test to be "wet" which will require using the bathtub with a small amount of water drawn; just enough to cover the pump.. but not allow any water to enter the Bee engine's rear air-intake. I have an idea to try.. and will attach a photo after I work on it.

Here's what I came up with for testing the engine-pump combo in my bathtub. It will only require approx. 1" of water-depth to fully cover the pump's intake-grate.


.. and since water doesn't burn... we need to raise the engine's air-intake to only receive air..







I made an elbow-diverter for the water-cooling nipple found on the pump's stationary nozzle.. so I don't end up squirting water all over the bathroom floor.   Could I "cap it"? Sure... but I want to see how effective it would be if I decided to utilize it.





The Ace/Cooney style venturi-tube throttle.. It's not the best throttling solution for this application.. but I want to see if the engine will throttle-down under the load of the pump. What's interesting here is; the engine performance shouldn't differ; between the pump being stationary.. and being in a hull underway. An exposed propeller's feedback through the driveline will vary greatly by comparison..... wouldn't it?




A better option would be to fit an exhaust throttle.. and run a Sure-Start style (horseshoe) backplate with a choke-tube... double-acting as a snorkel; effectively raising the air-intake above the bilge. The only downside to the exhaust-throttle is; that I can't use my muffler-design... yet.  

davidll1984 wrote:The Ace/Cooney style venturi tube accelerator should be suitable and even work very well but for a better control It would be better to control with servo I can already imagine the fixture with the entire system propelling backwards and making it difficult to maintain a precise engine speed. It will have to be pressed into the bottom at the rear of the bathtub.   I've done this before but only once   But after filling the bathroom with smoke then I decided to do it outside i was doing it in a small  pool for children.  This was great, it saved me from making a mess in the bath and water everywhere in addition to the smoke but this was à big one wit nitro engine a OS .35  

Yes David, You are imagining the test fixture correctly. It will require being "pressed" (held-down firmly) against the floor of the bathtub. I'll need to check the length of my glowplug clip-wires.. as my power panel will be outside of the bathtub.. on the floor.. near the toilet. (Do we have a toilet emoticon?)

So... I'm not going to use the bathtub to test-run the pump.. ........... I know that you all wanted to see that.. but I want to continue to remain in the good graces of SWMBO.. (Lynne)

She'll detect the essence of even the slightest lingering amounts of methanol, castor, Klotz and nitro like a bloodhound.. so I'm going to locate a window-box planter to use as a tub outdoors.

Something like this one shown below..





It'll be easier all around.. because I'll be able to set everything on the patio-table  and stand upright while working. The weather is getting consistently warmer too.

Could get a kiddie pool and tether run the engine with an actual boat.

So............ I sourced a 30" window-box planter to use as a test-tub. Because it's a planter; I'll need to seal the drain-holes in the bottom.. but it's the perfect size for what I need.

I decided that an exhaust-throttle might be easier to "apply".. and also to control. I'd set-up another alternate-engine with the exhaust throttle.. and decided to swap cylinders.. and make a linkage. I made an aluminum cooling-coil too.





W.O.T. position shown below





Closed/idle position shown below





This exhaust-throttle is a new experience for me.. and during it's installation; I see mis-alignments in the drive... that I need to address.

I could "see" a fair amount of run-out/imbalance in the coupling.. so I decided to make/install a new .125" solid /music-wire shaft. It's a lot better than it was.. and we'll soon see if it works.