Turboshaft Outboard - Jetboating for Gentlemen!

[smithy1]

Hi Anders,
The FADEC signal to the pump is just varying the voltage to the pump depending on throttle position and sensed engine rpm....it will then adjust the voltage to the pump to keep the rpm at the required level as demanded by the throttle signal, they're fairly simple animals really.

If the free power is only doing ~10,000rpm, the normal bearings will handle it easily as long as they're lubed sufficiently and temps don't get too high. I would point a lube spray at the upper bearing and let gravity feed the lower one if possible. Let the scavenge drain back to tank via larger dia line and possibly a filter and you should be good to go....I'm sure you've got something in mind...if you can successfully run the bike without too much drama, the outboard motor should be easy for you...

Cheers,
Smithy.

[nersut]

Hi Anders

Just making sure that you have removed the rubber impeller waterpump on the input shaft near the gears, so there won't be a big stream of seawater spray from the shaft tunnel on your nice engine.

Looking forward to see it working, what type and size of boat are you going to test your turboshaft outboard on? :-)


Cheers
Erik

[smithy1]

Sept 8, 2014 22:10:32 GMT -5 nersut said:

Hi Anders

Looking forward to see it working, what type and size of boat are you going to test your turboshaft outboard on? :-)


Cheers
Erik

LOL....Knowing Anders...it's probably going on something "ICE" related, ....and with winter coming up in that part of the world it would make sense..! He'll possibly have it powering a snowmobile at some stage..!

Cheers,
Smithy.

[Johansson]

Smithy: I managed to wreck the bike freepower bearings after all...

Erik: Didn´t think about the impeller, you just saved me a cold shower! *LOL*

I´ll borrow a small aluminum boat from my brother to test it on, but first I think I´ll try it out in a water filled oil drum just to see if the damn think will work at all.

[Johansson]

Today I modified a brake cylinder from a pocket bike and fitted it to the motor, as you can see I will use the sprocket as a brake disc to lock the freepower shaft while shifting into reverse.



Cheers!
/Anders

[racket]

Hi Anders

Neat solution :-)

Cheers
John

[smithy1]

Hi Anders,
Some of the "chain driven" Harley-Davidson machines with aftermarket sprocket/disk rotors have this type of setup...very clever indeed. Hopefully you won't get too much chain lube on the sprocket.....could cause a little "slippage" methinks..!

[Johansson]

Thanks!

Good point there Smithy, but with the engine at idle it should still be able to hold the freepower rotor still I think.

To keep the oil in the shaft tunnel from leaking past the lower bearing onto the sprocket I think I will keep the rubber seals intact on the lower bearing, at <10.000rpm the original grease should be enough for lubrication. The upper bearing might need some oil cooling though, and a constant oil flow should reduce heat soak.

I´ll try to make an oil jet that piss oil at an angle onto the upper bearing and then let it drain through a large port just above the lower bearing back to the tank. I could actually keep the boat impeller and route the water through a couple of turns of copper tubing inside the oil tank to keep it from overheating.

Cheers!
/Anders

[enginewhisperer]

Since the water pumps are the main cause of trouble with outboards, I'd probably avoid using it - but it's definitely tempting when you have an unlimited supply of cooling water!

I've been thinking the same with an electric outboard I'm building. It'd be nice to have cooling, but not having the water pump is a big advantage over the original engine

[Johansson]

If the water pump is what causes me most grief on this motor I would happily change an impeller every single day. :-)

[enginewhisperer]

haha, good point!

[Johansson]

I found some time in between house painting and garage building to continue on the outboard project, I would really like to try it out in the lake this summer.

Late tuesday night I wacked together a crude test stand in wood, I am glad my metal working skills are a bit better than what I can manage in wood...



The morning after I got up early to finish wiring the engine up and fit a brake handle, the battery pack for the ECU was charged and everything set up for a test start.



Unfortunately the batteries were crap, they lost the power just when the engine was about to reach self sustain so I had to abandon the test and order a 12v-7.2v regulator so I can use a car battery instead. You can see the smoke coming from the intake, at least the workshop smells nice now.



Cheers!
/Anders

[smithy1]

Hi Anders,
This is indeed an interesting project....is it possible for you to use a 2 cell 7.4v Li-Po..? I assume you're using a blower to start....do you need an electric starter motor for it..I may have a suitable one floating around at home...

Cheers,
Smithy.

[Johansson]

Hi Smithy,

I could use a LiPo but I prefer a sturdy 12V car battery that will last the entire fishing trip.

The engine is started with a motor starter, the threads in the aluminum bracket are damaged so I hold it by hand. I´ll figure out a better bracket design that also incorporates a FOD screen and print it out in PLA when time permits.

Cheers!
/Anders

[smithy1]

In that case I'd suggest a decent motorcycle battery, the turbine electronics use very little in the way of mah....My little jet dragster uses an average of ~180mah per 5min run.... and it has twin afterburner pumps as well as the engine pump, ECU, radio receiver and servos etc....my 3 cell 9.9v Li-Fe 4200mah battery will easily last me ~20 starts..even after all that it only takes ~4000mah on re-charge.

I think you'll be very surprised how little power your setup will use...and you're only running the one pump and ECU etc...

Cheers,
Smithy.