surface drive hydro

[stupidbaker57]

It's getting there! A little wiring, some fuel lines and a cable for steering. Gotta love that Ebay for the rudder. Only 40 bucks. The steering bar is wood just for set-up.

[crowsridge]

Very cool! Go get it wet!!!!!!!!!! With lots of pics......................

[stupidbaker57]

Here's a picture of the final drive. It's 16 to 21. If I have to change it, all I have to do is change the sprockets.

[PAR]

I can't see all of it, but that's one seriously restrictive intake. PVC?

[stupidbaker57]

I bought a motorcycle that had been sitting for a long time. The carbs were junk. The manifold is just to see how good the engine was. Once I have the boat done, I will build a better manifold from steel tubing.

[PAR]

Get the air/fuel delivery path as straight as you can. No hard bends and surely no 90 degree stuff. The reasonable choice is mandrel bent tubing.

[IMP-ish]

Cool boat and really cool diy surface drive! Hope you post some pics of it running.

[daiquiri]

Originally Posted by PAR

Get the air/fuel delivery path as straight as you can. No hard bends and surely no 90 degree stuff. The reasonable choice is mandrel bent tubing.

I second this. That 90° elbow will eat quite some useful power from the engine.

[stupidbaker57]

Once I get it in the water and running to work out any design flaws (and there may be a few) then I'll build my intake. I've been an auto mechanic for most of my life so a manifold design won't slow me done when I get there.

[HydroRocket]

Awesome. I was actually researching for building one of these and I came across this website with a picture of your boat.
I'm going to find a salvaged motorcycle engine and try to drop it in a two person hydro (pickle fork style) cruiser for out on the river.

I will be starting my own build thread I think too.

Have you had a chance to test this yet?

What engine is that? (how many CC, HP, RPM's?)

With that surface prop like that you won't have much for get-up-and-go but you'll have a lot more high speed right?

[tunnels]

Originally Posted by PAR

Get the air/fuel delivery path as straight as you can. No hard bends and surely no 90 degree stuff. The reasonable choice is mandrel bent tubing.

ooooh you need to find a motorbike racer mechanic to tell you all about intake pipes and lengths ,shapes and sizes !! ,all these things can play a very important part in the way your motor will run at differant speeds and its performance at differant revs !!!
Outboards have a tube inside the housing that is worth looking at and can be changed for differant effects in performance MOSTLY big out boards !!
So with the carb mounted close to the motor with a long bell mouthed intake tube to the carb and you have air ram effect taking place !!differant lengths of tube and will change the revs at which it is a advantage and a disadvantage
Same with exhaust lengths as well , Cock them both up and you got a motor that wont like you at all and you will be searching for ever wondering why you not getting what you want .
In my younger days i used to race cars and also motor bikes . Making manifolds and Tuning exhausts was an art . On differant days in differant situations i had a sliding exhaust pipe to change the exstraction effect for differant conditions and rpms being used !!
Same with air intakes thats why they call ram tubes because thats how they work at the right rpms tthe air can change to be slightly pressureized
Air moving down a pipe if stopped monentarily there is a pulse of possitive pressure , at that procise moment if the motor sucks its like a slight turbo action . Intake air is ,start !, stop, start ,stop,each time pulsing specially with single cylinder motors Its not a smooth constant flow as you might imagion !!
But get it wrong and the pulse of pressure changes to suction and its trying pull the air back out of the carby and is trying to kill the motors performance and can totally upset the fuel to air mix . This is really old technology but used to be interesting and i have a box full of out of print books on this very subject !! from the 1950s and before !!

Without the bell mouth on your intake tube this also has a effect caused by air turbulance as its drawn over the sharp cut edge of the tube !! I used to make my own bell mouths by heating the first 1 inch of the tube red hot and smacking it down hard and quickly with a big block of wood over a beer bottle !! easy and quick !!,the longer the neck of the bottle the better the shape you get but have to be quick !!!!

[tunnels]

My God it must be your lucky day !!

http://www.datafan.com/Horsepower_Bl...ners-handbook/

This almost the same as one book i have from years gone by, the last 1/3 deals with pipes intake and exhausts so you can pull up a chair and get a dozen 6 packs and read till you hearts content .!!

If you think thats good wait till ya get a load of this one

http://www.datafan.com//Horsepower_B...akeTuning.html

Its really going to tickle ya pinkies

Story with some pictures

http://www.southernskies.net/page_in...okeengine.html

And just to stop you from getting board

http://en.wikibooks.org/wiki/Enginee...Stroke_Engines

[Frosty]

Originally Posted by tunnels;
Same with air intakes thats why they call [B

ram tubes [/b]because thats how they work at the right rpms tthe air can change to be slightly pressureized
Air moving down a pipe if stopped monentarily there is a pulse of possitive pressure , at that procise moment if the motor sucks its like a slight turbo action . Intake air is ,start !, stop, start ,stop,each time pulsing specially with single cylinder motors Its not a smooth constant flow as you might imagion !!

Its called reversion but an inlet can never be pressurized thats how a venturi works. The fuel comes out of the jet because of the depression caused by the ventui if you force air in you force fuel back down the jets.

A turbo compresses fuel vapour, never pressures the carb.

[tunnels]

Originally Posted by Frosty

Its called reversion but an inlet can never be pressurized thats how a venturi works. The fuel comes out of the jet because of the depression caused by the ventui if you force air in you force fuel back down the jets.

A turbo compresses fuel vapour, never pressures the carb.

I understand what you saying and the 2 stroke thing and racing is a whole thing on its own . been there and done many hours making hot up get !!. Theres some really interesting stuff in those pages believe me. There were and still are some very clever people !!

[baeckmo]

Sorry Frosty, but you are wrong there. The increased pressure comes from the pulsation of the intermittent flow in the pipe. When the inlet valve opens, a low-pressure wave is propagating with the velocity of sound from the valve towards the pipe inlet. There it is reflected against what is called an acoustically lighter medium, causing a shift in pressure. The reflected wave going back into the pipe is thus a pressure wave, and the length of the pipe is adjusted so that this pressure pulse arrives at the inlet valve during its closing sequence, at the rpm where the extra push is needed.

This goes for the inlet of both two- and fourstrokes. The exhaust of fourstrokes is "same but reversed"; i.e. the xh-valve creates a pressure pulse that is speeding down the xh pipe with the local speed of sound (depending on gas properties and absolute temperature), again reflected at an opening with the consequent shift of pressure. The resulting low-pressure wave should reach the xh valve during its closing sequence in order to clear the cylinder from xh-gas. The "open end" may be a diffuser, creating a longer pulse, effective over an increased rpm range, and reducing the overall pressure level in the pipe.

For the two-stroke, however, we first need the "suction" from the reflected and inverted pressure pulse to scavenge the cylinder. But then we need to "block" the outflowof gas and increase the pressure in the cylinder at the closing of the xh port. This is accomplished by a final reflection of the outgoing pressure pulse against an "acoustically denser" medium in the shape of a reverse cone with a reduced outled dia. The resulting shape is an xh pipe with a constant dia, followed by a diffuser (increasing cone), then a short constant dia followed by the reverse cone, ending in a small outlet pipe.

The tremendous power increase we have seen in combustion engines to a great deal stems from a better understanding of non-steady flow phenomena.

Funny, tunnels, have we met in the racing tracks somewhere in EU? I built some pretty successful 50 cc, 125 cc and 250 roadracing bikes back in the late 1960-ies and early -70 ties.