Two Engins one carb

[madtech]

Originally Posted by StianM

It should be the same rpm as long as they are driving the same load.

If you running two engines but on two diferent loads the rpm would be more dificult to match. A smal PLS picking up signals from the ignition and giving up the diference in a 4-20 mA output driving the trotles would be one option.

please tell me more

[alan white]

this I have to see. Keep us posted!

[StianM]

Originally Posted by madtech

please tell me more

I wrote PLS, but I mean PLC.

You could use some kind off input from some speedsensors or use some kind of sensor to record the ignition pulses.

The difference betwen the two signals could be converted into some kind off outsignal. One off the carbs trotle could be controled by a motor increasing the trotle if it's below a given value and decreasin if it's abow a given value or it could be controled by a praumatic/hydraulic cylinder where a valve could add preshure and a other release preshure to control the trotle.

A automation expert should be able to think something out. PLC's are no longer exstemly expensive, but still not as cheap as consumer electronics.

[alan white]

The engines are always going at the same RPM, being tied together to a common shaft. There would be no signal difference. As a theoretical solution to two engines not mechanically tied together, your idea would apply.
Even if the throttles were controlled as suggested, however, variation would still exist enough to cause the two engines to constantly hunt and react.
Maintaining a 180 degree phasing can only be accomplished by mechanical means. At some point beyond, unless a differential were used, the engines would always be tied together anyway, except seperately clutched, they would be tied together differently each time the throttle went to idle and back.
Good tuning is all that's needed. A tachometer isn't needed to fine tune because boat speed will give the best evidence of performance. The exception would be if the engines were tuned to achieve the highest RPM possible while diconnected from each other. Two strokes are likely, however, to run better at a richer setting than would give the highest RPM, otherwise falter under load. A four stroke might be RPM tuned, but these are two stroke engines.

A.

[StianM]

Originally Posted by alan white

The engines are always going at the same RPM, being tied together to a common shaft. There would be no signal difference. As a theoretical solution to two engines not mechanically tied together, your idea would apply.

I think if you read my earlier posts you will see that here I mean two seperate engines running seperate loads that nead same RPM.

running two engines the same load would be no problem. There is several Tugs running 4 engines for two propeller. Some runn 2xstraigh 6 for manuvering, 2xV16 for cruise speed and 2xstraight6 + 2xv16 for tug operation. (just a exsample)

Once you engage the clutch linking two engine to eatchother they is to be concidered a single powerplant.

[alan white]

Got it now. I missed your saying "...but on two different loads".

Alan

[madtech]

hey there guys here are some pics of the tri engin e set up and some other things.......... please remember that all has now changed and now i only have wo engines but loads of bits moved around any way


the first is the tri engin setup with large centrefugal clutch
the second is the two engines and universal joint
the third is with the two engines the universal joint and chaine and prop
oh aand the third is my foil design for the rear set

tell me wat you think

[alan white]

Good Lord! You must be having fun!

[madtech]

fun is the essense of design hehehehehe
that tri engin set up did look mean

[alan white]

Well, it appears to be alive and well in Sussex, in any case. Looks like stuff we used to do years ago (times ten)!

[madtech]

hehehehehe thier defo in sussex and yes thier old. those engines are identical 1957 atco 2stroke 97cc origional bad boys. they seem to be identical in construction to the seagull outboards of the time apart from the water cooled head

[madtech]

does anyone know how i can fit a tachometer to the engins so i can get a rev reading while in the craft. its not essential but it would be nice. actualy they are essential as a tachometer will allow me to see if the rpm to proformance change when i use different props and set ups. this craft is very experimental. i think i can use an older car rev counter and take a puls feed from the electrics in the fly wheel but dont know wat tachometerto use or how to fit it argh

and does any one know what how much to gear a speedo down???? i wanna take a mechanical feed from the rear of the prop and gear the speed down so the prop now acts like a wheel. so if a car wheel is 24 inches circumference i need to gear the speedo by hmmmmm (prop eg 9x6) 24 inches(wheel circumference) devided by 6inches(prop pitch) which gives me four. this in therory will give me my maximum speed(not accounting for prop slip. this can be ajusted later allowing for slip and drag. this craft is a hydrofoil based craft and should only have 3sq feets of water contact at full speed

[StianM]

Originally Posted by madtech

does anyone know how i can fit a tachometer to the engins so i can get a rev reading while in the craft.

http://www.bwieagle.com/tac-monitor.htm

Originally Posted by www.deif.com

Waterproof illuminated instrument, DLQW96-pc, IP66
Size (mm): Q96
Pointer deflection: 240°
Scale: Customised scale available
Protection: IP54, IP66
Illumination: Long life LED
Accuracy class: 1.5
Scale base colour: Black
Figures, div. lines: Black, yellow, red, green
Pointer: Yellow, white
Standard measuring
ranges, voltage: 0…1/100V DC, ±0.5/±100V DC
Standard measuring
ranges, current: 0…1/100mA DC, ±0.5/±100mA DC and 4...20mA
Type approved by: MED

We used Deif on our bridge panels at Rolls Royce, but I'm shure there is others that is cheaper or has instruments fitting your rpm range.