Did a dream got shattered?

Glad to find new threads,,this one is a bit daunting technically for me but I'll try and see if I can wade thru enuff to see whats going on here if I dare...BTW...tomorrow will be interesting... weather should be nice for sailing in the bay at least...

I also prefer stoners to drunk people anytime....If anyone is "baked" they are't getting aboard though...Glad we will be journeying only about 2 miles or so and then the teens must debark and set up there camp while I have a quiet night aboard hopefully...maybe fishing for some flounder or whatever I can catch near the creek head. Getting late so I'd better get some sleep...



PS Hope I havent killed your thread...sorry again for my rant and thanks for accepting my apologies!

 

Good morning tugboat,

Maybe it is even wors as I first thought when I made this bloob of proposing those small hydraulic motors to you. Lets see whether we can re-calculate again.
It is stated : 585 revs per minute maximum i.e. 9.75 revs per second maximum.
It is also stated : 1368 inchlbs. One inchlbs = 2.54 cm x 0.45 Kg = 1,143 kgcm or 0,01143 Kgmeter. One horsepower = 75 kg lifting 1 meter in one second . Am I correct in saying that I must multiply 0.01143 x 9.75 revs/second = 0,1144 Kgm/second. Thus the motor is only 0,001525 horsepower. Tugboat, I think we should both have a good laugh. I am really sorry about it. Souljoul, you were right, I was a nutcase.

Tugboat, as an alternative, I would just have the diesel driving a single prop. Added to this, a small 12 HP ev motor. Have some brackets made around your tugboat and you could move this ev motor with prop around on the postion you like to have some extra tugboat pushpower. Have it remote controlled I am just thinking aloud now.

Also there was a thread with one diesel engine and two shafts with 2 props.
Could that be a solution for you?.

As a last resort, you could have 2 ev motors with props and the diesel driving 4 generators, like you original suggested.
bert

 

Burtku I could be wrong its been a long time but I think Hp ratings for motors is in Hp/hr while Hp definition is in seconds. That would make the motor around 5.5 hp? Remember Hp can be converted to KWH by multiplying by 0.746. I could be nuts here too.

 

Keep it simple Bert.

1368 in-lbs = 114 ft-lbs = 15 kgf-m.
585 rpm = 10 rps.

So the hydraulic motor is 2 hp.
You could have guessed that from the weight also.

 

souljour--No probs..try to understand there are people who come on here and just try to debase others for no apparent reason...I apologize also...
good luck on your quest --i dont envy your position...

 

good morning Bert, Actually i have this calculator it seems to wrok well and there is also a forum on her call hydraulic drive or something=--the guy used the same set-up you gave me...the engines for hydraulics like you suggested are in the 15 hp range. but remember that torque is much greater..hence although ill only make 5 knots i can push two large props...I would use a reservoir for back pressure. I talkeds to some experst yesterday and they think it could work well too!! no worries...i would not hold anyone responsible for my choices... I still will figure out how to build twins. if not i have the cat for back-up...

for future reference i used the prop calulator after i found out the aprox hp with the correct rpms.

http://www.baumhydraulics.com/calculators/motor_calc.htm

 

the thread on here is by ,mako2..he uses 22x 22 inch props in a ulstein-like thruster. twin props. all hydrualics..uses almost the same size engines you had you suggested

 

I'm not so sure tugboat. The calculator uses only pressure and fluid flow, but the data you supplied is max flow, max pressure and max. rpm. I think these numbers cannot exist at the same time.

Only if the hydraulic motor can handle a certain flow @ a certain pressure, the calculation can be correct (10 hp). But there is also a torque limit given (1368 in.lb.), restricting the output to 2 hp @ 585 rpm.

 

Hi CDK You made my day better. I forgot to multiply it by 1368 (inchlbs)
the final result is indeed 2,0327 Horsepower.
Bert

 

CDK- wouldnt the torque though be sufficient for my purposes?...even if it was 2 hp, wouldnt it be enough???.or would it just not work?
for sure, i wondered about the rpms in that calculator. why the rpm factor wasnt included...
what about those golf cart engines..they are rated 12 hp, but wouldnt they be more powerful at lower rpms than a diesel of identical hp?.
and wouldnt the hydraulics do the same work as a electric motor at higher hp?

hmmm...im glad at least i have time to sort this all out...thanks!

 

2 hp at 10 RPM is one hell of a lot of torque...

-Tom

 

It sure is Tom.
But in this case it is 10 RPS(econd), so only 1/60th of a hell of a lot and that ain't much....

 

H Tugboat,

yes CDK is right, you cannot use that calculator without taking the maximum ratings into consideration. For that reason (CDK please note) I tried to do it step by step, to enable you to get information on motors from other sources and could calculate yourselve. Sorry I made a bloob and forgot the maximum inch-pounds torque.
Bert

 

Sorry tugboat, but no.
To make the 2 HP available, the props must be so small and low pitched that they would turn at 585 rpm. The ones you have in mind require much, much more power to reach that.

 

A simple rule of thumb, "1 gallon per minute @ 1500 psi is equal to 1 HP" most pumps and motors show displacement in cubic inches per/revolution. 231 cubic inches in 1 gallon. The RPM will give flow volume and pressure will reflect the power.

3,000 psi and a flow rate of 1/2GPM is still 1 HP.

Hope that helps. (from Womack Design Engineering Manual )

Ron