engine question

[nautical]

Hi everyone.

Volvo provides installation drawings in thier site. for this specific engine (D12 675) the drawings could be found in the link below. My question is are the gearboxes provided are only for reverse purpose or is it also for reduction. IF so how can I find the reduction ratios. I mailed them but so far got no reply from them.

http://www.volvo.com/volvopenta/glob.../downloads.htm

Thanks.

[FAST FRED]

The site lists both ZF and other gear boxes . All will probably be reduction gears , as few power boats use 1-1 gearing and diesels.

Look up the gear box site to find the reductions that fit in the box.

FF

[nautical]

hi Fast Fred,

Thanks for the reply. What are ZF gear boxes. I am very new to this. Does volvo has a gearbox site

Thanks

[gnab]

hi
go to Zf-marine .com you will find all details

[nautical]

Thank you very much Gnab, I have another qustions. they given ratios first and second. what are they. can you explain a bit of it.

[RANCHI OTTO]

In ZF web:

1) single speed
2) Light duty
3) on left side > matching programs
4) match to engine model

.....

Type your engine model and you will have the corresponding gearbox model.
Calculate the propeller characteristics for each gear ratio offered.

Than draw r.p.m. vs diameter opt., P/D.
Only one diameter will be near your max. , take that and the corresponding i (gear ratio reduction).

For the 14 knots speed I suggest an EAR ratio of 0.65

[nautical]

hi Ranchi good to hear from you again. Graph Rpm vs Diam opt or P/D (not very clear)

[RANCHI OTTO]

Sorry...I will try again!

In the ZF catalogue for the choosen model do you have a renge of gear ratios.

You divide the engine rpm with the ratios and you will find the propeller revolutions.

Foe example (4) ratios = (4) propeller revolutions.

Now you know
- Power
- Revolutions of prop.
- Speed
- 1-w

You calculate with the B-Series Wageningen taking Z=4 (blades number) and EAR (Expanded area ratio)=0.650 (4) Dopt and corresponding Eta0 and P/D.

Now check the max. installable diameter...and take the D near the opt.

[nautical]

ok thanks I am trying.

[lazeyjack]

an dont forget to allow 12% of D for clearance of the boat bottom

[RANCHI OTTO]

Better 15%...but not vertical!

design a circle (propeller diameter) in the right position with the bottom shape, the min. clearance has to be 15%.

[nautical]

can someone explain these power ratings does it mean if I use a the highest ratio possible i will get very low out put

[RANCHI OTTO]

nautical...take you time!

Read the definitions of pleasure/light/medium duties!

The definitions are according to the service hours pro years.

[nautical]

thanks, running out of time

[RANCHI OTTO]

ZF gearboxes limits:

Pleasure > 500 h/y
Light > 2500 h/y
Medium > 4000 h/y
Continuous > unlimited

Have a look on your choosen engines at how many hours/y service gives the max. power and than choose your ZF model.