Torque Formula for Rudders

[GORDON MACKENZIE-2]

Hi
Can anybody help me out i am trying to work out the torque on my rudder to choose a ram ,  the wetted area is 1200 mm high it is a balanced rudder so 900mm behind and 200mm in front of the post and i am assuming maximum speed of 10 knots, i have had a look at the Vetus web page but cant get my head round the formula, maybe i should not have had that last glass of Vin Rouge last night.
Thanks 
 
Gordon Mackenzie
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[Mark]

I make the maximum torque 515Nm or 51.5 Kgm.
F=2.33 x A x V2
F=2.33 x 1.2 x 1.1 x (18.2)2     10Knots = 18.2 Km/h
F=2.33 x 1.2 x 1.1 x 342.25
F=2452.61N

b= (0.37 x 1.1) - 0.2
b=0.41 x 0.2
b=0.21


Torque = 2453 x 0.21 = 515Nm

51.5 Kgm

Ram to select by the above figures will be the MTC 52.
Regards
Mark Hughes

----- Original Message -----
From: "GORDON MACKENZIE" <[hidden email]>
To: <[hidden email]>
Sent: Sunday, July 06, 2008 1:37 PM
Subject: DBAm: Torque Formula for Rudders

> Hi
> Can anybody help me out i am trying to work out the torque on my rudder to
> choose a ram , the wetted area is 1200 mm high it is a balanced rudder so
> 900mm behind and 200mm in front of the post and i am assuming maximum
> speed of 10 knots, i have had a look at the Vetus web page but cant get my
> head round the formula, maybe i should not have had that last glass of Vin
> Rouge last night.
> Thanks
>
> Gordon Mackenzie
> -------------------------------------------------
> Visit http://www.barges.org for info, events, to buy and sell barges or
> equipment.  ------------------------------------------------------
> You can manage your records yourself, including unsubscribing and
> retrieving lost passwords at http://www.barges.org/newsgroups#maint 
> 6����r��xro�ÁU��������Ejj���

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[Julian Tether]

In message <[hidden email]>,
GORDON MACKENZIE <[hidden email]> writes
>Hi
>Can anybody help me out i am trying to work out the torque on my rudder
>to choose a ram ,  the wetted area is 1200 mm high it is a balanced
>rudder so 900mm behind and 200mm in front of the post and i am assuming
>maximum speed of 10 knots, i have had a look at the Vetus web page but
>cant get my head round the formula, maybe i should not have had that
>last glass of Vin Rouge last night.
>Thanks 
Best to let the supplier work it out.... They do it all the time.

Mine is now up and working just under 6 turns lock to lock 45-0-45 or if
I adjust it to minimum 14turns.
--

Julian Tether
Barge Parglena
e-mail: [hidden email]

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[J.Bishop]

Hi Gordon

Phone up Vetus on 0238 045 4507 and ask to speak to Kevin Pim and he will do all of the calculations for you!

Jeff

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]]On Behalf Of GORDON MACKENZIE
Sent: 06 July 2008 13:37
To: [hidden email]
Subject: DBAm: Torque Formula for Rudders


Hi
Can anybody help me out i am trying to work out the torque on my rudder to choose a ram ,  the wetted area is 1200 mm high it is a balanced rudder so 900mm behind and 200mm in front of the post and i am assuming maximum speed of 10 knots, i have had a look at the Vetus web page but cant get my head round the formula, maybe i should not have had that last glass of Vin Rouge last night.
Thanks
 
Gordon Mackenzie
-------------------------------------------------
Visit http://www.barges.org for info, events, to buy and sell barges or equipment.  ------------------------------------------------------
You can manage your records yourself, including unsubscribing and retrieving lost passwords at http://www.barges.org/newsgroups#maint 


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Visit http://www.barges.org for info, events, to buy and sell barges or equipment.  ------------------------------------------------------
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[al madorcha]

while vetus may be an easy but expensive option, (they use other peoples pumps and charge three times the amount etc) there are other ways to get yourself hydraulic steering. and it is possible to make yourself up to 85 degree or so either side rudder movement, depending on the piston stroke and eye placement with regard to central pivot point, i.e. top of rudder shaft. we chucked a disk on top and used a spread sheet to see how close the pivot points have to be and whether the piston was strong enough.

when we came to do ours last year my mech eng brother and i made a spreadsheet for the above calculations, but also with the option of using a 1:2 geared 90 degree universal joint thing.. which we scrapped as an idea, but the option is still in the sheet.

page 1 is where it all happens, there are our calcs and the vetus to compare. (bear in mind the vetus have some random assertions, with no reference factors, we did ours using all factors and no randoms; very similar though)

a variable displacement pump does sound like a good idea, we used an m+s hydrualic hkus model which gave 7 turns for our size piston, which we geared to 14 to ease the pain, also the shafts often are not strong enough for the latteral force of a direct mounted ships wheel hence the chain gear linkage between wheel and pump, which we will gear back to 7 turns when we eventually connect an extra engine mounted hydraulic pump to create power assisted steering.

sauer danfoss also make similar pumps i believe, make sure you have pressure release valves, seperate header/expansion tank, and non return up to a certain release point, that way you dont need to have a seperate wheel lock.


i hope this was more usefull than ramble, but here is the link for the spreadsheet, it should be straight forward enough.

http://rapidshare.com/files/127702407/hydraulic_ruddercalcs.xls.html


and last point of all, if your steering already functions well, leave it alone, it's no simple quick job to build a whole new steering system!