Model Boat Mayhem - Forum

Please login or register.

Login with username, password and session length.
Pages: [1]   Go Down

Author Topic: Prop shaft oilers  (Read 6128 times)

MichaelK

  • Guest
Prop shaft oilers
« on: July 27, 2011, 03:32:05 AM »

Just another quick question,
Does the top of the prop shaft oiler need to be above the water-line?
I can see arguements for both answers (yes or no), but I can't really decide.
Thanks
Mick
 
Logged

brianB6

  • Guest
Re: Prop shaft oilers
« Reply #1 on: July 27, 2011, 04:19:40 AM »

Good question  O0
If you can, yes. But remember the inner end of the shaft has to be above the waterline as well or there is not much point.
If you can't, no.
If the oil runs out quickly, you are better off using a thicker oil.   
I think the idea is that the oil stops water entering the shaft because of its greater viscosity as well as lubricating the bearings.   {-)
I made a tight fitting cap to go over the top of mine.
Logged

derekwarner

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 7,950
  • Location: Wollongong Australia
Re: Prop shaft oilers
« Reply #2 on: July 27, 2011, 07:58:36 AM »

 :embarrassed: ...Mick ...we really must go back to 1st principals here  O0

1. atmospheric pressure acting on the water is shall we say 1 atmosphere or approx 1 Bar
2. the pressure created @ 1. attempts to push water through the diametrical clearance between the prop shaft & the prop shaft tube
3. to counter this we also have a second differing atmospheric pressure acting on the same dimensioned diametrical clearance between the prop shaft & the prop shaft tube tryng to keep the water out
4. the krux of the matter is that the higher above sea level....the lower the pressure...hence water will always be forced from the lower point to the higher point

We may be only talking 3 to 10 mm in elevation height........but scientific fact is scientific fact

Try a Mayhem search.........there a a number of threads on lubrication of prop shafts ........some suggest water proof grease....some suggest it is too viscious ...some suggest olive oil as being environmentally friendly........

Derek  :-))
Logged
Derek Warner

Honorary Secretary [Retired]
Illawarra Live Steamers Co-op
Australia
www.ils.org.au

essex2visuvesi

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 6,146
  • Location: Finland, England, Finland!
Re: Prop shaft oilers
« Reply #3 on: July 27, 2011, 01:10:44 PM »

I use marine grease in mine... Its meant to be used in 1/1 scale outboard motors and is kind to the environment :)
Logged
One By One The Penguins Steal My Sanity
Proud member of the OAM  (Order of the Armchair Modeller)
Junior member of the OGG  (Order of the Grumpy Git)

geoff p

  • Guest
Re: Prop shaft oilers
« Reply #4 on: July 28, 2011, 07:28:44 AM »

According to Derek's #4, if we simply have an open tube from water-level to say deck-level, it will continuously 'pump' water up to the deck.

I don't think so!

My outboard bearing is plastic and is simply water-lubricated, while the inboard bearing is Lignum vitae (well, a bit of hard wood, anyway), which seems to accept the various side-thrusts imposed on it by various gear- or belt-drives, depending on the motor-of-the-moment.  Between the two bearings is an aluminium tube, and joined to it somewhere a plastic tube allows Vaseline to be injected on the odd occasion when I remember - a 5cc disposable syringe holds a season's worth of Vaseline.

Geoff
Logged

derekwarner

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 7,950
  • Location: Wollongong Australia
Re: Prop shaft oilers
« Reply #5 on: July 28, 2011, 08:25:34 AM »

 {-) ...sorry Geoff... but you cannot modify proven science nor physics   <*< ........... as you will not win  <:(

....point 4. below is fact.... 4. the crux of the matter is that the higher above sea level....the lower the pressure...hence water will always be forced from the lower point to the higher point

You have added a third dimension .......being the injection of a high viscosity grease which will naturally impede the ingress of water to a higher level in the angular prop tube ...... O0 :-)) .....Derek
Logged
Derek Warner

Honorary Secretary [Retired]
Illawarra Live Steamers Co-op
Australia
www.ils.org.au

MichaelK

  • Guest
Re: Prop shaft oilers
« Reply #6 on: July 29, 2011, 01:03:17 AM »

Thanks folks for all the differing views!! :o
I think I'll just fill it prop utbe with oil, put the boat in the bathtub, and see what happens.
If it passes water out of the top of the oiler, I'll go to plan "B" :-))

Derek, your point 4," ...hence water will always be forced from the lower point to the higher point" I can't quite figuer out. {:-{
Most rivers (I believe) run from the top of the hill DOWN to the bottom, no matter what the height above sea level it is at. O0
It normally takes a pump, (of some type... electric power, hand power, clak pump, bucket...) to make water go uphill.
Water has a tendancy to find it's own level. (I think Newton said that, thou I may be wrong about the name.) Which makes me think that if the top of the oiler tube is below the water line, water will come through the diametrical clearance between the shaft and bearing, and out either the inner end bearing or the top of the oiler, and eventually find equilibrum at the water line. eventually the boat will sink! O0 <:( <:(
Mick

 

Logged

HS93 (RIP)

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 2,949
  • I cannot spell , tough
  • Location: Rainhill UK
Re: Prop shaft oilers
« Reply #7 on: July 29, 2011, 01:31:21 AM »

{-) ...sorry Geoff... but you cannot modify proven science nor physics   <*< ........... as you will not win  <:(

....point 4. below is fact.... 4. the crux of the matter is that the higher above sea level....the lower the pressure...hence water will always be forced from the lower point to the higher point

You have added a third dimension .......being the injection of a high viscosity grease which will naturally impede the ingress of water to a higher level in the angular prop tube ...... O0 :-)) .....Derek


Derek  ..How does a centre board box on a yacht work then ?
Logged

geoff p

  • Guest
Re: Prop shaft oilers
« Reply #8 on: July 29, 2011, 03:36:24 AM »

Derek,
I agree that atmospheric pressure reduces with height above sea-level but I cannot agree that water will be forced from the lower point to the higher one.

What you are suggesting means we could use a hollow mast, open at its foot to the water, and let 'scientific fact' cause the mast to fill with water?  From where it could flow back down, by gravity, giving us a perpetual motion?

You know as well as I do, you are mixing-up the 'scientific' properties of two materials, water and air:  take into account the vastly different specific gravities of the two, the water will attempt to maintain a constant surface-level.  It would be a bit embarrassing if hydro-electric schemes found their water was flowing back up the mountain because "water will always be forced from the lower point to the higher point"  It does however flow from the higher pressure (headstock) pipe, across the turbines, to the lower pressure (tail) pipe where the pressures are both water-pressure not air pressure.

I think what you are actually trying to say is that water will flow from the (relatively) high water pressure in the tube to the air pressure inside the hull:  water pressure increases (about) .15 psi per foot of depth so, if the inboard end of the prop-tube is two inches below water-line the water in it is at a pressure 1.005 atm (=14.7700psi) compared with inside the hull, which is at 1 atm (14.6959 psi) (BTW, I used this tool to get these numbers: http://www.calctool.org/CALC/other/games/depth_press)

Geoff
Logged

derekwarner

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 7,950
  • Location: Wollongong Australia
Re: Prop shaft oilers
« Reply #9 on: July 29, 2011, 07:30:22 AM »

 :embarrassed: ....Guys....this is a very interestion simple little tool....http://www.calctool.org/CALC/other/games/depth_press & can be applied directly to our question/delima of ...air pressure/water/elevation & the combined effects with each other

So in an attempt to prove my point... O0 I chose a fine Stewart crystal wine glass +150 ml of water + a clear plastic drinking straw elevated @ approx 45 degrees from the surface of the water

I truely expected the water to be pressed up into the straw by the higher air pressure acting on the surface of the water & overflowing from the top of the straw 130 mm higher than the water level & leaking down the casing of my computer

Oh well........ >>:-( back to square one...........Derek  :P
Logged
Derek Warner

Honorary Secretary [Retired]
Illawarra Live Steamers Co-op
Australia
www.ils.org.au

Peter Fitness

  • Global Moderator
  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 6,802
  • Location: Wyrallah, near Lismore NSW Australia
Re: Prop shaft oilers
« Reply #10 on: July 30, 2011, 12:27:35 AM »

I use marine grease in mine... Its meant to be used in 1/1 scale outboard motors and is kind to the environment :)

So do I, with excellent results.

Peter.
Logged

Nige52

  • Guest
Re: Prop shaft oilers
« Reply #11 on: July 30, 2011, 08:50:51 AM »

:embarrassed: ....Guys....this is a very interestion simple little tool....http://www.calctool.org/CALC/other/games/depth_press & can be applied directly to our question/delima of ...air pressure/water/elevation & the combined effects with each other

So in an attempt to prove my point... O0 I chose a fine Stewart crystal wine glass +150 ml of water + a clear plastic drinking straw elevated @ approx 45 degrees from the surface of the water

I truely expected the water to be pressed up into the straw by the higher air pressure acting on the surface of the water & overflowing from the top of the straw 130 mm higher than the water level & leaking down the casing of my computer

Oh well........ >>:-( back to square one...........Derek  :P


Perhaps it's because you're upside down that the water didn't run up the straw? Maybe it will in Alaska?
 {-) {-) {-)
Logged

HS93 (RIP)

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 2,949
  • I cannot spell , tough
  • Location: Rainhill UK
Re: Prop shaft oilers
« Reply #12 on: July 30, 2011, 10:04:17 AM »

Ah that's it the blood has run from his brain to his feet  :} :}


peter %)
Logged

RaaArtyGunner

  • Guest
Re: Prop shaft oilers
« Reply #13 on: July 30, 2011, 11:02:48 PM »

Ah that's it the blood has run from his brain to his feet  :} :}


peter %)

No, the water goes own the plug hole in opposite direction also, because we are the right way up.

Don't forget that there are Hornary Aussies Amungst ya all.

Logged

john44

  • Guest
Re: Prop shaft oilers
« Reply #14 on: July 31, 2011, 02:24:25 PM »

I remember seeing or reading somewhere someone used an old Humbrol enamel paint tin soldered to the top of the oiler tube,
which was filled with oil down at the lake and the lid re-fitted. I think the lid had a small hole drilled in it to stop a vacuum/air bubble
happening and the paint tin acted as a gravity fed oiler.
    I have,nt tried this idea yet, but I think it is a good one.

john 
Logged

HS93 (RIP)

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 2,949
  • I cannot spell , tough
  • Location: Rainhill UK
Re: Prop shaft oilers
« Reply #15 on: July 31, 2011, 05:51:13 PM »

I have used these in the past, some people use grease some like oil but you have to watch out using grease because some suppliers are using very small dia tubes so there is very little gap between the shaft and the outside of the tube , and this can cause drag.

I uses Stainless steel bearings at the top and Acetal at the prop end the oil is just to coat the shaft to stop anything sticking to it and also to protect the bottom bearing when running out of the water,
I only put a few drops in each day I sail

Peter
Logged

john44

  • Guest
Re: Prop shaft oilers
« Reply #16 on: August 04, 2011, 02:38:11 PM »

Hi peter, What are the oil feeders you have used on the boat in your picture & where did you get them from ?

regards

john
 
Logged

RaaArtyGunner

  • Guest
Re: Prop shaft oilers
« Reply #17 on: August 04, 2011, 09:37:07 PM »

Peter,

Good practical photo, neat installation,  :-)) :-))
Logged

HS93 (RIP)

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 2,949
  • I cannot spell , tough
  • Location: Rainhill UK
Re: Prop shaft oilers
« Reply #18 on: August 05, 2011, 12:33:04 AM »

they are free flight oil tanks most model shops stoked them at one time they came in a few sizes  these where the small ones.ill look about for who has something similar

Peter
Logged

john44

  • Guest
Re: Prop shaft oilers
« Reply #19 on: August 06, 2011, 02:33:44 PM »

Hi peter, thanks for that I will  ask at my local model plane shop to.

regards

john
Logged

john44

  • Guest
Re: Prop shaft oilers
« Reply #20 on: August 11, 2011, 11:20:03 AM »

Hi Guys, I have found a supplier for the free flight " fuel tanks "the same as Peter has used
They are available from a site called Flitehook , they do them in 3 sizes. I have ordered some
so I will let you know what they are like.

thanks again Peter

regards

john
Logged

john44

  • Guest
Re: Prop shaft oilers
« Reply #21 on: August 11, 2011, 07:36:03 PM »

Hi again,
I ordered the free flight fuel tanks yesterday at about 11am,from ( flitehook ) they arrived this afternoon.
Excellent service. they are exactly like those on peters installation, but with a blue top.
  I also ordered the small bore fuel pipe too.

john
Logged

HS93 (RIP)

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 2,949
  • I cannot spell , tough
  • Location: Rainhill UK
Re: Prop shaft oilers
« Reply #22 on: August 12, 2011, 05:31:05 AM »

can you put a picture and a link or price , do you order by phone ? my supply dried up a few years ago so ill order a few.

thanks peter
Logged
Pages: [1]   Go Up