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[DieselDo]

The silicone is flexable so will allow the whole propshaft to move causing slight misalignment and yes vibration!!

[tight-lines]

think your right,,ive put a bit more expanding foam in aswell,,just for luck,,,problem is it took me 3 hours getting the foam out of one hull,and it wasnt all out then,now ive done it again in both,,,

and they say god loves a try'r ,,well hope he loves me this time bcos ,god knows ive try'd

[Seaspray]

Is it the stuff we use around the sinks n baths and never goes solid ?

[tight-lines]

yes the sink and bath ,sealent is called silicone,and thats what i have used,,in large amounts,shouldnt leak i hope

[Ghost in the shell]

personally i'd have used silicone grease or axle grease not bath silicone

[Colin Bishop]

I think he meant fixing the tubes in place Ghost, not lubricating them!

Colin

[tight-lines]

yeah fixing them in place,,,,,,i did use a silicone grease in the shafts,,,,,but a normal silicone sealent to seal,,,,,,

[tight-lines]

does rolling prop shafts down glass,,,show more problems with straightness,,,,,,,,instead of rolling down my kitchen worktop,,,

also do you check,roll,, the inner and outer shaft,on the glass,,,

[DickyD]

Your silicone will allow some movement of the prop shafts as it does not set solid.

[tonyH]

Hadn't noticed it in the above, but does the vibration reach a peak at certain revs. I.e. does it resonate? If this is the case, then having a double coupling or shortening the outer tube and refitting the bush can change the frequency out of the rev range.

Just a thought.

Tony

[Ghost in the shell]

I think he meant fixing the tubes in place Ghost, not lubricating them!

Colin

oh, !!

[tight-lines]

just tryed them again b4 i get some sleep,and i think the propshafts must be not straight enuff, ive got them sounding better,but they keep getting hot which must be where the slight kick in the steel rod must be rubbing on the oter shaft,,and no matter what i try,,when i get it good again it goes bad again,,,,think i might pay one of you lads,,,,to fix it if i cant get it to work soon ,,
is it normal to feel heat in the shaft?,,,

word of warning never get a plumber to make a boat

[Shipmate60]

If the shafts are lubricated they can get a little warm as the bearings bed in, but anything over a little warm does indicate a problem.

Bob

[Ghost in the shell]

... i think the propshafts must be not straight enuff, ive got them sounding better,but they keep getting hot which must be where the slight kick in the steel rod must be rubbing on the oter shaft...

as Adam savage (off Mythbusters) would say "There's your problem!!"

[sheerline]

Plumbers job: .. Keeping water in!
Boaters job:.....Keeping water out!
Shafts hould not get hot, definately something out of line or bent by the sound of things. Make sure the shaft bearings are not sloppy and the shaft can't wiggle sideways in the bearing. At high speed the shaft will wobble and oscillate like a good un and will not only make a hell of a noise but will soon deisplace the grease you put in
HHMMMM.... food for though... Keep at it mate, you're definately a try'er.

[tight-lines]

my propshafts,i dont think they have bearings in,,,they have a  4ml oil seal ,then on the main shaft ,they have a  smaller bore pipe insert,,,on each end,,which is the 4ml size,
so when people say bearing,do they mean the type that have the little roller bearings in,bcos mine just have the little pipe reducers to centre the inner shaft,

[DickyD]

Do your prop shafts have lock nuts on each end and are they too tight to the outer shaft. This can cause over heating.

[tight-lines]

they have a lock nut on one end,other end is held by the couplin conector,,but both of these are,,couplin about 10ml away from shaft,and blade nut not on,just the shaft sticking out,,,,

think im ready to admit defeat,,,but ive spent 400quid in bits,,,,im not a happy camper now,,,

could be the shafts are a bit out,,

im getting ready to see if theres anyone near preston i can pay to get them done of here,,,think ive made one of my motors change its noise pitch,so might of buggerd the bushes a bit too,all i need

[tight-lines]

ripped it all out again,,,not a happy chappy now,no way

[Shipmate60]

There are several known causes of the vibration you describe.
Starting from the aft end.

At 20000 are the props balanced to take those revs, you are getting in the realm of Fast Electrics.
Is the shaft straight and a good sliding fit in the bearings?
Is the shaft supported at the inner end?
Is the shaft held firm within the hull?
Is the inner coupling end close to the outer proptube, you only need a tiny bit of clearance.
Are the coupling ends bored central, there has been several instances of the ends being drilled off centre.
Is the coupling central?
If the shaft is firm you can use silicone but you have to line up the motor well and ensure that the shaft will not transmit any thrust to the motor.

Bob

[derekwarner]

tight-lines........I think we all understand your out of balance frustration   

Whilst there are 40 odd suggestions here.......my recommendation is to take your vessel to a model boat club meeting......explain your vibration issue to 'a listing ear'.........I am sure constructive comment  will follow......Derek

[tight-lines]

   At 20000 are the props balanced to take those revs, you are getting in the realm of Fast Electrics.

,,,running 12000 rpm,,about 10 at a guess in water,,

  Is the shaft straight and a good sliding fit in the bearings?

,,,little bit of sideways movement,,,rolled inner on a mirror,,,showed about 1ml out of its 10" length,,,,,so i would say at the 12000 rpm will be a problem,what would be nothing in terms of sound to a boat or springer at 4000rpm,,,bcos at 6v it doesnt vibrate half asmuch

   Is the shaft supported at the inner end?

well it was solid,,but i thaught bcos it was solid that i was getting the noise,so did it in silicone for a bit of movment,,to dampen the vibration,,.,,,but looking back now i was trying to solve a problem,that wasnt right,if you get me,,

   Is the shaft supported at the inner end? tried both

Is the shaft held firm within the hull? tried both

   Is the inner coupling end close to the outer proptube, you only need a tiny bit of clearance.

had it from tight to a inch away

   Are the coupling ends bored central, there has been several instances of the ends being drilled off centre.

yes

   Is the coupling central?

yes

   If the shaft is firm you can use silicone but you have to line up the motor well and ensure that the shaft will not transmit any thrust to the motor

,, right by your process of elimination,,,i think that the propshafts are out ,,,

i have had it in my hands set up ,out of the hull and running with no noise,,but it seems that the grease moves in the shaft after 2 mins of running,,which lets the metal vibrate again,,

think im going to buy two big motors and new shafts and run them at lower rpm,with big props,,if i cant fix it

[Ghost in the shell]

one thing i did with nord icelandia, was replace a double dog UJ with a piece of propshaft with two bits of silicone tubing on the ends.  went from growl and hum to a whisper

[Martin (Admin)]

Shouldn't worry to much till you've tried it in the water.

I have a Graupner motor in my coaster which on dry land makes heads turn,in the water lovely and quiet.

Hi tight-lines, have you tried the hull in the bath/water?

[tight-lines]

Shouldn't worry to much till you've tried it in the water.

I have a Graupner motor in my coaster which on dry land makes heads turn,in the water lovely and quiet.

Hi tight-lines, have you tried the hull in the bath/water?

no ive not been able to yet,bcos ive been to put off by the noise,,knowing even if it helped in water,,it would have to be holy water to total remove the problem noise ,,,

i think i know what it is,,are you ready bcos i dont think you will belive me,,and i promise this has took alot of messing to get to this conclusion?

its the motors,yep thats what i think,,its the speed 500e,

i think i might have a bad batch,seriously,,

i done all kinds of experiments,,
but if a hinged couplin cant spin on a flat work top,conected only with the grub screw at one end,,which is the motor end,,,and the other end is left to spin around the inner shaft im holding,,tight and level,,,

it must be the motor,,i also conected just the brass couplin insert on to the motor ,,tight to the motor,,and turned it by hand ,and it was tight ,then loose ,then tight etc etc,,

as if the spindle is a millionth out of line,,,

so when running the motor on its own,you cant tell,so at that stage you would think all is good
but as soon as anything is conected,,its vibration hell  !,,
at time of conecting things it can sometimes be made to go away ,moving angle of prop etc,but it could not be posible to fit it to such extremes,,bcos where ever it is held,,it soon finds its vibration in the body of the motor again and amplifies it,,

also  it could be that i dont have the natural skills to pull this off,,,,but i am usually good at making things