How to measure propshaft for bend?

[wragges]

Hi All,

Can anyone recommend a method (without buying expensive kit) to check / measure for any bend in a propshaft (conventional type with P-bracket).

Thanks,

 

[rusailing]

Hi, may be stating the obvious, but if you could remove the shaft then a quick roll acoss a glass coffee table or up against the house windows(!?!) would show up any reasonable bends down it's entire length. Otherwise, disconnecting your drive coupling and turning the shaft by hand could perhaps show up any tight spots through the 360 deg turns indicating a bend inbetween the stern gland an the P bracket.

After that, you may need to consider a DTI (dial test indicator - cheap enough to buy and easy to use) which can be placed in various positions along the shaft to measure any 'out of round' conditions. A good engineering shop will perhaps lend you one. The only problem you will have will be that they are almost exclusively designed to mount to steel by magnetism and i would guess your boat may be GRP or wood if you were lucky!

Have a search on google - somewhere like machine mart will have cheap versions.

Good luck, R

 

[PCUK]

As above use a DTI. Easy enough to mount remotely if the boat is GRP.

 

[savageseadog]

You can have dynamic bending which you can't measure statically of course

 

[rogerthebodger]

Depends how accurate you wich to measuer the static bend.

This is how I have done it in the past.

!) get 2 trestles/ stands and setup level and parallel with the distance between then half length of shaft

2) place shaft on trestles and allow to roll so bend is at bottom (gravity will do this).

3) get a straight edge the length of the shaft and hold on top of shaft.

4) measure gap under straight at center with feeler gauge.

If you with more accurate measurement get a dial indicator and attach to stright edge across trestles and roll shaft 180 degrees and take start / end readings of dial indicator difference is half the total bend (if trestles positioned half shaft length