Engine Alignment

[doug748]

The previous post has motivated me to ask this one again.. I need to perfect the alignment on my engine, it woked fairly well this season but I would like it to be better (high revs make your teeth rattle). The conventional method is not possible because I have a plain shaft end and Centaflex coupling, ie nowhere to put feeler gauges. Anyone tried a dial gauge, if so how does it work?

 

[nedmin]

I have a Centaflex coupling, I split the coupling, fairly easy as there are threaded holes to put in the existing set screws,when you tighten these it splits the coupling. The hole that the prop shaft goes in is quite long, I adjusted the mounts so that the prop shaft was an easy fit right into the coupling. Tightened the set screws to correct settings with torque wrench.

 

[TigaWave]

With the centaflex coupling alignment is not critical, they are designed to have a great deal of angular movement so can cope easily with mis aligned shafts. A shaft that is balanced joined by a centaflex at an angle with an engine that is balanced will not cause vibration.

Your vibration is likely to be on the shaft end, if it has been vibrating it is likely to have worn the bearings. I suspect either inbalance in the shaft/prop assembly (bent shaft, bent or damaged prop blade, or worn bearings or both. Have you tried disconnecting the coupling and seeing if you have any movement in the shaft either as it rotates (sit a dial guage on the shaft surface) or by trying to move it in any axis perpendicular to the shaft.

 

[webcraft]

I second Nedmin's comments.

The easiest way to line up a shaft with a Centaflex coupling is to adjust the angle until the shaft slides into the coupling with a single click, rather than going clunk-click as it centres itself on the way in.

This was recommended to me by Steve Birch of VAGB when we re-engined our Vega, and it worked a treat. Pity I paid a 'professional' to misalign it for me first! /forums/images/graemlins/mad.gif

- Nick

 

[doug748]

I can se the misalignment as the shaft rotates and estimate it as 32thou (using an engineers surface gauge and feelers), it seems to be evident mainly at the engine end. The prop and shaft are good, the plain Tufnol bearing at the prop end has some play, but seems ok to me. The Contessa is known for the noisy transmission and I may replace the plain bearing with a cutlass and see what happens. I suspect the noise of my old engine used to mask the prop noise, but its a matter of subjective judgement ,how much is too much!
Thanks for the contributions, I will try the single click method as well.