Kiwiprops™

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K3 Spring tension

 

This webpage is a sub-section of the web page covering replacement of a Nose Cone - which requires subsequent re-tensioning of the internal torsion spring:

 

Below is a summary of how to retension the internal spring which is tailed into the  the Nose Cone - Shaft or Saildrive. This may be needed to be undertaken if the Nose Cone has been moved - typically as the result of a rope wrap or the Nose Cone has been replaced.

Steps are as follows:

  • Locate the alignment marks punched on the boss - see last page of K3 Operating Manual.
  • Undo all 4 cap screws by two / three  turns - sufficient to loosen the Nose Cone on the boss.
  • Tap the head of each cap screw in turn to loosen the two halves of the Nose Cone on the boss.

Insert the Allen Key into the Saildrive nose and use as a lever to rotate the entire nose to re-align the marks as before. Spring tension should then be as before and it should take  ~ 1.5 kg or 3.5 lbs of force at the blade pin to start to tension the spring. Saildrives have a 6 mm hole at the leading edge to facilitate this - so insert  any non-flat nosed screwdriver and rotate.

For shaft nose cones insert the Allen Key into one of the cap screws and use as a lever to generate spring pre-tension. See last photo below.

 

Check the original alignment marks are now still in line as originally marked - or the new marks as shown in the photo's below for both Right and Left Handed units.

Holding it there - tighten up the 4 x screws evenly to pull the halves back together. This assumes the polyurethane joint material seal has been preserved. Simultaneously tap the nose cone aft to take out any excess wear tolerances in the assembly.

Nip up the 4 x screws - BUT DO NOT OVERTIGHTEN - it's tough - but still a composite. They must be tight enough for the nose to maintain it's position under the spring tension you have now loaded.  Final torque settings are 2 N.m for Saildrives and 2.5 N.m for Shaft drive style Nose Cones.

Tapping the blade carrier arms gently forward using a rubber hammer near the center can assist in adding tolerances / clearance to free up the assembly of it is binding.

Check the blade assembly will now rotate fully into the reverse position and return freely under spring tension to the sailing position where the blades are free to move fully through a fully feathered to engaged in an Ahead pitch position.

Grease the unit fully as per our web site video and your good to go.

The following photo's will show the correct position of the Nose Cones for both a Left and Right Handed K3 unit to enable a check as to the correct location of the Nose Cone joint line which will ensure the correct spring tension. Units are marked with pin punch marks post assembly - but these will not be there if a new nose cones is being fitted. If they can be transferred from an old nose cone - that would be of assistance.

Note that this join line on the Right Handed Shaft unit below is as shown relative to the heads of the Cap Screws. Ths opposite side will be in a different position.

Alternatively, assuming the unit was sitting on a flat surface nose up - then looking from the nose aft or down - you would initially rotate the nose, which holds the tail of the internal spring - so that it rotates the blade assembly that carries the blades into the motoring position.

In the motoring posiiton, the blades are free to rotate from touching the pitch stops as in motoring Ahead, to trailing aft as when Sailing, to ~ 25º past the due aft position to accommodate shaft angle.

RIGHT HANDED UNITS:

Right Handed  units have Left Handed springs that would screw in if rotated in a Left Handed or Anti-clockwise direction. Left Handed units therefore have Right Handed Springs.

So for a Right Handed unit ( with Left Handed spring ) - looking down onto the nose - you would initially rotate the nose in a Right Handed or Clockwise direction ( Viewed from above - relative to the boss ) - so as to initially wind up the spring such that it moves the blade assembly into the Ahead position until it reaches the internal stops on the drive dogs on the boss.

You would then rotate the nose further - maybe ~ 8 -10 mm at the diameter of the pitch stop casting and nose cone join line to provide the pre-tension required to ensure the blade assembly will always return to the feathered position. The nose cone joint should then be aligned as shown in the photo's as follows. [ NB: Ths will vary slighty by unit as spring tension will vary by batch, heat treatment ]

The photo below is of a RIGHT Handed Shaft unit - showing the joint line location of the Nose Cone relative to the Tripod casting such that the spring tension is correct for this spring. There may be slight variances between springs due to different material batches / tempering but the joint line will be very close to what is shown on this photo.

Note the position of the Cap Screws as the joint line on the other side will be in a different location relative to the Blade Carrier. This is because there are two joint lines but three tripod legs.

Moving the joint line towards the red mark will increase spring tension - towards the green will reduse spring tension.

The normal setting will be with the joint line at the blue mark on the centre of a leg.

Remember this is a Right Handed unit - Moving the joint line towards the green mark will reduce tension - towards  red will increase tension.


 

LEFT HANDED UNITS:

The photo below is of a LEFT Handed Saildrive unit - again showing the joint line location of the Nose Cone relative to the Tripod casting such that the spring tension is correct for this spring. There may be slight variances between springs due to different material batches / tempering but the joint line will be very close to what is shown on this photo.

Note the position of the Cap Screws as the joint line on the other side will be in a different location relative to the Blade Carrier. This is because there are two joint lines but three tripod legs.

Moving the  joint line closer to the Red mark will increase tension - Closer to the green mark will reduce tension.


 

Measuring spring tension of  1.5 kg or 3-4 lbs to start movement of Blade Carrier: