Kasama Srimok Rotor Head for Trex600

Written by Rob Turnbull Tuesday, 04 November 2008 00:00

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Kasama Srimok Rotor Head for Trex600
Links, Washout and finishing off

Kasama have built up a good reputation for their high quality machined components. When I heard about the upgrade head for the Trex600, I had to find out more. Kasama then very kindly agreed to supply the head for review.

 

 

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Introduction

The first thing you notice when you open the parcel is the outstanding finish to the component parts. Everything looks stunning and, as will become apparent through the build, the machining tolerences are very tight making the end result really very good indeed.

The head arrives in four clear strong plastic bags which are all sealed together. Each bag has the component parts sealed off from each other for protection. Obviously the head requires assembly before it can be used, and at the time this one was received no real instructions existed - however, it isn't rocket science, so the build quickly got underway.

Here's some of pictures of the head as it arrived in the clear plastic bags.

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As the bags are not numbered, and seemingly spread out a little, here's a breakdown of what's in each bag looking at the top compartment of each bag and working down it.

Bag 1 contents: Fixings, damper mounts and damper rubbers, Feathering spindle, Head button (stopper), Head block

Bag 2 contents: Fixings, Blade grip levers, Blade grips

Bag 3 contents: Ball links and fixings, Washout base, Flybar carrier ends, Flybar levers, Flybar carrier (Seesaw)

Bag 4 contents: Links, Mixing arm fixing bolts, Mixing arms

Assembling the head

To assemble the head, you will need to re-use a few items from your stock Trex600 head, including the lower mixing arms attached to the washout base and the flybar and paddles. You also need to either re-use, or supply new, the missing rocket links - the supplied links all come with just one rocket link attached.

I found putting all the fixings together in a pile saved searching through each of the pockets of fixings for the item I needed. I just searched one big pile instead. Alternatively, you can just cut out the parts that you need to use as you need them through the build process.

So let's get straight into the build.

The washout base and mixing arms

Parts used:

• Washout base
• Existing washout arms from stock Trex600 head
• 2x M3x14 hex head bolts
• 2x Brass spacers

The first thing to assemble is the washout base and the mixing arms taken off the original Trex600 head. The bolts that attach the mixing arms to the head are provided, as are the brass spacers that sit between the mixing arms and the washout base. While the opportunity presents itself, check that the ball links on the mixing arms are in good condition and change them if they look worn.

Slide an M3x14 bolt through one of the mixing arms, add the brass spacer and then threadlock the bolt into the washout base.

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Note the orientation of the arms. The short side of the arm sits to the left of the squared off area of the washout base to which the arm attaches.

Assembling the blade grips

First, lets have a quick look at these lovely blade grips.

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They look great and are machined to incredible tolerences. In order to get the bearings out of the grips, you must heat the grip up - they will not pop out on their own!

Parts used in this stage of the assembly:

• Blade grips
• Blade grip levers
• Upper mixing arms
• 2x M3x4 hex head bolts
• 2x M3x8 hex head bolts
• 2x M3x14 hex head bolts

One 4mm bolt and one 8mm bolt are used to attach the blade grip lever to each blade grip. The longer bolt fits into the hole nearest the headblock and the shorter bolt fits nearer the blade. If you look at the threaded holes you can see the outer one is shallow than the inner one.

Push the bolts through the blade grip levers and threadlock them into the blade grips.

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With both blade grip levers threadlocked into place, we next need to fit the upper mixing arms to the blade grip levers.

No shims or spacers are needed between the upper mixing arms and the blade grip levers, or the mounting bolts as the blade grip lever is machined with the equivalent of a spacer on it (to avoid the bearing from getting jammed) and the bolt sits on the inner race edge so that the bearing can move freely.

Fit the 14mm bolt through the upper mixing arm from the side the ball links are fitted, so the ball links are facing out when fitted to the blade grip lever. Carefully add a little threadlock (do not get any threadlock in any bearings) and then fasten the bolt securely to the blade grip bolt. Repeat the same procedure for the second blade grip.

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Assembling the flybar seesaw and head block

Parts used in this stage of the assembly:

• Headblock
• Seesaw
• 2x mixing arms
• 2x red seesaw end caps
• 2x M3x7 hex head bolts
• 2x M2x4 grub screws

The seesaw is fitted to the headblock first, and then the remaining parts are fitted as you slide the flybar through the assembly.

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Slot the flybar seesaw into the headblock and line it up so that the centre mounting holes are positioned inline with the bearings in the side of the headblock. Add a little threadlock to the M3x7 bolts, carefully slide them through the bearings in the side of the headblock and fit them into the seesaw mounting holes. Tighten them up without overtightening, and then check that the seesaw moves completely freely in the headblock.

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Next we fit the flybar through the head and attach the right parts to the head in the right places as we push the flybar through, as follows.

First, fit one of the red seesaw ends loosely onto the flybar with the flat edge facing the seesaw then feed the flybar into the end of the seesaw. Hold one of the mixing arms in position (noting the correct orientation of the arm to the headblock) in the seesaw and push the flybar through it. Continue pushing the flybar through the headblock and then fit the second mixing arm (again, noting the arms orientation) before pushing the flybar through and out the other side of the seesaw. Fit the other red seesaw end onto the flybar with the flat edge facing the seesaw.

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The two flybar mixing arms are locked onto the flybar using grub screws, but the flybar must be centralised in the head first.

To try and make this job a little easier, what I do is nip up one of the grub screws in one of the red ends to just lightly pinch the flybar. Then I use a vernier (or calipers) to measure the distance from the outer edge of the red end to the end of the flybar, and get both sides exactly equal before tightening both of the grub screws down onto the flybar with threadlock.

With the flybar centralised, and with no horizontal play on the flybar, we can fix the flybar mixing arms in place. When correctly fitted, they are angled down by 10 degrees and this angle is important to ensure the head works properly. There's no need to panic though as setting the angle perfectly is a simple job. First, turn one arm so that it hits the bottom stop of its available rotation, centre the arm on the flybar in the seesaw slot and then tighten the grub screw down using threadlock. Then hold the first arm firmly in place (rotated down) and rotate the other arm fully upwards and tighten the grub screw in place using threadlock. The correct angle is now set on these mixing arms - simple!

We can finish the flybar part of this assembly now by fitting the paddles, making sure that they are equidistant from the centre of the head. Knowing that the flybar is perfectly central means that you can safely measure from the outside edge of the red seesaw ends to the inside edge of the paddle and know the distances are correct.

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Fitting the dampers

Parts used in this stage of the assembly:

• 2x damper collars
• 2x rubber dampers

This rotor head comes with its own damping sytem which involves rubber o-rings mounted onto a split metal collar which is then fitted into the head. The feathering spindle then slides through that collar and it's all a very close fit leaving a lovely slop free head. The rubber o-rings should be greased a little before fitting to the head.

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Fitting them is simply a case of pushing them into the headblock with the wider end of the collar facing outwards to help prevent the damper rubbers from coming out of the head block. The outside edge of the damper holders also acts as the spacer between the headblock and the blade grips.

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Fitting the feathering spindle

Parts used in this stage of the assembly:

• Feathering spindle
• 2x M4x8 bolts
• 2x special grip washers

This head uses its own completely flat 8mm feathering spindle.

Fit a bolt through one of the special grip washers, add a small amount of loctite to the bolt and then tightly fit it into the end of the feathering spindle.

Slide the feathering spindle through a blade grip starting from the blade side (not the head block side).

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Push the feathering spindle through the dampers in the headblock and fit the second blade grip to it on the other side. Fit the second bolt through the special grip washer and add a small amount of threadlock to it before carefully fitting it into the end of the feathering spindle (inside the blade grip) and then tightening it up.

You will need to use two hex drivers, one in each bolt in the ends of the feathering spindle, to tighten them up. Make sure there is no lateral play along the feathering spindle once completed - i.e. the blade grips cannot move, at all, along the feathering spindle. Zero play.

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