Swift Kit Build

Introduction

The Swift comes as an almost ready to fly kit. Now it also comes as a build it yourself kit. The kit version does not contain an ESC, motor or battery, it is purely a kit as you would expect of any other heli manufacturer.

The article that follows is a build of the kit version of the swift to the point that it is essentially a built airframe. I have already written other articles for the site showing what to do next to install servos, radio and so forth and will not re-cover old ground.

Box contents

So, let's open the box. As can be seen below everything is nice and neatly packaged. All of the various components for the build are in their own separate plastic bags. Century has attempted to keep together all of the various parts related to each build step in the manual.

Blade Grips

The first task is to build the rotor head so without further delay let's get started. The swift has blade grips with double radial bearings and one thrust race. One radial bearing inserts into the blade grip facing the rotor hub, the other bearing inserts down through the blade grip and seats inside the blade grip. This second bearing has to be pushed down quite forcefully in order to seat correctly. Once the radial bearings are in place the thrust race is the final bearing which also seats down through the blade grip and a single bolt holds the whole thing onto the feathering spindle. The thrust race should be liberally lubricated with a silicon based grease.

The swift blade grip also contains the upper mixing arms. These mixing arms have a double radial bearing inside them with a brass spacer in the middle to hold the two bearings apart.

Care should be taken when screwing the mixer arm to the blade grip as if you overtighten then the mixer arm will bind. It should be extremely free moving with no binding at all.

No glues or loctite compounds should be required in this build step.

Rotor hub

The next step is building up the rotor head. This is essentially the installation of the flybar carrier and its seesaw. Followed by installation of the feathering spindle and finally bolting the blade grips onto the head block.

Firstly the flybar carrier needs to be built up and installed into the rotor hub. This is fairly simple and just requires some bearings inserting into the flybar carrier and also into the rotor hub. The pictures below show all the required detail in building up the flybar carrier. Note that the screws that go into the rotor hub are there to hold the bearing in place and do not require excessive tightening.

Installing the feathering spindle at face value does appear very straightforward, however, there are some things to be aware of when installing the feathering spindle. It is well documented that some swifts have a vibration or shake during spool up, this was mostly due to the undercarriage on early models being too flexible but it was also down to the feathering spindle being too tight in the rotor head. I wrote an article explicitly on how to fix vibration and at this stage in the build it is worthwhile checking this article and making sure that your feathering spindle fits correctly in the rotor head.

Once you have checked this you can go ahead and install the feathering spindle, insert the brass spacers and finally bolt the blade grips to the feathering spindle. Make sure that you use loctite on the blade grip bolts but take care to only use a modest amount as excessive amounts will get into the bearings.

Flybar, swashplate and mixers

Installing the flybar is a straightforward affair but care must be taken to make sure that the flybar is centered. What I mean by this is that the same amount of flybar rod emerges from either side of the flybar seesaw. You should center the flybar before fitting the flybar paddles. I use a vernier to perform this measurement so that I can get it within 1 mm difference.

The flybar control arms are used to hold the flybar in place, a grub screw locates onto a flat on the flybar so make sure that you have rotated the flybar such that when the grub screws tightened it does actually meet with the flat on the flybar. Don't forget to put the little plastic spacer between the flybar control arm and the seesaw hub bearing, also remember to put loctite on the grub screws.

Once the flybar is nicely centered the flybar paddles can be installed. Again care should be taken that the flybar paddles are screwed exactly the same amount onto the flybar so that the distance between the flybar control arm and a paddle is exactly the same on each side of the flybar.

The flybar paddles do not come with the covering installed and this must be done using the provided black stickers.

Once the flybar is completed the main shaft can be inserted into the rotor head and then the washout arms and swashplate can be installed onto the main shaft. The main shaft is bolted onto the rotor head using the supplied Jesus bolt and nyloc nut.

Main Frames

The swift mainframes are held together by the main shaft bearing blocks, motor mount and the front battery tray. Also worthy of note is that the swift kit contains the new mainframes that have been made stiffer to stop frame flex. Building the main frames is a simple case of bolting the bearing block, motor mount and front battery tray to one side of the main frames, then bolting the other side on to that. The screws provided to do this are self tapping cross head screws. Therefore care should be taken not to overtighten as you will strip the plastic threads.

Don't forget to put the anti rotation bracket in place before bolting the frames up, although with a bit of frame bending / stretching this can be added later if you forget.

Once the frames are together the upper bearing block bearing can be pressed into place. Following this there is some more work to do installing the four canopy mounts. Lastly the bellcranks for the servos can be installed onto the main frames. These have two bearings in them each with a brass spacer in the middle to keep the two bearings apart. When bolting the bellcranks onto the main frames once again take care not to overtighten as you will cause binding. The bellcranks should rotate effortlessly.

When installing the motor mount loctite should be used on the screws and nuts as these are not the nyloc variety and will come undone from vibration if loctite is not used.

Main Gear and main shaft

Installing the main gear involves also installing the main shaft into the main frames. First the main shaft locking collar needs to be put onto the main shaft underneath the swashplate. The main gear can now be inserted through the slot in the frames and pushed up into the motor mount where there is a hole for it to locate into. Now gently holding the main gear in place insert the main shaft down through the upper bearing block and through the main gear. Having done this the main shaft should now be protruding from the bottom of the main gear.

Turn the frames upside down so it is easier to do this next bit. Onto the protruding main shaft place the spacer washer followed by the main gear locking collar. Rotate the locking collar on the shaft until the holes in the bottom of the shaft and the locking collar line up. Now insert the bolt and tighten up the supplied nyloc nut.

We are almost done, the last thing to do is to secure the main shaft locking collar. Turn the frames the right way up and suspend the whole machine from the rotor head. What we want to do now is to make sure that the main gear is pulled up nicely into the motor mount and at the same time push the locking collar down onto the top of the main shaft bearing (in the upper bearing block). With the whole thing in tension the locking collar grub screws should be tightened. Make sure that loctite is used on the grub screws. The idea of this procedure being that the main shaft now does not have any vertical play and is held securely in place.

Tail Rotor

The tail pitch slider comes preassembled so no work is required on this particular part. The tail rotor blade grips need to be built and this consists of installing the bearings into the blade grips. Don't forget to put the supplied brass spacer in between the two radial bearings in each blade grip.

Once the blade grips have been built they can be bolted onto the tail rotor hub. Loctite should be used on the screws that insert through the blade grips into the tail rotor hub. Also take care not to overtighten the tail rotor blade grip bolts as this can cause the blade grips to not rotate freely on the hub. If you detect any binding then release the screw a little until the binding disappears. Also try not to use too much loctite on these screws as it will get into the bearings and cause problems later in flight.

Once the hub and grips have been built they can be secured onto the tail rotor shaft using the supplied grub screw. Once again loctite should be used and take care to make sure that the grub screw locates into the indentation in the tail rotor shaft.

With the tail rotor hub now secured in place push the tail pitch slider onto the tail rotor shaft and connect the ball links onto the tail blade grips.

Tail gearbox and pitch slider

The tail gearbox encases the tail rotor shaft but before the shaft can be inserted the tail drive pinion must be installed. The tail drive pinion is a white gear which is pushed onto the tail rotor shaft and lined up with the small hole through the shaft. A small metal pin is then inserted through the drive pinion and through the tail shaft effectively holding the whole thing in place. Care must be taken to make sure that the pin is flush against the pinion gear and not sticking out as it will damage the tail drive belt. Once the pinion has been installed the bearings can be inserted into the two halves of the tail gearbox and the gearbox closed around the tail shaft.

Bear in mind that at this point we have not installed the tail drive belt and the gearbox will need to be split open in order for the drive belt to go round the pinion gear.

Also in this step we need to build the control arm for the tail pitch slider. This is a matter of inserting a couple of bearings and then screwing the control horn onto the tail gearbox. The control horn has a cup in it that the tail pitch slider ball inserts into. This is a very tight fit and requires a considerable amount of pressure in order to get the ball to click into the cup. As in previous steps don't forget to put the brass spacer in the middle of the two bearings that insert into the control horn.

Tail rotor, front gearbox and boom

Finishing the tail rotor is a matter of installing the tail blades. The tail blades on the swift turn anticlockwise and should be fitted as shown below.

Now is a good time to install the tail servo holders and also the horizontal fin clamp and fin onto the tail boom as you won't be able to do this after the next steps.

The next part of the build is more complicated than the pictures below would lead you to believe. Essentially the following build steps are to install the tail drive belt between the front and rear pinions. Obviously this means also fitting the tail boom. Starting with the front gearbox the bearings are installed into the gear and the gear installed onto the supplied shaft. Don't forget to fit the small washers on either side of the gear so that when it inserts into the front gearbox it doesn't blind against the plastic. When putting together the front pulley the belt should be installed at the same time as you cannot fit the belt later on without splitting open the front gearbox.

Once the front gearbox is loosely screwed together the belt should be pulled down the tail boom and then the bolts on the front gearbox tightened just enough to hold the gearbox in place on the boom. The tail gearbox should also be fitted and the belt put around the tail shaft pinion (yes you will have to split open the gearbox to do this). There should only be a quarter turn on the belt when running between the front and rear pinions.

It is at this point that you set the belt tension. Pull the front gearbox forward to tension the belt and once you have the correct tension tighten the bolts that hold the front gearbox onto the boom. Once done the belt should be held properly in tension and the tail rotor should spin relatively freely.

 

Finished tail gearbox

The tail rotor gearbox is held in place by a single bolt that goes through the vertical fin, through the tail boom and into a nyloc nut. The single bolt goes right through the boom effectively holding the tail gearbox in place. At this point the screws and nuts holding the tail gearbox together can be fully tightened.

The boom and it's front gearbox can now be bolted into the back of the main frames.

Undercarriage

At this point we have a set of main frames completed and a tail boom complete with tail rotor installed into the back of the frames. We now need to install the battery tray and undercarriage, we also need to fit the boom supports. The undercarriage is held in place by four bolts and their respective nuts. These bolts go through the undercarriage, through the undercarriage spacers, through the carbon fibre battery tray and into the bottom of the main frames. The undercarriage spacers are there to raise up the back of the frames to keep the tail rotor clear of the ground.

Finished kit

Having installed the undercarriage and tail boom supports effectively the kit build is completed. I have written a build guide and setup article for the almost ready to fly swift kit, this can now be referenced to complete the build.

Below are some pictures of the finished kit build.