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Tuesday, 05 February 2008 17:36 |
So the question is, is the Blitz Avro worth the $1,500 price tag (double the price of say a Align Trex 700)? That is the question I intend to try to answer during my build log.
Well to start with the Avro arrived from England in 3 days and even before I saw any parts I was already impressed! The kit was extremely well packaged, first there was an outer box made of double walled cardboard, inside that was another thin single walled cardboard box both sealed with tape and glue. Finally inside that was the actual Blitz Avro kit box.
Inside the kit box, was you guessed it two more boxes with the main components in one and the canopy and frames in the other. These in turn were packed with more bubble wrap and cardboard.
There are two manuals, one covering the build and the other covering all the various setup options.
So far very impressed!
Stay tuned for the start of the build, in the meantime I am trying to decide on a painter for the canopy which is fiberglass and very well molded.
So the build has now started in earnest. I have not yet decided on all the components that I will use on the Avro, but I am using a YS 91 SR engine and have also ordered a MultiGov Pro governor which also includes a mixture control function similar to the CSM SmartCarb, but built into the governor which saves on space and extra wire.
So above is the YS 91 SR engine that will be going into my Blitz Avro. This will be the first time I have used a YS engine, but I have heard lots of good things about it. The only downside so far has been how difficult it has been to find one as they are in very short supply.
These are the first components to be assembled, the clutch and cooling fan.
The kit comes with components for both the OS and YS engines and in this particular stage it comes with two engine crankshaft nuts (the siilver colored threaded component above). The othe interesting thing is that the starter goes into the socket (the black threaded component) which screws (left hand thread) into the engine crankshaft nut.
The Avro has a large diameter small-fin cooling fan which combined with a high-flow shroud, is designed for optimum airflow.
The other nice feature is the self-aligning clutch and cooling fan which is made possible by the use of an upper and lower collet and a machine cut engine crankshaft nut. This eliminates the need to dial-indicate the assembly.
Here you can see the clutch and cooling fan attached to the YS91SR engine.
Next step is to assemble the auto hub with the main gear, crown gear lower bearing housing.
Again the kit comes with two main gears, a 42 and 43 tooth so you can choose your ratio depending on the engine you are using.
The gears are made of really well machined delrin and all the aluminium parts are extremely well CNC machined to an amazing level of detail and quality beyond anything I have seen in any other helicopter kit.
The auto hub uses sprag bearings rather than the normal roller bearings found in most helicopter kits so I expect no hub lock ups.
The other thing that is nice about the kit is that each build stage has a numbered bag the relates back to the stage number in the manual and contains just the parts required for that sub-assembly, so no searhing through bags for the righ parts as is the case with many kits.
and here is the completed auto hub, main gear and crown gear assembly.
Next the pinion gear/ drive pulley assembly.
Again the pinion is very well made as you can see.
Here is a close up of the pinion sub-assembly.
and finally the completed pinion drive assembly.
Next up will be the fuel tank.
again some nice components.
Here is the clunk assembly ready to be installed into the tank.
On the left is the main mast top bearing and the right is the starter guide.
So today I had an email from Blitz keeping me up to date on the Avro and the fact that they are about to introduce extra shims for the engine mount in addition to the one supplied, to fine tune the belt tension and as soon as they have received them they will forward a set to me as part of our customer support - very impressive!
This is the rear boom clamp and tail transfer bell crank.
and the bevel pinion gear assembly.
The above photo shows some of the components installed on the left hand main frame along with the tank strap and seal.
The belt you see is part of the two-stage transmission, consisting of drive belt and helical machine cut gears. This minimises resonance and delivers a smooth transition throughout the power band.
Above is the elevator linkgage assembly and collective shaft. This is part of a substantial collective assembly that rotates about a common centre as you will see later on in the build. The geometry of the design will ensure symmetry throughout the control range. The collective shaft is 5mm and the elevator A-link is supported on 4mm bearings.
Here it is assembled ready to be installed in the frame.
The above image shows both sides of the frames assembled.
Here is another nice Blitz touch, the main shaft comes in a protective sheath to protect it.
The drive pulley assembly, crown gear and main gear assemblies are all inserted into the frames from the right hand side. This is a very nice piece of design where the right hand frame has cutouts in it to allow the insertion after the frames are assembled and then covered with side plates or access panels as you will see in the next image.
This of course means that even after the Blitz Avro is fully assembled, the complete drive assembly can still be removed in minutes from the single stacked main frame, by the removal of the access panels.
These are the access panels. The top three pieces cover the access slots in the right hand frame that are used to insert and remove the drive train and the lower piece then goes on top to tie it all into the main right hand frame.
This is the undercarriage assembly.
Here is the undercarriage assembly attached to the main frame.
The interesting thing to note here is that unlike many nitro helicopters I have built the engine has still not be added to the frame.
The engine mount is pictured here, again a great piece of machining. Below the hole you can see on the nearest finned side you may notice a 3mm tapped hole, this is for mounting a header tank if you want to.
Shims are added between the engine mount if you are using the 42 tooth main gear. Blitz are sending out additional shims to allow more fine tuning of the drive belt tension.
The engine is inserted sideways through the frame and attached by four bolts.
Insertion and removal of the engine is really simple making maintenance very easy.
Here is a closeup of the YS 91 installed in the main frame.
Above is the Avro's swash plate. There are three set screws around the swash that can be used to pre-load the bearing.
The washout arm / link. This is the first of a few steps where you can adjust the assembly depending on the type of flying you want to do. In this case I put the control balls on the inner holes for stable flight.
These are the components for the main rotor hub and flybar carrier.
and here it is assembled.
The next step is to assemble the head cradle and add it to the main rotor hub. The kit also comes with a pair of white inserts for more aggresive 3D flight.
Finally, here is the head craddle assembled with the main rotor hub. Very different construction method to the normal one piece units found in other helicopters and again a great piece of art!
The next step is to assemble the main blade grips. Depending on the style of flying your want the helicopter to perform, you can setup the blade grips differently. The order of assembly of the radial bearing, shims and thrust race is different for stable flying and sport/3D and you can set the grips up for leading or trailing edge control.
and here is one assembled and ready to be mounted onto the feathering spindle.
as in the previous steps, again when assembling the blade grips onto the feathering spindle there is an option for different flying styles. For stable flying you use a 60 and 90 O-rings on each side and for 3D you use a 70 and 90.
These are the mixing arms and again depending on the flying style you ount the control balls in diferent holes.
Here are the mixing arms assembled onto the head and yet again there are options as to which holes you use on the main blade grip arms depending on flying style.
These are the flybar arms components,
and here they are assembled onto the head with the flybar also added.
These are the two torque tube bearing supports. Each one gets two o-rings which hold the torque tube in place in the tail boom.
Above is the tail boom (aluminium not carbon), the torque tube and the cross drive adaptors that will be held in place with epoxy and a socket head bolt and nyloc nut.
One end of the torque tube showing one of the cross drive adaptors and torque tube bearing support and bearing in place.
The bevel gear crss drive and tail rotor shaft assemblies for the Avro are shown above prior to installation in the gear case.
These are the two halves of the tails gear case.
The bevel gear cross drive and tail rotor shaft assembly installed in the left hand half of the tail gear case.
The collar you can see on the tail rotor shaft is used to adjust any end float out between the tail gearbox shaft bearings and is done through an access hole once the right hand side of the gearbox case is added.
Here the tail gearbox had been assembled onto the tail boom (with torque tube drive inside).
The two red plugs are removeable to access the gears inside, the nearest one being used to access the grup screws on the collar to adjust end float as mentioned previously.
This is the tail pitch control assembly.
and the tail pitch control bellcrank all ready to be assembled onto the tail.
Here is the canopy in it's unfinished state. It's now gone of to my painter.
Above you can see the tail blade grip and tail rotot hub components for Blitz Avro. You will notice that it has full bearings and thrust races.
and here is the tail blade grips and rotor hub assembled. Above the tail assembly you can see the special socket driver that is provided with the kit for reaching down inside the tail blade grips to tighten the nylock nuts that hold the grips to the tail rotor hubs.
Here you can see the tail rotor blade grips and hub assembled onto the tail rotor shaft along with the tail pitch boss and control bell crank.
This is the horizontal tail fin and mount shown upside down.
Today I had another example of Blitz first class service. Another small unexpected package from them saying that
"on a recent packing check I (they) noticed that the collective spacers for stage 34-1 may have been missed from your (my) kit. As a precaution I (they) have sent you (me) a replacement".
Now that's what I call service, I have not even got to that stage yet.
Above are some of the components for the Avro boom support.
These are the collective bellcranks (pitch, aileron and elevator) along with the collective collar.
Above is a series of three shots showing the current build stage of the Blitz Avro.
You can see the tail boom supports now added along with the collective bellcranks and control links.
I think that these are the thickest control rods I have seen used on a helicopter at 3mm which compares with 2.5mm on my Airstar Mongoose and JetCopter.
I have now ordered three JR DS8717 ultra high speed cyclic servos which should arrive soon.
Here are the main components for the servo support system. The system is designed to fully support the servo output shaft, while isolating the servo from resonance and vibration emmirws through the main frame.
This is the pitch servo mounted in the support sytem on the main frame.
and this show the pitch servo connected to the pitch bellcrank via the control arm.
It's been a few days since I last posted an update to the build, but don't worry I have not stopped work!
I ordered (and now received) a Reactor-X regulator (http://www.scottgrayrc.com/ReactorX.html) which I will be running at 6.8v for the cyclic servos. I have also ordered Radix 710mm main blades and 105mm tail blades, SAB 25g flybar paddles and a Hatori SB-19 muffler which is made specifically for the YS-91 long stroke engine that I am using.
There are no new pictures as there is not much of interest to photograph, just lots of wires everywhere at present as I figure out optimum positioning of the various components.
Here you can see the Avro on my worktable while I am wiring everything up and doing final assemblies.
The rotor head is now fully assembled along with the various links.
For those that have asked about the current state of the build, the Avro is pretty much complete and I am just waiting for the canopy to come back from the painter so I can finalize the position of the receiver.
Here are a series of pictures of the completed Avro with the exception of fixing the receiver in place and adding the battery.
The cannopy is now back from CanopyFX after painting and I am very pleased with the results.
Okay so after 5 successful test flights with the only issue being loosing the magnets for the governor twice, I had a crash caused by the tail loosing grip on the tail shaft.
I am not sure exactly what happened, especially as I checked the two grub screws before the flight. All I can think is that I did not have the "niples" that are on the ends of the grub screws engaged with the holes in the shaft and by checking the tightness before the flight I broke the lock on the locktight which allowed one of them to back out slightly during the flight.
The good news is that even though I was about 30 feet up, I manged to bring the Avro down with throttle hold on and did a relatively small amount of damage. The undercarriage struts took most of the impact and there strength I think prevented more damage than there was, even the main blades were fine.
In total there was about $300 worth of parts I am replacing, of which $100 was the canopy which although not damaged very badly I decided I want to replace.
The rebuilt Avro will have a couple of changes, firstly I will be adding a rear canopy piece which is available from Blitz which streamlines the Avro. Both the front and rear canopies have gone of to CanopyFX to be painted.
The second change is that I have replaced the Multigov Pro governor sensor with the Spektrum governor sensor that is mounted on the crankcase cover and uses the crankcase to measure the rotation of the engine.
Mounting is very easy and from bench tests it appears to work fine.
I have to say that this crash shows how strong this helicopter is and also how easy it is to repair. The cost of the replacement parts is very reasonable, for example a feathering bar is $13.50 (mine turned out not to be bent) and the service and speed of delivery from Blitz in the UK to the USA was great.
Expect new pictures in a few weeks when the canopies are back for the painter.
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