300C Assembly

I fitted the enormous Graupner motor after a bit of fiddling. In fact it went in and out 4 times before I managed to get the right sequence of assembly. Some instructions would have helped, but that's Vario, figure it out for yourself.

Then I put the chassis on the landing gear and fitted the now painted tailboom

In fact, I had painted everything which needed painting and here is the cabin loosely assembled to show you what it looks like. I took this photo without the flash as it washes the yellow right out when I take pictures with the flash on.

This is my target machine to model. There are a lot of 300c's painted in a similar manner in Europe and it seemed a nice bright scheme, but the big advantage is that I could paint each part with no masking off and assemble the parts all painted

With the help of my good friend Darrell Sprayberry, we got the cabin mounted up, and then I fitted the struts.

The rear fins needed a lot of fitting! Why I trusted Vario's built in recesses to be accurate I put down to naivete and lack of experience in building Vario stuff. Anyway, it patched up pretty well after I gouged the right shape and repainted it.

The different color tanks were fitted next. A bit of a fiddly job but I was learning and fitted the mounts to the cabin before I glued them to the tanks.

Motor, transmission and ESC

All the wiring has been arranged to come forward into the cabin, but I am not yet sure where I will mount the Rx and gyro box or the A123 Rx battery.

The HV servos in place and the tail rotor servo is set up after a lot of fiddling. A high power servo is needed here just to push the push rod and I have moved the ball links in on the lever to get less vertical travel on the rod as it goes from one extreme to the other. This reduces the binding and this the load on the Airtronics 94768 servo I used. I have reprogrammed the GY611 gyro to drive the wideband servo.

You will notice, the lack of mainshaft! When I ran it up, I got a lot of vibration so I removed it and checked it on a piece of glass. It is S shaped by about 1mm so I will be making my own. Vario's main shafts have a reputation of being soft and a 12mm shaft this thin is too much to risk unhardened

The new piece of hardened steel arrived today so I made a new main shaft. The only part I had problems with in making it was milling the flat for the set screw, so I used my trusty Dremel. This shaft is hard! That brought on further problems when I tried to insert it into the helicopter. It would not go through some of the bearings. I had to remove them all and take the bearings out of their respective holders. The mid bearing was simply too tight and the reason was a small burr on the inside of the bearing holder. I removed that and refitted the bearing and it was good. The bottom one on the mast housing was ok but the top one was way tight. I pushed it out and found that it was simply an undersized bearing so I replaced it with a new one from Boca which happened to be in the bottomless junk box. Then I could get the new main shaft through all the bearings. Fortunately the auto hub was a good fit. Then I ran the motor up to check the settings in the ESC. It asks for the number of poles of the motor and this information is not on Graupners web site. I asked Vario and they told me it was 12 pole, but when I did a simple test, that proved to be wrong, so I changed the number of poles to 14 and that was the correct number. The way to test this is on Graupners web site and it starts off by saying if you don't know the number of poles ask the motor manufacturer!

Then I progressed to the dummy drive belts. The instructions for this were all wrong! It took a few hours to figure it all out instead on the few minutes I anticipated but its done and looks ok, but I have never seen a 300C with the drive belts left exposed. There is no room to fit a scale cover and the fan protrudes too far to make it possible so I guess I will have to leave it like it is.

Then I fitted the push rods to the servos and swash plate. I used MA ball links as the Vario ones were very soft and flexible, I lost a heli on its maiden flight after a ball link came off and I did not want to repeat that experience.

Then I mounted the receiver and gyro box on a plate I had glued to the frames with PFM and tidied up the wiring. The battery will go in the cabin somewhere but I have yet to decide where to put the switch. The remote Rx will also go in the cabin somewhere.

The ESC mounts nicely in front of the frames in the fresh air and keeps the leads nice and short, and I have mounted the gyro away from strong magnetic fields at the back of the frames. l like that ESC and it's programmer. I bought a bunch of them while the Euro was way down and got them for about $200 each for the 100 Amp versions.

Today I mounted the rotor head and set the pitches. I use a digital pitch gauge and set all three blades within 0.3 of a degree. I found some old Vario Ball links which are about 3 times as thick as the ones which came with the kit although the ones for the head were missing!

While I was checking the head, I noticed that the tail rotor was going backwards! I checked the drawings and the inside of the box and I had assembled it according to the instructions, so I had to take it all apart and reassemble it with the driven gear at the other end. Nothing quite like building a Vario gear box twice.

That's not the only thing I did twice, but the other thing was my fault. I made the electronics panel too wide and had to tear it off and cut it down to size.

The inside of the cabin has a nice back panel molded which covers everything up

I had rough cut a hole to clear the panel and the electronics in the back so everything would be hidden. The idea is to make this panel removable easily with magnets or velcro. Once it is tidied up I will be able to fit it to the inside of the cabin but first I must make a battery holder while I have the heli on the bench. I want the batteries to sit under the chassis.

I found some 8000mAH batteries which were the same height as the 6S ones but as they are 4S they are narrower. However, it allowed me to do a lot of work on the battery tray and here is how it turned out.

The height from the bottom of the chassis to the underside of the landing gear is perfect, well it is now I have removed all the bolts, countersunk the holes and fitted countersunk screws to give the chassis a flat bottom

I cut the mounting plate for the electronics down even further and ran the wires very close in to the gyro box

That filled in this morning and this afternoon I spent with a pair of scissors, trimming the windows. The material Vario are using is new to me, its very soft and difficult to work with but it is crystal clear. If only their molded cut marks were more accurate. Anyway 5 hours later I slid the cabin on the frames and dropped the seat back panel in place

It's getting there. I cant permanently fit the cabin until I have checked the batteries fit and they should be here tomorrow. Then I have to fabricate some means of stopping them coming out in flight but allowing me to get them out easily to charge them up. Meanwhile I have the cockpit to paint and assemble and then I am in the home stretch.

Tomorrow came and went with no batteries so I did some detail work, but they did arrive the next day. They were too big to go in the place I wanted them, so I made up a CF plate and a drop bar to lower the plate so the batteries could slide in easily. Then I made another bar to stop them coming out the other side and a small bar to stop them coming out the back. Still haven't figured out how to hold them in and make changing them easy but that's the next job

I made up a switch plate to fit behind the cabin for easy access. The switch is a bit difficult to see being black on black in the sunlight

I did fit the Vario instrument panel just to fill in the hole but the 3D printer is going to get fired up soon and a proper panel will be made

So, it's finished Vario style. A lot more to do to detail it but here it is in all its glory

It was a nice calm day, so I figured I would try and set the headspeed while I had it outside. I set it at 1120 with my MA tach, and then I tried to lift off, but I had no rudder. I had checked everything before going out so I know it did work, but when I got it back inside I found the servo fried. I fitted a new one and found the problem. The servo travel was just a tad too great and was pushing the pitch arm past its limit. No problem normally but with a fresh battery giving lots of power, the gyro in HH mode and me messing around with the headspeed for too long, the servo had slowly moved over to the stop and cooked itself.

The new servo was set so that it had much lower travel and was in non HH mode and out I went again. I upped the ESC setting to 75% from 60% to get more headspeed and tached it at 1329 rpm. Later I checked the readout from the ESC and it said I was running a true headspeed of 869rpm. I love that ESC. The heli flew nicely but I did not have enough rudder. With the motor not running I could get massive throw but once it was running the setup did not have enough power to drive it very far. I rebuilt the linkage to get more mechanical leverage and my next flight should be better. Hopefully I will have video then.

Wind stopped a flight so it wasn't worth making a video of a hover, but things were not much better. I spoke to Joe about it and after considerable thought his light bulb turned on. He had spotted that the full size turned the "wrong" way and so I had reversed Varios correct gearbox and caused myself all these problems. I rebuilt the gearbox the way the instructions showed, flipped the blades and then hovered the heli. It hovered with no rudder trim and the pitch slider in the middle! What a dork I felt! OK, so now I could paint the tail rotor blades and add the aluminum leading edge.

It will be interesting to see how many people tell me I have the tail going the wrong way

Scale details