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chevell's blog
Posted by chevell | Jun 17, 2011 @ 04:08 PM | 903,146 Views
I've decided to dedicate a blog section to the tail vibration problem for obvious reasons.

Getting these tails vibration free seems to be one of those things that many of us have problems with, including yours truely. It also seems to be an inherent problem with these small Heli's in general. Part of the reason is that the tail blades are spinning 3.4 times faster than the main roter. So if the mainblades are going 4000 RPM's the tail blades are at 13,600 RPM's.

You know how the tail fin buzzes back and forth and it's difficult to hold onto without it buzzing your fingers off? If your lucky you don't have this problem "very unlikely" or it's not very bad "mild buzzing" that is about where I'm at now. Dynamic balancing helps but doesn't get rid of the tail buzzing completely.

This was recently referred too as the holy grail of small heli fixes. You can tune out part of the problem by dynamically balancing the blades using clear tape but I think there is more to the problem than this.

I believe a major part of the problem is that the bearings do not fit snug enough into the plastic bearing retainer's which tend to stretch out over time. Using higher quality precision bearings should also help.

Ideally the bearing retainer should be C/Aed into position and held firm so it can't vibrate or move at all.

After looking closely at what happens to the outside part of the bearing while running the heli I realized that the bearing retainer &...Continue Reading
Posted by chevell | Apr 21, 2011 @ 10:40 AM | 901,304 Views
I just completed this set screw mod on the heliworx head.

First picture is Heliworx head being drilled with #50 size drill for 2/56 stainless set screws.

Second picture shows the tapping process. The hole needs to be drilled perfectly straight and you have to be sure and tap the hole straight as well.

Third picture shows me spinning the head up to speed after I spent some time getting this mainshaft straight again. I have a procedure for this using a block of hardwood in my vise. This one is using the shorter 48mm mainshaft. I straightend the mainshaft for free in this case.

Forth picture shows a side by side comparison of my head next to the Heliworx head, not much difference between the two. They perform the same task but I made mine for 2.50$ in parts.

This mod makes it much easier to remove the head. It also eliminates the use of the pin which can be a real pain to remove. That is why this head was sent to me in the first place. I had to get the pin out first which was not easy, seemed to be stuck in there a bit.

I can do this mod for 12 dollars plus shipping. You couldn't do this mod yourself for less because the drill and taps plus the 2/56 set screws plus shipping would cost you more than that. Not to mention the machine work plus the precision and expertise required. I am in fact the one who originally came up with this idea of using set screws in place of the pin.

This is a very worth while mod because everytime you bend the mainshaft you will most likely need to remove the mainshaft to replace it or get it straight again. Dealing with that pin everytime is a royal PITA and tends to slowly beat up your nice expensive Heliworx head.

If you have a Heliworx head this is the mod you want.
Posted by chevell | Apr 05, 2011 @ 04:55 PM | 905,205 Views
Today were going to talk about the proper use of thrust bearings for the Xtreme framed V120's.

In case nobody was aware nearly all larger heli's use a combination of radial bearings and thrust bearings in the head support. There are plenty of good reasons for this besides the fact that it's the mechanically correct method for reducing friction on a helicopter head.

I decided that the el cheapo chinese radial bearings that my Xtreme frame came with weren't doing the best possible job of reducing friction. This was evidenced with the fact that if I over tightend the collar just a hair it would bind the radial bearings up big time. It made no difference if the tail gear was on or not so this wasn't caused by a gear mesh problem.

This apparent binding due to side axial loading a radial bearing is what happens everytime you use pitch in either direction. Placing high axial loads on radial bearings is mechanically incorrect, IMO this can lead to premature bearing ware and lots extra friction.

This isn't something you want on a micro heli that has very limited battery and motor power. As a result of using incorrect bearings you can expect to see wasted power with reduced run times, premature motor and bearing ware, unsmooth operation, increased bogging during pitch manuvers, and higher temps of both the battery and the motor will occur.

Luckily the Xtreme frame was designed to use both radial bearings and a thrust bearing at each end of the head support. It was...Continue Reading
Posted by chevell | Mar 03, 2011 @ 02:02 PM | 902,252 Views
Chev's FBL head and custom mainshaft

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Seeing as how I'm a do it yourself kinda guy I figured I would try my hand at making a custom mainshaft and my own version of the FBL head.

Using materials I purchased from Mcmaster Carr I was able to make these parts fairly inexpensively.

I'll start with the mainshaft which is a 5/64's precision polished rod made of A2 tool steel costing 2.69$ for 36" so cost per unit minus labor and tools is 19 cents each. The diameter is .0006" larger than the stock mainshaft so it fits with absolutely zero play going through the swash and bearings. This mainshaft runs smoother than the stock one and I'm very pleased with how it turned out.

I drilled the holes using a #61 .039" drill. I simply stacked the old mainshaft on top of the new one using tape to hold them together, this allowed me to use the holes as a guide and to keep the drill from wandering. You have to make sure the holes are exactly straight and perpendicular before you clamp them tightly into the vise. My mainshaft is also hardend and tempered which turnes it blue.

To make the mainshaft even better I drilled and tapped the original Walkera head using a #50 .070" drill, drilling right through where the pin was. I used some 1/16" long 2/56 cone tip set screws to hold the head on, the tips of the set screws go right into where the pin was and hold it very securly....Continue Reading
Posted by chevell | Feb 21, 2011 @ 11:47 AM | 902,200 Views
The first mod I would like to add is how to get the ESC's heat away from the Rx which is known to cause gyro drifting problems. This problem has been around for quite sometime and is a definate Walkera blunder. In fact I've had 4 other people complain about this same problem so far. Here is another thread about this problem at Helifreak. > http://helifreak.com/showthread.php?t=280821

I even had Walkera replace my Rx thinking that it was the problem when in fact the heat from the ESC was causing the gyro's to drift in an uncontrolled mannor a few minutes into the run. Pretty much everyone with the ESC mounted to the side of the 2610V Rx needs to do this.

The second mod is to the Xtreme landing gear which was way too squishy in my opinion, especially when you squeezed them from the sides. I added some .030" carbon struts and held them in place with some shrink tubing. This makes the landing gear much stiffer and stronger while still allowing the landing gear to flex at the mid point. I still need to test this one out more but so far it's good and only adds minimal weight.

The third mod "picture 3" is my canopy mount, I just didn't like the thin carbon rod they were using so I made a thicker mounting rod from the carbon tail shaft. I used thin carbon .015" for the carbon rod mount and shrink tubing to hold it all in place. You can see where I used the screws on the Xtreme frame to hold the mount on. It's very strong and light this way.

...Continue Reading