SonexBuilders.net

I'm struggling trying to determine how to end up with the specified end play of .005" to .015" with the specified bearings and hardware.
The right side of SNX-C01 detail C shows a SF-812-3 which is 3/16" overall length (1/8" below the lip/ same thickness as the control triangle tab)
https://symmco.com/wp-content/uploads/P ... -812-3.pdf

Left side of detail shows a SF-812-4 which is 1/4" overall length, 3/16" below the lip, so 1/16" extension beyond the thickness of the control triangle tab.
https://symmco.com/wp-content/uploads/P ... -812-4.pdf

SNX-F16-03 shows 16 1/2" between the angles
SXN-C05-02 has 8 1/8" both sides for 16 1/4" overall between the tabs.
So that leaves a 1/4" gap.

The specified AN960-416 washer is ~1/16" thick

The hardware as shown should take up 1/8" of gap with the -4 bearing and the washer.
That leaves the assembly with an extra 1/8" gap that isn't taken up per the plan shown hardware.

How have people been installing this?
A.) Use (2) SF-812-4 bearings and an AN960-416 washer on both sides?
B.) Use the bearings specified and (3) washers?
C.) Use (2) SF-812-5 bearings and no washers?
D.) Something else?


Gregg Short
Burbank, OH
Sonex-A #715
N715SX (Reserved)

My A model Waiex plans don't quite match up so I am having a hard time visualizing this. I have put symmco bushings through a piece of scrap and sanded them down to shorten them. Not sure if that helps.

Here is a photo of the SNX-C01 Detail C. This is Rev B.

The plan snippet you attached says to machine the length of the bushing to get the play specified. So I think my guess was correct. Those bushings clamp up hard to the vertical aluminum angles and all rotation is between the control stick mount and the bushing. So use the hardware as called out, and shorten the bushing(s) as required.

Consider these thoughts. Each build is a little different based on the mounting of those aluminum angles. Can you bolt up the bushings directly to the angles without a washer between, or does that make the bushing shoulders bind on the weldment? If it binds you need a washer to make the distance between the shoulders a little less than the inside distance on the weldment, using a washer. When you push the weldment left and right does it bottom on the angles? If so you need to shorten the bushing so the left bushing shoulder stops contact on the right side by 2.5-7.5 thousands and visa versa. The plans show you means to get to the final requirement but not the absolute assembly.

Bryan,

You're looking at the issue the wrong way...I'm way too loose between the angles. I've got it temporarily installed with two of the SF-812-3 bearings (because I didn't have the longer SF-812-4 bearing), and 5 washers! Not counting the ones shown between the bearing and the nut (that would be 7).
But even if I use an SF-812-4 bearing, I'm going to still need (4) 1/16" thick washers, rather than the (1) shown in the diagram.

And I get the fitment issue and plans not showing all the washers, but this is beyond what I've experienced in the past with the plans. It's also pushing the limits on the standards for use of washers. And kind of a critical part!

But I can't be the only one seeing this issue...unless the plans were updated beyond B...but there's nothing in the change log.

I could guess that the drafter thought that the bearing length was measured from the underside of the bearing lip, rather than the overall length. That would amount to using an SF-812-4 and SF-812-5 and a single washer as drawn. That would work as drawn and make sense to need to trim down a bearing by a smidge.

I'm curious if the diagram on the Wyex plans is the same...

Gregg Short
Burbank, OH
Sonex-A #715
N715SX (Reserved)

Greg it's been a long time since I built mine but I think I took up the excess space between angles with AN washers.

As I understood it, the required play to worry about is on the port side and only to do with the bearing play on the A frame. That is where the A frame is sandwiched between the lip on the 3/16" long symco bearing and the AN washer. This is the only symco that should require trimming.

The starboard side of the A frame floats laterally on the 1/4" long symco bearing which is clamped to the Aluminium angle. Clearance on the starboard side is not so critical, ie, just enough to safely clear the aluminium.

All replies seem to be based on the assumption the tree's dimensions are correct.
It would be hard to screw up the angle's location because of the pre-punched holes in the spar tunnel and angles. Not that CNC presses are infallible.

If you are working with Sonex legacy prints, the overall dimension should be available.
Judges???

Greg, if you build per plans you do end up with an expected gap between the control stick assembly and the vertical angle on the right side looking forward. On my plans built Sonex and not wanting to end up with this gap, I added a bronze oil washer on each outer side of the control stick assembly along with additional AN960-416 washers needed to fill any remaining gap and to result in the desired side to side clearance.

Hope this helps from another prospective,

Art,,,,,,,,,,,,,Sonex taildragger #95,,,,,,,,,,,,Jabiru 3300 #261 (20th year flying)

Area 51:
Yeah, these are fairly old plans #715 and it's mostly plans built (including the control triangle) to the prints. I've triple checked the dimensions in the plans relative to what I made....

Art:
Thanks! I was kicking around the idea of using a oilite flat washer type bearing as the spacers. Good to know I'm not alone in this...

Gregg Short
Sonex N715SX