Tailwheel Spring attach bolt

gear1 · #1 08-19-2011, 04:31 PM

My relatively high-time RV8 (1175 hours) has developed some slop at the tailwheel spring attach bolt hole. To compensate I installed an NAS bolt (slightly bigger than AN), but this did not take out the slop. Is it acceptable to drill and ream the tailspring (FSTW-ASSY) and the tailspring mount (WD-409) to accomodate a 5/16" AN bolt? If so, are there any tricks to drilling out the tailspring to the 5/16" hole. Thanks for your help!

mannanj · #2 08-19-2011, 06:55 PM

I went to the hardware store and bought a 1/8th thick 5/8th wide by 36 in. long steel strap. I cut two pieces of the strap one inch longer than the fore/aft length of the rudder horn. I drilled them to fit the existing holes in the rudder horn with equal lengths of steel both fore and aft of the horn. I then drilled holes in the fore and aft ends of the steel to fit the rudder cables on the fore-end and the tailwheel springs on the aft. I then bolted everything together so that the wear points are in the steel strap. If the steel straps EVER wear out, simply make new ones.

You may have to make slight adjustments in the rudder pedals/cables and the tail wheel spring lengths.

Larco · #3 08-19-2011, 07:33 PM

If I understand correctly, the rudder horn hole is elongated you might consider one of these. Many RVs use them. Larry
http://www.aircraftspruce.com/catalo...s/eyebolts.php

gear1 · #4 08-19-2011, 09:10 PM

Thanks for your reply, Mannan and Larry. I apologize that I did not make it clear. The tailwheel spring that I am referring to is the "stinger" that inserts into the tubular weldment inside the lower rear fuselage, and is held at its most forward end by a 1/4" an bolt through the weldment tube and the "stinger." The tailwheel assembly is bolted to the rear end of the "stinger" by two 3/16" bolts. Any suggestions for drilling the "stinger" hole out to 5/16"?

Greg Arehart · #5 08-19-2011, 09:20 PM

Craig,

Before I would drill this out to accept a 5/16 bolt, I would consider reaming it for an NAS "X" (maybe you already did this and still have the slop) or the next step up NAS "Y" bolt. The X is 1/64 larger than standard size and the Y is 1/32 larger. GAHCO usually has these or can get them. I did similarly with my main gear legs because the standard hole was too sloppy. Reaming the holes may be interesting considering their location..... but I'm sure it can be done.

I don't know what the structural ramifications are (disclaimer: I'm not an engineer), but would expect that the X or Y would not be structurally a problem since most of the strength is in the tube ends that the stinger goes into and the hole appears largely to keep rotational movement from happening, or keep the stinger from pulling out the back.

cheers,
greg

gear1 · #6 08-20-2011, 07:28 AM

Gregg,

Thanks for the information. I had no idea that "X" and "Y" bolts existed! This sounds like the perfect solution. Now to find a 17/64" reamer.

Greg Arehart · #7 08-20-2011, 08:39 AM

Craig,

I advise against buying an adjustable reamer, as they are not robust enough. I suggest a chucking reamer (designed to chuck into a drill) that is a few thousandths smaller than the X or Y bolt you are using (diameters are posted on the GAHCO website). One can always use a bit of emery paper to decrease the bolt diameter slightly if necessary for a tight fit.

Note, the X bolts are not too bad but the Y ones are expensive. If you get an AN4 X or Y bolt, the threads are standard size, just the grip is larger diameter.

cheers,
greg

az_gila · #8 08-20-2011, 11:15 AM

Perhaps a tapered pin might be a better solution?

Get engineering approval from Vans first, but it sounds like your problem is similar to the loose nose gear leg attachment.

Lars · #9 08-21-2011, 09:58 PM

Somewhere on here are some threads about taper pins and corresponding reamers. A few locals had issues with the bolt loosening, and have gone to taper pins. I decided to head things off at the pass and reamed for the pin last weekend.

From Aircraft Spruce,
Pin: AN386-2-9A
Washer: AN975-3
Reamer:12-02704

Because I did the job with the tailwheel mount installed in the fuselage, I had to buy an extended tap handle to reach down into the tail. Got mine from McMaster-Carr, p/n 2546A27. There are some earlier threads that imply better prices elsewhere, but those are the best that I could find a couple of months ago.

vfrazier · #10 08-22-2011, 11:31 AM

The following came from Rocketbob years ago and has been on my website ever since:

I want to pass on a little tidbit here about the bolt that holds the tailwheel spring to the tailwheel weldment. I drilled mine per Mark's instructions and found that the bolt went in too easily--this should be an interference fit (once again, my savior the "big-***" hammer should be used to put the bolt in). I wrapped a piece of scrap aluminum around the tailwheel spring and could twist it with a pair of vise-grips. Not good! If there's any play here, the bolt can eventually fail or the hole will become elongated. I have heard of failures in these bolts on RV's . Rather than taking my chances with a larger bolt and it too not being correct, I decided to fix it with a taper pin which worked out very well. Here's the recipe:

AN386-2-9A taper pin (aircraft spruce)

AN975-3 taper pin washer (aircraft spruce)

B&S #2 taper pin reamer (http://www.mscdirect.com/MSCCatLooku...rodID=02054021) (1/2 the price of AC$)

12" long tap handle (http://www.harborfreight.com/cpi/cta...emnumber=45206)

The taper pin has the advantage that if the pin ever loosens up, you can just tighten up the nut and things should be snug again. The taper pin is an odd-sized Browne & Sharpe #2 taper, so don't confuse it with other -2 tapers.

I highly advise that the final hole size should be reamed with a hand-reamer .001-.002 under-size even if you don't use a taper-pin. There are too many variables with drilling to final size with a hand drill. Bob Japundza