Pekola Tail wheel //Stinger Drilling on Super STOL

For general discussion of the Just Aircraft family of aircraft.
Includes: Highlander, Escapade, Summit and SuperSTOL.

Moderator: scubarider2

Pekola Tail wheel //Stinger Drilling on Super STOL

Postby The Flying Hare » Wed Dec 30, 2015 3:02 am

So there I was...... contemplating all the ways to drill the bolt holes in the Aluminum rod to secure the Pekola tail wheel to the stinger. I have particular interest in the proper mounting of this, as I was in the right seat during the first known failure of the SINGLE BOLT original design installation on John Levy's Super STOL in New Zealand last year. At first glance is seemed easy.....drill it, bolt it together and on to the next thing.......But WAIT!!!, there is more to doing this then I first thought. There is the rotational alignment, the depth of the stinger, the stress loading vs bolt hole location, orientation of hole, (horizontal vs vertical) and the clincher......how to do all this keeping the holes true to the existing holes in the Pekola mount, and harder yet, drilling through the 7075 rod and coming out on the other side, in the exact center of the other hole, keeping all the variables in check, and likely not being to clamp the entire assembly in a mill or drill press, and then consuming just enough booze to numb the fear of failure, but have a sufficient enough amount on hand to deal with the shame and sorrow when (not if) something messes up and the parts make the undesirable metamorphosis from valuable aircraft parts to "shittium"!!!
So there I sat.....contemplating the "What If's" and the "How To's".... nothing was easy, do-able, or possible..... I called out to Jim Pekola, since he is the Master of this tail wheel, but he didn't have any sure fire method, or good suggestions. Sampling the Booze and retiring to the boob tube started looking like a better solution, but then it all came together.....No TV, No Booze, No Shame and No Shittium!!!

I had some Toggle clamps that I got from Boeing Surplus years ago, back when they were still open. (These are available on Amazon now, search De-sta-co #463, about 36 bucks, you need 2) They have two 3/8 diameter threaded clamp pads, that I removed and replaced with some custom parts made out of threaded rod stock. One was center drilled with a Letter "D" bit to .246", one had a chamfered step that was .250" in Diameter. The other 2 have the .250 step but also have a shallow cone shaped tip.
I added 2 jam nuts on the Drill guide to prevent any wiggle.

Forum1.jpg

Forum2.jpg
Forum2.jpg (34.6 KiB) Viewed 1766 times

So heres how it goes......
1. Level the head rack tubes with a calibrated digital level.
2. Shove the tailwheel assembly on the stinger, WITH THE LOCK PIN IN IT"S DETENT, I put two 7/8 Diameter washers down inside the tube to act as a spacer at the rod end. (These do come out later)
3. Remove the tail wheel from the axle, and re-install the axle on the yolk.
4. Using a true block of wood or ? you can place the SAME level used in step 1 on the block, now the tailwheel yolk is rotationally adjusted so the axle is perfectly level with the head rack.
5. Use the clamp with the cone tips with decent pre-set tension, to clamp through the aft holes on the tail wheel tube into the 1" aluminum rod.
THIS LOCKS THE TAIL WHEEL IN ROTATION AND POSITION
6. Re-check the rotational alignment with the head rack, recheck the axle level, adjust if not matched to the head rack..... loosening the clamp and re-setting it as needed.
forum3.jpg
forum3.jpg (36.49 KiB) Viewed 1766 times

7. When all checks, Clamp the second clamp with the drill guide in the front hole. I used a Letter "D" bit in my 18 volt Dewalt drill, and some cutting lube. With the drill guide, the cuttings have no where to go, so the drill needs to be pulled out and cleaned frequently.
I set my drill bit in the chuck so that when the chuck touches the drill guide the tip of the drill is not quite touching the opposite alignment pin, so when you drill, the chuck bottoms out drill guide BEFORE the drill destroys the alignment pin. Then the last few thousands are done without the guide.
8. I drilled the other direction with the Letter "D" and then I used a .250 to ream it to the final size
9. I installed an AN4 bolt to keep the alignment in the new hole and then repeat with the drill guide clamp in the second hole.

My holes came out perfectly in the middle of the hole on the opposite side without "wallering" out the hole in the tube. With even a slightly wallered out hole, I think the shear potential is higher.

Does anyone have any input on using a NAS 6604-21 instead of the AN4 as the plans call for. The NAS6604 have a much higher shear strength...... Spruce sells them for $1.14 each, so its not a big deal......

Thought also needs to be given when drilling the second (additional) bolt to the swing arm. My swing arm had the single bolt already drilled horizontally 1.5" from the end of the tube. I am looking for input as to where to drill the second hole. I only have 7/8" from the center of the single hole to the end of the aluminum rod, inside the tube. I was considering drilling vertically approx. 1/2" above (towards the shock attach) from the existing hole, possibly using a NAS shear bolt.

Contact me off line if you need specifics or want to borrow the Jigs.

Chris Hare
Conroe TX
Super STOL N3OUT (in and out)
The Flying Hare
New Member
 
Posts: 9
Joined: Sun Mar 08, 2015 9:40 pm

Re: Pekola Tail wheel //Stinger Drilling on Super STOL

Postby Johnny C! » Wed Dec 30, 2015 1:39 pm

Wow!

That went from easy to complicated
& back to easy, real quick.

Good job!

John
There are many things that happen really fast when you are
flying an airplane. There is no sense in rushing any of the others.

I would much rather be looking down at the runway, than up at it.

Duane Sorenson & Rick Norton Gone West 6/8/09. Godspeed
User avatar
Johnny C!
Veteran Member
 
Posts: 820
Joined: Thu Sep 07, 2006 9:55 am
Location: Brevard, NC

Re: Pekola Tail wheel //Stinger Drilling on Super STOL

Postby john2 » Wed Dec 30, 2015 10:24 pm

So there I was...... contemplating all the ways to drill the bolt holes in the Aluminum rod to secure the Pekola tail wheel to the stinger. I have particular interest in the proper mounting of this, as I was in the right seat during the first known failure of the SINGLE BOLT original design installation on John Levy's Super STOL in New Zealand last year


Can you elaborate on this a little bit? Have there been other failures? Did it shear the head off from twisting force? If this is indeed a problem why not use a hardened bolt or maybe go to single 5/16" hardened bolt? I'm just thinking out loud as I'm 7k miles from home right now.
Take Care,
John Cooley
Kit #265 converted to SuperSTOL
N265JC reserved
User avatar
john2
Veteran Member
 
Posts: 189
Joined: Sat Mar 05, 2011 11:42 am
Location: Lucedale, Ms.

Re: Pekola Tail wheel //Stinger Drilling on Super STOL

Postby The Flying Hare » Thu Dec 31, 2015 11:00 am

[quote]Can you elaborate on this a little bit? Have there been other failures? Did it shear the head off from twisting force? If this is indeed a problem why not use a hardened bolt or maybe go to single 5/16" hardened bolt? I'm just thinking out loud as I'm 7k miles from home right now./quote]

I am not sure of any other failures, though I am no official spokesman. That said, the aforementioned event took place in November 2014 while landing at George River, on the South west shore of New Zealand's South Island.

George River.jpg


An easy 1200 ft strip at sea level. The approach and flare were very normal (not a STOL Smack Down landing). Being a friend of Levy for 30 years, I would just love to publicly throw him under the bus for making crappy landing, but I was there, and that wasn't the case. Immediately after touchdown, I noticed my view over the cowl was a significantly different sight picture form normal, I had limited forward visibility. (this increase in pitch was due to the tail wheel being twisted) John called out that he had no steering, and the plane veered off the runway into the bushes.

nz tail wheel.JPG
nz tail wheel.JPG (40.45 KiB) Viewed 1620 times


Luckily, there was no damage to the plane, as we were a 2 day walk from the nearest paved road.
The single tailwheel bolt on the aft side of the 1" aluminum rod had sheared. This translates to shearing 2 AN4 bolts at the same time, because the bolt goes through the stinger, effectively twice.
The bolt was replaced with another AN4 that I cannibalized from the seatbelt tang to cable assembly, (on John's side of course!!!) and that bolt was temporarily replaced with a non-aircraft bolt we scrounged from the eclectic guy that lives there.
All checked out, and good and we flew several more hours that day.
Later back at Johns house, we reconfigured the seatbelt bolt, and inspected the forward rod attach bolt, IT TOO WAS VISIBLY BENT.
I cant recall what the holes looked like, ie: if they were wallered, but in thinking about it, if the holes wern't wallered, I would not have been able to take a bent bolt out of a semi-close tolerance hole.
The additional holes were later drilled according to John.

As a side note, John does fold his wings every time he puts the plane to bed. There is an opinion that the additional weight on the tail with the wings folded, and the tail wheel swiveling through 90 degrees and bouncing along the floor, caused the excessive twist loading on the bolts, and caused the bolts to stress

I am going to use the NAS6604 bolts on mine.....and not worry about it

The story of the tail wheel failure, pictures and other happenings of the trip were detailed in an article that I wrote for [url]http://www.stolaircraftmagazine.com//url]


All the Best.....


Chris
The Flying Hare
New Member
 
Posts: 9
Joined: Sun Mar 08, 2015 9:40 pm


Return to Just Aircraft