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New tailwheel stinger

RedRaider94

Active Member
I have a 1500 hour RV7 that I did not build nor do I have any experience building one. I am going to put a new tail wheel assembly on to replace the stock vans assembly but noticed my current spring/stinger is definitely not as straight as it was when original. The angle of the tailwheel is a little swept back at this point and would like to have the correct geometry when putting the new tailwheel parts on and to save the bottom of my rudder (I have about 2” - 2.5” from the top of the main nut to the rudder).

Question is, how hard is it to actually change out the spring and can the bolts be accessed sufficiently from the outside of the plane through the access panels on each side? I suppose you can order this heat treated rod from Van’s and if so, any idea how expensive they are?

Thanks for any thoughts - much appreciated!
 
It isn't dreadfully difficult and you should have bolt access through a hole beneath the tailcone.

Blake has undrilled springs, important to get a good match on the mounting bolt, at www.flyboyaccessories.com Blake also has a free tech sheet for tail wheel maintenance that discusses replacing the spring.
 
New tail wheel stinger

Based on info here on VAF, I bought a Harbor Freight 12 ton pipe bender and straightened mine. Actually put a tiny bit of reverse bend on it and replaced the bolts while I had it out and cleaned up. Works great now.
I now have an almost new bender for sale. Used only once. Price is so cheap, though, it is not worth the freight cost to ship it.
 
Had not thought of trying to bed it and what that might do to the hardness of the steel.

Has it held up well and not quickly returned to its old form after bending? Also, did you just bend until it was straight or had just a slight reverse bend in it?

I have to believe I can find a machine shop to do that for me relatively cheap vs buying one for one time use.

Most importantly, I thought this bar was tempered steel to begin with and my concern would be not only does it need to be bent but it would need new heat treating to perform correctly for any reasonable amount of time. I figured the bending process would negatively affect the tempering process.
 
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Based on info here on VAF, I bought a Harbor Freight 12 ton pipe bender and straightened mine. Actually put a tiny bit of reverse bend on it and replaced the bolts while I had it out and cleaned up. Works great now.
I now have an almost new bender for sale. Used only once. Price is so cheap, though, it is not worth the freight cost to ship it.

I did the same thing to my -7, after 350 hrs or so and a lot of soft field operations I developed a tailwheel shimmey. My tailwheel vertical axis had developed about a 15° bend. Flyboys' has a great post on tailwheel geometry and the importance of maintaining a vertical plane on tailwheel mounting. I added a little reverse bend to allow for tailwheel loading. Problem solved!
https://i.postimg.cc/8kKb16HW/20200628-144130.jpg
https://i.postimg.cc/B6tCrTzm/20200628-162354.jpg
 
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Thanks Jake - that is what I was wondering. It sound like the bending process itself has no impact on the original tempering process or makes the spring materially weaker based on your experience. Bending alone is enough the fix the problem?
 
When you do make the bend do it in gradually in a 4"-5" area in the middle of the spring. Be sure the spring is bent true to its vertical. Be careful, easy to over bend.
Good luck!
 
Thanks Jake - that is what I was wondering. It sound like the bending process itself has no impact on the original tempering process or makes the spring materially weaker based on your experience. Bending alone is enough the fix the problem?

Hardening or annealing of alloy steel requires high heat and a specific cooling process. Generally speaking, It does not work harden or work soften.
 
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I had another thought - if it is not a great idea please don’t be bashful. If the stinger is slightly warped in the wrong direction, is there any remote possibility that it was originally drilled (the hole in the mounting tube and the actual tail wheel connection) pretty symmetrical where I could remove the stinger and turn it over and replace? It seems logical to me that there might be a chance but my logic doesn’t always work out as intended.
 
It seems like turning it around should work if it’s not bent too much, considering you have a standard yoke with two AN3 bolts holding the yoke/fork assembly on. You’ll need to make sure the tail wheel assembly is straight, though. To do this, make sure the airplane is level laterally with a long level across the longerons. If not level, let some air out of one of the tires to level it. Then bolt on your yoke/fork assembly. Put a level on the side of the fork and make sure it is level vertically. You can do this with the tail up on a stand because you are squaring the tail wheel assembly with the longerons. If your AN3 bolts are slightly loose, you can buy a couple close tolerance bolts from aircraft spruce to see if that snugs them up a bit. This of course all depends on how true these holes were drilled originally, but seems like it might be worth a try and fairly easy to check.
 
I found that the holes were drilled in my RV7 stinger were slightly off center so there was no way to just flip it. The 12 ton Harbor Freight hydraulic bender worked just great. Isn’t fair to return it after using it, but I still haven’ t figured out what to do with it now. It weighs 62 lbs with the one size pipe die for the stinger. Double that with all the other size dies it came with. Looking forward to making something else with bent pipe. Maybe a tool hangar for the hangar....
 
I had another thought - if it is not a great idea please don’t be bashful. If the stinger is slightly warped in the wrong direction, is there any remote possibility that it was originally drilled (the hole in the mounting tube and the actual tail wheel connection) pretty symmetrical where I could remove the stinger and turn it over and replace? It seems logical to me that there might be a chance but my logic doesn’t always work out as intended.

I know of an RV builder who did exactly this and it worked like a charm. He's been flying for years since doing it with no problems at all, YMMV!
 
Greg,

I wish you lived closer to Texas and we could put the pipe bender to use for a second time :)

Ok, I’m going to figure out how to pull it off (will be praying all week the original builder drilled a hole for access) this weekend and give it a shot at flipping over. If it doesn’t work, will try to find a machine shop close by that can bend it.
 
Just a quick update that this was far easier than I thought. Getting the spring out was real easy and it did have a slight bend to it. I flipped it over and to my amazement, the front hole was drilled perfectly true. I flipped it and the match drilled the new tail wheel housing to the two aft holes and the whole unit is perfectly level. Put a Doug Bell fork on and new wheel. Should be good to go and anyone thinking about flipping the spring - it worked like a charm.
 
New Rod

Does anyone make a substitute tailwheel rod for RVs maybe made from Titanium to save a little weight.
 
There is, but it's astronomically expensive and only 1lb lighter. Sky Designs sells it. Still waiting for my money tree to start producing. :D
 
mr.sun

Maybe, mr.sun ,, Greg,,, would bend your tail spring for you? . Since he has already invested in the press.
Greg you might recoup some of your investment if you bent a few tail springs for us?

I am curious about your screen name,, mr.sun. And your location,,, Wet west Washington???
Did you used to live in Arizona?
 
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Our 10 year old stinger was suffering from a bit of sag.

The knuckle was also a little wobbly, so we just overhauled it.

Had it cold bent down by 5° and put taper bolts through the original bolt holes.

Also, if you have issues with getting the nut on the bottom due to proximity of the weldment, use one of the new all metal lighter nuts currently supplied by Vans. A size down on the wrench which gives easy clearance.
 
Our 10 year old stinger was suffering from a bit of sag.

The knuckle was also a little wobbly, so we just overhauled it.

Had it cold bent down by 5° and put taper bolts through the original bolt holes.

Also, if you have issues with getting the nut on the bottom due to proximity of the weldment, use one of the new all metal lighter nuts currently supplied by Vans. A size down on the wrench which gives easy clearance.
Mike, did you notice a difference in handling after bending the "stinger"?
 
I suppose I could bend a few more but seems not worth the hassle. The thread I had found here described over bending it slightly to get the bend desired.

I used a magnetic angle tool set for 12 degrees, then it reflexes back to 8 degrees. I ended up with just the right amount to make the tail wheel fork pivot axis just about vertical. It has stayed the same for me but my landings have improved so not banging the tail much anymore.

I could not flip mine over because the holes were slightly different. Perhaps re-drilling for a taper pin would work out. I didn’t do that. Just replaced the bolts.

As far as my screen name, I have been doing Solar Power for over 30 years. Not getting rich but love my job and I can buy Avgas.
 
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