RV6 tail wheel mount

[Glenncfly]

Let me start off by saying that I am not a builder. I bought this airplane 6 years ago from the original builder. I’ve noticed the tail wheel wearing on one side and upon closer inspection found that the hole in the mount has worn and the spring is actually rotating inside the mount. Do any of you guys have a recommendation for a fix? I’ve had aircraft mechanics recommend drilling the mount and putting a hat bushing on both sides but I’m thinking replacing the entire assembly.

 

[blaplante]

A couple thoughts - taper ream and install an AN386 taper pin. Replace the whole tailspring (just did this for a client). Challenge is to get the new tailrspring drill to match your mount. Did a lot of measuring of the original spring and drilled the new one on a mill. Note that most likely your spring isn't from Vans, but rather from
Aviation Products
(805) 646-6042
[email protected]
They'll have the proper replacement tire as well.

Carefully note that the spring comes long, and you cut off the big end to fit. Original builder on clien'ts plane cut the small tapered end, which then wouldn't fit the pivot assembly, so then tapered down the tip, which made a loose fit into the pivot. One day the spring fractured at the pivot bolt hole) and the tailwheel dropped off.

Personally I'd look at the taper pin first. I can make you a deal on a new B&S #2 taper pin reamer.

 

[BlakeFrazier]

We've got a document concerning the process involved with match drilling the tail spring to a new one here: (link)

Of course, it all depends on where the wear is. If the actual mount is worn or drilled improperly from the beginning, that's a bit of a different animal, and not a small job to replace the weldment.

 

[Glenncfly]

We've got a document concerning the process involved with match drilling the tail spring to a new one here: (link)

Of course, it all depends on where the wear is. If the actual mount is worn or drilled improperly from the beginning, that's a bit of a different animal, and not a small job to replace the weldment.

We've got a document concerning the process involved with match drilling the tail spring to a new one here: (link)

Of course, it all depends on where the wear is. If the actual mount is worn or drilled improperly from the beginning, that's a bit of a different animal, and not a small job to replace the weldment.

Yes, the wear is on the mount, not the spring. The bolt is solid inside the spring. I have a video of it but don’t know how to upload from my phone. I’m thinking the hole in the mount was not drilled properly and over the years has gotten worse.

 

[blaplante]

Yes, the wear is on the mount, not the spring. The bolt is solid inside the spring. I have a video of it but don’t know how to upload from my phone. I’m thinking the hole in the mount was not drilled properly and over the years has gotten worse.

How much wear in the mount? If measuring the amount of slop is a problem, maybe tell us how much fore/aft or rotation the tailspring makes. If it's not *too much* then the taper pin is going to be the easiest solution. Grossly oversizing the hole to up a bolt size is not a good idea.

As noted above, extracting the mount from a completed fuselage is a big undertaking.

 

[auj4]

I replaced the original bent spring and non castering tailwheel with a new Flyboy Accessories spring and lightweight castering tailwheel.

I made an aluminium block to clamp around the old spring and match drilled the block to the old spring by drilling one half of the block through the old spring and then keeping the spring and first half of the block aligned, drilled back through the other half of the aluminium block.

I then clamped the block around the new spring and used it to transfer the holes to the new spring. I drilled halfway through the spring diameter from each side so my entry and exit holes were correct.

Because I used a drill press my alignment wasn’t perfect, but this was taken care of by the taper ream.

To drill the spring I used an expensive cobalt drill - keeping the drill cutting is key.

Google photo album here:
https://photos.app.goo.gl/QG5zQoFmWextxw4K6

Don H
Sydney, Aus

 

[Glenncfly]

How much wear in the mount? If measuring the amount of slop is a problem, maybe tell us how much fore/aft or rotation the tailspring makes. If it's not *too much* then the taper pin is going to be the easiest solution. Grossly oversizing the hole to up a bolt size is not a good idea.

As noted above, extracting the mount from a completed fuselage is a big undertaking.

 

[blaplante]

Well that looks like about 1/4 of the bolt diameter of movement. I am pretty sure that's an AN4 size bolt? Don't remember for sure. So we have 1/16" of play. An AN386-9A taper pin is about 0.29" at the big end, so it isn't going to fill this 5/16" (0.3125) hole. [Happen to have one laying here]

The usual solutions (all complicated by where it is...):

• remove/replace the mount
• weld up the hole & re-drill the mount (somehow not wrecking the ID) ... not a good option
• weld on a patch / washer and ream to fit. would be the go-to but it'll take a talented welder to do a reasonable job from either the top or the bottom.
• go to a longer taper pin - AN386-12 should do from what I can tell.

Note on the taper pin - I'm assuming, from the movement, that both top and bottom holes are worn equally. The taper pin will only take up the slop on one side, so now the twisting force is only restrained by one of the mount holes. But, if all the slop is stopped, hopefully the wear will be radically slowed.

 

[bjdecker]

The taper pin/bolt is one good suggestion.

However, you may find that putting in a fresh AN4-14A bolt but with an AN960-416 washer under the bolt head and an AN960-416 washer under the nut, and change the nut to an MS21042-4 or MS21045-4 and torque to the top end of the scale, will tighten things up enough. Adjust the tire/tailspring to the preferred position before tightening everything up.