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  #1  
Old 08-10-2015, 01:38 AM
riobison riobison is offline
 
Join Date: Jul 2011
Location: Oliver BC & Red Deer Alberta Canada
Posts: 308
Default Options for a higher breakout force on tail wheel?

Gents,

I'm looking to replace my Vans Tail wheel fork with something that will take a little more force to unlock it).

As well as NOT raise the rear of my RV4 any higher than what it is. (Its the shorter gear version of the RV4 that I have)

I could possible put a longer spring in with the key might help but a slightly different design might be better.

Any suggestions?

Thanks
Tim
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  #2  
Old 08-10-2015, 05:27 AM
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ccsmith51 ccsmith51 is offline
 
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Is it possible that your existing locking key is worn? I recently had the situation where my tailwheel would lock to the right but not to the left. I removed the key and spring attach arm and both were worn. I replaced the key and turned the arm upside down and got back to very strong locking force.
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  #3  
Old 08-10-2015, 08:50 AM
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Ironflight Ironflight is offline
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Location: Dayton, NV
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This is very common when the slot in the arm gets worn - check it carefully to see if the edge of the "U" slot is rounded or sharp - they aren't very costly to replace. Temporarily, you might be able to flip the arm over - they generally wear asymmetrically (top to bottom).
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  #4  
Old 08-10-2015, 10:02 AM
riobison riobison is offline
 
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Location: Oliver BC & Red Deer Alberta Canada
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Default So my lesson from this is

Hello Chris and Paul

I have it apart again and looking at it and its still clean, the key and spring looks good , the arm does show a little wear so it needs to be changed for sure. On the mounting socket the brass bushing needs to be replaced as the tail wheel fork has a tiny bit of play in there when its bolted together. As well there is a small bit of movement where it bolts onto the stinger.

I have the Vans set up on my RV4 with 600 hrs on it. It appears to be stock except for the tire that I put on a 100 hrs ago.

The wheel locks and releases as normal. But when I think about it, the wheel has not taken as much brake these days to unlock it to swing it around.

On Saturday when doing a cross wind landing with a lot of gusts to 25 knots with an average of 45 to 60 degs off the run way heading I could keep it straight until I slowed down and let my tail down. As soon as the tail touched the plane immediately weather vaned into the wind and off the run way and into the Alf alpha on the side of the runway. (no damage) I know my cross wind component was around 20 knots or maybe even more with the gusts. But the little wheel felt to me as well as my girl friend riding shot gun in the back that it had unlocked as soon as it started taking a load. I had full rudder and then got some brake on it as well but there was no changing its course. The skids marks are still there from the braking and the tire locking and letting go on the pavement, through the gravel and into the alp alpha.

So my lesson from this is that there is more than sufficient rudder while doing the approach and side slipping in and during the touchdown.

But when the plane gets slowed down and the tail is coming down there is not enough rudder with or without the brake to keep it straight at least on my RV4 especially if the little guy comes unlocked.

So I need to restore the little wheel to like new or better.

And above all not tackle anything much over 15 knots direct cross wind component. Next time I might not be so lucky.

Do any of the aftermarket set ups offer a higher breakout force? Or is the factory one sufficient when its like new? I could possibly add a little longer spring to put a little more tension on the pin. That would be another option.

Thanks
Tim
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  #5  
Old 08-10-2015, 10:20 AM
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Russ McCutcheon Russ McCutcheon is offline
 
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“force” is not what is intended to release the key from the steering arm, I think all the manufactures use the same method, the key climbs a ramp inside the yoke as the fork is deflected, the ramp pushes the key back disengaging it from the steering arm, if the fork has not been deflected sufficiently to cause the key to be pushed out of the steering arm then it should not disengage regardless what the force is, if it is disengaging without being deflected then the arm or key or both are worn out
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  #6  
Old 08-10-2015, 10:48 AM
rvbuilder2002 rvbuilder2002 is offline
 
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Location: Hubbard Oregon
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What material is your steering arm made out of?

The early ones were made out of aluminum and didn't hold up well (corners of notch got rounded off as described by Paul).

It was changed to being made out of steel about 15 years ago.
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  #7  
Old 08-10-2015, 10:51 AM
rvbuilder2002 rvbuilder2002 is offline
 
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Quote:
Originally Posted by Russ McCutcheon View Post
“force” is not what is intended to release the key from the steering arm, I think all the manufactures use the same method, the key climbs a ramp inside the yoke as the fork is deflected, the ramp pushes the key back disengaging it from the steering arm, if the fork has not been deflected sufficiently to cause the key to be pushed out of the steering arm then it should not disengage regardless what the force is, if it is disengaging without being deflected then the arm or key or both are worn out
Russ is correct, but if the notch in the arm begins to get worn, the tail wheel will start to release at a smaller deflection angle than is intended, because the ramp is no longer needed for it to happen.
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  #8  
Old 08-10-2015, 10:58 AM
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MarkW MarkW is offline
 
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Just to address one comment you have made twice, I would not use a longer spring. Stiffer maybe but longer may prevent the key from retracting all the way.
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  #9  
Old 08-10-2015, 11:02 AM
Larco Larco is offline
 
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Location: DVT Phoenix
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If it is a STEEL arm, some have used a round file to clean up the slot and make it deeper by a couple thousands. One of the aftermarket venders has recommended this and it seems to work very well. Larry
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  #10  
Old 08-10-2015, 11:06 AM
riobison riobison is offline
 
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Location: Oliver BC & Red Deer Alberta Canada
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I'll change out the arm as there is a small bit of wear (still not sure what is acceptable wear) put in a new spring and key as they are cheap and should be good to go.

I take it that if everything is like new then the design is good and sufficient to do its job even in strong cross winds.

I lifted the tail off the ground and put a scale on the trailing edge of the wheel and it took 3 1/2 to 4 pounds of pull to disengage the little guy in either direction. I used a small scale to measure the pull. Not overly scientific not overly accurate but it is a bench mark.

Will compare the measurement with the new parts installed.

Thanks
Tim
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