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  #1  
Old 01-19-2013, 12:55 PM
Jason Krause Jason Krause is offline
 
Join Date: Dec 2008
Location: Glendale, AZ
Posts: 65
Lightbulb Tail Wheel Yoke Improvements

We were curious about the possible benefits of a Ball Bearing Tail Yoke as compared to the standard bushing type that come stock with tail the dragger RV’s. After building a few samples and doing some initial testing, the results are quite impressive.

We have determined the ball/needle bearings have made the tail wheel much easier to steer and completely eliminated the hysteresis or “stickiness” caused by the normal bushing friction. There also doesn’t seem to be any indication of “shimmy."

Currently we are testing the yoke to see how it performs in harsh conditions. Primarily, making certain the bearings can handle the loads and conditions. i.e. large cracks commonly found in taxi and runways, moisture and fine dirt/silt from unimproved surfaces. Additionally, some less than ideal landings are being performed to further abuse the complete assembly.

Edit: Check out this video http://www.youtube.com/watch?v=vOjhB2AX1YY

We would love to get some feedback from all you tail dragger drivers about this possible upgrade. If all goes well, we will have the yoke available for sale soon, in our online store. Be sure to visit JD Air Parts at JDair.com for more information and check out our other products.


CNC machined and welded from 4130 steel and powder coated gloss black.


Notice the reduced "squat" angle. As long as shimmy remains at bay this looks much better.


This yoke will work other tailwheel products that are compatible with the 7/8" Van's setup.
However when combined with our Steering Link, Fork, New Control Arm* (*not pictured) and a light weight tail wheel the result is very impressive.



Just a quick exploded CAD rendering for a look inside. The aluminum sleeve is needed so the locking pin slides between the bearings for assembly.


Some of the prototype parts separately here.
__________________
Jason Krause
RV-7 SB Finish Kit
Flying other people's stuff RV-9, Kit Fox.....
www.JDair.com
RV accessories including TailWheel Steering Links,
Upgraded Tailwheel Forks and Rudder Pedal Extensions.

Last edited by Jason Krause : 02-03-2013 at 05:24 PM. Reason: added links, video link
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  #2  
Old 01-19-2013, 01:56 PM
rvbuilder2002 rvbuilder2002 is offline
 
Join Date: Jul 2005
Location: Hubbard Oregon
Posts: 10,088
Default

Looks nice. Do you have any preliminary weight projections compared to the standard issue unit. Resolving the constant maint. requirements of the standard unit would be nice, but this is the least desirable location on most RV's for adding weight.
One comment though, at first glance (not having done any calculations) it looks like the bending moment where the fork attaches to the pivot shaft will be quite high. Has static load tests been done on it?

Any option to use standard links and springs (for those that don't like the single link)?
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  #3  
Old 01-19-2013, 06:40 PM
Jason Krause Jason Krause is offline
 
Join Date: Dec 2008
Location: Glendale, AZ
Posts: 65
Default

Thanks! Great questions.

Currently the weight increase is 4 oz's when comparing just the yokes. This is not much, and can be offset with a light weight tail wheel and/or our fork.

YES! All the standard parts and most others (springs, fork and arms) can be used with the this yoke.

The fork:
The bending moment I believe you are referring to is not a concern due to the thickness of the horizontal plate and the way the lower axle flanges are positioned under the pivot shaft. Calculations and more importantly load tests were performed and the result was a distorted stock tail yoke (not likely in reality because of the tail spring) The tail spring like the main gear legs permanently distorts before any damage will happen to the airframe or components bolted to the other end....we hope
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Jason Krause
RV-7 SB Finish Kit
Flying other people's stuff RV-9, Kit Fox.....
www.JDair.com
RV accessories including TailWheel Steering Links,
Upgraded Tailwheel Forks and Rudder Pedal Extensions.
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  #4  
Old 01-19-2013, 06:54 PM
GusRV8 GusRV8 is offline
 
Join Date: Mar 2009
Location: Virginia
Posts: 37
Default locking pin area

Is the locking pin area that much larger than the pin itself to give a free-swivel area prior to actuating for full freedom of rotation? If I recall correctly, the 'old' style is positively captured in a much smaller range of motion prior to breaking loose. I assume that is for a more positive feel than if it were free to move through what appears to be a much larger range prior to release.
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  #5  
Old 01-19-2013, 07:14 PM
David Paule David Paule is offline
 
Join Date: Dec 2009
Location: Boulder, CO
Posts: 5,573
Default

The loads are surprisingly large, especially in off-nominal conditions such as pulling the plane into the hangar, over a lip. By surprisingly large, look up "Hertzian contact stress" and see for yourself.

FYI....

Dave
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  #6  
Old 01-20-2013, 09:00 AM
RV8Squaz's Avatar
RV8Squaz RV8Squaz is offline
 
Join Date: Feb 2006
Location: Senoia, Georgia
Posts: 986
Default

Now that is something I am interested in! I am tired of having to disassemble and lubricate that tailwheel every 20-25 hours. I'm in. As long as Van's standard parts such as the wheel, arm, and chains will fit. Another desire is that it be offered in white or light gray powder coating. My tailwheel parts are all red and the paint would cover white or light gray much nicer.

P.S. Does the height of the tail change?

Jerry
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  #7  
Old 01-20-2013, 01:21 PM
Jason Krause Jason Krause is offline
 
Join Date: Dec 2008
Location: Glendale, AZ
Posts: 65
Post A few responses

Quote:
Originally Posted by RV8Squaz View Post
Now that is something I am interested in! I am tired of having to disassemble and lubricate that tailwheel every 20-25 hours. I'm in. As long as Van's standard parts such as the wheel, arm, and chains will fit. Another desire is that it be offered in white or light gray powder coating. My tailwheel parts are all red and the paint would cover white or light gray much nicer.
P.S. Does the height of the tail change?
Jerry
Jerry, Glad you are interested.
  • The reduction in maintenance is very exciting, we are also looking forward to that.
  • The stock Vans parts should work fine, however we can't control their tolerances so I couldn't 100% guarantee that....The plan is for all the parts to be interchangeable.
  • There wont be much change in tail height with just the yoke. The aftermarket forks will of course raise the tail.
  • We will offer the yoke just like our fork either in Black Powder Coat or Plain without any coating.

Quote:
Originally Posted by David Paule View Post
look up "Hertzian contact stress" and see for yourself.
Dave
  • The possible brinelling of the bearings is certainly one of our concerns and will be inspected thoroughly during our testing process.

Quote:
Originally Posted by GusRV8 View Post
Is the locking pin area that much larger than the pin itself to give a free-swivel area prior to actuating for full freedom of rotation?
  • Not exactly sure what your asking but the locking/swivel mechanism remains mostly unchanged from the stock setup.
__________________
Jason Krause
RV-7 SB Finish Kit
Flying other people's stuff RV-9, Kit Fox.....
www.JDair.com
RV accessories including TailWheel Steering Links,
Upgraded Tailwheel Forks and Rudder Pedal Extensions.
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  #8  
Old 01-20-2013, 07:37 PM
Geeman Geeman is offline
 
Join Date: Apr 2010
Location: Houston TX KDWH
Posts: 391
Default Ready to purchase.

I am about to pull the trigger on a Tailwheel upgrade and was planning to purchase one of yours. I was thinking the other day...this thing would not stick so bad with a bearing. If you have them available now I am ready to purchase. Please contact me at geekyle@yahoo.com or 281-455-6784 and let me know. Thanks.
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Kyle Gee
Purchased and sold flying RV-6
RV-7 Kit (sold to purchase C150 to train my kids)
Purchased flying RV-7
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  #9  
Old 01-21-2013, 07:01 AM
Pablo Pablo is offline
 
Join Date: Aug 2008
Location: Frederick, MD
Posts: 83
Default Great idea!

Sign me up! I've got one of your originals and it definitely sticks (especially with a passenger in the back seat of my RV-4. This sounds like a needed upgrade.
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  #10  
Old 01-21-2013, 08:33 AM
Skysailor Skysailor is offline
 
Join Date: May 2011
Location: Atlanta, GA
Posts: 315
Default When can I buy one?

I am very interested in this. Will you sell the entire thing as a unit? I have an early 4 with the non swivel tailwheel. It will me modified to accept the full swivel but if your unit comes with all the parts I am very interested.

Mark Burns
404-433-2787
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