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Tail wheel strut bending

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rap(at)isp.com
Guest

Posted: Sat Jan 20, 2007 6:00 am Post subject: Tail wheel strut bending

I made the plunge and  ordered a titanium rod for my strut. Real expensive $378 from McMaster-carr. Had  to order 36" so I can get two out of the lgth.I actually made a sleeved  4130 tail strut. But the hassle of finding & heat treating was not  worth it. The titanium will be allot more corrosion proof. Were I'm looking at  putting my Kolb on my floats as soon as I get my sea plane rating.  That closed the deal since with the floats the tail will be in the water  allot.

      To change the  subject I also ordered the Rans S12 912 carb. conversion kit to reverse the  912 throttle at the eng. This should fix my throttle problem of the cable  wanting to buckle going to idle. I'll keep everyone posted on  this.

      So if I can get  these two problems solved I can get my plane inspected and flying. Rick  Pearce Kolb Mark3C 912ULS  

    [quote][b]

herbgh

Joined: 10 Jan 2006
Posts: 145

Posted: Sat Jan 20, 2007 7:09 am Post subject: Tail wheel strut bending

Rick and all

  

   wondering about titanium for main gear legs?  Anyone tried  them?  Herb 

  

 On Sat, 20 Jan 2007 07:58:51 -0600 "Rick Pearce" <rap(at)isp.com (rap(at)isp.com)> writes:

 [quote]        I made the plunge and    ordered a titanium rod for my strut. Real expensive $378 from McMaster-carr.    Had to order 36" so I can get two out of the lgth.I actually made a    sleeved 4130 tail strut. But the hassle of finding & heat treating    was not worth it. The titanium will be allot more corrosion proof. Were    I'm looking at putting my Kolb on my floats as soon as I get my sea plane    rating. That closed the deal since with the floats the tail will be in    the water allot.

        To change the    subject I also ordered the Rans S12 912 carb. conversion kit to reverse    the 912 throttle at the eng. This should fix my throttle problem of the    cable wanting to buckle going to idle. I'll keep everyone posted on    this.

        So if I can get    these two problems solved I can get my plane inspected and flying. Rick    Pearce Kolb Mark3C 912ULS  

 	  Quote: 	
		  



http://www.matronics.com/Navigator?Kolb-List

matronics.com



	
    

[b]

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Sat Jan 20, 2007 7:15 am Post subject: Tail wheel strut bending

I made the plunge and ordered a titanium rod for my strut.



 But the hassle of finding & heat treating was not worth it.



The titanium will be allot more corrosion proof.



     To change the subject I also ordered the Rans S12 912 carb. 

conversion kit to reverse the 912 throttle at the eng.



     Rick Pearce Kolb Mark3C 912ULS

Morning Rick:



Got a question:    How come you went with a rod and not a tube for 

your tail wheel strut?  I use heat treated .120" 4130, which is more 

than enough strength to do the job on my mkIII.  Would the titanium 

tubing be cheaper than solid rod?



You won't have to worry about the tail wheel strut coroding, but the 

tail post is still 4130.



Over the years I have found that shortening the tail wheel strut 

improves ground handling, reduces weight, and also reduces chances of 

bending.



Curious what RANS throttle reversal kit for the 912 set you back?



Take care,



john h

mkIII

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Sat Jan 20, 2007 7:49 am Post subject: Tail wheel strut bending

|  wondering about titanium for main gear legs?  Anyone tried them? 

Herb

Herb:



The Wondering Wench has them installed on her Max Air.



I would love to have them, if I could afford them.  I would go with 

tubing though, rather than solid rod.



Love my titanium tie down stakes.  Don't let anyone mess with them. 

hehehe  I believe Arty got her titanium gear legs from the same gent 

that makes up the titanium tie down states.



john h

mkIII

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

rap(at)isp.com
Guest

Posted: Sat Jan 20, 2007 1:01 pm Post subject: Tail wheel strut bending

$25 

---

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Sat Jan 20, 2007 1:22 pm Post subject: Tail wheel strut bending

From: "Rick Pearce"

| $25



Hi Rick:



Was wondering if titanium tubing would have been less expensive than 

solid rod?



Also wondering if tubing may not have been sufficient material to work 

as a tail wheel strut?



Thanks for the throttle info.



john h

mkIII

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

undoctor(at)rcn.com
Guest

Posted: Sun Jan 21, 2007 9:22 am Post subject: Tail wheel strut bending

Kolbers,

  

 I've watched the thread about bending the tailwheel strut,  including the question of replacing with a solid rod rather than a tube.   I'd like to note that when considering your choice it'd be well to consider the  resistance to bending in addition to weight and cost.   I tube is  inherently more rigid and resistant to bending than a solid rod even with  considerably less mass and weight.  The reason is because a rod only has  surface tension on the one surface for the length of the rod, whereas a tube has  two surfaces; both the OD surface and the ID surface; hence, almost double the  surface tension of a rod.  

  

 Surface tension is the reason it's possible to float a  piece of metal on water (you all remember the kids trick of putting a straight  pin on a piece of tissue paper floating in a glass of water, and when the tissue  gets sogged and sinks, the pin is left "floating" - not really floating in the  sense of displacing an equal weight of water, but of "floating" on the surface  tension of the water in the glass) and why water skeeters can casually  skate on the surface of a pond with only the balls of their little feet making  contact with the water.  

  

 A note of interest for those who recognize the validity of  the Bible, it is worthwhile to realize that all miracles are consistent with  nature, i.e., hungry Jesus turning rock into bread was a definite no-no, but  when the two walked on the water, it was a kind of strengthening or extension of  the laws of nature, not a contradiction of those laws.  Water to wine was  accelerated fermentation, etc.  Cool, huh.  (This "aside" IS Kolb  related because without the laws of nature, air wouldn't support a  Kolb and they'd just be funny-looking go-karts)

  

 Anyway, back to the initial thought, please research the  required wall thickness - a piece of discarded TV antennae will NOT do the  trick - but the bottom line is, far less metal will provide far greater  strength using tubing rather than with a rod.

  

 Dave Kulp

 Bethlehem, PA 

  [quote][b]

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Sun Jan 21, 2007 11:03 am Post subject: Tail wheel strut bending

Anyway, back to the initial thought, please research the required 

wall thickness - a piece of discarded TV antennae will NOT do the 

trick - but the bottom line is, far less metal will provide far 

greater strength using tubing rather than with a rod.



Dave Kulp

Bethlehem, PA



Dave:



Lot depends on how the strut is heat treated, tube or rod.



My strut has been thoroughly tested over more than 2,500 hours in 

extreme conditions with, probably, more tail wheel weight than most 

mkIII's.  What I fly with works well, is reliable, and will get you 

there and back home.



Do have a problem with buoyancy.  Can not get my tail wheel strut to 

float.  



john h

in soggy hauck's holler

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

d-m-hague(at)comcast.net
Guest

Posted: Sun Jan 21, 2007 3:40 pm Post subject: Tail wheel strut bending

At 12:20 PM 1/21/2007, David  Kulp wrote:

  	  Quote: 	
		  ... I tube is inherently more rigid and resistant to bending than a solid rod even with considerably less mass and weight.  The reason is because a rod only has surface tension on the one surface for the length of the rod, whereas a tube has two surfaces; both the OD surface and the ID surface; hence, almost double the surface tension of a rod... 	


 Sorry, but this is incorrect.  Surface tension is a phenomenon relating only to liquids, not to solids.  A solid's strength is a function of stress, or force per cross sectional area.  A solid bar is always stronger (and stiffer) than the same diameter tubing.  Actually, in bending, it's a matter of moment of inertia.  For the same weight, a tube will be stiffer, yes, because you can make it larger diameter.



 You are correct that the outer fibers are the most important; moment of inertia equals pi*r^4/4 (double the diameter and it's 16 times stiffer).  Thus the difference between a solid bar and a piece of tubing isn't that much.  For example, a 1" solid bar is about 46% stiffer than a 1" diameter 1/8" wall tubing.  The 1" solid bar is only 6.7% stiffer than a 1" diameter 1/4" wall tubing... but it IS stiffer.



                                 -Dana

 

 --

 --

 There are no bugs in this software, only unfulfilled features.    [quote][b]

jlsk1(at)frontiernet.net
Guest

Posted: Sun Jan 21, 2007 6:02 pm Post subject: Tail wheel strut bending

That settles it, I`m going to drill out my solid  rod to make it hollow, I`ll have the best of both.  : )

 [quote]   ---

dhkey(at)msn.com
Guest

Posted: Sun Jan 21, 2007 7:51 pm Post subject: Tail wheel strut bending

Ouch!

undoctor(at)rcn.com
Guest

Posted: Mon Jan 22, 2007 7:20 am Post subject: Tail wheel strut bending

 	  Quote: 	
		  Sorry, but this is incorrect.  Surface tension is a phenomenon relating 

      only to liquids, not to solids.  A solid's strength is a function of 

      stress, or force per cross sectional area.  A solid bar is always stronger 

      (and stiffer) than the same diameter tubing.  Actually, in bending, it's a 

      matter of moment of inertia.  For the same weight, a tube will be stiffer, 

      yes, because you can make it larger diameter.

      	


  

  

  

 Dana, I'm not a metalurgist, but you contradict one  I've discussed it with.

  

 Regards,

 Dave

 Do Not Archive

  [quote][b]

MKIIIX040

Joined: 31 Mar 2006
Posts: 123
Location: Millinocket, Maine

Posted: Mon Jan 22, 2007 8:19 am Post subject: Tail wheel strut bending

Would you rather break the tail rod (easily replaceable)  or tear off the lower verticl stab.

  

 Vic

 Me.

   [quote][b]

_________________
MKIIIX040
912UL

Rex Rodebush

Joined: 10 Jan 2006
Posts: 209
Location: Branson West area, Missouri

Posted: Mon Jan 22, 2007 8:41 am Post subject: Re: Tail wheel strut bending

Yes, the solid rod is stronger and stiffer than a tube of the same diameter.  However, the strength to weight ratio of the tube is much higher.



Rex Rodebush

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Mon Jan 22, 2007 8:52 am Post subject: Tail wheel strut bending

Would you rather break the tail rod (easily replaceable) or tear off 

the lower verticl stab.



Vic

Hi Ya'll:



Don't want to do either.



john h

mkIII

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

d-m-hague(at)comcast.net
Guest

Posted: Mon Jan 22, 2007 10:15 am Post subject: Tail wheel strut bending

At 10:19 AM 1/22/2007, David  Kulp wrote:

  	  Quote: 	
		   

 Dana, I'm not a metalurgist, but you contradict one I've discussed it with.

  	


 Perhaps he misunderstood your question, or you misunderstood his answer (the solid bar is stronger but the strength to weight ratio of the tube is higher as I said).  I'm not a metallurgist but I _am_ an aerospace engineer.



                                 -Dana

 --

 --

 There are no bugs in this software, only unfulfilled features.    [quote][b]

undoctor(at)rcn.com
Guest

Posted: Mon Jan 22, 2007 2:08 pm Post subject: Tail wheel strut bending

 	  Quote: 	
		  Sorry, but this is incorrect.  Surface tension is a phenomenon relating 

      only to liquids, not to solids.  A solid's strength is a function of 

      stress, or force per cross sectional area.  A solid bar is always stronger 

      (and stiffer) than the same diameter tubing.  Actually, in bending, it's a 

      matter of moment of inertia.  For the same weight, a tube will be stiffer, 

      yes, because you can make it larger diameter.Dana, I stand corrected.  I feel as if I've been had, or maybe the individual I was discussing it with attempted to put his knowledge into "layman's" terms for me. Since I don't know what your qualifications are, I called a copper tube factory closeby and spoke with an engineer and he backed up what you said about tubing may be ALMOST as strong, but never stronger.  He also asked the logical question, "If tubing were stronger than a rod, why would anyone ever use a rod?" Makes me wonder about the time I was working on my US and an electrical engineer flew in.  He saw me soldering joints for extra strength and he admonished me to crimp ONLY.  He said that the solder would fracture with the vibration but the simple crimp wouldn't.  When does one believe an expert?? Dave KulpBethlehem, PADana, I stand corrected.  I feel as if I've been had, or maybe the individual I was discussing it with attempted to put his knowledge into "layman's" terms for me. 	
0 	  Quote: 	
		  Dana, I stand corrected.  I feel as if I've been had, or maybe the individual I was discussing it with attempted to put his knowledge into "layman's" terms for me. 	
1 	  Quote: 	
		  Dana, I stand corrected.  I feel as if I've been had, or maybe the individual I was discussing it with attempted to put his knowledge into "layman's" terms for me. 	
2



  [quote][b]

d-m-hague(at)comcast.net
Guest

Posted: Mon Jan 22, 2007 2:21 pm Post subject: Tail wheel strut bending

At 05:06 PM 1/22/2007, David  Kulp wrote:



  	  Quote: 	
		   	  Quote: 	
		  Makes me wonder about the time

I was working on my US and an electrical engineer flew in.  He saw

me soldering joints for extra strength and he admonished me to crimp

ONLY.  He said that the solder would fracture with the vibration but

the simple crimp wouldn't.  When does one believe an expert??

	
	


 He has a good point.  When you solder a connection, the solder flows into the wires and you have what's essentially a solid wire... which isn't as flexible as the original multi stranded wire.



 I still tend to solder wires, though... maybe because I don't have a good crimping tool.  Too many of my crimped connections pull out of the terminal... but the wire doesn't break.



                                 -Dana

 --

 --

 There are no bugs in this software, only unfulfilled features.    [quote][b]

MKIIIX040

Joined: 31 Mar 2006
Posts: 123
Location: Millinocket, Maine

Posted: Tue Jan 23, 2007 6:56 am Post subject: Tail wheel strut bending

"I still tend to solder wires, though... maybe because I don't have a good  crimping tool.  Too many of my crimped connections pull out of the  terminal... but the wire doesn't  break."



                                -Dana

I'm with you on the soldered wires. Solder may crack but won't fall  or pull out of the terminal. I simply go the extra mile and put 2 layers of heat  shrink past any solder in the wire for better flex.

  

 Vic

 Me.

   [quote][b]

_________________
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912UL

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