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tailwheel leaf spring

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icubob(at)newnorth.net
Guest

Posted: Tue Jul 08, 2008 4:54 am Post subject: tailwheel leaf spring

hi all, with all the tailwheel talk lately i want  to throw out a question as i am debating this with my project [fisher dakota  hawk]............. i read of a ''one tail spring'' installation failure and and  a and p suggested replacing the one spring installation ''just before it  breaks!'' so one spring sounds risky. i found a ''spring place;; in colorado  that will supply untreated material to be formed, then heat treat it for me to  leaf spring specs. sooooooooo  my question is ''what is the opinion of  safety and single spring installations?''

                                                                                            bob noffs

    [quote][b]

Michel

Joined: 10 Jan 2006
Posts: 966
Location: Norway

Posted: Tue Jul 08, 2008 5:23 am Post subject: tailwheel leaf spring

 	  Quote: 	
		   From: bob noffs [icubob(at)newnorth.net]

 sooooooooo  my question is ''what is the opinion of safety and single spring 

 installations?''


	


Well Bob, I am not metalurgist and know virtually nothing about the matter. But I noticed that my single leaf broke exactly in the middle, where the bend is greatest. If you can get someone to make a single leaf spring where that part is stronger/thicker/wider or whatever it takes to take the load, it may be good enough. It's like a mast or a tree; the higher it is, the less load it takes and the thinner it can be.



Just a thought.



Cheers,

Michel Verheughe

Norway

Kitfox 3 - Jabiru 2200

<pre><b><font size  color="#000000" face="courier new,courier">

_________________
Kitfox 3 - Jabiru 2200

kitfoxpilot(at)msn.com
Guest

Posted: Tue Jul 08, 2008 5:23 am Post subject: tailwheel leaf spring

The problem you could have with a single leaf spring break is the rudder hiting the ground and being damaged!  your best bet would be a 3 leaf spring! this is what I put on my Kitfox because of this problem! Go 3 leaf for peace of mind.

  

 Ray

   

 From: icubob(at)newnorth.net

To: kitfox-list(at)matronics.com

Subject: Kitfox-List: tailwheel leaf spring

Date: Tue C 8 Jul 2008 07:51:07 -0500

     hi all C with all the tailwheel talk lately i want to throw out a question as i am debating this with my project [fisher dakota hawk]............. i read of a ''one tail spring'' installation failure and and a and p suggested replacing the one spring installation ''just before it breaks!'' so one spring sounds risky. i found a ''spring place;; in colorado that will supply untreated material to be formed C then heat treat it for me to leaf spring specs. sooooooooo  my question is ''what is the opinion of safety and single spring installations?''

                                                                                           bob noffs

 	  Quote: 	
		  



 target=_blank>http://www.matronics.com/Navigator?Kitfox-List

ttp://forums.matronics.com

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The i’m Talkaton. Can 30-days of conversation change the world? Find out now.  [quote][b]

icubob(at)newnorth.net
Guest

Posted: Tue Jul 08, 2008 6:01 am Post subject: tailwheel leaf spring

[quote] ---

msm_9949(at)yahoo.com
Guest

Posted: Tue Jul 08, 2008 6:38 am Post subject: tailwheel leaf spring

Bob, As I suggested to Ryan there are alot of safe operational hours in the one leaf if you watch it and treat it right. Eventually tho, I'd want to replace it with at least a 2-leafer. Trick is knowing when. If it breaks while in service, there will be damage. Ask Michel and others. 

  

Marco Menezes N99KX 

Model 2 582-90 C-Box



--- On Tue, 7/8/08, bob noffs <icubob(at)newnorth.net> wrote:

  	  Quote: 	
		  From: bob noffs <icubob(at)newnorth.net>

Subject: tailwheel leaf spring

To: kitfox-list(at)matronics.com

Date: Tuesday, July 8, 2008, 8:51 AM



    hi all, with all the tailwheel talk lately i want to throw out a question as i am debating this with my project [fisher dakota hawk]............. i read of a ''one tail spring'' installation failure and and a and p suggested replacing the one spring installation ''just before it breaks!'' so one spring sounds risky. i found a ''spring place;; in colorado that will supply untreated material to be formed, then heat treat it for me to leaf spring specs. sooooooooo  my question is ''what is the opinion of safety and single spring installations?''

                                                                                           bob noffs

 	  Quote: 	
		  

	


	


           [quote][b]

pwmac(at)sisna.com
Guest

Posted: Tue Jul 08, 2008 7:21 am Post subject: tailwheel leaf spring

I have lots of experience with leaf springs in trucks that are 

modified for long travel. Conclusion is that leafs work great if the 

deflections are small due to less flex, like the stock cars and 

trucks. But, the more the spring flexes the sooner fatigue results in 

breakage and/or sag. The solution is to reduce the flex which results 

in a very stiff ride. Thus the need for a softer tire to help the situation.

For the Kitfox multiple springs for much less deflection (=stiff) and 

the Homebuilder soft tire or an inflatable tire are good ways to go.

Regards, Paul

===========

At 07:20 AM 7/8/2008, you wrote:

 	  Quote: 	
		   > From: bob noffs [icubob(at)newnorth.net]

 > sooooooooo  my question is ''what is the opinion of safety and 

 single spring

 > installations?''

Well Bob, I am not metalurgist and know virtually nothing about the 

matter. But I noticed that my single leaf broke exactly in the 

middle, where the bend is greatest. If you can get someone to make a 

single leaf spring where that part is stronger/thicker/wider or 

whatever it takes to take the load, it may be good enough. It's like 

a mast or a tree; the higher it is, the less load it takes and the 

thinner it can be.

Just a thought.

Cheers,

Michel Verheughe

lcfitt(at)sbcglobal.net
Guest

Posted: Tue Jul 08, 2008 9:08 am Post subject: tailwheel leaf spring

Bob,



Just a thought or two and maybe an opinion here.  the original springs were 

single leaf.  My guess is that there are lots of guys still flying with the 

single leaf. Yes they can brake, but I doubt they would suddenly break 

without some visible evidence of eminent failure.  I doubt that most give 

that close a preflight and wonder if checking at annual would be sufficient 

to prevent breakage.



The springs should be springs.  I wonder for the lighter Kitfoxes if three 

springs would be like putting a bar between the tail of the airplane and the 

tail wheel giving no spring action at all.  The question relating to spring 

thickness in the different configurations is a good one.  If the three 

spring assembly is three 1/4" leafs and the two spring has two 1/4" leafs 

and I just measured the spring on my 1992 project and it is 1/4", you can 

imagine the ride you would get (or rather the ride the aft structure of the 

airplane would get) with a 3/4 inch of spring steel out there (especially if 

routinely landing on grass or gravel).  Also keep in mind that the average 

big Kitfox will "bottom" out empty, weight wise, in the 760 lb range and 

grow to over 1000 lbs as a few have done.  My first Model IV was 45 lbs at 

the tailwheel.  I don't think I need a spring that would handle a 100 lb 

tailwheel weight.  It also came with a single leaf, but I added another due 

to conversations on the list just like this one.  The second leaf (from the 

factory) was a partial leaf similar to what you see on muliple leaf systems 

on motor vehicles.  Interestingly, I had a bit over 900 hours on the 

airplane when I made the emergency landing that destroyed the airplane and 

the only airframe components that survived without any damage at all were 

the main gear "Hammerhead" and tailwheel assemblies - there was one flat 

tire.  Not being an engineer, I sometimes wonder about the multiple leafs 

with bolt attachments at both ends.  I can't imagine they are as flexible as 

a system of partial leaf springs.



I recently talked to a friend that wants to buy an ultralight to get in and 

out of a pretty remote 300 acres he owns near here north of Placerville.  I 

Can't remember the type, but he mentioned the lift strut attach point on his 

model of choice has a history of failure after so many years or hours of 

use.  As a solution, they routinely replace the part every two years, as I 

recall.  He seemed quite comfortable with that plan as, it seems, is the 

rest of the fleets pilots.  It sort of scares the daylights out of me as a 

lift strut failure is a big deal and might just be a life altering 

experience where the failure of a tailwheel spring might ruin a day or two.



But that being said,  I don't think I would want my airplane beat up on the 

ground with too much spring back there.  Right now with no empennage on the 

airplane the single leaf is too much spring as the caster angle gives the 

same result that Steve reports with his three spring set-up.



Here is the opinion part.  If the only spring available for replacement is 

the three spring unit.  I am tempted to use them one at a time and then plan 

on replacing them periodically.  Or more likely cutting the springs to give 

a system like I had, essentially giving a tapering effect to the structure. 

How often do we see motor vehicles on the side of the road with broken leaf 

springs.



Lowell



---

Fox5flyer
Guest

Posted: Tue Jul 08, 2008 9:33 am Post subject: tailwheel leaf spring

Good points Lowell.  Here's my opinion.

A simple solution for the lighter tail Foxes would be to buy the three leaf 

unit and remove the center leaf and go with the main and helper leaves. 

There is no way the two mains should be bolted front and back because they 

need to move independently on hard landings.  By using a main and helper it 

would be simple to just cut and taper the helper to terminate a short 

distance from the tailwheel bolt thereby giving it room to move 

independently of the main.  The heavier Foxes would probably be better with 

all three leaves, but each should be able to move independently.

Deke Morisse

Mikado Michigan

S5/Subaru/CAP 377+ TT

"The aim of an argument or discussion should not be victory, but progress."

- Joseph Joubert



---

Lynn Matteson

Joined: 10 Jan 2006
Posts: 2778
Location: Grass Lake, Michigan

Posted: Tue Jul 08, 2008 11:40 am Post subject: tailwheel leaf spring

Why not just buy the 3-leaf spring from Kitfox and be done with it?  

IF it will work with your model Kitfox, that is.



My original 2-leaf spring (I count all the leaves) broke and the  

tailwheel flopped around, slightly damaging the rudder fabric (not  

very bad as I haven't fixed it yet from 2 years ago). So I'd have to  

say I have a VERY LOW opinion of a single leaf, or even a 2-leaf  

installation. I count all the leaves, so the single to me is a single  

leaf....a 2 leaf spring is a main leaf (1 leaf bolted on both ends),  

and a helper/booster leaf bolted on just the fuselage end....and a 3- 

leaf (2 main leaves bolted at both ends, and a helper/booster leaf  

bolted on just the fuselage end.

If I'm using the wrong terminology, how about John McBean...who sells  

the 3-leaf spring that I now use....jumping in here and setting us  

all straight?



The main thing to think about when looking at your tailwheel spring  

setup is, what happens if the one main leaf breaks? Do you have  

another? Where does the tailwheel assembly go when the main spring  

breaks? The chances of a 2-MAIN-leaf spring breaking both mains in  

the same incident seems to be "not bloody likely."



Lynn Matteson

Kitfox IV Speedster

Jabiru 2200

Status: flying w/545 hrs





On Jul 8, 2008, at 8:51 AM, bob noffs wrote:



 	  Quote: 	
		   hi all, with all the tailwheel talk lately i want to throw out a  

 question as i am debating this with my project [fisher dakota  

 hawk]............. i read of a ''one tail spring'' installation  

 failure and and a and p suggested replacing the one spring  

 installation ''just before it breaks!'' so one spring sounds risky.  

 i found a ''spring place;; in colorado that will supply untreated  

 material to be formed, then heat treat it for me to leaf spring  

 specs. sooooooooo  my question is ''what is the opinion of safety  

 and single spring installations?''

                                                                        

                     bob noffs

 http://www.matronics.com/Navigator?Kitfox-List_- 

 ============================================================ _- 

 forums.matronics.com_- 

 ============================================================ _- 

 contribution_- 

 ============================================================

_________________
Lynn
Kitfox IV-Jabiru 2200
N369LM

Lynn Matteson

Joined: 10 Jan 2006
Posts: 2778
Location: Grass Lake, Michigan

Posted: Tue Jul 08, 2008 11:48 am Post subject: tailwheel leaf spring

Good analogy, Michel....now add another mast right next to the  

original, throw a rope around the two masts at the top, and you've  

just built in a safety factor of 100%.  : )



Yeah, I know.....you weight junkies will just have to eat another  

less burger.



Oops, one important problem with your mast/tree analogy...there's  

nothing hanging off the very top of the mast/tree. In the airplane  

scenario, we've got our asses hanging (sort of) off the end of that  

mast/tree.



Lynn Matteson

Kitfox IV Speedster

Jabiru 2200

Status: flying w/545 hrs





On Jul 8, 2008, at 9:20 AM, Michel Verheughe wrote:



 	  Quote: 	
		  > From: bob noffs [icubob(at)newnorth.net]

> sooooooooo  my question is ''what is the opinion of safety and  

> single spring

> installations?''



 Well Bob, I am not metalurgist and know virtually nothing about the  

 matter. But I noticed that my single leaf broke exactly in the  

 middle, where the bend is greatest. If you can get someone to make  

 a single leaf spring where that part is stronger/thicker/wider or  

 whatever it takes to take the load, it may be good enough. It's  

 like a mast or a tree; the higher it is, the less load it takes and  

 the thinner it can be.



 Just a thought.



 Cheers,

 Michel Verheughe

 Norway

 Kitfox 3 - Jabiru 2200

 <pre><b><font size  color="#000000" face="courier new,courier">



 List">http://www.matronics.com/Navigator?Kitfox-List</a>

 forums.matronics.com</a>

 www.matronics.com/contribution</a>



 </b></font></pre>

_________________
Lynn
Kitfox IV-Jabiru 2200
N369LM

Lynn Matteson

Joined: 10 Jan 2006
Posts: 2778
Location: Grass Lake, Michigan

Posted: Tue Jul 08, 2008 12:36 pm Post subject: tailwheel leaf spring

Gotta put in my 2 cents worth on the suggestion of a main and  

helper....what happens if the main breaks?



If anybody has seen the 3-leaf (2 mains...1 helper) from John McBean  

(www.kitfoxaircraft.com), you'll notice that the upper main leaf  

(that's the middle spring) has an enlarged hole in the tailwheel end  

of the spring. That is, the hole in this leaf is larger than the bolt  

that protrudes through it. With the tailwheel-attaching bolt inserted  

through the main leaves and the tailwheel assembly and  tightened,  

but not to the point of absolutely squeezing the whole assembly  

together as one piece...unable to move...the spring assembly will be  

able to flex, and the ride will be moderately soft/hard, according to  

your definition. But it WILL flex, due to the inner member of this  

assembly...the main leaf with the larger hole in it...being able to  

"absorb" the differing length of travel of the "small-hole" main  

leaf, because the bolt will be able to move within this larger hole.



When I assembled my 3-leaf spring, I greased the leaves, and used a  

self-locking nut on the tailwheel end. This assembly loosens after  

awhile, and I re-tighten it every few weeks. I plan on using a castle  

nut and drilled bolt in exchange for the nylon self-locker and  

undrilled bolt. This way I can adjust to some degree the tightness of  

the clamping pressure, and maybe not have to retighten every so  

often. Maybe an extra drilled hole in the bolt will allow some fine- 

tuning of the clamping pressure, or perhaps a thin washer will do the  

trick.



Hey, Deke, I landed in your back yard with no problems, didn't I? : )



Lynn Matteson

Kitfox IV Speedster

Jabiru 2200

Status: flying w/545 hrs





On Jul 8, 2008, at 1:26 PM, fox5flyer wrote:



[quote] 

 <fox5flyer(at)idealwifi.net>



 Good points Lowell.  Here's my opinion.

 A simple solution for the lighter tail Foxes would be to buy the  

 three leaf unit and remove the center leaf and go with the main and  

 helper leaves. There is no way the two mains should be bolted front  

 and back because they need to move independently on hard landings.   

 By using a main and helper it would be simple to just cut and taper  

 the helper to terminate a short distance from the tailwheel bolt  

 thereby giving it room to move independently of the main.  The  

 heavier Foxes would probably be better with all three leaves, but  

 each should be able to move independently.

 Deke Morisse

 Mikado Michigan

 S5/Subaru/CAP 377+ TT

 "The aim of an argument or discussion should not be victory, but  

 progress."

 - Joseph Joubert



 ---

_________________
Lynn
Kitfox IV-Jabiru 2200
N369LM

Michel

Joined: 10 Jan 2006
Posts: 966
Location: Norway

Posted: Tue Jul 08, 2008 1:09 pm Post subject: tailwheel leaf spring

 	  Quote: 	
		   From: Lynn Matteson [lynnmatt(at)jps.net]

 Oops, one important problem with your mast/tree analogy...there's  

 nothing hanging off the very top of the mast/tree. In the airplane  

 scenario, we've got our asses hanging (sort of) off the end of that  

 mast/tree.


	


Hey! You don't know where my ass is hanging from in the Norwegian woods, Lynn! 

Seriously, I am always amazed to see engineer constructions where weight and strenght are optimized in beams and structures. I only observe that the original Kitfox spring leaf is an evenly thick and wide bent piece of metal. Anyone can then guess where it is most likely to break. Maybe a better design than the even leaf would be better for the strenght/weight ratio.



Cheers,

Michel Verheughe

Norway

Kitfox 3 - Jabiru 2200

<pre><b><font size  color="#000000" face="courier new,courier">

_________________
Kitfox 3 - Jabiru 2200

Lynn Matteson

Joined: 10 Jan 2006
Posts: 2778
Location: Grass Lake, Michigan

Posted: Tue Jul 08, 2008 2:37 pm Post subject: tailwheel leaf spring

On Jul 8, 2008, at 5:06 PM, Michel Verheughe wrote:

 	  Quote: 	
		  > From: Lynn Matteson [lynnmatt(at)jps.net]

> Oops, one important problem with your mast/tree analogy...there's

> nothing hanging off the very top of the mast/tree. In the airplane

> scenario, we've got our asses hanging (sort of) off the end of that

> mast/tree.

 Hey! You don't know where my ass is hanging from in the Norwegian  

 woods, Lynn! 

You're right, and thank goodness I'm lacking in knowledge in THAT  

department, Michel. : )

 	  Quote: 	
		   Seriously, I am always amazed to see engineer constructions where  

 weight and strenght are optimized in beams and structures. I only  

 observe that the original Kitfox spring leaf is an evenly thick and  

 wide bent piece of metal. Anyone can then guess where it is most  

 likely to break. Maybe a better design than the even leaf would be  

 better for the strenght/weight ratio.

  I forgot all about the single leaf spring...made by Grove, wasn't  

it?...and as I recall, they quit making it, right? Now there was a  

problem waiting to happen, it seems to me. One break and your butt is  

on the ground. Enter the 2-leaf spring....the main breaks, and your  

butt is on the ground. Enter the 3-leaf spring...one break and  

Viola!, you're still rolling on the tailwheel...in most cases. I'm  

not saying that the 3-leaf spring (2 main leaves) is the end-all in  

engineering practices, but it beats the other two ideas because it  

has redundancy, unless I'm missing something.

Lynn

_________________
Lynn
Kitfox IV-Jabiru 2200
N369LM

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