REFLECTOR: towbar

[Brian Michalk]

I think I have it right.
A taildragger airplane is at risk of a ground loop because the CG of the 
airplane is behind the main wheels.
A control surface is at risk of flutter if the CG is too far behind the 
pivot point.

On 11/8/2010 12:38 AM, Bob Jackson (Jax Tech) wrote:
>
> I think having the CG forward of the pivot point will tend to make the 
> nose wheel unstable and want to flip around 180 -- didn't you say that 
> backwards, Brian?  Having it aft of the CG would make it more stable 
> and less likely to shimmy, correct?  What am I missing?
>
> ------------------------------------------------------------------------
>
> *From:*reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] 
> *On Behalf Of *Brian Michalk
> *Sent:* Saturday, November 06, 2010 11:51 AM
> *To:* Velocity Aircraft Owners and Builders list
> *Subject:* Re: REFLECTOR: towbar
>
> Nice design, but normally, you want CG as far forward of the pivot as 
> possible, not aft.
>
> Also, there was an analysis here ... I think by Ulmann, who concluded 
> that our shimmy problems are not caused by the CG/pivot arrangement.
>
> On 11/05/2010 11:46 PM, Bob Jackson wrote:
>
> Dave,
>
> Our gear is retractable, so I'm not sure exactly how you might apply 
> what we did.  However, I can tell you that although many Velocity's 
> don't make any provision for it, we have found that adding a standard 
> tow bar male 'tang' arrangement to our nose gear leg has been an 
> invaluable feature.
>
> Moving the plane around in a crowded hangar at home, or when you're 
> traveling, it has been 'priceless' for us to be able to use a standard 
> small Cessna type 'manually' controlled tow bar, or one of the big 
> orange ones (common at most FBOs) to move our plane around.
>
> It might be more essential because our Velocity is so heavy, but when 
> we have a full load of fuel (93 gals), it is very difficult to move 
> our plane around -- either trying to push up small inclines, or for 
> tight maneuvering because with full fuel it is essentially impossible 
> to pick up our nose to make tight turns (unless you enjoy hernias!).
>
> My aircraft partner designed (with some ME help) and had fabricated 
> the tow bar adapter shown below, as it is attached to the top of our 
> nose gear fork.  This is the front view.  It is also important (as I'm 
> sure you would appreciate) that the extra weight of the 'tangs' is on 
> the back side of the fork -- for anti-shimmy reasons.
>
>
>
> From the back side it looks like our tangs are made from steel 
> threaded rod, but that's only half the answer.  Not shown in this 
> photo are the smooth-outside, threaded-inside aluminum caps that screw 
> onto the threaded rod on each side.  These caps are the proper 
> diameter to mate with the female receptacles of the standard orange 
> (or small manual red) tow bars that are common available.
>
>
>
> Hope this helps -- should be a piece of cake for a guy like you!
>
> Bob Jackson
>
> Apopka, FL X04
>
> Turbo XL
>
> N2XF
>
> PS  Sorry I missed you in Oregon this summer -- I had a great time, 
> and enjoyed flying out of both the Aurora and Troutdale airports.  
> Maybe next year...
>
> -----Original Message-----
> From: reflector-bounces at tvbf.org <mailto:reflector-bounces at tvbf.org> 
> [mailto:reflector-bounces at tvbf.org] On Behalf Of David Ullman
> Sent: Friday, November 05, 2010 10:58 PM
> To: reflector at tvbf.org <mailto:reflector at tvbf.org>
> Subject: Re: REFLECTOR: towbar
>
> I have moved my Velo to the airport for final assy and testing.  Getting
>
> close to a real airplane.  I will post pictures when it is al together for
>
> the first time.  Question, what do FG people do for a tow bar?  The front
>
> wheel has a pant on it with a bolt in the location where a tow bar 
> hooks on
>
> many other planes.  I just want to pull and steer by hand.  I could 
> just put
>
> a rope or a hook through the nose tie down and do pretty good.   I haven't
>
> come up with a better idea yet.  Any suggestions?
>
> David G. Ullman PhD ME
>
> Robust Decisions
>
> ullman at robustdecisions.com <mailto:ullman at robustdecisions.com>
>
> 541-754-3609
>
> ************
>
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