In my job as a manufacturing engineer in a plant I have occasion to use
different springs. The characteristics of the spring are wholly determined
the material, diameter of the wire and diameter of the coil. There arre
several if not many houses out there who do nothing but wind springs. Many
are standard and do not have to be specially made. In following this
thread about the springs I seem to get the impression that every one thinks
there is a special recipe to get these springs from a special unique
supplier. What you want is an extension spring with a certain diameter
wire, certain diameter coil and of a certain length. You can call Lee
Spring, or Capitol spring or many others to see if is one of their stock
units or what it would take for them to wind it special which they do all
the time. You can find them on the internet.
Steve Hagar
A143
Mesa, AZ
Steve Hagar
hagargs@earthlink.net
> [Original Message]
> From: Paul Boulet <possibletodo@yahoo.com>
> To: <europa-list@matronics.com>
> Date: 11/1/2005 10:51:20 AM
> Subject: RE: Europa-List: Nose Gear Springs
>
>
> I'm willing to be point man for U.S. collection/distribution if needed
>
> Paul Boulet, N914PB
> Malibu, CA
>
> G-IANI <g-iani@ntlworld.com> wrote:
>
>
> Thanks to all those who have declared an interest in the Trigear bungee
> replacement springs. At this moment 13 builders have said they are
> interested.
>
> Here is some background so you know where we have got to.
>
> Two springs have been used to replace the nose wheel bungee and this has
> been done on at least five aircraft (on the Dutch register). The spring
> specification was done by Nico Groot and it took three attempts to get a
> suitable spec. Andy Draper was aware that the work was being done and had
> some reservation as to how successful it might be. Those who have them are
> very happy with the result.
>
> I have produced a drawing of the spring (complete with English translation
> of the specification) and calculated forces "on the stop" and at the
extreme
> of the spring travel (hitting the wire stop).
>
> Andy's reservation was that the spring rate (Young's modulus) of the
spring
> is much higher than that of the bungee. The modulus of a steel spring is
> linear whereas that of the bungee is highly non linear. This is because a)
> The Young's modulus of rubber is non linear, b) the bungee is multi
strand,
> c) the sheath probably plays a significant role, d) the bungee may have a
> safety thread, e) the installation may have anything from 12 to 20 working
> strands and f) these may be of two lengths. So the Young's modulus of your
> bungee might anything. Based on some very crude measurements I think mine
> may be about 25N/mm. The spring rate of the two springs is 65N/mm. While
> this arithmetic is interesting it is somewhat academic as only about half
> the load on the nose wheel is known (the weight of the aircraft). The
> remaining loads are dynamic loads caused by bumps so they are almost
> impossible to quantify.
>
> I have talked this through with Andy and reached the following
conclusion:-
>
> a) The initial springing is done by the nose leg, just as with the bungee.
> b) Once the nose leg is bounced off the stop the spring will give a
"harder"
> ride but this may prevent the wire stop being reached. In fact the higher
> spring rate may actually reduce the chance of a bent leg or prop strike.
> c) Once the nose leg hits the stop, and if sufficient further force is
> applied, the nose leg is going to bend.
>
> Following this logic, as long as the spring tension at full extension to
the
> stop (wire loop) is less than the strain at which the nose leg will bend
> then there is no disadvantage to using the springs. Andy has offered to do
> the calculations on the strain needed to bend the nose leg. Andy does not
> wish to see the protection, against bending the nose wheel leg lost.
>
> The disadvantage of using the spring is a weight increase of about 1KG.
The
> advantage is "fit and forget" and less blood on the floor.
>
> Assuming Andy is satisfied that the springs do not significantly increase
> the danger of bending the nose leg then I will get a modification
> application off to the PFA as soon as possible (the paperwork is already
> prepared). If Andy's calculations suggest these springs could be a problem
> then we may have to look at the spring design again.
>
> Everyone should be aware that the details on my drawing are more a
> requirement than a complete specification. They do not specify the
material,
> heat treatment etc so my remarks apply to only those springs made by the
> Dutch manufacturer. It will be perfectly possible for others to
manufacture
> suitable springs but it will require some development work and may not be
> cost effective.
>
> As Tim Weert has clearly explained (his posting dated 31/10/2005) the
> manufacturing cost of the springs has a high fixed overhead. To offset
this
> it will be of great benefit to order in bulk. My preference would be for
> Europa(2004) to handle this but I am prepared, if necessary, to act as
> co-ordinator.
>
> I will keep you all informed as to progress.
>
> Ian Rickard #505 G-IANI XS Trigear
> Europa Club Mods Rep (Trigear)
> e-mail mods@europaclub.org.uk
> or direct g-iani@ntlworld.com
>
>
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