Same here. If I'm not already on the list, please add me.
Garry Stout
----- Original Message -----
From: "Alan Burrows" <alan@kestrel-insurance.com>
Subject: RE: Europa-List: Nose Gear Springs
> <alan@kestrel-insurance.com>
>
> Hi Ian
>
> If I'm not already on the list, please add me to it, also if Europa
> choose not to stock the springs, then let me know & I will help if
> required.
> Cheers
>
> Alan
>
> -----Original Message-----
> From: owner-europa-list-server@matronics.com
> [mailto:owner-europa-list-server@matronics.com] On Behalf Of G-IANI
> To: europa-list@matronics.com
> Subject: RE: Europa-List: Nose Gear Springs
>
>
> 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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