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Re: Tailwheel calculations

Subject: Re: Tailwheel calculations
From: Europa <Enquiries@europaaviation.co.uk>
Date: Tue, 9 Dec 1997 13:37:55
      A comment worth adding to the tailwheel mod saga in general (not to
this posting in particular) is that we at Europa carried out a lot of
taxiing/ take-off/ landing trials with various geometries of tailwheel
assy, some of which were calculated and others which were developed from
the trials. The final design is a result of all these trials and the
continuing experience being gained on both of our mono-wheel aircraft.
     This is not to say that other solutions won't work, but bear in mind
that somewhere the theory has to stop and the practical take over. 

 Regards - Andy


>For those who are still interested in tailwheel geometries and are not
>thoroughly bored by it all, I should point out that the program produced
>answers for positive ( aft going deflections of the input arm ) as well as
>negative going (pulls). Aft dellections would only be meaningful if the
>coupling was by a rod, not a cable.   One really only needs the full
>deflection when the input arm is pulled against the 45 deg. stop. These are
>easlily tabulated.
>
>TAILWHEEL MOD. DESIGN OPTIONS 
>for Input angle -45 deg.( pull ) 
>Coupling dist 942  (typical)    Wheel horn rad. 63.5 (Europa)
>Wheel arm offset  25   mm.(Europa)
>
>Input arm offset  0    (at the old wheel position)
>
>Input arm rad.   Output angle deg.   Slack mm. in other cable.
>       60              -39                          14
>       65              -42                          15
>       70              -45                          17
>       75              -48                          19
>       80              -52                          21
>       85              -56                          24
>       90              -60                          26
>       95              -64                          28
>
>Any matching offest on the input loses deflection (though it is somewhat more
>linear)
>
>Input arm offset  12 
>
>       60              -30              26
>       65              -33              28
>       70              -36              30
>       75              -39              31
>       80              -43              33
>       85              -46              35
>       90              -50              37
>       95              -54              39
>
>Europas 25mm offset certainly gives some gain in sensitivity when not running
>straight, if that is what is needed, and I imagine not many will want to
>modify their wheel arm to make it otherwise. But if you do use zero
offsets on
>both arms, clearly with both at 63.5 you will get 45 output with no slack.
 An
>80 mm  radius input arm will give 60 deg output with just a few mm. slack,
>which will easily be absorbed by the springs.
>
>Incidentally the old tail wheel post provides a simple way of making a lower
>arm without hacking out thick plate. Just insert a 3/8" steel rod through the
>old bracket, and hook the cable ferrules over the ends, trapping between
>washers held by split pins.  Easy to adjust too with spacer tubes.
>
>Graham C  G-EMIN
> 
>
>


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