taildragger to trike

[anon]

A couple of folks have built their Himaxes and Minimaxes as trikes. On the
surface, it doesn't seem like an overwhelmingly difficult engineering
problem to overcome. How deluded might I be?

[J.Kahn]

anon wrote:
> A couple of folks have built their Himaxes and Minimaxes as trikes. On the
> surface, it doesn't seem like an overwhelmingly difficult engineering
> problem to overcome. How deluded might I be?
>
>
Moderately to extremely depending on how design/engineering savvy you
are. If someone has a successful installation just copy that.

[[email protected]]

On Feb 14, 7:23 pm, "J.Kahn" > wrote:
> anon wrote:
> > A couple of folks have built their Himaxes and Minimaxes as trikes. On the
> > surface, it doesn't seem like an overwhelmingly difficult engineering
> > problem to overcome. How deluded might I be?
>
> Moderately to extremely depending on how design/engineering savvy you
> are. If someone has a successful installation just copy that.

Be careful designing landing gear mount structure. Taxiing over rough
ground is really hard on gear, harder than bumpy landings. I've seen
some gear on ultralights that looks scary. Watched one collapse on
landing several years ago. And have heard of other gear failures on
homebuilts. We had a gear failure on a Glastar about five years ago,
when the single AN5 bolt sheared during braking after touchdown. The
gear is a round, tapered steel rod mounted in a steel tube socket
welded to the fuselage cage structure, and that AN5 bolt passed
through the tube and leg. Braking forces try to turn the rod in the
socket and landing/turning/taxiing loads try to push it inward, and
that bolt couldn't take it. After the repairs, it had a single 3/8"
NAS bolt, about three times stronger than the original AN5. Didn't
break no more.
So it ain't as simple as it looks. Worse, nosegears have to
be strong enough to take a lot more abuse than a tailwheel. The whole
weight of the airplane comes against the nosegear in a botched landing
or on touchdown on a really soft surface.

Dan

Dan

[Peter Dohm]

>
> Be careful designing landing gear mount structure. Taxiing over rough
> ground is really hard on gear, harder than bumpy landings. I've seen
> some gear on ultralights that looks scary. Watched one collapse on
> landing several years ago. And have heard of other gear failures on
> homebuilts. We had a gear failure on a Glastar about five years ago,
> when the single AN5 bolt sheared during braking after touchdown. The
> gear is a round, tapered steel rod mounted in a steel tube socket
> welded to the fuselage cage structure, and that AN5 bolt passed
> through the tube and leg. Braking forces try to turn the rod in the
> socket and landing/turning/taxiing loads try to push it inward, and
> that bolt couldn't take it. (additional info snipped)

I've never looked closely at the Glastar undercarriage, but the RV-8A uses a
similar system with good success. In the case of the RV that I looked at,
there would be no torsion applied to the mounting of the gear leg with the
tire correctly inflated. However, some torsional force would exist in the
event that the tire is either over-inflated or under-inflated.

Another point that I feel compelled to make, even though I really do not
like to say it, it that the gear leg and socket should NOT be lubricated. I
am not saying that the gear on the Glastar was, but just making the point
that the bolt is mainly to align the under carriage when not in use and that
friction should greatly exceed any capacity of the bolt when the airplane's
weight is on the wheels.

Peter
(Not a mechanic, but I've seen some strange things!)

[Stealth Pilot]

On Sun, 18 Feb 2007 12:32:19 -0500, "Peter Dohm"
> wrote:

>>
> but just making the point
>that the bolt is mainly to align the under carriage when not in use and that
>friction should greatly exceed any capacity of the bolt when the airplane's
>weight is on the wheels.
>
oh yeah? how did you work that out?
ever seen one flexing under load?

Stealth Pilot

[Peter Dohm]

> >>
> > but just making the point
> >that the bolt is mainly to align the under carriage when not in use and
that
> >friction should greatly exceed any capacity of the bolt when the
airplane's
> >weight is on the wheels.
> >
> oh yeah? how did you work that out?
> ever seen one flexing under load?
>
I haven't watched, but yes they do. And I still think that should provide a
jamming effect.

As to what, if anything should be used as an assembly coating, to prevent
rust, I really don't know.

OTOH, a similar system is used on a number of certified aircraft and
mechinics possess a wealth of knowledge. This is really the sort of thing
that should be discussed over a case of beer.

Peter