Hi Glen,
I agree with what you say, but I spoke instead of the die cast (I
think) aluminum double fork main landing gear legs and forks original
to most, if not all prewar coupes. I do happen to have a new "old
stock" (unused) prewar double fork nose wheel support (fork) that
appears to be cast aluminum. Any use of forged aluminum in prewar
production light planes was probably rather sparing due to associated
extra expense (such difference being significantly reduced by the end
of the war).
Ercoupe Service Memorandum No. 34 confirms the use of "aluminum alloy
permanent mold nose gear wheels" and "die cast magnesium wheels"
which, per Ercoupe Service Bulletin No. 16 were then replaced (due to
flaws or brittleness of the material) by a later "Permanent Mold
Aluminum Alloy Nose Wheel".
The "steel" gear seen today on most early Ercoupes was designed
either after the prewar "production run" or at the very end of it, as
I have a letter from ERCO to the War Department offering to supply
the later steel gear for the Ercoupes the government had purchased.
With the original 7.00 x 4 tires long out of production, only the
side-axle "steel gear" allows fitting of the oversize 8.00 x 4 tires
still available. They are far too large to fit inside of the double
fork main gear castings (of which I have a pair).
Presumably the DER would need to know the specific alloy and casting
method/production specification used by ERCO and associated
dimensional information, and a demonstration (hopefully short of
destruction) to design criteria maximum stress of the new trailing
arm. The fact that Cessna used 5.00 x 6 Cleveland wheels and brakes
on some production Cessnas should be sufficient "acceptable data"
inasmuch as the Cessna is heavier and has greater power.
Thanks for the response!
WRB
--
On Aug 23, 2010, at 13:02, Glenn Putnam wrote:
Nose gear forks are forged not cast ,castings do not have grain
structure(like wood) forgings do and are therefore stronger Glenn
Putnam
On Aug 22, 2010, at 6:30 PM, Greg wrote:
> Question for our certificated mechanics: Would it be "likely
> doable" (in your professional estimation) for a prewar Ercoupe
owner
> to invoke the "owner supplied parts" and have double forks (they
are
> symmetrical) cast that would accept 5.00 x 6 Cleveland wheels and
> brakes as were installed as main gear on some Cessnas for field
> approval by 337?
>
> Regards,
>
> William R. Bayne
Try AC 23-27. I 'spect you'll need to get a DER involved, and have
an accommodating FSDO.
Greg
