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Hi All,
Had to toss in my 2 cents worth, because I think there's a few red herrings here that should be addressed.
"on 04/13/04 12:17 PM, Greg Bullough at [EMAIL PROTECTED] wrote:
At 11:59 AM 4/13/2004 -0400, [EMAIL PROTECTED] wrote:I believe that the restraint wire is actually part and parcel of the dual fork. The dual
act Fred Weick once told me that the cable makes the airplane slower because the wheel is in the prop slipstream. Also as you mentioned the fairing does not work, an the main problem is that the strut will not work until it is fully extended so you are landing on the taxi spring and possibly damaging it.
fork is longer than the original gear, and sticks down far enough that someone whoOK, I went out and took some comparitive measurements.
lands flat may very well land on the nose wheel. You only have to crawl around
at an Ercoupe gathering to discover how many of these planes have a history
of a nose gear collapse, as evidenced by the wrinkled bellies."
The early coupe double-fork nose gear (to SN 187) measures approximately 13-3/8" from where the nose strut "seats" down into the fork casting. This is a derived figure - it is 10" from the top of the fork casting to the axle centerline, less the 2-1/2" machined recess (common on all the forks), plus 5-7/8" for the exposed half of a 4" tire (allowing 1/4" for distortion by static weight).
Using the same method, the single-fork wheel support and 4" wheel used from SN 187-4423 on the ERCO steel gear oleo strut (34097) is approximately 13-7/8", or some 1/2 " longer! I did not have an example of (34355) used with the Electrol unit and 4" wheel to measure, but would presume dimensionally there would be no difference. (Forney machined double forks to fit either "steel" and "Electrol" struts, but the casting (and resulting overall length) was identical.)
I did not have an example of the single-fork wheel support and 5" wheel used with the Electrol unit on 415-E through G Models and Forneys to SN 5674 to measure. As an aside, Forney found the forging dies had been destroyed for the 5" cantilever support. Since it was deemed sensetive to "shimmy" problems, designed a double fork support after using up the inventory of the earlier single-fork unit.
It is not clear as to exactly when the Univair double arm Nose Gear Conversion Assembly (for 5" wheel-p. 21 of their Parts Catalogs) was made available. It was/is available for either the "steel" or Electrol strut; and I had no example(s) of it to measure.
Using the same method, the Forney double-fork wheel support and 5" wheel used on F-1 SN 5675 and on (and retrofits) is approximately 15-3/4", or 1-7/8" longer than the ERCO 4" wheel and single-fork support!
All of these struts use the same part number taxi spring, 34041, so these length variations directly affect tail height/wing angle of attack. Can anybody explain to me why grinding the taxi spring to restore the correct levelness (with new MLG rubber shock absorbers, of course) would not have been perceived as both easy and necessary to maintain the original design's tendency to stay on the ground until or unless the pilot pulled back on the wheel? Maybe they forgot?
Aren't we talking tail height and taxi spring here? Presence (or absence) of a snubber has no effect on where landing and taxi loads are assumed by the compression of the oleo strut. A snubber only acts to prevent full extension of the strut, but you still need the oleo to function.
"Unfortunately, this risk only increases with the (questionable) 415D mod's loss
of elevator authority. D-pilots tend to land on the flat side...they kind of have to.
You can't hold it back and hold it off as easily as you can with a -C or -E style
elevator. You have to be right on airspeed to avoid either ballooning or plopping.
Either a balloon or a plop can put a D's nose gear down first. I admit that on
N2906H I just accepted defeat and did a ker-plop landing about 5 MPH fast
most of the time. The 'ker' being the mains and the 'plop' being the nose gear
just after.
The bad pattern seems to be 1) touch nose gear first 2) bounce badly due to the pitch
up which results 3) repeat (1) and (2) until 4) the nose gear collapses."
"...the cable is there on the dual fork for a reason. Yes, it
has its down-side, which is a lot less down-side than a nose gear collapse.What was that reason, again?
Even Uncle Fred's wisdom on this has to be taken with a grain of salt; engineers
don't generally like people screwing with their designs, especially after they've
made a conscious decision, as Fred did, about the original nose gear design.
His point about the taxi spring and the fact that the strut doesn't load up with
oil on the right side of the valve is well taken...and can't really be helped with
the dual fork system."
Greg
Regards,
William R. Bayne
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