Doubled Tailwheel main spring

[johneeb]

Eric,

Did the 27 lb. increase in empty weight gain between the year 1960 and 2003 all come from the main gear swap or from some other some of it from other additions?

Johneb

[GAHorn]

George, the amount of weight added to the tail by putting (later)
180 gear on a 170 is not "infinitesimal". A little added weight back
there goes a long way. The early 180s I referred to in an earlier
post are both '53 models, are both similarly set up (Atley Dodge
rear seats, just about the same everything else except the gear
legs). One has stock / original '53 180 gear legs, the other later
model 185 gear legs. The latter is a pig on the ground handling-wise
(the tail is simply too heavy). I realize this is a personal opinion, but
wanted to get the point across that if you do opt for the 180 gear
that has the axles moved forward, it will feel "significantly different"
on the ground (the tail will feel darned heavy indeed). Maybe some
folks like the tail so heavy they can't pick it up off the ground with full
power and full forward yoke. I happen to not like it that way.

I'm thinking Cessna moved the axles forward on the later model
180s because the front end of the airplanes got heavier and heavier
with each subsequent model year (an -R or -K O-470 is 35-45 lbs heavier
than an -A or -J). If they didn't move the axles forward, the later
model airplanes would be too easy to tip over onto their noses
with maximum effort braking.

Once again, we're back to the idea that Cessna did a fantastic
job from the get-go of designing the landing gear for the airplane in
question. Swapping parts out for "heavier duty" 180 parts (such as
gear legs) can have advantages as well as disadvantages.

You and I agree on all these points, Bela. I was attempting to point out that a 22 pound (or so) increase in actual wt. at the tailwheel occurs quite naturally from flight to flight in any airplane (modified or not), depending upon the cabin loading of each flight. (And in any case, we don't have an accurate idea that the increase was the result of a main-gear mod.)

I also agree and believe Cessna got it right when they made the airplane. I disagree (a friendly act) with Eric regarding the tailwheel mainspring maintenance, however. The entire point of identifying it as a regular replacement item in the "things to do" list revolves aroung the extraordinary stress that spring suffers. The 100 hour inspection checklist published by Cessna in the Service Manual, pg 2-16, under Landing Gear, item 10, calls for inspection of that tailwheel spring. The unwritten/unspoken-yet-intended action of that inspection is that if the spring is found to be be insecure, cracked, bent, deeply scratched, dented, or the paint chipped or peeled.....that corrective action be undertaken. Corrective action might include replacement. The "To do" list is an attempt to prevent the damage to the rudder caused by broken springs which, as Eric correctly observed, is a common thing amongst our airplanes.
My personal opinion is that the orginal 170 spring is adequate, and correctly designed for the airplane, and that it is not, nor was it ever intended to be a "permanent" part, but instead is intended to be inspected and regularly replaced. I further believe that home-schooled engineering and inventing efforts which result in unapproved modifications are unlikely to be a better solution to regular maintenance. (I suppose that method might also be referred to as "good-ol' American Ingenuity, but I can't help but think of it as "good-ol' southern engineering'.) No criticism of others is meant. Each to his own, but I believe my recommendation can be better supported and defended.

[zero.one.victor]

Eric,

Did the 27 lb. increase in empty weight gain between the year 1960 and 2003 all come from the main gear swap or from some other some of it from other additions?

Johneb

Hard to determine, as there's a big gap in the W&B data I have-- nothing between 1960 when the airplane was weighed after a total ("replaced fuselage...") rebuild, and 1988. The 180 gear was installed in 1986 & the airplane (allegedly) weighed, but the W&B sheet from that weigh-in is missing. The 337 for the gear change states that the airplane was weighed, and notes that the arm for the main wheels is now =18.5", as opposed to =22" for the original gear, but doesn't mention actual weight figures. There was not a corresponding airframe logbook entry made to match the 337.
So I don't know the weight of the 180 gear versus the stock gear. The airplane has had assorted radio gear as well as a vacuum system & gyro's installed & later removed. Interesting to note that the airplane weighs the same now with no rear seat, as it did in 1960 with rear seat.
I believe the 1960 weight did not include a full paint job, that's worth 20 or 30 pounds right there-- and the bench rear seat weighs 32.

Eric