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Convert Cherokee 140 to 180?



 
 
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  #11  
Old January 7th 05, 05:44 PM
Aaron Coolidge
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xyzzy wrote:
: What do you mean by a dog? Useful load, speed, what? What kind of TAS
: do you get in cruise? I'd be curious to hear this kind of feedback from
: 140 drivers, especially if they have also flown Warriors, 160s, or 180s
: and can give comparative experience.

Maybe I can help. I have a Cherokee 180 and have flown it 600+ hours. I have
also ferried a Cherokee 140 with the 160HP upgrade back & forth from MA to
FL a few times. I've also flown a Cherokee 140 with 150HP a couple times...

Real world figures with 36 year old airframes (the Cherokees all have METCO
wing tips, the Archer doesn't):
My Cherokee 180, no speed mods, Piper wheel pants, trues out at 141 MPH
at 70 ish % power.
The 160 HP Cherokee 140, no speed mods, Piper wheel pants, trues out at
117 MPH at 70 ish %. It has the AMRD prop tip mod.
The 150 HP Cherokee 140, no speed mods or wheel pants, trues out at
109 MPH at 70 ish %.
An Archer 2 (Old style wheel pants) owned by my friend (we fly in formation)
uses 50 less RPM to get the same TAS as I do.

Climb:
With 1 or 2 people and full fuel I rarely see less than 800 FPM initial
climb in my airplane. I usually see more like 1200 FPM. With the cold
weather, of course, climb performance is even better. In the summer at
gross wt (2400 lbs) I'll see at least 500 FPM.
The 150 HP Cherokee rarely makes 700 FPM, even in the winter. 500 FPM
in the summer is also unusual. (This plane has a tired engine, though.)
The 160 HP Cherokee is a solid 500+ FPM climb in the summer, 2 people and
36 gals of fuel. I haven't flown it in the dead of winter.

Thoughts: The big triangular hole under the Cherokee 140 cowling for
the cooling air exhaust is a tremendous source of drag. I would guess that
the fiberglass cowling on my airplane is the source of most of the speed
change between the 140 and the 180 airplanes. 20 extra HP just shouldn't
change the speed that much. The 20 extra HP also shouldn't make that much
difference in climb performance; I suspect that the much wider chord
prop on the 180 makes a big difference at low speeds. The 180 prop pitch
is also a climb prop pitch, and it can't be changed - it will easily make
redline RPM at any altitude I've flown at. Both 140 aircraft have cruise
props though I don't know the details.

I'd be happy to arrange a demonstration if anyone's in the area.
--
Aaron C. (N9376J)
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  #12  
Old January 7th 05, 06:31 PM
xyzzy
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Aaron Coolidge wrote:

I'd be happy to arrange a demonstration if anyone's in the area.


Where's "the area"?

  #13  
Old January 7th 05, 08:37 PM
[email protected]
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Tim Long wrote:
Our 140 is coming up on 1600 hrs TBO.

We really hate what a dog it is and would like more power.

Planning ahead, we've thought of a few options:

1 - 160 hp conversion (this is almost the minimum we'd do)


If you're already doing an overhaul, this is probably the most
cost-effective option on your list.

2 - Powerflow exhaust (article in Plane and Pilot claims 20% power
improvement - can it be combined with #1?)


This one is good if your current exhaust system needs a lot of work
and replacement parts. It's a bit pricey otherwise. The 140 owners I
know that have installed it are very happy with its performance.

3 - 180 hp conversion

Anybody know about praciticalities, costs of #3 above? I know it

would
require extra $$ for dissimilar engine exchange, STC costs, and
cowling/engine mount mods.


That's the biggie. I know two people who have done the conversion
(was available from Avcon). It's popular out here in the mountainous
west because the 140 is somewhat limited at high density altitudes
found at mountain airports in the summer. Both of the owners were
happy with the resulting performance, but both said that they'd never
do it again. It was more expensive than they thought it would be (lots
of mods required), it took months to complete, they had difficulty
working with the current STC holders (not Avcon) and in the end, they
still had a 140.

John Galban=====N4BQ (PA28-180)

  #14  
Old January 7th 05, 11:19 PM
Chuck
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Thoughts: The big triangular hole under the Cherokee 140 cowling for
the cooling air exhaust is a tremendous source of drag. I would guess that
the fiberglass cowling on my airplane is the source of most of the speed
change between the 140 and the 180 airplanes. 20 extra HP just shouldn't
change the speed that much. The 20 extra HP also shouldn't make that much
difference in climb performance; I suspect that the much wider chord
prop on the 180 makes a big difference at low speeds. The 180 prop pitch
is also a climb prop pitch, and it can't be changed - it will easily make
redline RPM at any altitude I've flown at. Both 140 aircraft have cruise
props though I don't know the details.

I'd be happy to arrange a demonstration if anyone's in the area.


No demonstration, but I'd sure like to talk about those numbers.

I purchased an older 180 ('63) about six months ago. She's great for
her primary purpose -- traning. She can climb at ~1000 even in our
San Antonio summers. Four people, temps in the low 90s this past late
summer and she's still going up at 900FPM. So, I agree with that.

I haven't had the opportunity to look up the exact type, but I
strongly suspect a climb prop (not original -- changed in '92).
That's based on performance. It climbs great compared to a 140 and a
140/160mod I've flown. But my speed is horrible compared to those
numbers you quoted.

At ~70% power, I'm lucky to get it to 110knots. The only way she ever
gets into the yellow is decending with power still on!!!

You mentioned the cowl with the big trangular hole in bottom -- well,
that's what I've got. And to make it worse, there is a lip that stick
downwards around the front of the opening -- creating even more drag.

I also saw someone else mention a replacement cowl that improved
airflow, dual exhaust (instead of muffler in front of the firewall),
and less drag. Is that what you have on your 180???



Chuck
N7398W


  #15  
Old January 7th 05, 11:58 PM
[email protected]
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Chuck wrote:

I also saw someone else mention a replacement cowl that improved
airflow, dual exhaust (instead of muffler in front of the firewall),
and less drag. Is that what you have on your 180???


Chuck,

Your -180 is one of the earliest examples ( a "B" model, I think).
As such, it incorporated the same cowl and restrictive exhaust system
that was used on the lower power models. Beginning with the "C" model
in '65, the -180 cowl was changed to a two-piece fiberglass clamshell
type and the less restrictive dual exhaust was added. With the old
cowl and old exhaust (particularly the latter), I'm not surprised that
you see a cruise of 110 kts. That's not unusual for the earlier
models.

I suppose that you could recowl the plane with a newer version, but
you'd probably have to get some kind of official signoff for a mod like
that (i.e 337 at minimum, field approval worst case). This could be
pretty expensive for minimal returns and there might be issues fitting
the existing exhaust into the newer style cowl.

For the exhaust, Powerflow exhausts are available only for the early
model -180s. It seems that the later model stock dual exhaust was not
very restrictive and didn't warrant a specially modded pipe. If the
-180 Powerflow improvements are similar to those of the -140 with a
similar exhaust, this could improve your engine output significantly.
Of course, the downside is that it's expensive. I'd probably wait
until my exhaust system needed major work, then go with the Powerflow.
John Galban=====N4BQ (PA28-180)

  #16  
Old January 8th 05, 12:52 AM
Aaron Coolidge
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Chuck wrote:
: At ~70% power, I'm lucky to get it to 110knots. The only way she ever
: gets into the yellow is decending with power still on!!!

Hmmm, my airplane cruises a needle width into the yellow arc at 70%.

: You mentioned the cowl with the big trangular hole in bottom -- well,
: that's what I've got. And to make it worse, there is a lip that stick
: downwards around the front of the opening -- creating even more drag.

That lip actually reduces drag quite a bit. I read a kitplanes article
a while ago about cooling drag, and the "Cherokee 140" design is almost the
worst except for that lip. Remove the lip, and the design is the worst
possible. I wonder sometimes if Piper intended to make the airplane draggy
to ensure that it didn't compete with the Comanche 180.

: I also saw someone else mention a replacement cowl that improved
: airflow, dual exhaust (instead of muffler in front of the firewall),
: and less drag. Is that what you have on your 180???

Yes, the Cherokee 180 got the 2-piece fiberglass cown and a dual
muffler design in 1965 IIRC (the Cherokee "C"). Mine is a 1968 Cherokee "D".
(I think the Comanche 180 was dropped around 1965, as well, so the
artificially high drag would no longer be required to limit speeds.)
The cooling air outlet is lower than the rest of the fuselage, so the
cooling airflow is to the rear and below the fuselage. The bottom of my
cowling has no openings except a small hole for the nose gear leg, and
a faired hole for the exhaust pipes. The nose gear leg hole is filled up
behind the oleo strut with a sheel of aluminum.
--
Aaron C. (N9376J)


  #17  
Old January 8th 05, 12:53 AM
Aaron Coolidge
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xyzzy wrote:
: Aaron Coolidge wrote:

: I'd be happy to arrange a demonstration if anyone's in the area.

: Where's "the area"?

Southeastern Massachusetts.
--
Aaron C.
  #18  
Old January 8th 05, 01:39 AM
Bob Noel
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In article , xyzzy wrote:

One significant consideration is useful load. Do you just want the speed
increase? There isn't any way to get a higher useful load.


Interesting, my club has Warriors that have an STC raising the MGW to
2440 lbs. There isn't a similar STC for the 140?


The highest max gross weight for a 140 is 2150lbs (some early 140's had/have
a max gross of 1950 lbs iirc - those can go to 2150 lbs).

--
Bob Noel
looking for a sig the lawyers will like
  #19  
Old January 8th 05, 01:55 AM
Bob Noel
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In article ,
Aaron Coolidge wrote:

Real world figures with 36 year old airframes (the Cherokees all have METCO
wing tips, the Archer doesn't):
My Cherokee 180, no speed mods, Piper wheel pants, trues out at 141 MPH
at 70 ish % power.
The 160 HP Cherokee 140, no speed mods, Piper wheel pants, trues out at
117 MPH at 70 ish %. It has the AMRD prop tip mod.
The 150 HP Cherokee 140, no speed mods or wheel pants, trues out at
109 MPH at 70 ish %.
An Archer 2 (Old style wheel pants) owned by my friend (we fly in formation)
uses 50 less RPM to get the same TAS as I do.


I don't have speed mods, but do have those metcoair tips (or whatever the name
is)

Before I converted my 140 to 160hp, it could cruise at about 105 KTAS at
~4000' and 75% (with wheel pants) but I would usually plan on 100 KTAS.

After converting to 160hp (and repitching the prop to a cruise prop) it'll
do 110+ KTAS down low at 75% (without wheel pants).


Climb:
With 1 or 2 people and full fuel I rarely see less than 800 FPM initial
climb in my airplane. I usually see more like 1200 FPM. With the cold
weather, of course, climb performance is even better. In the summer at
gross wt (2400 lbs) I'll see at least 500 FPM.
The 150 HP Cherokee rarely makes 700 FPM, even in the winter. 500 FPM
in the summer is also unusual. (This plane has a tired engine, though.)
The 160 HP Cherokee is a solid 500+ FPM climb in the summer, 2 people and
36 gals of fuel. I haven't flown it in the dead of winter.


before conversion: my 140 did not climb well, except in the winter. :-)
However, unlike the 150hp 140 example above, mine would regularly
climb at 1000fpm in the winter (initially).

after conversion (even with the cruise prop), it's much stronger in climb.
Easily 1000+ fpm climb even when pushing the nose over for cooling.
In fact, I now have to worry about climbing into the KBOS Class B airspace
when departing KBED to the west. I never had to worry had to worry about
that before.

--
Bob Noel
looking for a sig the lawyers will like
  #20  
Old January 8th 05, 03:55 AM
Prime
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xyzzy posted the exciting message
:

Tim Long wrote:

Our 140 is coming up on 1600 hrs TBO.

We really hate what a dog it is and would like more power.


I fly warriors in a club and have been toying with the idea of

buying a
140. I don't know if I'd be happy with less plane than I am

flying now,
but for 99% of the flying I do, a 140 would be sufficient, at

least on
paper. Hell, for 90% of the flying I do an Ercoupe or a

Tripacer would
be sufficient, but I'm not willing to go that small and

limited since
the 140 isn't THAT much more expensive to buy.

What do you mean by a dog? Useful load, speed, what? What

kind of TAS
do you get in cruise? I'd be curious to hear this kind of

feedback from
140 drivers, especially if they have also flown Warriors,

160s, or 180s
and can give comparative experience.


It's a dog even compared to a C172. The ceiling sucks and the
climb rate sucks. If you get near gross it doesn't climb worth a
damn. In the desert on a hot summer day we can't get much over
9000', and that doesn't buy a lot when you're trying to get to
OSH or otherwise east of the Rockies. Try taking off from any
runway when the density altitude is 4000' (not that high around
here) or so - you need something like 4000' feet of runway if
you're hot and heavy.

It's a dog in that we want better performance for ceiling and
takeoff distance. While speed and load carrying would be nice,
they are not the biggest issue!

Prime
 




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