 |
Matronics Email Lists
Web Forum Interface to the Matronics Email Lists
|
| View previous topic :: View next topic |
| Author |
Message |
wnorth(at)sdccd.edu
Guest
|
 Posted: Mon Mar 03, 2008 6:48 am Post subject: Prop indexing |
 |
|
Load on the propeller is not symetrical as the blades travel around the
circumfrence, and the crankshaft is subjected to accelerating and
decelerating loads as it spins around. The phase of these is tested for
certified prop/engine combinations at the design indexing, but it likely is
not tested at other indexing combinations.
Just because it is smoother to your butt does not mean it is smooother to
your engine, or to engine parts within.
You takes your chances when using alternate indexing.
| | - The Matronics RV-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV-List |
|
|
|
| Back to top |
|
 |
sportav8r(at)gmail.com
Guest
|
| Posted: Mon Mar 03, 2008 9:42 am Post subject: Prop indexing |
|
|
Lycoming factory told me to have at it with indexing if I wanted to; they had no concerns with it.
-Bill / Stormy
On Mon, Mar 3, 2008 at 9:44 AM, Wheeler North <wnorth(at)sdccd.edu (wnorth(at)sdccd.edu)> wrote:
[quote]--> RV-List message posted by: "Wheeler North" <wnorth(at)sdccd.edu (wnorth(at)sdccd.edu)>
Load on the propeller is not symetrical as the blades travel around the
circumfrence, and the crankshaft is subjected to accelerating and
decelerating loads as it spins around. The phase of these is tested for
certified prop/engine combinations at the design indexing, but it likely is
not tested at other indexing combinations.
Just because it is smoother to your butt does not mean it is smooother to
your engine, or to engine parts within.
You takes your chances when using alternate indexing.
[b]
| | - The Matronics RV-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV-List |
|
|
|
| Back to top |
|
|
larywil(at)comcast.net
Guest
|
| Posted: Mon Mar 03, 2008 2:38 pm Post subject: Prop indexing |
|
|
At 09:44 AM 3/3/2008, you wrote:
| Quote: |
<<<Just because it is smoother to your butt does not mean it is smooother to
your engine, or to engine parts within.>>>
You takes your chances when using alternate indexing.
|
Wheeler,
I have heard this several times before over the past 12 years on the
list. Several knowledgeable pros have said the same thing. Propeller
engineering
is a science of its own, and usually should be left to pros. I can
give many of you a good example. My RV-4, with it's IO-360, Hartzell
C/S prop happens to run smoothest (to my butt) at 20-21" manifold
pressure and 2100-2300 RPM !! Those of you with my prop know that
this RPM range is prohibited/ restricted because it produces a
vibration mode that causes permanent and additive damage to the prop.
You can't see it, and common sense and "butt feel" would never lead
you to suspect this damage is occurring.
I would love to reduce the vibration of my IO-360, but I would only
go with proven methods such as dynamic balancing and improved engine
mounts, or any other proven-to-be-safe method.
I lost my first RV-4 from a broken prop due to a bird strike. That's scarry.
Don't mean to preach. Just passing along precautions to the list.
Louis
| | - The Matronics RV-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV-List |
|
|
|
| Back to top |
|
|
ceengland(at)bellsouth.ne
Guest
|
| Posted: Mon Mar 03, 2008 3:05 pm Post subject: Prop indexing |
|
|
I thought I sent this to the list, but it seems I just clicked 'reply'
to an off-list email from Bill.
Anyway, here's the word from Lycoming, for those who are understandably
worried about deviating from the norm with props:
copied message:
If you get motivated to spend the extra time & money, the Lyc 'Service
Instruction' is on this page of the Lycoming web site (I got lucky):
The document subject is 'Propeller Flange Bushing location':
| | - The Matronics RV-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV-List |
|
|
|
| Back to top |
|
|
kahuna
Joined: 02 Feb 2007
Posts: 93
|
| Posted: Mon Mar 03, 2008 11:49 pm Post subject: Prop indexing |
|
|
Some information you might find useful with regards to indexing.
This was my experience with real data. In fact lots of data.
Enjoy,
Mike
http://mstewart.net/super8/propclock/index.htm
[img]cid:1__=08BBFE91DFB905978f9e8a93df938(at)us.ibm.com[/img]"Wheeler North" <wnorth(at)sdccd.edu>
[img]cid:3__=08BBFE91DFB905978f9e8a93df938(at)us.ibm.com[/img]
To
[img]cid:3__=08BBFE91DFB905978f9e8a93df938(at)us.ibm.com[/img]
<rv-list(at)matronics.com> [img]cid:3__=08BBFE91DFB905978f9e8a93df938(at)us.ibm.com[/img]
cc
[img]cid:3__=08BBFE91DFB905978f9e8a93df938(at)us.ibm.com[/img]
[img]cid:3__=08BBFE91DFB905978f9e8a93df938(at)us.ibm.com[/img]
Subject
[img]cid:3__=08BBFE91DFB905978f9e8a93df938(at)us.ibm.com[/img]
Prop indexing [img]cid:3__=08BBFE91DFB905978f9e8a93df938(at)us.ibm.com[/img][img]cid:3__=08BBFE91DFB905978f9e8a93df938(at)us.ibm.com[/img]
--> RV-List message posted by: "Wheeler North" <wnorth(at)sdccd.edu>
Load on the propeller is not symetrical as the blades travel around the
circumfrence, and the crankshaft is subjected to accelerating and
decelerating loads as it spins around. The phase of these is tested for
certified prop/engine combinations at the design indexing, but it likely is
not tested at other indexing combinations.
Just because it is smoother to your butt does not mean it is smooother to
your engine, or to engine parts within.
You takes your chances when using alternate indexing.
=====================================
tor?RV-List">http://www.matronics.com/Navigator?RV-List
=====================================
FORUMS -
tp://forums.matronics.com
=====================================
Site -
bsp; -Matt Dralle, List Admin.
bution">http://www.matronics.com/contribution
=====================================
| | - The Matronics RV-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV-List |
|
| Description: |
|
| Filesize: |
105 Bytes |
| Viewed: |
1512 Time(s) |
|
| Description: |
|
| Filesize: |
1.23 KB |
| Viewed: |
1511 Time(s) |
|
| Description: |
|
| Filesize: |
45 Bytes |
| Viewed: |
1512 Time(s) |
|
|
|
| Back to top |
|
|
wnorth(at)sdccd.edu
Guest
|
| Posted: Wed Mar 05, 2008 6:11 pm Post subject: Prop indexing |
|
|
All great comments, and some really interesting data.
However, possibly some might have missed the gist of my post. The prop has
varying loads upon it in torque and the crankshaft also has varying loads on
it in torque.
The longer the crankshaft (and more power it is producing) the more likely
that the aft end might be doing something different than the front end, and
this will not be measured by external sensing.
Drive gears, crankshafts, cam shafts and magnetos throughout the years have
occasionally had problems that were traced back to this. The fix was varied
and in some cases called for highly modified counter weighted crankshafts.
Somewhere, years ago, pre-internet, I saw footage of a crankshaft flexing
30degs from stem to stern at a high power/rpm setting as it went into
longitudinal resonance. It is really amazing to see that tough a piece of
steel turn into a wet noodle.
There are many things that can be additive or not in a resonance problem,
but cyclical pulsing of the load and of the input are big ones. By
reindexing you will be moving the phase of those load/input cycles and the
engine may get smoother. But is that because you got lucky or because the
crankshaft is now absorbing that vibration in an unsafe manner???
The shorter four cylinder engines seem to not be as prone to this, but I'm
pretty sure that the testing which was done on your engine was done in one
indexed position, if indexed on any other position then you are conducting
test flights every time you fly it.
If doing this makes you less uncomfortable than the slightly increased
vibration did, then you are an adult capable of decision making. In my mind
it an easy choice, but then I have a solid nose crank that seems to be about
as smooth as it gets, and I all I did was build the engine right before I
screwed a prop on it.
Condolences to friends, colleagues and family of the lost ones in FL. While
we try our best to make better what we can, sadly there is no cure for a
millisecond of exceptionally bad luck.
| | - The Matronics RV-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV-List |
|
|
|
| Back to top |
|
|
|
|
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum
|
Powered by phpBB © 2001, 2005 phpBB Group
|
Get Email Distribution Too!
FAQ
Search
Memberlist
Usergroups
Register
Profile
Log in to check your private messages
Log in
