Re: pteros have lift-off

[jrc <jrccea@bellsouth.net>]

Comments inserted.
JimC
----- Original Message ----- 
From: "David Peters" <davidpeters@att.net>
To: "jrc" <jrccea@bellsouth.net>
Cc: <dinosaur@usc.edu>
Sent: Tuesday, January 13, 2009 6:38 PM
Subject: Re: pteros have lift-off


> ......Those taxa are no longer the  issue. I'm interested in the 
> pterosaurs with shorter legs, weaker  pectoral girdles and much, much 
> longer wings.

Based on the image of your reconstruction of Istiodactylus that you sent me 
yesterday (thanks, by the way), I see no apparent problems with quad launch 
for the critter, though I would pose it somewhat differently than you do --  
with the launch caveat that I couldn't clearly see the humerus and coracoid 
in your image, but qualitatively I don't expect them to be unusual enough to 
present a problem.  Send the dimensions and mass, and I'll run the numbers. 
I use a different and perhaps more time-consuming  technique than Mike, so 
it may take me a while to get around to it.  I've noticed from our off-line 
comparisons that Mike and I get much the same results, so my hunch is that 
his quicker procedure will suffice.

> , but certain segments of it, such as when  the wings are vertical, or 
> nearly so, during terrestrial locomotion  and immediately following a 
> lift-off, are simple.

I'm glad to know that. :-)  It seems to me that you configure the forelimbs 
quite differently than I do during the launch.  For example, you don't seem 
to load them into adverse mechanical advantage prior to releasing them.  It 
may be that the joint locii are not so simple as you assume?  Or, are you 
saying that they are more simple than I assume?

> All I want now is minimum flight speed and apogee as a multiple of  the 
> unit specified by CG height at the beginning of the leap.

Since minimum flight speed and apogee aren't a simple multiple of the unit 
specified by CG height above the ground at the beginning of the leap, how 
does this help?  It sounds again like you are assuming a significantly 
different path for the long bones of the forelimb than Mike and I do.

> Been  gone all day. No reply, so far, to those queries.

Day job sometimes interferes with non-paying stuff  :-(
I just  now saw your post, so was unable to respond more quickly.
JimC