Received-SPF: pass
 receiver=logan.com; client-ip=207.217.121.226; envelope-from=Dastaten@earthlink.net
Message-ID: <4143EF61.9080107@earthlink.net>
Date: Sun, 12 Sep 2004 01:40:33 -0500
From: David Staten <Dastaten@earthlink.net>
Reply-To:  Dastaten@earthlink.net
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.4) Gecko/20030624 Netscape/7.1 (ax)
MIME-Version: 1.0
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Re: Engine off the floor
References: <list-406985@logan.com>
In-Reply-To: <list-406985@logan.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit

I am more worried about the stamped sheetmetal pan than anything else, 
Ed... Maybe I am misunderstanding your intentions, but you are going to 
weld the ears to the pan? or are you going to just bolt them to the 
engine in the corners (sandwiching either them, or the pan, against the 
block)..? I'm sure the bolts would be fine, since we use similar bolts 
in the more common "sandwich" mounts that are being marketed for the 
rotary, and if there is a concern, use longer corner pieces that recruit 
more bolts to the cause. Wouldn't it be possible to use a sandwich plate 
of your own using the steel plate you are considering, but having it 
mostly cut out within the dimensions of the block/pan (almost like a 
gasket shaped plate with the ears on it.. )..
 
Dave

Ernest Christley wrote:

> David Staten wrote:
>
>>
>>
>> Ernest Christley wrote:
>>
>>> In the likely chance that I'm missing something, I'm all ears 8*)
>>
>>
>>
>> What are you trying to accomplish by NOT using a sandwich mount.. 
>> save money? Save weight? 
>
>
> Well...yeah.
>
>> If you aren't conducive to using a sandwich mount like the others, I 
>> would err towards using the original mounting hardpoints on the 
>> engine block, or use some of the other 10x1 stud holes... AND perhaps 
>> the pan based mounts for some sort of torsional stability.. but NOT 
>> the proposed pan mounts as sole support. You are dealing with not 
>> only torque (which you appear to be cognizant of) but also G-loading 
>> (both positive and negative)... I would be interested in seeing what 
>> this sort of pan mount would withstand with regards to ultimate 
>> g-loading.. Normal Category is 3.8 g if I remember (and thats 
>> considered normal bounds.. I dont recall what the design factor is 
>> above and beyond that. Aerobatic is something like +9 and -3 or -6... 
>> it would be interesting if this 250 pound motor on a pan mount will 
>> remain in position without deformation at loading approaching 1000 
>> (normal) or 2000 (approaching aerobatic) pounds of load x factor.
>>
>
> Normal Category is certified to 3.8g positive and negative is 1.52g.
>
> For airplanes, the standard design safety factor is 1.5.  I believe 
> most of the composite designs use a factor of 2.0, due to the wide 
> disparity in quality between hand layups made by different people (but 
> don't take my word on that one.)
>
> Not worried about aerobatic manuevers, since I'm putting it in a 
> non-aerobatic, VFR aiplane, but my design criteria has been 10g with a 
> working weight of 350lb.
>
>> Engine mounts are a major structural item, and failure WILL likely 
>> mean loss of the aircraft, and landing in an uncontrolled manner 
>> (engine comes off and then you have a really unfavorable CG).. this 
>> is where you want to OVERBUILD (if you are going to err), not 
>> underbuild.. a stamped oil pan is hardly a structural item....
>>
>> Fly SAFE,
>> Dave
>>
>
> Overbuilding is definitely one approach, but not the one I'd prefer to 
> use.  The problem is that just adding more metal won't necessarily 
> make the structure stronger, but it ALWAYS makes it heavier (and more 
> expensive).  Very often it can actually make the structure weaker 
> (though, a full plate wouldn't).
>
> That being said, I have not set a goal to err or underbuild.  I have 
> set a goal to eliminate several pounds of expensive steel (or 
> aluminum), IF POSSIBLE.  A stamped oil pan can be as structural as 
> anything else, IFF it is used within it's capabilities.
>
> I have been having trouble finding some information.  Unfortunately, I 
> don't have the luxury of hanging weights from the bottom of my engine 
> until a bolt gives up, so I'm looking for published numbers.  The 
> closest I've been able to find is that a 6mm bolt should have a load 
> rating of at least 650lbs (the load ratings for is eye bolts, and 
> there is no way to tell if the limitation is on the eye or the bolt).  
> Does anyone have a table of working load limits for various size bolts?
>