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pitts_pilot(at)bellsouth.
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 Posted: Sat Nov 27, 2010 7:26 am Post subject: engine mount ears and attaching the Bendix Throttle body |
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I'm definitely no expert, but thought I'd comment anyway.
On 11/27/2010 10:01 AM, John Gonzalez wrote: | Quote: | Hi Bob,
I have all the manuals and I am still confused. The service table of limits says, "standard torque unless otherwise listed." That means all those other lised items in Section V have special requirements.
The beginning of section V lists, Studs. Although is uses the word studs, it doesn't say, Engine mount ear studs.
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That would imply that a stud is a stud ...... and we're talking fasteners here!!!
| Quote: |
Looking at the parts manual, the nomenclature spells out these four bolts, sixteen total, eminating out of the case, which attach to the engine mount ears as, STUDS.
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OK. Sounds good to me.
| Quote: |
The service table of limits states Minimum driving torque in Inch/pounds with very low values. These low values would make no sense for these engine ear studs.
One would think that these studs holding the engine mount ears would be listed, as they would need to be very strong, handle vibration and heat. So I am assuming that they have the standard torque for a 3/8-16 bolt of 30 Ft/Lbs. But under section V, 3/8-16 studs are listed as 50 Inch/Lbs...this is a huge difference!!!
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I haven't looked, but I think these studs are in shear, not tension???? Please correct me if I'm wrong. No matter how tight you get the stud, it won't change it's 'holding power'. It did surprise me the difference in torque on bolts Vs. studs though.
| Quote: |
I am simply trying to be very thorough as I have broken bolts and screws with these long torque wrenches before and these studs are very important.
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Very important indeed. If you're still concerned, use some Loctite ...... or lock nuts.
Linn
[quote]
Thanks,
John
> Subject: Re: engine mount ears and attaching the Bendix Throttle body
> From: bobturner(at)alum.rpi.edu (bobturner(at)alum.rpi.edu)
> Date: Fri, 26 Nov 2010 22:01:03 -0800
> To: rv10-list(at)matronics.com (rv10-list(at)matronics.com)
>
> --> RV10-List message posted by: "Bob Turner" <bobturner(at)alum.rpi.edu> (bobturner(at)alum.rpi.edu)
>
> You need to get hold of the Lycoming manual. (search on line). Many of the torques recommended by Lycoming are higher than standard for AN. I don't know why. Maybe because they also use lock washers? Or the high vibration levels?
>
> You got 2 gaskets so if you use Van's part to hold the cable ends, it goes between the throttle body and the engine, with one gasket on either side.
>
> Bob
>
> --------
> Bob Turner
> RV-10 QB
>
>
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=321117#321117
>
>
>
> <=======================
&g===
>
>
>
[b]
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Kellym
Joined: 10 Jan 2006
Posts: 1705
Location: Sun Lakes AZ
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| Posted: Sat Nov 27, 2010 7:36 am Post subject: engine mount ears and attaching the Bendix Throttle body |
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As to your mount ears...the table you are looking at for minimum driving
torque I believe is for installation of studs into the case. You can
always call Lycoming. I expect the 30 ft lbs you are looking at for the
nuts securing the ears to the studs.
You can always call Lycoming.
On 11/27/2010 8:01 AM, John Gonzalez wrote:
| Quote: | Hi Bob,
I have all the manuals and I am still confused. The service table of
limits says, "*standard torque unless otherwise listed*." That means
all those other lised items in Section V have special requirements.
The beginning of section V lists, *Studs*. Although is uses the word
studs, it *doesn't* say, *Engine mount ear studs.*
Looking at the parts manual, the *nomenclature *spells out these four
bolts, sixteen total, eminating out of the case, which attach to the
engine mount ears as, *STUDS*.
The service table of limits states Minimum driving torque in
*Inch/pounds* with very low values. These low values would make no
sense for these engine ear studs.
One would think that these studs holding the engine mount ears would
be listed, as they would need to be very strong, handle vibration and
heat. So I am assuming that they have the standard torque for a 3/8-16
bolt of 30 Ft/Lbs. But under section V, 3/8-16 *studs* are listed as
50 Inch/Lbs...this is a huge difference!!!
I am simply trying to be very thorough as I have broken bolts and
screws with these long torque wrenches before and these studs are very
important.
Thanks,
John
> Subject: Re: engine mount ears and attaching the Bendix
Throttle body
> From: bobturner(at)alum.rpi.edu
> Date: Fri, 26 Nov 2010 22:01:03 -0800
> To: rv10-list(at)matronics.com
>
>
>
> You need to get hold of the Lycoming manual. (search on line). Many
of the torques recommended by Lycoming are higher than standard for
AN. I don't know why. Maybe because they also use lock washers? Or the
high vibration levels?
>
> You got 2 gaskets so if you use Van's part to hold the cable ends,
it goes between the throttle body and the engine, with one gasket on
either side.
>
> Bob
>
> --------
> Bob Turner
> RV-10 QB
>
>
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=321117#321117
>
>
>
> <=======================
&g===
>
>
>
*
*
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_________________
Kelly McMullen
A&P/IA, EAA Tech Counselor # 5286
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Bob Turner
Joined: 03 Jan 2009
Posts: 885
Location: Castro Valley, CA
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| Posted: Sat Nov 27, 2010 2:28 pm Post subject: Re: engine mount ears and attaching the Bendix Throttle bo |
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The whole business of torquing fasteners is black magic as far as I'm concerned. It's amazing it works at all. Remember what you want is a certain amount of bolt stretch (pre-load). But most of the torque is needed to overcome friction. So any oil on the threads will make the stated torque value way off. McCauley props are put on with relatively low torque but also with a specified lubricant. I have to think that the star washers Lycoming uses makes a difference in the requirements too.
My guess (and it is just a guess): putting in studs involves no preload, so the stated 50 in lbs may be what's needed to engage a certain number of threads. It may also be what's needed to hold against the 30 ft lbs when the nut is put on, and the stud is loaded against the threads. Worst case, when you install the nut, the stud will turn in more until it too is at 30 ft lbs.
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_________________
Bob Turner
RV-10 QB |
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