Prop bolts not AN bolts?
Bruce Bockius
35-40 ft*lbs. My kit manufacturer says to torque 3/8" AN6 bolts to 160
in*lbs, which is 13 ft*lbs by my calculations. Are the bolts supplied
by Warp different than standard AN6 bolts? Why the big difference in
torques?
Thanks,
Bruce
********************
Bruce Bockius
http://www.xprt.net/~elrond/zodiac
ls
with a strong metallic, musty smell) and an "X" stamped somewhere on the
head (unless they're precision AN bolts which, I believe, have a diamond
instead). I'm not familiar with the Warp, but, IMO, prop fasteners should be
AN grade or better.
Just Say No to hardware store grade 8's (which I'm sure Warp did not supply
you)....
Lucien S.
PP-ASEL.
Captain America IV.
Bruce Bockius <elr...@xprt.nospam.net> wrote in message
news:39688213...@xprt.nospam.net...
Al Mills
> Just Say No to hardware store grade 8's (which I'm sure Warp did not
supply
> you)....
>
> Lucien S.
differences. What about that? I'd like to know too.
AL
Juan Jimenez (TeamB)
Bob Moore
>Just Say No to hardware store grade 8's (which I'm sure Warp did not supply
>you)....
Hardware store bolts are normally not even close to grade 8, usually less
than grade 3.
I have been flying with "Fastner Store" Grade 8's on my prop for 5-6 years
after the AN's (about grade 5) all sheared simultaneously and left me with-
out a prop.
And yes.... I'm running about 25 ft-lbs of torque on them.
Bob Moore
1/2 VW powered MiniMax
ls
assurance that the bolt and nut meets a particular standard.
I use AN stuff on my plane and have never had a failure (although lots of
bent ones). BTW, ironically, the compression strut/LE tube connection in the
wing on my plane is done with long grade 5 bolts! And this is a Jesus joint
(although fortunately a very well designed joint), since the forward wing
support wires attach to the wing here via tangs. The bolts used are good
quality grade 5's, but I still wonder why AN-grade hardware isn't used here,
as it is on the TE/compression strut attach joints...
A friend of mine is rebuilding the brakes on his Porsche; he's attaching the
brake discs on with MS grade stuff - talk about a whup-ass bolt! And
something like 7 bucks a pop, but very strong, consistent bolts. And they
shore are shiney and purty too......
Lucien S.
PP-ASEL.
Captain America IV.
> Hardware store bolts are normally not even close to grade 8, usually less
Ron Webb
>
> Hardware store bolts are normally not even close to grade 8, usually > less than grade 3.
> I have been flying with "Fastner Store" Grade 8's on my prop for 5-6 > years after the AN's (about grade 5) all sheared simultaneously
The published "specs" for the stuff grade 8 bolts are made from, and that for
A/N hardware ARE comparable - about 125KPSI. "Hardware store" bolts of up to
180KPSI can be had.
The differance is in the threads and shank. The threaded section on A/N is
short, so that hopefully the shear loads will be applied to the unthreaded part.
Also the threads on A/N are rolled (pressed under high pressure) instead of cut.
This means no sharp corners (stress risers), and the grain structure is not
interrupted.
Is grade 8 good enough for most things on a homebuilt? Probably... but why risk
it for the small savings? I took my quicksilver ultralight apart a few weeks
ago. The MAIN bolt that holds the downtubes to the root tube was pretzelled
good. It was A/N, and simply bent. Who knows what a grade 8 equivilent would
have done. It would be a bad feeling to have your airplane come completely apart
in mid air...
As for why the torque differance... I don't know in your case, but consider
this:
When you torque a bolt, you are applying a pre load, and thus reducing the load
that the bolt can take in that dimension. You get in return, the parts held
together tighter, and less chance of the bolts coming out.
In a critical application, I don't see how a "one size fits all" torque spec can
be expected to be optimum in all cases.
The standard torque for the A/N bolt that you quote is such a thing. To
paraphrase Mr Spock: "it is the beginning of wisdom...not the end"
BD5ER
be a non question. Do the bolts supplied by Warp Drive have the same thread
pitch as AN bolts? AN bolts have finer pitch than your ordinary bolts and
require less torque to get the same clamping preasure. This MIGHT be the
differance.
Fred Fillinger
8mm bolts -- prop/class 8.8.
Warp says 14.5 ft. lbs., but of course 8mm is
smaller than 3/8". Then re-torque every 5-10
hours (yuk). You might just call Warp Drive, but
I suspect their's may have more tensile strength.
The kit mfr is correct for AN6's by my reference
(well, 160-190 actually).
Fred F.
Bruce Bockius wrote:
>
> My Warp Drive comes with 3/8" bolts and directions to torque them to
> 35-40 ft*lbs. My kit manufacturer says to torque 3/8" AN6 bolts to 160
> in*lbs, which is 13 ft*lbs by my calculations. Are the bolts supplied
HRH
>:::
> As for why the torque differance... I don't know in your case, but consider
> this:
>
> When you torque a bolt, you are applying a pre load, and thus reducing the load
> that the bolt can take in that dimension. You get in return, the parts held
> together tighter, and less chance of the bolts coming out.
> In a critical application, I don't see how a "one size fits all" torque spec can
> be expected to be optimum in all cases.
Umm, well, actually, I don't think that's how bolts work.
The purpose of the torque spec is NOT to keep the bolt from coming out.
The preload does NOT reduce the axial load the bolts can take.
The purpose of the torque spec is, among other things, intended to
establish a preload that is GREATER than the maximum expected operating
load.
The reason this doesn't exactly subtract from strength in the stressed
dimension is perhaps a little bit subtle. Consider an axially loaded
bolt with a preload of 150% of the working load. The working load
is trying to stretch the bolt. However, the bolt already has strain =
preload / E. (Where E = Young's modulus.)
The force needed to maintain the preload comes directly from the
strain ("stretch") in the bolt and is proportional to it.
Now, until the load EXCEEDS the preload, the bolt just isn't going to get
any longer (no more strain) and so **it doesn't "feel" the load at all**!
The preload neatly prevents any flexing, so, no work hardening, no fretting,
no cycling toward any fatique limits, etc, ... THAT'S what the preload is
for, and why it doesn't subtract from the load-carrying capacity of the bolt.
quod erat demonstrandum :-)
HRH
P.S. You actually were slightly right. Compression of the bolted object
causes the bolt to "feel" a fraction of the load, varying with stiffness of
the bolt vs stiffness of the object. This is one reason why very studly
bolts have intentionally narrowed flank sections, so MORE of the strain is
spread through the bolt, and not in the threads, the head, the thing being
bolted, etc; it makes the whole thing more ideal, easier to analyze, lighter...
Oh yeah, this gives you a hint as to why torque specs vary, the original
question. You don't need more than the highest expected load, and you have
to worry about compressing or crushing the bolted thing. It also varies a
LOT depending on how (whether!) you oil the threads first. In a critical
application, you actually specify the kind of oil used on the threads, because
you are trying to nail a specific amount of tension and you don't want torque
vanishing into thread friction.
Jim
probably like 20-25 ft. lb. where 5 lams wood prefer 18-20 ft. lb. That
is based on standard SAE 2 hub and if nuts are used behind the hub it
wood prefer 20 rather than 40 if its a shear nut rather than a tension
nut (shear nuts are thinner and have fewer threads to grip them). The
primary locking feature of the prop bolts is torque and redundency is
saftey wire or plastic in the nut threads. This is all lieback
technology and is opinion based on application and use. It is not law.
just an opinion mind-ya
Al Mills wrote:
>
> > Just Say No to hardware store grade 8's (which I'm sure Warp did not
> supply
> > you)....
> >
Dan Horton
> Are the bolts supplied by Warp different than standard AN6 bolts? Why the
big difference in torques?<
I think that's a terrific question. However, you're the only one here who
knows what bolts they supplied. Do they have 3 slashes on the head or 6? I
think Warp uses Grade 8's (6 slashes), which are 150,000 psi material (AN's are
120,000) and are normally torqued to about 52 ft-lbs in a fine thread.
I assume the six 3/8" bolts are to clamp the prop hub to the engine
flange. Note I said "clamp". The idea is to drive the prop with friction
between the flange and the prop hub. There should be no relative movement
between the two, and no shear loads on the bolts. The drive lugs found on an
SAE 1 or 2 hub are insurance; they insure that shear loads are not applied in
the area of the bolt threads in the event that clamping force is insufficient.
Using a bolt that allows a higher clamping force is a good deal. Not possible
with a wood prop, fine for the Warp with it's metal hub. That may explain the
application of different bolt types with different torques.
Having said all that, we arrive at your second question, which is
something I wanna know too. Why do AN's and SAE/ASTM bolts have such different
torque recommendations? Check the recommended torques for any AN bolt and then
check the same size and pitch in a Grade 5. They are both 120,000 psi, so it's
not an unreasonable comparison. You'll find a higher torque, often double, for
the Grade 5. Why?
Dan Horton
rich...@techhead2.com
>
>>
>> Hardware store bolts are normally not even close to grade 8, usually > less than grade 3.
>> I have been flying with "Fastner Store" Grade 8's on my prop for 5-6 > years after the AN's (about grade 5) all sheared simultaneously
>
>The published "specs" for the stuff grade 8 bolts are made from, and that for
>A/N hardware ARE comparable - about 125KPSI. "Hardware store" bolts of up to
>180KPSI can be had.
It's easy to tell, look at the radial markings on the heads of the
bolts. six marks means grade 8 and three means grade 5. Standard
hardware sold in most stores is grade 2, about as soft as a carriage
bolt.
>
>The differance is in the threads and shank. The threaded section on A/N is
>short, so that hopefully the shear loads will be applied to the unthreaded part.
You would be hard pressed to find any cut threads on any commercial
hardware today. Almost everything is rolled, not for better
structure, but because it's faster and cheaper
>
>Also the threads on A/N are rolled (pressed under high pressure) instead of cut.
>This means no sharp corners (stress risers), and the grain structure is not
>interrupted.
>
>
>Is grade 8 good enough for most things on a homebuilt? Probably... but why risk
>it for the small savings? I took my quicksilver ultralight apart a few weeks
>ago. The MAIN bolt that holds the downtubes to the root tube was pretzelled
>good. It was A/N, and simply bent. Who knows what a grade 8 equivilent would
>have done. It would be a bad feeling to have your airplane come completely apart
>in mid air...
Now you've hit on the difference between grade 8 and grade 5. The
grade 8 has a higher tensile strength, but being harder, would crack
with much less bending. It would take more to bend it, but would
crack with less bend.
>
>As for why the torque differance... I don't know in your case, but consider
>this:
>
>When you torque a bolt, you are applying a pre load, and thus reducing the load
>that the bolt can take in that dimension. You get in return, the parts held
>together tighter, and less chance of the bolts coming out.
>In a critical application, I don't see how a "one size fits all" torque spec can
>be expected to be optimum in all cases.
>
The 35 - 40 ft/lbs quoted is within the 35 -42 ft/lbs that is a
standard rating for a 3/8"-16 thread. But for a grade 8 bolt going
into a high strength nut or other part. It's usually set at 2/3 of
what it will take to strip either the bolt or the nut/other part.
Using a grade 8 bolt threaded into a part made of un-hardened 1018, as
an example, the torque would be considerably below this, perhaps as
much as 60% lower. A fine thread bolt would have considerably lower
torque spec, but the torque spec would yield the same clamping force.
This clamping force is what is subtracted from the tensile strength to
give a figure of the load the bolt will hold, and while it may seem
considerable, it's usually a small percentage of the total the bolt
can hold.
Richard B.
Craig C.
> Having said all that, we arrive at your second question, which is
>something I wanna know too. Why do AN's and SAE/ASTM bolts have such different
>torque recommendations? Check the recommended torques for any AN bolt and then
>check the same size and pitch in a Grade 5. They are both 120,000 psi, so it's
>not an unreasonable comparison. You'll find a higher torque, often double, for
>the Grade 5. Why?
The torque loads for NAS/MS/AN bolts and screws are based on type of
service the fastner is designed for. An example is the NAS 6xxx series
bolts. They are designed strictly for service in a shear load. The
specs do not allow them to be used in a tensile load application. A
different example is the NAS 158x series screw. they are designed for
either shear or tensile loads. When you look them up in the spec, not
only do they give a shear rating, but they give a tensile rating with
particular nuts. One of these days, I'm going to scan in all my
hardware spec sheets and manufacturing data sheets and put it all on
CD so that it can easily be copied...
Craig C.
Dan Horton
> One of these days, I'm going to scan in all my hardware spec sheets and
manufacturing data sheets and put it all on CD so that it can easily be
copied...<
Oh boy, I'd love to have a copy of that. Can you tell us a source so a
fellow can obtain his own?
>The torque loads for NAS/MS/AN bolts and screws are based on type of service
the fastener is designed for.<
Sounds like the torque spec for AN's was set based on some arbitrary
criteria for safe use in the field, ie, little preload because 'they" couldn't
be sure if users knew or cared about determining the type of load, in
particular mixed loads. Perhaps MS/NAS specs, which came later, were more type
specific. If that is true, then a AN bolt installed in a clamping high-cycle
tension application should indeed be torqued to a higher preload than the
torque charts indicate. Can't bet on it without data, but I would love to
know.
Dan Horton
Craig C.
>
> Oh boy, I'd love to have a copy of that. Can you tell us a source so a
>fellow can obtain his own?
>
>
Ryan Young provided me with this link to search current standards:
http://www.dtic.mil/stinet/str/dodiss4_fields.html
All the documents are in PDF format so that they are easily searched
and printed.
I'll see about taking all of my standards and process stuff up to my
folks house in the next day or so and scan it in. I don't know what
kind of format I can put it in, but as soon as I get it done and some
things cleaned up on it, I'll e-mail you a copy. I know it will be a
pretty big set of files, but I'll do what I can to compress them.
Craig C.
Dan Horton
>I know it will be a pretty big set of files, but I'll do what I can to
compress them.<
That would be terrific, and thank you. I have WinZip if that helps. And
thanks for the link, I'll check it out.
Dan
ls
risk
> it for the small savings? I took my quicksilver ultralight apart a few
weeks
> ago. The MAIN bolt that holds the downtubes to the root tube was
pretzelled
> good. It was A/N, and simply bent. Who knows what a grade 8 equivilent
would
> have done. It would be a bad feeling to have your airplane come completely
apart
> in mid air...
A little off topic, but this is one of very few (maybe two or three) joints
on the Quick that puts a shear load over a considerable distance of the bolt
(i.e. the surfaces applying the force are not mating surfaces or are
seperated by floating components such as washers) so you definitely want an
AN bolt there. Still, bending of this bolt is not that common, usually only
after a series of hard landings, or lots of operation off a very bumpy grass
field. There is usually only a saddle seperating the downtube from the RT
surface, so only a little less than 1/4" of bolt is involved in the shear
load.
The other Jesus joint on the Quick with this problem is right behind that
one, the seat support down tube-to-root tube attachment point. On older
quicks that were originally designed with the hard prop drive shaft coupler
but are upgraded to the flex coupler, this attachment point is usually
shimmed outwards quite a ways with washers placed under the saddle so the
support tube can clear the new (larger diameter) coupler. The net effect is
the shear loads imposed by the seat support tube being spread out over
almost a 1/2" to 3/4" length of bolt!
The fix here is to drill a new hole further back in the root tube for the
down tube attach point (newer quicks that already came with the flex coupler
already have the hole located further back on the root tube, I believe) and
bend the tube (or flip it around and attach it on the other side of the RT)
to allow it to sit flush against the RT with only a saddle underneath and
still clear the coupler. This'll thankfully require a shorter bolt also.
This will also move the seat forward and up, so you'll have to readjust the
seat itself.
Just something to check when you go to put it back together.
I ran into this situation during the rebuild of CA IV last summer and fixed
it as described above. But it was pretty hair-raising to see that bent bolt
I was hanging my butt on all that time ;).
Anyway, sorry for the off-topic post.
Daniel Grunloh
>On Sun, 09 Jul 2000 12:06:57 -0800, Ron Webb <rw...@gci.net> wrote:
>It's easy to tell, look at the radial markings on the heads of the
>bolts. six marks means grade 8 and three means grade 5. Standard
>hardware sold in most stores is grade 2, about as soft as a carriage
>bolt.
I believe quite a few UL prop manufactures provide grade 5 or
equivalent bolts in english or metric sizes. AN bolts are
often not used because they provide insufficient thread length
to allow a locking jam nut on the back side of the threaded
Rotax hub.
This method is preferred over safety wiring (by some) because
it allows for easy checking of torque values. Especially
valuable on wood props where the owner/operator is reluctant to
cut those pretty safety wires to check the torque.
--------------
Daniel Grunloh (gru...@uiuc.edu)
http://www.staff.uiuc.edu/~grunloh
Brian Rauchfuss - PCD
>Ron Webb wrote:
>The reason this doesn't exactly subtract from strength in the stressed
>dimension is perhaps a little bit subtle. Consider an axially loaded
>bolt with a preload of 150% of the working load. The working load
>is trying to stretch the bolt. However, the bolt already has strain =
>preload / E. (Where E = Young's modulus.)
>
>The force needed to maintain the preload comes directly from the
>strain ("stretch") in the bolt and is proportional to it.
>
>Now, until the load EXCEEDS the preload, the bolt just isn't going to get
>any longer (no more strain) and so **it doesn't "feel" the load at all**!
>The preload neatly prevents any flexing, so, no work hardening, no fretting,
>no cycling toward any fatique limits, etc, ... THAT'S what the preload is
>for, and why it doesn't subtract from the load-carrying capacity of the bolt.
I guesss this is too subtle for me. The total load on the bolt in the
axial direction is the preload + load. So increasing the preload doesn't
do anything to hide the load.
Brian
Rich Shankland
of AN bolts, so I thought I'd throw in my two cents worth. In four out of
five instances of odd-sized bolt requirements for the Emeraude, I ended up
having to choose Grade 8 or 9 bolts.
The two main wing bolts which attach the spar to the fuselage are 9/16" x
~7" bolts. The four bolts which attach the outer wing panels to the center
section are 1/2" x ~7" bolts (the ~ means I can't remember the exact
length). The six bolts which attach the landing gear to the wing spar are
3/8" x ~8" bolts. The prop bolts are 3/8" x 8" long. None of these are
available on the new or used market in AN grade. I had to use Grade 8 or 9
bolts.
There are 52 bolts which attach the fish plates to the spar at the joints.
(13 top and bottom, each side) These are 5/16" bolts of two different
lengths. As I remember, 5-1/8" long and 5-7/8". Luckily, I found a source
for these on the surplus market as they are no longer available new. If I
had to pay for a specific run of these bolts, each different length would
have cost me over a thousand dollars!
For your information, I located these bolts at Larson Industries. Don Larson
is a friendly fellow who is an honest businessman. His Dad left him a hangar
full of aircraft hardware and Don sells it as a sideline. When it's gone -
it's gone. You may contact him at:
Larson Industries
2758 N. Las Posas Cir.
Camarillo, CA 93012
Ph. (805) 491-2359
fax (805) 491-2559
He has a five page catalog which lists many of the sizes available. When he
runs out of an item, that's it. He doesn't restock. Here's a few examples of
his last listed prices:
Air Frame Bolts
AN 3-5A 35 ea. $2.00
AN 3-12A 10 ea. 1.25
AN 4-5 " 2.00
AN 4-10 " 2.50
AN 4-20 " 2.50
AN 4-40A ea. .75
Elastic and misc. stop nuts
AN 365-1032A 180 ea. $3.00
1-1/4" x 16 Axle nut 2 ea. 5.00
Washers
10-32 alloy washer 360 ea. $4.00
If you compare these prices, I think you will find he undercuts almost
everybody and he's a nice guy to deal with. He made an error on one of my
orders and immediately did everything he could to make it right.
--
Rich Shankland
http://www.harbornet.com/folks/shankland/emeraude
"Bruce Bockius" <elr...@xprt.nospam.net> wrote in message
news:39688213...@xprt.nospam.net...
> My Warp Drive comes with 3/8" bolts and directions to torque them to
> 35-40 ft*lbs. My kit manufacturer says to torque 3/8" AN6 bolts to 160
> in*lbs, which is 13 ft*lbs by my calculations. Are the bolts supplied
> by Warp different than standard AN6 bolts? Why the big difference in
> torques?
>
Bruce Bockius
- the prop bolts were provided by the aircraft kit manufacturer, not
Warp
- they claim to by AN6-34 bolts... A single 'X' on the end, plus the
bold italic 'R' that I believe
designates the manufacturer
- they have what I believe are standard AN castellated nuts on the end
(normal AN thread pitch).
- I see now that Warp recommends torqueing the 1/4" bolts (that ARE
supplied by them) to 110 in*lbs,
which is also way more than the normal torque for AN4.
So it seems that in this application Warp recommends a higher torque than I'm
used to. Like I said these bolts connect the prop extension to the Warp
propeller hub. Now I'm thinking maybe I should torque the AN6 bolts that
connect the other side of the prop extension to the engine redrive to this
same, higher torque - it seems like they are pretty much the same application
to me!
"Juan Jimenez (TeamB)" wrote:
> What kind of nut on the other end?
>
> Bruce Bockius wrote:
> >
Rich Shankland
news:147C08F2B54E6E8F.342E21DC...@lp.airnews.net...
The problem you might run into is for the
> extremely long bolts, as most of the specs I have stop at a grip
> length dash # of 96, which is 6" of grip...
Exactly the problem, Craig. I guess after WWII started, they stopped
manufacturing bolts (and other implements) longer than 6". Fortunately, I
was born in December, 1941 and have no such limitation.
TedInAZ
a hole thru them and bolt them together. You tighten the bolt to obtain
1000 lbs of preload (or squish) pressure between the two bolts. When
unloaded the load will be +1000, 0, -1000, +1000, 0, -1000 at the left
outer, left core, left inner, right outer, right core, and right inner
surfaces of the two pieces of steel. Basically both pieces of steel are
squished together by 1000 lbs.
Now put a 500 pound stretching (axial) load on the two pieces of metal.
The load will now be +1000, -500, -500, +500, +500, -1000. Note that the
load the bolt "sees" is still the 1000 lbs at the outer surfaces of the
steel. The bolt has not stretched for there is still 500 lbs of squish
keeping the pieces together. Even a 1000 lbs (exactly) load will not
separate the pieces.
Now put a 1200 pound axial load on. The loads will be: +1200, -1200, 0,
0, +1200, -1200. The trouble is that after we load the pieces above 1000
lbs there is no "cushion" of squish to draw from. In this case something
(the bolt) is going to have to carry another 200 lbs. Unfortunately,
most materials (including steel) stretch under increased load (and
contract when load is removed). So the bolt will stretch when it must
carry the extra 200 lbs. This is bad because metal does not like to be
continually stretched and contracted (just flex a paper clip a few
times). Remember, before we went above 1000 lbs axial load, the (1000
lbs bolt load - axial load) was absorbed in the squish between the two
plates.
Things get more complicated when the material does not like to be
squished in compression (like wooden props).
Craig C.
>I haven't seen a reference in this discussion pertaining to the availability
>of AN bolts, so I thought I'd throw in my two cents worth. In four out of
>five instances of odd-sized bolt requirements for the Emeraude, I ended up
>having to choose Grade 8 or 9 bolts.
>
If you look at the bolt specs, for a lot of the hard to get stuff,
you can substitute any of the NAS6xxx series bolts that carry
equivalent or better specs.. The 1st x signifies that it is a close
tolerance bolt and what material it is. The next two x's designate the
diameter in sixteenths. The problem you might run into is for the
extremely long bolts, as most of the specs I have stop at a grip
length dash # of 96, which is 6" of grip...
Craig C.
Craig C.
>"Craig C." <valc...@dhc.net> wrote in message
>news:147C08F2B54E6E8F.342E21DC...@lp.airnews.net...
>The problem you might run into is for the
>> extremely long bolts, as most of the specs I have stop at a grip
>> length dash # of 96, which is 6" of grip...
>
>Exactly the problem, Craig. I guess after WWII started, they stopped
>manufacturing bolts (and other implements) longer than 6". Fortunately, I
>was born in December, 1941 and have no such limitation.
>
Hehehe...actually, the only reason my charts stop at -96, is where I
got them from, we never had need for any bolts that were longer than
the -96...and those were extremely rare...In 10 years there, I don't
think that I ever saw an assembly that used anything more than a 4".
Someone does make them, but I don't know who. I do know that at soime
point I will be finding out, as one of my projects requires about 100
bolts that are 6.5"+ in the main spars.
Craig C.