The Murphy Builders Site

Does anyone actually torque warp drive AN6 prop bolts to 35 lb-feet like
Warp Drive specifies?
That is over twice what an AN6 would normally be torqued to and it sure
doesn't feel right to go that high.
This is with hardened washers, fender washers, a UHS fibreglass spinner
backing plate, and a crush plate.
I don't have drive lugs but it is a gear driven prop - not a Lycoming
Ken

From: Ken <klehman@albedo.net>
Reply-To: <rebel-builders@dcsol.com>
To: rebel-builders@dcsol.com
Subject: [rebel-builders] Warp drive prop bolts
Date: Wed, 17 May 2006 22:54:07 -0400

Does anyone actually torque warp drive AN6 prop bolts to 35 lb-feet like
Warp Drive specifies?
That is over twice what an AN6 would normally be torqued to and it sure
doesn't feel right to go that high.
This is with hardened washers, fender washers, a UHS fibreglass spinner
backing plate, and a crush plate.
I don't have drive lugs but it is a gear driven prop - not a Lycoming
Ken





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Hi Ken

Do you mean 35 ?

I thought AN3 nuts needed about 25, and AN4 need about 50, so AN6 would be
higher ?

Nig
745E

Yes Nig but feet not inches. I have two different documents from Warp
Drive specifying 35 lb-ft. (420 in-lb) for 3/8 prop bolts which is over
twice the normal 160 to 190 in-lb for AN6 airframe bolts as noted by Dale.

Steve is correct that 30 lb-ft is not unusual for a 3/8" engine bolt but
engine bolts firm up quickly and don't feel soft and like they are about
to twist off. These prop bolts turn a lot as the torque slowly builds.
At 25 lb-ft they feel like they are stretching -or more likely squeezing
the heck out of that fibreglass spinner back plate. When converting the
engine, I noted that 35 lb- ft on an AN6 bolt with a normal aviation
washer under it, will permanently deform both the washer and a solid
block of 6061 under the washer. Granted the prop hub is almost certainly
a stronger alloy.

I think Drew has the right idea (thanks Drew) and unless I hear
otherwise I think I'll leave them at about 25 lb-ft and check for
fretting/movement on the drive hub when the prop is removed. I haven't
tried it without the fibreglass spinner backplate. The UHS spinner is
popular though and I haven't heard anyone else mention this. I did find
mention on the web of a case of the prop hub being cracked possibly by
overtorquing the bolts. Does anyone happen to know what 3/8 Lycoming
prop bolts are torqued to?

Warp Drive also specs 120 in-lb for the AN4 bolts which clamp the blades
which is also about twice normal but they feel fine to me at 120 in-lb.
Probably because they do not go through the fibreglass spinner backplate.

Ken

N.Smith wrote:

Hi Ken

Do you mean 35 ?

I thought AN3 nuts needed about 25, and AN4 need about 50, so AN6 would be
higher ?

Nig
745E

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popular though and I haven't heard anyone else mention this. I did find
mention on the web of a case of the prop hub being cracked possibly by
overtorquing the bolts. Does anyone happen to know what 3/8 Lycoming
prop bolts are torqued to?

Warp Drive also specs 120 in-lb for the AN4 bolts which clamp the blades
which is also about twice normal but they feel fine to me at 120 in-lb.
Probably because they do not go through the fibreglass spinner backplate.

Ken

N.Smith wrote:

Hi Ken

Do you mean 35 ?

I thought AN3 nuts needed about 25, and AN4 need about 50, so AN6

higher ?

Nig
745E

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Drew

Hi Ken,
Could have been another instance, but I suspected my Warp hub cracked due
to my overtorquing. Mine is small duty stuff though -- a 40hp Rotax 2 stroke
with Warp 66" and aluminum hub. It has 6 center 1/4" bolts and 4 smaller
(8mm) each side and Warp calls out 110-120 in-lbs on the 1/4" in my spec
sheet.
-Ben

Hi Ken,
Could have been another instance, but I suspected my Warp hub cracked due
to my overtorquing. Mine is small duty stuff though -- a 40hp Rotax 2

with Warp 66" and aluminum hub. It has 6 center 1/4" bolts and 4 smaller
(8mm) each side and Warp calls out 110-120 in-lbs on the 1/4" in my spec
sheet.
-Ben

Ken, you may wish to give Darryl at Warp Drive a call. Years ago, when I
first started using the Warp on my Lycoming, I too questioned that high an
over torque setting for the blade clamp bolts and the prop bolts. But

there made it very clear to me that they needed to be at that torque
setting, so that is what I went with. Maybe that is why I never had blade
root collar cracking on mine.

Walter

-----Original Message-----
From: mike.davis@dcsol.com [mailto:mike.davis@dcsol.com] On Behalf Of Ken
Sent: May 19, 2006 7:52 AM
To: rebel-builders@dcsol.com
Subject: Re: [rebel-builders] Warp drive prop bolts

Thanks Ben
The cracked hub I was referring to was on someone's web site that I
looked at a few days ago but they didn't give much detail other than
that Warp replaced it even though they admitted it may have been
overtorqued. I'm getting some interesting offlist info as well. Some
folks have seen fretting on the prop hub on the Lycomings and the six
cyinder 0-300 unless they use the Warp Drive 35 ft-lb. torque on those
3/8 bolts. I haven't found any issues about bolts failing or bolt
problems with the UHS spinner backplate but there apparently have been
some problems with bolts punching through certified composite backplates
when large fender washers were not used. Looks like I'm being overly
cautious but I tend to be overly curious as well ;)
Ken

bransom@dcsol.com wrote:

Hi Ken,
Could have been another instance, but I suspected my Warp hub cracked due
to my overtorquing. Mine is small duty stuff though -- a 40hp Rotax 2

stroke

with Warp 66" and aluminum hub. It has 6 center 1/4" bolts and 4 smaller
(8mm) each side and Warp calls out 110-120 in-lbs on the 1/4" in my spec
sheet.
-Ben

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I use 19 to 22 ft-lbs on all 3/8 prop bolts..Sensenich/McCauley or Warp.
Just recheck them a few days later Ken...but I've never had one loosen
because of the UHS fiberglass bulkhead.

Wayne