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Afterfxllc(at)aol.com
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 Posted: Fri Apr 29, 2011 4:44 am Post subject: What a joke |
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This is the most Mickey Mouse SB and fix I think I have ever seen.
Instead of replacing the bolt and nut with one of the proper size and length they (Jabiru) just add an ARP nut that is too long and that's their fix.
I am in the process of installing the New water cooled heads on a 3300 that fixes the non existent re occurring over heating problems they (Jabiru) claims don't exist. But the funny thing is Rotec has sold over 100 sets of them. I will post pics as we progress on the install.
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Thruster87
Joined: 16 Apr 2008
Posts: 193
Location: Australia
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| Posted: Sun May 01, 2011 9:20 pm Post subject: Re: What a joke |
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A local flight training center that has been using Jabiru aircraft for the past 12yrs, swears by the new nut modification,they found that the new nuts can be torqued more easily [the small nuts feel like they are going to strip the threads during torquing] and since doing the SD have NOT had any more issues.Also they have a wobble bar [10"] which they ground to move about 10 deg and they ground the socket walls so it would fit in.This way NO need to remove any bits from the engine.The jury is still out on the need to use loctite,as without it it would make it a lot easier to re-torque the nuts/studs. Cheers
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Afterfxllc(at)aol.com
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| Posted: Mon May 02, 2011 11:26 am Post subject: What a joke |
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I know for a fact the ARP nut is far better and stronger than the old nut but having said that they should have also had the bolt of the proper length replace the old one.
It seems to me they are trying to fix a stripping nut problem with a stronger nut when in fact they have a non stretching bolt problem they aren't addressing and as you know when you strengthen one part something else is more prone to fail. Seems like the heat is causing the case to expand and the bolts aren't of the stretch type so the nuts strip as a result. Re torquing is simply masking an underlying problem.
Same as the heads.
Jeff [quote][b]
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mhubel
Joined: 05 Sep 2009
Posts: 141
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| Posted: Tue May 03, 2011 5:03 am Post subject: What a joke |
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Is it being suggested that the loctite is not really required? It
appears that the original nuts were locking and the replacements are
not. Still we use other bolts in critical places which have no locking
method like head bolts. I find the idea of using Loctite questionable as
I believe it can increase the risk of improper torque applied and if one
has to remove it, Loctite claims the temperature to weaken it is 250C,
To get anything that hot, parts are much hotter. One would think the
bolt strength would be compromised by over heating. According to SAE
J429 heat treated bolts should not be subject to temperatures over 260C.
I think this means that if a nut ever has to be removed the bolt (and
cylinder?) has to be removed.
On 05/02/2011 1:20 AM, Thruster87 wrote:
| Quote: |
A local flight training center that has been using Jabiru aircraft for the past 12yrs, swears by the new nut modification,they found that the new nuts can be torqued more easily [the small nuts feel like they are going to strip the threads during torquing] and since doing the SD have NOT had any more issues.Also they have a wobble bar [10"] which they ground to move about 10 deg and they ground the socket walls so it would fit in.This way NO need to remove any bits from the engine.The jury is still out on the need to use loctite,as without it it would make it a lot easier to re-torque the nuts/studs. Cheers
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=338613#338613
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--
Mark Hubelbank
NorthEast Monitoring
2 Clock Tower Place
Suite 555
Maynard, MA, 01754 - USA
mhubel(at)nemon.com
978-443-3955
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_________________
Mark Hubelbank
N708HU
CH601XL
Jabiru 3300
Rotec TBI 40-3 carb
Sensenich ground adj prop.
240 hr TAF
Pictures at photo.hubbles.com |
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psm(at)att.net
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| Posted: Tue May 03, 2011 5:24 am Post subject: What a joke |
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Hi Mark,
I don't know why I am getting into this conversation, but I guess my
experience making knives comes into play here.
When heat treating steel, the temperature is raised to a desired
temperature to reduce brittleness. For tool steels this is usually done
to at least 900 or 1000 degrees F. I'm not sure exactly what
temperature aircraft bolts are heated to, but I'm quite sure it is well
above 250 C. So long as the temperature is kept below the heat treating
(tempering) temperature I don't think the characteristics of the steel
will be impacted.
I also wonder what role LocTite or other friction devices might play
here. The large diameter nuts in question should be torqued to a very
high and consistent level. I would hope this would keep them from
coming loose under expected conditions of vibration and temperature.
Lastly, I wonder why amateur builders think they know more about how to
keep an engine running properly than the designers of that engine.
Paul
XL Jab 3300 soon to enter flight test.
On 5/3/2011 5:57 AM, Mark Hubelbank wrote:
| Quote: |
Is it being suggested that the loctite is not really required? It
appears that the original nuts were locking and the replacements are
not. Still we use other bolts in critical places which have no locking
method like head bolts. I find the idea of using Loctite questionable
as I believe it can increase the risk of improper torque applied and
if one has to remove it, Loctite claims the temperature to weaken it
is 250C, To get anything that hot, parts are much hotter. One would
think the bolt strength would be compromised by over heating.
According to SAE J429 heat treated bolts should not be subject to
temperatures over 260C. I think this means that if a nut ever has to
be removed the bolt (and cylinder?) has to be removed.
On 05/02/2011 1:20 AM, Thruster87 wrote:
>
> "Thruster87"<alania(at)optusnet.com.au>
>
> A local flight training center that has been using Jabiru aircraft
> for the past 12yrs, swears by the new nut modification,they found
> that the new nuts can be torqued more easily [the small nuts feel
> like they are going to strip the threads during torquing] and since
> doing the SD have NOT had any more issues.Also they have a wobble bar
> [10"] which they ground to move about 10 deg and they ground the
> socket walls so it would fit in.This way NO need to remove any bits
> from the engine.The jury is still out on the need to use loctite,as
> without it it would make it a lot easier to re-torque the nuts/studs.
> Cheers
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=338613#338613
>
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Afterfxllc(at)aol.com
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| Posted: Tue May 03, 2011 10:45 am Post subject: What a joke |
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Well Paul
If you read 4130 it has standards that I and everyone else needs to follow. I have shown this fix to a few A&P's that have said they would NOT sign off if this was on an engine this way. Jabairu has a history of an engine that overheats and distorts cylinders and this is just another example of piss poor engineering.
Ask yourself if you would see this on a lycoming or Continental and the answer is no and the reason is because they have to build them to standards where others use experimental as a way to get away with anything.
Jeff
| Quote: | Lastly, I wonder why amateur builders think they know more about how to
keep an engine running properly than the designers of that engine.
|
[quote][b]
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