[TowerTalk] Thrust bearing Help
K8RI on Tower talk
k8ri-tower at charter.net
Wed Nov 30 17:45:45 EST 2005
>I have a Glen Martin TB-25 Thrust Bearing
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> I am having trouble BACKING OUT the set screws that lock the Mast in
> place
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> This TB-25 is made of Die cast Aluminum.
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> I have used WD-40 and several other sprays.
As with most penetratiing oils, WD-40 may take a day or two to penetrate.
I noted one other reply on WD-40 being a water displacment oil. Virtually
all hydrocarbon oils displace water, but that is not how they break stuck
bolts, and *pistons* free.
I'd give the WD-40 a number of applications and let it set for a day or two.
There are other penetrating oils available such as PB blaster and "Mouse
Milk" (yes that is for real) and every one seems to have their favorite.
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> I just can't break loose the bolts. I just don't want to break the bolts
> or
> the top housing of the TB-25.
>
There is probably some corosion in there between the aluminum casting and
steel bolts. If repeated applications of penetrating oil do not work over
several days (This problem requires patience) you can try alternating
applications of heat to the casting around the bolt, applications of
penetrating oil (careful of fire) and actually heating the bolt. Remember
the Aluminum has a far greater coefficent of expansion than steel. Also try
working the pressure applied by the wrench to the bolt "back-and-forth" just
a little.
Another approach is an impact wrench set to very low power
Another, moving more toward last resorts is to tap the bolt head with a
hammer in a direction that would drive it straight in. When I say "tap",
I'm guessing these are probably either 5/16" or 3/8" common steel rather
than a grade 5 or 8 so they are already on the soft side. Based on that a
"tap" is definately not a round house swing using a 5# Engineer's Hammer.
<:-)) OTOH you can hit them fairly hard depending on the hardness of the
bolt, the size of the bolt and the hardness of the mast inside the thrust
bearing.
>
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> Any ideas on what to spray on the bolts that will help break them loose
As I said earlier, this is a problem that normally takes patience. Although
the process can be hurried with heat and impact, the hurrying often causes
more problems than it solves.
As an example, we used to take small engines that had seized. You couldn't
turn the crank with a pipe wrench, but take the head off, spray with WD-40,
let set over night and you could turn the crank by hand the next day.
Roger Halstead (K8RI and ARRL 40 year Life Member)
N833R - World's oldest Debonair CD-2
www.rogerhalstead.com
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> 73 de wb5aaa
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> later,
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> Jim Barron
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>
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