[TowerTalk] Thrust Bearing expansion, a little warning

[Hans Hammarquist]

 Yes, the expansion for most resins is far larger than for most metals. The warning is that you usually place the resin inside a metal housing of some sort (as you don't want to rely on the tensile strength of the resin, only compression). The result is that, when you heat the assembly, the hole diameter will shrink because the resin will expand more that the surrounding metal housing. 

This is more of academic interest as the elasticity of the resin will allow the shaft to rotate even if you have a tight fit.

Hans - N2JFS 

 

 

-----Original Message-----
From: jimlux <jimlux at earthlink.net>
To: Thomas Noel <tnoel at mac.com>; charlie <charlie at thegallos.com>
Cc: Gene Smar <ersmar at verizon.net>; towertalk <towertalk at contesting.com>
Sent: Fri, Dec 9, 2016 10:06 pm
Subject: Re: [TowerTalk] Which Thrust Bearing to Use

On 12/9/16 6:45 PM, Thomas Noel wrote:
> Absolutely. The circumferential expansion far exceeds the tiny inward
> radial expansion.
>
There's no radial inward expansion at all. everything moves "out"
the outer edge moves out "more" than the inner edge.


> Thomas W Noel
> KF7RSF
>
>> On Dec 9, 2016, at 6:23 PM, charlie at thegallos.com
>> <mailto:charlie at thegallos.com> wrote:
>>
>> <anip>
>>> I don't agree.  If the hole is large enough to just clear at -40C, when
>>> heated the entire mass will increase in volume.  The OD will get larger
>>> and
>>> the hole will get smaller and become tighter against the mast.
>>>
>>>
>>> 73 de
>>> Gene Smar  AD3F
>>>
>>>
>> I guess your science teacher "Back when" didn't do what mine did.  He had
>> a steel ball (on a handle, and a steel ring (ditto).  At room temp, the
>> ball would NOT fit through the ring - maybe 1/32 of interference.  You
>> then took the ring, put it in a bunsen burner, and hot it hot (didn't even
>> need to be red) - the ball fit though perfectly
>>
>> Yep, the way materials expand the hole gets bigger.  We do it in the shop
>> ALL the time, heat a gear etc to make the hole bigger to drop over a shaft
>>
>>
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