 How do bearings work?, Aluminum case expansion |
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| worn |
 May 24 2013, 08:35 PM
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Winner of the Utah Twisted Joint Award  Group: Members Posts: 3,602 Joined: 3-June 11 From: Madison, WI and North Bend WA Member No.: 13,152 Region Association: Upper MidWest 
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Calling the experts and anyone else. The case with the holes is aluminum. The crank, cam and lifters are steelish. As the case heats up the holes expand at twice the rate of the steel parts within. So how are for example main bearing clearances maintained as I open the throttle on the ribbon of highway that lies ahead. Shouldn't oughta work. Are they extra tight to start out with? (IMG:style_emoticons/default/unsure.gif)
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| Jeff Hail |
May 24 2013, 09:23 PM
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Senior Member Group: Members Posts: 1,141 Joined: 3-May 07 From: LA/ CA Member No.: 7,712 |
QUOTE(worn @ May 24 2013, 07:35 PM)  Calling the experts and anyone else. The case with the holes is aluminum. The crank, cam and lifters are steelish. As the case heats up the holes expand at twice the rate of the steel parts within. So how are for example main bearing clearances maintained as I open the throttle on the ribbon of highway that lies ahead. Shouldn't oughta work. Are they extra tight to start out with? (IMG:style_emoticons/default/unsure.gif) The secrets in the film. It's all about the film. |
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| McMark |
May 24 2013, 09:27 PM
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#3
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914 Freak! Group: Retired Admin Posts: 20,180 Joined: 13-March 03 From: Grand Rapids, MI Member No.: 419 Region Association: None |
Doesn't it expand in all directions...
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| stugray |
May 24 2013, 10:06 PM
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#4
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Advanced Member Group: Members Posts: 3,825 Joined: 17-September 09 From: Longmont, CO Member No.: 10,819 Region Association: None |
QUOTE Doesn't it expand in all directions... A cylinder will increase in diameter as it heats. So a hole down the middle of a cylinder (a pipe) will increase in inside diameter as it heats. So I dont know why it works either. Stu |
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| VaccaRabite |
May 25 2013, 06:03 AM
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#5
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En Garde! Group: Admin Posts: 13,878 Joined: 15-December 03 From: Dallastown, PA Member No.: 1,435 Region Association: MidAtlantic Region
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1) tolerance is designed so that the clearance is acceptable at cold and hot to have oil pressure in the proper range. You can be out of spec but have good cold oil pressure that falls on its face when the engine is hot.
2) expansion at the center is relatively small. Expansion is not linear. 3) the engine heats up from the heads in, not the crank out. And the center of the engine will be roughly oil temp instead of the outside of the engine which will be roughly head temp. Less expansion at 200 then at 390. Zach |
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| Mark Henry |
May 25 2013, 06:15 AM
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#6
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that's what I do! Group: Members Posts: 20,065 Joined: 27-December 02 From: Port Hope, Ontario Member No.: 26 Region Association: Canada |
QUOTE(Vacca Rabite @ May 25 2013, 08:03 AM) 1) tolerance is designed so that the clearance is acceptable at cold and hot to have oil pressure in the proper range. You can be out of spec but have good cold oil pressure that falls on its face when the engine is hot. 2) expansion at the center is relatively small. Expansion is not linear. 3) the engine heats up from the heads in, not the crank out. And the center of the engine will be roughly oil temp instead of the outside of the engine which will be roughly head temp. Less expansion at 200 then at 390. Zach QUOTE(Jeff Hail @ May 24 2013, 11:23 PM) The secrets in the film. It's all about the film. (IMG:style_emoticons/default/agree.gif) |
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| worn |
May 25 2013, 09:08 AM
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#7
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Winner of the Utah Twisted Joint Award Group: Members Posts: 3,602 Joined: 3-June 11 From: Madison, WI and North Bend WA Member No.: 13,152 Region Association: Upper MidWest
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QUOTE(Mark Henry @ May 25 2013, 04:15 AM) QUOTE(Vacca Rabite @ May 25 2013, 08:03 AM) 1) tolerance is designed so that the clearance is acceptable at cold and hot to have oil pressure in the proper range. You can be out of spec but have good cold oil pressure that falls on its face when the engine is hot. 2) expansion at the center is relatively small. Expansion is not linear. 3) the engine heats up from the heads in, not the crank out. And the center of the engine will be roughly oil temp instead of the outside of the engine which will be roughly head temp. Less expansion at 200 then at 390. Zach QUOTE(Jeff Hail @ May 24 2013, 11:23 PM) The secrets in the film. It's all about the film. (IMG:style_emoticons/default/agree.gif) I know all about the film. What I am wondering about is the fact that the case is going to grow considerably from cold start to operating temp. The bearing supports will open up as circles to be several thousands larger. And the steel expands as well, but only half as much. How do you make an aluminum motor not too tight at cold and still ok at full hot? That is not a question about the film just my curiosity a professional habit for me. Not meant to solve a problem. Thanks |
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| Mark Henry |
May 25 2013, 09:35 AM
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#8
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that's what I do! Group: Members Posts: 20,065 Joined: 27-December 02 From: Port Hope, Ontario Member No.: 26 Region Association: Canada |
I'm getting that all the time when I post as well, doesn't seem to load, then you press "add reply" again and it double posts.
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| worn |
May 26 2013, 09:19 AM
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#9
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Winner of the Utah Twisted Joint Award Group: Members Posts: 3,602 Joined: 3-June 11 From: Madison, WI and North Bend WA Member No.: 13,152 Region Association: Upper MidWest
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QUOTE(Mark Henry @ May 25 2013, 07:35 AM) I'm getting that all the time when I post as well, doesn't seem to load, then you press "add reply" again and it double posts. Well thanks for fixing that. Back to topic I find that gm has filed patents addressing this with main bearings. They found that a very high beryllium aluminum alloy would produce an expansion coefficient like steel. Proposed it for bearing caps. As to the film, how thick is it by the time the warm up is complete? |
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