How resistant is the thrust bearing to damage?
01-07-2011, 10:58 AM
#21
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-Jordan- Posted on Jan 7 2011, 06:06 PM
No it is not.
The thrust bearing is not like a crank journal.
Crank journals form an oil wedge like this:
Thrust bearings in the F20/22 (probably all engines) are half moon shape (180º) bearing shells that can not create a wedge that thick & strong.
The thrust bearing surface is devided in 3 sections by 2 grooves where oil is forced between the bearing and the crank.
At every groove is an oil film break.
Also, and not like in the crank journal drawing, there is no oil "stored" in the thrust bearing at rest.
It needs fresh oil to form an oil film, it has no oil at the ready at a cold start like crank journals.
The question is: how fast does it build-up a strong enough oil film to support any load, how many revs does it take?
Kinda clear is: when you start the engine with the clutch in, there is a load on the thrust from the 1st revolution of the crank.
Concider the fact that it only takes a couple hundred lbs to release the clutch pedal and the thrust is made from material and lubricated in the same way as the main and rod bearings.
The thrust bearing is not like a crank journal.
Crank journals form an oil wedge like this:
Thrust bearings in the F20/22 (probably all engines) are half moon shape (180º) bearing shells that can not create a wedge that thick & strong.
The thrust bearing surface is devided in 3 sections by 2 grooves where oil is forced between the bearing and the crank.
At every groove is an oil film break.
Also, and not like in the crank journal drawing, there is no oil "stored" in the thrust bearing at rest.
It needs fresh oil to form an oil film, it has no oil at the ready at a cold start like crank journals.
The question is: how fast does it build-up a strong enough oil film to support any load, how many revs does it take?
Kinda clear is: when you start the engine with the clutch in, there is a load on the thrust from the 1st revolution of the crank.
01-07-2011, 11:34 AM
#22
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Originally Posted by crank,Jan 7 2011, 11:53 AM
the starter spins the tranny now along with the engine...although i too believe NO load on the thrust bearings is better during a cold start. I would rather replace a starter the thrust bearings
01-07-2011, 12:49 PM
#23
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Originally Posted by SpitfireS,Jan 7 2011, 11:58 AM
-Jordan- Posted on Jan 7 2011, 06:06 PM
No it is not.
The thrust bearing is not like a crank journal.
Crank journals form an oil wedge like this:
Thrust bearings in the F20/22 (probably all engines) are half moon shape (180º) bearing shells that can not create a wedge that thick & strong.
The thrust bearing surface is devided in 3 sections by 2 grooves where oil is forced between the bearing and the crank.
At every groove is an oil film break.
Also, and not like in the crank journal drawing, there is no oil "stored" in the thrust bearing at rest.
It needs fresh oil to form an oil film, it has no oil at the ready at a cold start like crank journals.
The question is: how fast does it build-up a strong enough oil film to support any load, how many revs does it take?
Kinda clear is: when you start the engine with the clutch in, there is a load on the thrust from the 1st revolution of the crank.
No it is not.
The thrust bearing is not like a crank journal.
Crank journals form an oil wedge like this:
Thrust bearings in the F20/22 (probably all engines) are half moon shape (180º) bearing shells that can not create a wedge that thick & strong.
The thrust bearing surface is devided in 3 sections by 2 grooves where oil is forced between the bearing and the crank.
At every groove is an oil film break.
Also, and not like in the crank journal drawing, there is no oil "stored" in the thrust bearing at rest.
It needs fresh oil to form an oil film, it has no oil at the ready at a cold start like crank journals.
The question is: how fast does it build-up a strong enough oil film to support any load, how many revs does it take?
Kinda clear is: when you start the engine with the clutch in, there is a load on the thrust from the 1st revolution of the crank.
01-07-2011, 03:00 PM
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gernby Posted on Jan 7 2011, 09:34 PM
Input shaft and 1st, 2nd and reverse gear set.
Set = 2.
And roller bearing drag in 3rd to 6th gears on the input shaft and 2 main bearings.
With cold & thick oil it can be more that just a couple of % I guess.
-Jordan- Posted on Jan 7 2011, 10:49 PM
You mean: they get oil?
Yeah.. that's pretty fundamental
Its not even oil directly from an oil supply, its second hand oil from a crank journal.
At a cold start they are running dry.
By default.
Just as dry as piston rings and cams.
Only for a short time (agree) but its a different thing in crank journals as they have some oil "in" them.
No.
Closed journal bearings are not the same as thrust washers.
3 strikes = you're out.
Actually.. strike 4 would be the clearance.
Crank journals have between 0.017-0.041mm of play.
Axial crank play is between 0.10-0.35mm.
Not exactly the same fundametal principle.. is it?
The starter would only have to spin the input shaft of the transmission
Set = 2.
And roller bearing drag in 3rd to 6th gears on the input shaft and 2 main bearings.
With cold & thick oil it can be more that just a couple of % I guess.
-Jordan- Posted on Jan 7 2011, 10:49 PM
the fundamental method of lubrication is the same
Yeah.. that's pretty fundamental
Its not even oil directly from an oil supply, its second hand oil from a crank journal.
Unless the thrust bearings are running dry
By default.
Just as dry as piston rings and cams.
Only for a short time (agree) but its a different thing in crank journals as they have some oil "in" them.
the same type of bearing as the mains/rods.
Closed journal bearings are not the same as thrust washers.
3 strikes = you're out.
Actually.. strike 4 would be the clearance.
Crank journals have between 0.017-0.041mm of play.
Axial crank play is between 0.10-0.35mm.
Not exactly the same fundametal principle.. is it?
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