Solid Pinion Spacers...
Registered User
Joined: Jul 2000
Posts: 520
From: MD
Heh… I think I finally found what I was looking for in some ford documentation…
As per ford, the crush sleeve is there for 2 reasons:
- keep the inner bearing race of the front pinion bearing from spinning on the pinion shaft, wearing a grove in it. If the preload is to work right you can not have a press fit on both sides, and without an inner race press fit it will tend to spin on its own.
- Keep the bearings square during assembly to assure that they seat in the races correctly so as not to mess up the bearings or loose preload later on.
Nothing about holding the nut on…
I feel better now.
As per ford, the crush sleeve is there for 2 reasons:
- keep the inner bearing race of the front pinion bearing from spinning on the pinion shaft, wearing a grove in it. If the preload is to work right you can not have a press fit on both sides, and without an inner race press fit it will tend to spin on its own.
- Keep the bearings square during assembly to assure that they seat in the races correctly so as not to mess up the bearings or loose preload later on.
Nothing about holding the nut on…
I feel better now.
West South Central Moderator / Special Guest
Joined: Dec 1998
Posts: 1,650
From: Coppell, TX USA
mark,
it will however help keep the pinion nut on, because it allows more torque to be applied to the nut. Pinion nuts don't back off a lot, but it does happen. many people don't run crush sleeves/solid spacers at all.. and have found that w/o tacking the nut it backs off.
yes, in theory it prevents the bearings inner race from spinning on the shaftl, but due to the preload on the bearings in the first place(totally created by the nut), I doubt this is an issue.
*shrug*
it will however help keep the pinion nut on, because it allows more torque to be applied to the nut. Pinion nuts don't back off a lot, but it does happen. many people don't run crush sleeves/solid spacers at all.. and have found that w/o tacking the nut it backs off.
yes, in theory it prevents the bearings inner race from spinning on the shaftl, but due to the preload on the bearings in the first place(totally created by the nut), I doubt this is an issue.
*shrug*
Registered User
Joined: Dec 1998
Posts: 209
The crush sleeve provides bearing preload that is independant of how much torque is applide to the pinion nut. The nut is torqued down to over 100lb-ft, in order to bottom out the yoke onto the pinion.
As the sleeve is compressed, it first goes through an elastic range, where it acts as a spring. As it is compressed further, it passes the steels yied point and permanantly deforms. If you then loostened the pinion nut, the crush sleeve would go back through the elastic region before it loses preload, (called hysteresis). So, even after it is deformed, it is still preloading the bearings.
The crush sleeve sets preload, and prevents over-preloading. Plus, it maintains preload as the bearings wear, and also during differential expansion/contraction duer to temperature extremes.
The crush sleeve acts as a spring with a very high spring constant.
The preload can be set using solid spacers and shims, however this is very time consuming, is dependant on the installer, and doesn't compensate for part tolerances (flatness, parallelism) wear, or temperature effects.
FYI, I've spent the last 10 years designing preloaded bearing sets for DC spindle motors, there are many ways to acheive preload (crush sleeves, springs, dead weight)
As the sleeve is compressed, it first goes through an elastic range, where it acts as a spring. As it is compressed further, it passes the steels yied point and permanantly deforms. If you then loostened the pinion nut, the crush sleeve would go back through the elastic region before it loses preload, (called hysteresis). So, even after it is deformed, it is still preloading the bearings.
The crush sleeve sets preload, and prevents over-preloading. Plus, it maintains preload as the bearings wear, and also during differential expansion/contraction duer to temperature extremes.
The crush sleeve acts as a spring with a very high spring constant.
The preload can be set using solid spacers and shims, however this is very time consuming, is dependant on the installer, and doesn't compensate for part tolerances (flatness, parallelism) wear, or temperature effects.
FYI, I've spent the last 10 years designing preloaded bearing sets for DC spindle motors, there are many ways to acheive preload (crush sleeves, springs, dead weight)
Registered User
Joined: Feb 2000
Posts: 35
From: Chickasha, OK
PGR,
You state:
"If you then loostened the pinion nut, the crush sleeve would go back through the elastic region before it loses preload, (called hysteresis). So, even after it is deformed, it is still preloading the bearings."
If that's the case, then answer me one simple question. Why, if I take the nut off the pinion, can I then remove the front bearing (after the seal if removed). I haven't removed the crush sleeve, and it is still in its original position, but the front bearing will come off. If the crush sleeve preloads the bearings, they should remain loaded until the crush sleeve is removed, but they don't. You must distinguish the difference between BEARING loading and CRUSH SLEEVE loading. They are not the same.
The crush sleeve goes between the front and rear bearings. It is actually trying to PUSH the bearings OUT of the cups (away from one another). It does NOT load the bearings into the cups. That is what the nut does.
If you still doubt this, try a little experiment. Put a rearend together without the crush sleeve. Tighten the nut to 100 ft-lbs. After you do, you will not be able to rotate the pinion. Why??? Because the nut is OVERLOADING the bearings. In this condition the bearings will ultimately fail. The crush sleeve provides resistance against the nut while tightening. This allows you to torque the nut to 100 ft-lbs and still rotate the pinion.
As I said before, the front spindle is EXACTLY the same. Tighten the nut, and the resistance to turning the wheel becomes more (ie the preload is higher). A front spindle doesn't have a crush sleeve, or a solid spacer, yet bearing preload is acheived. How is this possible with what you are saying? It is possible because the NUT provides the bearing preload. When the nut is locked down with a cotter pin, it cannot back off, and with minimal bearing wear, preload is maintained.
Let me define PRELOAD. It is the load that keeps the bearings pushed into the cups. Without this load, the bearings would be loose in the cups and wear would cause failure. It is just enough to cause rolling resistance, but not enough to accelerate wear. If you can picture a pinion with the bearings and cups, it would be impossible for the crush sleeve to force the bearings into the cups, as it is located BETWEEN the bearings.
Another suggestion. Tighten a pinion nut with a new crush sleeve. As the crush sleeve begins to crush, there is a HUGE resistance on turning the nut (probably over 75 ft-lbs). But, even though the crush sleeve is crushing, the pinion will still move in and out. Why???? Because the nut has not forced the bearings into the cups, ie there is no preload.
I don't know the oreintation of the cups and bearings on a DC spindle motor, but I do know how a rearend works. I have built many of them, and because the mouth of the cups are facing AWAY from each other, and the crush sleeve is located BETWEEN the cups, it does NOT provide preload. Bearing preload can be acheived WITHOUT the crush sleeve.
Shane
You state:
"If you then loostened the pinion nut, the crush sleeve would go back through the elastic region before it loses preload, (called hysteresis). So, even after it is deformed, it is still preloading the bearings."
If that's the case, then answer me one simple question. Why, if I take the nut off the pinion, can I then remove the front bearing (after the seal if removed). I haven't removed the crush sleeve, and it is still in its original position, but the front bearing will come off. If the crush sleeve preloads the bearings, they should remain loaded until the crush sleeve is removed, but they don't. You must distinguish the difference between BEARING loading and CRUSH SLEEVE loading. They are not the same.
The crush sleeve goes between the front and rear bearings. It is actually trying to PUSH the bearings OUT of the cups (away from one another). It does NOT load the bearings into the cups. That is what the nut does.
If you still doubt this, try a little experiment. Put a rearend together without the crush sleeve. Tighten the nut to 100 ft-lbs. After you do, you will not be able to rotate the pinion. Why??? Because the nut is OVERLOADING the bearings. In this condition the bearings will ultimately fail. The crush sleeve provides resistance against the nut while tightening. This allows you to torque the nut to 100 ft-lbs and still rotate the pinion.
As I said before, the front spindle is EXACTLY the same. Tighten the nut, and the resistance to turning the wheel becomes more (ie the preload is higher). A front spindle doesn't have a crush sleeve, or a solid spacer, yet bearing preload is acheived. How is this possible with what you are saying? It is possible because the NUT provides the bearing preload. When the nut is locked down with a cotter pin, it cannot back off, and with minimal bearing wear, preload is maintained.
Let me define PRELOAD. It is the load that keeps the bearings pushed into the cups. Without this load, the bearings would be loose in the cups and wear would cause failure. It is just enough to cause rolling resistance, but not enough to accelerate wear. If you can picture a pinion with the bearings and cups, it would be impossible for the crush sleeve to force the bearings into the cups, as it is located BETWEEN the bearings.
Another suggestion. Tighten a pinion nut with a new crush sleeve. As the crush sleeve begins to crush, there is a HUGE resistance on turning the nut (probably over 75 ft-lbs). But, even though the crush sleeve is crushing, the pinion will still move in and out. Why???? Because the nut has not forced the bearings into the cups, ie there is no preload.
I don't know the oreintation of the cups and bearings on a DC spindle motor, but I do know how a rearend works. I have built many of them, and because the mouth of the cups are facing AWAY from each other, and the crush sleeve is located BETWEEN the cups, it does NOT provide preload. Bearing preload can be acheived WITHOUT the crush sleeve.
Shane
Registered User
Joined: Dec 1998
Posts: 209
I guess my last post was way unclear. The crush sleeve preloads the front inner bearing race against the pinion yoke. It does not preload the bearing set, that is accomplished by the pinion nut torque.
The crush sleeve will keep the front inner race from spinning on the pinion shaft, and increase the friction required to back off the pinion nut.
In order for a crush sleeve to preload the bearing set, it would need to be in forward of the front innner race, or be a larger diameter and be between the outer races, assuming they are a slip fit (which they aren't!)
The crush sleeve will keep the front inner race from spinning on the pinion shaft, and increase the friction required to back off the pinion nut.
In order for a crush sleeve to preload the bearing set, it would need to be in forward of the front innner race, or be a larger diameter and be between the outer races, assuming they are a slip fit (which they aren't!)
Thread Starter
Registered User
Joined: Jun 2001
Posts: 822
From: Lawrence, KS, USA
Originally posted by PGR
The preload can be set using solid spacers and shims, however this is very time consuming, is dependant on the installer, and doesn't compensate for part tolerances (flatness, parallelism) wear, or temperature effects.
The preload can be set using solid spacers and shims, however this is very time consuming, is dependant on the installer, and doesn't compensate for part tolerances (flatness, parallelism) wear, or temperature effects.
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