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View Full Version : Really need advice on bushing retention problems



stanger53
06-12-2015, 07:15 AM
I often rebuild old Eaton passenger car power steering pumps like came on early 1960s Fords and such. It is a solid compact design, with the main housings split vertically, and a steel input shaft running on a pair of bushings.

A common problem is the front bushing wears oblong in the direction of constant belt pull, and the shaft moves around enough that the front seal will leak. The bushings were never sold separately (only came with new replacement housings - no longer available), so I have been attempting to replace the bushings, but with poor luck so far.

The original bushing was a Clevite piece -- steel backed with an overlay on the inside that had a copper color to it. The shaft is .749" diameter and the bushing is basically made for a .750" diameter shaft and is .750" in length. There is no groove cut into the interior surface of the bushing. Due to normal clearances, there is some pressurized lubricant flow (Ford Type F fluid) around the bushing and shaft and a return hole for the fluid to return to the pump.

I tried using an Oilite bushing of the same basic dimensions, but the bushing was not as nearly a tight fit in the housing bore, so it would quickly stick to the shaft, spin put of the bore, and move forward and push the seal lip out. I tried cleaning the Oilite bushing as best possible and using a bearing locker chemical to help hold it in place, but I suppose the oil in the bearing material prevented the locker from working and I had the same problem.

I then found another bushing made of solid 932 alloy/SAE660 bearing bronze to try. It has no oil, a finely grooved outer surface for locker retention, and press fitted into the housing requiring at least as much pressure as the original bushings. In fact, the bushings interior diameter shrunk down during installation and I have to burnish the bushing bore to get the shaft to go through it. I do not have specs on the clearances of the shaft/bushing setup, but fit it so that the shaft has the same side-to-side play (when dry) as it would in a still-acceptable old bushing.

The housings are doweled to go together, so they fit the same on assembly every time, and upon assembly, the shaft will turn easily and smoothly with the new front bushing installed as it would in old original bushings. When dry, you can noticably move the shaft side-to-side in the bushing and feel the clearance, though it is not excessive enough to hear the parts "click" against each other.

However, I still have a problem keeping the bushing retained in the bore. Shortly after start up, the shaft seems to seize up on the bushing enough to break it loose from the bore, causing the bushing to wander and put pressure on the internal rotor which ofter causes metal shavings and failure. The tight fit and use of green or red bearing chemical locker does not seem to last past startup. The bushing sticks to the input shaft, but does not "weld" to the shaft, and can easily be twisted off and the shaft and bushing are not galled.

I do not understand why this tightly fitted bushing, of bearing bronze material, even when applied cleanly with an additional chemical locker, will almost instantly stick to the input shaft, even though it is not a tight clearanced setup. Is the bushing not getting enough lubrication and need a groove inside it to increase lubricant flow?

Any thought or suggestions on how to get a bushing to fit and stay in the housing? Any idea why the setup seems tight in the right spots, loose in the right spots, but fails to hold properly, sometimes within the first five minutes of fire-up?

gvasale
06-12-2015, 07:58 AM
Depending on how thick/thin the wall of the bushing is, what are the chances of pinning them in place? WRT to your parts seizing, how about a small groove done with a Dremel tool inside the bushing? It would need to break the end where the lube has access to the bushing.

wierdscience
06-12-2015, 10:37 AM
The problem you are having is with expansion of the bronze which has nowhere to go outward since it's constrained by the housing causing it to shrink the bore.That IMO is why the shaft turns free by hand,but sticks and spins the bushing after running.
The original Clevite bearing was a steel backing with only .015-.020" layer of porous Bronze/Tin overlay applied to it,less Bronze,less expansion.

I think you have two options,#1 find a replacement for the original bearings,is there a Clevite number on them?Have you tried tracking them down using that number if so?Maybe look at wrist pin bushings for a suitable replacement.

#2 ream some clearance in the 932 bearings,shooting from the hip I would suggest .0008-.001" >installed< clearance would be the minimum.

firbikrhd1
06-12-2015, 10:50 AM
While reading your post a thought occurred to me; could you use a caged needle roller bearing in place of the bushing? If the shaft is hard where it runs on the bushing it might be a solution. A caged bearing may have less friction than a bushing so it wouldn't have th tendency to try to spin in the housing, plus the pressed in portion is steel.
I'm just shooting from the hip here and trying to help with a solution and there may be a hundred reason why this solution won't work.

stanger53
06-12-2015, 11:35 AM
The problem you are having is with expansion of the bronze which has nowhere to go outward since it's constrained by the housing causing it to shrink the bore.That IMO is why the shaft turns free by hand,but sticks and spins the bushing after running.
The original Clevite bearing was a steel backing with only .015-.020" layer of porous Bronze/Tin overlay applied to it,less Bronze,less expansion.

I think you have two options,#1 find a replacement for the original bearings,is there a Clevite number on them?Have you tried tracking them down using that number if so?Maybe look at wrist pin bushings for a suitable replacement.

#2 ream some clearance in the 932 bearings,shooting from the hip I would suggest .0008-.001" >installed< clearance would be the minimum.

I was never able to find a replacement Clevite bushing -- was never able to determine if they were ever available separately at all. Clevite doesn't seem to do a lot of small bushing like this anymore.

I don't know what the exact clearance is between the bushing and shaft. When cold and dry, the shaft will move side-to-side noticabley and you can feel the gap when it does. It isn't loose like a broom handle in a garbage can, but I would think that this would indicate more than .001" alone.

Maybe the clearance needs to be looser to allow for the clearance shrinkage when the pump is operating. I am not aware if solid bronze bushings expanded that much. The bushing itself is only about 1/16" thick.

stanger53
06-12-2015, 11:38 AM
While reading your post a thought occurred to me; could you use a caged needle roller bearing in place of the bushing? If the shaft is hard where it runs on the bushing it might be a solution. A caged bearing may have less friction than a bushing so it wouldn't have th tendency to try to spin in the housing, plus the pressed in portion is steel.
I'm just shooting from the hip here and trying to help with a solution and there may be a hundred reason why this solution won't work.

Since the bushing is only about 1/16" thickness, the only way a needle bearing would work would require align-honing the bore of the housing larger to accomodate the bearing. I am not capable of this. I am also not sure that the shaft material is designed and hardened to operate on a needle bearing since that is not its original application.

Blackfoot
06-12-2015, 12:40 PM
Is there any possibility that the shaft is bent. I think any (no matter how slight) misalignment of the shaft will make holding a press fit bushing difficult or impossible. How was the original bushing held in place? If there was no shoulder on the bushing or snap ring or something in the hole to keep the bushing from pushing through, then something is going on that is not natural for that pump. I have not done the math, but with only .062" wall thickness, it would take quite a bit of oil pressure against it to push it out. Is this a vane, piston, gear, or what type pump is it?

dfw5914
06-12-2015, 03:06 PM
McMaster sells a steel backed bronze bearing:
http://www.mcmaster.com/#standard-sleeve-bearings/=xlf2dg

stanger53
06-12-2015, 03:57 PM
Is there any possibility that the shaft is bent. I think any (no matter how slight) misalignment of the shaft will make holding a press fit bushing difficult or impossible. How was the original bushing held in place? If there was no shoulder on the bushing or snap ring or something in the hole to keep the bushing from pushing through, then something is going on that is not natural for that pump. I have not done the math, but with only .062" wall thickness, it would take quite a bit of oil pressure against it to push it out. Is this a vane, piston, gear, or what type pump is it?

It is not the shaft. I have had this happen with four separate pumps now, each with its own shaft and housings.

The only thing keeping the original bushing in place is a press fit. I don't think that oil pressure is pushing the bushing out. I think the bushing is trying to seize up on the shaft -- despite clearance and oil all around it -- and then it tends to walk up and down the shaft either pushing forward on the front seal or rearward against the rotor.

The pump is a "roller" style pump which is a six-armed rotor with hollow rollers loose in between the arms.

tc429
06-12-2015, 07:19 PM
how thick is the housing from bushing od to housing od? you might have room to put a split thread in there- drilling parallel to shaft at bushing/housing contact point, and put a small spring pin or even a 4-40 setscrew in... it wont spin, but will be a bear to remove next time. the old dodge 'taperlok' quick disconnect hubs use something kinda like this(but thread clearance on one half), I always hated them as they often wont come apart... Ive seen the split threads used on a lot of older equipment, it works, but think it might be a last resort type of thing...

for initial break-in, consider adding some special lube: www.lowerfriction.com sells tungsten disulfide lube, way slicker than moly, and the film thickness is so insanely small, you wont need enough to cause contamination worries... Ive been mixing the powder with grease, using as 'neverseize', amazingly slick stuff...I have also been mixing about a teaspoon with a quart of way lube, putting in our refitted machines- slides are often initially draggy, tried some of this additive, dropped servo current from 80% to 15% in a few minutes of running, and it stayed there... My buddy Glen likes to set gibs a little tight on turcite as it tends to lap in a bit in the first day or two of operation, but last time I still saw high servo load after letting it run overnight on way lube, tried some of this crap- it really works.
I wouldnt recommend using it on a engine as rings need 'abrasion' to initially seat rings, but wouldnt be afraid to add a little after the first few miles. on something like a bushing, I would think it should do fine...
Alternately, maybe just chuck up the shaft in a drill and 'run it in' for a little bit before assembling the rest of the pump?

boslab
06-12-2015, 07:36 PM
Cut a few small grooves in the bore, like circlip size, a few shallow on the bush od, stick it in with retaining stuff like loctite bearing fit, that worked for me on a roots blower unit
Mark

RussZHC
06-12-2015, 08:59 PM
Grasping here...any chance what is supposed to be round is not?

Spent some time looking at this online and man, not much info and most of the rebuild kits are just seals, the only bit that seemed directly related was advice that if the fit is too sloppy to find a replacement housing complete that is a better fit...of course the complete opposite is also out there, rebuilds in the hundreds and hundreds of dollars.

Really tiny pin on the line between bushing and housing to keep it from spinning? Or as Mark and others have said, some sort of mechanical means as opposed to bonding...it really sounds like you are doing everything one can...

Rich Carlstedt
06-12-2015, 10:10 PM
You pose an interesting problem , but more information is needed.
You say :
" Due to normal clearances, there is some pressurized lubricant flow (Ford Type F fluid) around the bushing and shaft and a return hole for the fluid to return to the pump."
What do you mean when you say around the bushing?
Is the flow or pressure on the OD of the insert ?
Where is the return hole ?
Observation:
Brass or bronze expands 50 % more than steel or cast iron
I assume the body is cast iron or steel ?
The factory using a steel backed insert has little concern for thermodynamic expansion issues.
By using a brass/bronze bushing, you do !
Brass/Bronze bushings are sized by the fit ! If the OD of the bushing is +.005 larger than the bearing bore size, it will shrink .005 when pressed in. That's why the ID of the bushings are oversize, so you can control this without reaming or honing the bore after installation.

Please understand that a Brass/Bronze bearing has "TWO" low coefficient of friction (COF) surfaces, the ID and the OD, so both must be controlled.
The factory installed inserts had a low COF on the bore and high on the OD

You can determine if the bronze is causing a problem quite easily by making a few bushings out of cast iron.
The bushing will not seize on the shaft and should run fine, just will not last as long as a tin/copper compound coating found on the original inserts
Rich

CalM
06-12-2015, 10:21 PM
Try an automotive automatic transmission supply. There is just about every size plan bearing used in slush boxes.

I've got quite a selection left over from a recent GM 4L30e rebuild. I bet you can find a replacement for the original.

Barring that, a little more clearance, and pin the things!

oldtiffie
06-12-2015, 10:30 PM
Why not "hard chrome" the shaft and grind or turn it to size if/as required?

https://www.google.com.au/?gws_rd=ssl#q=hard+chrome+usa

https://www.google.com.au/search?q=hard+chrome+usa&biw=1536&bih=710&tbm=isch&tbo=u&source=univ&sa=X&ved=0CDsQsARqFQoTCIHiq-bPi8YCFc0RvAodNroAOw

stanger53
06-12-2015, 10:52 PM
You pose an interesting problem , but more information is needed.
You say :
" Due to normal clearances, there is some pressurized lubricant flow (Ford Type F fluid) around the bushing and shaft and a return hole for the fluid to return to the pump."
What do you mean when you say around the bushing?
Is the flow or pressure on the OD of the insert ?
Where is the return hole ?
Observation:
Brass or bronze expands 50 % more than steel or cast iron
I assume the body is cast iron or steel ?
The factory using a steel backed insert has little concern for thermodynamic expansion issues.
By using a brass/bronze bushing, you do !
Brass/Bronze bushings are sized by the fit ! If the OD of the bushing is +.005 larger than the bearing bore size, it will shrink .005 when pressed in. That's why the ID of the bushings are oversize, so you can control this without reaming or honing the bore after installation.

Please understand that a Brass/Bronze bearing has "TWO" low coefficient of friction (COF) surfaces, the ID and the OD, so both must be controlled.
The factory installed inserts had a low COF on the bore and high on the OD

You can determine if the bronze is causing a problem quite easily by making a few bushings out of cast iron.
The bushing will not seize on the shaft and should run fine, just will not last as long as a tin/copper compound coating found on the original inserts
Rich

The front and rear bushings are right alongside the impeller inside, so that area is pressurized and there is always some fluid escaping past the rotor and the housing and making it to the bushings. The fluid runs between the shaft and the bushing. Each bushing has a hole on the other end for the fluid to vent back into the pump, thus promoting flow and preventing excessive fluid pressure against the back side of the seal.

The housing of the pump is cast iron. From what I have been reading on solid bronze bushings, they do contract inside with the press fit, and they also expand more with heat, and therefore require more clearance than a steel-backed bushing.

The bushing has a bit of "tooth" on its OD -- a fine grooving like the grooves on an old LP record (if you know what that is). The ID of the housing bore is about the same. I would think this is sufficient to give the chemical locker the area and roughness to firmly hold the bushing in place, but not always it seems.

I would think the press fit along should retain the bushing in the bore, and the locker is just insurance. I think my main problem is that the clearance I am trying for seems fine when the pump is cold, but is too tight when it gets hot and the bushing expands and shrinks inside. I think I need to size the clearance looser and it might be wise to cut a shallow lubrication groove in the ID of the bushing to promote lube flow. I understand the principle of pinning the bushing to keep it from rotating, but I feel that is last-chance remedy needed because something else isn't done properly.

Oh, and thanks to everyone on the comments and suggestions. They have all been inciteful and helpful.

stanger53
06-12-2015, 10:55 PM
Why not "hard chrome" the shaft and grind or turn it to size if/as required?

https://www.google.com.au/?gws_rd=ssl#q=hard+chrome+usa

https://www.google.com.au/search?q=hard+chrome+usa&biw=1536&bih=710&tbm=isch&tbo=u&source=univ&sa=X&ved=0CDsQsARqFQoTCIHiq-bPi8YCFc0RvAodNroAOw

The problem on these pumps is not that the clearance is loose overall, but that the bushing becomes egg-shaped after many years of running with constant belt-pull in one direction. When the shaft can move considerably father in one direction then at 90-degrees to it, then the shaft pulls away from the seal and causes a leak. The idea to replace the bushing is to restore the shaft to a bearing surface that is round and has the correct clearance its full diameter.

Forestgnome
06-13-2015, 10:51 AM
If the bushing was "sticking" to the shaft it would show signs of galling. Have you tried researching who originally manufactured the pump? I found parts for my hydraulic pump that way. The pump was in an International loader, but I found the pump was manufactured by Cessna.

Willy
06-13-2015, 12:31 PM
I believe the OP stated that this was an Eaton pump. I've rebuilt a number of these pumps but that was many years ago when the rebuild kits did include bushings. I see that this pump is still available new but it has now been changed over to bearings rather than bushings. This pump was and still is used in other applications as well, I've seen them used on tractors for example. Converting it to bearings would be the way to go but as you already mentioned you do not have the equipment or capability to do this conversion. For about $140 for a new pump this is always the last option, but at least that option is there.
As a rule a part like a bearing or bushing usually has more than one application, so like CalM and Forestgnome mentioned, I too would try a well stocked automatic rebuild shop or a hydraulic rebuild shop as a source for that elusive bushing.

Pinning the bushing to the bore is also an option but the fact that you are experiencing a seizure between the shaft and the bushing at this point suggests that clearances are too tight and or the bushing is being distorted when pressing it into the housing.
I had a quick look on Ebay and was quite shocked to see these old pumps going for upwards of $400 for a good old original!! The car resto crowd must still have some serious coin to spend.:)

garyhlucas
06-13-2015, 08:11 PM
After reading this thread and seeing that the bushing is very thin wall I think another force is at work here. We just brought in a mixer and when we took it apart the bearings are still good but the outer races have about 0.060" clearance in the aluminum housing! The bearings had been walking around in the aluminum housing roll forming it it to a larger size, kind of like burnishing a bore.

I believe what happens here is that the shaft actually presses the bushing hard against the housing and the bushing 'walks' around the bore it is installed in. Slowly but surely it roll forms the bushing until it is thinner and a loose fit. The steel backed bearing can handle the load while the oilite or bronze cannot. That walking action is kind of like a harmonic gear reducer with an enormous reduction ratio, so a very high force can be generated which shears any adhesive you might use. So what you need is a bushing material that is just a little softer than the steel of the shaft so they don't gall.

boslab
06-13-2015, 08:29 PM
That makes sense, sounds as if it's going to be either a bearing transplant or white metal cast in situ and bored.
Mark

mike4
06-13-2015, 08:42 PM
I have had some luck with Chinese manufactured steel backed bushings , I have an old pump that is used to transfer used engine oil from the catch tray to storage tank , it was something that i picked up at a site a few years ago , manufacturer unknown but it had a similar problem .

I was looking online for some other parts and came across a supplier , emailed them with the details and they sent four as a sample , I have since purchased many others to replace bushes which are not able to be sourced from the local suppliers.

Yes I know that many here will get on their high horse about buying from Chinese sources , however when the OEM decides to curtail parts due to whatever reason , I am quite happy to find a supplier who can get what I want , and when these are compared to the originals they are exact in measurement and material to the no longer made OEM stuff.

I see no reason to junk a machine on principles alone.

Michael

sarge41
06-13-2015, 08:58 PM
Just wondering, are the bronze bushings impervious to things like thread locker and other types of cements such as epoxies ?

sarge

Doozer
06-13-2015, 11:25 PM
There is a company that makes sintered iron bushings. I forget the name.
Also CyberBond is a retaining compound (Loctite type) that works well in the
presence of oil. Yes I have tested it, it sticks like glue even under oil.
Loctite type products will wick into sintered bearings, not solid ones.

-Doozer

firbikrhd1
06-13-2015, 11:30 PM
So what you need is a bushing material that is just a little softer than the steel of the shaft so they don't gall.

Just a thought, how about a cast iron bushing?

stanger53
06-14-2015, 12:58 AM
There is a similarly sized bronze bushing available in a harder, tougher grade of bronze that is made for strength. If the problem is the bushing being "pressed" thinner, then that bushing may work better., but since the material in the bearing I am using is the most common bearing bronze alloy, I think the bushing is up to the load.

I'm thinking that the bushing need to be installed with more clearance than usual. I have read many places that an all bronze bushing needs more clearance because the heat will make it close up tighter on the shaft, and I think this is what is happening.

In all cases, the bushing started to seize on the shaft and break loose from the housing after only a few hours time. The last incident, which I have here right now, probably did so in the first 30 minutes. When I installed everything, the shaft had the same amount of side clearance as a good used bushing would have, but I think the all-bronze bushing needs more to allow for the loss of clearance that comes with use and heat.

Never has the bushing completely froze on the shaft. They broke loose from the housing, and were stuck to the shaft, but you could easily grab the bushing and twist it off the shaft by hand. The steel shaft showed a bit of galling, but I think that was from metal debris from the parts movement in the pump and not from the bushing welding up.

I think I need to make sure the bushing (after installation) is perfectly round and smooth inside, and allow an extra thousandth or two of clearance to allow for the tightening down. I have a brand new OEM 1960s era pump that I can tear down and check the factory clearances from. I will do this and figure out what to add to the clearance to allow for expansion.

I am just surprised and concerned because it failed so quickly before any real hydraulic load was put on it. I thought it had sufficient clearance and the locker would be extra insurance.

1-800miner
06-14-2015, 01:35 AM
Maybe lap the bushing after it is installed?

Willy
06-14-2015, 01:42 AM
I think I need to make sure the bushing (after installation) is perfectly round and smooth inside, and allow an extra thousandth or two of clearance to allow for the tightening down. I have a brand new OEM 1960s era pump that I can tear down and check the factory clearances from. I will do this and figure out what to add to the clearance to allow for expansion.



I think you are on the right track. Round and smooth is good, straight as well is also key.
It's been a long time since I've been into those pumps but I remember reaming the bushings after install. I do quite a bit of older HD engine work and just about any bronze bushing in this and other work that I run into entails the use of a reamer to ensure proper finished size. Adding a little extra clearance can only help at this point.

RichR
06-14-2015, 10:38 AM
Maybe you could duplicate the original bushing. Turn a piece of steel to 0.875" and bore it to 0.770". Put a bronze plug in with some retaining
compound and let it set up. Bore out to 0.750" and then part it off.