Alternator casing spun bearing repair

[Webley91]

Looking into it further, I have found a site that lists a bore dimension for "mounting roller bearings" as 36.89 to 36.98mm. "For torque transfer" is given as 36.67 to 36.75mm.

That is over 1mm larger than given by the other source. I had assumed that these rings were made to standard sizes?

The second site also says they can compensate for misalignment. Does that mean that, depending on the amount of wear, they could be used without needing to bore out the housing?

 

[Peter from Holland]

The bore still needs to be straight IMHO

Peter

 

[Webley91]

Thanks for the reply.

My plan was to mount a piece of scrap steel bar in the lathe chuck. I would then turn a boss to fit the bore in the outer side of the casing. I would tap this boss with a thread such as M10 x 1.5

I would have to remove the oil seal from the casing in order to fit a bolt and washer to hold it onto the boss.

I could then machine the bore to suit the tolerance ring.

If the wear in the rear bearing is not too bad, I may not even need to remove it from the shaft. The outer race is slightly pitted but not badly scored. It did not make any noticeable sound before the alternator failed.

 

[dana gear]

I have a failed alternator from a Mitsubishi 2.5l Diesel engine. It is believed that the internal electronic regulator has failed, which can easily be and cheaply replcaced.

On disassembling the alternator, I found that the rear bearing had spun in the aluminium casing. The bearing is the type with a groove in the outer race to hold a spring clip. I am unsure of the correct term for this type of bearing (see link below). The spring clip was found to be broken into two pieces when disassembled. This had presumably allowed it to spin in the bore.

I have considered boring out the bearing housing and fitting a steel sleeve. This would not be necessary if a bearing with a suitably oversized outer race could be found.

From what I have read, these bearings are not interference fitted to allow for expansion due to heat. Is this correct? If so, whay clearance would the bore need to be machined to?

There is also a groove in the bore in line with the position of the spring clip. Was this groove machined by design or worn into the bore by the loose bearing?

Link to the image of the specific bearing:
https://www.shop.bendiks.pl/eng_pl_140432-NS-Bearing-36739_1.jpg

Thanks for any information.

Our Caterpillar fork lifts are built by Mitsubishi and badged Caterpillar, we purchase replacement alternators from Wilson a supplier to O -Reilly's auto parts about 70 bucks. you may want to see what they have.

 

[dian]

Looks like you could get a thin plate made to fit the slot diameter and cut it in half then put it on and press it off. Ie using the slot as the point of contact.
I have not got my head around how it fits together as it looks arse about in the picture...sure the fan would be on the outside, but the seal position looks wrong in regard to the spine.
It appears you don't have much meat to play with in regard to sleeving the bore so will be out of luck.
I would put new bearings in it and loctite the loose bearing in place...if it heats up the alloy housing should expand faster than the shaft.
As long as the bearing is not too loose in the bore...if its really loose you may be out of luck also.
those small bearings sure spin at a hight rpm if you do pulley ratio calcs and refer it to the engine rpm.

"I would put new bearings in it and loctite the loose bearing in place...if it heats up the alloy housing should expand faster than the shaft."

thats what i was thinking. expansion of shaft and housing should roughly cancel out. the same for a spindle with aluminum housing.

and if you use permatex, it would matter even less.

 

[john.k]

What makes them expensive is the exhauster(vacccum pump),splined extension of the armature......A commmon fail is the spline disappears,and a whole new alt is needed.......Any plain alternator is cheap ..........If you want expensive ,then try the 400amp oil cooled alternators from busses and coaches ......no change from $10,000..some are more costly even ....all the power is needed to drive a multitude of small blowers to circulate air in the coach.

 

[Webley91]

To revisit this thread, I sourced the bearing and oil seals* from a local alternator repair shop.

They had a look at it a few months back and said that the rear housing was worn out so they would be unable to repair it. They do not have the capability to machine the housing, but said they would be willing supply the parts and could test it once reassembled.

They are apparently able to also source the tolerance ring but don't have it in stock at their shop. They will hopefully get back to me with a price next week. Their supplier's catalogue also lists thicker walled solid repair rings which can be interference fitted in place. The closest suitable size in the catalogue is 35 x 38 x 10mm.

I have measured the worn bore and it is oval shaped towards one side. The gap appaered to be too much to use loctite or similar.

*As for the oil seals, they come in a pack of two. Apparently some Japanese alternators with vacuum pumps use two matching oil seals placed into the same bore. I have never yet seen this configuration used on anything I have personally worked on. Looking into the seal from the outer side it looks like a twin-lip design. I did not realise there were two separate seals.

Our Caterpillar fork lifts are built by Mitsubishi and badged Caterpillar, we purchase replacement alternators from Wilson a supplier to O -Reilly's auto parts about 70 bucks. you may want to see what they have.

I am in the UK. I couldn't locate any UK based companies who could supply a reconditioned original unit.

I did manage to find a new replacement from an unknown brand which it currently fitted to the vehicle.

There were a few places that quoted significantly more than the cost of the new replacement unit to rebuild the old one. This was also before I was aware of the spun bearing.

 

[john.k]

A lot of auto parts repairers are significantly more costly that a new part......and thats before the "we struck a problem" spiel ,that costs an extra $100 over the quote...If you are to run an auto shop ,you must perfect the "we struck a problem I've never seen before" with a straight face ...and demand an extra hundred just like it happened every day!...........The psychoanalyst would equate this action with an unfulfilled childhood desire to rip off customers and lie like a politician.

 

[BT Fabrication]

Thanks for the replies. I have attached photos showing the bearing and housing. This alternator has a vacuum pump mounted to the rear which is driven by the splined shaft.

As far as I know, this alternator was made by Hitachi.

I did think of using the rear casing from another alternator. They were used with many variations of the same engine in a range of vehicles. Apparently these bearings commonly spin and wear the bores, so another unit would likely have the same problem.

These engines are also not often found in UK junkyards. This engine is now over 30 years old. It is rare to see anything made before 2000 in a junkyard here. These used engines are also commonly exported as complete units when the vehicles are scrapped.

I believe the front bearing is locked in place. I have not disassembled the front end as the front bearing still turns smoothly.

A replacement regulator can be easily bought for around the equivalent of $20 USD. I thought it would be worth repairing as a spare unit as the windings are undamaged. I originally hade a quote of over 200 UK Pounds to have it rebuilt, but this was before I had disassembled it and found the spun bearing.

The vehicle currently has an unbranded new replacement alternator fitted, which was half the cost of a rebuild. While it is working now, I am sure it will not last as long as the original.

What would be the best way of removing the bearing from the shaft without damaging the pressed steel cup underneath?

View attachment 296775

View attachment 296776

any way you do it will screw the seal up, seals and bearings are like lego bricks, just need a bearing supplier or hydraulic supply to fix it and find the ID OD and thickness. its all universal fit.