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Replacing odd-ball sized bearings from 1989.

Replacing odd-ball sized bearings from 1989.

(OP)
Dear Gentlemen,
I've been rebuilding the supercharger from 1989 Toyota MR2.  Here in the States, the car is officially an antique.  The supercharger is an OEM factory (Toyota SC12), self contained unit which has a pair of flat roots-type paddles.  I am having trouble finding replacements for the oddly dimensioned front bearings that measure 17mm bore, 45mm outer diameter and 14mm in depth.  It's the 45mm outer that is absolutely impossible to find...  off-the-shelf items tend to be 40mm or 47mm.  If this were a money-no-object project, I could order custom bearings.  Cheaper yet, I could bore the mounts to 47mm but I'm trying to avoid those expenses, if I can.  I was wondering if the problem could be solved by pouring a hard setting compound around smaller 40mm bearings.  Liquid Metal is advertised as being pretty tough.  I was also considering the use of a high-temperature binary plastic called Novolac 555.  Is it likely either of these compounds would adequately hold a 40mm bearing placed inside a 45mm mount?  Does anyone know of a company that stocks odd-ball sized bearings?
Walter Carter, Palm Springs, CA

RE: Replacing odd-ball sized bearings from 1989.

Are there any numbers on the bearing that could be used to identify it?

Failing that, I presume that the shaft needs to be held accurately in alignment in order to maintain the proper clearances between the supercharger rotors and their housing. That ain't gonna happen if you have the shaft loosely in place and pour some sort of liquid crap around it. Plus, if you ever have to change the bearing again ... ! ! !

Choice 1, accurately (!) machine the housing to accept a 47mm OD bearing. Choice 2, machine a sleeve that fits around a 40mm OD bearing which in turn fits into the 45mm hole.

RE: Replacing odd-ball sized bearings from 1989.

I know from personal experience that TRD can be difficult to deal with when it comes to older Toyota performance parts.....However they can and often do have parts such as the bearings you seek in stock.  I certainly would not hurt to check..."Parts is Parts" !

http://www.trdusa.com/

Rod

RE: Replacing odd-ball sized bearings from 1989.

I wonder if it is an imperial size, since one of the inch series has a 44.something mm OD? That would be an odd thing to do, admittedly.

Either way getting the proper spare part is worth it whatever the cost, compared with machining.

The smaller bearing will only have 80% of the load capacity, given the original part has shagged out I am rather averse to replacing it with a weaker part. Might be worth thinking about a needle roller instead.

 

Cheers

Greg Locock

I rarely exceed 1.79 x 10^12 furlongs per fortnight

RE: Replacing odd-ball sized bearings from 1989.

I assume you've measured that it's truly 45mm OD? With 17 x 47 x 14 being such a common bearing size, I just had to ask. Owing to this availability (thus wide choices of other parameters of a replacement bearing), if it were me, I'd try to decide if boring to 47mm would compromise the bearing plate at all. It's only about .080" overbore, so only about .040" material removal.

RE: Replacing odd-ball sized bearings from 1989.

(OP)
I have a hard time believing the outside dimensions on these bearings my damn self.  I have these bearings in my hand and I keep measuring them in disbelief.  The rear set of bearings is even more weird...  they are 46mm O.D!

Regarding the shell idea to get a smaller bearing installed, I wouldn't know where to begin.  I would guess one would want to start with 47mm O.D. aluminum stock or heavy tubing.  For me, that would be like finding the hey stack needle.  And as Mr. PontiacJack pointed out, the smaller bearing would be weaker.  I plan on calling TRDUSA today.  Maybe they have the OEM bearings.

RE: Replacing odd-ball sized bearings from 1989.

TRD is not the manufacturer of the SC12, it is/was manufactured by the Ogura Clutch Company.

I'm about 98% sure it is their "TX12" model, though it may have been updated since 1986 when it was first sold on the MR2: http://www.ogura-clutch.com/products.html?product=105&category=3

Might be worth trying to contact the company for replacements. I haven't yet had an opportunity to dissect the blower on my supercharged MR2 so I'm sorry I can't be more help :)

RE: Replacing odd-ball sized bearings from 1989.

Funny, I've used epoxy based bearing setting technique to effect field repairs on heavy equipment, only to have them last until the other pins and bushings need replacement.  Doing so on a turbo or supercharger would scare the heck out of me.  If a piece ever cracked out in an inconvenient manner (does it ever happen any other way?) and the blower swallowed it, you'll be faced with replacing much more than a bearing.

A sleeve, as a previous poster suggested, barring an original replacement, might be the best way to go.  If you start boring out housings, you've got to watch for oil channels or other features, not to mention weakening it.  A smaller bearing will have less load capacity, true, but may have a higher rpm rating which would equalize the difference.

My 2 cents.  Good luck!

RE: Replacing odd-ball sized bearings from 1989.


Thought from the past---------

7mm OD X 40 mm ID X  width

Heat shrink on available 40 mm X 17 mm bore

 

At 74th year working on IR-One2 - - UHK PhD - - -

RE: Replacing odd-ball sized bearings from 1989.

If you can find a bearing with equivalent
load bearing capacity, machine a sleeve to
to fit the housing. This would be much better
than machining the housing and losing rigidity.
Use Loctite on the sleeve depending on the
housing material.

The more you know, the more you
know you don't know....

RE: Replacing odd-ball sized bearings from 1989.

Look up "tolerance rings" They are a corrugated sheet metal shim for the outside diameter of bearings. They are used in lots of applications where metals are dis-simalar, and have different thermal expansion capacities

http://www.usatolerancerings.com/

Russell Giuliano
 

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