Ball Bearings on IM Shaft

[Gizmoman]

Here are a few photos of my IM shaft with two ball bearings installed on the sprocket end instead of the sleeve bearing.
I mentioned doing this a while ago and was poo-pooed for the idea - I simply had to do it then

I added some brass at the bottom of the bore to provide enough meat for the bearing depth (needs more cleaning up).

The shaft was turned to 40mm and I found a 40mm ID seal that fit the cap perfectly.
I also had to take about .030 off the inside face of the cap.

The snap-ring groove is not shown in the drawing.



The fits are "small hammer snug" and the shaft rotates with my little finger. I cross-drilled into the oil port which will cause the oil to flow through the bearings before returning the the block. I removed the seals from the bearings and added a spiral retaining ring to keep the shaft from moving laterally.

It was all very scary but I couldn't be happier with the outcome. I won't tighten the timing belt any more than is needed - I just won't worry about the sleeve bearing anymore or loose oil pressure as it begins to fail.

[8v-of-fury]

Duuuuuuuuude, right on!

Absolutely going in to the FAQ/How-To thread

[wolf_walker]

I don't think there is a thing wrong with it in concept, other than cost.

Only other concern is service life with the relatively filthy oil in a motor,
particulates denting the tiny space between the roller and race and that
dent cracking over time, you'd never hear or notice till it came apart without
regular inspection.  Which is part of why aircraft get that after a certain number
of hours I believe.  The oil gap is much higher in use on a sleeve bearing, such
particulates slide right through.  I'd consider a bypass oil filter after all this work.  

http://www.motortrend.com/features/auto_news/2008/112_0804_2008_sae_show/photo_18.html

Way, way, way back, early 1900's, there were full ball bearing motors built, even up into the 60's
some really high end Indy car stuff was built with them here and there.  And of course motorcycles, then and now.
I'm sure there are other examples.

I'll be interested to hear how it lasts.

We had an interesting go-round with the IMS bearing on the M96 Porsche motors, P did some
stupid things, aftermarket did some stupid things, then someone but some tougher ceramic bearings in and actually
let it get oiled, eventually it occurred to someone that you could ditch
the failure prone roller bearing and put a sleeve bearing in and it was all better. More or less.
It's still a ***ty motor.  Go figure

Neat stuff either way.  

[wolf_walker]

Wait, I do have one more question.

I'm not familiar with the oil routing intimately off hand, but common wisdom has been for
a long time that worn IMS bearings=low idle oil pressure and I've seen basic crude evidence of this myself.

Isn't feeding bearings like that, assuming from the same source as original, going to be a big open spot
and adversely effect oil pressure?  Did you restrict flow in any way?

[Gizmoman]

. . .Did you restrict flow in any way?

The original port is blocked by the tight bearing fit.  If you look closely, you can see a tiny hole cross-drilled into the feed port. I figured that's about the right diameter . Don't recall the exact drill size but it really is quite tiny.
Thanks for the excellent feedback all. I will be adding some additional filtering and cooling as well. Never thought about the particulates in the diesel oil. One of the good things is that I don't think the bearings are loaded heavily if the belt is tensioned properly. The bearings were about ten bucks each http://www.vxb.com/SRCH.html?Store_Code=bearings&Search=6906rs.




8V - thanks for the kudos but I'd wait to see how it lasts before posting - hate to steer someone wrong.

[libbydiesel]

Gizmo, how are you handling the thrust?

[8v-of-fury]

8V - thanks for the kudos but I'd wait to see how it lasts before posting - hate to steer someone wrong.

Can't get feedback and stuff without it being out there. If it fails, all the better to have it documented.

[Gizmoman]

Gizmo, how are you handling the thrust?

I'm letting the two rows of balls handle it. That's why it was nice being able to slip two bearings in the space.
I figure it can't be too much as the stock flange just rode against the inside face of the cap/cover. The cover had a slight polish from the original flange.
I agree there will be some thrust but I doubt it's enough to worry about. Probably highest when the oil is cold and the pump is working it's hardest.
That is unless I'm totally wrong

[Blocksmith]

Don't get me wrong--I love over-engineered solutions to a problem, and this coming from a family that is staring down the barrel at 3 out of 4 kids being engineers when it's all said and done. But the practical side of me just can't silence the little voice saying 'get a timing belt tension measurement tool and be done with the whole problem'. Only about $70 on ebay (with only 30 seconds of searching), and it will save one from destroying one's IP main bearings as well. Dunno, just kinda seems to me like one would be ahead in the overall scheme of things to invest in the necessary tooling to properly service these motors per VW spec, and have done with it...

HAVING SAID THAT, I most certainly tip my hat to you--going where no man has gone before, as it were, and I am quite curious as to how this solution to a common problem plays out in the long term (speaking as one needing to replace a set of totally destroyed IM bearings in an ongoing motor rebuild). Keep us posted--despite what I may have insinuated, I am rooting for you and your ambitious solution!

[Toby]

The question that I have is: What makes you think the block isn't cracked where you brazed it? Clearly you did not preheat anything, because the paint and grease aren't burned off. Cast iron does not take well to localized heating to those temps.

[Gizmoman]

Agreed Blocksmith. It's a long story but in the original block, the IM shaft bearing was probably still within the Bentley spec - it simply needed a re-bore and new "standard" rods. That speaks to how a properly tensioned timing belt makes for
little wear on the original bearing. The used block I purchased, I purchased because the bores still had the original hone marks (also came with the proper rods) and the bearing was totally shot. Which led (If I recall) to a jumped/broken belt and trashed head.
BTW, I tension the belt with the twist method and it has worked so far.

What I did may have been totally unnecessary but it's done and as well as I had hoped. I have been designing/building machines all my working life and removing weaknesses is just part of the process. Hopefully, I won't regret this odd-ball stunt.

The question that I have is: What makes you think the block isn't cracked where you brazed it? Clearly you did not preheat anything, because the paint and grease aren't burned off. Cast iron does not take well to localized heating to those temps.

As for cracks in the casting, your'e correct - pre-heating a larger area may have been better but where do you stop? There is huge a chance the larger heat zone may relieve stresses elsewhere and change all sorts of things. It was a gamble and it was quite nerve racking for sure but I had to make the call. Besides, I've successfully brazed more cast iron than most. Insinuating that I didn't know what I was doing based on a photo is silly. There are no cracks.

The comments are appreciated - all of them. And as I've said many times, without this forum, I'd have never attempted this build at all.

[R.O.R-2.0]

omg... i think i just.. well, yea..

this is the coolest thing ive ever seen!!

sir, that is some brilliant construction work..

(this would be a good one to post on the 16v forum on Whortex as well, being that 16v engines eat IM shaft bearings WITHOUT over tensioning the belt)

[Gizmoman]

Thanks a bunch R.O.R.
If I were to do it again, I would not go as deep into the block, and go deeper in the cap which still has quite a bit of meat. Having to add brass had my b-hole seriously puckered.