99Mystique ATX
Hard-core CEG'er
There is not enough room to run a wider bearing (or bearings) on the jackshaft without modifying several things...
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Vortech build
- Thread starter Beans
- Start date
oh well, thanks for clearing that up. ...G.
Selecting a bearing for this application is tricky, you have to balance carrying the shaft load (easier with larger bearings) against keeping the bearing's internal components foot-per-minute (FPM) speeds below self-destruction, and for a given RPM, FPM goes up as bearing diameter increases. It's a double-edged sword: You want large bearings to carry the load, but large bearings have higher FPM and therefore lower RPM limits. Toss in another variable like dealing with the environment (unsealed, sealed, shielded, etc), and it only gets tougher to find the right bearing.
I would suspect that for most of us, our engines spend 90% of their running life between idle and 4,000 RPM, so even with the jack shaft at 2X crank, these bearings are comfortably running in their safe zone most of the time, but the low percent romps to 6,500 RPM crank is where the damage occurs.
The folks at Vortech are pretty smart, and have been dealing with high speed bearings for many years, so I suspect they made an engineering compromise.
I haven't seen the shaft bearing housing, but it may be in a "clean" enough area to use a shielded bearing.
I would suspect that for most of us, our engines spend 90% of their running life between idle and 4,000 RPM, so even with the jack shaft at 2X crank, these bearings are comfortably running in their safe zone most of the time, but the low percent romps to 6,500 RPM crank is where the damage occurs.
The folks at Vortech are pretty smart, and have been dealing with high speed bearings for many years, so I suspect they made an engineering compromise.
I haven't seen the shaft bearing housing, but it may be in a "clean" enough area to use a shielded bearing.
i was surprised to read in those data sheets that the jackshaft bearings are actually low grade general purpose.
In one description, it said they are automotive wheel bearings.
How many people change their wheel bearings every 30k miles ? Something is obviously wrong. I'm guessng your car tires don't whizz round at 14K.
What you said about the rating of larger bearings is true of the double race bearings too. I thought that maybe the premature failiure of the bearing was due to axial forces, not the destruction of the bearing seal. This might have explained to an extent, the spline failiures. Whatever, seems Vortech thought the problems insurmountable and so they stopped making ticking time bombs :laugh: .
Hopefully now some more light has been thrown onto this issue, finding a better bearing is a step closer ... G.
svtfixer
Veteran CEG'er
i figure there may be a unit of the same dimensions just with the new technology. but youre saying that to handle the rpms its going to be a different dimension? wider?
Beans
Addicted CEG'er
considering the shielded and the rubber sealed bearings are exactly the same, one is rated 14k the other 9k... it occured to me that it wasn't just the rubber seal failiure that could be killing the bearings.
When i looked into axial bearings like the ones on the impeller output shaft, i found they come in two flavors, single and twin row . The twin row run cooler and have lower friction and were worth looking into, since the shaft runs above a header. They are 18 - 21mm wide depending which ones you use ... hence why i asked if they were even possible as candidates.
There are single row axial bearings that are 15mm wide iirc, ... i may try those if the shielded fail like the rubber sealed do .....G.
sorry beans, didn't intend to crowd out the thread.
svtfixer
Veteran CEG'er
at least its relevant. i have my jackshaft out. what info were you looking for on it?
if you can fit an 18 or 21mm wide bearing. The stock bearing is 15mm.
It's already been said that it would require machining of the shaft and other parts too.
It will probably be easiest for everyone if a suitable single row axial bearing could be found.
I'm going to test out the stock shielded type.
It will be much easier to find a properly speed rated shielded bearing than a rubber sealed, so hopefully my new bearings will not suffer with dirt ingress... paving the way for an axial bearing of the same type ...G.
99Mystique ATX
Hard-core CEG'er
Ok so I got to thinking about this a bit more and I think there may be a better solution. Based on what I've seen, the inside bearing (s/c side) is usually in the worst condition. That's the side that was shot on my unit and had a bit more play/wear in the bearing on Beans's unit. Given the design of the unit this makes sense so I think if you really wanted to prolong the life of the jackshaft bearings you'd want to look at running a different inner bearing. My suspicion is that the RPM isn't the main issue that it is more the combination of RPM and load. Bearing life is essentially a function of rotating speed, load and lubrication. Increase speed or load and you'll decrease bearing life.
If you turned the shaft down (section separating the outer and inner bearings) so you could run a wider bearing on the inside I think you might be able to fit a wider bearing in there. However, I'd make sure the jackshaft went to a very good machinist who knew exactly what you wanted done. It wouldn't take much and you'd be out of a jackshaft and stuck with an expensive paperweight.
If you turned the shaft down (section separating the outer and inner bearings) so you could run a wider bearing on the inside I think you might be able to fit a wider bearing in there. However, I'd make sure the jackshaft went to a very good machinist who knew exactly what you wanted done. It wouldn't take much and you'd be out of a jackshaft and stuck with an expensive paperweight.
do you think being in the center of the shaft where there is most flex, may be a contributing factor ? Maybe a bracket could be made to brace the center.
ideally wider bearings would be best, if it was just 3mm to be taken off the shaft.
One question pops up..... if you machine your shaft, do you think you can still retro fit the stock 15mm wide bearings ?
BTW; how did beans' jackshaft look for runout ? ...G.
svtfixer
Veteran CEG'er
These Things aren't cheap let alone available to play around w.
Do all these bearings take the same type of oiling? And is that really enough for the speed? I would think the age of the oil and the cleanliness of it have a lot to do w longevity .
don't Paxton's use something like trans fluid?
It's a fairly small line as is, does that change w different units or is that siZe line fairly standard?
Do all these bearings take the same type of oiling? And is that really enough for the speed? I would think the age of the oil and the cleanliness of it have a lot to do w longevity .
don't Paxton's use something like trans fluid?
It's a fairly small line as is, does that change w different units or is that siZe line fairly standard?
99Mystique ATX
Hard-core CEG'er
Would it help? Sure, but it wouldn't be worth nearly the time, cost and effort to do it. I understand trying to improve the design but there comes a point where it's just not worth it. If you need a car you can reliably drive a 25k+ per year throwing a Vortech on it isn't the way to go. It's great for a toy or something you can work on but IMO that's about it.
Like I said before, if you really want to modify it I'd run at 6205DU on the pulley side and then machine the shaft and then possibly run a wider bearing on the s/c side. I'd have to run some calculations to see what makes sense but that could work.
If you machined the shaft and wanted to go back the easiest way would be to design a press-fit sleeve to make up the difference in what you removed. So, yes it could be done.
I don't know yet, J/S is still at the machinist's.
i only asked because when you look at failed bearings, you can sometimes tell what has caused the failiure. Since you have the experience, i thought you might have some insight to how they failed. I haven't seen one of those failed bearings up close.
As for making a supporting bracket, something that i will keep in mind, in case a good oportunity arises to do it. You know; those days when you want to do something to your car and you can't decide what ..... and in frustration you end up buying some needless shiny crap :laugh:.
yeah i see, but the wider bearings are axial (you know with thrust written on the side), so you need to run them in pairs, don't you ? .... G.
edit; sorry i don't mean to keep coming back at you. I just thought you were the person to ask since you had actually repaired them.
That's why i ask a lot of questions before ripping into anything. ... G.
Beans
Addicted CEG'er
Again. 30k is unreasonable maintenance on a car that didn't come with forced induction from the factory? Don't think so.
If something fit direct, it would be worth a upgrade. Too much work otherwise. Seems like that doesn't exist, therefore beating a dead horse!!!!!!!!
If something fit direct, it would be worth a upgrade. Too much work otherwise. Seems like that doesn't exist, therefore beating a dead horse!!!!!!!!
Yeah, i understand all this talk of bearings can seem boring, i should of started another thread instead of hi-jacking yours ... sorry mate ....G.
Beans
Addicted CEG'er
Vortech build
I dont mind at all, it's a good place for the discussion.
I think you guys are being over zealous with the idea.
I dont mind at all, it's a good place for the discussion.
I think you guys are being over zealous with the idea.
svtfixer
Veteran CEG'er
us few crazies gotta stick together.
we love problem solving, sorry... but god made us that way ...G.