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VW MKIII-A3/B4 TDIs This is a discussion about MKIII-A3/MkIII Jetta/Golf (<99.5) and B4 Passats (96,97) TDI's. Non TDI related postings will be moved or removed.

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Old April 6th, 2016, 11:10   #46
thechoochlyman
 
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I took some more detailed measurements of the roller assembly and added an assembly drawing. You can see the large version Here. Please excuse the mixture of English/Metric dimensions. haha



Colors for bottom illustration:
Black - roller
Green - Bearing
Purple - Threaded stud with 19mm hex
Red - interference fit collar

The bearing is directly centered inside the plastic roller. The collar (Red) sticks out past the end of the roller and clamps everything against the arm. (Purple) keeps force on the bearing and makes sure it all stays together. Even though (purple) is slightly smaller than the bearing ID and is a slip fit, (red) puts pressure on each side of the bearing ID and keeps (purple) from spinning inside it.

I'm off to make a prototype right now, and probably put it on my car. Even though the bearing in my current roller feels kinda sloppy, I can make the roller and change the bearing later. As you can tell, it would be very simple to make a roller for a larger bearing if somebody would suggest one.
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Last edited by thechoochlyman; April 6th, 2016 at 13:32.
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Old April 6th, 2016, 12:47   #47
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Unless I'm missing something I'd think more mass on the idler pulley would be a bad thing? The main issue the clutched alternator pulley was trying to solve was too much inertial mass on the serpentine belt which in turn hammers the crank pulley.

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Old April 6th, 2016, 13:01   #48
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The crank doesn't move at constant velocity as it makes a revolution. There sections of movement where it is accelerated rapidly by a combustion event. Just before that though, the force of compressing the air in the cylinder slows the crank down. This radio decel-accel causes the roller to bounce by having the tension varried on the belt and the hard link on the alternator. A clutched pulley allows for this difference in speed in the belt and alloys the alternator to not be slowed down.

A clutched pulley will eventually fail. Mine did, and I replaced it with the ALH one, and when they're fully toast they can become equivalent to a standard pulley. Having more mass on the tensioner roller would reduce belt bounce with solid pulleys. However this then moves the stress over to the belt. If your tensioner spring is old and your belt is bouncing excessively, a heavier pulley would reduce that too. I don't know though if there is a consensus about the addition stress of a heavier pulley on the belt being an okay thing or bad thing.
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Old April 6th, 2016, 13:05   #49
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Quote:
Originally Posted by thechoochlyman View Post
Page break
I believe the larger bearing in the 'large' version is the 6303 where the normal ones are 6203's. There is a pair of either in the roller.
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Old April 7th, 2016, 05:32   #50
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Quote:
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I believe the larger bearing in the 'large' version is the 6303 where the normal ones are 6203's. There is a pair of either in the roller.
The 6303 is 17x47x14 whereas the 6203 is 17x40x12. I suppose you could use two of them in a roller, but the stock roller I pulled from my car uses a single 6203. I need to order a new 6203 for mine, but I may go ahead and get a 6303 as well so I can make a pulley for it. At any rate, I think a single bearing design should be just fine as long as it's high-quality.

I got it finished yesterday, runs and tracks great! It's heaver than stock, but not too heavy. I think aluminum is the perfect material for this part.



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Billet Coolant Flanges - Idler Pulleys - CCV plates - Window Guide Clips
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Old April 7th, 2016, 05:36   #51
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I'd assume This Bearing will work just as well for a replacement in the pulley?
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Old April 7th, 2016, 06:50   #52
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Quote:
Originally Posted by thechoochlyman View Post
The 6303 is 17x47x14 whereas the 6203 is 17x40x12. I suppose you could use two of them in a roller, but the stock roller I pulled from my car uses a single 6203. I need to order a new 6203 for mine, but I may go ahead and get a 6303 as well so I can make a pulley for it. At any rate, I think a single bearing design should be just fine as long as it's high-quality.

I got it finished yesterday, runs and tracks great! It's heaver than stock, but not too heavy. I think aluminum is the perfect material for this part.

[IMG]<snip>[/IMG]

[IMG]<snip>[/IMG]
Are you sure about that? The two that we've posted photos of have 2 bearings each of either size.

Yeah, that bearing can work. It's shielded, not sealed, so dust and moisture will migrate inside it more easily. Have a look at post #2 for sealed bearings. Since it's rather exposed, I'd rather go with a sealed bearing, though in reality, 2RS isn't needed, only RS and have the sealed surfaces facing out.

Reducing end user cost and using 1 bearing isn't a bad idea though, imho.
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Old April 7th, 2016, 07:07   #53
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I'm positive - look back at the photos, none of them have two bearings. If there were two 12mm wide bearings, it would only leave a 1.2mm wall for them to press against in the pulley. My stock one definitely had only one bearing.

Thanks for the reference, I'll look at a different one!
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Billet Coolant Flanges - Idler Pulleys - CCV plates - Window Guide Clips
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Old April 7th, 2016, 07:12   #54
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SKF looks pretty good, but I really think I want to go with the NSK. Shows 12k RPM and all.

EDIT: NSK purchased.
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Old April 7th, 2016, 07:19   #55
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Though you purchased it, and it's not a bad bearing, the SKF is a 19K bearing:
https://www.motionindustries.com/pro...p?sku=00051851
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Old April 7th, 2016, 07:45   #56
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Quote:
Originally Posted by thechoochlyman View Post
I'm positive - look back at the photos, none of them have two bearings. If there were two 12mm wide bearings, it would only leave a 1.2mm wall for them to press against in the pulley. My stock one definitely had only one bearing.
The aftermarket ones do have two smaller bearings in them. The OEM ones have one larger bearing.

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Old April 7th, 2016, 09:27   #57
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I can really see it here now in Dave's picture. Were there any particular brands that had the two small bearings instead of the larger single?

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Old April 7th, 2016, 10:15   #58
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Any of the ones that cost $10 or less with have the small double bearing, inferior setup.
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Old April 13th, 2016, 15:01   #59
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Funny thing happened. I Amazon Prime'd my bearing last Thursday, it got lost in the mail and was already three days past due to arrive. I sent them an email about it yesterday and they shipped out another one with one day shipping. So today they both came in the mail. Can't beat getting a free spare.
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2.5" Straight-pipe exhaust CCV/EGR Deleted Malone Stage 3, 2.0 IQ Autometer Gauges Billet Stuff
Billet Coolant Flanges - Idler Pulleys - CCV plates - Window Guide Clips
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Old April 20th, 2016, 14:34   #60
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Two reasons I haven't bit the bullet on this yet.
1) for $75, I can buy the big bearing version of the plastic roller (for the hub) and a metal roller from Amazon for less
2) don't know the mass difference between the two

How much would producing the hub be? How much does your overall roller weigh? I can loan you my 2 kg scale with 0.1 gram resolution if you'd like.

I may still buy one off you with a reduced diameter since I'm running a larger alternator pulley, thus belt tension is higher.
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