Bosch Alternator Rebuild Info

TDIDaveNH

Left Lane Coal Roller at Large
Joined
Feb 17, 2009
Location
North Conway, NH
TDI
'97 Passat x2
Good find DC, but the hex end of the 15mm hub is only 17mm and responsible for holding the pulley away from the engine and would have only the points of the hex doing that job, which are also chamfered if you look closely. There are 40mm OD by 15mm ID bearings out there or a small-scale group buy here
I never like rigging stuff up baby-carriage stye...as a last resort, this is an option as well
 
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Digital Corpus

Top Post Dawg
Joined
Mar 14, 2008
Location
Ontario, California
TDI
'97 B4 w/ 236K mi body, 46K mi soul
Or you can stack a washer against the hex side, no? I'll keep those links in mind since I've not had a chance to search for the odd-size bearings yet.
 

TDIDaveNH

Left Lane Coal Roller at Large
Joined
Feb 17, 2009
Location
North Conway, NH
TDI
'97 Passat x2
Yup, the simple solutions seem to elude me right away, lol. I edited my last post with a link for some 19mm hex stock to make these on a lathe.
 

TDIDaveNH

Left Lane Coal Roller at Large
Joined
Feb 17, 2009
Location
North Conway, NH
TDI
'97 Passat x2
I don't think I would use aluminum just on the basis of thread strength.
I guess the Gates version of 028145278A also has the 17mm hub. Abacus bought one recently through Amazon but when I checked on it a couple days ago, all there was was ones with the 15mm hub by other manufacturers So evidently they are still available but you do have to do some online digging and scrutinize photos closely.

I do know the ones made by Meyle are 15mm but have not researched others
 

Digital Corpus

Top Post Dawg
Joined
Mar 14, 2008
Location
Ontario, California
TDI
'97 B4 w/ 236K mi body, 46K mi soul
Well, for about 2x the cost, there is grade 7075 aluminum that can be use, fwiw.

At quick google search, since 0.75" = 19.275mm, yields several inexpensive options compared to your first link. All of those are 3' lengths for less than $20.

I've not had a chance to go over the rollers just yet...

Just finished doing an update for the carbon/graphite brushes a little while ago. It's hard to find anything not on eBay or produced in the US that isn't stupendously expensive, $60 ea., so I'm open to other sources.
 
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Digital Corpus

Top Post Dawg
Joined
Mar 14, 2008
Location
Ontario, California
TDI
'97 B4 w/ 236K mi body, 46K mi soul
Updated prices and added the recent Dayco Roller. Come tax return season, I'm going to have some disposable income so I'll be picking up a couple of these to confirm dimensions and fitment for the sake of thoroughness.
 

thechoochlyman

Vendor , w/Business number
Joined
May 7, 2015
Location
Campbellsville, Kentucky
TDI
1997 B4 Sedan
Is there any interest for me making some stainless steel idler pulleys? Or whatever material you like, for that matter. Dave - what exactly are you suggesting about getting a larger, stronger bearing and building a pulley around it? I can do exactly that with no issues. I was approached a while back about making the 17mm spacer sleeves, and I feel like revisiting it now.
 

Digital Corpus

Top Post Dawg
Joined
Mar 14, 2008
Location
Ontario, California
TDI
'97 B4 w/ 236K mi body, 46K mi soul
Yeah, sorry for not following through about the hub ideal that long while back.

I myself wouldn't want an aluminum pulley unless it's heavier than the stock one. The stainless one is a nice idea, but what alloy would be used to help with cost? I don't know if I'm the only one who wants the inertia benefit from a heavier pulley.
 

thechoochlyman

Vendor , w/Business number
Joined
May 7, 2015
Location
Campbellsville, Kentucky
TDI
1997 B4 Sedan
Aluminum would definitely be heavier than the plastic one with all the speed holes in it. I'll have to check on cost for stainless roundstock that size and see how much it compares with other options. I won't be doing anything fancy with it, just turning it down enough to work without hitting anything. The more material left, the better - at least as far as inertia is concerned.
 

thechoochlyman

Vendor , w/Business number
Joined
May 7, 2015
Location
Campbellsville, Kentucky
TDI
1997 B4 Sedan
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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vanbcguy

Veteran Member
Joined
Feb 22, 2013
Location
Vancouver, BC
TDI
'93 Passat - AHU mTDI with GTB1756VK
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.

Sent from my XT1097 using Tapatalk
 

Digital Corpus

Top Post Dawg
Joined
Mar 14, 2008
Location
Ontario, California
TDI
'97 B4 w/ 236K mi body, 46K mi soul
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.
 

thechoochlyman

Vendor , w/Business number
Joined
May 7, 2015
Location
Campbellsville, Kentucky
TDI
1997 B4 Sedan
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.



 

Digital Corpus

Top Post Dawg
Joined
Mar 14, 2008
Location
Ontario, California
TDI
'97 B4 w/ 236K mi body, 46K mi soul
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.



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.
 

thechoochlyman

Vendor , w/Business number
Joined
May 7, 2015
Location
Campbellsville, Kentucky
TDI
1997 B4 Sedan
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!
 

Abacus

That helpful B4 guy
Joined
Nov 10, 2007
Location
Relocated from Maine to Dewey, AZ
TDI
Only the B4V left
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.

 

thechoochlyman

Vendor , w/Business number
Joined
May 7, 2015
Location
Campbellsville, Kentucky
TDI
1997 B4 Sedan
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.
 

Digital Corpus

Top Post Dawg
Joined
Mar 14, 2008
Location
Ontario, California
TDI
'97 B4 w/ 236K mi body, 46K mi soul
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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