cam chain tensioner shoe - can it be improved?

[Goran]

Hello,

I know they rarely go wrong, and can last over 300k miles, but I cant help wondering if they could be made from better material?
It would be nice to replace them with better ones when doing the cam cover gaskets at some point in the future.

Would aluminium be a bad choice because it would cause wear on the cam chain? (aluminium being tougher than the nylon plastic used on oem shoe).
Also I guess the chain running over an aluminium shoe would generate a lot of aluminium dust which would end up in the oil.

Is there a better plastic that bends rather than breaks, and that would not become brittle from heat inside the engine? I read about glass reinforced nylon would that be good?

Just out of curiosity I bought one of these from ebay, I'm going to do some destructive testing on it to see if its any good.

http://www.ebay.co.uk/itm/Vw-Audi-ec...37252755803325

[Goran]

I have been searching around and a picture from this website gave me an idea. If someone could make us a aluminium or steel casting with the plastic wear surface locked in like in this picture, it would be unable to brake off at the edge.

http://www.murtfeldt.com/products/ch...el-c-profiles/


some more info (I'm bored )

http://www.eng-tips.com/viewthread.c...=292501&page=1

so from the above it appears the Audi geniune ones that are creamy in colour are probably made of Nylon 4.6 (the better stuff) and the darker colour aftermarket ones are probaby the older type of Nylon 6.6 with added graphite as per above forum. However those assumptions are just based on the colour of the different pads.

[Goran]

Another find. Porsche pads appear to be almost the same as our pads. Except ring on bottom one and no holes. I'm hoipng to get a couple to see if they are are the same dimension wise, a hole is easy to drill if needed.

Porsche pads are different, they dont fit Audi variator!
//Maybe another option for replacement with a genuie OEM part since Audi wont sell us their pads individually.
//UK:http://type911shop.co.uk/shop/articl...6aid%3D2887%26
//States:http://www.koperformance.com/part-nu...ENUINE-PORSCHE
//Porsche part no. is 99610525300
Porsche pads are different, they dont fit Audi variator!

Does anyone know what the hole is for on our pads? is there a oil squirter or someting in the variator body that squirts oil through that hole or something?



Message for Nollywood: please ask your engineering friend who may make pads for us to look into Stanyl Diablo (recently selected by Fiat) and Duratron CU60 (apparently one of the toughest high-temperature plastics).

http://www.quadrantplastics.com/eu-e...ron-R-pbi.html

http://www.dsm.com/en_US/html/dep/ne...nyl_diablo.htm

[Goran]

more info. Stanyl are still pushing PA46 as the way to go for chain tensioners. Looks like they are the suppliers to the factory that casts the chain tensioner pads (still havent found out who that is, could it be Borg-Warner?). Although I could be worng, other factories make a material called PA46 too but with different properties, for example:

http://www.piedmontplastics.com/prod...n-46-pa46.aspx
300F is only 148C, not much above engine operating temperature.


http://www.dsm.com/en_US/automotive/...ng_systems.jsp
"The material gives you solid performance across the engine’s lifetime when dealing with high chain tension"

I have to disagree with them, the pad failures that have been posted so far is proof to me that PA46 starts losing its structural properties after approx 100,000miles in a engine oil environment, which is hardly the lifetime of the engine. Unless our pads are made of some other weaker PA46?

[Goran]

I posted on the Porsche forum, they say that Porsche updated the material for their pads.

http://986forum.com/forums/performan...-cleaning.html

*edit* - I received the Porsche pads, they look very nice but shape is different they wont fit Audi variator

[Nollywood]

The best way to improve would be if the tensioners have three rollers (sprockets) for the chains to ride on. Less friction, though would be quite expensive to engineer as aftermarket items.

[Goran]

rollers or sprockets are an excellent idea. Unfortunately the cheapest design option, replacing the pad with rollers without re-designing the variator body, is a bit space limited. The pads are only 7.5mm high above (and below) the variator body plate, leaving room only for small rollers (so really 5 needed ideally), with worryingly thin material thickness available. For example, roller drum (plastic) 2mm thick. Roller shaft (steel) 3mm thick. Roller bracket/frame (steel), thinnest point 1mm.
Here is a quick snapshot of the drawing I was preparing for the machining of pads out of a better material.

! Also, I received the Porsche pads unfortunately they are the wrong dimension, dont buy !

[Goran]

interesting post on the A4 forum. McGyver fix

http://forums.audiworld.com/showthre...=349969&page=3

[Goran]

Here are cad drawings hopefully detailed enough for machining chain tensioner pads from better material. One is the 'original' pad, dimensions taken from a Chinese copy pad bought from ebay. The other is a simplified version.
Use at your own risk, I take no responsibility if dimensions turn out to be wrong, always verify dimensions from Audi original pads or the mounting plate on the cam variator.

[Goran]

Me again
I wanted to check dimensions of the variator, so I got a cheap used A6 variotor from Ebay. Also allows me to practice putting on the macined pads (if I ever manage to convince someone to make them for me from that tough material).
The pads on this variator (mileage unknown) seem to be in pretty good shape, not too worn. I took one off a couple of times and it didnt brake.
If only Audi sold the pads separately I would be quite happy to stick in a set of new original Audi pads and change them again in another 100k miles.

Dimensions of pad mounting plate are 51mm x 14mm x 5mm, so the drawings I posted before seem to have the right dimesions for the mounting section.

The piston of this variator just comes out by itself, doesnt seem to have the locking pin that our variators are supposed to have that only release with sufficient oil pressure.