I have a PM out to grip grip but if anyone else knows this would the grooves have to be cut when taking off 4mm's? my measurements show the 74mm is the overall, grooves are at lea st 2mm deeper so when we talk 74mm it is the overall so do grooves need to be cut? Thx, Mark

 

I'd have the groves reproduced as close to stock as possible even if it means sacrificing overall diameter.


http://mbworld.org/forums/w211-amg/2...-design-2.html






Don't be this guy: http://mbworld.org/forums/c32-amg-c5...n-today-3.html

 

The OEM pulley grooves are about .135 deep and the rib on the belt is about .08 deep with squarish corners at the root.
You could conceivably make a groove say .11 deep with .020 rads in the corners, the width of the groove, included angle and the radii at the top would have to be the same as the OEM pulley. You would gain .050 on the inside diameter of the groove or you could make the outside groove diameter .05 smaller. It would be weaker because of the smaller radii but ....
You do not want to lose the existing belt contact area or it is a step backward.

 

My stock pulley looks different.
The outside flange is equal in diameter to the grooved section and in your pic your grooved section is deep by a lot. Is that cut from a stock pulley? I would think not or the Crossfire has a different pulley design than my older 2002 SLK32. maybe I should see if Themguy turning mine can just do the grooved section to leave a bit of a ridge, .080", to help keep the belt on?

 

The SLK grooves are not that deep. I measure .090". Shop plans to make a tool to duplicate the stock groove shape and I left him a belt with the fact it needs to sit flat against the pulley after the machining is complete. the grooves measured at the largest diameter after cutting should not be less than 68mm if cut at .090", 2.25mm's.

 

I measured the groove depth (.135") on a shadow graph (10:1) and that dimension should be within a thou or so.
To measure the depth accurately you need to do it this way or use a depth micrometer with a point on it, using a scale does not take into account the radius at the bottom of the groove.
Measured with a engineers scale I get roughly .120" depth, the scale is .040 thick.
I did measure the whole groove profile but my filing system weaknesses allowed me to lose the paper with the sizes on it.

The SLK uses the same pulley I am sure so that is a bit strange.

 

My depth gauge did not have a point. The belt does not go that deep so I guess the depth is a function/result of the tool shape used for the angles.

 

AH! The oops! I cut a little too much, 51mm! Wonder how long that lasted

 

The depth is the result of the radius size and it being tangential to both of the flanks of the groove. A smaller radius would make the groove deeper, a larger radius would make the groove shallower.

 

I think I'll visit that shop today and talk about the grooves. I was thinking about going to 69mm but that would not lave much of the originsl groove left. This is not a shop with CNC machines but an old building(for sale) with 1-2 employees. I got the impression the owner was going to take on the project himself. Anything I should tell him but not get him upset about the level of importance the grooves assume which would be what on a scale of 1-10? I would think if the bely sits flat on the pulley and has as much a degree of friction surface that is possible we should be OK. To me the belt has a strange asymetrical shape, I'll bring glasses. I need to have him get this right as it will save a SC pulley and get the 178/PSK on so much sooner.

 

here is a link to the specs needed for making a cutting tool.
ISCAR Cutting Tools - Metal Working Tools - GPV

However, I would just have a shop that has already successfully done one for a forum member do yours.

my $.02

Chris

 

Hi Chris, which shop is that? I may be interested too.

 

Hi Robert,
I was alluding to shops that have been used by members such as Grip Grip and Jefasold (and others) successfully as OPPOSED to a shop that has never done it before. While a shop that has CNC equipment is not required ... it is desired.

As you well know, this pulley (and the patch of belt it is in contact with at any given instant) is trying to transfer 30-60 horsepower in order to compress the air (and subsequently burn the rubber off our tires )
However, some don't know how critical the pulley groove profile is to this .... hence my 2 cents

Cheers,
Chris

 

And I just thought that you would save me some time and recommend a shop I can use. But thank you anyway.

 

I would if I could . I don't know what Jefasold paid, but Grip paid under 150 for his second one and that seems like a fair price. The pulley is worth more than $300, no sense in taking chances on trashing it.

Cheers,
Chris

 

Well, I think I need a diFferent shop. When looking at everything as a whole I agree on not taking a chance. Now to find that shop Anthony used......

 

https://www.crossfireforum.org/forum...tml#post654958

here is the invoice for his first ... the second was $140

fc4f5499.jpg

 

Anthony used that shop almost 4 years ago. Can't hurt to call and ask

 

That number, 1-615-672-0122 is no longer in service. Have I got the number correct?

 

Any other shops that are sure to cut a pulley correctly? I'd love the 70mm I was hoping for. Mark