12H pulleys - machine or replace?

[Scrub Basher]

I'm running a Series I 12H. The countershaft, fan and alternator pulleys are worn out. I can get the countershaft and fan pulleys machined down and a new steel pulley made to replace the worn cast alternator pulley for about $1100 AUD less than buying all new pulleys from Caterpillar...but the countershaft and fan pulley diameter will be reduced slightly by the machining process. The new alternator pulley can be made a little oversize to compensate for the reduced diameter of the other pulleys so the standard v-belts can be used.

Question: can you see any problems with going down the path of slightly undersize countershaft and fan pulleys and a slightly oversize alternator pulley?

 

[Nige]

Personally I would always suggest to use either OEM or aftermarket parts manufactured to OEM dimensions.

In your case I would ask what ambient temperatures you work in and are cooling system temperatures an issue.? Then segue into whether or not it might be advantageous to try to skew the pulley dimensions in your favour and maybe increase the fan speed by say 5%.? This might mean the need to buy either a new fan or a new countershaft pulley.
I dunno, just trying to think outside the box here.

 

[Scrub Basher]

Personally I would always suggest to use either OEM or aftermarket parts manufactured to OEM dimensions.

In your case I would ask what ambient temperatures you work in and are cooling system temperatures an issue.? Then segue into whether or not it might be advantageous to try to skew the pulley dimensions in your favour and maybe increase the fan speed by say 5%.? This might mean the need to buy either a new fan or a new countershaft pulley.
I dunno, just trying to think outside the box here.

Thanks for your input Nige.

Ambient temperatures are anything up to about 45 degrees centigrade. On top of that, the leaking countershaft seal + fan has been spraying a little oil onto the aircon condenser, which has subsequently attracted dust and blocked part of the condenser, and yet will all of this the machine has never overheated - the temp gauge always sits at about 90 degrees (and I have been putting up with this leak for 3 Australian summers).

I'm thinking that reducing the diameter of the countershaft pulley and fan pulley would more or less cancel each other out in terms of increasing or decreasing fan speed, and the main change would be that the alternator would spin at slightly lower RPM - but given that the machine operates for hours and hours at a time I can't see that it will run out of spark...

 

[Blue-Fox]

Thanks for your input Nige.

Ambient temperatures are anything up to about 45 degrees centigrade. On top of that, the leaking countershaft seal + fan has been spraying a little oil onto the aircon condenser, which has subsequently attracted dust and blocked part of the condenser, and yet will all of this the machine has never overheated - the temp gauge always sits at about 90 degrees (and I have been putting up with this leak for 3 Australian summers).

I'm thinking that reducing the diameter of the countershaft pulley and fan pulley would more or less cancel each other out in terms of increasing or decreasing fan speed, and the main change would be that the alternator would spin at slightly lower RPM - but given that the machine operates for hours and hours at a time I can't see that it will run out of spark...

Im not familiar with the 12H, but I have 2 12G models and If its enough rpm change to the ALT pulley slows down you will have to rev up the motor to "field" the alternator (cold) and begin to charge if she will not charge at idle. Usually once excited they will carry the charge. BUT Due to that snake lying in the grass to bite you later I would look into possibly swapping out an idler or adding onto the idler and remachine to keep ALT size vs ading pulley circumference to the ALT. Slowing the ALT is a bad idea. (But I live in the frozen wasteland where charging batteries right off the hit might mean the difference between live or die in remote AK)