I have recently milled my rotor tips out with a 3mm brand new 3 flute cobalt end mill exactly on cente line of the original 2mm slot.
the slot grooves measure 3.05mm using calibrtaed slip blocks to measure the slots ie this is 0.0017" plus the nominal 3mm size.
the 3mm apex seals are 2.94mm ie 0.0023" under 3mm nominal size.
therefore total clearence will be 0.004"for my 3mm tip in my groove.
is this in tolerance or should i give the tips more clearence?
on the rebuild vid i have it says no more than 0.006" clearence but thats for 2mm tips.
I think it would depend on the coefficients of expansion for the tip and the rotor, you need enough clearance to cope with the transient conditions at startup and shut down as well as when the engine is running.
I would contact the maker of the seals and get them to recommend a clearance, it is afterall in thier interest to make sure there product works as well as it can in your engine.
all standard 2mm grooves where bang on 2mm, tight with a slip block
all standard 2mm apex seals are 1.92mm which gives 0.08mm clearence or 0.003" clearence in a tight 2mm dead size groove.
like you said mike a 3mm tip will expand more than a 2mm tip, this is why i want to make sure before rebuild.
the tips are from atkins but they dont like replying emails!
i asked them in an email last week
The rotor also expands too.Same max clearance works well.
Regards
Carl
On my race motors I used the clearence specs of 0.065mm+- 0.005mm,this was on one piece carbon apex seals.
oldone thats .002" clearence (+.065mm)
carbon wont expand like steel though.
my old apex seals where very loose in there 2mm grooves when i took them out but the grooves where dead size 2mm.
it seems to me that the groove has to be dead size 3mm or near as damit because all the seals are made undersize for clearence.
pts seals in aus make there 3mm seals to 2.92mm which is .003" under nominal size to start with, also they do the same for 2mm seals which are 1.92mm.
so my 3mm seals will be around .005" clearence
But if you use Carbon seals,they take on the shape of the groove\\slot that is why they will be loose in the slot...carbon is softer than steel and does not expand like the other materials.Personal feeling,I like the apex seal to be softer than the housings...rather let the seal wear than the housing.On the latest space age materials the seal is so hard that it wears the housing rather than the seal......personal taste I would say ;)
I thought that there wernt any carbon seals available to use with high boost as they cant take the pressure. Which is why people use steel ones.? Am I wrong?
cheers, michael.