Quote:
Originally Posted by BURN-BROS
Are the numbers right on the spreadsheet
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Aaron, I agree with this observation and I have serious doubts about the validity of this data.
A typical engineering steel would have an expansion of about 13 ppm/degC rather than 10.
All Auminium alloys I have knowledge of have a figure of at least 19ppm/degC and 21 would be a more realistic estimate for an alloy with relatively low Silicon.
Elektron (Magnesium) Alloys are more likely to be around 25ppm/degC
I belive Dilavar is about 18 ppm/degC
17-4PH (Precipitation Hardened Martensitic Stainless Steel) is about 10.8 pp/degC
All of this expansion data is based on measurements taken at 20 degC and there will be some minor variations at 200 degC but similar trends would be observed.
I beleive that clamping force increases with temperature in all cases.
Clearly in the case of Dilavar this increase is relativley low and if you only use Dilavar on the lower studs there will be an uneven distribution of force on the studs and barrels. I am not sure this is entirely christian and not something I would generally recommend.
The 'standard' steel stud would give a moderate increase in clamping force and the 17-4PH the highest increase.
It is interesting that ARP's 'best' material is Age 625 and this an 'Inconel' type alloy which is Nickel based and offers extremely good high temperature properties but has a typican expansion of 13ppm/degC and is very similar to a standard steel stud.
Just for interest Titanium 6AL4V a typical alloy used in race cars has an expansion of about 9.5ppm/degC.