ASTM D 4633-86 outlines procedures to use to compute the energy delivered using nonstandard weights and samplers. The standard was withdrawn in 1995, so you may have to do some hunting in older ASTM books to find a copy.

Not having a copy of the D 4633 standard myself, first principles suggest that we can look at the amount of energy delivered to the soil by a larger sampler and heavier weight. The energy delivered to the soil will equal the change in potential energy. Thus

E = m*g*deltaH = W*deltaH

where W is the weight of the hammer and deltaH is the drop distance of the weight onto the anvil.

The sampler will transmit the energy of the hammer to the soil (neglecting friction effects) around the circumference of the sampler. So we get

Eavg = W*deltaH/(pi*D)

where D is the diameter of the sampler and pi is 3.14159...

If you compare the ratio of average energies transmitted to the soil, you should work out a fair approximation of the conversion factor.

Unless my reasoning is not quite there, in which case I will be pleased to learn of a better solution.

Hope this helps.

Jeffrey T. Donville, PE
TTL Associates, Inc.
www.ttlassoc.com

We went through this on another thread something like 15 responses - There is a good graph/table in Fang's Foundation Engineering Handbook (the big tome - formely Winterkorn and Fang) - it is in the chapter on site investgations.  They have how to standardize for any size hammer and spoon size.  Do a search on threads and you may find the older one.  If I find it, I'll advise.

Thread261-82930

Thanks for the info and tip to older post.  Problem solved.