Above is a job comparison from 1926, put together by the firm Proctor and Cleghorn of Santa Rosa, CA, showing the Vulcan #2–to say nothing of the #1 also–significantly outperforming the MKT 9B2 (which they superseded with the 9B3) driving concrete piles. Vulcan obtained this data from Harron, Rickard & McCone, Vulcan’s dealer in California. (They were mentioned in a Vulcan ad the same year.)
Although the results shown are pretty sketchy, some kind of attempt needs to be made to explain this. The 9B2 had a rated striking energy of 8,750 ft-lbs while the #2 has one of 7,260 ft-lbs. By a pure energy competition, the 9B2 should have done better. The main reason probably has to do with the prime mover used on the job.
The rig had a 35 HP Mead-Morrison boiler. That’s enough for the #2 (nominal 25 HP,) but not the 9B2 (nominal 45 HP) or for that matter the #1 (nominal 40 HP.) The result of that is borne out in the note on the right: the #2 had to stop after 30 minutes for the boiler to get up a new “head of steam” (repressurise the steam drum) while the 9B2 would not “hold up” after half that time. The #1 did better but “would not hold up to full capacity of pile hammer,” which probably means that it didn’t achieve full stroke. (Since it had 15,000 ft-lbs of rated energy, that may not have been a problem for the 20′ long piles.) That underscores the importance, then and now, for an external combustion hammer to have a large enough power source–and a reservoir for the intermittent feed–to keep it running at full energy. It’s very likely that the 9B2 may never have attained full rated energy during operation, which was harder to see with the 9B2 since the hammer is closed and you can’t see the ram stroke. With a Vulcan full stroke is obvious with the open construction, one reason why operators and engineers preferred it.
It’s also worth noting that one of the piles was “broken” after it was started with the 9B2 and finished with the #1. Breaking concrete pile during driving–especially in the middle of the pile–was a phenomenon that took the pile driving world by surprise. It wasn’t until the early 1930’s, with the pioneering work on the wave equation by David Victor Isaacs in Australia, that this phenomenon was better understood, but it took another half century for that understanding to be translated into really more effective pile driving.
The strength of the Vulcan design is that it is versatile enough to be adapted to many types of piles, most of which were invented after its introduction. The 9B2–and now the 9B3–is better suited for steel piles (especially in its cushionless mode) and those which need to be driven without leaders.
These days, both the Vulcan #2 and the MKT 9B3 are supported by Vulcan Foundation Equipment.
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