ORIGINAL: phase5
I have spoke with SMT over the phone a few times, they are going to a event in GA shortly and will have the engines on stands to do side by side comparisons to other brand speed engines ( As all of you know I'm new to the speed bug don't know the tech name of the devise used to measure trust ) I'm going to try a few of them out although I may not be the most qualified to give test result I will be honesty about my results good or bad
Not to repeat what CP said, but static thrust measurements for speed applications are totally meaningless. The only thing that matters is how much thrust the prop produces at flight speed. The angle of attack of a propellor at any specific rpm varies with the forward speed, therefore the efficiency varies throughout the flight regime. A small high pitch prop is running at or near stalled condition on the test stand, stirring a lot of air in meaningless directions. The prop giving the highest static thrust could easily be the worst choice - to exaggerate the example, think 11-4 versus 9-8.
How would you compare a .50 that is tuned for peak horsepower at 17k rpm, to one tuned for peak horsepower at 21k? Would you put the same prop on them, for example a 10-6, and compare? The higher timed engine might spin it more slowly than the other - but, prop it for peak rpm and it may develop more power than the lower timed engine.
Speed comes from horsepower - not torque alone, not rpm alone - the product of the two, PLUS - a prop matched to the engine and appropriate for the airframe at the same time. Put 200hp in a Honda Civic and you can gear it for 150mph, but put 200hp in a pickup truck and you can't run the same gearing. But they will both do the same amount of
work in the same time.
A good example might be an OS .50-whatever to a West .50 - bolt an 11-6 to each and see what happens.. my guess is the OS wins the static thrust battle. So which one can fly your airplane faster..? Which one has the highest peak horsepower?
You can make a somewhat meaningful comparison between engines designed for similar operating rpm by running a common prop on each. In that case, rpm is the litmus test.
I'm not pooh-poohing the test stand comparison, but I am suggesting that you be thoughtful about how you evaluate. Honest as they may be, there are many ways to set up a side-by-side comparison to make your products look good. That said, I am quite sure they are great running, high quality engines. Will be fun to see the demo.