With the engine running very well I brought the power turbine up to about 14,000 RPM. This put the drive shaft and brake drum at 2,800 RPM. I applied pressure to the brake while adding power to compensate for the drag. After three or four tries I balanced the RPM with the drag of the brake. Without going over 15 PSI combustor pressure or 925 deg. Fahr. EGT, I was able to produce 11.5 foot-pounds of torque @ 2,800 RPM.
By using the horsepower formula:
Horsepower = Torque (in lb-ft) x RPM 5,252
11.5 lb-ft x 2,800 RPM = 32,200
32,200 / 5,252 = 6.13 HP
I finally have the number I was looking for and not too shabby for a scrap pipe power turbine. I feel that 6.13 horse is enough to drive a ground based vehicle fairly well but not at the speed of sound. I was not surprised or disappointed at this measurement but it at least it is done and I can publish the horsepower rating at 6.13 HP @ 2,800 RPM*. I had messed around with different RPM/torque ratios and found that the higher RPM produced the most torque so without flogging the engine, this is a good conservative rating. *Further testing at a later date revealed that the GR-5A can produce 8 SHP @ 3600 RPM. See the GR-5A Demo Video.
I am sure with some adjustments that I could get a few more HP out of the GR-5 but it could take a toll on the engine over time. I am just happy the the engine is running very stable and should be a great power plant for a vehicle of some kind. The next step is designing a vehicle to put the engine on so I can cruise around the block.
Till the next time..............
Don Giandomenico, Part-time gas turbine engineer :0)