profqwerty - n/a
4-Nov-07, 01:44 PM
Hi,
The tacho has arrived and I have a free day for once, so I have been having a go with the lift engine (Robin EC25PS).
It's a 9/9 set up, in a 550mm duct.
Their 3Z Nylon blades, so the max tip speed is 168m/s
So the radius is 0.275m
so 0.275*2*pi = 1.727m circumference
so 168m/s / 1.727m = 97/s
97/s*60s = 5833
so the fan should be going at about 5800rpm at most.
However this would probably produce >90dba @25m,
so using the regs' recommended limit of 122m/s, that would be 4236m/s.
I will set the blades up so full throttle max's the revs at 5750rpm for a bit of peace of mind, then can use the tacho to keep the revs at 4200 for quiteness.
I just put some old petroil into the for testing and it seemed to produce a lot of smoke, and had oil coming out of the exhaust joint - does the oil separate from the fuel after a bit (i did shake it) or can the fuel go off or something?
Thanks,
Toby
The tacho has arrived and I have a free day for once, so I have been having a go with the lift engine (Robin EC25PS).
It's a 9/9 set up, in a 550mm duct.
Their 3Z Nylon blades, so the max tip speed is 168m/s
So the radius is 0.275m
so 0.275*2*pi = 1.727m circumference
so 168m/s / 1.727m = 97/s
97/s*60s = 5833
so the fan should be going at about 5800rpm at most.
However this would probably produce >90dba @25m,
so using the regs' recommended limit of 122m/s, that would be 4236m/s.
I will set the blades up so full throttle max's the revs at 5750rpm for a bit of peace of mind, then can use the tacho to keep the revs at 4200 for quiteness.
I just put some old petroil into the for testing and it seemed to produce a lot of smoke, and had oil coming out of the exhaust joint - does the oil separate from the fuel after a bit (i did shake it) or can the fuel go off or something?
Thanks,
Toby