same tooth count on the main gears
Actually, helical gears use larger teeth than a straight cut gear, so there are less of them. However, your final drive ratio will be almost identical since the circumference is pretty much the same on the two main gears.
What helicopter is this? Do you happen to know the main gear tooth count (straight and helical) and the pinion tooth count (straight and helical)?
Tony,
Helical teeth aren't always larger than straight teeth. D.O.G. already said in post #3 that the tooth count was the same.
FWIW the tooth size is specified by the 'Modulus' (typically something like M0.6 , M0.8 or whatever) which is the number of teeth on the gear divided by the gear diameter. You must always make sure that both meshing gears have the same modulus.
EDIT.. well it seems from post #7 like the tooth count isn't actually the same, so all bets are off! By keeping the same tooth pinion and reducing the main gear tooth count the reduction will be much less, so your RPM will go up a lot. If you want to keep the same RPM then you need to fit a smaller pinion, the calc says 10.5 tooth, which is obviously immpossible so either 10 or 11 depending on if you want a small increase or decrease in RPM.
Tony,
Helical teeth aren't always larger than straight teeth. D.O.G. already said in post #3 that the tooth count was the same.
FWIW the tooth size is specified by the 'Modulus' (typically something like M0.6 , M0.8 or whatever) which is the number of teeth on the gear divided by the gear diameter. You must always make sure that both meshing gears have the same modulus.
EDIT.. well it seems from post #7 like the tooth count isn't actually the same, so all bets are off! By keeping the same tooth pinion and reducing the main gear tooth count the reduction will be much less, so your RPM will go up a lot. If you want to keep the same RPM then you need to fit a smaller pinion, the calc says 10.5 tooth, which is obviously immpossible so either 10 or 11 depending on if you want a small increase or decrease in RPM.
Helical just means slanted. Not a brand. With the straight cut gears you are at a 11.538 and on the helical you are at 9.307. You need to run an 11 tooth pinion to get the head speed back down. With an 11 tooth pinion you will still have a slightly higher head speed since the motor will be turning a half turn less per revolution of the main head. If you want more torque then go with a 10 tooth pinion.