Gears

[Raygun]

Hi I was just wondering are there any heli's out there with helical cut gears instead of straight cut gears?? The helical gears are stronger and so quiet you would never get any gear train noise. I was just wondering why they are not in greater use when there not really any harder to make. Ray

[McKrackin]

Do you mean beveled gears?Like the teeth are slanted on the main gear and coiled around the pinion?

[Raygun]

Yes something like that any slant of the gear tooth would be helpful like a ring and pinion in a car rear end. Ray

[McKrackin]

Sure.Most of my Walkera helis had this type drive.

[McKrackin]

[lowbudget]

helical cut gears put a strain between the gears trying to push the pinion outward away from the ring gear which causes more drag - flat bushings or tapered bearings are really needed to combat the drag factor = VIC

[BTCat]

Mar 9, 2009 19:47:23 GMT -6 lowbudget said:

helical cut gears put a strain between the gears trying to push the pinion outward away from the ring gear which causes more drag - flat bushings or tapered bearings are really needed to combat the drag factor = VIC

Yea this is an area where I have some real world experience. Mine on the mechanical (and minor engineering) side and I think RAY (or maybe RFT?? All you people look the same to me ) has experience on the machining side. "Helical cut" I believe is the officially accepted term. It's the one I use. But I see it called bevel cut all the time in the heli world too. Bevel cut to me is more like the input gear (pinion) on a car differential. It would be more for laying the motor sideways and driving a ringgear.

Lowbudget is right. Helical cut gears do have more thrust force (upward or downward depending upon the drive direction). Whereas straight cut primarily side-load. The advantage of Helical cut is two fold. First they are quieter. Second, they offer more contact surface area allowing more power to be transfered between the motor and the gear without breaking or prematurely wearing one or the other. I don't know if the manufacturers are addressing the thrust load issue (it would be simple and cheap), but if they are, the helical would seem to be the way to go.

Now, since none of that addresses the original question: As usual, McKracken is right. Most of the Walkera's I looked at had helical cut gears and they advertise it as being for better power transfer.

[BTCat]

A thought occured to me. The dam main blades are a huge source of thrust load .... DUH. So the heilical cut gears would seem to offer very few negatives.

[McKrackin]

The only difference I ever noticed was that I never ever stripped one BUT!!!,,,!!!,when building an ARF,the pinion was just this side of impossible to find

[Raygun]

I was just wondering thanks Ernie for the picture they appear to me they would be better I use to make gears when needed but not that small and there are some negatives but the positives kind of balance them out. Ray

[lowbudget]

would rc cars or trucks have that type of setup = VIC

[19000rpm]

Ray's right...at least when it comes to gears. OK, he's right about almost everything. ;D

The ring and and pinion, helical gear, approach is much stronger and less apt to strip, as ernie has experienced, because of the increased contact area of both of the gear's teeth as they mesh. That also causes more drag too, but in high torque applications the helical benefits far outweighs the increase of the drag. IMHO all heli gears should be made this way as long as there is sufficient motor torque and RPM to overcome the added drag.

Happy landings