Helical gears???????
11-07-2009, 03:28 PM
#1
Helical gears???????
Has anyone ever heard of using helical gears for rc cars like the tc3??????I read they are stronger,more quiet,and have more contact.
11-07-2009, 04:49 PM
#2
TC3 doesn't use the helical gears if I remember correctly (the BJ4WE I used to have used TC3 transmissions).
Do you mean the crown and bevel spur gear setup? I thought all shaft-driven 4wd uses this scheme (even in off-road).
Helical gears, to my knowledge, is the gear type that is used on the Tamiya 801x Nitro.
Where it's similar to the TC3's crown and bevel, but instead of the teeth being straight, it is curved...
I don't have an 801 pic for you but this is what I'm talking about:
The gears are just like crown and bevel, but they are curved, since it's "HELICal"
I believe mechanically, this forces efficiency only in one direction...
Do you mean the crown and bevel spur gear setup? I thought all shaft-driven 4wd uses this scheme (even in off-road).
Helical gears, to my knowledge, is the gear type that is used on the Tamiya 801x Nitro.
Where it's similar to the TC3's crown and bevel, but instead of the teeth being straight, it is curved...
I don't have an 801 pic for you but this is what I'm talking about:
The gears are just like crown and bevel, but they are curved, since it's "HELICal"
I believe mechanically, this forces efficiency only in one direction...
11-07-2009, 06:30 PM
#3
Tech Apprentice
Hey... I think he's asking if he knows of anyone who has tried to use helical gears in a tc3 - not stating that the tc3 uses them
11-07-2009, 08:40 PM
#4
They are used in some 1/8th offroad buggies. The only 1/10th 4wd electric that I know of that used helical cut gears in the front and rear gearbox was the old Tenth Technology Predator series. Dunno if they still do or not. Not really worth it, IMO. Molding/machining the gears would cost a good bit more, and the increased surface contact of each tooth actually creates more friction and more drivetrain loss. Probably not worth it for a bit smoother drivertrain and a little more strength in the teeth. Probably be less tolerant to gear lash adjustments too, compared to straight cut gears.
11-09-2009, 11:25 AM
#5
I did mean helical gears to replace the spur and pinion gear......would it really cost a noticeable amount of friction increase and decrease in drive train power?I was looking at my tc3s 72T spur & it looks chewed up a little.Im trying a new set up and want a smooth drive.Maybe it will help with decreasing motor vibration as well,smooth pinion action smooth armature revs.Idk im just asking.
11-09-2009, 01:06 PM
#6
Tech Fanatic
Helical gears for the spur and pinion would require the use of thrust races in the system, adding to cost, weight and drag. When a straight-cut gear is in operation, the resultant force drives the gears apart against the bearings already in use in the motor and drive shaft.
When a helical gear is under load, the resultant force drives the gears apart in a side load/motion that would push the driveshaft against the drive cups. Some sort of thrust race would be needed to prevent it jamming into one end. Same for the motor, the helical will push/pull the armature/rotor to one end of the motor putting end loads on a bearing designed for radial loads.
A double helical spur/pinion would contain those forces and prevent side loads, but that's a complex thing to design and mould accurately.
If helical gears were used in the gearboxes (as bevel gears) then because the tooth contact is greater, the gears could be smaller. Smaller gears would reduce the drag. It's all about tooth loading. The more teeth in contact during power transfer, the smaller the contact area of each tooth needs to be. Helical bevel gears are used in applications where size is important (as they can be smaller than straight-cut) or where noise is an issue (because they are quieter).
Hypoid bevels are used where height is an issue, as the pinion can run a centreline below the centreline of the crownwheel. Hypoid bevels are usually used in automotive applications.
All in all, the straight-cut design is more than adequate to deal with RC loads, and we are not usually worried by noise or driveline height. That helical gears can be more efficient than their straight-cut equivalents is well proven, but the cost and complication for RC just isn't worth the effort. HTH
When a helical gear is under load, the resultant force drives the gears apart in a side load/motion that would push the driveshaft against the drive cups. Some sort of thrust race would be needed to prevent it jamming into one end. Same for the motor, the helical will push/pull the armature/rotor to one end of the motor putting end loads on a bearing designed for radial loads.
A double helical spur/pinion would contain those forces and prevent side loads, but that's a complex thing to design and mould accurately.
If helical gears were used in the gearboxes (as bevel gears) then because the tooth contact is greater, the gears could be smaller. Smaller gears would reduce the drag. It's all about tooth loading. The more teeth in contact during power transfer, the smaller the contact area of each tooth needs to be. Helical bevel gears are used in applications where size is important (as they can be smaller than straight-cut) or where noise is an issue (because they are quieter).
Hypoid bevels are used where height is an issue, as the pinion can run a centreline below the centreline of the crownwheel. Hypoid bevels are usually used in automotive applications.
All in all, the straight-cut design is more than adequate to deal with RC loads, and we are not usually worried by noise or driveline height. That helical gears can be more efficient than their straight-cut equivalents is well proven, but the cost and complication for RC just isn't worth the effort. HTH
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