Helix Angle

ok related question would a helical gear set be able to be meshed and unmeshed on the fly or does that take some more magic sauce? like the h/l gear set up in some of the cheap asian mills/lathes?
 
Yes, in some cases. If a gear set is going the same speed they can be slipped in or out of gear... People do it all the time shifting gears in a standard transmission without using the clutch by just matching the engine speed to the rolling speed of the gear train....... Is it recommended? A) no Can it damage gears? A) Yes

My clutch cable broke on my motorcycle when I was in town right near the highway. I started the bike and pushed it to get it going then gingerly slipped it into first gear with a clunk. Once I sped up, I put my foot on the shift lever with slight pressure and when I checked the throttle it slipped nicely into second gear. I did this all the way home without any nasty sounding clunks or grinding....

Half nuts are a good example of helical gear interfaces that are engaged and disengaged on the fly...
 
o0norton0o said:
Yes, in some cases. If a gear set is going the same speed they can be slipped in or out of gear... People do it all the time shifting gears in a standard transmission without using the clutch by just matching the engine speed to the rolling speed of the gear train....... Is it recommended? A) no Can it damage gears? A) Yes

My clutch cable broke on my motorcycle when I was in town right near the highway. I started the bike and pushed it to get it going then gingerly slipped it into first gear with a clunk. Once I sped up, I put my foot on the shift lever with slight pressure and when I checked the throttle it slipped nicely into second gear. I did this all the way home without any nasty sounding clunks or grinding....

Half nuts are a good example of helical gear interfaces that are engaged and disengaged on the fly...
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thanks for the reply and I know that they can be engaged/dis-engaged, let me rephrase the question, are there disadvantages to meshing helical gears in place of straight spur gears on a mini mill transmission H/L range selector?
 
Any time you engage gears on the fly, you risk the possibility of damage. That holds for both spur gears and helical gears. Automotive transmissions have synchronizers the match tha speed of the gears prior to engagement. I took the high/low gears of our tractor out because the clutch was not fully disengaged and I was trying to shift on the fly. Those were spur gears. Best practice is to wait a few seconds for the gears to come to a full stop. I then rotate the drive train manually if the gears didn't mesh immediately.
 
RJSakowski said:
Any time you engage gears on the fly, you risk the possibility of damage. That holds for both spur gears and helical gears. Automotive transmissions have synchronizers the match tha speed of the gears prior to engagement. I took the high/low gears of our tractor out because the clutch was not fully disengaged and I was trying to shift on the fly. Those were spur gears. Best practice is to wait a few seconds for the gears to come to a full stop. I then rotate the drive train manually if the gears didn't mesh immediately.
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i get that my question is more about shifting while stopped, are the helical gears harder to mesh in say a mini mill H/L selector? the on the fly in my first post was incorrect, i mean are they harder to engage than straight spur gears.
 
dabear3428 said:
i get that my question is more about shifting while stopped, are the helical gears harder to mesh in say a mini mill H/L selector? the on the fly in my first post was incorrect, i mean are they harder to engage than straight spur gears.
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I don't believe that they are. My understanding is that helical gears run quieter that spur gears. Also, initial contact with the next tooth occurs while the gear is still fully engaged with the previous tooth, lessening stress on the tooth.
 
dabear3428 said:
i get that my question is more about shifting while stopped, are the helical gears harder to mesh in say a mini mill H/L selector? the on the fly in my first post was incorrect, i mean are they harder to engage than straight spur gears.
Click to expand...
I think engagement while stopped/no-load will be the same, two parallel/coaxial planes passing each other with (essentially) the same instantaneous spur profile. Maybe a touch of friction as the helical path rotates the mating gears a little, but the comparison looks the same in my mind.
 
dabear3428 said:
i get that my question is more about shifting while stopped, are the helical gears harder to mesh in say a mini mill H/L selector? the on the fly in my first post was incorrect, i mean are they harder to engage than straight spur gears.
Click to expand...

pontiac428 said:
I think engagement while stopped/no-load will be the same, two parallel/coaxial planes passing each other with (essentially) the same instantaneous spur profile. Maybe a touch of friction as the helical path rotates the mating gears a little, but the comparison looks the same in my mind.
Click to expand...
thanks
 
Now that's a good question! Just looking at vector components from the helix angle, I would guess they could be quite high. Good thrust support and oiling are always present wherever I've encountered them, like in manual transmissions and transfer gearboxes. Just look at how much thrust is on a helical ring and pinion, that's nearly all due to the spiral there.
 
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