Whining noise

[Skurge]

Whats that whining noise race cars make, FIA GT cars seem to be the loudest, but formula 1 cars don't make that noise

Here is a video
http://www.youtube.com/watch?v=Y-ukhZeuGyw

 

[LTC8K6]

Straight cut gears? Sounds gearboxy to me.

 

[Skurge]

What are straight cut gears?

 

[LTC8K6]

Pax cars generally have helical cut gears which mesh quietly, except for reverse, which no one cares about. Ever hear a manual car in reverse? You can often hear a gear whine from straight cut reverse gears. Also called Spur gears.

Race cars want the strongest gears, and they don't care about noise, so they usually use straight cut gears.

http://en.wikipedia.org/wiki/Gear#Spur

 

[Skurge]

The article says

Whereas spur gears are used for low speed applications and those situations where noise control is not a problem, the use of helical gears is indicated when the application involves high speeds, large power transmission, or where noise abatement is important.

So wouldn't helical gears be more suited to a race car?

 

[LTC8K6]

While it's true that helical can transmit more power, because the force is spread out more, spur gears usually have stronger individual teeth, and they transmit force more directly. You can think of them as more efficient than helical gears. It's the stronger teeth that racers want, I believe. With helical gears, there are more losses, I believe, and racers don't want that.

One reason spur gears are used in low speed apps is because when you move them fast, they mesh with a whine. Which is what you are hearing in those GT cars...Spur gears meshing fast and noisily.

I believe you can make spur gears quiet by manipulating the mesh angles, but it loses something, making it undesirable for racers.

 

[LTC8K6]

http://www.youtube.com/watch?v=OpZvuMAzfS4

Someone put straight cut gears in their Subaru...

http://www.youtube.com/watch?v=rUs9loF7HaU&

 

[Skurge]

That makes sense. Thanks for the info.

 

[AMCRambler]

I was gonna say supercharger but I think LTC is right. I never heard of straight cut gears. Learn something new every day.

 

[franksta]

I was gonna say supercharger but I think LTC is right. I never heard of straight cut gears. Learn something new every day.

They're a popular mod for aircooled VWs to eliminate some of the thrust load off of the cam when you're running really tough valve springs. Some people just like the sound.
http://www.youtube.com/watch?v=SynhO3LoJsA

Muncie M22 "rock crusher" one of my favorite applications of ye olde straight(er) cut gears.
http://www.youtube.com/watch?v=lWjcgP-MeaI

 

[SpatiallyAware]

While it's true that helical can transmit more power, because the force is spread out more, spur gears usually have stronger individual teeth, and they transmit force more directly. You can think of them as more efficient than helical gears. It's the stronger teeth that racers want, I believe. With helical gears, there are more losses, I believe, and racers don't want that.

One reason spur gears are used in low speed apps is because when you move them fast, they mesh with a whine. Which is what you are hearing in those GT cars...Spur gears meshing fast and noisily.

I believe you can make spur gears quiet by manipulating the mesh angles, but it loses something, making it undesirable for racers.

I was under the impression that helical gears are prone to 'binding out' where some of the force transferred also tries to separate the gears vs spur where the force is transferred directly.





I also am... suspect... of the part of that wiki article that claims helical gears are used in high strength applications. I'm no ME but that goes against everything I've seen IRL.

 

[Bignate603]

I think that a primary cause of failure for racing transmissions is teeth braking due to shifting while on the throttle. AFAIK most racing transmissions do not use a syncromesh design so the teeth may not mesh perfectly as they engage which can easily break weak teeth. A straight cut gear with stronger individual teeth would be less prone to breaking even if the total load transmitting capacity of the gear is somewhat lower.

 

[exdeath]

I think that a primary cause of failure for racing transmissions is teeth braking due to shifting while on the throttle. AFAIK most racing transmissions do not use a syncromesh design so the teeth may not mesh perfectly as they engage which can easily break weak teeth. A straight cut gear with stronger individual teeth would be less prone to breaking even if the total load transmitting capacity of the gear is somewhat lower.

Gears in a transmission are ALWAYS meshed, regardless of being synchronized or not. The gears never move.

 

[LTC8K6]

Personally, I love the sound of them.

http://www.youtube.com/watch?v=hUJvpWwLmHM

This guy puts his gearbox to good use.

http://www.youtube.com/watch?v=dmJH84FnQa8

There's nothing like screaming mechanical mayhem!

 

[Bignate603]

Gears in a transmission are ALWAYS meshed, regardless of being synchronized or not. The gears never move.

You're completely right, sometime in the past I knew that. I swear I'm getting to the point where I'm forgetting stuff faster than I learn stuff.

 

[atiffarooqi]

Actually it has nothing to do with gear strength. In reality helical gears are stronger than straight gears because of the amount of surface area helical gears have relative to straight cut. BUT the helical gears have a lower trust load tolerance, so the case has lower load capacity. In fact, putting straight cut gears into a case that originally has low load capacity will actually increase the case's capacity. What this does for a race car is actually a weight benefit, not a strength benefit, because rather than maintain helical gears and increase the strength (and weight) of the case, you can use a "low load-bearing" case with straight gears and ultimately increase the capacity of the whole tranny.

 

[SpatiallyAware]

Actually it has nothing to do with gear strength. In reality helical gears are stronger than straight gears because of the amount of surface area helical gears have relative to straight cut. BUT the helical gears have a lower trust load tolerance, so the case has lower load capacity. In fact, putting straight cut gears into a case that originally has low load capacity will actually increase the case's capacity. What this does for a race car is actually a weight benefit, not a strength benefit, because rather than maintain helical gears and increase the strength (and weight) of the case, you can use a "low load-bearing" case with straight gears and ultimately increase the capacity of the whole tranny.

:thumbsup::thumbsup:

Thanks for this info, good to know. Welcome to ATG.

 

[JCH13]

Actually it has nothing to do with gear strength. In reality helical gears are stronger than straight gears because of the amount of surface area helical gears have relative to straight cut. BUT the helical gears have a lower trust load tolerance, so the case has lower load capacity. In fact, putting straight cut gears into a case that originally has low load capacity will actually increase the case's capacity. What this does for a race car is actually a weight benefit, not a strength benefit, because rather than maintain helical gears and increase the strength (and weight) of the case, you can use a "low load-bearing" case with straight gears and ultimately increase the capacity of the whole tranny.

Came here to say this. Thrust loading can make helical gears impractical in high-load situations.

I also recall learning that straight cut gears can be made wider, because the transmission doesn't need thrust bearings anymore. This can allow straight-cut gears to be stronger than helical, but I am not 100% on the source of this information.