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Author Topic: Special-cut gears  (Read 14549 times)

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GTRS Fiero

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Special-cut gears
« on: November 27, 2019, 08:41:04 pm »
I remember something about the gears in the Fiero transmission having a special cut.  What difference does it make?
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Fierofool

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Re: Special-cut gears
« Reply #1 on: November 27, 2019, 10:10:42 pm »
From the machine shop, if I remember correctly, there are straight cut gears like Melling Gears.  I think they were spur gears.  There is a gear with an angular cut like the gears inside our headlight motors and there are screw or worm gears also like inside our headlight motors.  There are beveled gears like the spider gears that run in a ring and pinion setup.  There is a strange looking gear that I don't remember the name of, but the teeth of the gear were cut into a V. 

I've never seen the inside of a Fiero transmission, but I would guess that they are all spur gears with the edges of the teeth tapered so that they can engage one another while in motion. 
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GTRS Fiero

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Re: Special-cut gears
« Reply #2 on: November 27, 2019, 10:35:29 pm »
Maybe it was just in first gear.
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TopNotch

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Re: Special-cut gears
« Reply #3 on: November 27, 2019, 10:49:43 pm »
All street use transmissions have the gears cut at an angle. This is called helical gears. Racing transmissions sometimes have straight cut gears. Here is an article that explains why.
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scottb

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Re: Special-cut gears
« Reply #4 on: November 28, 2019, 06:09:18 am »
Gear teeth in a V shape are herringbone gears
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GTRS Fiero

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Re: Special-cut gears
« Reply #5 on: November 28, 2019, 06:15:53 am »
So, my RC car uses straight-cut gears, which makes it noisy.

I had an '85 Escort that really whined, when downshifted to first.  Does the Fiero do that?
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scottb

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Re: Special-cut gears
« Reply #6 on: November 28, 2019, 08:33:08 am »
herringbone gears
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GTRS Fiero

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Re: Special-cut gears
« Reply #7 on: November 28, 2019, 08:37:16 am »
Maybe if they were larger, I could see them!   ;)

Holy cow!  Those things would steamroll my Fiero!
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scottb

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Re: Special-cut gears
« Reply #8 on: November 28, 2019, 08:43:47 am »
reduction gears for a ship
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Fierofool

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Re: Special-cut gears
« Reply #9 on: November 28, 2019, 08:50:00 am »
Those gears are different than what I saw at the shop.  There was no space between where the angle of the teeth changed.  I don't think they were capable of being engaged and disengaged.  They were probably intended to be installed on 2 parallel shafts, which would effectively change the direction of rotation from input to output shafts.  The only I can see that they could be engaged and disengaged is that if the shafts moved away from one another.  Shafts in gearboxes generally don't do that because they need to be firmly located due to the stresses placed upon them.  It's gears that generally move in a gearbox, not shafts. 

When my partner and I first got together, he worked for Arbiser Machine, making gears.   

And yes, both my Fieros gearboxes whine.  In all gears. 
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TopNotch

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Re: Special-cut gears
« Reply #10 on: November 28, 2019, 11:12:29 pm »
If a transmission with helical gears whines, it could mean it's worn. The old transmission in my duke was whining pretty bad when I replaced it. The "new" one doesn't.
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GTRS Fiero

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Re: Special-cut gears
« Reply #11 on: November 29, 2019, 07:52:30 am »
Quote from: scottb on November 28, 2019, 08:43:47 am
reduction gears for a ship

Ah, yes.  In that case, they would send my Fiero to Davey Jones' locker.
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GTRS Fiero

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Re: Special-cut gears
« Reply #12 on: November 29, 2019, 07:53:35 am »
Quote from: TopNotch on November 28, 2019, 11:12:29 pm
If a transmission with helical gears whines, it could mean it's worn. The old transmission in my duke was whining pretty bad when I replaced it. The "new" one doesn't.

Interesting.  How can one tell the difference between "normal" whine, and "worn" whine?
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TopNotch

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Re: Special-cut gears
« Reply #13 on: November 29, 2019, 10:48:57 am »
If the whine is louder than the engine, that's a good clue.
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GTRS Fiero

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Re: Special-cut gears
« Reply #14 on: November 29, 2019, 06:24:20 pm »
You'd figure it would grind, when worn.
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