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Old 02-09-2014, 01:53 AM   #1
Mike V. Florida
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Default Bronze or Aluminum timing gear

Any preference/advantage between these two? I already have one of each.
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Old 02-09-2014, 03:21 AM   #2
H. L. Chauvin
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Default Re: Bronze or Aluminum timing gear

FWIW:

One (1) experience & one (1) opinion:

After speaking to Mr. McEachern, & his solving my noisy fiber/steel timing gear problem with a higher lift "new" cam, I would trust whatever he recommends for your particular needs.

I bought his recommended aluminum timing gear which matched my McEachern made crankshaft gear installed by Mr. Ron Kelley & it is "not" noisy ......... even when listening with an Amazon.com mechanic's stethoscope.

I had one fiber timing gear fail years ago on a modern car where the car had to be towed to a shop; however, it appears it would take a head on collision to make the aluminum timing gear fail.

Hope this helps.
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Old 02-09-2014, 08:27 AM   #3
forever4
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Default Re: Bronze or Aluminum timing gear

What about Iron/Steel?

Camshaft Timing Gears on Ford Garage



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Old 02-09-2014, 09:37 AM   #4
tbirdtbird
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Default Re: Bronze or Aluminum timing gear

would that be noisy?

fiber, alum., and bronze are quiet
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Old 02-09-2014, 09:47 AM   #5
John LaVoy
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Default Re: Bronze or Aluminum timing gear

we've had a number of the fiber gears fail over the years. We switched to bronze about 15 years ago and every car we have now has a bronze gear in it. There is no noticeable difference in noise from the bronze gear.
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Old 02-09-2014, 09:56 AM   #6
jhowes
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Default Re: Bronze or Aluminum timing gear

Mikes question has not been answered and I have the same question. What is the experience with bronze vs. aluminum and how many miles should I expect from a fiber gear before it fails.
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Old 02-09-2014, 10:10 AM   #7
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Default Re: Bronze or Aluminum timing gear

Aluminum makes a little bit of noise, but not bad if both gears are meshing well. The bronze won't make as much noise as an aluminum gear, and I have yet to hear of anyone breaking a bronze set. The only down fall of the bronze set up is the $. But if you're building a motor, what's just a little bit more $ at that point. The way I look at it, both are a huge improvement over the fiber gear.
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Old 02-09-2014, 12:25 PM   #8
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Default Re: Bronze or Aluminum timing gear

Either gear will rattle if the clearances are wrong, and either will be quiet if they are right. Its not the fault of the gears which are really precision made. After 80 years of wear and re-babbitting the clearances sometimes may be off. Should be .003, .004 max, measured at 3-4 places around the gear. Dan has oversize gears available. Bronze is probably not worth the extra money unless you are going radical with mods.
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Old 02-09-2014, 12:46 PM   #9
MikeK
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Default Re: Bronze or Aluminum timing gear

I see two parts to answer Mike V.'s question: 1) Noise 2) Longevity

1) Noise
I believe the noise issue is directly related to the pressure wave (vibration) attenuation of the gear material if gear mesh (mis-mesh) issues caused by errant geometry are factored out.

Assuming identical gear mesh geometry, Steel, Cast gray iron, Cast bronze, Cast Al/Si alloy, and Pressure molded phenolic/fabric will all transmit vibration with different levels of attenuation. So who wins?

Back in the 80's I was teaching Foundry practice and metallurgy in a tech school. I had several 10" diameter demonstration bells cast from different metals/alloys that I often used in the lecture hall.

Here's an easy way to look at those materials: Imagine you have those bells made out of those different materials and you are striking them all with the same clapper made from the crank gear material.

Both the steel and bronze bells will ring fairly well, just how well will depend on the specific metallurgy and heat treatment of the material. (Loudest/longest)

The cast Aluminum, if old #12, 319, or 356 will ring but not as well (2nd Loudest/longest)

The cast gray iron (cam gear shown by Vince) will ring but not as loud and for a very short time. One of the great known advantages of cast iron is it's ability to absorb and attenuate vibration. This is why mill and lathe frames are C.I., not steel weldmets. (3rd Loudest/longest) I might add here that Vince's gear with spokes rather than a solid center will further attenuate transmitted vibration.

Pressure molded phenolic with fabric laminations will come in last for performance as a bell. (4th Loudest/longest ring) I never had an actual bell like this, but it surely would go 'thud' when struck.

OK, how would I use this rough, qualitative data? We are looking at sound created from mis-mesh of the gears. If the gear tooth geometry is theoretically perfect, NO vibration is generated and all the materials would be equally silent. As the mis-mesh increases the sound spread between the above materials increases. Conclusion: The gear mis-mesh determines what you hear, and the material determines how much that geometrical gear error vibration will be attenuated.

2a) Longevity (wear)
Assuming a steel crank gear, motor oil, and tooth pressure loading, the phenolic gear should wear fastest. All of the various metals will depend on specific alloy, heat treatment, and surface in their interaction with the crank gear. The cast gray iron will likely be a very long runner, a steel cam gear could grind itself up in 1000 miles if it is the wrong alloy, or go 1,000,000 miles if properly selected. Bronze and Aluminum gears will also be highly dependent on specifically what alloy. I know of one Bronze gear in an RK engine that ground and flaked itself severely in 5000 miles. I have seen an aluminum gear that had silicon crystals so abrasive it severely wore out the crank gear.

2b) Longevity (strength)
What has NOT been addressed here is impact shock delivered to the teeth through the crank as each cylinder fires. The model A has no front damper to attenuate this. A non-counterweighted crank will deliver more firing shock to the cam gear than a weighted one. Basically, it comes down to which material can best withstand a repetitive beating. Here, steel likely wins, as it will distort, molded composition fails, it will crack. The cast iron, bronze, and aluminum gear will depend on alloy and heat treatment to determine the winner.

When you look at the whole problem as posed by Mike V. you have to weigh wives tales, testimonials, and severely lacking materials data. Good Luck. Cogged timing belt, anybody?
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Last edited by MikeK; 02-09-2014 at 05:49 PM. Reason: correct grammatical error
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Old 02-09-2014, 01:07 PM   #10
Purdy Swoft
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Default Re: Bronze or Aluminum timing gear

All of Dan McEacherns gears are silent when used in matched sets. In general, bronze is best and said to be quietest. I've used Bronze and aluminum and they are both quiet for me. I've run loud exhausts on most of my cars and murdersickles for most of my life. I've run power saws and other loud air tools while doing body work as a professiion. My hearing may not be as good as it was when I was a kid. They are just model A's, I love them like they are and am not tring to make a rolls Royce out of them. Bronze and aluminum gears should last a lifetime or more. Fiber gears have never lasted that long for me. The longest that a fiber gear ever lasted for me was seven years and some only lasted a few months. The reason that some fail is because some put a rag between the gears when tightening the cam nut. I know, I know, I've done it myself and it works but is hard, especially on the fiber gears. Dan McEachern recommends the use of a special clamp on the cam gear be used when tightening the cam nut on all of his gears. I think that George Miller showed one of these clamps in use here before.
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Old 02-09-2014, 01:34 PM   #11
H. L. Chauvin
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Default Re: Bronze or Aluminum timing gear

Hi Mike,

FWIW, serious past experiences:

Some may remember that every old non-electric hand crank cash register & every old "till", (money drawer in old stores & bars), had about a 4" x 12" x 3/8" thick piece of marble right above the drawer for a very specific reason.

Counterfeit coins were often made back then; however, with every metal or metal alloy recipe one could imagine, I experienced with old coins that only one (1) had a special sounding loud "ring" like a high pitched musical note determined by the diameter of the coin -- this "ring" was very audible from a long distance.

Furthermore, in the 1700's & 1800's church bells & steamboat bells were cast from different alloys; however, I experienced a few very old bells with only one (1) alloy that produced a "ring" that could be heard from over (10) miles away.

Could go into details on scientific musical notes for different alloys in bells; however, I would imagine if anyone wanted to make a timing gear that had a very unique loud "ring" to it, just make it out of pure silver.

Hope this helps if anyone wants to add timing gear "rings" to a Model A after he wins the lottery -- for now, I'm sticking with quiet, durable long lasting aluminum.
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Old 02-09-2014, 05:18 PM   #12
George Miller
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Default Re: Bronze or Aluminum timing gear

I would take the bronze it will last for ever.
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Old 02-09-2014, 07:01 PM   #13
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Default Re: Bronze or Aluminum timing gear

Bronze would also be my first choice, even though I'm running a one piece fiber gear without trouble. I wouldn't install a 2 piece fiber gear, even if it was free.
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