Carbon fiber timing gear

[gward1211]

Has anyone had any experience in having a timing gear CNC machined out of carbon fiber to replace bakelite gear?  From what I have heard, aluminum is too noisy.  This is for a 1928 Buick Master.

[Rusty_OToole]

One thing they used to do was rivet  leather onto the gear as a sound deadener. They would machine a recess in the gear and rivet in a matching ring of leather.

 

Or make the gear out of brass or bronze.

[joe_padavano]

2 hours ago, gward1211 said:

Has anyone had any experience in having a timing gear CNC machined out of carbon fiber to replace bakelite gear?  From what I have heard, aluminum is too noisy.  This is for a 1928 Buick Master.

Machining a gear out of carbon fiber stock is a bad idea. The fibers need to be aligned with the load application axis. That won't be the case for a gear machined out of a laid-up plate.

[Bhigdog]

11 minutes ago, joe_padavano said:

Machining a gear out of carbon fiber stock is a bad idea. The fibers need to be aligned with the load application axis. That won't be the case for a gear machined out of a laid-up plate.

How about laying up the blank by alternating the layers 120 deg to each other?......bob

[edinmass]

Why not run a fiber gear? They were fine for millions of miles. Making something complicated doesn’t make it better. Gears are available off the shelf in 99 percent of applications.

[Frank DuVal]

Or just run aluminum or steel (If the fiber is unavailable), as who can hear the noise anyway! For sure it will not lose points in AACA judging.

 

The material does need to be compatible with the other gear, or wear will be an issue. Carbon fiber might be bad for the other gear.

[joe_padavano]

11 hours ago, Bhigdog said:

How about laying up the blank by alternating the layers 120 deg to each other?......bob

That would help, but frankly I doubt the OP has the facilities to properly lay up prepreg, compress it, and cure it, so I assume he was talking about buying a pre-cured blank. In the aerospace world we have 3D-knitted preforms of graphite fiber that are put into a mold and resin injected for applications similar to this. Needless to say, that requires aerospace-grade budgets. 😉

[gward1211]

Thanks, all, for your comments.  It seems that carbon fiber is not the way to go.  In reply to some points:

I don't have an aerospace budget.

I can't source a new one.  Bob's Automobilia advises that they have had 1928 Buick timing gears on order for 2 years and are not hopefull of ever getting some.

1928 Buick master timing gears 2nd hand are rare in Australia.

I have been told that the noise from an aluminum timing gear is unacceptable.

I'm not sure about brass.  Brass is a sonorous metal.  Has anyone had experience with a custom-made brass gear?

Kind regards

 

Geoff Ward

 

[Grimy]

I can't speak to Buicks, but my 1918 Pierce and 1922 Paige have aluminum timing gears out of necessity (not enough survivors to warrant reproducing), and both are a tad noisy only momentarily on startup until oil reaches them.

[JV Puleo]

1 hour ago, gward1211 said:

...I have been told that the noise from an aluminum timing gear is unacceptable.

I'm not sure about brass.  Brass is a sonorous metal.  Has anyone had experience with a custom-made brass gear?

Kind regards

You probably mean bronze. Brass would be a poor choice.

But, if you are concerned about the noise made by an aluminum gear you might try gear lapping. The mating gears are run (off the car) in an oil bath with rottenstone or some other light abrasive in the oil. This would require making up some sort of stand but it would not have to be a precision machine. This is how RR finished their timing gears. It was a tedious process but gave excellent results. It wasn't done with mass production cars simply because it is so time consuming but for a restoration it might be a good idea. The stand could be made to run off an electric motor and simply left running for days at a time if needed.

 

Another possibility would be a Delrin gear...

Edited December 26, 2022 by JV Puleo (see edit history)

[Terry Harper]

If noise is the issue with metal gears. You could investigate having a new gear milled out of Garolite. It should be a pretty close match to the material used in your original fiber gear. It's available in both paper grade and canvas grade.

 

Edited December 26, 2022 by Terry Harper (see edit history)

[dibarlaw]

The fiber Master Gear is available NEW from Then and Now Automotive. I purchassed one from them for my 1925 Standard. The only variation was that the new gears are solid fiber without the steel hub. I also had to machine a steel washer to get the proper spacing  to match the face of the gears for my Standard application.

 This is what is running in my car now. Not a fun job!

 

Comparison between an earlier aluminum gear and a later fiber one.

 Friend Dave wants me to turn the faces on an earlier 1919 aluminum gear to match the later fiber ones for his 1928 Standard. The 1919 6 cylinder gear has the same O.D. and # of teeth, pitch angle etc. but the rim and hub is thicker.

 

[Larry Schramm]

For my 2cents worth the solution is VERY SIMPLE.  Just buy the gear that the other Larry just above states above is an off the shelf purchase.  No fuss, no mess, no agonizing, etc..

 

A couple of reasons that I would go this route is

 

1. It is the simplest and most efficient route.  Have the part within a week or less probably.

 

2. The most important reason is the original engineers DESIGNED IT TO HAVE A FIBER GEAR.  I believe probably correctly that the reason for the fiber gear is if anything went wrong with the water pump or the starter generator where they would lock up the fiber gear would fail and not damage anything else in the motor.  The fiber gear is like the "fuse" in the mechanical system.  Overload in the system, the gear would fail and not damage the rest of the motor.  Cheap replacement compared to the rest of the system.

 

If a replacement gear was made out of steel, aluminum, etc... I am not sure it would act like the fiber gear in a system failure. 

 

I would never use anything else.

 

Just IMO.

Edited December 27, 2022 by Larry Schramm (see edit history)

[dibarlaw]

I whole heartedly concur with Larry S. As I had showed the failed original timing gear in my 1925 Standard.

 The effect....

 The cause....

 I had machined a new Stainless Steel shaft and Bearings. I had assumed about .003 thousands clearance. I ran the assembled pump on my lathe for 10 minutes. All seemed to be working freely no overheating. VERY INPORTANT! LINE REAM THE BEARINGS WITH HOUSING ASSEMBLED!

 I had to use a puller to get the bearing off the shaft.

Apparently with the installed pump being a bit tweaked by the mounting of the hoses the front bearing overheated, seized on the shaft. I sent the pump up to Reeve Enterprizes in Cazenovia, NY. where they were able to install a lip seal on the output side and a new bushing was done for the front where I used packing since the failure caused a score right where the lip seal would need to be. Not an issue for the last several thousand miles.

In Short... I believe the fiber gear to be a good failsafe component in the system.

 The Other Larry

[dibarlaw]

I believe that I took out the timing gear on my 1925 Master by over tightening the very worn and leaky waterpump packing glands. The watchword for tightening these is HAND TIGHTEN ONLY!

I have made new pump components for it also. Yet to be installed.

Another not so fun job.......

 

 

 

Edited December 27, 2022 by dibarlaw
Added content (see edit history)

[gward1211]

Thanks Larry D and Larry S for the advice.  Unfortunately, Tom at Then & Now Auto advised that he is out of stock of timing gears for 1928 Buick Master engines.  He hopes to have some more made soon.  I have a 2nd hand gear which I am going to run with for the time being.  The old timing gear (which was new-old stock - unused but could have been up to 90 years old) was installed only a 1,000 miles ago and it failed without an obvious cause.  I am told that bakelite-impregnated canvas can dry out and become weaker (or brittle).  See photo.  I was looking at the option of having one made, but it will be too expensive.  I hope Tom comes through soon.  I will buy one as a spare.

Larry D, thanks for the images of the washer needed for the front of the gear.  I assume that that was needed to prevent the fan pulley pulling on too far.  Could you please tell me about the thinner washer.  Is that for the rear of the gear to go between the fiber face of the gear and the camshaft retaining plate?  I notice on mine that the face of the retaining plate shows some wear, indicating that the camshaft tends to be pulled inwards.  On your old timing gear arrangement, was there a washer or spacer between the timing gear steel hub and the camshaft retaining plate?

 

Kind regards

 

Geoff Ward

Sydney

 

 

[Larry Schramm]

Geoff,

 

I would check all of the parts of the water pump and the starter/generator to be sure that they turn freely.  Just a thought.

[Stude Light]

I'm pretty sure fiber gears were designed strictly for noise and not as a fail-safe design. This is the one I'll be using in my 1921 Olds V8. It's only 102 years old so hopefully it'll hold up. Interestingly, it is an all metal gear with trough in the center of the gear section containing the fiber that the crankshaft driven gear rides on.

 

 

[dibarlaw]

Geoff:

 Sorry to say I can not recall where I had the smaller thinner washer. Front or back? All I know is that I needed to shim one side or the other to keep the gear matched with the others.

[gward1211]

Hi all

What I couldn't work out was - the timing gear seemed to fail over time - not a sudden stripping of a couple of teeth.  The gear below looks like it's been pummelled to death.  I also found some lumpy fiber bits in the front and middle sections of the oil pan which could not have happened just in the last few seconds of operation.

 

 

Edited December 28, 2022 by gward1211 (see edit history)

[gward1211]

I think I have found the culprit - corrosion on the driving surface of the crankshaft gear - see photo.  I have been unable to find out the history of this car.  The engine was newly rebuilt but not run before I acquired it.  It has obviously been out in the weather for a long time, given the amount of chassis rust pitting.  It now seems that there must have been water in the engine or else the crankshaft was out of the engine and in water.  It annoys me that I didn't spot this when I installed the new timing gear a year ago.  The old timing gear was worn out but had not been otherwise damaged.  I hope the crankshaft nut and gear can be removed with out too much drama.

Kind regards

 

Geoff Ward

 

[gward1211]

If anyone is interested in a bit more about this car, there is an article in the Pre-War Buicks e-magazine on my Google Drive at the following link:

 

https://drive.google.com/file/d/1s26GKPBS9gSXkp918CcpwiUK32geq5-g/view?usp=share_link

 

Thank you to everyone for their comments and help.

 

Kind regards

 

Geoff

 

[EmTee]

16 hours ago, gward1211 said:

What I couldn't work out was - the timing gear seemed to fail over time - not a sudden stripping of a couple of teeth.  The gear below looks like it's been pummelled to death.

Does the water pump shaft turn freely?  More importantly, does it continue to turn freely under load at operating temperature?  I wouldn't expect the shaft to suddenly lock-up solid and cause the fiber teeth to be ground-off in one area.  Much more likely is the shaft gradually becomes tighter and tighter causing accelerated wear on the fiber teeth as the accessory shaft timing increasingly lags the crankshaft gear as wear increases.  Eventually it gets to the point where the fiber teeth are too thin to take the load, at which point the fiber gear begins to skip against the crankshaft gear at which point complete failure occurs rapidly.  The result is the fiber teeth are badly chewed all of the way around.

 

I agree that the fiber was probably used primarily to attenuate gear noise.  A metal gear could be used if it incorporated a shear key, or pin.

[gward1211]

The water pump spins freely.  It has modern seals (back to back) not a gland nut.  The  puzzle at the moment is - if the corroded teeth on the crank gear cause the failure, I would expect there to be 2 spots of damage on the cam gear.  2/3 of the circumference of the cam gear is undamaged.

Any further suggestions welcome.

Kind regards

 

Geoff Ward

 

[Akstraw]

On 12/28/2022 at 3:56 PM, gward1211 said:

If anyone is interested in a bit more about this car, there is an article in the Pre-War Buicks e-magazine on my Google Drive at the following link:

 

https://drive.google.com/file/d/1s26GKPBS9gSXkp918CcpwiUK32geq5-g/view?usp=share_link

 

Thank you to everyone for their comments and help.

 

Kind regards

 

Geoff

 

Thanks for sharing this link.  You have a beautiful car, though you certainly have had challenges with it.   Great e magazine, too.