Mister fiber timing gear, you are the guilty one.

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Model T Ford Forum: Forum 2012: Mister fiber timing gear, you are the guilty one.
Top of pagePrevious messageNext messageBottom of page Link to this message  By Steve Jelf, Parkerfield KS on Monday, April 23, 2012 - 11:21 am:

In the earlier thread about the dead Fordor there was a picture of this still in the car. Now that it's out and easier to see, I thought I'd post a picture just for the entertainment value.


Top of pagePrevious messageNext messageBottom of page Link to this message  By A. Gustaf Bryngelson on Monday, April 23, 2012 - 11:36 am:

I think if you turn it over, you can get a few more mile out of it.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Richard Eagle Ida Fls on Monday, April 23, 2012 - 11:40 am:

Possibly find another, cut them in half and glue together. Looks like more than half is good. :-) :-)
Seriously I've always worried about fiber gears with generators.
Rich


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jerry VanOoteghem on Monday, April 23, 2012 - 12:16 pm:

They'll do that with very little or no warning.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jerry Ostbye on Monday, April 23, 2012 - 12:47 pm:

Reduces cam and lifter wear by not turning.:-)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Steve Jelf, Parkerfield KS on Monday, April 23, 2012 - 01:43 pm:

I wonder if I should put it on ebay.


Top of pagePrevious messageNext messageBottom of page Link to this message  By R.V. Anderson on Monday, April 23, 2012 - 04:05 pm:

That looks like the Cy-lent brand gear. My '23 had one in it until it just wore out.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Michael Deichmann, Blistrup, Denmark on Monday, April 23, 2012 - 04:09 pm:

I'm in that club too:


Top of pagePrevious messageNext messageBottom of page Link to this message  By J Berch on Monday, April 23, 2012 - 04:15 pm:

Things like that always make good nail-hangers in the shop to show your buddies when they stop by to shoot the breeze and solve all the world problems.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Steve Jelf, Parkerfield KS on Monday, April 23, 2012 - 04:24 pm:

Yep, it's going up there.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Royce in Dallas TX on Monday, April 23, 2012 - 04:33 pm:

I got 10,000 miles out of mine before it looked like that. They are crap for sure.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jerry VanOoteghem on Monday, April 23, 2012 - 04:38 pm:

As I've stated in the past, I believe this is a major contributor to broken crankshafts. Notice that in most every case, at least half the gear teeth are gone. That means that the gear turned at least half a revolution before it finally quit all together. In that 1/2 rev. it was most likely grossly out of time, stopping and starting as the teeth climbed over one another, catching & slipping. It's very possible that ignition could have occurred on a compression stroke and bang, no more crankshaft. I've heard several people claim that their crank broke so violently that it stripped the teeth off the fiber timing gear. Wrong, it's the other way around.


Top of pagePrevious messageNext messageBottom of page Link to this message  By David Chantrell - Adelaide, Australia on Monday, April 23, 2012 - 05:42 pm:

I found the fibre partially stripped when I broke a crankshaft in my 1925 years ago. I ripped it out and put genuine gears back in. Although a bit noisier I had no further problems. I much prefer some typical Ford 'T' sounds then the headache of taking an engine in and out and the work required to fix it.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Semprez on Monday, April 23, 2012 - 05:45 pm:

It looks like that gear needs a full set of dentures. I personally appreciate the wonderful documentation you have provided us. One more item to add to the check list for sure!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Steve in Tennessee on Monday, April 23, 2012 - 05:58 pm:

On old T guy recently told me:

"Any T or A engine that is REALLY quiet is a sign of something bad about to happen. They should make some noise, and they all sound a little different."

Perhaps there is some wisdom there. I don't know.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Clayton Paddison, Portland Oregon on Monday, April 23, 2012 - 06:22 pm:

I think that fiber timing gear was one of the worst ideas Ford ever implemented on the T....Nothing wrong with the steel gears.

I have an aluminum gear in my car, but also have a steel spare.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Steve McClelland on Monday, April 23, 2012 - 06:45 pm:

We have a bronze gear in our coupe, I've always heard the fiber gear works best with out use of a generator.
But we never used one for the same reason as the picture Steve Jelf posted.... I don't like the idea of "fiber" anything turning my cam just think of what's in the return oil line !
First thing that comes to mind with "fiber" too me is paper.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ron Patterson-Nicholasville, Kentucky on Monday, April 23, 2012 - 07:43 pm:

Clayton
Did you really mean to infer that a fiber timing gear was Ford's idea and used in Model T production? That's news to me.
Others
There is a bunch of variables in all this.
Improper babbiting and gear lash between the crank and cam gears.
Is a fiber or Nylon for that matter appropriate for the loads involved.
How about improperly made gears?
How many times have you seen poorly made reproduction parts?
The Model T generator always seems to get lashed into the fiber timing gear failure? The normally operating generator consumes about 1/3 horsepower. I would think driving the valve train consumes more?
I believe the "generator" problem is improper gear lash as a result of not using gaskets on the generator side mount or not correctly checking correct gear lash when installing a generator.
When you think about this problem, think in big circles.
Ron the Coilman


Top of pagePrevious messageNext messageBottom of page Link to this message  By Harold Schwendeman - Sumner,WA on Monday, April 23, 2012 - 08:42 pm:

Ron - I can see where the generator might be considered harder on a gear (especially fiber or nylon) due to the added load, however, I would think that it would be more of a STEADY load that would just vary slightly, depending on how much the generator is charging, but I'm thinking that driving the camshaft would be more demanding on a gear than the generator. I think on an 8-cyl engine, the camshaft might might be a pretty steady load on the timing gears, however, a 6-cyl engine, with 4 fewer valves, would be a slightly "pulsating" load at certain critical rpm's, and a 4-cyl engine like the model "T" would surely be more of a "pulsating" load at certain critical rpm's, rather than the more steady load to drive a generator. Not sure if this makes sense or not, but I sure remember back in the '60's that the 4-cyl Pontiac Tempest engine was a failure, because when the engineers took a "shortcut" and just basically cut a V8 engine in half, but they didn't count on the camshaft "pulsations" actually stretching the timing chain to the point where it would eventually stretch enough to slap against the stamped metal timing chain cover which made a terrible "clatter" that I very well remember!

Anyway, I'm thinking that this is one of the "variables" you were talking about Ron,....does this make any sense?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Gene Carrothers Huntington Beach on Monday, April 23, 2012 - 09:06 pm:

OK I didn't see any stick up for old fiber gear. Now it makes me worry cause I had this noise and finally traced it down to the cam gear. I ordered a .005 Over Sized gear from a local vender. Measured it with my old Bronze gear and was surprised to find the OS one was even smaller than the one I was running. I had an old fiber one so I installed it and started the engine to see if the noise had quited. Bingo, no rattling noise so I decided to button it up and run it that way.

Today we ran 130 miles and the car ran great with top MPH at 63 down the 101.

Don't tell me It'll blow up tomorrow. Lucky I don't have anything other than the cam to drive.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Erik Barrett on Tuesday, April 24, 2012 - 12:32 am:

I believe Ron is correct in that there are many factors in play here. I have seen many fiber cam gears and they appear to vary in quality. Many are of old manufacture and may be deteriorating with age. As an engine builder I have seen mains bored off center, causing improper gear mesh. A generator can complicate the problem, especially if not spaced correctly or if the gear runs out of true due to damage to the armature or other trouble.
I too, ripped down Ca. Rte 101 today at 60 MPH and better. OK, so the overdrive is cheating. The point is, I have confidence running a UHMW ("Teflon") gear that I have been using from Reeder's Performance T Parts, now apparently defunct. I like these gears because they seem to have all the benefits of fiber gears, (no noise), and metal gears(reliable). Is anyone else making them available now?
We had a great time on the first day of the
california Dreamin' tour.
Fordially, Erik


Top of pagePrevious messageNext messageBottom of page Link to this message  By Royce in Dallas TX on Tuesday, April 24, 2012 - 06:41 am:

My 15 doesn't have a generator. The fiber gear committed suicide on its own.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jim Eubanks, Powell, TN on Tuesday, April 24, 2012 - 08:34 am:

I would not put a fiber gear in anything, have alum gears in all my cars and yes, have lost one crank with a stripped fiber gear. It AINT worth the risk!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Tom Bergmann Sydney - Australia on Tuesday, April 24, 2012 - 08:43 am:

Erik
The 2012 Snyders Catalog has the Nylon cam gears in 2 versions. Standard and advanced 7.5 degrees.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Steve Jelf, Parkerfield KS on Tuesday, April 24, 2012 - 09:11 am:

I'm sure a lot of people will protest that they've never had a problem, but since spending a week at a motel in Trinidad CO waiting for replacement of bent valves and other repairs to a dead Suburban, I'm not a big fan of nylon timing gears either.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Clayton Paddison, Portland Oregon on Tuesday, April 24, 2012 - 11:07 am:

Ron,

I thought that was the story? Were the fiber timing gears NOT a Ford experiment that just didn't work?

I would swear that the one I pulled out of my motor was stamped "Ford"...


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jerry VanOoteghem on Tuesday, April 24, 2012 - 12:17 pm:

Clayton,

Was it stamped with the Ford script logo, or was it marked in simple block letters, as an aftermarket source might do to identify what car it's for.

I don't believe Ford ever supplied fiber gears in the Model T days. Maybe if you got a replacement gear from a Ford dealer in 1940, (for example), perhaps it might have been fiber?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jerry VanOoteghem on Tuesday, April 24, 2012 - 12:26 pm:

Ron,

You're correct in that any part, used or installed incorrectly can fail. However, there can't be that many poorly installed fiber gears out there to explain their poor performance, can there? I can tell you that the three I shredded were not binding when first installed.

As to blaming the generator, I don't believe anybody is really doing that. As you advised, I believe folks are "thinking in big circles" by suggesting that it's the cumulative load of valve train & generator that may overtax the gear.

All this being said, I still have a fiber gear in my Touring car. It's been in there for forty years. I inspect it closely every year. Trusting soul, ain't I?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ron Patterson-Nicholasville, Kentucky on Wednesday, April 25, 2012 - 12:24 pm:

Jerry
Today I learned something from someone who knows what he is talking about. Several years ago a well known company was making quality (Using an appropriate manufacturing process) fiber timing gears. They no longer make these.
Another manufacturer started making (using a cheaper process) the poor quality units that are available today.
Ron the Coilman


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jerry VanOoteghem on Wednesday, April 25, 2012 - 12:52 pm:

Ron,

Very true. The older ones had the teeth essentially molded in while the new ones appear to have cut teeth. The difference being, the cut variety cuts through the molded-in fibers that give the tooth its strength. Is this what your "source" indicated? Just curious.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ron Patterson-Nicholasville, Kentucky on Wednesday, April 25, 2012 - 01:50 pm:

Jerry
I was told the earlier gears were laminated and press formed out of a fibrous materiel (similar to fiberglass) in a mold.
The later cheaper versions were rough cast out of a granular material (no fibers) and then had the teeth machined.
The cheaper gears put the more expensive gears at a significant disadvantage the they stopped making them.
In my opinion one would have to be out of their mind to use fiber gears available today.
Ron the Coilman


Top of pagePrevious messageNext messageBottom of page Link to this message  By Steve Jelf, Parkerfield KS on Wednesday, April 25, 2012 - 01:55 pm:

It tells us something that some of the major parts dealers don't carry the fiber gears. The old iron gear is going in my car. But that will be noisy! So? It's a Model T. I probably won't notice that noise over all the other noise.


Top of pagePrevious messageNext messageBottom of page Link to this message  By john kuehn on Wednesday, April 25, 2012 - 02:22 pm:

I wonder sometimes why there is no one making the original iron type timing gears. They will tend to be a bit noisy but its not all that bad.
Maybe the brass or aluminum gears dont cost as much to reproduce.

Hmmm.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Royce in Dallas TX on Wednesday, April 25, 2012 - 09:44 pm:

The iron gears are completely silent after they are broken in. Just like the aluminum and brass gears.


Top of pagePrevious messageNext messageBottom of page Link to this message  By mike_black on Wednesday, April 25, 2012 - 11:09 pm:

I put a fiber timing gear in my TT in 1978. In 2004 my gen slung the windings and stopped the gear resulting in the fiber gear being eaten. I only had to replace a cutout, an armature and a timing gear. What would have broken if the timing gear had been steel?


Top of pagePrevious messageNext messageBottom of page Link to this message  By George_Cherry Hill NJ on Wednesday, April 25, 2012 - 11:19 pm:

This issue with cam gears is real simple to figure out in plain language...

The car was designed with an iron gear...at a given tooth form...for a given load...at a given face width...at a given 'degree' system. Y'all got that, that part is really easy :-)

If you DO NOT change the gear pitch or the face width or change a spur to a helix then changing materials comes with considerations and complications! Going from cast iron to fiber resin good engineers will say the gear can only transmit 50% of the load of the previous sized iron gear, for nylatron and delrin gears the same deduct applies, aluminum has a similar 'deduct' but can be played with depending on 'heat treatment' and bronze for all intents and purposes is interchangable with cast iron in gearing. This is the part that most people 'miss'. Hey, if a pinion has a 250% safety factor then a 50% reduction in the gear is not a big concern but how many of you think Ford had 250% safety factor on the crank gear? Yeah...right...'nuf said.

Now Ron is right, there have been many types of fiber gears thru the years and they are a plywood of sorts...some type paper layer and resin sandwich...sometimes cotton burlap and resin sandwiches...sometime linen and resin sandwiches...and sometimes canvas duck and resin sandwiches. Today you can get fibre resin gears in carbon fibre...but I have yet to see a mass migration away from traditional other materials. Start to see the bigger picture now? The paper type is the cheapest raw material and also the lowest grade possible. Wonder what these T gears are.

Steve...you have everything else in the universe that can be had that you are lucky to always find for pocket change! Got a big disc sander? Take a slice and polish it on the sander...see what the 'fiber' really is. :-)

Fiber resin gears have another benefit/problem. They are quiet only because they actually do 'mush' under load and impact rather then 'rap'...but they can only take a few billion cycles of this before they want to wheez...then again, some of the resins used tend to want to go soft at 160F, others at 250F. That 160F grade just might scare me, I don't know.

The Delrin and Nylatron work the same way but their fatigue life is somewhere about ten fold the resin fibers but the life and conformance will never be agreed to by the raw material maker for over 200F operation...then again, these plastic gears will throw teeth if installed to standard backlash. They do work fine provided...that you ADD additional backlash clearance over what the iron design called for...usually about 1 thou per inch of diameter is considered 'safe' enough. Aluminum has the same problem, it grows with heat pretty fast but not as fast as the delrins/nylatron....but aluminum laps away quicker than other materials so it will 'walk' in most of the time.

Finally...to Royce WOW! Sometimes we don't agree on a few minor things...but...that is about the best thing you have ever said using the least amount of words possible! Kudo's and a tip of the hat!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Royce in Dallas TX on Thursday, April 26, 2012 - 07:49 am:

I still prefer the original iron timing gears. If they are in good shape put them back in. The other gears are a downgrade in reliability, like many so - called "improvements".


Top of pagePrevious messageNext messageBottom of page Link to this message  By Wayne Sheldon, Grass Valley, CA on Friday, April 27, 2012 - 04:01 am:

First, I have really enjoyed all the postings and explanations about fiber timing gears. I was going to say "especially (?)", but there were too many really good explanations to choose a couple over the others.
Second, nobody changed my mind on anything. I have been firmly in the "I don't care for fiber timing gears" camp since I was about ten. My father had put a 'new' rebuilt 216 engine into his 1951 Chevrolet pickup. My mother had just gotten her driver's license. The engine had about 18,000 miles on it and my dad was almost 200 miles from home when it let loose. My poor mother had to go rent tow-bar equipment (how many people remember those?), bundle up my toddler sister, younger brother, and myself, to drive the first long drive in her life to go where my dad sat on the side of the road. I remember it being one of the longest days in my life. I watched for a couple days while my dad pulled the engine back out and repaired the damage. I clearly remember how that gear looked still in the stripped engine. And the 216 was designed to run a fiber gear.
I am totally with Royce on this one. I usually use good used steel gears. Model Ts are supposed to rattle. I am, however, very grateful that good replacement gears are available. Otherwise good originals would be very difficult to find.
Thank you to all.
Drive carefully, and enjoy, W2


Top of pagePrevious messageNext messageBottom of page Link to this message  By David Stroud on Friday, April 27, 2012 - 05:52 am:

The first experience I had with fiber timing gears was on a '56 Chevy six cylinder that our preacher had in the early sixties. It let loose and my Dad and some other church members repaired it. I was about twelve years old and didn't know much about cars, but even back then, I thought that was a very poor setup. I still think so. Dave


Top of pagePrevious messageNext messageBottom of page Link to this message  By Hal Davis-SE Georgia on Friday, April 27, 2012 - 06:49 am:

My cynicism is showing, but here is how I see it. Someone comes up with a cheap way of doing something and puts a marketing spin on it to move your attention from the shortcomings of the inferior product to some perceived advantage. I remember picking up a shirt in a store that was so thin you could read the paper through it. They were marketing it as "quick drying". Perhaps the fiber gears fall into the same category. The real reason they are fiber is because it is cheaper to make. The "quieter" feature is the marketing ploy. Just a theory...


Top of pagePrevious messageNext messageBottom of page Link to this message  By Steve Jelf, Parkerfield KS on Friday, April 27, 2012 - 08:46 am:

Hal, if you're cynical on this, so am I.


Top of pagePrevious messageNext messageBottom of page Link to this message  By George_Cherry Hill NJ on Friday, April 27, 2012 - 10:21 am:

Hal,

It's not cynicism...you are right, a lot of stuff is P.T. Barnum....and at the end of the day there are maybe 5% who luck by....don't really know why...they just do.

I'll share the way I look at some of this 'stuff'...where a technology existed in the era, and Ford chose not to use it...buyer beware! Beat me up if folks must, but even things like ball bearing 4ths change the 'dynamic' of what is going on with where that load wants to go and it does go somewhere...

For some of this other stuff...such as how to actually make a coil box impervious to humidity and tracking or a good way to add adjustment to shaft pinions without opening and shimming 20 times? The technology or 'thought' didn't exist in the era, and while someone was creative in a modern 'solution' they took the time to think it through before they said "why not...zero downside!"


Top of pagePrevious messageNext messageBottom of page Link to this message  By Brian Sullivan, Powell WY on Monday, October 22, 2012 - 10:45 am:

Is this the type of gear that I am to be concerned about?; if yes will toss it and replace, but wanted to confirm first.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Semprez-Templeton, CA on Monday, October 22, 2012 - 11:10 am:

Bad, bad Mr.timing gear!If a magnet doesn't stick to it, off to the recycle bin for me!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Norman T. Kling on Monday, October 22, 2012 - 11:33 am:

I have not yet had a crankshaft break! Therefore, crankshafts don't break! We know the above statements are not true, because probably everyone on the forum has known someone who did have a crankshaft break, or have heard about one breaking.

Therefore, because someone has run a fiber gear and not had it break, does not mean it can't happen. The opening post is proof positive that it can and does happen.

By looking at that picture, I would conclude the engine was going quite fast to take off that many teeth before stopping. It only takes just a few teeth to throw the timing off enough to stop the engine.

Here are some things I think could have contributed to the problem. You will notice that only the front part of the teeth were shredded. That would indicate a misalignment between the crankshaft gear and the camshaft gear. I don't know whether that car had a generator, but I have seen generator gears where the teeth were worn leaving a sharp edge at one end of the gear teeth, indicating that the generator was or had been at sometime out of alignment with the camshaft. If that same generator gear were installed with a new fiber camshaft gear, the sharp edge would very quickly cut into the fiber teeth.

I don't know for sure whether either of these factors caused the demise of that gear, but would rather live with some noise, than have a quiet car which could stop instantly (They can still stop instantly from other causes, but here is one that can be eliminated).
Norm


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jerry VanOoteghem on Monday, October 22, 2012 - 12:25 pm:

Norman,

Every shredded fiber gear I've ever seen, including the ones I've shredded, have had about half the teeth missing. Not all done at high speed either.

The fiber teeth don't get cut or wear in the normal sense, they just simply break off with almost zero warning.

Brian,

Yes, that's one of the bad guys. If it were mine I would throw it away.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Brian Sullivan, Powell WY on Monday, October 22, 2012 - 12:28 pm:

Tossed. Thank you.


Top of pagePrevious messageNext messageBottom of page Link to this message  By William L Vanderburg on Monday, October 22, 2012 - 12:53 pm:

Quote: "Someone comes up with a cheap way of doing something and puts a marketing spin on it to move your attention from the shortcomings of the inferior product to some perceived advantage."

Isn't this exactly what part shysters were doing back in the day and today as well?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Wayne Sheldon, Grass Valley, CA on Monday, October 22, 2012 - 05:00 pm:

I am glad you tossed it. My tale is a ways back.
Drive carefully, and enjoy, W2


Top of pagePrevious messageNext messageBottom of page Link to this message  By Roar Sand on Monday, October 22, 2012 - 07:16 pm:

Scary stories here!
I bought a spare crank and cam gear from the Sears Catalog somewhere around 1965, and it seems like the smart thing to do now is to throw the fiber cam gear away.
Much good info here!
Roar


Top of pagePrevious messageNext messageBottom of page Link to this message  By Norman T. Kling on Monday, October 22, 2012 - 07:44 pm:

I don't know when they came out with the fiber gear, but most of the Model A's I have owned in the past had fiber cam gears. So maybe someone thought what was good for a Model A was also good for a Model T? By the way, I have also had the fiber timing gears on Model A's go bad. Plymouths had a timing chain and sometimes the chain stretched to the point it would fall off the sprocket. And other cars had a timing belt. The belts had to be replaced from time to time, so i guess that part was always a problem.
Norm


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mike Vaughn on Monday, October 22, 2012 - 07:49 pm:

My case is with a nylon gear, the alternator seized after I had parked the car after a full day of driving. A couple of hours later I went out to try and start the car and because the alternator was seized the starter had enough power to shell the teeth on the timing gear. It shelled the teeth on the gear until the crank gear came into contact with the shelled out area. Notice only half of the teeth are missing so essentially the crank rotated one complete revolution before it ran out of teeth and was just rubbing on the timing gear. I don't believe that a metal gear would have allowed the starter to turn at all so you would have heard the bendix engage but the motor would have been unable to turn the engine over. The nylon gear may have saved the starter from damage, who knows. I did replace the gear with an aluminum gear because I already had one on the shelf as a spare. Looking at Steve's gear the damage looks very similar only half of the teeth are shelled. I would suspect the generator may have been hard to turn and the starter motor turned the crank one revolution before it was out of teeth. Just my thoughts.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Max L. Christenson on Monday, October 22, 2012 - 07:51 pm:

Has anyone tried using the adjustable timing gear, adjustable in two degree increments, made by Specialty Motor Cams? If so, how does it perform?

I am rebuilding a 1922 Model T engine. It came to me with a fiber timing gear in it. The word "Ford" (in script) is etched into the gear. This Ford script fiber timing gear appears to be in good shape, but I wonder whether I should replace it. I suspect that I should replace it, but with what? Aluminum or bronze, or the adjustable timing gear?

How can you tell if a used original iron timing gear is still usable? Isn't the fact the original iron timing gear is used (not NOS) an indication that it is now un-usable?


Top of pagePrevious messageNext messageBottom of page Link to this message  By george house on Monday, October 22, 2012 - 07:56 pm:

Steve Jelf,
You won't need to italicize your worry that iron timing gears will be noisy. I put the original spur cam/crank gears back into my '14 runabout. Its real quiet and runs like a scalded ape. Like the ring and pinion, its nice to use a decent matched pair but if thats not possible - go ahead and use the Ford timing gears


Top of pagePrevious messageNext messageBottom of page Link to this message  By Danial - Veneta OR US Earth Solar System on Monday, October 22, 2012 - 10:11 pm:

I have a pair of those fiber timing gears, brand new. Should I sell them as dog-chew toys?


Top of pagePrevious messageNext messageBottom of page Link to this message  By roy palmer on Monday, October 22, 2012 - 10:18 pm:

Isn't there a better timing gear that is fiber? A fiber gear that has some kind of strings running through them.

I have heard those gears do not have problems. Is that true?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Steve Jelf, Parkerfield KS on Monday, October 22, 2012 - 10:35 pm:

Max, the answer is no. The fact that an iron gear has been used doesn't mean it's no good. I have an excellent iron gear that was in a pile of miscellaneous parts I bought at an auction for $11. Most of us use Hyatt axle bearings that are ninety years old but still good. There are good used parts around. It takes some digging, but you can find them.


Top of pagePrevious messageNext messageBottom of page Link to this message  By George_Cherry Hill NJ on Tuesday, October 23, 2012 - 12:38 am:

Ah back on this one again, eh?

It’s real simple…Plastic and Laminated Phenolic may have a history of working in the application yet when we look at a failure such as this we see that the teeth obviously sheared in bending.

Forget wear factors, forget noise, forget backlash, forget all the other things that go into finding a good gear set-up and let’s just look at bending by its’ self. At what point in bending does it just go nuts, all other things being the same as to dimensions, loads, and the like?

Rather than take my usual Don Quixote approach, this morning I had the pleasure of hosting ‘morning with the boss’ with the new Masters interns in Mechanical Engineering. I don’t have drawings and sizes with me but could guess at good enough for PD and took ‘I’ as width as it really doesn’t matter in relativity terms and looked at 1600 RPM on the pinion. Then had the boys do everything else in relative terms.

Here are the results (which I did double check before posting and did so the old fashioned long hand way like old f*rts still do). When it comes to ‘bending’, bending strength relativity or better said resistance to bending is on a standardized ‘safe stress’ basis:

Cast Iron in the 160-200 BHN range……………………………………………………..….... = 100

Using plain old M-1020 plate material without special treatment………….....…. = 167

Using a standard basis (5000 psi) middle of the road laminated phenolic…......= 42

Using a Delrin type material……………………………………………………………………… = 42

Sorry, did not do aluminum because I don’t know the alloy number and a minor change gives huge result changes.

As they say “There you go!” the answer is in the numbers! Why anyone would want other than an original jumps right out on you.

Now the conundrum…a Delrin gear should behave no different than the Phenolic Resin Laminate if we only look at ‘safe bending stress’, so why do the Delrin apparently survive? My view and it would take another work session is that it says that the working surface pickles differently in use and that something else causes the Phenolic Laminate to go ‘poof’. It may be loss of backlash due to swelling or may be something else. My gut says the fibers open up and swell in time, backlash tries to go minus and then it just adds a whole new factor to fatigue. I’d also like to know the exact compound number and suffix on the ‘plastic’ gears as I know that a very minor change in suffice has a huge effect on cycle fatigue life, but that’s and other topic for another thread since the focus on today is looking at bending stress.

I personally have not designed too much in Phenolic Laminate being of an age where Delrin and like ‘plastics’ were the latest and greatest but I do now recall that on some high speed machinery that I inherited design responsibility on as a pup part of the precision printing register used a laminated phenolic gear. And…the ‘fitters’ use to actually burn the gear tooth surface totally black before submerging in the oil sump! Guess I should have asked why, eh? Don’t know but maybe the white haired guys of the time knew something about Laminated Phenolic in a hot oil sump?

In any event, the answer is clear…why even use a Laminated Phenolic? They may last for a long, long time, but surely do grenade when they let go, eh? Ford was apparently not concerned about using Cast Iron and its higher resistance to bending.


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