Broken cam gear

[speedytinc]

Last weekend, 7 model T's headed out for a 4 day camping trip to Death Valley from Orange county. A 700+ mile round trip. We all had a great time dry camping In the open desert. On day 4, cruising @ a comfortable 45mph about 150 miles from home, the engine developed a nasty gear noise. I pulled over & figured the noise was coming from the timing gear mesh. Looking into the oil filler hole while running didnt tell me anything. I have a generator grounding switch/idiot light in the cab. When grounding out the generator, the noise went away. Thought the generator gear got loose. So down the road we continued with the generator grounded off. Made it another 100 miles, then It was like the ignition died.
Tested the coil for spark. Set the crank pin horizontal & noticed the rotor in the middle of 2 plug wires. Thats odd! Pulled #1 spark plug & had a guy hand crank, me checking for compression. Got suck, but no compression. Thats odd! I then did a Mexican compression test. Near no compression resistance. Dead. To the chase trailer.

Next day, "I gots to know!" Did some more looking @ the cam gear thru the oil fill hole. Looked like the generator gear slid forward. More lookin & crank turning, I saw it. An edge of one of the 3 spokes was visible. Broken Iron Cam Gear. Nothing wrong with the generator. The 3 spokes of the cam gear had broken & by continued use, the ends wore enough that it slipped 90 degrees out of time. The gear slid back behind the hub.

This was the first motor I ever built using an original timing gear in 40 years & the last. The gear was in great shape, no wear, on cracks. I replaced it with a Dan McEachen bronze gear. Back up & running.

Any comments? Are original timing gears prone to breaking?

[Kerry]

Never seen or heard of it happening at my end of the world

[Allan]

I'm with Frank, I have never seen a broken original cam gear in more than 55 years of T driving.

Allan from down under

[Wayne Sheldon]

Never seen anything like that either! I have one original iron cam gear that I pulled out of a really worn out motor that the teeth are all worn down to nearly razor sharp! It was so amazing that I have kept it now for nearly fifty years.
I have seen a few strip the teeth due to problems with the generator or a magneto, but never broken spokes unless it was hit hard somehow.
Being on a really tight budget? Good original iron gears is all I have used for years.

[dobro1956]

Ill be #3 to say I have never seen a broken cast iron cam gear in over 40 years of messing with Ts.

[speedytinc]

Wow, didnt expect these responses. I had heard, at some point , Ford changed the design from 4 spokes to 3 for added strength. I, too have not heard of anyone having this kind of failure.

[RajoRacer]

I seem to recall that somewhere I read that the new 4 spoke "helical" gear was stronger than the later 3 spoke - this was 40 + years ago though ! I run Ford steel gears in my T's except the Racer which has Dan's matching gears in it - bronze cam & steel crank. Never have heard of a steel gear failure either !

[Dan McEachern]

Way back when the only aftermarket gears available were fiber, all the go fast guys would only run the 4 spoke cam gears or use the straight cut early gears. Joe Gemsa offered a steel, solid web cam gear for sale on a limited basis, but yes, it was common break the 3 spoke gears. Green Engineering did offer a solid hub steel cam gear along with their other goodies. The helical gears do add a bit of an axial load to the gear set.

[Les Schubert]

I wonder if the problem is related to poor gear mesh fit up? I always CAREFULLY check the gear mesh of both the crank to cam and the cam to generator. Just a thought.

[speedytinc]

I used this cam gear for its minimal wear. Only original gear I have ever found as usable. Gear mesh was correct, a bit more clearence than the book recommends due to a little wear, but not excessively noisy.
I always check the generator gear mesh & shim the mount per spec. Many folks over look this.

[Erik Barrett]

If your internal oil line is clogged it will starve the timing gears for oil. Most external oil lines dump the oil behind the gears so your bearings will survive but the gears will grind themselves up. Ask me how I know this.

[speedytinc]

If your internal oil line is clogged it will starve the timing gears for oil. Most external oil lines dump the oil behind the gears so your bearings will survive but the gears will grind themselves up. Ask me how I know this.

aw shoot, I should have run a speedo cable up the tube when I had access. Didnt think of it.
I am not worried about it being clogged. I run kevlar. 1)There is no band lining to clog the funnel. 2) The last time I checked the transmission screen, after a long time of running, had only a little iron on the magnet. 3)When I first stopped after the noise started, I pulled the filler cap while running, there was plenty of oil flinging off the gears.
Good idea though.