MTFCA Forum

Four days ago, driving back from town, with my wife in the car, our 1922 Coupe broke the crankshaft.
My record is not very good. Two Model T's, and now two broken cranks!
At least our 1915 Touring car, is all back together, with a scat crank, Chaffin's .280 cam, EGGE domed pistons, new rods with dipper caps, new timing gears, straightened oil pan, new 4th main and balanced flywheel, balanced triple gears, new drums, etc, etc.

I have a parts car, and I had taken the engine out of it, 6 months ago and it is at the machine shop now, getting the same treatment as the 1915 engine.
After breaking the crank in the 1915, I thought I would get ahead of the disaster curve, and have a new engine built and ready for the 1922 coupe.
But, the crank let go before the replacement engine was ready.. So much for the best laid plans of mice and men.
The crankshaft let go between cylinder number 2 and number three.

OUCH!!!

I think that's where mine broke.
Condolences and welcome to the club. (again)

When I mag those earlier crank shafts 60% goes in the junk pile, the later 26-7 crank have a lot higher percentage rate of being a good crank.

The one I've broke was the same location. Slowing down for a stop sign. Shook like crazy. Turned off the key, pulled over, looked around, found no holes, started it back up. Pulled out my phone, I think I need a ride to the trailer.

This particular location is right in front of the center main. One problem with adjusting the bearings, is when the center main is worn it is usually on the top side under the block because if the transmission sags the weight of the flywheel and transmission will tend to bend the crankshaft down at the rear and up in the center. So the wear on the rear main will be in the cap and the wear on the center will be in the block. When the center cap is tightened to take up the clearance, unfortunately it causes the crank to bend as it rotates and eventually metal fatigue sets in and the crankshaft breaks. So if you get a loose center main, you need to pull the engine and reset the main bearings. If it is not worn too much you might get the timing gears to fit by scraping the front and rear main, but if they won't fit, you will need to pour the main bearings. While doing so, it is good to do all the bearings and if needed, turn the crank or replace the crank. Also you need to straighten the crankcase so the rear of the transmission does not sag. The extra power on the top of the engine might also play a part, but not as much as an overhead conversion would.
I think the SKAT crank is a good idea. I have one in one of my cars and it runs very smoothly and hopefully the crank will be stronger.
The broken crankshaft is not a new problem with the Model T. It happened to my grandfather in 1926 and the T he had was only a couple years old at the time.
Norm