After 7000 miles of fun I finally did it.
So annoying I was actually looking at it not an hour before admiring my car, in a lineup of fantastic classic cars.
I was taking it easy because I was planing to drive it to Ireland in 11 days. We were going up a slight hill about half throttle no problems, and BANG! My heart sank, after reading on here I knew straight away it was the crankshaft.
It's a diamond dodge crank, and I have alloy pistons.
Photos to follow tomorrow.
I am going to fork the bucks over for a new Scat crank in my rebuild. Its not worth it using a used crank on an early block.
If you are lucky the break didn't damage the block. Be sure to check all the webbing around each of the main bearings with magnaflux before you put a new crank in. If they are cracked, sometimes they can be welded and the block can be salvaged. Don't blame yourself. The car is almost 100 years old and this might have been the original crankshaft. It could have happened to anyone.
Years ago I did the metalurgy on a bunch of cranks for the T's the DB was the crappiest of them all for crank. Of all the crank's I have magnufluxed I have never found a DB not cracked?
What was the best original crank you found?
Jeremy, the best I had found was 25-27 crank that was stamped EE on the throws, now there is four other styles of 25-7 cranks with different stampings also they are U,C,AA,F and The DE from canada. A few years back some one else had followed up on this and that is where the new Dubatt's cranks came from, he had made them from the same material as the EE's. I have never heard of any his cranks failing but when the ScaT came out how do you compete against a big company like that? I would sure like to get my hands on one of his cranks. I just installed one recently and they fit and look very nice. I think the Scat is an over kill for weight but if you using the A conversion in a T then you need that weight. Just my thoughts, Thanks
Good-day Jeremy: Welcome to the club that I joined in 2004.I thought some members may benefit from my expériences as outlined below.The first photo is of the broken “ Sure-mike” counterbalanced crank from the early years. In 1998, in apparently good condition, it had been provided with the engine for our ’12 Touring. During the engine rebuild, this crank had been chromed up to standard. However I suspect that whoever did the job, neglected to magnaflux the crank before proceeding with the work. All looked to be in excellent condition when I assembled the engine initially. I drove the car successfully for a couple of years before the crank failed during my trip to Toronto in 2004.
Close inspection of the break in the centre main revealed that in fact “ the shaft was cracked for quite some time- make that several years- notice the dull rust coloured portion, versus the small shiny portion that was newly fractured. As a replacement, I have indeed installed the modern counter-balanced crank also shown in the photos. We have over 22,000 miles on the engine since this upgrade with no further troubles.
Why should the crankshaft have broken in the center main?
My suspicion was that this used crankshaft had been in an engine in an early T, (not a ’26 or ’27) ; one that provided no means of fixing the hogshead to the block- thus holding the crankshaft and transmission in a fixed straight line, but that the pan was free to flex up and down at the back end. This flexing throws a great deal of extra stress into this center main bearing. To address the problem, I came up with a novel solution described below:
First I assured myself that my early ’12 pan was indeed “straight and true”!
Then the engine was assembled in the vertical, with the pan and hogshead bolted securely in place. With a hardwood pry-bar between the hogshead and the upper rear of the block, I pried and/or squeezed until I had the output shaft of the transmission, true on the center to allow the FOURTH MAIN –ball cap to slide freely into place. This is the straight line we want to retain. To do so I then bent up a ¼” thick cold–rolled steel plate, which I fixed with the four rear-most head bolts, 1/4” longer, onto the head. The bend, that must be very precise, brings the lower end of this plate, down to the two upper bolt locations of the bolts that retain the transmission inspection cover. With the cover removed, and my ¼” plate intimately against the surface of the hogshead, I carefully entered a sharply pointed 5/16” NCT tap from the inner face of these two holes to clearly/accurately mark the centers on the underside of the plate. The plate was then removed and close tolerance holes drilled for two new Grade 8 Allen head cap screws. The upper surface of the plate is counter bored at the appropriate angle such that the cap screws are flush on the upper side. We can then reinstall the plate – with the four rear head bolts on the upper end, and insert and tighten the cap screws through the lower end into the hogshead. All that is left to do, is to modify the inspection cover with a step on the upper edge, to accommodate this additional ¼”plate. (See the sketches.)
In 11 years of driving this upgrade has done an excellent job. (As this modification allows us to retain the original early block in our brass T’s- with the added security as in Henry’s ‘26/’27 upgrade, in recent years, a couple of other local club members have also followed my efforts.)
It is unfortunate that it took Henry Ford until 1926 to rectify the problem by installing the two ears on the hogshead and modifying the block with two bosses to accept the 7/16” bolts that fix the hogshead securely to the rear surface.
Tom, that's a remarkably good idea and not that hard to fabricate. Are you using the magneto post?
Hi George: In actual fact I have been running a True-Fire ignition system for these many years.
However the support plate leaves adequate clearance of the magneto post to properly connect the lead.
I rebuilt the magneto coils and recharged the magnets during my initial rebuild.(Although I don't use the magneto with the True-Fire -that operates on DC voltages only,and not the AC produced from the magneto, it still today produces an excellent output. I gave up years ago trying to have equal performance from four Model T coils. Perhaps one day I'll try again.
Warmest regards,Tom Forsythe
(Indeed this is an easy upgrade to our early blocks - most fellows could handle it!)
Jeremy, since your crank broke in front of the center main, you've still got the center and rear main. Why not take a spare block and build a "Johnny Popper" type two cylinder out of it and have some fun?
Excuse my lack of knowledge but can someone please explain exactly where the number stamp is located on the crank?
Kevin - These are mostly letters on the crankshaft. The DB is for Dodge Brothers, a "T" over a "W" is for Transue Williams, and a "C" over an "H" is for Cleveland Hardware & they are the manufacturers of those crankshafts. There are others also, including Ford script.
The EE, U, C, AA, F and DE refer to the metalurgy and hardness of the crankshaft for the '26 & '27's. The EE was the last one used and is considered the best original crankshaft made.
These letters will be found on the side of the throws between the rod journals, but Some "EE" crankshafts have the EE stamped on the very front end also.
Beyond this there are two general styles of T Crankshafts. From '09 to '24, they have diamond shaped throws between the rod journals. From '24 through the end of production, the throws have straight sides and are much "beefier".
I've broken two crankshafts and both of them were the diamond shaped type. One was made by Cleveland Hardware and the other by Transue Williams. I would never again use a diamond shaped crankshaft. Further, If I bought a car with one in it, I would remove it and put a Scat Crank in.
I have a 27 and research tells me the motor was last rebuilt in the 60's so who knows, I haven't had the pan off yet. Can you post a pic of a number on a crank so I can see exactly where to look please?
I haven't mastered the art of posting pictures on the Forum yet....perhaps someone else can post a picture of this.
I have never noticed a difference of crack rate in a 26-*27 motor.
They all will break, at one time or another.
We go through a lot of 26-27 cranks the same as the others that are cracked, to find a useable one.
I'm posting these for Keith G.. The comments are by Keith:
The first two pictures are comparing the early / diamond shaped throw crankshafts to the later, straight sided crankshafts.
The next one shows the "C" over "H" = Cleveland Hardware manufacturers logo. The next one shows T498 & I think this is the factory number. The "AAXO" is the metallurgy & hardness code. These three are all on the same broken crankshaft.
The next one has a "T" stamped over a "W" and is the logo for Transue Williams. This is also one of my broken crankshafts.
The next two pictures are from an unbroken straight sided crankshaft. The "F" inside a triangle means it was made by Ford, and except for the Ford script on it, it has no other markings.
The last picture is of the two crankshafts I've broken.
A big Thank You to Rob for posting these pictures for me. One of these days UI've got to take the time to learn how to do it.
Learn how to do what, post photos, or break crankshafts??
I think Keith has breaking crankshafts mastered.
Sorry Keith, I couldn't resist.
Amen to that!
There are many members of the two piece crankshaft club among us. What about guys like Dean Yoder & the Montana 500 guys...do any of them ever break crankshafts?
Maybe it's time for a new thread on how to "bulletproof" Model T engines so they don't break crankshafts, including pan straightening, balancing, 4th main, trans. main shaft, the best crankshaft to use, etc., etc.
Anyone want to try it?
It's inevitable - they'll eventually break as long as the main and rod bearing diameters are as thin as the original 1.248". You may lengthen the life by making everything straight and unbendable with the improved attachment between the hogshead and the block, but there are still twisting in the crank from each power pulse on each revolution - and a long thin crank like in a T with four large pistons totaling 176 cui twists so much it'll eventually get fatigued and crack.
And if it's run at certain speeds, the twisting impulses will interact and resonate increasing the amplitude even more, sometimes called "thum" speed - something to avoid for best crank life.
Even though all T cranks are doomed in the long run, some of them lasts longer than others - there will be serviceable T cranks after we all are gone, just harder to find good ones. 26/27 EE marked cranks has a good track record. And if you have the means and wants to go fast without breaking cranks, then there are SCAT cranks available with larger bearing diameters.
Roger - That's a good summary on the life and problems of Model T Crankshafts.
You mention SCAT Crankshafts with larger bearing diameters, but how do you feel about SCAT crankshafts with the stock 1.248" diameter?
Can they be reasonably "bulletproof, as when used for typical Model T touring, not racing?
Just looking for more opinions on this.....
Same question as Keith, with an extra ??. Is the SCAT crankshaft near "bulletproof" at 1.25 diameter or do we need to go to the 1.50 size with new rods, etc to achieve this? Next question, does the block need to have the mains enlarged then rebabbited and bored for the larger crank, or can you just have the block line bored to fit the larger SCAT crank? I want to build up a spare motor with a C-35 head to replace the current one when the Sure-Mike goes.
I broke my first crank at 37,000 mile mark.
Keep your bearings in alignment& keep on trucking.
I haven't got any facts about how the std diameter SCAT cranks will hold up, but I can speculate.. New Ford cranks had a decent chance of survival for the life of the car, and still noone has cracked any of the SCAT's as far as I know.
But still, a chain isn't any stronger than it's weakest point, and the twisting forces are there just the same - even more concentrated to the thin bearing areas since the rest of the SCAT cranks are stiff and heavy. The manufacturer of the Dubats cranks analyzed the chinese steel in an early SCAT crank and wasn't impressed, but ok, he had his own crank to grind..
I think any crank with 1.248" mains in a large four cylinder engine is doomed in the long run due to the harmonic twistings in the crank, but they still just might hold up for 37,000 miles like Dean's did - and very few T's will need to cover that mileage.
A real crank shaft saver would be a harmonic balancer, a kind of flywheel at the front of the crank with an elastic rubber component that counteracts the most harmful twistings. But such a damper is hard (impossible?) to combine with the original oil pan and the front engine mount, so I guess we'll have to let them twist (and try to avoid the "thum" speeds)
If I'm lucky and my 26/27 crank holds up for 37,000 miles, I'll be good for another 12(?) years - and by then some other parts in the engine will likely also need attention.
(Message edited by Roger K on June 02, 2015)
Roger - Thanks for your thoughts above.
If the SCAT Crankshaft is the best available now, it's weak point is still the 1.248" Main and Rod bearing journals.
That brings us to Noel's question above on 1.5" bearing journals. Can anyone answer that?
BTW, I'd still like to hear from the Montana 500 guys....have any of you broken crankshafts? Can you tell us about it?
The notes are not complete about all the causes for the participants that did not finish, but among the last years results I saw two drivers got broken cranks in 2003, one in 2011 and one in 2013. http://www.antiqueautoranch.com/montana500/results/results.html