Preventing the "Broken-Crank-Blues.." Anybody tried this?

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Model T Ford Forum: Forum 2015: Preventing the "Broken-Crank-Blues.." Anybody tried this?
Top of pagePrevious messageNext messageBottom of page Link to this message  By James J. Lyons III - West Virginia on Tuesday, June 02, 2015 - 07:58 pm:

So, I've been following the threads on the 2-piece crank stories and I've been considering my own situation with two brass era cars that still sport the original motors. Well, The engine on the 15 is kind of tired so I'm thinking of taking it out this winter and going through it.

That got me thinking about the crank, the 4th main... and how to assemble it all so that it is in a relaxed state.

A lot of pains are taken to make sure everything (meaning the 4th main) lines up when the engine while it is vertical and on the stand. But as soon as you flip it horizontal to put it in the car, the weight of the transmission goes on the crank and things are going to sag. So that got me thinking about solutions to the problem.

The sketch shows my proposed solution to the problem. When the engine is on the stand and assembled, I am planning on match-drilling two holes through the 4th main flange, into the beefy web of the pan. These holes would allow a press fit for a select hardened pin... I'm thinking an 1/8th inch pin. With the gasket and flange located, the pins are pressed in place, securely holding the 4th main at the relaxed location. The length can be trimmed with an angle grinder (make sure you cover any holes!) so that the pin does not extend beyond the thickness of the flange. When you are ready to install the engine, the pinned 4th main should stay in the proper location until you can bolt the drive shaft up, keeping the transmission shaft in proper alignment.

Hurl you suggestions, praise, insults and broken shards of glass. I'm all for coming up with a way to precisely maintain alignment to reduce stress on the crankshaft.

pin


Top of pagePrevious messageNext messageBottom of page Link to this message  By joe bell on Tuesday, June 02, 2015 - 08:03 pm:

James, I have seen the time taken for pinning the fourth main, wish I had a picture of the 14 with the broken crank! I think is does help but the diamond cranks are weak and if you run them all the time, it is only a matter of time till you join the club.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bud Holzschuh - Panama City, FL on Tuesday, June 02, 2015 - 08:47 pm:

Sounds like a good idea. Can't see any downside to it. I'll save the post and try it on the next rebuild!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Walt Berdan, Bellevue, WA on Tuesday, June 02, 2015 - 09:16 pm:

I've typically played with the 19 or later engines so I may be missing something but I've usually found the 4th main to fit quite snugly in the pan and trans cover. My approach has been to set the engine vertical, check runout of the tail shaft and then check the fit of the 4th main to the pan. Now I am a member of the 2 piece club having broken 2 on my speedster over 20 years. A combined 30+ years on my touring and coupe with stock motors never had a crank issue. I am knocking on wood as I type this though as I believe the bit about "when" rather than "if".

Then again I've seen pinned 4th mains and I can't imagine they could hurt if all is aligned before they are drilled. If it makes you feel better, go for it.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Kohnke Rebabbitting, Clare, Iowa on Tuesday, June 02, 2015 - 09:52 pm:

The biggest cause to a crank breaking, Ford did it them selves.

On both sides of the center main, they went in with a grind wheel and cleaned up the casting, or forging leaving a square radius, and they will crack there sooner, or later, as some of the broken crank pictures showed.

That's where we check first.

Herm


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bob Gruber- Spanaway, Wash. on Tuesday, June 02, 2015 - 10:41 pm:

I did exactly that to one about 5 years ago.
It's my son's T and he doesn't baby it.
Don't know how many miles but it's still going strong.
It's a diamond shaped crank.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Allan Bennett - Australia on Tuesday, June 02, 2015 - 11:19 pm:

My speedster has the 4th main cap drilled and fitted in place with two 3/16" countersunk set screws threaded into the casting on the pan. This makes removal easy. Then just fit the rest as usual.

Hope this helps.
Allan from down under.


Top of pagePrevious messageNext messageBottom of page Link to this message  By WilliamThomas Forsythe on Wednesday, June 03, 2015 - 12:04 pm:

In a previous contribution to this subject, I had mentioned installing the ball cap with the engine in the verticle,and a truly centered "slide fit" on the transmission output shaft.I neglected to relate that as well as installing the four bolts, 2 into the hogshead and 2 into the end of the pan to position the ballcap,I also drilled and tapped into each-(hogshead & pan) and installed 1/4"x 28 flat head allen head cap screws which lock the ballcap on center.As to the weight of the transmission pulling the rear end of the pan downward,I installed the support plate as outlined.Thus all stays in line when the engine is in the horizontal position.My plate is providing the same "improvement" as Ford has done in '26 and '27.Regards,Tom Forsythe


Top of pagePrevious messageNext messageBottom of page Link to this message  By clifford prince on Wednesday, June 03, 2015 - 03:00 pm:

Well...I have been measuring pan gaskets.New ones measure 0.049 and the ones removed after an engine strip have measured 0.034..so during use they have compressed by 15 thou.So no matter how carefully you check the fourth main alignment when building the engine it would seem vertical alignment will suffer with time.Having said that both crankshafts I have broken have been between number one and number two and I don't think fourth bearing misalignment would have contributed much to this.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Les Schubert on Wednesday, June 03, 2015 - 07:37 pm:

My solution is a "floating" connection of the transmission shaft to the crankshaft. So far it seems to be working out as planned. About 10 of them in service for 5 years


Top of pagePrevious messageNext messageBottom of page Link to this message  By Tim Wrenn-Monroeville OH on Wednesday, June 03, 2015 - 07:39 pm:

Clifford, I'm certainly no mechanic, and definitely no expert, but if the 4th. main is misaligned, being at the opposite end of #1 & #2 I would think the "bending" of the crank from that opposite end would definitely contribute to the forward break.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Gene Nelson - Eastern Iowa on Wednesday, June 03, 2015 - 09:38 pm:

Les,
could you tell us more about "floating" connection of the transmission shaft to the crankshaft?
Gene


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