Warford Input Shaft Failure Analysis

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Model T Ford Forum: Forum 2016: Warford Input Shaft Failure Analysis
Top of pagePrevious messageNext messageBottom of page Link to this message  By Chris Bamford, Edmonton AB on Sunday, October 09, 2016 - 01:05 pm:

Hello All

We recently installed a cast-iron Warford in my '24 Speedster. Opted to ditch the front adaptor (and front universal joint) and bolt the transmission directly to the fourth main.

Eliminating the front universal meant the Warford input shaft had to be built up from 0.810" across the flats to 0.875" across the flats to be a good fit in the fourth main.

Welded up all four flats then machined them down to suit first two photos below.

The input shaft snapped in two after about 250 miles. Today I removed the transmission and had a look at the break. My assumption is that the shaft was probably solid until welding, or, more accurately, until after it air-cooled following the welding.

Third photo below shows the failure is concave toward the transmission and convex toward the engine. I expect this means something but don't know what.

Final two photos are closeups of the break area. I figure that little bit of sold material did pretty good to last 250 miles of highway speed and me learning how to shift!

What do you think was this a result of the welding, particularly air-cooling, or maybe a pre-existing weak point, or something else ???

I have now two replacement input shafts one is from an aluminum Warford and the correct size across the flats but is otherwise marginal compared to the other one, too small across the flats but otherwise good... If I wanted to use this second one and weld it up, what should we do differently?










Top of pagePrevious messageNext messageBottom of page Link to this message  By Seth in Alabama on Sunday, October 09, 2016 - 01:35 pm:

Chris, I have no clue about why that one broke. Lol hopefully someone will be able to look at it and tell you what it means. My gut instinct says that the part was allowed to get too hot while welding and then like you said - it air cooled and was too brittle.

Just as a side note I'd double check that the rear end spins freely like it's supposed to and that the rest of the Warford spins freely like it's supposed to.

My recommendation would be to keep hunting a good input shaft from an aluminum Warford rather than trying to modify a shaft. But that's just me.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Scott Owens on Sunday, October 09, 2016 - 01:45 pm:

Chris, The shafts that I make for race cars are air cooled. I think its the fact that you welded it is the problem. I would not weld the next one. Scott


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ted Dumas on Sunday, October 09, 2016 - 01:56 pm:

Why don't you make a new round stub shaft with a round extension. Then drill the original shaft and silver braze the extension in place. Then recut the square in line with the center of the shaft.


Top of pagePrevious messageNext messageBottom of page Link to this message  By David Dewey, N. California on Sunday, October 09, 2016 - 07:04 pm:

Did anyone think that the welding created lots of stress riser points with those sharp edges?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ted Dumas on Sunday, October 09, 2016 - 07:51 pm:

Internal sharp corners are extreme stress raisers. External sharp corners are not. The pictures look like it might have been cracked before any work was done. I recommended silver brazing because it is the strongest braze and heating with a torch will get the most of the assembly very hot such that if left in air it will cool slowly which is what you want.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Royce in Dallas TX on Sunday, October 09, 2016 - 08:22 pm:

I suspect the welding made the part brittle leading to failure. If you machine a new one from billet stock it will likely be fine.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Les Schubert on Sunday, October 09, 2016 - 08:33 pm:

Chris
My thoughts;
1. Perhaps cracks left after the welding. Yes I like the silver brazing idea, but perhaps even more I might like the idea of a shrink/press fit of the conversion piece to the shaft OR simply press it into the tail shaft of the T trans.
How much clearance did you have in that area last time?
2. Misalignment! You have a LOT of weight hanging on a quite "flimsy" attachment. I think you might be lucky it broke there, and didn't break the crank


Top of pagePrevious messageNext messageBottom of page Link to this message  By Tony Bowker, Ramona, CA on Sunday, October 09, 2016 - 10:25 pm:

I much prefer an Oldham coupling between the Warford and the rear of the Model T transmission. This avoids all the mis-alignment between the two. I suppose the weld could make any fractures worse and I would not have done it that way.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Wayne Sheldon, Grass Valley, CA on Monday, October 10, 2016 - 03:36 am:

Set up the chopping block. Grab the axe. I will stick my neck out.
I wouldn't trust welding a shaft like that. Gear/shaft material like that often doesn't take kindly to the various stresses of heating, cooling, and material flow. It takes someone with a lot more knowledge of metallurgy than I have to get it right. (First, you have to have a pretty good idea what Warford was using 90 years ago.) There are people that I would trust to weld one if I had to.

What I would have done, and would probably do now.
I know. Many people freak out and jump all over the place at the mere mention of (dirty word ahead!) (shudder) "shims". But I have taken enough things apart that had only kept running by proper use of shims. Properly made. carefully fitted, shims can fill the gaps, provide sacrificial wear material, and restore proper alignment. The specific stresses the shim will be subjected to determine how hard or soft the shim material should be.
Lighter forces may do well using brass shim stock (readily available in a variety of thicknesses. Heavier driving forces like this input shaft will be subjected to should use something tougher. For many things I use paint can steel. Usually spray paint cans (avoid using the welded seam.) The material is thin, easy to cut (sometimes difficult to drill if you need holes in it)

For a square shaft into a square hole, the shim should be carefully formed around the square shaft, Cut to near size, and clamped onto the square, then carefully folded to a tight fit. Use a small hammer to lightly tap the corners to a tight fit. You want to wind up with a one piece square tube/shim that slips onto the shaft tight. It is okay to not weld or close in the tube/shim. The thickness must be close to precise. Your final fit should be a snug slip fit. Grease all parts for final assembly.
The fit is important. If paint cans are too thin, you may need to find some other sheet metal that gets the fit right. I have even used material a bit too thick, and filed and sanded carefully to thin it down to the perfect fit.
Drive carefully, and enjoy, W2


Top of pagePrevious messageNext messageBottom of page Link to this message  By John McGinnis in San Jose area, CA. on Monday, October 10, 2016 - 07:26 am:

My view of this centers around what appears to be a bending fracture. I suspect a good job was done in building up and machining the square...probably providing an excellent fit. Here is the problem...it should have been a sloppy fit to allow for the flexing of the system. That is why the U-joint was used. The Warford cast iron is a large mass that cannot be restrained well enough to eliminate movement at the connection to the T transmission. This fracture is the same as that which breaks crankshafts at the flange through misalignment and pan flexing.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Chris Bamford, Edmonton AB on Monday, October 10, 2016 - 08:28 am:

Thanks to everyone for their comments and suggestions. We are still cogitating on the best approach for round two. Your input is much appreciated.

John, your suggestion to ensure a little extra clearance seems prudent. I can't say how much clearance there is into the fourth main now, but the broken stub did slide out quite easily.

John and Les both expressed concern about the mass of the Warford bouncing around behind the engine. I'm fairly confident of the fabricated support bracket we tied into one of the step plate brackets.

Further thoughts and comments are most welcome. Thanks again.






Top of pagePrevious messageNext messageBottom of page Link to this message  By Royce in Dallas TX on Monday, October 10, 2016 - 09:06 am:

I too think that you committed a fatal tactical error in choosing to eliminate the U joint. Neither the T engine or the Warford were intended to bolt directly to one another without a U joint. The U joint protects both parts. While the welding hastened the failure, that failure may have saved your engine.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Chadwick Azevedo on Monday, October 10, 2016 - 09:24 am:

Did you allow for any movement on your rear brace was it bolted tight?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Les Schubert on Monday, October 10, 2016 - 09:52 am:

Chris
My concern extends further to the amount of deflection you are certainly causing the back end of the pan to undergo by simply having all that weight bolted back there.
The T engine transmission unit is rigid!!!
The T frame is flexible and not all that strong (most frames I find are "sagged" at the firewall area.
I personally might get away with what you are doing, because I would install one of my "floating " transmission shafts
If you search the forum archieves you will find the research Paul Vitko did on pan/crankcase deflection


Top of pagePrevious messageNext messageBottom of page Link to this message  By Chris Bamford, Edmonton AB on Monday, October 10, 2016 - 10:22 am:

Hmmm, more food for thought.

Royce, the aluminum case Warford is intended to bolt up directly to the T transmission. Other than a larger-across-the-flats input shaft, I wonder are there other differences?

Chadwick, yes a little bit. The vertical mounting bolts at the rear of the Warford had rubber washers and the self-locking nuts not drawn up real snug.

Les, this engine has one of your floating shafts.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Larry Smith, Lomita, California on Monday, October 10, 2016 - 11:40 am:

That is why I gave up on Warfords. I had an original aluminum one for years, and a Ruckstell too! That car would go! But the input shaft kept wearing for some reason, so I got rid of it. I don't regret it.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Paul Vitko on Monday, October 10, 2016 - 12:02 pm:

The front U joint on my Mark E built like a blade screw driver fitting has been trouble free for many years with a heavy iron over and under supported with a modified cross member using heavy wall square tube.
I drive much less then you Cris but do drive nasty steep hills up and down some times using the under drive along with brakes for safety reasons.
That U joint makes me believe it has saved my crank-- it has only a small spring holding the two half's together with the blade part about 1/4 inch insertion into the receiving part--end play?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Les Schubert on Monday, October 10, 2016 - 12:33 pm:

Paul
Any chance of posting a picture (or a picture of a hand sketch would do too). I like your idea/concept, just want to be sure I understand the details of how you did it
Chris
I had forgotten (obviously I'm getting older)!!! So we can ignore that concern!!
As you will note above, I really like Paul's idea. I have great respect for his "engineering "


Top of pagePrevious messageNext messageBottom of page Link to this message  By John McGinnis in San Jose area, CA. on Monday, October 10, 2016 - 03:04 pm:

Maybe this is why Muncie has a U-joint on the input. Although it is hard mounted to the T engine/transmission, there must have been perceived (or actual) deflection of the transmission to warrant the U-joint. Muncie also has a support bracket in the rear.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Allan Bennett - Australia on Monday, October 10, 2016 - 07:20 pm:

Is this a possible application for a modified square section on the shaft, to mimic the ball drive on hex/allen keys? It should allow minor shaft misalignments to be negated.

Allan from down under.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Paul Vitko on Monday, October 10, 2016 - 11:19 pm:

In the past I fabricated a ridged square tube arm that bolted to the exhaust side of a 16 block. The end of the arm came to the end of the fourth main on the hogs head.
With a dial measuring the distance from the arm to the hogs head just setting in the drivers or passenger seat would change the side to side measurement 17 thou or more each way as I remember. stepping on the running board or rocking side to side in the seats did the same.
Those frames are weak. and that's why I like the later block with two bolts holding the hogs head to the block.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Tim on Tuesday, October 11, 2016 - 10:42 am:

Would this help the situation?

http://www.mtfca.com/discus/messages/118802/125070.html?1266623997

Found using my search engine - http://tfoye.com/modelt/ :-)


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Semprez-Templeton, CA on Tuesday, October 11, 2016 - 11:16 am:

Tim, Chris is using one of Les's floating shafts.

Les, How can one acquire one of your floating shafts?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jerry VanOoteghem - SE Michigan on Tuesday, October 11, 2016 - 11:55 am:

I agree with the thought that it broke due to its being welded.

Options:
- Get another shaft.
- Make a new shaft.
- Have a female spline EDM'd into the existing shaft and insert a new end, splined on one end and square on the other. The splined end could be a close slip fit or an interference fit. Use a good grade of steel and have it heat treated to a mid 40's Rockwell C hardness. Yes, it's an involved and probably expensive repair, depending on what machining resources you have.

I'll second Allan Bennett's suggestion to slightly crown the flats, which will allow for some misalignment. A .005/.010 crown is probably all that's needed. You could actually do some trig and determine how many degrees of misalignment a given crown would allow for.

Whatever you do, I sure hope you've got external accessory brakes!!!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jerry VanOoteghem - SE Michigan on Tuesday, October 11, 2016 - 11:57 am:

Chris,

How much "too small" are the flats on your spare shaft?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dick Fischer - Arroyo Grande, CA on Tuesday, October 11, 2016 - 12:16 pm:

Jerry makes a very important point:

"..... I sure hope you've got external accessory brakes !!!"

Whenever I think about doing something with the drivetrain in my T I try to remind myself that the drivetrain is the linkage between the brake and the wheels. That's why in the old days they called it the "emergency brake" instead of what we now call the"parking brake".

Dick


Top of pagePrevious messageNext messageBottom of page Link to this message  By Chris Bamford, Edmonton AB on Tuesday, October 11, 2016 - 02:01 pm:

We are starting the repair today. Rather than use one of my spare shafts, we'll cut the existing broken shaft between the bearings (photo below) and attach a new input stub of 4140 steel. The gear end will have a bored centre locating hole, the input end will have a matching centre stub. The matching faces will be Veed and welded. (When I say "we" are doing this, it really means a trusted precision machinist, his trusted journeyman welder, and me the guy writing the cheques and twisting the wrenches.)

Allan, that sounds like an excellent idea, thank you. As Jerry notes, it needn't be much of a crown, particularly with the floating transmission shaft.

Jerry, my spare shaft from an aluminum transmission is only a few thou small across the flats but the drive edges of the flats are worn significantly and the bearing cup integral with the gear is in very poor condition. This cup supports the inboard end of the output shaft.) My other spare shaft (in a complete cast-iron trans with a cracked case) is 0.060 +/- small across the flats which are sized for a U-Joint. My longer-term plan is to repair this cast-iron case, overhaul the innards, and install it (including the U-Joint extension!) in my '26 Touring.

Jerry and Dick, there are decent accessory brakes on this car 7" dia hydraulics on the front and newly-relined small-drum ACs on the rear. Both are operated by an external hand lever.

Thanks again to everyone who posted to this thread. I really appreciate your comments and suggestions, and will post updates as the project moves ahead.


Top of pagePrevious messageNext messageBottom of page Link to this message  By David Stroud on Wednesday, October 12, 2016 - 04:12 am:

I have built up worn shafts and missing gear teeth on dragline bull gears and other equipment using a "work hardening" stick welding rod several times in a past life. The idea is that the base of the weld metal stays somewhat "pliable", for lack of a better word, and the surface of the weld becomes "work hardened" from the contact of the gears/shafts as they are used. Worked very well, as long as everything is ground to fit as closely as possible. Don't know if such rod is still available. One that comes to mind is a Lincoln Welding product "BU (for build up) 90" rod that was developed for building up dozer rollers and rails (Bud will no doubt recognize that). Worked very well, and was very handy for many other applications. There were many other brands, but that one comes to mind. JMHO Dave


Top of pagePrevious messageNext messageBottom of page Link to this message  By Paul Vitko on Wednesday, October 12, 2016 - 11:20 am:

If I were checking a half day of removing the intake and exhaust manifolds and make an arm described in the post above would be done. The cross members and supports look weak. If nothing else I would sleep better.


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