4th main

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Model T Ford Forum: Forum 2009: 4th main
Top of pagePrevious messageNext messageBottom of page Link to this message  By Rob Mills on Monday, December 28, 2009 - 09:13 pm:

I am thinking about using the Texas T ball bearing 4th main that requires no machining, has anyone used it and what are you thoughts? Do you need to use the tail shaft locator from Langs to get everything straight or can you follow the book for ligning everything up?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Les Schubert on Monday, December 28, 2009 - 09:19 pm:

Rob
I wouldn't.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Kenneth W DeLong on Monday, December 28, 2009 - 10:26 pm:

When the crankshaft broke in our 14 i found the ball bearing 4'th main had went bad.The rebuilder said otherwise my engine was in good shape untill the crankshaft broke?? $ 2500.00 and a total rebuild later a STOCK 4'th main was used!! Good luck! Bud.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Rob Mills on Monday, December 28, 2009 - 11:45 pm:

Ok it is starting to sound like the Ball bearing 4th isint the way I should go. Does this include the main that need the tail shaft machined or is it just the one that is press fit?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Les Schubert on Tuesday, December 29, 2009 - 12:56 am:

Rob
Personally I am a big fan of the ball bearing 4th main. Unfortunately most of them are not made right. The rotating race needs to restrained (light press fit). The outer race needs to have some slip axially. The bearing needs to be installed so it carries radial load but does not resist thrust.
If it is not done right you risk;
1. tearing up the bearing because it is improperly loaded.
2. tearing up the output shaft because it is slipping on the shaft
Neither circumstance is desireable
The ones commercially offered seem to mostly have missed these requirements. It is unfortunate.
So while I continue to make my own for my use I am afraid that does not help you


Top of pagePrevious messageNext messageBottom of page Link to this message  By Tim from ModelTengine.com on Tuesday, December 29, 2009 - 09:14 am:

Les is right. The crankshaft and transmission grow and shrink with temperature changes just like the pistons. It all needs room to stretch.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Adam Doleshal on Tuesday, December 29, 2009 - 11:50 am:

I've known several people who have used them and they all ended in failure of some sort or another. Usually the inner seal fails then the bearing fails and then the shaft breaks loose and turns in the inner race... And this is the best case.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Rob Mills on Tuesday, December 29, 2009 - 11:33 pm:

Ok, I will not use the ball bearing 4th main! But, the original one I have seems to be in good shape but it seems to have quite a bit of clearance, what should it be and what should the tail shaft measure? Should I buy a rebabitted one or what? This kind of threw a little monkey wrench in my plans right when I thought I had it figured out. Thanks for all of the help.. We are getting closer by the day... Rob........


Top of pagePrevious messageNext messageBottom of page Link to this message  By Les Schubert on Wednesday, December 30, 2009 - 12:24 am:

With all due respect I have run them for many thousands of miles over a 30 year period with zero problems. BUT they need to be done right and there in lies the problem. I have NEVER torn one up yet. And so Rob I think your decision is the right one.

Babbitt 4 th main; I figure .001-.003" clearance if I was going to use one just like the rest of the main bearings.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Danuser on Wednesday, December 30, 2009 - 09:23 am:

Les I also ran one for 15 years driving to all the MTFCA Natl meets and regional tours, NEVER any problems on a shortened A cranked T engine in a 26 touring


Top of pagePrevious messageNext messageBottom of page Link to this message  By Kenneth W DeLong on Wednesday, December 30, 2009 - 10:15 am:

If my post sounded like i was aginst anyones ball bearing 4'th main i dont know that much about them.I do know what i found when i broke my crankshaft! A model T runs unfiltered oil everywhere and with aq semi rigid crankshaft in a semi ridged crankcase why have one bearing with no give like the others?? Baffled Bud.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Fred E HoustonD on Wednesday, December 30, 2009 - 12:34 pm:

Evidently it depends. I've been running one in my Fronty with an A crank since 1975 with no problems. They were manufactured locally by an elderly machinist, pattern maker with an excellent reputation, long since gone. On the other hand, there's nothing wrong with a babbit bearing.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Adam Doleshal on Wednesday, December 30, 2009 - 12:49 pm:

.002" to .003" fourth main clearance would be ideal in an engine that has been completely precision balanced and blueprinted. Unfortunately, the average T engine was subject to enough manufacturing variences that fiting a fourth main that tight may cause bearing failure. Usually, I would consider .004" to .005" about right on something that hasn't been completely rebuilt and verified for correct runout. They were originally manufactured with clearances even greater than that for just that reason.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Brent in 10-uh-C on Wednesday, December 30, 2009 - 02:36 pm:


quote:

The crankshaft and transmission grow and shrink with temperature changes just like the pistons. It all needs room to stretch.




I agree, in theory you are correct, ...but by how much? Does the pan grow also counteracting some of this? Does the crank expand "forward" offsetting some of that growing/shrinking dimension??


Top of pagePrevious messageNext messageBottom of page Link to this message  By Norman T. Kling on Wednesday, December 30, 2009 - 02:40 pm:

Don't worry about how much it grows. It would all depend on how hot the car runs and whether you are going uphill or downhill. If you use a good babbit bearing you have no problems. If you use a ball bearing and it's properly built and installed, no problem. If it's not broken, don't fix it!
Norm


Top of pagePrevious messageNext messageBottom of page Link to this message  By Paul Vitko on Wednesday, December 30, 2009 - 02:53 pm:

Think Adam is right, when you can step on a running board and move the 4th 7 thou horizontally and 3 thou vertically or pull the emergency brake and push it up 20 thou tight might not be a good idea----- no proof though.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Les Schubert on Wednesday, December 30, 2009 - 03:08 pm:

I don't argue with the "upset conditions" people quote but I will stick with my number when you are running down the highway.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Kenneth W DeLong on Wednesday, December 30, 2009 - 03:33 pm:

Apples is apples but ornges aint! Two A crank conversions are just that.Were both A cranks turned down to 1.248 and even if they were,were the webs reduced in size and the quality of the steel?? International used a Ball bearing on each end of a crankshaft for several engines and still today i have never heared of a failure,but they used a large stiff crankshaft,filtered oil,heavy crankcase,large bearings! In a model T engine what is actually gained with a ball bearing over babbitt?? Bud.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Rob Mills on Wednesday, December 30, 2009 - 07:19 pm:

Where would you find a properly built ball bearing assembly? I was going to buy one from Tesas T's but now I am scared of it so I might stick with the stock OEM parts.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Rob Mills on Wednesday, December 30, 2009 - 08:22 pm:

Ok I just tried to measure my shaft and ball cap and this is as close as I can get, shaft 1.557 and the Ball cap is 1.564 I tried taking main bearing shims and sticking them in as feeler guages and I was able to put 4 in, One top bottom left and right and was still able to turn the ball cap but there was drag on it. Is this close enough for a motor that is just putting around locally or should it be tighter? If I buy a rebabitted ball cap from Langs it would be 3 thou tighter, they say you should be between 4-6 but I think I am closer to 4-7. Using my digital mic I was getting 1.561 top to bottom and 1.564 side to side?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Rob Mills on Wednesday, December 30, 2009 - 08:31 pm:

Ok I just re-read all of the posts and think my questions are all answered here, I did all of the bearings in this motor, removed the magnets and installed a oil slinger but the runout on the tail shaft was not done since this is not by any means going to be a touring car just a local dirt road joy rider. I think the ball cap I have is going to work just fine. Thanks for all of the help again and again... Rob....


Top of pagePrevious messageNext messageBottom of page Link to this message  By Les Schubert on Wednesday, December 30, 2009 - 09:04 pm:

Rob
The best part is you are making a informed decision. I respect either way you go on this.
Bud
One advantage is one less oil leak as well as you stop filling up the rear axle with engine oil.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Kenneth W DeLong on Wednesday, December 30, 2009 - 10:15 pm:

Les,The one i found in my engine was open on the face and i don't rember if the back was sealed or not?? I also don't know how or when it was installed? This is hard to belive but after the compleat rebuild i don't have any oil leaks to speak of! Maby i had better check my oil?? Happy New Year!! Bud.PS,It must have been sealed on one side?? Bud.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Tim from ModelTengine.com on Wednesday, December 30, 2009 - 10:16 pm:

I've run a few T's. Some with ball bearings and babbitt. So far I am not a member of the broken crank club. The ball setup worked for me, some leaked some didn't. The bottom line for me is this: There is controversy about this product. There are numerous crankshaft breakages associated with it - proven and unproven. It's a potential liability so I don't put them in my customers cars. Babbitt works so that's what we use. If it's fit right it doesn't leak.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Norman T. Kling on Thursday, December 31, 2009 - 10:22 am:

A few things about Babbit. 1. Henry used it. 2. All the other mains and rod bearings are Babbit. A Babbit 4th should last as long as the other bearings and when you have to pull the engine, you can check it and replace/repour as needed. 3. They have lasted for up to 100 years.
Norm


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