Crankshaft end-play

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Model T Ford Forum: Forum 2015: Crankshaft end-play
Top of pagePrevious messageNext messageBottom of page Link to this message  By Dave Young in Mays Landing, NJ on Sunday, December 20, 2015 - 07:50 pm:

What would cause the thrust surfaces of the rear main to wear rapidly? I've got my engine torn down at this time and was very surprised to find that my crankshaft end play is .014". This engine was rebuilt 4 years ago by a very reputable shop and has about 6,000 miles on it. The block was re-babbited at that time and everything was set to the proper specs. The fellow has since retired and here I am. Is this sort of wear par for the course. I changed the oil every 400 miles and she ran great. I pulled it out because I was getting metal in the oil, which I thought was coming from the aluminum timing gear. Four years ago, the crank was moving .012", and that's what prompted me toward having a total rebuild done... And now I'm right back there again.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Roger Karlsson, southern Sweden on Monday, December 21, 2015 - 04:47 am:

The only thing that pulls the crank axially in the thrust direction is the clutch spring. Have you run the engine a lot in neutral / low or reverse?

(The angled teeth on 1919 and later timing gears would also give a little resultant force in the axial direction, but that's minor and insignificant compared to the clutch spring)

Was the crank shaft reground during the rebuild? Maybe the thrust surface on the crank wasn't properly smoothened out? (even reputable people makes mistakes sometimes..)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dave Young in Mays Landing, NJ on Monday, December 21, 2015 - 08:13 am:

The crank was not regrouped. When I drive the car, I do use the clutch lever for braking most of the time. It's a 26. I feel it's easier to replace brake lining than band lining. I see what you are saying about the clutch spring effect. Interesting.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Roger Karlsson, southern Sweden on Monday, December 21, 2015 - 08:42 am:

With a properly smooth thrust surface on the crank you should be able to run in neutral a much longer time without significant increase of the axial play, I think. Maybe the surface was rough and since the crank wasn't reground, maybe the crank wasn't completely checked in all areas?
Hopefully it was magnafluxed :-)

On a '26 with a four dip pan maybe it should be possible to take out the third main cap and check the thrust surface without pulling the engine (at first)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Donald Conklin on Monday, December 21, 2015 - 09:00 am:

An improperly ground thrust surface can certainly take out the thrust surface on the babbit. (the pitting on the thrust surface was not completely removed when the engine was rebuilt) Of course the engine ran longer than the 90 day 4000 mile warranty so the rebuilder would not warranty it.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Norman T. Kling on Monday, December 21, 2015 - 12:23 pm:

If you go uphill in low for long distances your crankshaft will be forced to the rear by gravity and the clutch spring will also pull the flywheel toward the back. That would move the magnets farther away from the magneto ring.

It is not good to leave the engine idling in neutral for long periods of time nor to use low for long periods. So if you live in an area with steep hills it is best to have a Ruckstell or other auxiliary transmission to shift down while ascending or descending steep hills.

Norm


Top of pagePrevious messageNext messageBottom of page Link to this message  By Eric Hylen- Central Minnesota on Monday, December 21, 2015 - 12:37 pm:

My guess, is that you're finding proof of poor workmanship. Sadly, your "very reputable shop" didn't recognize the importance of properly grinding the crankshaft as part of the rebabbitting process. You might be able to correct their errors by having the crank ground, fitting a new 3rd main and running in all three mains with timesaver. Otherwise, you're probably looking at having the whole babbitt job redone.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jerry VanOoteghem - SE Michigan on Monday, December 21, 2015 - 01:20 pm:

Dave,

Not having your crank reground was most likely where your trouble comes from. The thrust bearing surfaces on the crankshaft do not wear evenly. The wear forms a groove on the thrust faces. When you size a rebabitted 3rd main, it has to be narrow enough to pass by the unworn, high spots on the crank thrust faces. Once past those surfaces, the main cap "falls" into the existing wear groove in the crank, getting right back to the same excessive clearance you always had.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Kohnke Rebabbitting, Clare, Iowa on Monday, December 21, 2015 - 02:06 pm:

Eric is right, but what we see through here is, that kind of clearance was cut that way or very close to that way when new.

You should have all the thrust surface at .003 to not over .004, end play, when new. That should stand up to thousands of miles to get even 1/2 a thousands of miles with out even a 1/2 thousandths of wear.

Most of the time we see much more then that with high spots less, and when the high spots wear off, that is where the high clearance comes from.

And yes, the thrust should always be touched up, on the crank.

You can not get the thrust perfect using a machine for the final 2 or 3 thousandths cut, we always hand scrape, to get 100%.

Herm.





Top of pagePrevious messageNext messageBottom of page Link to this message  By Norman T. Kling on Monday, December 21, 2015 - 02:16 pm:

Beautiful bearings, Herm
Norm


Top of pagePrevious messageNext messageBottom of page Link to this message  By Kohnke Rebabbitting, Clare, Iowa on Monday, December 21, 2015 - 02:38 pm:

I must have passed over the center main picture after the crank was in.

Also some pictures of Vern's cranks that he grinds for me.

Note: Radius, the correct size, touched up flywheel side, front seal and Pulley area straight, rebuilt Pulley pin hole, as needed, Mains, and rods Zero run out, and, or taper. Very High polish on mains and rod pins. The center lines .000-00 to .000-50 run out.

Cranks always crack checked with Black light.

Vern Phone 800-765-2926

Herm.



Top of pagePrevious messageNext messageBottom of page Link to this message  By Dave Young in Mays Landing, NJ on Monday, December 21, 2015 - 06:27 pm:

So, I checked back thru my records from the rebuild of this engine and it does in fact show that the crank was ground, magnafluxed and the crank flange was faced. It also brought back the painful reminder that this rebuild cost as much as most cars... $7,800. Yeah. I figured that as the caretaker of this fine little Model T, she would tick along for the next 30 years of my life, and all would be good.

Well, at 7 months after the rehab and about 2,000 miles, the T was sitting in my driveway, idling, as my wife and I loaded luggage into our car trailer, about to head out to a 3 day tour. The T made a loud metallic bang and stopped. It had seized up solid! We winched it into the trailer and hauled it the 5 hour trip to the engine shop and worked together to pull the engine and find the trouble. Turns out a wrist pin had welded itself to those fine import pistons.

Two months later, I got the motor back and into the car. Lately, shes been getting noisy. I drive it a good deal, and pulled the head this fall to take a look in there. Not pretty. The cylinders and pistons had galled. I had the block honed to give me .005 clearance on a new set of Egge pistons which have the ring land area relieved by .030". The fellow had set it up with only .0025 clearance before, which i guess is alright for a parade car, but not a driver.

Herm. My wife gave you a call this morning about me sending my rods out to you to be checked. Thank you. I'm thinking they certainly got stressed when the engine seized up and I don't know that they were checked at that time.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Erik Barrett in Auburn Ca. on Monday, December 21, 2015 - 09:57 pm:

Dave, we see this kind of thing all the time. People build engines and transmissions too tight, thinking they will get years more service out of them when the opposite is true.
We use a bronze thrust on the front of the rear cap. Lasts forever, even with a heavy clutch spring.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dave Young in Mays Landing, NJ on Monday, December 21, 2015 - 10:09 pm:

I haven't pulled the pistons and crank out of this block yet, but I have it out and on a stand. I just noticed that each rod appears to be visibly forward of center of each piston. In the photo below, I have the crank thrust tight rearward and the rods are still forward of center within the pistons. What's going on here?

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Top of pagePrevious messageNext messageBottom of page Link to this message  By Dave Young in Mays Landing, NJ on Monday, December 21, 2015 - 10:43 pm:

I have not measured yet to see if the rods are in fact off center with the bores. Is it possible that the Egge pistons are just cast this way and give the illusion of off center?

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Top of pagePrevious messageNext messageBottom of page Link to this message  By Frank van Ekeren (Australia) on Monday, December 21, 2015 - 11:15 pm:

Your looking for something you wont find in a model T engine, modern day build and specs, all looks normal other than getting rid of that tie wire on the rod bolts, replace with split pins, even your thrust clearance still comes in on a mileage run T engine, a magneto gap of up to .040" is still with in specs for a magneto to operate correctly.
Fix the babbitt on the 3rd cap because you now have it out. What oil I can see in your photo's doesn't look metal contaminated, are you finding large pieces of anything?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Kohnke Rebabbitting, Clare, Iowa on Tuesday, December 22, 2015 - 12:02 am:

Dave, take pictures of each main, and the front end of the gear to look how it lines up with the front end of the block, at the front cover gasket surface.

There are only two things that will throw off centering the rod in the cylinders.

1.Crank placement.

2. Off set in the rod, or bend. Twist won't effect that movement.

Herm.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Kohnke Rebabbitting, Clare, Iowa on Tuesday, December 22, 2015 - 12:41 am:

Dave, take pictures of each main, and the front end of the gear to look how it lines up with the front end of the block, at the front cover gasket surface.

There are only two things that will throw off centering the rod in the cylinders.

1.Crank placement.

2. Off set in the rod, or bend. Twist won't effect that movement.

Herm.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dan McEachern on Tuesday, December 22, 2015 - 11:30 am:

Looks to me like that crank gear is totally worn out, and that did not happen in 6000 miles. Just sayin.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dave Young in Mays Landing, NJ on Tuesday, December 22, 2015 - 01:18 pm:

I'll take those photos tonight. The oil visible in this picture has only about 15 minutes of run time on it. The previous oil changes of an hour or two of running all came out looking like pixie dust. Nothing large enough to pick out, just a metallic sheen. I had sent the oil to Blackstone labs and they saw nothing. Must have never even looked at it...


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dave Young in Mays Landing, NJ on Tuesday, December 22, 2015 - 09:08 pm:

Herm, is the thrust controlled by both the rear main block Babbitt and rear main cap Babbitt, or just the rear main cap Babbitt?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dave Young in Mays Landing, NJ on Tuesday, December 22, 2015 - 09:27 pm:

Dan. That crank gear does look pretty beat. Yet, according to the invoice, it was brand new 4 years ago! if I lived closer to Iowa, guess where I'd be going?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dave Young in Mays Landing, NJ on Tuesday, December 22, 2015 - 09:36 pm:

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Top of pagePrevious messageNext messageBottom of page Link to this message  By Dave Young in Mays Landing, NJ on Tuesday, December 22, 2015 - 09:38 pm:

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Top of pagePrevious messageNext messageBottom of page Link to this message  By Allan Bennett - Australia on Tuesday, December 22, 2015 - 10:13 pm:

Dave, I have been following your posts and offer these thoughts. Dan noticed the worn steel crankshaft gear. I suspect that was not replaced in the re-build. That worn gear may well be the source of the metal in your oil. It will certainly chew away at an aluminium timing gear.

Your question to Herm re the thrust faces at the rear main: Usually there is a thrust face on the main cap only. To have a thrust face on the block would involve tinning the block before pouring the bearings as is done with rod bearings. This is not done due to the heat required to have the whitemetal adhere to the tinned surfaces. They are poured and then peened in situ, being held in place mechanically by the drill holes in the block. At least, that is how my man does it. Others may vary.

Hope this helps.
Allan from down under.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Kohnke Rebabbitting, Clare, Iowa on Tuesday, December 22, 2015 - 10:27 pm:

Herm, is the thrust controlled by both the rear main block Babbitt and rear main cap Babbitt, or just the rear main cap Babbitt? "END QUOTE"

On many motors, when placing the crank, I have found that a low mileage block utilized the block part also for crank thrust.

We have done many blocks fit with a Babbitt thrust, if the customer so desires.

I am with Dan on the crank gear!

It looks like the crank is pushed ahead to the rear flange, but it is still away from the Babbitt thrust on the cap at the top.

I would say from the pictures, crank placement is close?

Herm.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Kohnke Rebabbitting, Clare, Iowa on Tuesday, December 22, 2015 - 11:22 pm:

When you put a thrust on a block, you never try to tin cast iron.

You have to machine the block thrust off to what you need, and then replace it with Babbitt that is peened, just like the Model A's, and B's.

From what I have seen, the block was used for the top half of the thrust.

Here is a low mileage 1913 block, I put in a Scat crank.

Note the block thrust, after I marked the crank out, it ended up where it always does.

Here are the pictures.

Herm.


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