And it wasn't Ford.
No wonder photo's of centre crank bearings rebuilds are way off spec, who ever is supplying the vendors of change over center caps has it wrong!!
Length of journal is 2-3/16"
Length of cap is 2-1/8"
Service specs of clearance is 1/32" to the 1/16"
VENDORS SUPPLY!! 2-1/32"
3033 Fords factory specs of center cap Length!!
And I get accused of not knowing what I'm doing when working with Ford specs, some need to have a re-think!!
Frank, if dealers are supplying 2 1/32" long caps, they do indeed not meet Ford's spec.
Ford designed the cap at 2 1/8" and at that length, it would give a clearance of 1/32 to 1/16" on the journal. The Ford Assembly manual states as such, and also describes that this clearance is to allow for expansion/lengthening of the crank shaft. It is not intended to provide thrust capability, and with a properly fitted 3rd main, will never ever contact the crank in a thrust capacity and is not stated or implied that it will, in the manual.
In reality, there is negligible loss of life in a cap that is somewhat shorter as the vendors supply, as I believe that the babbit can withstand something like 10,000 lbs per square inch, and I wouldn't worry about the loss of bearing area. There are many more marginal features of a 100 year old engine that merit attention!
If you're trying to prove that vendors don't supply a part that meets Ford Spec, then you're right, I guess. I'd bet that it depends on the vendor you use.
If you're trying to impute and then prove some thrust function to an original Ford center main bearing made to Ford spec, you're simply wrong in your understanding of the spec. Every manufactured part has a min/max dimension, and every system designed with a running clearance has a minimum designed clearance. Ford designed it to completely, positively and always clear the crank...not constrain it.
If I've misunderstood your post or intent, then I'll apologize right here.
So, you're claiming that the vendors supply a center main cap that's 3/32" shorter than Ford specs. How exactly does that impact anything? As Scott states, it's a bit less bearing surface but, nothing to be concerned over. (I agree) Beyond that however, I fail to see the issue.
1 major in packed from the go-set 2 long term problems
1, the ability for the main to maintain it's internal oil pressure!
2, the journal to carry the full load of piston thrust and prevent the crank from cracking at the radius cuts!
3, Henry built in a safety feature on fitting the wrist pins bushings on cast pistons that if it ever happened that the big end failed, the pin would not score the bore, something that has been lost with aluminum pistons, point being, this is the same thing for the magneto, the thrusts wear on #3 and the shaft begins to float, now set the #1 and
#2 to Fords specs, that gives you the expansion clearance needed and also over time a longer engine life for the magneto preventing the magneto being chewed up past it's own spec clearances.
Remember Ford specs require the rebuilder when the shaft is out by .002" out of round and the journals more than .012" wider, to fit a new shaft.
We don't if we can reclaim with a crack test and regrind, so we need to replace and cut the babbitt to the right specs.
The position and end play of the model T crankshaft is determined by the rear main bearing. Period. The length specs Ford provided for the front and center main caps were to prevent them from being interchanged by mistake. If the rear main bearing thrust fails, the life expectancy of the front and center main bearing fillet radii to control the end play can be measured in minutes, when that clutch spring hauls back on the crank in anything but high gear. This was not something Ford was concerned with. If a rod or main bearing failed, you took it in for repairs.
Cranks breaking at cracks originating at the fillet radius are caused by a few things. One is being 87-106 years old. Another is being reground with the fillet radii too small because doing it properly requires modification of expensive grinding wheels. I have a grinder who will do it correctly, but I take him 15-20 cranks at a time so the grinding wheel mods are economically justifiable.
Erik, your scenario is very floored, the babbitt flange is a very viable bearing, even when it gets to the stage of running on and of a radius cut, if it will self destruct in minutes then big end bearings are stuffed on start-up. The wear on the 1st and 2nd if it ever gets that far, can not exceed the speed of wear of the thrust face on the 3rd cap, if the thrust flange was to disintegrate in a instant, the caps kept in Ford specs will prevent the crank floating the magneto to destruction.
My whole point of this is a set of specs are easy to follow and work with, to build a engine that already exceeds specs by whole fractions instead of thou's is pointless.
Frank, I respectfully disagree. The big end bearings do not have 90 pounds of clutch spring pressure hauling them sideways. The side thrust on the rods is near zero unless they are bent or otherwise misaligned.
If the thrust bearing failed to the point where the front and center bearings controlled the crank position, the magneto would barely be functional as the gap would be too wide. It would not be destroyed, however. Remember that clutch spring? It pulls the crank and magneto rearwards, away from the field coil.
All this being said, you are perfectly correct that using parts that are out of specs is poor practice. T parts are not that hard to get. If you build an engine, it's worth doing right.
True Erik, but I send cranks in that require both thrust face clean-ups, have you seen a T eat a magneto? they make an impressive mess, it's fascinating on how big a piece and how much of copper winding can be in bedded into babbitt bearings, I'll take photo's if or when, for the next one that comes in.
Agree with you Frank, I have the thrust faces cleaned up on the cranks. It's hard to find a grinder who will grind cranks to our specifications. I have seen a few magneto destruction events. In fact, I was driving during one of them many years ago. Looks like someone dumped a load of copper spaghetti into sausage grinder. Not pretty, something to be avoided. The ones I get here are usually due to failure of the hardware that holds the magnets to the flywheel or magnets picking up a foreign object like band nut or washer. End result is messy no matter what.
There is only one thrust, and that is the third main. The other caps should never come in contact with the crank. I see no problem with the second main cap being smaller in size than the block. In the pictures the caps used are in fact the ones that ford supplied with that block. Also please next time some one post pics of a rebuild and something looks off, ask before you make your own conclusion. Also maybe post pics of your completed work so people can poop on your pride and joy. I added a pic taken with a cell phone of the fourth rod that you think will put a wrist pin into the wall, I can even see with a awful pic that it does not have the eighth inch end play YOU think it does. J and M has rebuilt hundreds of model t engines, and Cadillacs, Packards, Jaguars, and even Duesenbergs. Oh yeah, they also make new all new drums, according to ford specs given to them by Ford, I think they know what they are doing.
I do apologise if that's the case, it is very de-sieving! Front and center specs are an other story.
Sorry Dav, that #4 looks fine, I was looking at the wrong end, it's the photo of #1 in ?, more photo's please!
Thank you Frank, apology accepted, All of the rods are the same. I will post more pics of it. Your specs for the cap only go to 1923, what happened after 23?
For those who may be interested in Ford specs, although they are Ford Canada period prints, it shows clearly flanging of main caps to put the crank to clearance specs.
Have you fitted a scat cranks to a model t block, the new cranks are nothing like a stoke crank for a good reason. I would hardly call the artist rendering a spec though.
meant to say stock crank, the new cranks are far different. Also the pic in the last post, How can you be sure that ford poured that bearing? I didnt take pics of the rest of the rods, they are all perfect! Dont have time to do it right now. Could you post pics of your completed bearings?
David, I would love to show you fresh jobs but I'm still waiting for the return of 3 shafts, the first several years of T's had Dodge Brothers caps, that's how the specs are set with babbitt flanges, what the issue is now is specs being out from over machining that can be compensated for by earlier ways.
If the crank width on the journal comes in on spec
Block is 2-1/8 and a good Ford cap comes in at the same all is great.
Now using the min clearance for a 0 mile 0 hour rebuild, center the shaft, we have just over .015" each side.
Now we go back to the #1 reason, 'oil'
to put it simple if you have a hole in a bucket we don't make it bigger to hold it's contents.
The splash system relies 100% on making it's own hydraulic pressure.
We have a 360degree hole both sides, fluid, like electricity, will take the path of least resistance, oil will head straight for the sides leaving minimal to do it's job.
Read this below will explain it better on oil.
This is an over machined crank to 2-5/16"
This is one of Herms jobs, Flanged to at least bring the cap back to Ford specs of 2-1/8".
Frank, wrong again!
What you are calling an over machined crank of 2- 5/16 is the norm for standard Model T cranks before machining.
They very from 2.200 to about 2.350, and some times under that, and sometimes greater then that by a few thousandths.
Frank, your lack of Model T experience is really screwing up your flawed research.
I was waiting for your reaction Herm, to defy Fords specs is to admit they mean jack to you so what you say is gospel and to agree with me is to admit you have been screwing it up for years.
It's all about trust, the average T owner puts his trust in a machinest to build a new engine, the machinest puts his trust in engineers to set the specs, which Ford has done very well.
Now I have a 40 year old piece of paper that states I'm am Engineer, what do you have?.
Just some specs to re-freshen your memory!!
Frank, I will say it again, I put babbitt on the sides for no more then looks, and for when I cut the Radius, so the cutter don't want to bob in and out. The crank will never touch the cap or block by a long shot.
Those caps never did have babbitt on the sides. Mr. J & M Machines picture shows the exact way that motor came from the factory, the caps set back from the block.
Ford seen that there was no need to waste babbitt on the sides on the early caps, as it was of no use, and they Quit.
Your center Spec. is Bogus, as evidently you haven't found out yet that Model T cranks very an 1/8th of an inch from one to another when installing in a block.
Maybe some day Kerry!
There you go again Herm, you make it out that they are my specs, NO!!! Fords
At the end of the day, it shows that Canada build a better engine.
are you stating that a bearing with an axial clearance of 1/32" is a radially stiffer bearing than one with 1/16" axial clearance (higher oil pressure per your 6/16 post)?
So long as the hole in the block bearing is supplied with a volume of oil sufficient to keep the well full and the oil groove filled, hydrodynamic action of the oil within the bearing (.002" clearance radially), cares not one whit whether the axial clearance is 1/32" or 1 foot. As soon as the axial clearance exceeds the diametral clearance, the "lift" or relative pressure that the oil attains under operation ceases to exist.
I still think you're reading way too much into Fords specs and imputing an operational advantage or disadvantage on the caps length, when is is simply a manufacturing spec for the piece part
I'm doubting that this will sway you in any way based on the length of two identical threads on this subject, but wanted to make sure that those reading for information would have the benefit of these facts.
From the care and effort you put into your work, I'm sure your engines turn out just fine.
Scott, I'm sure you mean well, but after several years of designing and building pressurised irrigation farm systems, the one thing I never managed to perfect was the ability to push water up hill in a pipe with no sides.
Why haven't ANY engine builders agreed with Frank?
Before you, (or anyone else), harps on further about what Ford "specs." are, back up your arguments by getting a copy of the actual Ford crankshaft blueprint from Ford archives. Copying pages out of some non-Ford published book with cartoon type diagrams does not give your argument the slightest validity. (Neither does your reasoning or your experience watering farmland.)
I'm sorry that this post has turned so controversial as I don't like to be offended or see anyone offended, but if I read the above posts, correctly, I have learned some things that I didn't know. 1. All T blocks and caps that still had usable or at least complete babbitt in them that I have seen, had babbitt around the full circumference around each crank or rod journal, including the sides. 2. Although Ford may have had some sloppy machinists working for him that didn't cut each journal to the same size, I always though it was proper, and standard procedure to cut them all to the same size, although the last T engine that I had rebuilt had a different machined measurement on EACH main and the rod journals, although cut to the same measurement, differed from any of the main specs. The crank was replaced with one cut to equal specs instead of trying to even out the specs on the "messed up" crank. Maybe I reading the information in these posts, incorrectly, but I'm just stating my opinion on whet I think I have gathered from the above posts.
If a model T had an oil pump and there was gauge pressure on that oil system, then perhaps your analogy would make sense.
The only oil "pressure" in a stock T is hydrodynamic pressure created at the exact point of oil riding between two elements with one element rotating. Viscous drag between the two elements and lubricant draws the lubricant into the contact area and if it is of adequate viscosity will create a pressure area of sufficient strength to suspend the one part from the other so long as the diametral clearances are of sufficient intimacy that the bearing does not collapse. So long as there is a constant supply of oil in the reservoir supplanting the oil loss out the ends, this pressure will remain indefinitely during operation (rotation).
BTW, if I wanted to water farm land and had no pipes, I'd scrap the pump and pray for rain, which is precisely what is happening inside a T engine.
Good luck to you on your efforts to persuade folks to your way of thinking. Perhaps it would be an interesting article for the magazine.
Also you would never want the oil to be trapped in a babbit bearing, you want a constant supply of fresh cool oil to cool the bearing. The viscosity of the oil will keep it in the bearing long enough to due its job, leaving before being burned.
I've never stated that the way it is set up by today's machinests that it is a failure, just could be better, and Ford had it right with Dodge, and Ford specs!
David, It's not a question of agreeing with me, I work with 'FORD' specs, the question would be, why is it OK to use a popsicle stick for a feeler gage?
as to your other post, it's still a very leaky pipe with clearances, fresh oil will always be available.
Jerry, it was a FORD publication and specs are available in may other FORD publications over the years.
Terry, you will has a very nice engine that will last you many years.
Scott, I see you have an understanding or how oil works but in a splash system, the clearances are .0005 larger than pump and for no other reason than clutch drag, a lot of you fellows like to use 5W oil, the babbitt will well and truly be dragging it's b-hind on the crank!
My post of yesterday was censored when I made mention of the cartoon style image as not being valid and certainly not useful in building an engine. I further made the point that using that image to prove the way it was supposed to be was questionable due to the lack of rod bolts and nuts.
Both my post and the one that followed were removed.
I have been on this forum since 97 and that has never happened.
I am a certificated aircraft mechanic and fly the engines I overhaul. I know how to read blue prints, table of limits, and assembly clearances. The only mention I have seen to control end play is the third main. I have never seen and Frank has not identified from a Ford drawing an acceptable gap with tolerance for the center or front main.
The censoring is what got me the most however and if being a chapter president didn't require my membership in the America club I would drop it.
To many on here that I have met, I hope to see you down the road. Removing my bookmark to this forum.
Your post is at other one! Still here, this is a different thread.
By Gary Tillstrom on Tuesday, July 01, 2014 - 08:16 am:
That is not a build spec. That is the equivalent of a cartoon and the purpose of that image is other than building an engine. If you're counting on that to prove "the way its supposed to be" I would take issue with the lack of rod bolts and nuts.
....and I agree
Your "cartoon" posting is alive & well here: http://www.mtfca.com/discus/messages/411944/450035.html?1404232631 scroll to the bottom.
There are two message strings on this topic.
Yo Gary, I got caught thinking the same thing.
You can't leave unless they use a bigger whip!
I have learned from you on your aircraft engines.
Same specs are in the Ford service book.
Do the maths Gary, in a perfect world the T engine would have left the production line with.
Front bearing, 2" journal, 1-15/16" cap
center bearing, 2-3/16" journal, 2-1/8" cap
Max settings, all Ford documented sizes
The above of Dans post has the min to max same as the Ford service book. Now it can't be an each end spec for then the block journal would need to be 1/16" smaller, it's a shared measurement just like any other part that has end play or float or heat clearances, piston or thrust face on rear main etc.