Installing Rear Hub On A '40

[philipswanson]

Do you guys recommend installing the rear hub to the tapered spindle with some light oil or grease on the spindle to ease the fit or installing it totally dry?

[V8COOPMAN]

Clean & DRY Only! DD

[oldskool]

needs to be perfectly dry , clean with lacquer thinner or brake cleaner

[philipswanson]

Thanks, that's what I thought. I just wonder why?? It's not like its going to come off because its secured by a nut and cotter key. So what is the logic of it being dry. Just wondering.

[Floyd]

Friction is the answer here. Just like a tapered collett or bit for milling machine or large drill press or even ball joints. The nut is there to keep it together and provide that a force is always keeping it in contact. The keyway adsorbs shock and does transmit part of the load depending on how much "taper friction" is available. Valve grinding paste is good for lapping the hub to the axle shaft to provide a full contact surface. Clean off the grinding compound and clean completely and dry. Assemble and be happy for doing a good job.

[51woodie]

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It has to do with the coefficient of friction. The axle drives the hub through the key, which is exposed to shear force when torque is applied to the axle shaft. The reason for a dry fit, hub to axle, is that the hub is driven up on the taper when the axle nut is tightened, to somewhere around 200 ft/lbs.. The friction is needed to aid in keeping the axle from shearing the key. If the axle/hub was lubed, then friction drops, there is more stress on the key, and a potential for failure. Some people will check the axle/hub fit with machinist blue to confirm there is good contact on the surface area. Don't forget there is a seal (looks like a fiber washer) that fits in the outside end of the hub, before the washer and nut go on.

[philipswanson]

Makes sense, thanks guys!

[19Fordy]

Just as a point of info.
If you don't have that little fibre seal,
you can make one out of an old piece of leather....like a belt.

[Mart]

My understanding is that if working properly, the drive is transmitted by friction between the hub and the shaft. In theory, the key isn't transmitting the drive. So imagine you left the key out. What would you do to make the friction drive work? Well, first of all you would make sure the surfaces are as perfect as possible. It is recommended to lap the hub to the shaft. I have done this myself, it isn't difficult. Then you would assemble it clean and dry. Finally you do the nut up very tight.

Obviously you do use the key, but you need to imagine it is not there. So no oil or grease, or lapping compound, nothing but clean metal to metal contact. And tighten that nut until something goes click.

Mart.

[V8COOPMAN]

Originally Posted by mart

my understanding is that if working properly, the drive is transmitted by friction between the hub and the shaft. In theory, the key isn't transmitting the drive. So imagine you left the key out. What would you do to make the friction drive work? Well, first of all you would make sure the surfaces are as perfect as possible. It is recommended to lap the hub to the shaft. I have done this myself, it isn't difficult. Then you would assemble it clean and dry. Finally you do the nut up very tight.

Obviously you do use the key, but you need to imagine it is not there. So no oil or grease, or lapping compound, nothing but clean metal to metal contact. And tighten that nut until something goes click.

Mart.

Spot-On! DD

[philipswanson]

It is kinda hard to keep the grease out of the bore in the hub since you have to pass the spindle through the freshly packed wheel bearing area. I like to load the bearings plenty and the end of the axle needs to pass through and will get some grease on it. Tried to keep that to a minimum but some gets in I'm sure.

[Mart]

You need to take extra care. make sure the grease is in the bearing, clear it away from the central part. make sure you get an straight shot at it and if you get some on there, take it off, clean the axle and the bore and do it again.

It can be done.

Mart.

[Tim Ayers]

Question and I don't mean to high jack, but it relates to this discussion.

I used NOS axle shafts and they were perfect, shiny metal. I lapped one side, but didn't install the hub. The follow day, it appears to have a coating of the lapping compound on the stub even though I thought I cleaned it off very well.

Besides chemical cleaners, would it be OK to run a 3M pad or Roloc on the stub to clean it? I don't want to do anything that will mess up the taper.

[glennpm]

Clean it off with "lacquer thinner or brake cleaner" (post #3) or acetone.

[Tim Ayers]

Originally Posted by glennpm

Clean it off with "lacquer thinner or brake cleaner" (post #3) or acetone.

I tried brake cleaner and it's not taking off the compound. I'll use a little more elbow grease.

[51woodie]

Tim. In my experience, when a shaft is machined properly, the finish is nice and shiny. Some machinists can get a finish that is mirror like. When two parts are lapped together with compound, the finished surface is "ground" away at the high spots by the lapping compound, leaving a dull surface, similar to the surface of 1000 grit wet paper. An example is lapping valves to their respective seats. The seat of a new valve is nice and shiny, but when the valve is lapped, you will see a dull mark the width of the mating surface on the valve seat. Unless you have some real special compound, I think you have it cleaned with what you have done. IMHO.

[Tim Ayers]

Originally Posted by 51woodie

Tim. In my experience, when a shaft is machined properly, the finish is nice and shiny. Some machinists can get a finish that is mirror like. When two parts are lapped together with compound, the finished surface is "ground" away at the high spots by the lapping compound, leaving a dull surface, similar to the surface of 1000 grit wet paper. An example is lapping valves to their respective seats. The seat of a new valve is nice and shiny, but when the valve is lapped, you will see a dull mark the width of the mating surface on the valve seat. Unless you have some real special compound, I think you have it cleaned with what you have done. IMHO.

OK, I thought about that and I think/hope you are right. It did seem like there was some lapping compound left over. I'll look it over real good before installing the hub.

[philipswanson]

The theory is that if there is any grease or oil left on the spindle, it will reduce the friction between the two and the hub may rotate on the axle and break the key. Has anybody provided evidence of broken keys caused by this or is it just another old Ford myth? With the nut torqued to over 200 pounds, how much slippage could there be with or without a wet or dry axle taper? Have we seen keys break?

[34fordy]

Originally Posted by philipswanson

The theory is that if there is any grease or oil left on the spindle, it will reduce the friction between the two and the hub may rotate on the axle and break the key. Has anybody provided evidence of broken keys caused by this or is it just another old Ford myth? With the nut torqued to over 200 pounds, how much slippage could there be with or without a wet or dry axle taper? Have we seen keys break?

It is termed a "friction fit". Anything between such as oil or grease or ANYTHING,--reduces the friction and will most certainly break the key and probably ruin the axle.

[V8COOPMAN]

Originally Posted by philipswanson

The theory is that if there is any grease or oil left on the spindle, it will reduce the friction between the two and the hub may rotate on the axle and break the key. Has anybody provided evidence of broken keys caused by this or is it just another old Ford myth? Have we seen keys break?

Is this evidence enough? The hub turned on the axle because not nearly tight enough. Rolled the key right over in the slot...destroyed axle. No myths here! It's exactly the same theory that a Morse Taper works on. That key DOES NOT drive the hub! TIGHT for good reason! DD

[Tim Ayers]

Originally Posted by 51woodie

Tim. In my experience, when a shaft is machined properly, the finish is nice and shiny. Some machinists can get a finish that is mirror like. When two parts are lapped together with compound, the finished surface is "ground" away at the high spots by the lapping compound, leaving a dull surface, similar to the surface of 1000 grit wet paper. An example is lapping valves to their respective seats. The seat of a new valve is nice and shiny, but when the valve is lapped, you will see a dull mark the width of the mating surface on the valve seat. Unless you have some real special compound, I think you have it cleaned with what you have done. IMHO.

Well, it was exactly 51 Woodie described. The axle was perfect shiny metal and, after real close inspection, the lapping compound took the sheen off. I got it really clean and should be good to go.

[JSeery]

How taper fits work is not related to Ford. Taper connections are used in a lot of applications and require surfaces that match well and are clean.

[Floyd]

All well said. Now lets throw some numbers on here. Dig out your slide rule and lets go.
As to the key , 1/4 X1/4 X approx. 2.8 ", using typical AISI 1018 material, we get a possible max torque transmission of 540 ft-lbs. per axle side,
A good flathead can make about 185 ft-lbs torque max. Using a low 4:11 rear end, the most that could be seen at the axles would be 760 ft-lbs total. The differential action has to be taken in consideration. This assumes everything is perfect. Real world reduces these numbers by 20 to 50%
Now to the tapered axle and hub. At 250 ft-lbs torque on the axle nut, clean and lapped smooth finish on axle and hub we can get possibly 690 ft-lbs of torque carrying capacity per axle side.
Lets say the differential divides the torque equally, no LSD here, we have a max torque at each axle shaft of 760 / 2 = 380 ft-lbs of torque twisting the axle shaft.
The keyway can handle 540 ft-lbs of torque under ideal conditions which means a perfect fit in the slot of the axle and no fretting, shock loading or fatique etc. If we add in a little safety factor ,1.8, this comes out to a design torque value of 300 ft lbs. which less than and too close to the engine value of 380ft lbs. The key will not do the job alone. See picture above.
As to the self locking taper fit of the axle and hub, which can withstand 690 ft lbs of torque. The engine value of 380 ft-lbs is well within the design limits if everything is perfect. However if a hub is removed for brake work and not reinstalled correctly, say only 150 ft-lbs are applied to the nut, then we can only transmit about 400 ft lbs of torque which is too close to the 380 ft lbs we can see from the engine. Real world conditions can change these numbers drastically and in the wrong direction.
A perfectly assembled taper fit hub and axle will work by itself . A Poorly maintained and set up taper assembly can be prone to failure.
A keyway alone system will barely work in ideal conditions. Poor conditions and it will always fail.
The combination of the taper fit and the keyway and correct axle nut torque is what keeps us safe out on the highway. Its all done with numbers, the Ford guys had good slide rules, we need to use good tools.
My opinion and calcs.

[JSeery]

When abusing Ford banjo rear ends the axle should brake or twist before a properly installed hub would turn on the axle.

[philipswanson]

Thanks for all the great information! Good discussion.

[V8COOPMAN]

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Originally Posted by Floyd

The keyway can handle 540 ft-lbs of torque under ideal conditions which means a perfect fit in the slot of the axle and no fretting, shock loading or fatique etc. The key will not do the job alone. See picture above.

A keyway alone system will barely work in ideal conditions. Poor conditions and it will always fail.
The taper fit and correct axle nut torque is what keeps us safe out on the highway.

I know that Floyd spent some meaningful time calculating all those forces. Without re-running his math, I have no reason to doubt that he is at least "in the ballpark", if not spot-on.


I have no desire, nor the physical stamina any more to take-on an almost dumb "Mr. Wizard-like" project, but it would be damned interesting if SOMEONE here on the forum could be convinced to play along and partake in an experiment to remove the KEY from the keyways on the tapered axles on a pre-1949 Ford vehicle. Said 'SOMEONE' would of course replace the drums/hubs, and torque the big nut to the roughly 205-ish ft. lbs. factory figure. Then, a reasonable test drive would follow, not driving like a demented hot rodder, but a normal drive of a mile or two. Return home, remove both big nuts and determine whether or not the hubs had remained tight and in line with their original clocking. I'd be willing to bet a "fifth", purchased tomorrow the 3rd, that a drive on the 4th would prove that the hubs would not slip....more or less convincing folks, for once and for all, that the KEY in the keyway is NOT what drives the hub/wheels/tires.


I believe that there is ONLY ONE person on this forum that MIGHT POSSIBLY be game-enough to undertake this nutty experiment. With that, I wonder if our friend Mart would be up for this challenge with his ol' white pick-up? Surely SOMEONE here must be curious! Mart? Anyone? DD

[Mart]

I'm laughing here, but you did say not like a demented hot rodder...

[Tim Ayers]

I second your Mart nomination. I would think that it would. It is amazing how tight they are on when I'm just placing them on hand tight doing the brakes.

[philipswanson]

Hey if friction between the hub and spindle is what we want, why not use some red Loctite on the spindle for added insurance?

[V8COOPMAN]

Originally Posted by philipswanson

Hey if friction between the hub and spindle is what we want, why not use some red Loctite on the spindle for added insurance?

C'mon, Philip! There's a huge difference between 'friction' and gluing. I believe that the last 90 PLUS years that Fords have been operating with tapered axles and hubs this way should prove that if ya precisely follow Ford's original, printed installation procedures, you won't need "added insurance". Those hubs are difficult-enough to remove as it is (when properly installed). Try to imagine attempting to remove one after some bozo has glued it on. But what the heck do I know?


Can we assume you finally had a successful mating of the shaft into the U-joint? I hadn't heard-back whether or not you finally won that battle. DD

[Floyd]

I will "sixth" the motion that we get the fifth for the fourth and do it on the third.. Make mine Russell's Reserve as I know Jimmy.
Keyways are not efficient and have the load concentrated on only one side. However they are good for limited power transmission like pulleys on straight shafts like your table saw, PTO, band saw, etc. If you want to transmit a lot of power and still have a sliding type assembly fit, you use multiple "keyways" which are then called "splines". Think transmission input and output shafts.
If you want to perfectly align something to a shaft, like a hub for a wheel, you cannot do it with just a sliding fit. The taper joint provides this true alignment IF made correctly. Also the efficiency of the geometry of the correct taper makes it self locking and provides terrific forces that can be used for transmitting power.
Fun fact- If properly made and assembled and tightened, the force to remove the hub will be 13 tons.
Drink up, be safe!

[philipswanson]

Originally Posted by V8COOPMAN

Can we assume you finally had a successful mating of the shaft into the U-joint? I hadn't heard-back whether or not you finally won that battle. DD

Yes but I had to remove one end of the spring first. The wagon spring has extra leaves and it hits the cross member when going in assembled. After that she slipped right in on the second try. I will be putting the Columbia controls in next. Thanks, Phil

[Kube]

I can tell you I had run a lathe with a 6', yeah SIX FOOT swing. The tooling was held in with nothing but taper collets. There were times I'd be taking 3/8" off at a pass.
A properly mated taper is more than enough to handle anything even the strongest flathead can dish out.

[Floyd]

I was waiting for your reply. As a tool and die maker, you have depended on taper fits for every hour of every day that you worked. That is a lot of experience. The good news is that in the tool room you got to enjoy correctly done taper assemblies.

[Kube]

Originally Posted by Floyd

I was waiting for your reply. As a tool and die maker, you have depended on taper fits for every hour of every day that you worked. That is a lot of experience. The good news is that in the tool room you got to enjoy correctly done taper assemblies.

I really enjoyed my career. Best of both worlds for me. I was able to use my hands and my brain. It was nearly always interesting.
Plus, I was actually paid to make things perfect!

That huge lathe I'd mentioned previously was a tad intimidating. I was quite amazed at the chips I was able to remove without the machine giving as much of a grunt.

[40 Deluxe]

Originally Posted by Floyd

All well said. Now lets throw some numbers on here. Dig out your slide rule and lets go.
As to the key , 1/4 X1/4 X approx. 2.8 ", using typical AISI 1018 material, we get a possible max torque transmission of 540 ft-lbs. per axle side,
A good flathead can make about 185 ft-lbs torque max. Using a low 4:11 rear end, the most that could be seen at the axles would be 760 ft-lbs total. The differential action has to be taken in consideration. This assumes everything is perfect. Real world reduces these numbers by 20 to 50%
Now to the tapered axle and hub. At 250 ft-lbs torque on the axle nut, clean and lapped smooth finish on axle and hub we can get possibly 690 ft-lbs of torque carrying capacity per axle side.
Lets say the differential divides the torque equally, no LSD here, we have a max torque at each axle shaft of 760 / 2 = 380 ft-lbs of torque twisting the axle shaft.
The keyway can handle 540 ft-lbs of torque under ideal conditions which means a perfect fit in the slot of the axle and no fretting, shock loading or fatique etc. If we add in a little safety factor ,1.8, this comes out to a design torque value of 300 ft lbs. which less than and too close to the engine value of 380ft lbs. The key will not do the job alone. See picture above.
As to the self locking taper fit of the axle and hub, which can withstand 690 ft lbs of torque. The engine value of 380 ft-lbs is well within the design limits if everything is perfect. However if a hub is removed for brake work and not reinstalled correctly, say only 150 ft-lbs are applied to the nut, then we can only transmit about 400 ft lbs of torque which is too close to the 380 ft lbs we can see from the engine. Real world conditions can change these numbers drastically and in the wrong direction.
A perfectly assembled taper fit hub and axle will work by itself . A Poorly maintained and set up taper assembly can be prone to failure.
A keyway alone system will barely work in ideal conditions. Poor conditions and it will always fail.
The combination of the taper fit and the keyway and correct axle nut torque is what keeps us safe out on the highway. Its all done with numbers, the Ford guys had good slide rules, we need to use good tools.
My opinion and calcs.

Hmm. I don't see the trans. low gear ratio figured in. I used 2.82 as the first gear ratio and came up with a total of 2144 ft. lbs. of torque to divide between the the two axles (minus drivetrain losses-say 20%) so 1700 divided by 2 equals about 850 ft. lbs. max. per axle in first gear.

So from the numbers presented here, it looks like the taper fit alone is not enough! (At least not when the clutch is popped at max RPM in first gear!)

[Aarongriffey]

But Coop, some guys think the rear axle nut is supposed to be tightened just to the point of touching the hub. They think it is like the front wheel bearing nut.
I’ve had guys jump all over the place when the say me tighten that nut.
When that happens I ask them about the nut that holds the steering wheel on.
To prove that the friction will drive the hub just fine a friend of mine bought a ‘26 model T touring and it drove just fine with no axle keys.

[cas3]

i have been waiting for someone to bring up machinist tapers into play, thanks kube for that. jacobs tapers on my r8 mill collets to hold on the drill chuck stay in place without spinning, and without a 200lb torque nut holding it together...just the precise taper fit, never falls apart. well...maybe when too lazy to change collets and try to mill with a drill chuck...but we dont have to go into that, and not mentioning any names here either

[cas3]

to add to Aarons post, every car i have ever owned with tapered axles, many brands, the hubs were loose when i bought it

[cadillac512]

Originally Posted by 40 Deluxe

Hmm. I don't see the trans. low gear ratio figured in. I used 2.82 as the first gear ratio and came up with a total of 2144 ft. lbs. of torque to divide between the the two axles (minus drivetrain losses-say 20%) so 1700 divided by 2 equals about 850 ft. lbs. max. per axle in first gear.

So from the numbers presented here, it looks like the taper fit alone is not enough! (At least not when the clutch is popped at max RPM in first gear!)

Correct! I've built rear axle assemblies for drag cars and that's the way to choose what axle strength is required for a particular engine/trans/torque level/gear ratio. That first gear ratio is a very important factor.


Terry

[russcc]

That was a great thread. Thank you Fordbarners. I have been doing it wrong, but now know hoe to remedy the situation.

[V8COOPMAN]

Originally Posted by 40 Deluxe

Hmm. I don't see the trans. low gear ratio figured in. I used 2.82 as the first gear ratio and came up with a total of 2144 ft. lbs. of torque to divide between the the two axles (minus drivetrain losses-say 20%) so 1700 divided by 2 equals about 850 ft. lbs. max. per axle in first gear.

So from the numbers presented here, it looks like the taper fit alone is not enough! (At least not when the clutch is popped at max RPM in first gear!)

Originally Posted by cadillac512

Correct! I've built rear axle assemblies for drag cars and that's the way to choose what axle strength is required for a particular engine/trans/torque level/gear ratio. That first gear ratio is a very important factor.
Terry

Guys....You're both absolutely correct...you must use 1st gear as the deal-breaking factor when multiplied by rear end ratio for overall torque computations. But I have to disagree (within reason) with the statement about TAPER fit ALONE not being enough to hold the axle firmly with the hub. Think about it....99-3/4% of us morons that drove one of these old Fords before reaching the legal drinking age has revved it up and side-stepped that left pedal in 1st gear. Many of us even got away with it more than once and laid-down a skinny black patch long enough to make those girls on the corner giggle and shake their heads. But Henry's boys didn't really design-in a redundancy factor meant to protect Billy Bad-ace from unconditional poor judgement, and that next time or two would leave ya with a requisite trip to the junk yard for a $10 trans or a $20 rear end with a GOOD ring and pinion or spider gears, and a few hours underneath replacing such. My point here is that the old Ford drive trains weren't built for continued abuse, but SOMETIMES when the planets were aligned just right, and when those big nuts were tightened correctly, those old tapered axles spun those hubs like there was no tomorrow.......until the one time when everything just went south! DD

[cadillac512]

So no amount of fool-proofing will overcome the efforts of a sufficiently motivated fool? Darn...

[Floyd]

This has been fun stuff. At least we got some people thinking which is a good thing. And yes to 40 Deluxe, your trans point is well taken and does affect the numbers. The actual limiting element in this exercise is the traction of tire to road. At approx. 560 ft-lbf at the axle(per side) the wheel will spin the tires IF the car is not allowed to accelerate, i.e. pushed up against a wall. Otherwise most of the force goes into accelerating the car. A whole notha set of calculations, but we just want to go fast (and stay safe with tight axles)
Fun session and yes Cadillac512, we will not be able to foolproof our way past all of the fools.

[cadillac512]

And thanks for the math,Floyd. It's good stuff,and as I've always said: It's Math,not Magic!



Terry