Full float rearends
 

Does anyone know of any reason NOT to run a full float 9" style rear end in a street car? My 69 camaro is set up for road race/street and FF axles seem to be the best way to go. I don't think anyone makes a bolt in version, though, so I guess I'd have to weld on mounts for myself.

I cant think of one. Then again... I have been putting them into street cars for quite some time now.

Yes there is a bolt in version for the first Gen F-body. Its not your typical GN hub or wide five set-up... but it actually uses a bearing cartirdge from a late model GM chassis.

As for the perches, I am sure that they could be installed in the stock location... at the stock 4* angle... or, they could be left loose for the end user to set the angle to their peticular driveline package. Which is what I would recommend for most.

Chicane- who makes the rear you're talking about? I'd like to keep the 4 3/4" bolt circle and as close to stock width as possible. I think Moser makes something that may work, but not bolt in. I have no problem welding on the mounts myself if I need to. Thanks.

That would be me.

It starts off with a Ford Motorsport HD fabricated kit housing, 4130 tubes and 4340 (or 300M) axleshafts. It maintains the 4.75" bolt circle... as it utilizes the Corvette C5/6 wheel bearing cartridge.

The housing and axles can be made to fit any width, at the time of manufacture, and the leaf perches can be welded or left loose for the end user.

:willy: Moser :willy: ... now that is a scarry thought.

To All:

Are there a number of semi-floating rear ends Breaking Axles while being used in PT Cars?

Drag Racing with 800+ HP maybe.

I guess I'm not following why go to a full floating rear end for street or track use with <600 RWHP?

With a good housing from Strange or Moser and Quality 31 splined Axles, are you in danger of breaking an axle even on a road race track with our cars?

Even, "Hard" driving requires the driver to be smooth as not to disrupt the balance of the car.

Help me, what am I missing, other than getting one for the coolness factor?

Sincerely,

Ty O'Neal

Ty,

It's really only partially an axle strength issue. The horespower transmitting capability is not at all at issue. It has to do with the bending loads high "G" cornering exerts on the axle at the bearing. The Bearing (Bearings, there are 2) are much larger on the floater hopusing. This gives you the strength and longevity for those high speed, high "G" turns. It also gives you the benefit of changing center sections without having to pull the wheels off. (Assuming no center caps on the track) Pop the axle covers off, pull the axles and away you go. Circle track guys use floaters almost exclusively. Check Coleman, Stock Car Products, Winters, Franklin to name a few for applications. They can be made any length or offset. The down side is, I don't think anybody is making a street brake "Kit" for them at this point. Could be wrong. You will probably have to build your own "Kit". Hope this helps.

I'm going to pull the n00b card here and ask if someone can explain what a full float rear end is, vs. other types. I'm still learning here.

are these available already? and do you have pricing. I will be in the market for a rear for my nova in the coming months and you have my attn:

A full floater, is a rear end that has axles that only transmit torque, The lateral loads on the wheels are transmitted to the two conical roller barings on the Hub... much like spindle on a rwd car.. except the spindle i shollow.. and the axle protrudes thru it and connects the axle to the hub via a driveflange..

the idea is that since no bending losda are being put on the axle it can handle more HP for a given weight.. and is you should break an axle the wheel will stay on (and of course the fact that it olny requires pulling the axles out a couple of inches to change centersextion.... without removing the wheel, or calipers to remove the discs...
http://www.mittlerbros.com/images/20...mplete_kit.jpg
cool huh?

So essentially you have the wheel on a separate bearing that it freely rotates on, and the axle comes inside and spins it, but is not holding the wheel to the hub, correct? So the wheel isn't pulling on the drive axle at all. That is cool!

exactly!

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Chad:

Has anyone that you know of ever broken an axle with a PT Car where a full floating axle would have made the difference?

To the best of your knowledge does anyone on this board drive their cars hard enough to justify the expense?

Circle Track Cars, Stock Car Racing etc. are always loaded to one side of the car. I can understand why this would make a difference over 500 miles, especially if they are basically loaded continuously over the length of the race.

Now if changing the rear pumpkin was a necessity, I would understand as putting the exact "Best" gearing is important enough to make a difference.

I know a fair amount of the Bonneville Car use them for that reason. (It sure wouldn't be because of side loading):D

Anyway thanks for responding, I look foward to your imput on these questions.

Ty

Ty,

I really can't answer your first question as I am just entering the PT world myself.

As far as I can tell there are alot of people on this board that drive their cars hard, that is one of the reasons I like this community so much. Alot of people talk, but not many back up what they say. As far as expense, it is not all that different. Maybe 2-3 hundred bucks. As I said the issue is brake kits, i don't know of any street kits with parking brakes.

Your third comment is only partially true. I never dealt with 500 mile races. I was involved with asphalt short track racing on .5 mile paved ovals. Most of these races were between 25 and 50 laps. In these short races I have absolutely seen Moser, Strange etc. axles break due to the side loads. I don't have personal experience yet, but i would think that on most road coarses during the length of a race or hot lapping you could achieve a similar number of cycles with the amount of turns on the coarse.

As far as quick third member changes, you could look at this in several ways. You may not need changes for a particular track, but you would make it easy on yourself to say change from a road trip gear to a track gear to a drag strip gear. Althought any rear with a drop out third member can accomodate this somewhat easily the floater adds to the ease.

I would absolutely run a floater at Bonneville. If for nothing else I keep all for wheels even with a broken axle. That's key! LOL

All this being said, we did not put a floater in our truck project. While we are building it with the PT style, my Dad will see very little if any real track time with it. So the massive amount of choices in brake packages lead us to use a standard 9" custom built.

Later

As do Ford-style bearings and disc brakes.

I fully understand the need for a full-floater setup, but not in our application. Most people here don't really run their cars that hard in comparison to competition applications. Most cars here wouldn't peak 1.5g in a road course, nor do they sustain high lateral loads for very long. The ONLY time I've seen a axle break at the flange was an off-road rig using stock 30 year old axles.

I think the only reason why I'd do it so I can run some crowned axles and -1 degree camber. I'll save the weight and put the cash somewhere else. Does this mean we should run 15" wheels too?

Oh no you didn't!

All good information Matt. I wasn't even going to go down the cambered rear avenue at this point. This is a great thread. I have met alot of people with alot of know how that don't know what a floater rear is. By the way our 9" is hung from one of your tri-angulated 4 links.

i have seen that the full floaters can be ordered with up to 1.5 deg negative camber... doesnt that put alot of wear on th ecrowned axle and on the drive plate?? i mean there are no CV joints in there... just a splines axle that is 1.5 degrees off in allignment??

fabricating some brackets for a corvette caliper shouldnt be rocket science, and if the cambered rears dont wear like a mo-fo it would be cool to run a cambered one just for some added lateral grip

but how much camber then?? .5 or 1 degree? and should one run alittle toe as well to make the tires wear even??

I almost shot water through my nose! Glad you took it with humor, that's how I meant it. Hope that tri 4-bar works well for you. It sure has for us!

Deuce, it does put some wear on the splines...don't expect tens of thousands of miles of use out of them. But it isn't bad. In fact, non-crowned axles can run up to 3/4 degree without excessive wear. I wish I could quantify "excessive", but I can't. If I were to do it (and I'd love to), I'd run a 1/2 degree to be safe. It's tough to do, though.

whats tough??

It's tough to bend the tubes accurately while maintaining that angle with respect to the necessary pinion angle.

...and if you ever change the pinion angle down the road you just introduced some toe into the picture-- which will become additional roll steer. And hopefully you don't find out that it's roll oversteer, especially during a situation when you least expected it. :willy:

I'd love to hear from someone who has driven a cambered rear end on a leaf spring car... I can imagine as you get on and off the throttle and pinion angle changes and things change from toe in to toe out it might get a little exciting. :)

I know alot of us (myself included) my not really NEED a floater, but if the cost difference is only a couple hundred bucks on top of about 3 grand, then why not? It is without a doubt a superior design, right? Whats wrong with a little overkill, especially in the drivetrain? Is there any application out there where semi floaters are better?

That's why not, IMO. How much more do you want to spend? A good set of 31-spline axles with 3.150" bearings is somewhat overkill for most of us.

I'd be willing to bet a SF axle is slightly lighter, both in unsprung and rotating mass. AND you have all the brake kits you want that will bolt on.

With that mentality, you might was well go for a 4" driveshaft. But it's only money.

It just seems to me that a little extra insurance toward drivetrain strength would be more of an investment than a waste of money. Besides, look at the money most of us spend on our cars- a couple hundred bucks is barely felt. (price a good paintjob lately?) I think I'd rather put it toward a stronger axle than chrome. But now you've got me thinking about a 4" driveshaft! Maybe not.

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The Bearing you mentioned. Is that the Big Ford Bearing you are referring to?

I've got the Strange Center section and housing, Their 31 splined Axles, Tru-Trac, and it uses the large Ford End Bearings.

From what has been explained to me from Mark Magers, and what I have read since read. This set up is plenty more than enough for a PT car that gets lots of Track time.

That's why I wasn't so keen of the full floater, unless you just want one, and Lord knows I certainly have made similiar decisions from time to time.

Take Care,

Ty

Yes it is. Specifically the tapered style bearing.

LOL! However some of us guys with long single driveshafts actually did the math and found out that a 4" driveshaft was necessary to keep a comfortable margin away from hitting the critical speed of the shaft at the speeds the car can and occasionally attains. Might as well spec all your parts to be safe at the maximum operating capability of the vehicle!

With my combination I found that I was within 150 rpm of the critical speed of a Mark Williams 3.5" aluminum driveshaft at the top of 4th gear, which I do hit every now and again. 150rpm is NOT a comfortable "safety margin" for me especially when it comes to something like critical speed which can and does have very dangerous consequences. A 3.5" Aluminum MMC shaft had about a 700rpm margin, and a 4" aluminum shaft had about a 850 rpm margin. The prices were all very similar so I chose what would give me the biggest margin of safety.

That comment was within the context of this discussion, which is using equipment that isn't necessary for a particular application and is only purchased for a "cool factor" or otherwise (something other than a "need" basis).

If you NEED a 4" driveshaft, then you don't have a choice. Same goes for a FF axle. If you DON'T need a 4" shaft, than what's the point? You'll just spend more money on something that is oversized. Bigger isn't always better.

Perhaps I'm too anal about efficiency. I guess that's why I do what I do. Sure, every part should not be sized such that no margin of error exists, but the FOS designed into every part should reasonable enough to allow for unusual loads and situations, but not so much that excess weight and bulk degrades vehicle performance.

I think you will have great success with that rear. From my past and the research I did we ended up with the same thing. Although I had the housing built locally.

Later,

Nah, you just sound like a mechanical engineer. So am I... and I agree with you 100%. :P

Make that 3. So am I and I agree as well.

x 4!

also mechanical engineer... and im getting a track9 from sc&c... although im leaning towards an aluminum williams centersection with GM12 bolt ring and pinion and 33 spline axles.. ..partly just to be different and partly to reduce loss..

We went with the Strange aluminum center with a street aluminum daytona pinion bearing carrier and 31 spline Tru-Track with 3:89 gears. It looks really good and saves a bit of weight. We had a smooth back center housing mated to 3' axle tubes and Big Ford bearing ends. Add that to 31 Spline Moser axles and there you have it. Should be nice.

Which semi-float housing ends (if purchasing an aftermarket housing) allow for tapered bearings, and how do you set the preload? Most of the SF aftermarket stuff I have seen uses the "cartridge ball" style which is not intended for alot of side loading. Thanks for everyone's input!

Yes.


Save weight by... ?? Id love to hear your thoughts on this subject.




It would depend on the design. If you are referencing the typical BGN or wide five... Id say yes. But not with a cartridge bearing/sensor design... its less than half the rotational mass of a BGN/W5.

As for the subject of a 4" driveshaft... some of us need a 4" driveshaft because of the shaft speeds that we deal with. Safety and durability outweight the cost everytime.

Besides... $3k for something that will not break or that you will not have to fix or rebuild constantly... is a better mentality than a $10k paint job.



If it were of any choice, I would be looking into the components from Mark Williams. Their 57/58, 66/67/68 series housing ends all use tapered rollers. But for what its worth... the typical 'Ford big bearing' ends are too large for 99% of the applications outside of drag racing. As are differential cases that have bearing registers larger than that of 3.062". Bearings... are subject to the very same limitations concerning critical speed. Most here will never see those limitations... but then again... there are those of us that do.

About the pre-load of tapered bearings... the difference in the bearing cup depth and the retainer plate is how this is accomplished. With the bearing pressed onto the axleshaft and inserted into the cup, the amount of the bearing race that protrudes past the end of the bearing cup (along with the axle seal) is clamped into the bearing cup with the loading of the retainer plate to the housing end.



If thought out well enough... you can build a stronger, more reliable, more efficient and lighter differential for well under $3... even while using a 9" type design. Although the the 9" is typically 3% less efficient... you can get that back and even a little more by choosing the right components.

:cheers:

Chicane,

I am curious and would like to know a bit more about the SF taper roller bearing design. My question is, Is measuring the delta of the cup to cone the only way the "pre-load" is verified? We used quite a few tapered rollers in mass transit gear boxes and found through hours and hours of testing that we could not use this type of check to verify the proper initial clearance. Due to manufacturing tolerances of the cup to cone it was found that we needed to develop fixturing to measure the axial and radial clearance values. Based on those values and testing, a matrix was developed to determine the proper clearance for the application. I guess that brings me to a second question, you refered to pre-load. Our tapered rollers were always set with some amount of clearance, is "pre-load" just a generic term being used here? Thanks for any information you can provide.

Sorry to all the others for the book, but I'm curious.

Later,

Instead of falling suspect to any speculation I have called upon our resident bearing specialist... CarlC to address this subject. Hopefully he will reply shortly.

CC- Yes... that term being used is rather generic. But... Ill take a stab at a simple explaination as I under stand it.

Bearings with a tapered geometry, can be difficult to directly measure radial clearances. For this reason, radial clearances are commonly converted to axial clearances. (Radial clearance equals axial clearance times the cotangent of the bearing contact angle.)

The amount of clearance between bearing rollers and raceways measured in this axial direction is called endplay. The optimal initial endplay depends on a number of factors, including shaft and housing materials, bearing fits, and operating temperatures.

With this, endplay adjustments in tapered roller bearings are made during assembly or installation to compensate for the expected thermal expansion during operation and system deflections. Axial preload in tapered roller bearings is produced by displacing one bearing ring axially in relation to the other by an amount corresponding to the desired preload force. Generally, each bearing is individually and manually adjusted using shims or spacer sleeves, or by tightening torques from means likend to the bearing retainer.

In addition to manual methods, there are also several automated techniques. In the case of double-row tapered roller bearings, a preset assembly can be supplied, or the bearings can be adjusted manually at assembly by machining spacers.

Careful monitoring and observation of applications can sometimes reveal early warning signs of clearance and endplay-related problems. Vibration monitoring equipment, for example, can detect the excessive axial and radial shaft movements caused by too much endplay. Temperature sensors can detect-increases in heat associated with impending bearing failure. This may also be accomplished by reading the surface condition that may provide a picture of what the failure mode is... radially spalling, micro spalling, impact deformations etc etc.

CarlC... take it away.

Re-read my post:

Don't need... and did not need to re-read your post. I read your comment's correctly the first time.

My reply was to educate the rest of the forum members that don't know any better and/or that do not understand shaft specifics. Even comments in generalization can mis-lead or mis-represent the point trying to be conveyed. :)

My original question was if a FF axle can be used on the street, because I have never seen one on the street, and the answer was yes (thanks chicane). I may not NEED one now, but the direction my car is heading, I will most likely NEED one later. I will spend the extra few hundred now rather than a few thousand twice.

Tom's on it.

Preload can be + or -. Often in the bearing industry, but mostly related to machine tool spindle bearings, clearance will be referred to as negative preload.

Due to the nature of the beast tapers are set using an axial endplay (bench endplay) value. On horizontal applications it can be a real bear to get the BEP set correctly since gravity is not your friend. On larger assemblies it is recommended to set the BEP in a vertical fixture. Trying to measure radially usually does not have good results due to trying to keep the system aligned, off-center housing mass loads, no access to both sides of the shaft, multi-piece rings, etc. It can be a very time consuming and arduous process.

Smaller TRB's like those used as discussed are great for the do-it-yourself'er since the preload is built in. There are very few self-contained TRB assemblies like these anywhere in the industrial field. I like them, and have proved very reliable for me.