Contemporary Cobra Watts Linkage

[mickmate]

I got a piece of billet a tapered reamer and a rotary table for the milling machine to start making the conical shape of the watts brackets to fit Jag hubs. Then I went back in the thread and found the simple and effective solution that is perfectly suited to my cutting table. The hubs you show are a lot more friendly to mount brackets to but I wouldn't change to inboard brakes if there was a choice. I have found it easier to drop the whole rear end to service Jag brakes, and that was when it was fitted in a Jag. Some good ideas and discussion keeps us all thinking though.

[Dazecars]

Originally Posted by mickmate

The hubs you show are a lot more friendly to mount brackets to but I wouldn't change to inboard brakes if there was a choice. I have found it easier to drop the whole rear end to service Jag brakes, and that was when it was fitted in a Jag. Some good ideas and discussion keeps us all thinking though.

I am not doing a very good job of communicating my idea Yes the hubs I pictured are normally used to convert the brakes from in board to outboard, but my thought is keep the inboard discs. You have to run a rotors thick spacer between the diff and the half shaft any way so put the rotors there and run the inboard discs as normal. My thought was just to use the newer hubs for the sole purpose of having OEM mounting locations on the hub that were designed from the factory to handle that kind of pressure. mickmate, like I said before, I think your design is fantastic and the 3/8" hub material should be strong enough, I just like to think outside of the box and look at other options so I figured I would bring it up to see what people thought.

[mickmate]

I understand what you're suggesting and it would be a good use of existing bracketry. First Cobras used inboard discs but they were moved outboard due to overheating and poor serviceability.

[Dazecars]

I am a dork, I read through what you had written and I realized you were saying, if you had outboard disc hubs you would run outboard discs. Sorry Do you have an ETA or idea of $$ when you will be ready to sell

[PDUB]

Seems as though I read about an outboard brake conversion for the jag based on newer jag parts that were interchangeable from another newer model... I think it was from the jag lovers site, but I can't quite remember. Anyone else ever see that? What was it?

[mickmate]

I think one of our CCX guys is putting that on his car now with XJ40 parts. After the prototype worked so well I'm working on another batch and will have prices within a couple of weeks.

[Dazecars]

Originally Posted by PDUB

Seems as though I read about an outboard brake conversion for the jag based on newer jag parts that were interchangeable from another newer model... I think it was from the jag lovers site, but I can't quite remember. Anyone else ever see that? What was it?

any modern Hub from the XJ40 through the X300 and X308 will work. The hibs are the same on all those cars, but the calipers and rotors for the XJ40 are designed for solid rotors similar to the ones found inboard. The X300 and X308 rotors are vented for better cooling and need a bigger caliper.

As far as other parts, if it is an XJ40 you only need the stub axle as the XJ40 and older rears use the same u-joint. If you get an X300/308 stub axle you will need the entire half shaft as the u-joints are different. Other than that the only other difference is the diamiter of the hub to wishbone pin. As was mentioned already in this thread you either need to sleeve the wishbones and use the newer pin or use different bearings and the older pin. The difference in pin size is only .05" and the newer type pin rides in a sleeve that fits in the hub bearings so a person could probably have that sleeve machined out to accept the older stile pin. The other option and the one I will be doing is I am machining som UHMW bushings to replace the bearings. they will fit in to the newer hub and accept the larger stile pin. here are some pictures I took of some XJ6 parts compared to my X308 parts

Here is the modern hub with a bolt pattern adapter



Here is the hubs side by side





here is the half shafts, old and new



new hub on an old wishbone




I have researched this a lot, please let me know if I can help further

[PDUB]

Thanks for the info Daze... the newer stub axle looks pretty whimpy! Is it up to high HP applications? Looks like they changed the splines on it... or am I missing something? I'll send a PM for more info. Thanks again.

[cobrarkc]

Originally Posted by PDUB

Thanks for the info Daze... the newer stub axle looks pretty whimpy! Is it up to high HP applications? Looks like they changed the splines on it... or am I missing something? I'll send a PM for more info. Thanks again.

You can still use the old stub axle by using a combiation u-joint. 1410 to 1350 and don't worry about the smaller 1350 u-joint they can handle up to 1000hp. This is where i got mine, even though they don't have it listed, ask them they have them.
http://www.dennysdriveshaft.com/c130...al_joints.html
Most u-joint places can get them for you.

[Dazecars]

Originally Posted by PDUB

Thanks for the info Daze... the newer stub axle looks pretty whimpy! Is it up to high HP applications? Looks like they changed the splines on it... or am I missing something? I'll send a PM for more info. Thanks again.

If you look at the two stub axles, old and new, the splined sections are about the same diameter, and that is where the torque is transferred to the wheel flange. With that in mind the newer stub axles have more splines which should make them stronger than the older Jag stubs.... make sense??

[PDUB]

Originally Posted by Dazecars

If you look at the two stub axles, old and new, the splined sections are about the same diameter, and that is where the torque is transferred to the wheel flange. With that in mind the newer stub axles have more splines which should make them stronger than the older Jag stubs.... make sense??

The new splined section looks much sorter, and the splines look like they might strip out with any sort of wear, i.e. the surface area in which they mate to the hub looks whimpier. The old one looks like the input shaft on a toploader... that is pretty tough!

I'm not an ME, so I cannot say for sure, but it just looks weaker to me. I would love to hear from an expert, since I am interested in persuing the outboard brakes...

Cobrarkc, did you go with the outboard system?

[Dazecars]

I too am not a ME. I am sure the shorter splined section will reduce strength, but as fas as the splines them selves, lots of fine splines will always be way stronger than fewer heavy ones. its like a fine thread bolt vrs a course thread bolt, or a 19 spline axle vrs a 30 spline axle.

[Ralphy]

Originally Posted by Dazecars

I too am not a ME. I am sure the shorter splined section will reduce strength, but as fas as the splines them selves, lots of fine splines will always be way stronger than fewer heavy ones. its like a fine thread bolt vrs a course thread bolt, or a 19 spline axle vrs a 30 spline axle.

I did the math once years ago on a fine vs. course thread. Thinking the surface area was maybe close to the same in area. However because the surface or depth was less. The solid section of the bolt minus the thread is greater making the area stronger. Plus resists backing off better. A fine threaded bolt is better, unless it is in an area where the nut is continually taken on and off.

[PDUB]

Originally Posted by Ralphy

A fine threaded bolt is better, unless it is in an area where the nut is continually taken on and off.

Is this due to wear? Does that mean the smaller spline would be more likely to wear faster with the fore and aft torque of the drive line?

[Ralphy]

Originally Posted by PDUB

Is this due to wear? Does that mean the smaller spline would be more likely to wear faster with the fore and aft torque of the drive line?

PDUB, We use a lot of fixtures at work. What I have seen is a chance of pulling threads out with continual use, bolt in bolt out. A splined shaft has a large surface area vs. fasteners I would not think you would see wear on a shaft vs. a bolt. I would not worry.

Helicoils work even better!

[Ralphy]

Nick,

Looking at one of your pics, it seems this setup would be worthless without the watts? Those two horizontal links would be all over the place and sheer the bolts! Anyhow, would you think the lowers would work just as well with a tube and heim joints? Now one step further, could it work with one shock up front only?

What I do see in your photo is a setup that allows for the watts location to not be as critical as with a one piece lower, no?

http://www.clubcobra.com/photopost/s...0/ppuser/10964

Ralphy

[cobrarkc]

Originally Posted by PDUB

The new splined section looks much sorter, and the splines look like they might strip out with any sort of wear, i.e. the surface area in which they mate to the hub looks whimpier. The old one looks like the input shaft on a toploader... that is pretty tough!

I'm not an ME, so I cannot say for sure, but it just looks weaker to me. I would love to hear from an expert, since I am interested in persuing the outboard brakes...

Cobrarkc, did you go with the outboard system?

I am not an ME either but here goes. Think about a Ford 9" rear axle there are either 28 spline or 31 spline with the later being stronger. Now think about how much of the axle is splined, around the same amount that is splined on the newer Jag axle stub. The part after the splined area the is necked down only holds the axle stub into the hub and doesn't need to be as thick.

[mickmate]

I'm a Mech and Prod Engineer but I didn't stay at a Holiday Inn last night. You guys have a good eye for what will and won't work and how to put it together, you're practical engineers. The key to comparing the parts you're looking at is CSA (cross sectional area) of the shaft that is acting in shear. If you have a lot more splines even if they aren't as deep if the CSA is greater on the part that is in shear it will obviously be a lot stronger. The watts is great in this application and I think very necessary. One of the high HP cars a customer of mine has is eating holes right through the rear inner fender with the flex and play of lower control arms allowing tires to touch it.

[PDUB]

Daze, got any pics with the calipers in place? I'm curious about picking up the mounting points for a Watts link... top and side views.

[PDUB]

Nick, are those caliper mounting points on the hub strong enough to hold a bracket for the Watts link? Not sure if there is room for one, but...