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3/13/2012 7:17 pm  #31


Re: The Jaguar IRS picture thread

I'd worry more about the LCA. All of the acceleration is tied to that using a 6" lever. So if you have 300 ft lbs of torque, multiplied by a 10:1 reduction ratio that's 1500-3000 ft lbs at the hub, which I think translates to about half that on the LCA. You suspension guys could clarify that some. Anyway, 750 to 1500 ft lbs of torque is an awful lot to apply to an unbraced welded tubular LCA.

Jim

 

3/13/2012 8:32 pm  #32


Re: The Jaguar IRS picture thread

Jim,
If you look there are radius rod mounts on the LCA. They are, the radius rods, sold separately. As far as the upright, it would seem to me the tubular stainless would be stronger than the factory aluminum. However I'm still scratching my head about the Dick Guldstrand C2/C3 aluminum uprights. Maybe a tire planted tends to want to go straight better than I'm thinking. This strength with an upright is why I like the T Bird knuckle design.

Last edited by Ralphy (3/13/2012 8:38 pm)

 

3/14/2012 7:10 am  #33


Re: The Jaguar IRS picture thread

A radius rod doesn't do a thing about the torque applied to the LCA. It transfers straight line force only, but that force is being applied six inches above the tie-in point. If you have 1500 ft lbs of torque being applied through a 1 ft long lever to the contact patch then you have 1500 pounds of force being applied at the axle. The problem is that that 1500 lbs is also rotating around the radius rod six inches below the axle, putting 750 ft lbs of torque on the LCA itself. The Jag LCA is a very stout large diameter tube and will handle it just fine, but a tubular ladder has almost zero torsional rigidity. It will flex like a noodle.

Nobody seems to pay much attention to the counter torque that is generated in a stock Jaguar IRS system. But it is essential to its proper operation so this is a big big oversight.

Jim

 

3/14/2012 2:32 pm  #34


Re: The Jaguar IRS picture thread

I get it, however Heidts is doing the same and selling the design. I agree with you and I plan to have some sort of upper control myself.

http://www.hotrod.com/howto/hrdp_0712_irs_for_musclecars/photo_16.html

Ralphy

Last edited by Ralphy (3/14/2012 2:34 pm)

 

3/14/2012 4:59 pm  #35


Re: The Jaguar IRS picture thread

No comment

Last edited by tyrellracing (10/27/2012 6:27 pm)

 

3/14/2012 9:14 pm  #36


Re: The Jaguar IRS picture thread

         
Join Date: May 2002
Location: Brisbane Australia, QLD
Cobra Make, Engine: RMC under re-construction, GenIV with tremec 600, Jag 3.31 L/S diff
Posts: 3,184
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Default
[b wrote:

With regard to servicing the Jag center you should be aware of this info:
DazeCars, Mustang IRS or Independent Rear Suspension page IV

With regard to shortening and other info then go here:
Independent Rear Suspension Forum / The Jaguar IRS picture thread

and here:
DazeCars, Mustang IRS or Independent Rear Suspension page III

With regard to other info re IRS then choose a thread from here:
Independent Rear Suspension Forum / Independent Rear Suspension Forum[/b]
__________________
Brisbane Australia:
Beautiful one day, perfect the next.

http://www.clubcobra.com/forums/australian-cobra-club/114086-jag-rear-end-width.html

Why has the details of my membership of club Cobra been copied here?.
Is there some rule that I can't link to this site when some-one in another forum asks questions regarding the modification of Jag rear ends?.

 

3/15/2012 5:16 am  #37


Re: The Jaguar IRS picture thread

Rebel are you referring to my post maybe? If so I think I was only telling Daze about his site getting exposure. The exact opposite is true I think. I always try to add where I get any info I post and a link. This does to two things. First I can verify where I saw such (any) info. Then second if a person finds it useful, they can follow the link and maybe read more.  If you look at any pics I posted, you should for the most part see a link where it came from. I feel it makes this site more useful as a IRS data collection site.

Let me ask you this, have you seen the page where I put all the videos?  I collected 100 plus and tried to categorize them.

http://irsforum.boardhost.com/viewtopic.php?id=256

Ralphy

Last edited by Ralphy (3/15/2012 5:29 am)

 

3/15/2012 5:42 am  #38


Re: The Jaguar IRS picture thread

Jim and TR, let me say it again. My favorite design has got to be, The Roadster Shop. Using the Corvette C5/C6 uprights. They do so many things right in my opinion. The LCA is a 1 5/8" tube, rated at 1,400 HP. Maybe a little stout for my needs. I think it could be a bit lighter for lower HP motors.

http://img849.imageshack.us/img849/4060/screenshot20111116at915.png

http://www.roadstershop.com/products/suspension-independent-rear-unit

Last edited by Ralphy (3/15/2012 5:46 am)

 

3/15/2012 5:42 am  #39


Re: The Jaguar IRS picture thread

Heidts is a great example of the problem, and I imagine their customers are having terrible problems with wheel hop, can't figure out where it is coming from, and blaming the original Jag IRS design for not having an upper link. That ladder appears well made, so it will store up an incredible amount of torque energy before permanent distortion sets in, just like a big old spring. Once the tire slips a little it will release and re-set. I imagine if you had a high speed video of the wheel you'd see it moving around all over the place, forward, back, up and down.

Jim

 

3/15/2012 5:46 am  #40


Re: The Jaguar IRS picture thread

Ralphy, that's nice enough if you have the room for it. MGBs do not, without major surgery. The Jag can be made as a bolt-in unit, which is a major advantage, and properly set up it is a very good suspension.

Jim

 

3/15/2012 5:49 am  #41


Re: The Jaguar IRS picture thread

 

3/15/2012 5:53 am  #42


Re: The Jaguar IRS picture thread

I don't know. However at Club Cobra I see many of the Jag guys complaining about wheel hop. That's where the upper Watts link came in by Mickmate.

Jim Blackwood wrote:

Ralphy, that's nice enough if you have the room for it. MGBs do not, without major surgery. The Jag can be made as a bolt-in unit, which is a major advantage, and properly set up it is a very good suspension.

Jim

Another option may be something like this.
http://www.clubcobra.com/photopost/data/500/DSCN1543_Small_.JPG

Last edited by Ralphy (3/15/2012 5:56 am)

 

3/15/2012 6:00 am  #43


Re: The Jaguar IRS picture thread

One thing I like about Roadster Shop's setup. Is the design controls the toe from behind the halfshaft. To me it seems a very strong position to eliminate the upright from twisting. Plus depending on how long you make that link, you can change the roll/steer. From zero to plus or minus.

 

3/15/2012 6:09 am  #44


Re: The Jaguar IRS picture thread

Another way to remove the twisting of the upright. Is to move the LCA way up and wide, like the T Bird design. However for some this creates an issue for the coilover mount on the LCA. My case is I lose height/length for my coilover. I would have to somehow make room to drop the CO thru the LCA

 

3/15/2012 9:18 am  #45


Re: The Jaguar IRS picture thread

Keeping the upright from twisting is one thing, the LCA is quite another entirely. I recall some discussions about the upper watts link, but from my perspective there are three very critical issues with it:
1) Space limitations mean it will not fit in the MGB without compromising tire width, suspension travel, ride height, or sheet metal, and perhaps several of those in combination. I have 315/35-17" tires under the car with a 3" flare.
2) The immediate result of the top link is to transfer all of the counter torque loading of the differential away from the LCAs and into the differential mounts. The only way to do this safely is to provide a sturdy and somewhat rigid lower mount from the differential to the body. Most do not do this. The stock design only applies longitudinal torque to the differential mounts, counter to the driveshaft and at roughly 1/4 to 1/3 the lateral torque. The half shaft counter torque is transferred to the LCAs where it is balanced out by the torque produced by acceleration forces acting on the upright, using the upright as a lever arm to produce the torque.
3) The add-on completely changes the way counter torque and acceleration loads are handled by the suspension, removing those loads from the admittedly beefy (stock)  LCA and applying them to the Watts link, which is usually diminutive. It now becomes a highly stressed member of the suspension package, yet I have not seen one so far that was sized to handle those loads.

Wheel hop is anything but a typical characteristic of the Jaguar suspension, and is very dependent on the specifics. It requires energy to be absorbed and stored in some component(s) of the suspension and then released as tire slippage occurs. So far we have had no instances of wheel hop in the MG-Roadmaster, despite the 455 Buick engine. The devil is in the details. If there is wheel hop, there is energy being stored somewhere. It may be in the linkages, the bushings, or in some cases perhaps even the tires but it is most definitely there somewhere. Eliminate that and the wheel hop will go away.

OTOH, if you are regularly winding the engine up and dropping the hammer, (Which means you are building a dragstrip car and would benefit from things like jacking the tires into the pavement on launch.) the Jag IRS isn't particularly well suited to this use, and a solid axle may be in your future. There is a good reason why top fuel dragsters do not run IRS.

Jim

 

3/16/2012 2:54 am  #46


Re: The Jaguar IRS picture thread

No comment

Last edited by tyrellracing (10/27/2012 6:29 pm)

 

3/16/2012 9:57 am  #47


Re: The Jaguar IRS picture thread

Sounds pretty rigid, where do you think the energy was being stored, the inner ends of the LCAs maybe? Another thing that plays into it is that some recommend that the Timken bearings be set up with free play. Since you have Timkens both in the lower outer pivot and in the axle spindle, any excess play will aggravate the problem. Timken (the Manufacturer of the bearings) recommends preload, and in the case of the pivot bearings where rotational loading is exceedingly slow they easily tolerate a very heavy preload. This takes a great deal of slop out of the system.

There isn't a whole lot to be done about the inner needle bearings other than to replace them with a different type,  but this does present an opportunity to redesign the LCA to a lighter unit with more torque rigidity. I have such a design in the works.

Another problem area is the attachment of the LCA pivot brackets to the differential case. The bolts are too close together and are in single shear, quite clearly a design compromise, and the cage was relied upon to reinforce the attachment. I haven't addressed that shortcoming but at the very least the brackets should be pinned into the case.
Far better would be a strut from the top of the housing forward and down, but the only way that can be made to work is with a new monolithic LCA/strut assembly that transfers rotational loads into the strut to the top of the housing. This can be done rather easily once the new LCA is built but I won't be starting on that for some time yet unless someone orders a suspension package from me. Still, maybe after my car is back on the road I can take that design back up and do something with it.

Jim

Last edited by Jim Blackwood (3/16/2012 10:45 am)

 

3/16/2012 5:10 pm  #48


Re: The Jaguar IRS picture thread

No comment.

Last edited by tyrellracing (10/27/2012 6:30 pm)

 

3/16/2012 5:37 pm  #49


Re: The Jaguar IRS picture thread

No comment

Last edited by tyrellracing (10/27/2012 6:31 pm)

 

3/17/2012 5:16 pm  #50


Re: The Jaguar IRS picture thread

No comment.

Last edited by tyrellracing (10/27/2012 6:32 pm)

 

3/17/2012 5:21 pm  #51


Re: The Jaguar IRS picture thread

TR,
Trying to stay within the Jag concept. I'm throwing ideas out for Jag conversions. I lose track myself, however this is the Jag thread. The AU UCA may be limited but if Jim can copy the basic shape and make it fit? It's all good.

Anyhow I still have not decided which way I will go yet.
Ralphy

Last edited by Ralphy (3/17/2012 5:29 pm)

 

3/18/2012 8:22 am  #52


Re: The Jaguar IRS picture thread

So now we both understand this is a Jag thread. And I guess you will stop trying to highjack it. And quit going into what I'm doing with my C3. My pic of as you say one shock mount is more than you have shown. So I guess it's Ralphy 1 shock mount Vs.TR's nothing shown. Post your pics, your talents obviously are enormous. Can you operate a camera?

I think the discusion we were having was on how Jim could improve what he already has. And not building from scratch a whole new T5 IRS. Which by the way, he has done a nice job. He has some pics unlike some others here.
Ralphy

Last edited by Ralphy (3/18/2012 9:42 am)

 

3/18/2012 10:01 am  #53


Re: The Jaguar IRS picture thread

Guys, in all fairness the flow of forces is more complex than any of us have described up to this point. For instance, and again starting with the Jag, when TR adds his top link he is not simply redirecting all torsion and linear acceleration forces into the chassis. We are still left with the anti-torque from the differential. This is not all simply transferred into the frame of the car, it is also applied to the LCAs, and in unknown proportion. Plus although the  level is only 1/3 to 1/4 as much, the transverse anti-torque is also there.

Now, TR I must agree with Ralphy here, both of us have provided clear photos of our work and/or the concepts we've been discussing, and while your descriptions have been pretty clear some things are not. Example, your 45* strut braces. 45 degrees in which plane? Can't see that without a photo. In one plane they would resist one force, in a different plane another. I can think of at least one orientation where they would be completely ineffective but I've given you the benefit of the doubt. Not that happy about it, but trying to be fair.

The AU IRS aside, my application generally precludes a top link as in ANY iteration it will raise static ride height and/or decrease suspension compression. I feel that space would be better used to replace the solid half shaft with a light weight tubular one, but again the cost is the same. So my focus is to strengthen and lighten the Jag IRS with minimal fundamental design changes, like adding a top link. Not that I'm against it particularly as a concept, just that it's poorly understood and there is extremely little room for it. Consequently a firm understanding of the forces involved is essential, as the size of the links would have to be minimized in the extreme.

With that thought in mind it is first necessary to fully appreciate every aspect of the basic flow of forces, take every conceivable action to rigidify the transitions, and only then to look at what happens to those forces when the top link is added. Rather than mummify the body, apply a small band-aid in effect. If the force flow through the top link can be reduced to 5% of the total for instance, then a small and light link can be highly effective in controlling unwanted vibrations such as wheel hop.

I'll give you an example using a lathe. When turning a long slender piece it is common for harmonic vibrations to build up in the tool and part to the point that a visible and even rough chatter pattern can be seen on the surface of the part, including a vibration that can be felt in the machine and heard by the operator. This can happen even with the most rigid of machines, tooling, and even sometimes with short and rigid parts. However, despite the strength of heavy cast iron, alloy steel, carbide tooling and the metal being worked, frequently a finger placed on the rotating part will stop the vibration. What is the strength of the finger in relation to all the above? Miniscule. But it is just enough in just the right spot to shift the balance, alter the frequency, and dampen the vibration, resulting in a smooth cut.

For the Jag IRS this is what I see as the function of a top link. The fundamental structure is already there and well proven in the normal envelope of operation. Just because someone wants to exceed this envelope, or because they constrict it by installation compromises does not mean the basic design is flawed or that a fundamental design change is needed to fix it. In preventing chatter the approach is to stiffen the structure by shortening the most flexible members, change the speeds and feeds, look for compliance and eliminate it, and then only as a last resort apply band-aids or go to another machine design. I think that approach is equally valid here and I doubt we've exhausted our remedies.

Jim

 

3/18/2012 6:22 pm  #54


Re: The Jaguar IRS picture thread

Jim, posting of the AU UCA was nothing more than a visual aid. My thinking was you may be able to copy the geometry. My first question would be, how tight of a bend can be put into say a 1" dia. DOM tube, 4" maybe a 3" radius?  Your heartburn is the UCA. Mine will be length and position of the coilover. Every conversion has it's issues. Do you still have a boot?

I finally think I understand your analogy. The UCA is the finger on the shaft. And being the position (height) of the UCA. The further you raise it's position the less strength it needs to have.

Two misconceptions about machine shops. No we don't always sit on our butts. The work is  more a mental job than a physical most times. You see me sitting however inside I'm planning and you just interrupted my thinking with your jealous comments. Then second, that Bridgeport that you think is a bull of a machine is not as stout as you think.

Oh and that stupid feeds and speeds chart you have? Throw that in the trash, the machines your running were never built stout enough to achieve those numbers and you have no coolant! LOL!

Ralphy

Last edited by Ralphy (3/18/2012 7:35 pm)

 

3/18/2012 7:49 pm  #55


Re: The Jaguar IRS picture thread

A fairly good aid too, and providing the center section could be kept clear might not have to reduce travel. But unless very carefully designed, would necessitate CV halfshafts, a big complication with inboard brakes. Plus it is not the right design to stiffen the longitudinal axis, which I suspect is where most of the wheel hop comes from.

Jim

 

3/19/2012 5:17 am  #56


Re: The Jaguar IRS picture thread

Jim,
I'm not sure if I have this right but it would seem to me acceleration forces come from the center of the axle. So if you have no UCA the wheel centerline is somewhat free, wanting to pull/move forward of the LCA in more of a rotational form on the LCA's outer pivot points, twisting the LCA. Which would want to load energy into your LCA.  Once the resistance equals the traction the energy is released snapping back home. The axle centerline will rapidly move for and aft, loading and unloading, wheel hop? So if you arrest the force from above in some form UCA. The force on the LCA is no longer rotational but more linear. The design of a control arm deals well with linear forces that's it's strength working in the same single plane. Are you still concerned the LCA design you have, still would want to move forward? The extra reinforcement you built to the LCA. Would it have been better to have it behind the bone? Adding to that as TR points out the aluminum upright twisting and loading.  The configuration looks to be nothing more than a unintended/unwanted spring, including the LCA and upright.

Another question, do you have any angle in your inner pivot points on the LCA, anti squat? If you do how much? Just being nosy here!

I look at you pics from time to time, man that's a tight area! The rotors just fit above.

Last edited by Ralphy (3/19/2012 5:19 am)

 

3/19/2012 5:50 pm  #57


Re: The Jaguar IRS picture thread

1965 Jaguar E-Type Lightweight-Style Vintage Racecar
http://img3.imageshack.us/img3/8459/3degeesnegative.jpg


I found this picture of a Jaguar lightweight racecar rear suspension set-up for racing on Hemmings.   This car is running the half-shafts horizontal with 3 degrees of camber.  Coil-overs are 825 pounds per inch.  I calculated 500 pounds/inch at the wheel on a 2350 pound car!  The description of this car is good reading: http://www.hemmings.com/classifieds/carsforsale/jaguar/e_type/1369722.html
I like the radius rods and carrier support.  The bearing air ducts are definitely cool.

Last edited by irstang (3/19/2012 5:59 pm)


"'Cars are like primates. They need to squat to go.'—Carroll Smith"
 

3/19/2012 8:05 pm  #58


Re: The Jaguar IRS picture thread

Vented brake rotors too, so that's a fairly serious effort.
Ralphy, my perspective on it is that all things have a natural resonant frequency. Wheel hop is no different, and for it to occur it must rely on the components working in harmony to amplify the frequency at which the wheel hop can occur. This is a fairly low frequency, involving several rather large parts.The more rigid and solid the parts are, and the more tightly they are joined, the higher the resonant frequency becomes, and likewise the looser and more limber, the lower the frequency. However, there is going to be a cutoff point both on the high and the low side, beyond which the harmonics will not continue to self amplify. The trick then becomes to tune the system out of the range of the resonance that is wheel hop. And I agree that twisting of the upright can and does contribute.

Any time we change the system we affect the natural resonant frequency. Odd as it may sound, it is entirely possible that something like the UHMW bushings that we used in the outer pivots on the MG-Roadmaster changed the resonance enough to prevent wheel hop, as we have not seen it on that car. But I would not naturally expect that to be the case and so would not expect that change to give those results. But considering what we are trying to accomplish it is within the realm of possibilities that the use of those bushings lowered the resonance enough to move it beyond the lower threshold. This is counter to the usual approach, where we seek to move the resonance above the upper threshold, by stiffening members, bearings, bushings and transition points, but there seems to be a fundamental advantage to the lower frequencies, as harmonic points are spread further apart and fewer opportunities exist for such things as frequency doubling. Perhaps then this is one of the secrets of the OEM compliant bushings on the forward struts. Something to keep in mind later this summer when I'm testing the unit on my car.

Many of the things we do in putting these units in custom builds greatly affect the resonance. Our choice of mountings, geometry, and components all play a part.

Regardless, adding a top link will to at least some degree reduce the torsional loading on the LCA. However it also greatly changes the entire resonance of the assembly. So it is no surprise that this addition resolved the resonance problems that TR was having, just as the finger placed on the rotating part moved the lathe out of resonance. Still, the more I think about this the more I feel that in a Jag IRS the top link is more of a modifier in many cases unless a CV is used, and this would especially be the case where the top link is a longitudinal Watts.

Just being there does not automatically remove all torsional loading from the LCA for instance. It divides the load, yes. But once compliance is taken up the load is proportioned between the two structures based on a great many factors, resulting in a highly complex picture of how the forces are now being distributed about the suspension pieces, including the counter torque being generated by the differential and transferred both to the LCA and through the chassis. With a top link such as the AU piece we add in the twisting force about the UCA's vertical axis as well as compliance of its inner and outer pivots, making the flow even more complex.

This divide and conquer scheme has been proven effective, but it is sort of a shotgun approach to curing the basic problem, and it muddies the picture as to just what is going on. The simple Jag system by contrast is considerably more straightforward. Where only one suspension member exists to do the job there is no question as to what percentage of the load is being carried by this member versus that one and under what parameters. It is 100% all of the time. Although that may not make tuning out wheel hop an easy task, once you do, it IS fairly easy to understand why it worked, and at least in theory that should make the suspension more user friendly to tune.

Anyway, my system is pretty straightforward. No angled pivots or any of that stuff, because I wanted a good baseline for possible future improvements. At this point there does not seem to be any need, but we haven't raced the car. I guess time will tell.

Jim

 

3/19/2012 8:12 pm  #59


Re: The Jaguar IRS picture thread

So Ralphy,  Have you done anything to your kit car project or are you only here to critique the efforts of others?   Nearly every member here has at least worked on their projects. You just post the accomplishments of others.  What is with that.  You have more postings here than any one else and yet you have built nothing.  You have suggested that your life is too busy to build your IRS using things you volinteered to do as your excuses.  Maybe if you spent a few hundred less hours on the internet per week and a few in your garage building your perposed IRS I would not have any gripe.  After three years of you posting with out any display of your OWN accomplishments.  I just finished my second IRS instal.  This time in my Tiger.   Its been three years,  Lets see your work!

Last edited by tyrellracing (1/13/2013 9:12 pm)

 

3/19/2012 8:54 pm  #60


Re: The Jaguar IRS picture thread

As a point of intrest Carroll Shelby began a huge number of law suits before his death.  He went after all the kit car manufacturers selling kits or whole cars using the Cobra name. Factory Five gave him a huge out of court settlement with the promise they would no longer use the Cobra name or pay an additional sum to the Shelby foundation for each car sold using the name. Since Carroll owns the name outright there have been no litigants able to beat him in court.  From what I have read the manufacturors that lost their suits have to pay a undisclosed sum for every car they sold with the Cobra name.  For some this will reach into the millions.  Many will go bankrupt.
 The foundation was formed to continue litagation and collect funds in the event of Carroll's death.

Last edited by tyrellracing (1/13/2013 9:35 pm)

 

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