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Question about differential, Pass roll bar.
I'm somewhat bewildered on how exactly the limited slip diff. works in the Kirkham.
The original Jag rear worked like the corvette in that a solid half shaft was required to apply forces to dis-engage the clutch packs to allow one of the wheels to spin at a different rate in a turn. (these were essentially the same carriers used in solid axle rears) Since the dual A-arm requires a slip type shaft, how is the diff. activated? :confused: Or worse is it activated at all?%/ Spools are mighty rough on tires in street cars. Also even though it's not original I'd like a Passenger roll bar, anyone know of a source for a matching one. (SS) Kirkham should offer this IMHO. Passengers are people too!!!:eek: |
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I haven't seen any pictures yet of that area so I don't know if they use stub pipes or flanges.
Since the body is rivited in at assembly time plus I'm opting for the stainless frame it may be a tough mod. The added problem of inconsistant wheel base among mfgs. and chassis design means the roll bars aren't universal. I think the car looks better with dual bars as well. I'm suprised how few are out there. |
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Kirkham does offer dual roll bars, you just have to ask. The differential works fine. The half shafts transfer torque like a solid shaft, the slip joints just allow them to change length.
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It works the same way, instead of the forces running along a solid half shaft to resist the twisting forces the half shafts transfer this force to the output flanges on the sides of the diff. The clutches inside are somewhat like motorcycle clutches, which are "Almost" fully locked together, when enough strain (Like turning a corner) is applied they allow some slippage. It is quite easy to adjust the pre poad on these clutches, either by using different spring washers or re packing the plates in a different order. A little like... If the clutch is too stiff and the plates are packed + - + - + - then re pack them + - - + + -. This would in effect reduce the grip by 40%.;) |
The sideshaft design has nothing to do with the operation of the LSD. The Jag is the Salisbury type with a clutch pack like you describe. The Kirkham , as far as I understand and the Shelby uses a Dana Lsd which has a cone clutch. The solid or spicer type sideshafts are going to turn the differential unit exactly the same.
John |
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Oops! Should have mentioned. I'm only familiar with the Jag diff. But as said above, the type of shafts make no "diff"-erence.:D |
Still seems a little funky to me, cone or clutch it's the same forces needed to activate either.Since the slip shafts are intended to allow for wheel travel (grow / shrink with knuckle travel), it would also cause the same action against the carrier as horizontal load shift (taking a turn). Granted one is a brief force compaired to the other.
Even a hard launch would cause a "crouch down" of the rear and activation on let-up, so I can't see a pre-load on the slip shafts of any kind, they have to free-float. Has anyone noticed an inside tire chirp when taking a curve? Sorry if it seems like nit-picking, but this can easily cause differential heat / failure. Obviously a standard spider gear carrier would not be effected, perhaps this was a compromise on the original sc cars when they dumped the rear leaf spring? Glad to hear the Pass bar is available, from what pictures I found it looked like a tough add-on to do after the fact. From what I could see each attachment point required added brackets of some kind. |
Actually there's a way to make it work but it requires fixed output flanges (anchored to the frame) and a "floating differential". The weight of the diff. shifting would disengage the outside wheel clutch/cone.
The more I think about it the more I'm convinced it's not designed right as is. Not to be a PIA, just want the car to be the best. I have no doubt the Kirkhams do as well. Actually I take that back, float the knuckles on the A-arm joints (for side to side movement) and switch to solid shafts. The driveshaft forces would effect a floating diff. I'd guess. |
Ronbo,
I don't believe a lateral force being applied to the diff through the axle (or half shaft) is needed to activate or deactivate the limited slip. It sounds to me like that is what you are suggesting??? Check out this website: www auburngear.com/aftermarket/products/differentials/ Kirkham has used a couple of different limited slip units over the years. We are currently using Auburn units. The cars do not experience chirping of the inside tires. That would most likely come from a locking differential as opposed to the limited slip that we use. I am sure that someone with intimate knowledge of how clutch type limited slip diffs work will chime in and help us all understand. FYI: We are having a great sale today in conjunction with our open house! |
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Summit 08 SALE |
Joe, could you take a minute and describe the Kirkham rear? I take it that it utilizes the Dana 44, like the Jag, but does it have inboard brakes? If not, how do you all work the rotors & hubs to go with the pin drives and what rear brakes do you go with?
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The "side forces" that is if you pushed the wheel towards the diff has absolutely nothing to do with the operation of the differential. The output shaft bearings clearances are preset within the diff casing. If by putting force from the side created movement "inside" the diff you would have to throw the diff away. The holding or breaking of the clutch pack is caused by the rotational forces of the driveshaft not the transverse forces.
The same applies to both types of diffs. The spicer sideshafts are needed when you have double wishbone suspension because (remember Geometry at school), the control arms and the sideshaft do not scribe the same arc as they go through their respective ranges of travel. So the sideshaft needs to have an adjustable arc !!! I hope that explains it in somewhat simple terms!!%/:JEKYLHYDE |
Yep, I was wrong. Seems it's merely a "brute force" approach where the clutches, cones break loose from enough pressure. This "bias" is determined by the springs.
Found this on one of my favorite sites: Howstuffworks "Clutch-type Limited Slip Differential" Thanks for all the input everyone. Patrick I can answer your question, they use outboard brakes (wilwood). There are pictures on Kirkham's site of some of the components in the "manual" section and also look at Manufacturing, suspention for the outboard components. Guess I'll be calling them Monday to get my order in, can't pass on a sale. Thanks Joe. |
Talked to Joe today and got my order in...:D
After looking through all the photos of the summit page I found one that shows the roll bar mounts. (last photo of the differential section) There are two brackets welded to the frame plus they're at different heights so this is not any easy add-on. Now that I've learned how differentials work it should be a cake walk. (especially since they're putting most of it together);) I figure I can handle the fuzzy dice mounting on my own. |
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