4x4 IFS Front suspension idea

FABRICATOR

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Even though Rzeppa joints are of the same design, they are not identical. Most (not all) will go very close to 45*. The most common limiting factor is the axle hitting the inner edge of the outer shell. This inner edge is also the end of the ball races. Some joints can have their angle limit increased by grinding away that edge, others will loose angle capability if that edge is modified. This is because the balls are that much closer to coming out of the race. Even two joints the same size from the same manufacturer can have different angle limits depending on what axle size they are broached for. A small axle will never touch, but a big one can. The late Mickey Thompson spent considerable effort exploring this. He used to run axles that had a smaller diameter in just that area along with special heat treating. It worked well enough.

Of course this brings up the question of vehicle design. If you need to run more angle than a Rzeppa joint can provide, there is probably something else wrong. Control arms, corresponding joints, and steering, all loose effectiveness and/or strength past these angles.

The grooves in a Rzeppa joint are all the same, going the same direction. Under power, all the balls are working the same and all are rolling. Other than swiveling in place, the inner race is stationary. The Lobro style has 3 grooves facing one way and 3 another. Under power the torque is not divided up to all 6 balls at the same time. There is a combination of rolling and sliding. There is also more force acting on the ball cage. The grooves are placed this way so the inner race and the cage can slide in and out in relation to the outer race. (axle plunge)



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FABRICATOR

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Thom,
That site is more than just opinionated. It belongs to the inventors of the Thompson CV joint. The language used to "knock" other joints is obviously borrowed from their patent application. They also obviously put all the ball type joints together under the name of Rzeppa. It is interesting but IMHO not accurate. There are European trucks that use the Rzeppa joint in their drivelines The large front drive axles from Rockwell, and many military axles and drivelines use Rzeppa joints.

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JrSyko

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Sorry to interrupt, but a quick question, but what is IMHO? Please carry on now......

See ya in the dirt!
 

partybarge_pilot

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930 CV with good cages 32 deg. X 2 = 64 deg.

The truck We are setting up only has 55 deg of wheel movment on steering. With this it will turn a very tight radius. The wheel base is about 122'. I fail to see the need for more movment unless your running a longer wheelbase.
 

AZmiik

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they use Lobro type CVs that really didn't seenm that big. They run pretty messed up to. I remember seeing a set our mechanics had apart. They were worn pitted and galled but back together and on teh truck they went.

MIke
 

partybarge_pilot

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the reason the Cv's on hummers aren't that big is that they have gear reduction hub's. With something like a 2 to 1 reduction it cuts down on the driveline sizes. But there is an increase in driveline speed. The H1's were designed to go about 65 max, when you drive them around on the freeway at 70 your cv's burn up a lot faster....
 

ntsqd

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There are also two generations of CV's on HMMV's, early (=small) & late (=bigger).

Ya Fabricator, after I posted that link I had a chance to really read & study what they were saying. I think their design is too complicated with too many small, exposed to the elements, parts to ever be a workable design. Google did turn up a lot of links on the topic and I only investigated a couple.

TS

I used swerve around my halucinations, now I drive right thru them.
 

Bob_Sheaves

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Hi all!

As an aside to the discussion, everyone is missing one thing that will cut down on joint angularity at the limits of travel...that is to say-a floating axle. Imagine a carrier housing attached to the left lower control arm with a "barrel style" engine mount, attached to the right lower control arm with a 4 inch long (center to center) shackle, and a Camaro or Corvette style torque arm running from the pinion end of the housing parallel to the front propshaft and attached to the vehicle frame using another "barrel style" engine mount (Barrel mounts are another name for voided engine mounts and are barrel shaped on their bolt axis).

Just food for thought (BTW- it's been done before-check out the US patent office web site and look through the Chrysler Corp suspension patents)....

Additionally, double Rzeppas can be utilized (at axle flange and at knuckle flange), but a conventional slip shaft assembly must be installed to allow for shaft plunge. Careful assembly and alignment of the joints is also critical, lest you chatter the joints to dust due to unsyncronised vibration.

Best as always....

Bob Sheaves

<P ID="edit"><FONT SIZE=-1>Edited by Bob_Sheaves on 12/19/02 06:39 AM (server time).</FONT></P>
 

tkr

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Good to see you back Bob. I always like your input, but man....you make my brain hurt!!


Matt Nelson
Team Kwik Racing
 

CanyonMan

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Does anybody have any experience with the Doetsch-Tech 4" lift kit for 4x4 Chevys? Are their shocks any good?

Lyrch
 

FABRICATOR

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Yes, Welcome back Bob.
BTW, there are alternatives to slip joints on the shafts...

<font color=orange>The best ideas are the ones that look obvious to the casual observer.</font color=orange>
 

tkr

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Re: "BTW, there are alternatives to slip joints on the shafts..."

Such as??? I have been thinking about this pretty much non stop for a couple days now and I can't come up with a thing.

Matt Nelson
Team Kwik Racing
 

Ryno

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Great to see you back Bob!! Always good to see your posts. I just need to read it about 4 times to get all the info. =) Good stuff nonetheless.

Matt-Me too...I drove my friends 01 Silverado with 40" swampers....BADASS!! He used a custom/ whiplash kit, and custom made alot of stuff on the truck. I'm thinking the Ibeam idea....but I know someone will do a 88-98 long travel kit sometime. Too many working class guys without funds for a new truck, and like the old body style anyways. Just my .02

Ryno

Build it like a Rhino, and Leave it be.
 

Bob_Sheaves

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Thanks guys...I'm back in the US for Christmas holidays.....

I made a mistake before and should have stated that the double fixed Rzeppa and slip shaft was my personal preference. There ARE several ways to fix the plunge issue:

1. Use a Rzeppa at the wheel end and a "tripod" plunging joint at the axle (see this under most front wheel drive cars)

2. remove the retaining clips from either side of the inboard (axle end) Rzeppa and machine a longer plunging shaft, fitted with high load retaining springs (like 320lb. valve springs) on either side of the spider, concentric to the axle shaft centerline to allow for plunge motion

This is not intended as all inclusive, but rather to get some other thoughts started.

Best as always,

Bob Sheaves
 

FABRICATOR

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Re: "I have been thinking about this pretty much non stop for a couple days now "

MATT, A lot of things take weeks to figure out and months to iron out. (plus the $,$$$)

I can't get into it too much, but think of a slip joint with rows of ball bearings instead of splines. Now think: where can such a device go??? You end up with something that has very close to zero friction and wear. The low friction means no effect on the suspension and much less plunge pressure applied to the CV joints. This is especially important when dealing with high torque figures. And it does not have to weigh much either.

BTW, the Tripot or Tripod joint can be very strong, allow ample plunge, durable, and is nearly frictionless, but none of them go more than about 18 degrees. Very popular in many forms of road racing, up to and including F1.

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