Who Know's What a Real LIVE AXLE is??

[DUMP!]

And do you think one would live in the desert??

Dump

[ZTFab]

I've always understood them as a straight axle shaft that connects both driven wheels..no differential.

Both wheels always turn at the same rate....like on an old school go-kart.

It would really depend on it's application whether or not it would "live" in the desert.

Are we talking 80HP or 800HP?

[jgbjgb]

A live axle is just another name for a solid axle with a differential, it is one unit that moves as one unit.


I've always understood them as a straight axle shaft that connects both driven wheels..no differential.

Both wheels always turn at the same rate....like on an old school go-kart.


That would be a chain driven axle or chain drive.

[FullsizeFun]

A live axle is just another name for a solid axle with a differential, it is one unit that moves as one unit.



That would be a chain driven axle or chain drive.

No, not what Dump is talking about. A typical rearend houses a right and a left axle shaft that are driven by the spool. A "Live Axle" is ONE axle shaft the full width of the rearend that drives both wheels.

Dump, I think if it was made by the right axle builder it could work. Are you trying to gain strength? Lose weight? Less Parts? What is your goal?

[FABRICATOR]

TT's use a real live axle. But one can modify a definition if one wants to.
Perhaps something along the lines of a sprint car. As in one long axle, no axle housing, only a diff carrier and outer bearing units. Not a new concept. Could save some weight but it has some complications.

[DUMP!]

But one can modify a definition if one wants to.

Not looking to modify anything. Why are you always so condesending??

All the books I have looked at dealing with suspension set up etc. refer to the type of housing like in a TT as a Solid Axle or Beam Axle. Bob Gordon was the first person I ever heard refer to a Live Axle and he was talking about the first Stadium Toyota trucks PPI built back in the early 80's. He also said his Blazer (Parnelli Jones Built) had a Live Axle in it. I know also the last Stadium Toyota trucks PPI built also went back to them after many years of using standard type housings. The way I understood it was that in a Live Axle rear end there is no axle inside a tube, no housing just the axle tube. The tube is the axle and the part you see is the part that turns thus the term "LIVE". They require a stationary center section and what is referred to as a birdcage or bearing unit on either end of the moving (rotating, LIVE) axle tube. Typically two suspension links would be connected to the center section and two links would be connected at each of the outer ends of the axle tube at the birdcages. I was wondering how realistic it would be to use one in a TT today. I see it as the only way one could reduce unsprung weight on a truck of this type and maintain something close to the existing strength and wheel travel. What are the complications ol wise one??

Dump

[DUMP!]

I've always understood them as a straight axle shaft that connects both driven wheels..no differential.

Both wheels always turn at the same rate....like on an old school go-kart.

It would really depend on it's application whether or not it would "live" in the desert.

Are we talking 80HP or 800HP?

You got it ZT. I'm thinking 7-800 horse


A live axle is just another name for a solid axle with a differential, it is one unit that moves as one unit.

That's what I figured most here on RDC would think. A Solid Axle is not a Live Axle the way I understand it. Just because the axle moves up and down does not make it "Live". Live means you wouldn't want to touch it when it's moving or you would get all raped up in it. Things that use Live Axles are Go karts, Sprit Cars, Midgets, Some types of circle track cars, PPI stadium trucks and PJ's Blazers.



That would be a chain driven axle or chain drive.

Sprint cars are not chain drive


No, not what Dump is talking about. A typical rearend houses a right and a left axle shaft that are driven by the spool. A "Live Axle" is ONE axle shaft the full width of the rearend that drives both wheels.

Dump, I think if it was made by the right axle builder it could work. Are you trying to gain strength? Lose weight? Less Parts? What is your goal?

You got it as well. Lose Unsprung weight would be the goal.

Dump

[ZTFab]

Wow, I would love to look at those "bird-cage" assemblies.

No matter how innovative some of the new vehicles are nowadays, I am still amazed at the technology and conceptual ideas that builders used decades ago....even if it never proved beneficial or successful.

[jgbjgb]

A live axle is just another name for a solid axle with a differential, it is one unit that moves as one unit.


That's what I figured most here on RDC would think. A Solid Axle is not a Live Axle the way I understand it. Just because the axle moves up and down does not make it "Live". Live means you wouldn't want to touch it when it's moving or you would get all raped up in it.




1. A live axle, sometimes called a solid axle, is a type of beam axle suspension system that uses the driveshafts that transmit power to the wheels to connect the wheels laterally so that they move together as a unit.

A live axle consists of a central differential in a single housing that also contains the driveshafts that connect the differential to the driven wheels. The differential is connected to the engine via a swinging drive shaft and a universal joint. The complete assembly may typically be suspended with leaf springs, coil springs or air bags.

In small trucks solid front axles have generally been replaced by independent front suspension.

Some live axles use trailing arms, semi-trailing arms, Panhard rod, or Watt's linkage to control the vertical and lateral movements of the axle. Others, particularly older vehicles, use Hotchkiss drive, in which the leaf springs provide axle location as well as suspension.



2. A live-axle (also called solid-axle, beam, or dead-axle) suspension is an automobile suspension that uses a single-piece axle to connect the front or rear wheels, side-to-side. This contrasts with an independent suspension (IRS) design which uses constant velocity joints to link the wheels, allowing the wheel on one side to move vertically while the other does not.

Live-axle is considered inferior to independent suspension because the drive components (shafts, gears, etc) are part of the suspension and move with it, thus greatly increasing unsprung weight and decreasing traction. Until the 1980s it was the most common form of driving axle found in the average rear-wheel drive car.

A typical live axle consists of a solid tube with a central casing containing the differential, with the wheels mounted on each end of the tube. The drive shafts (for driven wheels) run inside the tubes. The whole assembly is connected to the vehicle body or chassis by links and springs. Because the axle follows the road, with the vehicle body moving above it, drive is supplied to the axle via a swinging propeller shaft and universal joints. While relatively cheap to manufacture due to its simplicity, its weight (which is part of a vehicle's unsprung weight) can lead to handling problems.



3. A live axle is a type of transmission to a set of wheels in which the drive components (shafts, gears, etc) are part of the suspension and move with it. Until the 1980s it was the most common form of driving axle found in the average rear-wheel drive car.
A typical live axle consists of a solid tube with a central casing containing the differential, with the wheels mounted on each end of the tube. The drive shafts run inside the tubes. The whole assembly is connected to the vehicle body or chassis by links and springs. Because the axle follows the road, with the vehicle body moving above it, drive is supplied to the axle via a swinging propellor shaft and universal joints. While relatively cheap to manufacture due to its simplicity, its weight (which is part of a vehicle's unsprung weight) can lead to handling problems.

Live axles are still widely used on trucks and heavier vehicles, but in cars they have mostly been replaced with front-wheel drive or independent rear suspension (IRS) designs.

[NIKAL]

I dont know if a Live Axle would work in Off-Road. Dump said the PPI Stadium trucks used one, but that is in a controled racing environment. And PJ's blazer had one and that was a desert truck, so it must have sort of worked. But I would think the amount of debree kicked up off the front tires would not be good and you would get a ton rocks hitting the axle, bushes and other things wrapped up around the axles. Not only would this damage an axle, could you imagine the vibration you would get with having something wrapped around and axle. There is a reason most trucks carry a extra drive shaft. I would think a spair axle would have to be on the list of things to have on the truck during a race. And how many times have you seen an axle housing break? I have seen it quite offen, so your axle would have to be much stronger then the current housings we are using today.

[partybarge_pilot]

I don't see it being any more vulnerable to damage or debris than an IRS axle. You would need to take some of the same precautions with it like wrapping it with rubber and maybe some sort of seal shield for the center section.

I had actually considered this for a 7S truck after looking at the PPI truck for a while. With leafs and a single point bar for the center section, it would have had a lot of the same characteristics of a 4 link and still be legal. Not to mention the unsprung weight savings...... Now it you could get a whole bunch of spline mount knock off wheels made........

[partybarge_pilot]

Giggity....

http://www.race-dezert.com/skunkz/mteg_ivan/42.jpg

http://www.race-dezert.com/skunkz/mteg_ivan/36.jpg

[racer56]

Dump,

I like your thinking, I want to try the same thing. My idea is to use a live axle rear end with a reverse four link and a torque tube. The trailing arms would go to the bottom of the bird cages. The upper links would go from the top of the bird cage to the center of the back of cab. A torque tube would go from the center of the rear end to the transmission. The advantages would be at least 30% unsprung weight savings, increased ground clearance, more power to the ground, a fully protected drive shaft assembly, ease of maintenance and possibly more cost effective.

[philofab]

Dump,

I like your thinking, I want to try the same thing. My idea is to use a live axle rear end with a reverse four link and a torque tube. The trailing arms would go to the bottom of the bird cages. The upper links would go from the top of the bird cage to the center of the back of cab. A torque tube would go from the center of the rear end to the transmission. The advantages would be at least 30% unsprung weight savings, increased ground clearance, more power to the ground, a fully protected drive shaft assembly, ease of maintenance and possibly more cost effective.

A reverse four link? I think that would lead to "plunge" style issues as the rear end and torque tube would travel in different arcs. Most vehicles that had torque tubes used it as part of the suspensions link system. A torque tube would probably work well for a "live" axle for DUMP! though.

[philofab]

And do you think one would live in the desert??

Dump

They work for quads in a slightly different manner without breaking. A quad sees way more forces on the axle due to the rear suspension style. Why not?

I personally think De Dion is where the future is at. Less unsprung weight and almost the same handling as a current TT. Buggy guys couldn't complain the same way if you entered your TT in C1 without a body on it! :)

Only problem is the requirement for huge amounts of plunge between the wheel and diff. Back to the drawing board....

[philofab]

Giggity....

http://www.race-dezert.com/skunkz/mteg_ivan/42.jpg

http://www.race-dezert.com/skunkz/mteg_ivan/36.jpg

Anyone know if this actually ends up weighing less?

[standfast]

Doesn't seem like there is a huge weight savings possible. Maybe the rear brakes could be ran up at the transmission output. This can be a very powerful brake being it is gear reduced at the rear end. How much does a rear housing like a tubeworks weigh? Could a cast aluminum one be lighter and as strong?

[partybarge_pilot]

Well, I know that an 8-3/8" Midget quick change axle weights about 50#'s without hubs and brakes. A non-QC 10" with all the magnesium bells and titanium whistles would be under 100#'s without brakes and hubs. If you wanted to get really funny and run the stainless clad aluminum rotors and knock off hubs, you could have a complete ready to roll rear under 150#'s.

[partybarge_pilot]

A light TW rear is 250, a heavy one is 350.......

[DUMP!]

Dump,

I like your thinking, I want to try the same thing. My idea is to use a live axle rear end with a reverse four link and a torque tube. The trailing arms would go to the bottom of the bird cages. The upper links would go from the top of the bird cage to the center of the back of cab. A torque tube would go from the center of the rear end to the transmission. The advantages would be at least 30% unsprung weight savings, increased ground clearance, more power to the ground, a fully protected drive shaft assembly, ease of maintenance and possibly more cost effective.

Don't know if I'd go with the torque tube. In a TL maybe you could get away with using a drive shaft that would fit through a torque tube but in a TT I think that you'd want a standard drive shaft. The reverse 4 link would actually work better for strength, I think, and would eliminate the need for a big truss or any truss for that matter because it offers a more even distribution of load over the axle. Instead of loading the axle at top, center and lower ends like a traditional 4 link. As for geometry with a reverse vs. traditional, it's all about where you position the links. I have both modeled in the computer and can make them both do the same thing by how the links are positioned. With no torque tube you would need a 5th link to the top of the diff to keep it orientated properly.


Anyone know if this actually ends up weighing less?

I'll let you know!


A light TW rear is 250, a heavy one is 350.......

Don't forget to add in the axle shafts because those would be eliminated with a Live Axle.

Dump

[partybarge_pilot]

I personally think De Dion is where the future is at.

Why would you take all the worst attributes of IRS and beam axles and mix them?

[philofab]

Why would you take all the worst attributes of IRS and beam axles and mix them?

I guess I should have made it clear I was joking.... :D

[racer56]

Don't know if I'd go with the torque tube. In a TL maybe you could get away with using a drive shaft that would fit through a torque tube but in a TT I think that you'd want a standard drive shaft. With no torque tube you would need a 5th link to the top of the diff to keep it orientated properly.

Dump,

I was thinking of using a standard drive shaft inside a larger than normal torque tube, but it might be a packaging nightmare? I had a race car that had a 5th link/Torque arm in it, that was adjustable at the front pivot point up and down and side to side. Adjusting the torque arm mounting point made a huge difference on corner entry/exit and forward bite. When I had it adjusted right, the increase in forward traction was unbelievable.

[Superfab]

I see the potential. If you built the whole thing from scratch you could make a 4" dia axle, possibly a high pinion center with a gear lube pump built in (keeps the driveshaft and pinion seal out of harms way), and the pick-up points could be built in. The gear housing could be built from 2024 or 7075 billet for strength. The only drawback is possible rock damage to the axle and the harmonic it could cause. Proper material and heat-treat would result in a pretty tough piece.

[motorhead]

Is there a thrust bearing being used at the lower link mount (see circle in pic) to allow the axle to rotate and keep the axle from laterally moving?

A minor disadvantage would be increased inertia created from a larger diameter axle rotating. I would think any substantial reduction of unsprung weight would out weigh the draw back of increaing the inertia. I would expect the additional inertia to be almost negligible in addition to the tire, but will crunch the numbers to see how much calculus I've forgoten in the last 2 months :D.

[racer56]

Is there a thrust bearing being used at the lower link mount (see circle in pic) to allow the axle to rotate and keep the axle from laterally moving?

A minor disadvantage would be increased inertia created from a larger diameter axle rotating. I would think any substantial reduction of unsprung weight would out weigh the draw back of increaing the inertia. I would expect the additional inertia to be almost negligible in addition to the tire, but will crunch the numbers to see how much calculus I've forgoten in the last 2 months :D.

Don't forget that traditional rear ends have large diameter steel spools or diff's and the live axle rear end pictured does not.

[Superfab]

Herzog has had some experience with this. From what I was told the axle was 4" dia. They did a test where they held the brakes and applied power. The deflection in the axle was impressive. It would be interesting to video the axle under load and see the deflection and possible harmonics while running. In a heavy desert truck the axle would see all the load vs. a std housing where the loads are shared.

[partybarge_pilot]

Is there a thrust bearing being used at the lower link mount (see circle in pic) to allow the axle to rotate and keep the axle from laterally moving?

That is what is called a "Bird cage" in the roundy round world. They wave 2 ball bearings in them.


A minor disadvantage would be increased inertia created from a larger diameter axle rotating.

With an aluminum axle, the mass and inertia wouldn't be much more than a conventional set-up. The reduction in unsprung weight on the other hand would be significant.

[Samco Fab]

I cant imagine that vibrations would be all that bad, even if the axle was dented or slightly bent. A axle rotates 5 to 6 times slower than the driveline. 39" tires dont spin that fast even if you are going 120 mph.


I know it would add unsprung weight, but what if you made the birdcage a gear reduction hub like a Unimog or Hummer. It would reduce the loads on the axles in half (2 to 1 gear reduction) , and raise the axle shaft and pumpkin about 5" up out of the way. You would have to build a gnarly birdcage in the first place, gear reduction is not that far fetched, and the drive line would also be way up out of harms way. Your ring and pinion would also be about a 3 to 1, and actually have sufficient teeth on the pinion, as well as not spin fast enough to get really hot.

I think gear reduction at the wheel will be on future off road machines.