Dual Case H/L 4wd?

[GeneralDisorder]

Geeze, welcome to 1908. Why not a modified planetary arrangement? I'd think that would cut maintenance greatly, plus you wouldn't have to worry about a chain abandoning ship while on the road-

 

1. Chain is reliable *enough* to do the job. Triple or quadruple chain would be used.

 

2. Automatic chain tensioners that ride directly on the chain are available so no tensioning system is required.

 

3. Chains will not NOT reverse the rotation of the existing axle shafts - unlike a "simple" gear arrangement would.

 

4. Sprockets in any size imaginable are readily available off-the-shelf and would only require minimal (if any) modifications if designed right.

 

5. Chains do not require liquid lubrication. They can run greased for long periods and as such they do not require the same level of sealed housing.

 

6. Chains are more efficient than gears.

 

7. I don't own, nor do I plan to own, a gear hobbing machine.

 

Trust me - chains are much better for what I'm planning. I've thought a lot of this through. I'm not kidding myself that it would be a daily driver, or even that it will be able to drive on the freeway.... but I'm willing to try and possibly fail.... but I will have tried!

 

GD

[zyewdall]

Stock suby is only about 22:1 in low range 1st. Most stock 4x4 trucks are in the range of 30:1 to 45:1. You can do alot of off-road stuff without anywhere near 120:1 I'm sure. Large rocks and stuff... yeah, it'd be nice.

 

The unimog U500i is available with a 3000:1 final drive. It goes 450 feet per hour at wide open throttle in the lowest gear. Just about the only thing I can think of using a ratio like this for is for slowly shoving a giant rotary snowplow through a hardpacked drift higher than the cab (which is an option you can buy with it)

Edited July 14, 2009 by zyewdall

[GeneralDisorder]

My plan is to throw a Samuri t-case in behind the Subaru transaxle, then have the additional 1.6:1 chain reduction hubs at each wheel. The Samuri case can be geared as high as 6:1 in low and also has a certain amount of reduction ability in high. 100:1+ is easily doable. The chain reduction can't be much more than 1.6:1 unless you want a trailer queen - being that you *can't* remove the reduction it has to be able to run at that amount of reduction at all times.

 

GD

[4x4_Welder]

Actually, if you use a modified planetary gearset, you can have all the gear reduction you want with no reversal of the shaft direction, and you can even keep your outboard brakes. It's actually very simple- No sun gear, internally toothed ring gear attached to the hub, axle shaft comes into the planet position. Two simple, readily available seals and grease and you're set.

FWIW, if you get a CNC with a vertical rotary indexing table, you'll have a gear hobbing machine. Ship the bits up to me, I'll harden them and lap them together if you'd like, I have the tools and know-how for that.

 

Any chain is going to fail once dirt gets into it, it's a lot easier to get a sealed greased gearset to last. I've worked on enough supposedly sealed greased chain drives in tillers to know they wear quickly, auto tensioning or not. Besides, why make it "OK"?

Edited July 15, 2009 by 4x4_Welder

[GeneralDisorder]

I do see what you are saying - but I just don't think a CNC of any kind is in the cards unless I build the thing myself.... maybe possible but I kind of doubt it. I wonder what a garage sized CNC would run?

 

I would like to have some manual machining equipment first - a mill and a lathe of my very own to start with. I have access to both at work, but that's just not quite the same as I'm not the official operator of said equipment and so accessing and using it is not as easy as I would like it to be.

 

I like the idea - it's the tools that I lack unfortunately.

 

GD

[Scott in Bellingham]

the weak link is the axles that said I wouldnt go threw all the work to get lower gears, yes I have done it , I have found that a good EJ stuffed under the hood and some 27" tires solves the low gear issue and is alot more easier if you want lower gears and bigger tires get some stronger axles ( probably not Subaru), if I did do it again I think the reduction should be between the engine a EJ or course and the stock dual range maybe a wide toothed belt like they use on the airplane prop shaft reduction setups

[GeneralDisorder]

the weak link is the axles that said I wouldnt go threw all the work to get lower gears.

 

The axles will handle more than you think at nearly flat angles. They will handle the most load at near flat angles and slow speeds. The strength of the joint is proportional to the speed you run them at and the angle they have to move through. Thus lower gearing will actually save your axles - many people with t-case setups find they break more diff stubs than they do axles because of the torque applied to the stubs. A reduction at the wheels would help by moving some of the load away from the stubs. Different diffs and axles would help as well. And ultimately you would have to run a different transmission as the Subaru transaxles aren't designed to output that much load through the rear output.

 

GD

[Scott in Bellingham]

The axles will handle more than you think at nearly flat angles. They will handle the most load at near flat angles and slow speeds. The strength of the joint is proportional to the speed you run them at and the angle they have to move through. Thus lower gearing will actually save your axles - many people with t-case setups find they break more diff stubs than they do axles because of the torque applied to the stubs. A reduction at the wheels would help by moving some of the load away from the stubs. Different diffs and axles would help as well. And ultimately you would have to run a different transmission as the Subaru transaxles aren't designed to output that much load through the rear output.

 

GD

 

 

I have seen to many axles and stubs brake ea82s are stronger then ea81s but ive seen them both brake last time out I saw 4 brake

[GeneralDisorder]

I have seen to many axles and stubs brake ea82s are stronger then ea81s but ive seen them both brake last time out I saw 4 brake

 

Anecdotal at best. What angles are being run? How fast were they going? Were the axles new or already worn out? Etc, etc.

 

I'll state again - the strength of the axle is directly related to the speed and the angle. Run at flat angles and low speeds they are much stronger than the stubs.

 

Axle breakage, in large measure, is a result of people taking "running starts" at obstacles because they don't have the gearing to crawl over slowly. This puts enormous stress on the joints as they flex far beyond their design limits with lift kits of various shapes and sizes, and spin at high speeds with wheels hanging in the air, etc. It's angle AND torque (which can be equated to speed and inertia with formuli) that are important. High angles means the torque at which catastrophic destruction of the joint takes place is lower.

 

I've been there and done that - broken as many axles as anyone in the process. I've also studied the physics and the mechanical engineering aspects of the CV and DOJ joints used in the stock axles. I'm here to tell you it's NOT the axle's fault - it's how most people are using them. Granted there are better and stronger designs out there, but if you work within the limitations of the stock design you will find they are much more capable than they seem to be - only because *most* people are running them incorrectly in rigs that could be made correct with the proper changes to the suspension geometry.

 

GD

[TeamCF]

.... but I'm willing to try and possibly fail.... but I will have tried!

 

GD

 

 

And that is how we are going to push our Soob's limits just a bit further.

 

I've gotten caught in the "can't be done" rut. But at least giving things a shot could at the very least spawn a new idea, or inspire someone else to take it a step further.

 

 

I have an idea for if you ended up wanting to go with gears. At least to make it like the ones in the link I posted.

Not sure if they still have them or not. But last time I was down at Clackamas Steel thay had a couple crates of transmission guts. Lots of various gears and such in there. Just a thought.