pic: Don't do this. It's a bad idea.

[Michael Blake]

Originally Posted by squirrel

Here's a much better explanation.....but then, I do like old stuff

http://www.youtube.com/watch?v=F40ZBDAG8-o

NOW, _that_ was helpful... ;-) THANKS, Jim!!

[Michael Blake]

Originally Posted by EricH

Short version: If both can go the same way at the same speed, both go the same way at the same speed. But if one of them can't keep that speed up, then it doesn't have to due to the way the differential is set up.

So, where's the "slippage" provided in this setup?

THANKS!

[Hawiian Cadder]

Why not choose pneumatic tires over the suspension? I don think you would get much "play" before the bevel gear bottoms out.

[Cuog]

Originally Posted by Michael Blake

So, where's the "slippage" provided in this setup?

THANKS!

There is no "slip"* in a differential. The nature of how the gears mesh is what allows the shafts to turn at differing rates. The differential itself has no control over the situation, its just along for the ride.

*(unless we start talking limited slip differentials and lockers etc)

[EricH]

Originally Posted by Michael Blake

So, where's the "slippage" provided in this setup?

THANKS!

In the differential gearing. Two of the 4 gears in the inner box are connected to the wheels; the other two are idlers. The relative speed of the wheels doesn't really matter to the idlers; they'll move as fast as they need to.

Hint: Think of this setup as 2 gearboxes. The inner box is the 4 in the middle of the "axle"; the outer is the bevel at the top and the large gear it meshes with.

[Michael Blake]

Originally Posted by EricH

In the differential gearing. Two of the 4 gears in the inner box are connected to the wheels; the other two are idlers. The relative speed of the wheels doesn't really matter to the idlers; they'll move as fast as they need to.

Hint: Think of this setup as 2 gearboxes. The inner box is the 4 in the middle of the "axle"; the outer is the bevel at the top and the large gear it meshes with.

Also, helpful... THANKS, Eric!

[lemiant]

Originally Posted by EricH

Actually, Michael, lemiant didn't have a chance to read squirrel's link yet. I would suggest reading that link, then figuring out the drive system.

Short version: If both can go the same way at the same speed, both go the same way at the same speed. But if one of them can't keep that speed up, then it doesn't have to due to the way the differential is set up.

I hadn't. I thought the big bevel was attached to the shaft not the box. After reading that article I understand, and am amazed!!!!

[Tristan Lall]

Wouldn't this work better with constant velocity joints (rather than universal joints)?

And are you using the universal joint as two of the members in a four-bar linkage that holds up the wheel? If so, isn't it just going to deflect to the maximum? (Or am I missing a spring somewhere?)

This would be a fun stock design to keep around...just to tempt people when FIRST decides to give us some real obstacles.

[AdamHeard]

Originally Posted by Tristan Lall

Wouldn't this work better with constant velocity joints (rather than universal joints)?

And are you using the universal joint as two of the members in a four-bar linkage that holds up the wheel? If so, isn't it just going to deflect to the maximum? (Or am I missing a spring somewhere?)

This would be a fun stock design to keep around...just to tempt people when FIRST decides to give us some real obstacles.

I Agree with your complaints about suspension geometry.

Also, The suspension on this seems to indicate a purpose of driving over varied terrain. With the completely open differential on there, the wheel with less resistance (often in the air, not making any contact) will get all of the rotation, leaving a torque on the static wheel equivalent to just the friction in the differential.

[Hawiian Cadder]

Originally Posted by AdamHeard

I Agree with your complaints about suspension geometry.

Also, The suspension on this seems to indicate a purpose of driving over varied terrain. With the completely open differential on there, the wheel with less resistance (often in the air, not making any contact) will get all of the rotation, leaving a torque on the static wheel equivalent to just the friction in the differential.

true, maybe you could use a limited slip differential to prevent that.

[PAR_WIG1350]

Originally Posted by AdamHeard

I Agree with your complaints about suspension geometry.

Also, The suspension on this seems to indicate a purpose of driving over varied terrain. With the completely open differential on there, the wheel with less resistance (often in the air, not making any contact) will get all of the rotation, leaving a torque on the static wheel equivalent to just the friction in the differential.

The suspension Appears to actually a three bar linkage with the link from the wheel bearing retainer to the differential frame being a spring loaded variable length link (possibly a gas shock). The u-joint is simply the joint between two links. It would benefit from more support, but the geometry should still work.

Also, by linking the axles with a slip clutch between the output gears of the differential the static wheel issue could be resolved. Like this. basically it's a primitive version of the limited slip differential.

[MrForbes]

That method of using the axle shaft as a suspension locating member was used on some IRS cars for years, including the Corvette starting in 1963

[Cuog]

Originally Posted by squirrel

That method of using the axle shaft as a suspension locating member was used on some IRS cars for years, including the Corvette starting in 1963

Also known as a "Swing axle"

First on this list: http://www.autozine.org/technical_sc...uspension2.htm

Also used on VW Beetles(busses, and most other models including porsche) 38-68