Which diff goes where for Kong?

[Juggular]

I assembled 3 differentials with varying hardness.  A: hardest, B: medium, C: softest. 

Softest will go to the front, because the front will make the largest arc when turning.  Where should the medium and hard go?  

 

Scenario 1--Dual steering)  The center wheels should get the hardest because the center axle would be the pivoting point.  After the front, the rear steering will get the next smooth diff.  Because it's closer to the center axle. it will need a bit less differential action than the front.   

Scenario 2--front steering only)  [A] If I think of Konghead as simply having 2 additional wheels to a 4 wheeled car, the rearmost wheels should get the hardest differential, just like a 4 wheeled car.  This seems inaccurate because the middle wheels are not idle.  Maybe it's similar to the scenario 1, where the vehicle kina turns on the center axle. Even though the rear does not steer, wouldn't they still make more arc than the middle?  Then middle set should get the hardest diff.  [C]  Maybe all of the middle and rear 4 wheels together could act like 2 rear wheels of a 4 wheeled car. Then the center and the rear diffs should have the same hardness?  I'm going to stop here, because I'm really confusing myself with a silly question that wouldn't make a whole lot of difference in real life.  

I can't make sense of it...  https://www.ijser.org/researchpaper/optimizing-the-turning-radius-of-a-vehicle-using-symmetric.pdf 

 

[GooneyBird]

The way I'd set it up:
4-wheel steering: medium front ánd rear, and softest in the middle. With 4-wheel steering the pivot point lies at the center axle, as the distance between all 3 axles is the same. So the front and rear axle are equal, in this regard. For a bit more traction coming out of a corner I'd actually try to put the hard-diff in the front. Might introduce a bit of understeer, but will be quicker all-around.

2-wheel steering: This is when things get interesting. Because the distance between the three axles is the same, I don't think that you can look at it like a semi-truck, where the pivot point lies between the two rear axles. It's a bit dependant on weight distribution, but I think that the pivot point will still be the center axle, and it will drag the rear around in corners. In this situation I'd still put medium up front, but I'd go softest in the middle, and hardest rear. This will allow more readily the breaking of traction on the rear, and could help with turn-in.

In reality though, I don't think any of this matter a single bit, as the suspension on the truck, and the play in the system, will be far more relevant to the handling than the diff hardness. Also, the tires probably don't have enough traction to actually be able to notice anything.

[MadInventor]

Just a quick point, the centre axle is not equidistant between the front and rear axle:

 

With the diffs you have I'd go softest in the middle as gooneybird says, then hardest in the back and the medium in the front. Under hard acceleration all the weight is going to be forced down onto the back axle, so that's where you'll want the most limited slip effect.

What I would do however is fit a Tamiya 53200 one way unit in one of axles (probably the front or the rear, depending on how you want to drive the truck). Fitting in the front axle you'll only have 4wd from the rear axles in reverse but it will improve the cornering and ensure you always have good traction on the front axle going forwards. (Also means that you will be able to achieve good handbrake turns with it) I've had a modified TT01 one way unit in the front of a TXT-1 for over 6 years and much prefer how it drives over the stock setup. Fitting one in the very rear axle will mean the truck will still have 4wd to the front and rear end in both forward and reverse, but the very rear axle will have proper LSD going forwards without compromising cornering.

[Nitomor]

Excellent tip that Mad Inventor. I didn't realise that part would fit that diff. Might experiment with my 4x4x4 WT01! It would also stop the WT01 4x4's from doing stoppies if fitted to the front!

I look forward to all the different setup possibilities on the G6-01 lol!

 

 

 

[Kingfisher]

1 hour ago, Nitomor said:

Excellent tip that Mad Inventor. I didn't realise that part would fit that diff. Might experiment with my 4x4x4 WT01! It would also stop the WT01 4x4's from doing stoppies if fitted to the front!

I look forward to all the different setup possibilities on the G6-01 lol!

 

 

 

On my 4x4x4 build, I locked the rear and kept the front open. Now, I am rethinking it, and am wondering if my crab walk will be weird. 

[MadInventor]

4 hours ago, Nitomor said:

Excellent tip that Mad Inventor. I didn't realise that part would fit that diff. Might experiment with my 4x4x4 WT01! It would also stop the WT01 4x4's from doing stoppies if fitted to the front!

I look forward to all the different setup possibilities on the G6-01 lol!

 

 

 

I haven't actually tried it in the diff housing, but I have been able to fit successfully fit 53200 in both a thundershot and a Mitsi Pajero metaltop wide, which use the same diff gears, so I see no reason why it wouldn't fit in these diffs.

 

[Juggular]

My silly question came from another unresolved question.... "how much limited-slip-differential is optimal?"  

It's not a settled question.  Subaru, Toyota, BMW... basically all the car companies that are making LSD are still wrestling with the same question.  Youtube tests show that all perform differently.  

It makes you wonder what you could do to your differentials, doesn't it?  

I found that differentials don't need to spin freely at all. In one full circle, outside wheel may turn maybe 60 degrees more, certainly not even one turn.  I'd assemble diffs stiff; my fingers would feel raw from trying to turn the drive cups. Then I'd put the car down on a wooden floor and make it pivot on the center part of the rear axle (like a tank spinning on its own axis).  It does fine.  To emulate ice and loose dirt, I'd lift the car somewhat to make it easier to slide.  Still, stiff diffs would work fine on less traction.  

3 diffs got me wondering what would Subaru engineers do if Subies came with 6 wheels.  The stiffest diff is at risk of losing traction if asked to differentiate too much.  In that sense, wouldn't it be safe to put it in the middle?  But of course, the rear gets the most weight in acceleration, so if one wheel slips at the rear, stiffest diff would be best also.  (I am still quite confused about all this...)