Scale Model Shop

**nickedw** · 21 March 2024, 18:59

Originally posted by Jakko

For all I know, the differentials compensate for front-to-back differences in rotation speed as well as left-to-right?

Good info, the axles diffs physically (well mechanically anyway) can’t do that.

They split all of input rotation from the drive flange left and right. It’s the input to these diffs drive that further needs splitting front to rear, so in effect, they need to receive different input speeds (when turning) front/rear to further distribute left/right. So when turning you might send 500 rpm to the front and 490 to the rear, and 100% of both those inputs then gets subdivided left/right via the final drive ratios etc. so the diff can’t lose or gain anything, all it can do is apportion all of the received energy left to right, if it’s receiving either too much (or nor enough) a. It doesn’t know, b. It couldn’t do anything about it. The centre diff is doing the same thing at 90° so 100% of the engine power just gets divided up front to rear, mostly it does nothing much as front/rear rotational speed is matched when travelling straight, it’s when turning it kicks in.

**minitnkr** · 21 March 2024, 22:15

Many gearboxes/transfer cases have liquid couplings to reduce the effects you're discussing, also different ratios front & rear.

**nickedw** · 21 March 2024, 23:08

Here’s someone having the exact same conversation in the medium of Lego it’s just me that’s nuts then.

Conceptual differential layout for an 8x8

https://www.eurobricks.com/forum/index.php?/forums/topic/119292-conceptual-differential-layout-for-an-8x8/

I created a conceptual differential layout for an 8x8, just to see if it could work. It does it so far, even there is obviously still some minor tension happening between the axles. However it is better than not to have any center diffs at all. Any opinions?

**nickedw** · 24 March 2024, 06:34

I’m still making slow headway with this kit, theres a lot of cleanup, ejector pin marks, and removal of stuff for Eduard PE to do, so some more photos later.

in the meantime looking at my references, it’s time for my next stupid non-model question - why would you put a radiator (so you are trying to cool something down) next to the exhaust (the hottest part of the engine) am I missing something? It looks like it’s a cooler for the hydraulic oil that drives the winch motors etc

**nickedw** · 24 March 2024, 06:45

Originally posted by minitnkr

Many gearboxes/transfer cases have liquid couplings to reduce the effects you're discussing, also different ratios front & rear.

Interesting been reading up on that, makes perfect sense.

I’ve come across this technology for LSD stuff in the past, but hadn’t realised it was used like this too. I think the Ferguson system (as in Massey-Ferguson Tractors and Jenson FF) worked liked this. Now I've looked it up the Celica GT 4 Rally car had a viscous coupling centre diff too. Good stuff!

**Andy T** · 24 March 2024, 09:28

There looks to be a shroud on the back of that radiator, which possibly contain a fan, pulling air through from the open side of it and maybe cooling the exhaust a little as a side effect.