Non-Newtonian differential fluid????

[Raymond Glover]

Hi - I have a 222 I am building, albeit slooooowly. My wife is an engineer and had an idea about the differential fluid. She was wondering if anyone has ever used a non-newtonian fluid such as cornstarch/water. These are fluids that act as a liquid when something passes through them slowly, but act more like a solid when something hits them at high speed. The reasoning would be that if the diff slips at rapid speed, it would be more viscous and then as the non-spinning tire tire grabbed and went slower, the resistance would decrease to save energy and heating.Has anyone tried this? I plan to try it as soon as I get to that part of teh kit.
Anyway, it will be an interesting experiment. Perhaps sloppy too.

Also, thanks to all the contributors on the forum, I always learn so much and enjoy looking at all the models.
Cheers,

Ray Glover - Ft Hood Texas, USA

[Adrian Harris]

A very interesting concept and certainly worth a try

Is the change of state progressive

I've seen non-newtonian fluids which go "rubbery" when subjected to shock but I'd be interested to see how it will react to being crushed between the teeth of the four gears inside one of these differentials

Adrian

[Adrian Harris]

You can buy Hyper8 differentials on eBay quite cheaply, so it might be worth buying a spare and filling that.

You could test it by clamping one axle in a vice and driving the other with something like an electric screwdriver which has a variable speed facility.

You should be able to gauge the state of the "fluid" by the stress placed on the screwdriver.

Adrian

[Fabrice Le Roux]

Hi Ray,
It's a fun idea and one I puzzled over many years ago when I built the Tamiya Hilux R/C truck. Aside from the awful cart-sprung suspension (which never worked that well) the open diffs always seemed to get "crossed" at just the wrong point in the rough. The freewheeling hubs were neat though..
I came to the conclusion that some real-world mechanisms just don't scale down. Even if you create a 1/6th scale Viscous LSD (no acid involved!) and use silicon oil from an RC Buggy shock set up, the surface area between the clutch plates will be just too small. What have appeared are small electrically locking clutches/brakes, still too large to fit inside a Robbe diff but possibly useful for a centre diff lock design.
Fully locking differentials have always been an acceptable solution for when the going gets really bad anyway.
Have fun.
BTW Custard also exhibits some Non Newtonian Fluid characteristics..
cheers,
Fabrice

[Adrian Harris]

> BTW Custard also exhibits some Non Newtonian Fluid characteristics..

It have to be cooked until DunkelGelb though

Adrian.