I Like to build middle scale PF AWD cars.

Always have a dilemma: with differentials or not. Now I am trying to find idea of rear live axle with possibility of locking (by hand). I tried many times, but did not find any compact and effective idea.

The main rules:

1) using differential of NEW type

2) wide of axle without wheels 13-15 studs

3) axle can be "suspended"

4) axle is compact and can be fitted without lifting body too high to be civill offroader

Please, mates, give any ideas

Edited January 1, 201312 yr by rm8

Why a differential of the new type? I think it's much easier to achieve with a differential of the older type.

Here is a idea that sariel came up with.

@ Alasdair noted, you can read more about Sariel's "3 Studs Wide Differential Lock" . He wrote that "It relies on the transmission driving ring, which is a rare part but very easy to engage/disengage. It’s so compact that the driving ring actually touches the differential case, but the resulting friction is minimal thanks to its smooth surface. The 16-teeth and 20-teeth gears are well meshed and capable of handling a considerable torque, while their ratio reduces the torque transferred to the transmission driving ring by 20%. I suppose the driving ring and the differential have similar torque resistance, but the driving ring is a much more expensive loss "

Here is a idea that sariel came up with.

Yes, but without 5x7 frame it is not so strong:(

You could of PM'd me and I could of edited my post.

Yes, but without 5x7 frame it is not so strong:(

You can add bracing easily enough too it.

Sariel also came up with this "Compact Axle With Differential Lock" design -- it is a "Simple driven, non-steered axle assembly with a differential lock, based on studless pieces. Building instruction included.

The following design addresses the problem of the new differentials being difficult to lock, and the older, easily lockable differential being difficult to use with studless pieces. This simple driven, non-steered axle is based on a studless 5×7 frame and allows to drive the differential with a 3:1 gear reduction. Locking is done by a transmission driving ring controlled with a 32039 connector, without the need for more specialized pieces such as the transmission changeover catch. The entire assembly is very compact and rigid, and the 32039 connector is less likely to snap over the transmission driving ring than other pieces.

Small pneumatic cylinder shown in the example is only one of several possible ways to control locking. While using pneumatics may be convenient when there are many suspended axles, as it allows to control them all from a single valve, and requires only connecting elastic hoses to them, it is also possible to use a motor – directly or, for example, with a small linear actuator."

I cant use old style diff because front axle is steered and also driven. Using 4L old diff at front is problem, because liftarm frames are for 3L diffs). Using old style diff at front axle also make front axles wider 2 studs tan with new style diff.

Using rear old style diff and front new style diffs simultaneously- impossible, cause when there is no central diff ( or when it is locked) gear reduction at axles will be different (24 old, 28 tooth - new)

Edited January 1, 201312 yr by rm8

I think your best bet is to use Sariel's diff lock with the new style diff and then brace it...

I cant use old style diff because front axle is steered and also driven. Using 4L old diff at front is problem, because liftarm frames are for 3L diffs). Using old style diff at front axle also make front axles wider 2 studs tan with new style diff.

Using rear old style diff and front new style diffs simultaneously- impossible, cause when there is no central diff ( or when it is locked) gear reduction at axles will be different (24 old, 28 tooth - new)

The mini turntable has 28 teeth too.

Apart from that: this was a problem I was pretty much unable to solve, but with an independent suspension, so the space was even more limited. But with a solid axle, it should be doable with Sariel's solution, you have plenty of lateral space, and I wouldn't worry about strength too much, the wheel on a simple Technic axle will be your bottleneck, not the suspended frame.

As also legomuppet9 said, best solution is sariels idea. I have used it on big trucks and then usually under heavy torque some gears slipped, but you build pretty small scale so i think on problems.

rm8, do you by any chance make instructions for any of your models? I have tried building in this scale, but it is so far beyond my skill set. In the case that you haven't made instructions, would you be able to post some more pictures of your smaller scale models? Thank you in advance, and happy new year!

Luke, in Canada

Hi i saw this Unimog around mid size scale u can see it has a new diff and diff lock pictures are here http://jaaptechnic.blogspot.nl/2012/03/unimog-u500.html

and here is a video

use a O frame because your differential easily slips without it.

build a difflock like this:

http://www.brickshelf.com/cgi-bin/gallery.cgi?i=5425237

and ad a axle 3 connected on a axle 6 with a axle switch on it as shown in the movie above.

use a O frame because your differential easily slips without it.

build a difflock like this:

http://www.brickshelf.com/cgi-bin/gallery.cgi?i=5425237

and ad a axle 3 connected on a axle 6 with a axle switch on it as shown in the movie above.

My old idea is similar to your.

http://www.brickshelf.com/cgi-bin/gallery.cgi?f=481750

But your axle is better and compact.

Thats what I want to build:) thank you.

But i will combine your and Sariel's ideas to minimize gears:)

Your gearing way to locking axle is 16:16:16 and I will try 20:16, like Sariel do.

Edited January 3, 201312 yr by rm8

Night was succesfull:

Very strong, no deformation on heavy load, friction is minimal. Locking is controllable by 12 bevel gear.I like it.

nice! very small!

i will link it on my site

Thank you. But it need some optimization for minimum part count/complexity. You can try to optimize it, guess you understand main idea of my construction:)

Thank you. But it need some optimization for minimum part count/complexity. You can try to optimize it, guess you understand main idea of my construction:)

i will give it a try!

when i have time...