First PF 4x4

[T_Tank]

This is one of my first 4x4 I've been trying to complete with the new PFs.

Basic functions

-1XL motor driving a 16t to 16t using technic conveyor links (don't have normal chain links >.<) that then drives a 8t to 24t differential

-1M motor for running a mini LA directly to pull an push a older pneumatic piston (will be replaced with a newer one likely to be modified for running water or RC shock oil in)

-1M motor running a auto valve to open an close the center diff locker.

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Things to be done

-Improve drive train gear ratio make it more torque oriented

-Create proper 4link connected live axles

-Build a truck body maybe a 80's F150 or Chevy

On each side of the V6 engine is the M motors...Hopefully this will help with weight distribution

The auto valve that runs the small bidirectional piston for the center differential locker

Its probably unusual to see the lego conveyor links being used to actually drive the gearbox but I'm trying really hard to work with what I have

This piston does work but its over 14years old an I think a member on the forum had issues with hydraulic steering with older seals leaking all over the place

edit---

Forgot to mention I'm having a issue with making 4 link suspension that doesn't swing side to side excessively causing dog tracking (NOT GOOD >.<) an I want to see about putting the newer diffs in the axles an implementing a pneumatic locker for each axle aswell

Edited February 28, 2011 by T_Tank

[AndyCW]

It is important not to try articulating the link to it's extremes.

The closer a link is to its extremes shortens its effective length and causes the undesired steering feature. I used the longer links which allow more travel before they do this. I also made it a point to set the ride height so that the link was nearly parallel to the ground and when the suspension was fully compressed the link was nowhere near its available travel. (I'm not sure if this is very clear?)

We approached the design from different directions. I designed my axles, suspension, and frame first and am currently working on the drive train.

I like the mLA connected to the pneumatic cylinder to function as the "orbital" valve for the hydraulic steering. Can't wait to see how that turns out for you.

[T_Tank]

I did finally figure out how to set my links so they won't dog track. ATM I'm fiddling with some 6L links though I think the longer 9L ones would work better for a longer wheel base. An I do have a test axle made though it desperately needs a redesign they spread apart to easily will have to look an see how some other folks made their axles work an try to implement a diff an locker. Its kinda hard for me to atm order or buy sets for parts cause I'm saving up for a 3week vacation in Europe which I'm excited about since it will be my first time out of the USA.

Also I know this is probably overly complex for a truck trial like vehicle but I tend to think in a over complicated manner doesn't help that I've also spent a year at a technical collage learning about large diesel chassis an engines

[AndyCW]

With you links so close together in the vertical plane they are not very able to resist the torque reaction of the axle. There are 4 studs between my upper and lower control arms and I still get some caster change between power on and power off.

If you can get that pneumatic locker to work and be robust I may have to borrow that idea.

[T_Tank]

Ya I figured I need to space the links vertically more to make them work more reliably. I'm gonna try a few ideas with the axles in the next few days really like to make the axles as strong as possible while being easy to make into a steer axle for the front (only have 1 free u-joint atm >.<)

[T_Tank]

Update new axle concept finished used axles to make the internal structure an then added the outside area supports its very sturdy still need to figure how to mount the pneumatic locker piston onto the axle. At the moment I'm very happy with these axles, although I have found there is a defect with the 8t bevel connecting to the 24T on the diff on the side where you load the smaller differential gears that the tooth mesh there Isn't enough to keep the 8T from slipping on all the other spots of the 24T gear it meshes perfectly an doesn't move out of place. Anyone else find this issue with the newer lego diffs? I'm slightly tempted to make a axle using the older generation diff but that will make the axle alot clunkier. >.<

[Aqualize]

Update new axle concept finished used axles to make the internal structure an then added the outside area supports its very sturdy still need to figure how to mount the pneumatic locker piston onto the axle. At the moment I'm very happy with these axles, although I have found there is a defect with the 8t bevel connecting to the 24T on the diff on the side where you load the smaller differential gears that the tooth mesh there Isn't enough to keep the 8T from slipping on all the other spots of the 24T gear it meshes perfectly an doesn't move out of place. Anyone else find this issue with the newer lego diffs? I'm slightly tempted to make a axle using the older generation diff but that will make the axle alot clunkier. >.<

*pics*

Sorry but I don't understand what you're writing about slipping gears. Do you really mean 8t and 24t gears? You don't have those in your differential, only in the final gear reduction close to the wheels. What am I not getting?

Btw I like started building with the same "hub reduction" as you a few days ago (but using the 6-hole "rims" all the way, no bushings and with axles through all the holes in the wheel's rim). But in an earlier project I made a differential lock that was very big (clumsy), your variant is more compact. I will probably use that one if I need a differential. In the project I'm doing now I skipped the differential. But perhaps I should redesign.

[T_Tank]

its the 24tooth gear on the differential housing itself that slips on the side where you put the 3 12tooth bevels inside it (has grooves for the outer sides to slide in but not to fall out through the bottom). I do like how lego did make the newer differential smaller compared to the older generation one thats actually used for my central diff.

[Aqualize]

Well now I see. That new differential is actually a 28 tooth one. http://www.bricklink.com/catalogItem.asp?P=62821

That older one has 16t and 24t (the one used in the central differential).

I also like the new differential. Mainly because it can be placed inside one of these:

http://www.bricklink.com/catalogItem.asp?P=64179 (the 64178 can also be used).

And then you get a very strong frame around it.

I'm away for the weekend from my lego parts to build with... at least I here have my completed 8868 to look at :)

Edited March 6, 2011 by Aqualize

[DLuders]

In this excellent TechnicBRICKS article, Conchas had noted that, starting with the 8297 Off Roader II set, the new differential was smaller than the older ones. Not all of the pictures in that article appear below (because they are big), but here are the words regarding the differential:

"With the new Off Roader, there comes also one differential with a new design. This new design is also the 3rd generation of the LEGO TECHNIC differentials, as illustrated below:[/color]

At center the first generation from 1980, on the right the 2nd generation from 1994 and on the left the new design (2008).

Again the new differential is smaller than its predecessor (3L wide in opposition the former 4L version), however it uses inside the same 12 teeth bevel gears as before (only the 1st generation used different ones).

Because it is thinner, both clutch gears (16 and 24 teeth) on the previous design have disappeared... which may mean that the new differentials can't be blocked anymore!?

Instead, it got a 28 teeth bevel without clutch.

The other extreme got no gear but its design with four inner tabs, suggests there is still an hope for a future clutch mechanism, despite it is incompatible with actual Driving Ring and Driving Ring Extension. Lets see if LEGO designers have new Driving Ring on the way for the future, to address this issue.

The differential 28 teeth gear, has a few shorter teeth...because of a mystery slot... the wider (shallow) slot is for the present bevel gears but the deeper narrow slot is for something else... (it is too narrow for a linkarm). Because of the slot, the bevel gears only go in from one side and don't drop through!

As bevels tend to slip quite easily, the shorter teeth can make this even worse... Lets wait and see what other users will report about this new part.

The new design has other disadvantages,

•It only interfaces it other bevel gears, which forces transmission to be perpendicular.

•Can't be used with a chain.

•Can't be used with standard or worm gears.

With all these limitations, hopefully this won't be the only differential in use by the LEGO TECHNIC Designers, for the future...

As AVCampos wrote in a comment to another post, lets hope "this new differential won't completely replace its predecessor, but rather supplement it where size matters".

This new differential easily meshes with a 20 teeth double bevel, as in the present Off Roader design.

In the central part of the differential, we can see a block that prevents internal bevel gears from bending, which used to make them slip and lead to breaking gears."

[T_Tank]

Dlunders post sums it up what I'm having issues with an ya sorry about getting the tooth counts off embarrassed about that >.<. The shorter teeth don't mesh right an cause it to slip at that one an only point. Also that square box liftarm softa works for I did try using one for a axle but it wasn't wide enough to add the gears to the sides to make it possible to use a locker -based on Sariel's idea for a 3stud wide locker found here 3studs wide Diff locker - Now I'm thinking with both axles running with the center diff locked an the diffs not synchronized at that flat spot I should be able to stil operate it I'll unfortunately find this out after a couple of months saving an packing for a trip. But if anyone here has some ideas to improve the concept some that be great.