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20 minutes ago, Teo LEGO Technic said:

Sweet truck! Very nice system for the front axle, I saw the same portal axles used by Functional Technic on his Unimog, they're very compact and sturdy https://www.functionaltechnic.com/2020-08-30/unimog-406-with-diff-lock-and-portal-axle

Thanks you very much, yes those portal axles are very compact and study, the only problem is the turning circle radius.

 

24 minutes ago, Teo LEGO Technic said:

I can also probably stick an XL in each and see if it holds. :wink:

It seems lots of people use pneumatics for diff locks, that might be something I should look into. :thumbup: 

Really good ideas.

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8 hours ago, 1gor said:

I don't know if you have pair of defender wheels (and if portal axles hub from 8110 set fits in it); that could (perhaps) help you to gain stiffness

Those portal axles sort of fit in the defender rims. They do rub at the top, so some may not prefer it, but I'm personally fine doing it, and have done it in a Zetros MOD I have yet to post.

 

Also, are you sure you can't do the "old-school" diff lock with the new differential? In my experience it rubbed just a little, but was (in my opinion) workable.

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Great choice for a moc, lol, I am currently working on a very similar model myself, although I have decided to omit many of the features you will be using, for now. Mostly just so I will actually complete it, rather than quit in disgust as often happens with my mocs.

I am having a hard time with steering right now, having decided on a large actuator for the control. So I will be following with great interest.

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On 8/14/2021 at 7:14 PM, 2GodBDGlory said:

In my experience it rubbed just a little, but was (in my opinion) workable.

It may work, but the issue is the triangular shape of the diff causes uneven friction, which will be a worse issue for the MOC at higher speed (when the gearbox is in higher gear). 

On 8/14/2021 at 9:46 PM, Johnny1360 said:

I am having a hard time with steering right now, having decided on a large actuator for the control. So I will be following with great interest.

It's a challenge for sure, hopefully I have a solution for you soon :thumbup: :thumbup: :thumbup:

On 8/14/2021 at 10:33 AM, 1gor said:

I don't know if you have pair of defender wheels (and if portal axles hub from 8110 set fits in it); that could (perhaps) help you to gain stiffness

I don't sadly, gonna have to work with the regular rims.

BTW more examples for driven, steered, diff locking axle builds are welcome!!! Thanks @Lukes_Brick_Studio for your input so far :wink:

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So here's the current progress. The front axle continues to be a challenge, but once I figure it out, the gearbox, diff lock mechanism, and chassis will be relatively easier. As far as the steering axle is concerned, I've broken it down into drive, steering, and differential lock, to investigate and compare my options:

Drive:

  1. New differential in a 5x7 frame 
  2. Zetros style, without frame, and geared on the side to allow space to for the clutch to enter the differential on the side

Of these two options, I chose the 5x7 frame, because I want the perpendicular gears to be as secure as possible to take the toque I'm planning to put on it.

Steering:

  1. Using an actuator:
    1. Small actuator - more space efficient, but has to be within two studs of the wheel hub pivot centre in order to have enough range of motion 
    2. Large actuator - takes up A LOT of space, but can be much stronger, and has much more travel
  2. Worm gear - use a rack and pinion connected to a worm gear 

Either way, the motor powering the steering can either be on the axle or chassis. Of these options, the large actuator simply takes up too much space, so I plan to go with either the small actuator, or the worm gear.

Differential Lock: (given 5x7 frame)

  1. Clutch:
    1. "Classic" lock system with clutch directly connected to differential causes some friction between diff and clutch, but is workable like @2GodBDGlory said :thumbup:
    2.  Use more gears to push the clutch further out, and have less friction 
  2. Clutch movement:
    1. Small pneumatic actuator
    2. Zetros - style with orange screw piece 

Of these choices, all are available, as none have any clear advantages or disadvantages. 

My one question to you guys is: what do we think of reducing the gear ratio further after the diff, and increase the ratio before the diff, to take pressure off of it in terms of torque? Is this worth the effort, or does the added friction and complexity not make it worth it overall? Hope I haven't rambled on too much :grin:

 


 

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Use the small actuator. Wormgear will be slow AND if you oversteer it, it'll break the model because it won't stop. the small actuator has a clutch to prevent this. 

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Posted (edited)

After a lot of prototyping (and I mean a lot :rofl:) I finally have a working version that is pretty close to the final version of the front axle. Drive is using the new differential, in the 5x7 frame for maximum strength, steering is using a small actuator, placed at 2 studs from the pivot point for sufficient steering range of motion, and differential lock is using a clutch operated by a small pneumatic piston, shifted away from the differential with two sets of gears, to eliminate friction between the clutch and the differential hub.

The portal axles are secured very well, both top and bottom, and the only thing still needing some work is some reinforcement on the gears at the front that transmit power to the M-motor for steering to prevent slipping, and some work on the diff locking system, perhaps strengthening it or moving it in a new position to increase ground clearance.

Thoughts? :classic: :classic: :classic: 

800x449.JPG

800x449.JPG

800x449.JPG

Edited by Teo LEGO Technic

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My friendly advice is to try to make additional bracing for those gears used with small linear actuator.

At least on blue 20 toothe double bevel gear with clutch put bushes and axle with stop instead of pin ...

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Posted (edited)
16 minutes ago, 1gor said:

My friendly advice is to try to make additional bracing for those gears used with small linear actuator.

For sure yeah, it's currently slipping under pressure so I was planning to strengthen it. :wink:

Do you have an idea for a better diff lock setup? If it was more compact, I could turn flip the axle around and that would remove the need for the gears entirely, just stick the M-motor directly into the actuator following the perpendicular gears. As it is, the diff lock system protrudes too much and would ruin the truck's approach angle if it was at the front. 

Edited by Teo LEGO Technic

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On 8/17/2021 at 12:11 PM, Mechbuilds said:

Use the small actuator. Wormgear will be slow AND if you oversteer it, it'll break the model because it won't stop. the small actuator has a clutch to prevent this. 

This has not been my experience.  Wormgears have been successfully used by others with no problems for steering.  I mean, once you hear a change in the motor pitch as long as you stop you should be okay.  If you keep power going and going, sure, it will break, but there is sufficient warning for you to stop....

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For differential I have only idea to put itside frame, but honestly I didn't try it...

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15 hours ago, nerdsforprez said:

This has not been my experience.  Wormgears have been successfully used by others with no problems for steering.  I mean, once you hear a change in the motor pitch as long as you stop you should be okay.  If you keep power going and going, sure, it will break, but there is sufficient warning for you to stop....

yeah but with a linear actuator it doesn't matter if you hold the button for too long as it won't damage anything. 

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Hi guys
@Teo LEGO Technic saw your e-mail and thought it’s better to answer here. I disassembled the Unimog already a while ago. But I made some renders for you of the front axle if you still want to use it for your model. the steering angle is with Lego always a problem if you want to have propulsion in the front axle and that is due to the old and new cv-joints. You cannot change that but only if you use cardan joints. In my opinion cardan joints do not fit for steering in front axle because of the pivot point of the steering axle. In real cars the pivot point of the steering axle is close the middle of the tire if you look on the tire from above. With Lego it is normally outside of the tire like in my axle. with cardan joints it is even further away from the tire. Another problem my axle has is that you cannot use Lego wheel hubs if you want to have a portal axle and keep the pivot point of the steering axle close to the tire. Without a Lego wheel hub, the tire is more lose on the axle but turns better. Now everybody has to decide how you choose. The performance you can see in my video of the Unimog.
Regarding how you can make diff-lock: With pneumatics it is easier on the axle but you need in the model a compressor and valve. With mechanics like in the Zetros form Lego it is much harder on the axle but easier in the model an you need only one motor. With pneumatics you need at least on motor if you use a auto-valve on otherwise two motors.

axle_portal_diff-lock_15.1.png

axle_portal_diff-lock_15.2.png

axle_portal_diff-lock_15.3.png

 

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