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My kid asked if we could make a giant tractor out of Lego. So I set out to work on something that should be satisfactory. I don't have the Claas tyres so I had to settle for Unimog tyres but maybe I'll buy some Claas tyres some day.

I haven't done much MOCing in Technic, especially vehicles of my own design so it's interesting to see how this project turns out. So far I've finished the chassis, with independent suspension on all wheels, steering and rear axle drive. I've routed both steering and driveshaft along the centerline, and where they cross, there's a red idler gear to transmit driving while steering shaft goes through that gear. I intend to make the exterior brightly coloured and toy-like, but I don't have a clear picture in mind how it'll look like. Though I planned to use yellow and black banana gears as mudguards.

Bottle for scale.

HV1VwPx.jpg

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After some real-world testing (=letting my kid play with this) I came to the conclusion that the front wheels are not nearly strong enough and the suspension needs to be redesigned. I had used the design by @Zerobricks mentioned in here: 

But it's not strong enough against torsional stress, if the suspension is compressed while the wheels are turned, the wishbones twist too much and parts tend to get loose. The core of the problem obviously is the steering pivot, which is between the wheel and the chassis and not inside the rim. So I set out to design steering/suspension assembly that would have the pivot point closer to the wheel and perhaps be stronger against torsional stress. I found some inspiration here: 

But that's of course entirely different kind of suspension, so I had to modify it heavily in order to fit it to my vehicle. Here's a few photos on what I came up with (work in progress):

traktori_1.jpg

traktori_2.jpg

traktori_3.jpg

The steering pivot is at the inner edge of the wheel, and when pressing from the middle so that the springs fully compress, nothing gets loose or pop out. I haven't yet attached it to the rest of the chassis so real-life testing still awaits, but if anyone can spot any obvious flaws, it would be nice to know before further work.

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I had a hard time thinking of how to comment on your suspension. Do me a kindness and take it apart, please. The geometry, or more precisely the complete randomness of it, hurts my eyes. Best scenario is to go back to @Zerobricks design and just make it stronger, not massacre it. Sorry. The moment you put any serious weight on it, things are going to explode.

Edited by Sariel

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7 hours ago, Sariel said:

I had a hard time thinking of how to comment on your suspension. Do me a kindness and take it apart, please. The geometry, or more precisely the complete randomness of it, hurts my eyes. Best scenario is to go back to @Zerobricks design and just make it stronger, not massacre it. Sorry. The moment you put any serious weight on it, things are going to explode.

No it doesn't explode, not even when placed on the ground and compressed so that the springs bottom out, nothing loosens, though the differential should be located lower as the CV-joints are over their limit when the suspension is not compressed. I already did some modifications though, mainly to how the suspension arms connect to the center, but that's mostly aesthetic fix. I tried to make Zerobrick's design stronger but couldn't, there's just too much play in the wishbones considering the distance of the steering pivot to wheel.

The main problem I set out to solve here was making a suspension with portal hub that would allow the steering pivot to be located near or inside the wheel, and I'm sure my design could be improved, but random or not, somehow it appears to work at least to some extent.

12 hours ago, Magical Duck said:

Wow, that is quite complex! How sturdy is it (there are a lot of small connections)?

Surprisingly, but probably not enough. We'll see when the real-world testing commences.

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Aren't your 'king pins' on different planes? Surely it doesn't turn... hard to tell. Many parts make it confusing!!

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given the thread title, I was expecting to see something like this

 

 

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Hi

If you want a good, strong portal suspension with a good pivot point, I suggest you look at the one I used in the Tiger 6x6 which uses the rims from 42110.

 

 

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I'd say you are in trouble with that front axle.  If you want something that will bear weight, then put in a solid axle with a centre pivot.  This will allow you to use the portal hubs and minimise the offset in your steering.  It will make the steering lighter and easier to turn.  Once you have that sorted out, then you could spring your front axle to the main chassis.  This is how most tractors are still built.  Complex suspension is not everything, especially if your steering does not turn, or ends up exploding.

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5 hours ago, howitzer said:

No it doesn't explode,

It might not explode, but it looks like many parts will be stressed too much if the suspension is compressed. Could you make a video which shows the suspension compressed? I'm also keen to see the steering in action.

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Just to be clear though, which 'tractor' are you looking to build? Something more similar to 42041 or 42054? I'm just thinking that if it's the latter, you could make your life a lot easier by substituting those springs for a pendular system.

That LPEPower axle is one of the most densely complex things I've built, but I've only now noticed that there's something about these pivot angles - similar to those used in that design - that my brain is rejecting

EkkpWp3.jpg

Though I can verify that, while the design may not have been perfect, it didn't explode.

 

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5 hours ago, CrankyCraig said:

Just to be clear though, which 'tractor' are you looking to build? Something more similar to 42041 or 42054? I'm just thinking that if it's the latter, you could make your life a lot easier by substituting those springs for a pendular system.

That LPEPower axle is one of the most densely complex things I've built, but I've only now noticed that there's something about these pivot angles - similar to those used in that design - that my brain is rejecting

EkkpWp3.jpg

Though I can verify that, while the design may not have been perfect, it didn't explode.

 

I'm building a kid's toy with a specifications "giant tractor" :D so there's really no definite form I'm aiming at. But I want it functional and sturdy enough to withstand play without constantly needing to fix parts of it, and that's where Zerobricks' otherwise nice design failed. Pendular axle would definitely be better, but I don't have parts (Unimog balljoints) for that so I'll have to stick to independent suspension for now. I have one more idea on how to make do with the portal axles, but if that doesn't work out, I may have to just ditch them and try something else. Unless someone can think of a way to build a sturdier design using portal axles. I did some searching on Eurobricks without finding anything usable though, so I don't have high hopes.

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Well, I would imagine that a kid would more typically refer to a farm tractor when referring to a tractor, which usually have basic (if any!) suspension, so that should make your life a bit easier. You wouldn't necessarily need the unimog balljoints, you could use a couple of turntables - big or small. 42030 had pendular rear suspension, and it was made without any of those pieces.

However, if the brief was 'giant', you have to go much, much BIGGER! :grin:

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53 minutes ago, CrankyCraig said:

Well, I would imagine that a kid would more typically refer to a farm tractor when referring to a tractor, which usually have basic (if any!) suspension, so that should make your life a bit easier. You wouldn't necessarily need the unimog balljoints, you could use a couple of turntables - big or small. 42030 had pendular rear suspension, and it was made without any of those pieces.

However, if the brief was 'giant', you have to go much, much BIGGER! :grin:

There was also a wish for it to be "bouncy" so I guess that calls for a suspension. And for a crane arm like that of the MB Arocs. I've got to see what I can do about that...

Earlier iterations had enough bounciness, now I just have to figure out a way to make it sturdier. Turntable solution could be usable, thanks for the idea. I'll try it later if my current vision doesn't work out.

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This is an ultraheavy-duty pendular axle I designed a couple of years ago. The springs are mounted on a pivot, so you get around four studs of suspension travel on either side.

640x457.jpg

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8 hours ago, suffocation said:

This is an ultraheavy-duty pendular axle I designed a couple of years ago. The springs are mounted on a pivot, so you get around four studs of suspension travel on either side.

640x457.jpg

Interesting, how much ground clearance it allows?

I rebuilt the whole suspension assembly, and now it at least feels much better. Here's some photos:

traktori_4.jpg

traktori_5.jpg

traktori_6.jpg

The only problem I can see with this build is that when the springs are bottomed out, the axle touches the connectors between wishbones and steering pivot:

traktori_7.jpg

I guess I could move the differential up a stud, which should solve this issue. Any comments?

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2 hours ago, howitzer said:

Interesting, how much ground clearance it allows? 

Two studs with Unimog tyres, three with Claas tyres. You could gain another stud by using small turntables instead of large ones. Obviously, since the suspension is pendular the clearance is constant.

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5 hours ago, howitzer said:

The only problem I can see with this build is that when the springs are bottomed out, the axle touches the connectors between wishbones and steering pivot:

That happens for a reason. The reason being: you're still ignoring the geometry completely and trying to murder your axles as result. The 3 arms I have marked SHOULD ALL BE OF EQUAL LENGTH. And to make things worse, the parts I've marked with yellow rectangles are angled so they're effectively less than 3 studs long, which messes up the geometry even worse. I understand you're just building a toy for your child but it really doesn't take much effort to stop trying to break LEGO pieces in process. If your car had suspension like this, it wouldn't last two turns:

https://pasteboard.co/JdO1IC4.png

Edited by Sariel

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Man @Sariel is toxic. 

So much criticism but no actual solutions offered. Basically pointless comment. 
If it takes no effort then why not post a solution. 

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11 minutes ago, Mechbuilds said:

So much criticism but no actual solutions offered.

I literally drew the problem on the pic and described the solution (and that's second time I've done it in this thread, BTW). Sorry for trying to help and not making such insightful, helpful comment as yours. I sometimes forget that the only activity allowed on EB is patting each other on the back.

Edited by Sariel

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4 minutes ago, Sariel said:

I literally drew the problem on the pic and described the solution. Sorry for trying to help. I sometimes forget that the only activity allowed on EB is patting each other on the back.

Com'on @Sariel.  Not true nor accurate.  Plenty of helping and constructive criticism on EB without needing to be snarky.  

I love your stuff.  I love your contributions... but lets be honest....unless you are posting your creations, your reviews, or some solution you created your postings are minimal.  You rarely, if ever comment on other's MOCs, despite your talents don't participate or even vote in contests, etc.  And then you post a series of snarky posts for this one thread.  Rife with sarcasm and an aire of superiority.  Why someone so talented as yourself chooses to single out this thread they way you have is beyond me.  There are plenty of GREAT builders out there that don't show such arrogance.  And then try to package it in this "trying to help" wrapping and play the victim?  Man... just stop.  

I have loved your stuff for a long time. Still do and I support it.  All while knowing there is a good dose of arrogance in your work.  I accept it.  But man, that arrogance really is showing in this thread.... you might want to tuck that *&#$% in.   

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One thing that's bothering me about this build is the rear axle lifting up the chassis. Traditionally tractor bodies are completely level and the suspension is minimal. You're putting too much effort into that. Focus more on a system that can power implements, or distributing the weight better.

Edited by Maaboo35

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12 minutes ago, nerdsforprez said:

.unless you are posting your creations, your reviews, or some solution you created your postings are minimal.  You rarely, if ever comment on other's MOCs, despite your talents don't participate or even vote in contests, etc.  And then you post a series of snarky posts for this one thread. 

Didn't know that 2 comments constitute a "series". Yes, I'm getting discouraged again and again from commenting here because any form of criticism, however mild, is unwelcome on EB. To the extent that you guys fail to help others because helping would mean pointing out some errors. Until my first post here literally the only comment was "Wow...", whereas the author of this thread obviously needed help. But no, not here. I actually remember some builder showing his crane model a while ago, which was pretty decent, but the author kept misspelling "outriggers" again and again. And it went for 2 or 3 pages if I remember correctly, with not a single soul offering a correction because that would be IMPOLITE. I'm nowhere near being arrogant, I'm just dead tired of your endless drama whenever a comment is posted with anything other than praise in it. Come to think of it, I think it's pretty arrogant to be able to help someone correct their errors but deciding to look the other way. And yes, my first post sounded unpleasant, but look at the pic it was referring to. I'm pretty sure that most people viewing it had the same thoughts I did, they just remained silent.

Be honest, you don't want me commenting on EB, you just want me shoveling praise left and right. Anything other is considered unsavory.

Edited by Sariel

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