My 8x8 Project

[Mechbuilds]

Hi guys! 

I've decided to scrap everything what i was doing and focus on this 8x8 project.. 
The axles are exactly copied from sariels tatra but i've put on some modifications.. 

The wheels are all locked with no differentials and the motor is direct drive 1:1. (subject to change)
I'm currently waiting for a load of parts and soon more. So progress is at a snails pace. 

Features:
8x8
4 wheel steering
RC
Rock crawling abilities (lots of suspension travel)

Here are some pics:


Chassis with motor mounted:


Rear axles


Steering axles:


Bottom:




Next i need to tackle two things: 
A steering mechanism that works.. (all 4 front wheels are going to turn.)
And a suspension that gives me lots of travel. (This is going to be used as an RC rock crawler.)
The suspension needs to be as low and compact as possible but still giving the axles lots of articulation. 

Any tips/ideas?  I really need help with the suspension and steering. 

[jorgeopesi]

With that XL motor I would recomend you more robust axles take a look at this maybe it could give you some ideas.

Tatra 2017

[suffocation]

14 minutes ago, jorgeopesi said:

With that XL motor I would recomend you more robust axles [...]

The axles are the same as in Sariel's latest Tatra, which is driven by 2 XLs, so there shouldn't be any problems.

[Mechbuilds]

Yeah the wheels turn and if i hold it from the hub, the frame has a minor flex. But after i strengthen the frame and add shocks, it should be gone. 

[Mechbuilds]

What i could do is move the front axles half a stud apart so i can center the steering system. 
But i was planning on attaching two left and two right front axles together in the middle and adding a steering system between the axles in the center.. But i'm not sure how suspension travel affects the steering angle.. 

[1gor]

Keep in mind that steering links have to be closer to chassis not to affect suspension travel  and look carefully on pivot points...hope that you are satisfied with current shocks, because they are to big for my project ?

[Mechbuilds]

Has anyone tried tackling a steering system like this? 
I asked sariel how he did it but he refused to answer. 


EDIT:
 

This is not an easy task.. But i can go zerobricks idea if i can't come up with a solution. 
I was hoping to use those bigger wheel bearings though.. But there simply seems to be no way to connect it properly.. But i'd love to have just one vertical axle that i spin to turn it. 
Problem is trying to link them to the steering knuckles.. 


What i also could do is just solid front axles... 

Edited July 2, 2018 by Mechbuilds

[Zerobricks]

Hi

I used such steering solution successfully here:

For steering I used 2 mini linear actuators which gave system lots of steering power and stiffness.

Check the LDD file here (use developer mode and disable physics check before opening it):

www.bricksafe.com/files/Zblj/mini-tatra-8x8/Tatra%2062.4%208x8%20LDD%20DEV.lxf

Edited July 1, 2018 by Zerobricks

[Mechbuilds]

5 minutes ago, Zerobricks said:

Hi

I used such steering solution successfully here:

For steering I used 2 mini linear actuators which gave system lots of steering power and stiffness.

Check the LDD file here (use developer mode and disable physics check before opening it):

www.bricksafe.com/files/Zblj/mini-tatra-8x8/Tatra%2062.4%208x8%20LDD%20DEV.lxf

Can the gear ratio be changed to match the rear axles though? 

[Zerobricks]

Gear ratio of what?

[Mechbuilds]

Just now, Zerobricks said:

Gear ratio of what?

The center uses big gears for wheel axles and small gears for the single middle axle.. But the rear axles i'm using use both same sized axles in the middle and for wheels.. 

This means, if i build the same axle you've shown, the rear axles will spin 2 times faster than the front axles.. Otherwise looks like a solid solution. 

[Zerobricks]

That's up to you, how you will build the axles. Seems to me you are trying to combine a bit of mine and a bit of Sariel's s setup. You have to experiment and find a way how to make it work.

Edited July 1, 2018 by Zerobricks

[Sariel]

3 hours ago, Mechbuilds said:

I asked sariel how he did it but he refused to answer. 

Oh man, just because I don't have time to answer your many emails (I have 3 weeks to move to another apartment with my wife, kinda busy right now) doesn't mean I "refuse to tell you how I did it". Besides, I've already shown quite a lot in my video and at my website, with all the photos and description, for a creative person to reverse-engineer everything, possibly improving on me in the process. But no, some people DEMAND to be personally assisted with everything, because trying something yourself is below their dignity, and then of course I'm the bad guy because I have more pressing matters to attend to than hold their hand through every step of the building. Seriously...

Edit: I've checked and there's a pretty close photo of my Tatra's steering solution at my website. But let me guess, you never checked my website, right? 

Edited July 1, 2018 by Sariel

[sirslayer]

Sariel maybe you should write a book on Lego techinc chassis fundamentals!!   can't wait to see the finish build mechbuilds!! 

[Aventador2004]

3 hours ago, Sariel said:

Oh man, just because I don't have time to answer your many emails (I have 3 weeks to move to another apartment with my wife, kinda busy right now) doesn't mean I "refuse to tell you how I did it". Besides, I've already shown quite a lot in my video and at my website, with all the photos and description, for a creative person to reverse-engineer everything, possibly improving on me in the process. But no, some people DEMAND to be personally assisted with everything, because trying something yourself is below their dignity, and then of course I'm the bad guy because I have more pressing matters to attend to than hold their hand through every step of the building. Seriously...

Absolutely, in fact, it is quite unfairly stated toward you. This is like remodeling and calling it your own @Mechbuilds. Exactly like another company...

Sariel is a huge help to the Lego community, give him his respect.

[Sariel]

8 hours ago, sirslayer said:

Sariel maybe you should write a book on Lego techinc chassis fundamentals!!  

I thought I kinda did: https://www.amazon.com/Unofficial-LEGO-Technic-Builders-Guide/dp/1593277601

[doug72]

51 minutes ago, Sariel said:

I thought I kinda did: https://www.amazon.com/Unofficial-LEGO-Technic-Builders-Guide/dp/1593277601

Yes you have already provided an excellent guide book,  I have your 2nd edition.

If I get stuck during a MOC build  I always consult your guide to see if there is a solution and for ideas.

Doug72

Edited July 2, 2018 by Doug72

[Mechbuilds]

Woaaah! Chill dude. Refused to answer simply means that i haven't received an answer. Don't know how to say it in english.
Sorry if i gave an impression that i was wronged by sariel by something. 

Anyways. What i like to do is build something according to instructions so i can understand how it functions before i can improve upon it.. 
The images in sariels site don't really show the steering linkages how they're built cause they're hidden behind a massive clump of parts. 
I can't tell how they're mounted inside. Otherwise i wouldn't have asked at all in the first place. 

My goal is to make a 8x8 RC truck i can go have fun outside. 
I'm not a lego engineer. I'm just a construction worker who has about 1-2 hours maximum a day time to spend on lego's. 

If i can combine 1,2.. even 3 mocs together into something that's semi functional then i've accomplished something.. 
Even if i outright copy somebody elses moc, i don't really care cause i only built it to have fun with it myself. 
If i make modifications, i'll always remember to give credit to who's ever moc i copied. 

What i need is just a functioning chassis that works and i'll build my own "body" on top of it and then modify the thing as a whole when it needs to be modified. 


Currently i'm directly copying zerobricks mini tatra build's steering mechanism cause i couldn't figure out a functional way to make 4 wheel steering without the wheels turning when the suspension drops. 
Instead of wasting the only 1-2 hours a day time on a steering mechanism, i decided to just go with what works and start working on the chassis as a whole. 


What i could understand from the LDD file is that the chassis doesn't have suspension springs but it uses a leaf spring system by having a Link 9 https://www.brickowl.com/catalog/lego-link-9-32293-35257? 
I'm wondering how durable this is when the moc is used for rock climbing? 

Progress:





This is basically the same steering system as zerobrick's tatra design.. However, i'm thinking about modifying the steering system in the middle so i can attach a PF servo to it. 

[Zerobricks]

52 minutes ago, Mechbuilds said:

I'm wondering how durable this is when the moc is used for rock climbing?

Depends on the weight you put on it. Front links are reinforced with a 5L beam, so they can take quite a lot of punishment.

[Mechbuilds]

Chassis progressing slowly.. Rear axle is taking shape.. 



The steering system now has a gear. Because i was planning on attaching a steering servo to the front to turn the vehicle rapidly. 
Problem is, the gear doesn't turn much when steering.. A steering servo would turn a whole 90 degrees.. Which is far too much.
I think it's easier to calcultate the travel once the back wheel hubs are attached so they don't swing around and bind everywhere.. 

I wonder if i should go with the zerobricks leafspring system to the back as well to match the front or go for springs and put all the weight (batterypacks and motor ect.. ) on the back.. 


Also, is there a durability difference on colors? I can get the 32293 axle in black, grey and brown color. 

Edited July 2, 2018 by Mechbuilds

[Johnny1360]

4 hours ago, Mechbuilds said:

Also, is there a durability difference on colors? I can get the 32293 axle in black, grey and brown color. 

@sirslayer might have some advice for you in that department, I think he has been doing some testing on part strength and weight differences. I think he said black seems to be the strongest. 

[sirslayer]

from my experience black color axles is the only color that haven't snapped or crumple apart on me.. Using a scale that measured 0.001 of a gram is recommend and just by observation and you can see the black color axles are thinner. I found this sharable youtube video and wow, is it true??? black axle are indestructible? 

 

[Mechbuilds]

Wheels came in the mail. 

Now still waiting for various parts so i can continue the project. Still need to order a lot more.. 


Next i need to start figuring out the steering so it would work on a servo.. 
The one gear in the middle only turns one tooth to the side.. So the turn radius is 3 teeth on the gear. 
EDIT: Wormgear. 

Edited July 4, 2018 by Mechbuilds

[Mechbuilds]

Still no updates on the build but RC stuff are coming in the mail. 

Thinking about attaching a winch to the front. 

[Mechbuilds]

One shipment of parts came in the mail! 

Progress has been made:

Remote joystick.  (Instructions by Simon's lego technic corner)
Front leaf springs attached to the front and rear axle progress.. 
The axles have been attached in the middle. Now once my wheel bearings come in the mail, i'll start working on rear leaf springs. 
Still haven't ordered the steering servo yet. 

Pics:







Offtopic: 
Sry about the pile-o-parts in the background.. "Mr legs" is taking care of them. (Maybe i should build "Mr legs" a little further.. He's my builder buddy!)