efferman

Axle Collection Thread

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Just now, aminnich said:

no differential :sceptic:

Not in between the wheels yes, but you can add one behind, from the two axles coming out.

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never thought of that, I am so used to just having the differential in the middle of the axle like we see on the sets from LEGO.  I am going to have to figure something out.  First to get the 2 axles to have a diff then combine into one central axle... we shall see 

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The differential would be mounted at an angle, like in Gerger's Grove crane. Something like this:

17stud.png

17stud-inside.png

(You can find more info on this axle on page 2 of this thread).

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So I downloaded the LXF file from the second page, here is a size comparison with what I have 

800x446.jpg

about 2 studs too wide, BUT I think I could move the diff out of the axle and do the gearing work with the diff just outside the axle, what do you think of this?

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800x600.jpg

800x600.jpg

800x1067.jpg

800x1067.jpg

Big bad front axle experiment, 8 studs suspension travel, 30° steering (2 stud rack travel boh ways) pneumatic tightening or softening of the suspension, slackless wheelhubs that will fit 3 hole rims, direct drive from 2 L motors wich are semi suspended.

So far it holds up well during testruns, but I will have to do some re-design to get better mounting options attaching it to the chassis.

Cheers!

Edited by Permo

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After watching @Didumos69 build his Greyhound buggy, I wanted to see if it was possible to build a portal hub based off of his turntable hubs.

This is my result. I have built it in real-life. The entire hub is inclined to get the control arm mount points and the drive axle as lined up as possible. This only fits in the large rims with the 6 pin hole pattern. The 107 mm Claas tires, the 94.8 mm truck tires and balloon tires, and the 68.8 x 36 ZR tires all fit. The pink assembly is only for the 94.8 mm truck tires, it stabilizes the wheels. It isn't necessary. The blue assembly is just a mockup to show how it could fit. There is a little bit of king pin inclination. Using the 94.8 mm tires, ground clearance at the bottom of the hub is a little of 4.5 studs. Because the hub sits at an angle, the distance at the towballs is a hair over 5 studs. This hub 1 stud narrower than the Lego portal hub piece. 

The lxf can be found here: http://www.brickshelf.com/gallery/steater/Ideas/mini_turntable_portal_hub.lxf

mini_turntable_portal_hub.png

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The hub itself feels fairly solid, but, there is nothing keeping the 8 tooth gear from sliding. The control arms are not parallel either, so they cannot be braced closer to the hub end. This hub is also as floppy as the standard Lego hubs, so there is no advantage there.

 

The hub was more of a "see if I can" than anything. It is a lot of complication for hardly any change in the gear reduction, and reducing the width by 1 stud. 

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Promising, very promising....

800x600.jpg

Need torque ? Need insane steering radius ? Need no CV joints...

 

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Just now, Permo said:

Promising, very promising....

800x600.jpg

Need torque ? Need insane steering radius ? Need no CV joints...

 

Good idea, but there are lots of flaws:

- The 12 tooth gear meshing with turntable can slip out

- The 12 tooth gear from the L motor is very badly supported and can cause big stress on the motor output

- Whole assembly is very inefficient, since the vertical drive axle has to support the force of the vehicle, the torque created by the wheel trying to spin, the force created by the wheels pushing it forward and the forces created by steering system trying to steer wheels - all of these create friction on the spinning axle.

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Yes, correct, this was just a quick testing of the principle of driving the large turntables directly, there's a far mre sophisticated version now on my desk, wich will be part of my next moc, it needs to be build solid as a rock because the amount of torque is absolutely huge for a Lego contraption.

And there's another thing there, it really needs a centre differential because of the huge steering angle that is allowed with this setup the inner wheel hardly rotates in the corners, in combination with the torque it just makes the whole thing whobble and squeek in the corners.

So I now have a centre differential, formlocked build, pneumatic suspended V2 in the works, removing the motors allows for even more gearing if needed and the good thing is, the gearing takes place at the right place for Lego contraptions, there's no stress on the fragile differential as all the gearing is taking place after it, and with two coupled L motors I am actually gearing up towards the differential so it still has a nice speed, it's definitely not crawling, no critical stress points in the drivetrain and a huge steering angle.

I think as a concept this is very promising.

Edited by Permo

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after building more today, I do not think efferman's axle will work out as nicely as I thought it would.  I believe his axle is meant for a European truck when the chassis does not extend much past the axle.  

 

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Very promissing idea; I was looking for something like this for my syn-trac project

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Those joints are ratcheting, so that means you can’t have (proper) suspension. 

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2 hours ago, LvdH said:

Those joints are ratcheting, so that means you can’t have (proper) suspension. 

You have tested this solution?

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2 hours ago, I_Igor said:

You have tested this solution?

No, but I have a couple of those joints, and these are one of the strongest ones LEGO has...

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6 hours ago, LvdH said:

Those joints are ratcheting, so that means you can’t have (proper) suspension. 

You are right. I didn't realize that because they are smooth in LDD. Now when I took a closer look of the picture I see it. South Harmon Institute of Technology (read only capital letters).

Edited by pagicence

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7 hours ago, LvdH said:

No, but I have a couple of those joints, and these are one of the strongest ones LEGO has...

Thanks

7 hours ago, pagicence said:

You are right. I didn't realize that because they are smooth in LDD. Now when I took a closer look of the picture I see it. South Harmon Institute of Technology (read only capital letters).

That is what I thought in first place after seeing images...

Edited by I_Igor

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Indeed that would be a very stiff suspension. I do wonder though if the ratchet mechanism could be modified to make this work. 

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