Suspension Issues

[Phoxtane]

I'm trying to build a suspension system out of the new snowmobile suspension arms and the hubs that come with 42000. I was hoping to make it small, but I'm having issues actually designing it and making it compact. (In other words, I've no idea what I'm doing...)

As such, I'd like to build a compact suspension that'll fit the wheels that come the 42009 crane. Since it's for a typical car, with front wheel steering and rear/all wheel drive, if I can do that also, it'd be perfect.

The main problem I seem to be having is attaching the wheels to the hubs, having a hub that'll allow for a driveshaft to pass through, and then mounting the whole assembly in such a way that I can still attach a shock absorber and steering assembly, if needed. Sadly, I'm not as good with Technic as I had thought.

[Black-Build]

There was a Hummer HX trophy truck from lego on this forum that used suspension you need, sadly, I'm on my Ipad and don't know how to copy a link...

[rm8]

here we go

highres pictures:

http://cs608626.vk.m...pppQ1mRT2hQ.jpg

http://cs608626.vk.m...VTinUxFiYqA.jpg

http://cs608626.vk.m...8MGcfMEjL2I.jpg

http://cs608626.vk.m...YrO_S2kWx3M.jpg

there is also useful "Axle thread" here

http://www.eurobricks.com/forum/index.php?showtopic=92099

Edited July 15, 2014 by rm8

[Black-Build]

here we go

highres pictures:

http://cs608626.vk.m...pppQ1mRT2hQ.jpg

http://cs608626.vk.m...VTinUxFiYqA.jpg

http://cs608626.vk.m...8MGcfMEjL2I.jpg

http://cs608626.vk.m...YrO_S2kWx3M.jpg

Yeah, those I ment!

Edited July 15, 2014 by Black-Build

[Phoxtane]

Well, after a good while of tinkering, I managed to come up with this:

This is meant to be the rear axle, so it requires a driveshaft, but not steering. The current problem is that I haven't got enough space to wedge another U-joint or CV-joint in between the small hub and the current U-joint. In addition, I haven't got a place to attach a link to keep the hub locked and I haven't got an upper attachment point for the shock absorbers. I decided to keep it simple and start with the core of the device, which I knew was going to involve a differential and most likely a 5x7 frame. The issue is, this isn't nearly as workable for the front axle, even given how unworkable it is so far! Should I go back to the 42000 hubs, to make life easier on myself? Or do I need to custom-build a hub out of small pieces to make this work? I'm up for either so long as it works.

Edited July 16, 2014 by Phoxtane

[Zerobricks]

What about using the older black hubs? Those would fit perfectly there.

Edited July 16, 2014 by Zblj

[Black-Build]

I agree with Zblj, you can't make the wheels driven with these hubs i think. I think you need to find another way.

Edited July 16, 2014 by Black-Build

[Rockbrick]

if you could manage to work this onto the hub and axle coming from the Universal joint:

then you could attach a wheel to the end of the axle going through this - but it will be a sliding joint so keep that in mind

stiffen it up a bit - use this one and two suspension arms side by side:

[Phoxtane]

Both great ideas. I wasn't able to work out how to attach the custom hub, so I went ahead and used the older black hubs and wound up with this;

Upon further examination, it appears I've replicated the dark gray A-arm, but with more pieces and in a bulkier package! I guess we all have to start somewhere.

In addition, since these are the same size, this suspension unit is still too wide for the size of the 42009 crane wheels. Which leads me to the next line of inquiry: Perhaps another drive suspension unit could be built with these?

I don't think there's really a good way to build a powered drive unit with these guys. Perhaps some sort of independent trailing arm suspension in the back would work? I don't think there's a good way to power those as well. I'll have to ruminate on it for a bit at work.

[Black-Build]

I would say, have another look at Hummer HX's suspension. I think you have to scrap the diffs...

[Phoxtane]

Not in the rear I hope. That's where I'll need it. Perhaps it could be done with a floating differential?

[Phoxtane]

I went back and did some poking around with the linked images. I was able to tease out this assembly here:

It's much better than any of my previous attempts to build anything more than a basic suspension system, that's for sure. I even think it's Ackermann-correct! However, if turned too far the steering tends to collapse in on itself, due to the linkages going parallel and then inverting in relation to the connections on the hubs. I'm not sure how to correct this, as a servo motor will move the steering rack enough to cause a collapse every time.

[VKTechnic]

However, if turned too far the steering tends to collapse in on itself, due to the linkages going parallel and then inverting in relation to the connections on the hubs. I'm not sure how to correct this, as a servo motor will move the steering rack enough to cause a collapse every time.

The way to solve this problem is to move the link mounting points so that the steering link is parallel to the suspension arms. This problem is nicely addressed in

at 2:15.

[Phoxtane]

If I move the links parallel to the suspension arms, then the hubs will have the wheels toeing out. This was how I managed to keep the wheels straight when the steering is centered. Thing is, I think that's how it was done in the Hummer images that were linked earlier, so I've no idea how they managed to get around that issue. Perhaps the shocks mounted in between the links and the suspension arms are what keep the links from collapsing? If so, then I can just put a beam on the-

Oh.

I see what is going on here now; the shocks are mounted between the linkages and the suspension arms on the Hummer model in order to prevent this issue from occuring. As such, I've added some half-width 5L beams on the ends of the arms to do the same thing. I think I'll end up with a greater steering lock as well!

[VKTechnic]

To correct the toe-out, you'll of course need to redesign the steering rack, like so:

This will give you a more compact setup, and you won't need those half beams to keep the wheel from collapsing in.

Plus, you'll have much less bump steer at center and more steering lock.

[Phoxtane]

Done and done:

However... another problem has arisen. The small pieces behind the steering rack are giving me enough grief with catching on the frame, and the steering rack being difficult to brace properly due to these parts has led me to decide to abandon this concept and turn to The Unofficial Technic Builder's Guide for help. There's a small steered independent suspension unit in there [page 226] that will fit my needs perfectly. Thanks for all the help!

[SNIPE]

Maybe something like this:

[Phoxtane]

I think I'm quite close to getting the axles completed. Here's the progress I've made:

Notice the problem? The rear axle is about 4 units wider than the front, if I'm measuring correctly. That's with the rear tires flipped around so the deeper face is towards the center, which shaves some distance off. If I can keep an driven independent suspension with differential in the back, I'l be happy. I don't think it can be done without some serious trickery though, which is way beyond my level [admittedly, pretty low to start with].

I think some sort of trailing-arm suspension would work; perhaps with the suspension arms running parallel front-to-back, rather than branching off perpendicular to the chassis. The problem then becomes an issue of getting power to the wheels.

[Rockbrick]

Why not use 4L beams (in pairs if you must) instead of 5L at the rear?

[Phoxtane]

That's the minimum distance I've found for a CV joint and a U-joint to connect; they're butted up next to each other. That's pretty much the only way to get power from the differential and maintain the parallel linkage at the wheel end of the suspension arms. In order to retain the traditional suspension setup, the only width savings I can see would be in the hubs themselves or somehow produce a floating differential setup. I recall seeing a car with one in this forum, but I've no idea where it's gone to.

Apart from that, I think a more feasible solution is to move away from the traditional independent suspension setup; but how?

EDIT: Found it:

Edited July 18, 2014 by Phoxtane

[Rockbrick]

That's the minimum distance I've found for a CV joint and a U-joint to connect; they're butted up next to each other. That's pretty much the only way to get power from the differential and maintain the parallel linkage at the wheel end of the suspension arms. In order to retain the traditional suspension setup, the only width savings I can see would be in the hubs themselves or somehow produce a floating differential setup. I recall seeing a car with one in this forum, but I've no idea where it's gone to.

Apart from that, I think a more feasible solution is to move away from the traditional independent suspension setup; but how?

EDIT: Found it: (proper formatting will ensue when I have access to a proper computer and not a mobile device! It's in the third result for the search terms 'floating differential' in this sub-forum)

Ah i see now - I do not have these parts so I didn't know they were 'butted' up

you could always place the diff longitudonally, and use tatra like bevel gears to get to it

[Phoxtane]

In order to make that work, I'd end up with some sort of setup where the power for the differential enters from the side, or from in between the differential and one set of the bevel gears. Even then, the points where the power exits the frame to the suspension would be spaced very far apart. It could work... but it'd be more workable in a Tatra-style truck, I think

In the above picture, it looks like the differential is held in place by two small L-beams, and then connected to the wheels by a CV-joint piece that connects directly to an unsteered 42000 wheel hub. It looks as if the only suspension arms are the lower ones; I'm not quite sure how the upper half of the hubs is secured. Even so, this means that there isn't a parallel linkage- and as such, the rear suspension is practically a Tatra setup.

[Phoxtane]

After a bit of digging, I found the instructions for the car pictured above. It is a revamp/rebuild of the 8081 Extreme Cruiser by Thirdwigg: http://www.brickshelf.com/cgi-bin/gallery.cgi?f=538248