5-link B4

[elvo]

:wub

[Lee]

Very cool.

How is the shock mounted at the bottom? and also is this just to give it infinate toe in adjustment?

[jimmy]

awesome!

[super__dan]

http://en.wikipedia.org/wiki/Multi-link_suspension

I've never really understood the benefits and not sure I'm any the wiser from the above article. Does look nice though!

[ashleyb4]

That is awsome!

A

[Northy]

Did you not hear me talking to Tom about this at the weekend? ;)

G

[ashleyb4]

I would be worried about poping one of the 28 ballstuds off.

A

[CAClark]

B4 Avante stylee, looks pretty cool.

[super__dan]

No, well not that I remember. I remember the quiz qeuestion though ;)

[Mike Hudson]

cool idea but how will that look with the bodyshell on :lol:

[elvo]

Very cool.

How is the shock mounted at the bottom?

In a more mechanically sound way than on the JRX-2 :lol: It's mounted to the bottom forward link. Figuring out a way to mount the shock properly was 95% of the work.... (the other 4,99% was making sure it didn't pop off landing the first jump)

and also is this just to give it infinate toe in adjustment?

Well it's got infinite adjustment of... ... basically anything :D A 5-link is suspension nirvana.

It seems to be crash-proof as well. But I'm no expert in that matter...

[elvo]

I would be worried about poping one of the 28 ballstuds off.

A


Only 22 for the rear suspension :p 32 for the whole car...

[Chrislong]

Its an impressive piece of work.

But don't take offense, I can't see the point, yet. Have you done it for performance or for own curiosity?

[Cockerill]

I think its a car only him or Jim Dixon will ever understand fully :woot:

It does look good tho. As Chris says, what's the theory behind it other than infinitely adjustable?

[nitrokillah]

good idea but looks over complicated to get it setup right

[Lowie]

If I understood the wikipedia-article correctly, it is quite easy to tune a car with this kind of suspension, as changing one aspect of the tuning, doesn't affect other aspects.
Also, camber and caster are much more stable. When a car lands from a jump, or rolls in a corner, with a conventional suspension the camber-angle will change, but not with this type of suspension, so it is much more consistant and the suspension can move more freely.

http://upload.wikimedia.org/wikipedia/en/thumb/b/b6/5link3Dtop1.gif/200px-5link3Dtop1.gif
(source: wikipedia)
On this picture you can see that movement of the wheel does not affect the angles.

Drawside is the more complex build ... and you have more parts to maintain, or that can fail.
... and according to the wikipedia-article, a swaybar is needed to control (slow down) the chassis rolling.

... So all Elvo has to do now, after testing this suspension, is building it also into his S2.
Next thing you know, conversion kits are sold lol

[elvo]

Its an impressive piece of work.

But don't take offense, I can't see the point, yet. Have you done it for performance or for own curiosity?


For both!
The point is this: I've always found anti-squat to be a huge compromise. Very little anti-squat is good for accellerating through bumps and sideways traction, but lots of antisquat is good for absorbing bumps off-power, and on-power traction. And it's a fixed value; you set it, and you're stuck with it.
With a 5-link suspension, the two forward links allow the same kind of flexibility and tunability for anti-squat as you have now for roll centre, it's almost limitless. Anti-squat varies throughout wheel travel. That, and you can make the rear wheels move back in bump. I've always wanted to test that, but with A-arms, you'd have to use a massive amount of anti-squat (like the AERO, possibly more), but then the shocks don't work properly anymore...

[Chrislong]

Is there a name for each link so they can be identified?

if the two on each side (drag link upper and lower?) are unequal length, then that would mean antisquat could increase or decrease through suspension travel, same as if the 2 links were not mounted parallel.

Then with the lower two wishbone links on each side, if these are unequal in length, or not mounted parallel, then the toe in will increase or decrease through suspension travel.

Then the top link, we all know what that does, camber change through suspension travel.

Then beyond that, with the movement of one factor, means other tie rods are twisting and so other factors become changeable through suspension travel even if not intended to be.

But with all this, id be completely lost. On paper it may mean a perfect setup can be acheived, but do we live long enough to find it practically? :lol: Seriously though.

On that animated picture above, links don't look to remain static in length through the animation, or is that just me?

Will you be running something like this at Belgium? I am intrigued by this, and impressed with your engineering and bravery mate.

Chris

[elvo]

Is there a name for each link so they can be identified?
Probably, just use words like forward, side, rear,.. etc.


if the two on each side (drag link upper and lower?) are unequal length, then that would mean antisquat could increase or decrease through suspension travel, same as if the 2 links were not mounted parallel.

Anti-squat decreases in bump regardless of link length being unequal or not. It's the same as with roll centres: they shift as the car leans in turns, if you change link positions, they just shift a little more or a little less, or earlier or later, or further or... you know.

Then with the lower two wishbone links on each side, if these are unequal in length, or not mounted parallel, then the toe in will increase or decrease through suspension travel.
Indeed. Decreasing toe during compression is bad, I know that from previous experiments. Don't know about the opposite. This is also called 'roll steer', and it's generally regarded as a very, very bad thing, either way. But I kept the B4 geometry for those.

Then the top link, we all know what that does, camber change through suspension travel.

Then beyond that, with the movement of one factor, means other tie rods are twisting and so other factors become changeable through suspension travel even if not intended to be.
The forward and side links are close to perpendicular (on my car, not in the wiki animation), so they don't influence each other too much. It was hard getting the top side link parallel to the 'wishbone' link, because it's far from it on a standard B4. The spur is in the way.


But with all this, id be completely lost. On paper it may mean a perfect setup can be acheived, but do we live long enough to find it practically? Seriously though.
There aren't that many options really. I kept the B4 geometry (which is good) and just added side links. And because the shock attaches to the lower side link and I didn't want to have to make a new shock tower or use a different shock length, the pickup points and length of that link were more or less determined as well. And the top side link had to be about the same length. In the end, there are not many variables left.


Will you be running something like this at Belgium? I am intrigued by this, and impressed with your engineering and bravery mate.


Running the 5-link at the GP? There's a fine line between bravery and foolishness! Let's say I don't know which side I'm on yet :-) Going from a nice mid-motor car back to B4, now that's foolishness, so I'd have to make a 5-link for the S2. But the S2 has the shocks behind the CVD's, so the shocks would have to attach to the rearmost lower 'wishbone' link instead of the side (drag) link. And that means it won't have the B4 shock geometry :-/

[Danny McGee]

wouldnt mind seeing a bit more, with the wheels off ;)

[Chrislong]

Would it be possible to mount the shocks on the front of the rear tower on an S2 to match the b4 geometry? Just an idea.

Well, if you don't run it, please do bring it with you still. ;)

Chris

[elvo]

Would it be possible to mount the shocks on the front of the rear tower on an S2 to match the b4 geometry?.



It already is!


BTW: Is Danny seducing me? :blush:

[Chrislong]

He's a student, if he gets out of control just put him on a train - he'll be missing for days! :lol:

[Cockerill]

:lol::lol:

[Danny McGee]

He's a student, if he gets out of control just put him on a train - he'll be missing for days! :lol:

Ha bloody ha :o

[Lowie]

just read on another forum about this type of suspension being nothing new (Elvo never claimed to have invented this thing). But I was surprised to learn that it even allready had been used on a RC-car before.

The Losi Jrx2 (1988) (with thx to Asso-man)

http://i304.photobucket.com/albums/nn162/boudddha/MINTEarlyJrx-2.jpg

http://i304.photobucket.com/albums/nn162/boudddha/MINTEarlyJrx-26.jpg

[elvo]

The Losi Jrx2 (1988)

http://i304.photobucket.com/albums/nn162/boudddha/MINTEarlyJrx-2.jpg

http://i304.photobucket.com/albums/nn162/boudddha/MINTEarlyJrx-26.jpg


The manual is on here somewhere..... under 'downloads' or 'reviews' IIRC.

[SHY]

And the Tamiya Egress

[smokes]

how does it stop the wheel base shortening as the wheel travels through the suspension arc? i thought that is why i though double wish bone are more commonly used in racing to stop this happening. I know multi link is used on most modern cars due to it compact construction layout and good handling properties.

[CBRDEAN0]

how does it stop the wheel base shortening as the wheel travels through the suspension arc?.

You Don't.

If you take a look at the cars used on the Paris/Dakar rally you will see that the use a 5 link system too.

If you design the drag links so that they slope up towards the front of the car at static suspension height - It will lengthen the wheelbase and add stability when the car lands.

You can also use a 5 link setup to add toe-in under squat for more stability during accelleration.

[ashleyb4]

OOOO i want that jrx.

A:wub:wub:woot::thumbsup:

[smokes]

not good for on road if the yaw rate exceeds 5 degs of more in a corner as this could make the loaded side wheelbase in a corner shorter than the unloaded side in a corner. That said pug use a trailing are setup that works really well on the old pugs.

[Jonny_H]

not good for on road if the yaw rate exceeds 5 degs of more in a corner as this could make the loaded side wheelbase in a corner shorter than the unloaded side in a corner.aaaaand... so what?

Besides, it depends on roll angle not yaw rate (which would be in deg/sec); and it also very much depends on the length of the arms and their angle at normal ride height.

[Southwell]

Who cares, on road sucks :thumbsup: ;)

Good job Elvo :D

[elvo]

aaaaand... so what?

Besides, it depends on roll angle not yaw rate (which would be in deg/sec); and it also very much depends on the length of the arms and their angle at normal ride height.

And their angle at normal ride height is ... up towards the front of the car. So loaded side wheelbase would be longer, not shorter.


http://www.rc-offroad.be/pictures/2008_05_11_training_vlijmen/pages/vlijmen_practise_032.htm


(And yes, on-road is for wimps)

[Paul_Sinclair]

Looks very good Elvo! Props! :thumbsup:

How's the wear/slop coming? Is there much? I would think finding some nice heim-type joints would help.

You know, an X - 6 isn't much wider than a B4...

[elvo]

How's the wear/slop coming? Is there much? I would think finding some nice heim-type joints would help.

You know, an X - 6 isn't much wider than a B4...


Slop is ... ... not too bad. There is some; slightly more than on a freshly built B4 suspension. But it feels as if it's spread out over 3 dimensions, rather than being mainly in the dimension where it affects camber but not toe-in. But then again, I didn't use new ball studs in 2 places. It's still fine after a few rough test sessions, which I think is also due to the fact that the forces are more evenly spread over all the different links.

Yeah, only 2/10 are heim-type joints. More would be better.

Chassis width is no problem, but having the shocks behind the axles is.... ... a bit.

[CCristo]

Elvo,

What rear hubs are you using? Any chance we can see some detailed up close pics?

[elvo]

Elvo,

What rear hubs are you using? Any chance we can see some detailed up close pics?


Custom made ones. They took many evenings/nights to design, and 2 days to machine.

[rich_cree]

I love it!

That is ace :)