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dirtydiesel

One link suspension setup without a panhard rod

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I'll have to find a laptop - these videos won't play on my phone or tablet..... :-/

Wouldn't work from my iPhone either until I tried open in new window

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Excellent ! Worked for me too. Thanks Lewis - I can go and watch the Hollinsclough clip now too. :)

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Thanks for those.... that climbs very well, it almost looked like it was sqauting under power, hard to tell my pc isnt happy with multimedia currently running in safe mode lol

thanks for the comparison vid of the 80series, notice on the second steep climb how it sort of bounced, shame the camera wasnt side on as I bet we would have seen the rear suspension bouncing up and down....... this is what I would have expected from yours, yet yours was nice and smooth even when you broke traction at the top it didnt seem to bounce

hmmm I know this is going to sound a bit... silly but I'm starting to think radius arm suspension might react differently

Could you get some more vid but side on, and try it with different speeds on the same hill eg crawling vs hp

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biggin quarry?

You have an obsession with biggin quarry Mikey :P

The vids were taken at manton quarry in lincolnshire.

It seems to go well, have you turbo'd it now?

It was always turbo'd Lewis, the semi electronic pump on the mondeo engine always held it back, i have fitted a 300tdi injection pump to the ford engine now and it has really transformed the engine.

It looks like it climbs well and the rear suspension certainly seems supple and allows flex, however to be honest I'm so out of touch I can't really see what difference the sliding a frame makes to climbing ability over a panhard

I don't think the sliding a frame make a blind bit of difference to the way it climbs, i posted the clips for DeRanged and to try and make sense of why the high AS/AD works for me.

Aggressive driving too, yourself or someone else?

Both clips are Johnny, the agressive approach was the only was to get a clear on that section, he was the only person to clear it, i'd tried to finesse it and only got a 1.

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Thanks for those.... that climbs very well, it almost looked like it was sqauting under power, hard to tell my pc isnt happy with multimedia currently running in safe mode lol

thanks for the comparison vid of the 80series, notice on the second steep climb how it sort of bounced, shame the camera wasnt side on as I bet we would have seen the rear suspension bouncing up and down....... this is what I would have expected from yours, yet yours was nice and smooth even when you broke traction at the top it didnt seem to bounce

hmmm I know this is going to sound a bit... silly but I'm starting to think radius arm suspension might react differently

Could you get some more vid but side on, and try it with different speeds on the same hill eg crawling vs hp

I fully intended to take some more comparison clips on the setting up day, but it was getting colder and darker and beer was calling!

I'm pretty sure it does squat under power, which is the opposite of what the AS% says it should?

I am begining to think that the AS/AD number has little or no actual meaning, other than to let me compare what i have against what i build next, The way the supension works in this buggy suits my driving style and the terrain i drive very well, so my thoughts are to try and build the percentage differance in AS/AD from this one into my next one

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I'm pretty sure it does squat under power, which is the opposite of what the AS% says it should?

people forget about the front end, as you get mass transfer from acceleration remember your front is lighter so the springs can push it up ... my old rangie was a bugger for this

I am begining to think that the AS/AD number has little or no actual meaning, other than to let me compare what i have against what i build next, The way the supension works in this buggy suits my driving style and the terrain i drive very well, so my thoughts are to try and build the percentage differance in AS/AD from this one into my next one

people read way to much into AS in my opinion, remember that AS is the % of mass transfer from acceleration that the links get, the whole amount still ends up on the wheels in the end, because the % that the springs get still pushes down.... the bonus from a high AS is faster transfer of this weight to the tyres so better grip

The catch for use compared to dragsters is we have way more travel in our suspension, and the bit most forget is we drive on hills.... I know this sounds obvious but this moves the CoG, WB and the angle of our links..... now add that with what happens when you loose grip the back end lift from lots of AS is gone, now when your on a hill that can get scary..... most of us have seen the SWB hop when on a steep climb

I see AS score as more of a balance to make a stable truck not a super take off truck

The more I think about it, the more I feel radius arm style links work differently.... because the link is fixed to the axle tube there is no push pull action going on

Ive been racking my brains trying to remember if I have ever seen a radius arm truck hop.... but I cant, I mean I dont think Ive ever seen one hop

I remember the budget guys yrs ago in street drags building ladder bar rear suspensions for more AS (a radius arm) but we went four link for the tuneability, I know the ladder bar cars could be setup to hop but its left me wondering if there hop threshold is a higher AS

This is one of my questions for John when he has finished his explanation

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I have posed the following question previously on other forum discussions without receiving an answer.

If the front radius arms chassis attachments happen to be behind the vehicles for/aft centre of gravity, do anti dive forces due to braking tend to lift both front and rear ends, instead of just the front? And conversely if the rear radius arm chassis attachments are in front of the for/aft COG, do antisquat forces tend to lift the whole chassis on steep climbs instead of just jacking the back end ?

Providing traction was maintained on both front and rear axles, I'd assume these opposing forces would counter each other to a degree. But what happens on a steep gradient when front end traction is marginal and rear end traction is high? The rear RA's lifting the whole chassis would presumably be lifting the COG, leading to a possible rear endover flip.

It would be a little more difficult to arrange radius arms or One Links etc in this way on a vehicle with a longish wheelbase, but on something like a Suzuki or even a SWB LandRover, one could get close.

Bill, the important thing is the path of the line from the tyre contact patch through the side view instant centre (SVIC). So you must consider both the height and for & aft position of the SVIC, i.e. don't consider one in isolation. Now plot that line and see where it passes the sprung C of G, more importantly how close/far it is from the sprung C of G and on which side.

I fully intended to take some more comparison clips on the setting up day, but it was getting colder and darker and beer was calling!

I'm pretty sure it does squat under power, which is the opposite of what the AS% says it should?

I am begining to think that the AS/AD number has little or no actual meaning, other than to let me compare what i have against what i build next, The way the supension works in this buggy suits my driving style and the terrain i drive very well, so my thoughts are to try and build the percentage differance in AS/AD from this one into my next one

I can't see the clips, Photobucket gives a message that this is temporary.

%AS numbers are only as good as the data values used to determine them, and the height of the sprung C of G can often be a wild guess that introduces significant errors.

Your statement about using the %AS to compare what works well for you with one build and use it again with another build for similar/same use is spot on.

This is also valid for using the same %AS as someone else if it works well in the same circumstances.

What is not valid is taking values that work well for completely different terrain and traction conditions and expecting them to be ideal in all conditions.

So it is a meaningful measure when used appropriately.

people forget about the front end, as you get mass transfer from acceleration remember your front is lighter so the springs can push it up ... my old rangie was a bugger for this

people read way to much into AS in my opinion, remember that AS is the % of mass transfer from acceleration that the links get, the whole amount still ends up on the wheels in the end, because the % that the springs get still pushes down.... the bonus from a high AS is faster transfer of this weight to the tyres so better grip

The catch for use compared to dragsters is we have way more travel in our suspension, and the bit most forget is we drive on hills.... I know this sounds obvious but this moves the CoG, WB and the angle of our links..... now add that with what happens when you loose grip the back end lift from lots of AS is gone, now when your on a hill that can get scary..... most of us have seen the SWB hop when on a steep climb

I see AS score as more of a balance to make a stable truck not a super take off truck

The more I think about it, the more I feel radius arm style links work differently.... because the link is fixed to the axle tube there is no push pull action going on

Ive been racking my brains trying to remember if I have ever seen a radius arm truck hop.... but I cant, I mean I dont think Ive ever seen one hop

I remember the budget guys yrs ago in street drags building ladder bar rear suspensions for more AS (a radius arm) but we went four link for the tuneability, I know the ladder bar cars could be setup to hop but its left me wondering if there hop threshold is a higher AS

This is one of my questions for John when he has finished his explanation

Hills don't change the C of G or wheel base. You are making the mistake of not changing your reference frame with the slope if you think that, and you are probably getting %AS wrong if you haven't adjusted the reference frame.

The change is suspension height, front and rear does change on hills (and with articulation) and that may, or may not, change the position of the SVIC, relative to the tyre contact patch.

In a 2wd vehicle the %AS doesn't change on hills. In a 4wd vehicle it does because the traction, front and rear, changes. We have squat at the rear wheels, and its opposite, lift at the front (%anti-squat and % anti-lift (for a 4wd only) are calculated the same way, but the proportion between rear and front traction needs to be taken into account for a 4wd, similar as for braking).

Link suspension has an advantage over radius arms in that there is more freedom in where to locate the SVIC, it can even be where there is an empty space.

Another big advantage, assuming there is nothing in the way, is they can allow the %AS to reduce when the suspension rides, thus creating a more stable system vs unstable system if the %AS rises.

For %AS, radius arms will behave the same as link suspension with the same SVIC, and vice versa at a particular suspension height.

Compared to radius arms, link suspension allow more freedom to adjust the roll axis.

However there are more ways to get link suspension wrong compared to radius arms.

Don't judge either link or radius arm suspension by comparing a good example of one to a poor example of the other. Also remember good link/radius arm suspension can be let down by poor springs or dampers.

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I can't see the clips, Photobucket gives a message that this is temporary.

%AS numbers are only as good as the data values used to determine them, and the height of the sprung C of G can often be a wild guess that introduces significant errors.

Your statement about using the %AS to compare what works well for you with one build and use it again with another build for similar/same use is spot on.

This is also valid for using the same %AS as someone else if it works well in the same circumstances.

What is not valid is taking values that work well for completely different terrain and traction conditions and expecting them to be ideal in all conditions.

So it is a meaningful measure when used appropriately.

Thanks for the reply John,

The clips seem to be working ok.

Although the wild guess of CofG can introduce significant errors in the actual numbers, the actual percentage differance between the front and rear should remain fairly constant for any given change in CofG hieght.

Another thought i've been having is how much effect the front to rear weight distribution would have on the position of the CofG

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Thanks John,

The clips work on a daily bandwidth limit for your account.... maybe this is the reason you couldnt see them

lol now Ive got more questions... all good I'll save em up, I'm still stuggling with your last post in the other thread, not your explanation just my head is.... foggy from the pain killers I live on

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Thanks for the reply John,

The clips seem to be working ok.

Although the wild guess of CofG can introduce significant errors in the actual numbers, the actual percentage differance between the front and rear should remain fairly constant for any given change in CofG hieght.

Another thought i've been having is how much effect the front to rear weight distribution would have on the position of the CofG

Dan, how did you determine the cog position, height and forward/rear?

Daan

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Dan, how did you determine the cog position, height and forward/rear?

Daan

The link calculator doesn't allow for fore/aft CoG position. and i used the pirate inspired method for CoG height (top bell housing bolt height)

I have weighed the front and back of the jimny and it's close to 60/40, although with me in it it's probably close to 50/50

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Is the seat a long way behind the centre line? Or is the vehicle that light/you that heavy that it makes such a difference to weight distribution?

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Another thought i've been having is how much effect the front to rear weight distribution would have on the position of the CofG

There is something else to consider to do with weight distribution... the more weight on the tyres the more grip.... on most 4wd's that weight is 75-60% front axle, as you accelerate some of the weight moves from front to back

There is a down side to moving weight back.... when your on a hill with good grip you start lifting the front.... there has been alot of guys play with weight balance here in the trials scene.... for a north south motor box combo, crank pulley sitting on the front axle centre line or just behind, for an east west combo from a front wheel drive because they are a more compact weight they can mount further back from around 6" off the firewall forward

from my truck following the rules that ends up with around 65-50%.... a more even split gives you better sidling control, truck doesn't flop as your uphill wheels follow the terrain, but for climbs you still want nose forward weight

There are those that buck the trend with rear mounts, but if you watch they cant attack the steep climbs they have to use momentum not HP and are stuffed on power on off climbs like terraced or platform climbs

But did you notice johns reply to us all, with a 4wd the front axle "anti-lift" so the high anti dive front axle does pull down .....

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Is the seat a long way behind the centre line? Or is the vehicle that light/you that heavy that it makes such a difference to weight distribution?

Combination of both Lewis, it only weighs 865kg i wiegh in and around 100kg, and the seat is halway between the centerline of the wheelbase and the rear axle.

It's light enough that i can tell it climbs worse with a adult passenger on board!

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Because it should be obvious, I'm not sure if I correctly understand what you are getting at when you said:

Another thought i've been having is how much effect the front to rear weight distribution would have on the position of the CofG

The front to rear weight distribution directly affects the fore & aft position of the C of G. By definition C of G is a notional point where a concentrated mass equal to the total mass will produce the same effect.

For equilibrium the sum of all of the moments must equal zero.

If:

the weight at the rear wheels is Wr

the weight at the front wheels is Wf

the total weight is Wt = (Wr + Wf)

the wheel base is Lw

the distance of the C of G ahead of the rear wheels is L1

the distance of the front wheels ahead of the C of G is L2

Taking moments about the rear wheels gives:

L1 = (Wf x Lw) / Wt

then L2 = Lw - L1

Alternatively for the same results take moments about the front to give:

L2 = (Wr x Lw) / Wt

then L1 = Lw - L2

The above is an example finding C of G give 2 known weight/masses.

Note when taking moments about the rear wheels the moment of the weight on the rear wheels is zero (Wr x 0.0 = 0.0) so it wasn't included in the 1st example .....

The method for finding the C of G for a large number of masses is the same i.e. add the moments for all of the masses, then divide by the total mass.

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snip ... snip

But did you notice johns reply to us all, with a 4wd the front axle "anti-lift" so the high anti dive front axle does pull down .....

But if you are going to consider anti-lift with a 4wd, then you should not be using the usual 2wd theory to determine %AS.

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But if you are going to consider anti-lift with a 4wd, then you should not be using the usual 2wd theory to determine %AS.

John I have been asking on a few forums over the years, if we still calc the anti's for our rigs given that the book stuff is all based on solid axle 2wd. Are you saying that our values are changed by 4wd and that both axles are driving and housings reacting?

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I don't see a problem using the 2WD method to compare behavior, when comparing apples with apples, so to speak.

If you want to be pedantic the %AS, %AD method/value are easily adjusted for 4WD, but when your being pedantic, what do you do when you reach the limit of traction at the front?

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I don't see a problem using the 2WD method to compare behavior, when comparing apples with apples, so to speak.

If you want to be pedantic the %AS, %AD method/value are easily adjusted for 4WD, but when your being pedantic, what do you do when you reach the limit of traction at the front?

Get the co driver to sit on the bull bar?

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More than five years after this excellent build...what can be said? Any problem/things to do different if done again? 

I think that a mix of this and Bill's Wildfing rear one link on leafs will give what I want for my 88.

 

FB_IMG_1549219103728.jpg

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12 hours ago, o_teunico said:

More than five years after this excellent build...

....and I don’t think Dan uses the forum anymore, sadly.

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Sadly not seen him around these parts for a long time!

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He might be persuaded to dip his toe back in for a discussion like this - he actually bought the trialler to Seven Sisters a year or two ago so it's still around.

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22 minutes ago, FridgeFreezer said:

He might be persuaded to dip his toe back in for a discussion like this - he actually bought the trialler to Seven Sisters a year or two ago so it's still around.

Get him back! :D 

 

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