CleaR Motorsport. A new beginning in Cheshire. Your chassis tunning specialist.

[LoneWolf]

The spring platforms are quite wound up, which paired with the taller top hats, are making the dampers hit full extension IMHO.

A longer damper should be on the cards here to solve the problem, from what I can see. Or a shorter spring.

Might be worth trying the old short top hats as well? As those might give you some more travel in this specific case.

[Ian Kinder (Bagpuss) - Joint Peak District AO]

10 minutes ago, CosKev said:

Get some shock covers on them once you are happy👍

Give the threads above the spring seats a good squirt of ACF50 before putting the covers on🤓

One we've got them to the heights were happy with. I'm not likely going to need to adjust them again.

[joolz]

16 hours ago, harrypotter said:

 

Excuse my ignorance but what is the W fig related to and why is 50% desirable.

50% is only desirable if that's what you want from the car, ie it says the centre of mass is in the middle of the 4 tyre patches, however it's a misleading number because 1)  you might not want that it depends what you are doing with the car and your personal handling preferences and 2) you can have a number close to 50% and yet still have a big diagonal tyre load inbalance, see Ian's car has 16kg across one diagonal (very close) but 62kg across the other. Sadly because of the way the car pivots across the evenly load-spread diagonal the only way to address that is to move weight in the car, you won't sort it on spring platform height  changes alone.

[Maurici- CleaR Motorsport]

4 minutes ago, joolz said:

50% is only desirable if that's what you want from the car, ie it says the centre of mass is in the middle of the 4 tyre patches, however it's a misleading number because 1)  you might not want that it depends what you are doing with the car and your personal handling preferences and 2) you can have a number close to 50% and yet still have a big diagonal tyre load inbalance, see Ian's car has 16kg across one diagonal (very close) but 62kg across the other. Sadly because of the way the car pivots across the evenly load-spread diagonal the only way to address that is to move weight in the car, you won't sort it on spring platform height  changes alone.

Yes, but, you are mixing concepts here.

 

Unless you do oval racing, or you like braking locking front wheels, there is no real reason of having positive or negative wedge.

 

You are mixing static weight distribution (construction) and dynamic weight transfer.

 

Cross weight its never been misleading, is a tool to mitigate the inherent unbalance due the non symmetrical construction of a car. Particularly important in a very light and small two seater.

 

 

[harrypotter]

14 minutes ago, joolz said:

50% is only desirable if that's what you want from the car, ie it says the centre of mass is in the middle of the 4 tyre patches, however it's a misleading number because 1)  you might not want that it depends what you are doing with the car and your personal handling preferences and 2) you can have a number close to 50% and yet still have a big diagonal tyre load inbalance, see Ian's car has 16kg across one diagonal (very close) but 62kg across the other. Sadly because of the way the car pivots across the evenly load-spread diagonal the only way to address that is to move weight in the car, you won't sort it on spring platform height  changes alone.

Given that very few cars are ever symetrical weight wise, what would your criteria be for a road going westfield if not 50%?

[joolz]

1 hour ago, harrypotter said:

Given that very few cars are ever symetrical weight wise, what would your criteria be for a road going westfield if not 50%?

That's great for a road going car (or regular circuit race car for that matter) , but you asked why is 50 percent desirable and i suggested it's not always desirable.

Drag racing for instance, or you have a massively powerful car but don't like corners, so you maximise traction at the expense of overall grip.

There's a great many cases where having the centre of mass of the car actually in the centre of the 4 contact patches is a very good idea, and other cases when it isn't.

[joolz]

1 hour ago, Maurici- CleaR Motorsport said:

Yes, but, you are mixing concepts here.

 

Unless you do oval racing, or you like braking locking front wheels, there is no real reason of having positive or negative wedge.

 

You are mixing static weight distribution (construction) and dynamic weight transfer.

 

Cross weight its never been misleading, is a tool to mitigate the inherent unbalance due the non symmetrical construction of a car. Particularly important in a very light and small two seater.

 

 

Yes for a great many cases having the mass of the car exactly within the contact patches is a good thing, but it's not a number to go fixating on if say you do drag racing, or as you say ovals only. That was kind of my point .. whist the 50 percent equal load spread might initially appear to be all things to all men (other genders are available..) it's actually not. And as we can see from Ian's car, it's actually misleading because the corner weight loads are very dis-similar.

 

Also not sure I'm mixing anything. The only thing a static load test can tell you is the static load. it tells you nothing about relative spring rates, roll centres, damper rates etc which impact on dynamic transfer. The only thing a static load test tells you is the load at each contact patch when the car is static. As such, (westies and their ilk being somewhat eavenly spread of load in the first place) if you add say 70 or 80kg of driver directly over the offside rear wheel the only way you are going to even the static load is to add 80kg over the nearside rear wheel, or remove 80kg from the offside in the first place. No amount of damper spring platform adjustments changes  the fact you've added 80kg of actual physical weight to one corner of the car, though robbing Peter to pay Paul in corner weight adjustments may as you say mitigate (reduce, make less severe) any cross weights, it's not the same as actually physically having a platform with an even mass distribution.

[Maurici- CleaR Motorsport]

1 minute ago, joolz said:

but it's not a number to go fixating on if say you do drag racing, or as you say ovals only. That was kind of my point ..

So... Not the case here. We are talking about Ian's car, and handling. Not drag racing nor ovals. I get your point, but I honestly doubt ill ever have in my scales a car that will not aim to 50% wedge.

 

3 minutes ago, joolz said:

it's not the same as actually physically having a platform with an even mass distribution.

We do agree here. I think. You just seem to like to do the long worded version.

[harrypotter]

5 hours ago, Maurici- CleaR Motorsport said:

The car on its 4 wheels on the floor wasn't at full extension. So initially i didn't even expect that to happen... Shouldn't be a preload problem. But yes sounds like is hitting the top at overextension.

With the right rebound control, that should not happen either... And if it did at the end of its travel, shouldn't be as harsh as I heard in the videos Ian sent me once he got home... As it should be some sort of soft stop. 

We'll investigate further but the problem here seems to be the nature of the hardware, good or bad, isn't liking the current ride height.

Im surprised other people found themselves with this problem too, as I have never encountered that.  Maybe im too used to posher hardware.

 

After a bump a correctly valved  damper should control the body enough for preventing to go any higher than the resting position... At least with any sort of speed (by the end of its travel).

 

Lowering significantly the car is out of the picture as is a full road going car....

Stiffening it too much too, as is s fully road going car.

 

Some compromises may need to be made that Ill discuss with Ian on Thursday.

Thanks for the feed back. 

Unbeknown to me when I bought my car the rear suspension was set by the previous owner to deliberately stiffen it enough for drifting! He had achieved this by preloading the springs so much that there was no movement until carrying two people and driving over potholes in the circuit paddock. This over came the preloaded springs for a millisecond before banging back fully open. Strangely on the smooth track it drove well; very stiff but cornered well. Reducing the excessive preload solved the problem.

I wonder if the s2000 has a sump so low that the front suspension has to be raised more than other setups? That would also mean that the rear has to be raised more to achieve the correct rake. Just a thought.

In an ideal world only the minimal amounts of preload should be required to adjust suspension heights on low weight cars such as ours. 

Am I right in thinking that ideally the damper should be approx 2/3rds open when resting on the wheels for a road car?

[harrypotter]

1 hour ago, joolz said:

That's great for a road going car (or regular circuit race car for that matter) , but you asked why is 50 percent desirable and i suggested it's not always desirable.

Drag racing for instance, or you have a massively powerful car but don't like corners, so you maximise traction at the expense of overall grip.

There's a great many cases where having the centre of mass of the car actually in the centre of the 4 contact patches is a very good idea, and other cases when it isn't.

So you agree that 50% is ok for a westfield? 

For a drag car with the mass towards the rear would you still not want the same 50% diagonal distribution?

[joolz]

2 minutes ago, harrypotter said:

So you agree that 50% is ok for a westfield? 

For a drag car with the mass towards the rear would you still not want the same 50% diagonal distribution?

From what i understand (and Maurici will see this and tells me hopefully) .. that wedge number is just the percentage of the two diagonal cross weights compared to the total weight. In Ian's case even though the wedge number is great, his corner weights are miles out, and that's because presumably he is sat in the drivers seat.

What it means in Ian's case is that (just going solely off the static load results)  his left rear tyre will lose grip before his right rear tyre (because it carries less load), and his front left will loose grip before the front right (again because it carries less load).

So, if Ian were to take his car drag racing (because you mentioned that so i will go with that scenario), he might find his start is compromised because his left rear tyre spins before the right rear tyre. You can now see that even though the wedge appears ideal at 50 percent, Ian's car would be compromised in terms of startline traction, and front brake traction, all other things being equal.

 It's semantics to some extent because once a car is built it's very hard to move 20 or 30 kg or more of load to equalise the mass distribution, and maybe that is why Maurici likes to see that figure close to 50 percent, because it means that it's as close as he can get it *without* physically moving weight in the car.

[Ian Kinder (Bagpuss) - Joint Peak District AO]

44 minutes ago, harrypotter said:

Thanks for the feed back. 

Unbeknown to me when I bought my car the rear suspension was set by the previous owner to deliberately stiffen it enough for drifting! He had achieved this by preloading the springs so much that there was no movement until carrying two people and driving over potholes in the circuit paddock. This over came the preloaded springs for a millisecond before banging back fully open. Strangely on the smooth track it drove well; very stiff but cornered well. Reducing the excessive preload solved the problem.

 

Wow, that sounds interesting/challenging!

 

44 minutes ago, harrypotter said:

I wonder if the s2000 has a sump so low that the front suspension has to be raised more than other setups? That would also mean that the rear has to be raised more to achieve the correct rake. Just a thought.

 

I'm aiming for 140mm front and 165mm rear.

 

The gearbox hoop is lower than an S2000 sump (just).

 

 

 

 

 

 

[Maurici- CleaR Motorsport]

44 minutes ago, joolz said:

Many things. most of them correct IMHO

but...

44 minutes ago, joolz said:

From what i understand (and Maurici will see this and tells me hopefully) .. that wedge number is just the percentage of the two diagonal cross weights compared to the total weight.

1 diagonal really... as the actual wedge term is used in oval more than circuit. but... semantics. I use it to aim for a 50% (neutral wedge) that means 50/50 diagonals. The reason I say is 1 diagonal... is because the pure term is positive or negative wedge for left handed turning only cars not the case here, so you are correct, but I thought I may as well explain why the scales use the term wedge rather than diagonal %.

 

44 minutes ago, joolz said:

and that's because presumably he is sat in the drivers seat

correct.

44 minutes ago, joolz said:

his left rear tyre will lose grip before his right rear tyre (because it carries less load), and his front left will loose grip before the front right (again because it carries less load).

Correct if you were applying solely planar loads, but isn't the case once the car is moving. It naturally rolls and transfers loads, doesn't pulls laterally.

44 minutes ago, joolz said:

So, if Ian were to take his car drag racing (because you mentioned that so i will go with that scenario), he might find his start is compromised because his left rear tyre spins before the right rear tyre.

correct to an extent. for drag racing, i would aim to 50% weight at the rear due the purely static start and lack of bends to deal (on the road anyway, as you have to steer a lot in a proper drag car). For any other scenario, I would trust to a rather decent LSD to take care of the first few metres till the loads have transferred to the back and the car has acted as I've said above as a wonky table. the masses will rotate from the roll centre height diagonally to load the unladen wheel. As soon as there is ANY sort of acceleration the dynamic transfer is actually huge.

44 minutes ago, joolz said:

and front brake traction, all other things being equal.

Braking is slightly different than accelerating. You can't brake without movement, therefore it will be a rather immediate weight transfer to the unladen corner (wonky table again) equalizing pretty much exactly the front load. (depending on the car stiffness you may be able to slam the brakes more aggressively or less). In another words, a softish car will ask for quite a lot of preload (progressive braking) rather than slaming the brakes, but we are not digging that deep. I don't do hardware changes when setting a car so its out of scope. 

 

44 minutes ago, joolz said:

Maurici likes to see that figure close to 50 percent, because it means that it's as close as he can get it *without* physically moving weight in the car.

 

It isn't me who likes it... I can quote some authors, and engineers, and racers... but... Milliken and Milliken is a good start. Or even the static load diagram of a braking or cornering scenario...

The weight doesn't moves in a planar way, but rotates from the intersection of the roll centre height and the CG (the neutral wedge point) and this is why you will never adjust a car that is meant to steer, brake or accelerate to a 50% in the axles, unless you can do the same in all 4 of them corners (rather difficult if isn't a single seater, or something dedicated) because when the weight gets transferred you will end with massive differences in the front or rear axle...

[Maurici- CleaR Motorsport]

1 hour ago, harrypotter said:

Am I right in thinking that ideally the damper should be approx 2/3rds open when resting on the wheels for a road car?

could be a rule of thumb, yes.

[joolz]

1 hour ago, harrypotter said:

 

Unbeknown to me when I bought my car the rear suspension was set by the previous owner to deliberately stiffen it enough for drifting! He had achieved this by preloading the springs so much that there was no movement until carrying two people

My track car was set up just lie that when I bought it, very short dampers front and rear with no droop unless carrying occupants. Sadly it wasn't a drift machine, it was a determined under-steerer. I have yet to try it out with its new suspension, but hope there's some improvement .