Question delta - tadpole - quad steering different ?

[stormbird]

Hi all

So having ridden delta trikes for many years a Hase Kettwiesel and now Pythons I find the steering goes very very light at speed [ say above about 15 mph ]

Tadpoles - no idea never ridden one

Quads - now is this a tadpole with 4 wheels ?
I have ridden/raced 4 different ones and at speed the steering becomes heavy , and with a 180' bend on a race track it takes a good heave to get them round.

Does anyone think this is normal ?

I am enjoying this honest !

Paul

 

[DannyC]

I have never had the opportunity to look very closely at any of these cars and so I don't know the engineering behind their steering setup.
If we were to pretend that they were just a tadpole with an extra wheel for just a while then yes the faster you are travelling the quicker everything seems to happen.
With Go-Karts and the like under acceleration the front wheels "lift" (think of a motorbike doing a wheelie under hard acceleration). I'm not sure your legs are capable of getting the car to do a wheelie but the effect is probably still there.
The steering doesn't change in its operation as such though because it is all static and fixed linkages "X" degrees of movement at the input will always = "Y" degrees of movement at the output won't it?
But the distance traveled in FPS may make it seem more responsive and any transfer of weight to the rear or lifting of the front at all would make it seem lighter.
Also, on tight turns doesn't the weight transfer and one wheel gets less loaded?

 

[stormbird]

The steering doesn't change in its operation as such though because it is all static and fixed linkages "X" degrees of movement at the input will always = "Y" degrees of movement at the output won't it?
But the distance traveled in FPS may make it seem more responsive and any transfer of weight to the rear or lifting of the front at all would make it seem lighter.
Also, on tight turns doesn't the weight transfer and one wheel gets less loaded?

But I am saying this :-
' I have ridden/raced 4 different ones and at speed the steering becomes heavy , and with a 180' bend on a race track it takes a good heave to get them round.'
Which is exactly the opposite of what you are saying ?

 

[DannyC]

But I am saying this :-
' I have ridden/raced 4 different ones and at speed the steering becomes heavy , and with a 180' bend on a race track it takes a good heave to get them round.'
Which is exactly the opposite of what you are saying ?

I have re-read it and yes, silly me. Those were the words used. My mind translated them to starts heavy and gets lighter as speed increases. Doh!

 

[undertoad]

At first, I thought you were describing"understeer", where the car wants to go straight, instead of following the steering input.
But maybe you're talking about the actual physical effort needed to turn the steering ?
If so, then it must have something to do with weight transfer loading up the whole steering linkage, and the geometry causing some kind of bind ............. Maybe

 

[stormbird]

At first, I thought you were describing"understeer", where the car wants to go straight, instead of following the steering input.

This of course is all a bit tricky as now days most motor cars are engineered to be neutral when turning and of course we are now shielded from the actual steering forces by power steering.

But maybe you're talking about the actual physical effort needed to turn the steering ?
If so, then it must have something to do with weight transfer loading up the whole steering linkage, and the geometry causing some kind of bind ............. Maybe

That's the one , a snake around another car and moving from side to side on the track is easy however reach a bend and you have to haul really hard on the steering to get it to turn and maintain that pressure till the turn ends where it then sharply straightens up.

The first pedal car I drove [ in the 24hr race ] seemed to run out of turning it was obvious following other cars they could turn tighter, when I asked I was told the steering seems to lock up at some point ' just pull it harder ' it will turn more we think the chassis twists and causes the mechanism to bind !

As I said I have not ridden any tadpole trikes however my gut feeling is in a turn they tend to pivot around the single rear wheel and so could be quite easy to turn , maybe a quad is different because you are trying to make the 2 rear wheels turn ?

The only people on here currently with quads are Emiel and Geert I suspect they do not try to turn tightly at speed it is outside their operating envelope ?

Paul

 

[undertoad]

I recall reading an article about one of the early Baja off-road races - The author rode shotgun, with Arnold Swartznegger (of all people) driving, in a highly modified Jeep.
It seems that the power steering pump blew, or the belt broke, or something, early in the race, and when they told him about it, Arnold said "Vatt? Vass dere sometink wrong mit der steering?"

 

[Popshot]

A quad or taddy has a self centring steering effect from the caster. This gets more pronounced as you go faster so more effort is needed to steer.

A delta also has a self centring steering effect which also gets stronger with speed BUT the lack of two front wheels means it wants to tip and this counteracts the self centring and then overpowers it meaning any input then feels like power steering has kicked in.

 

[stormbird]

At last an answer I can understand !

Thanks Popshot

 

[Popshot]

It's useful having the steering get heavier with speed. If you quickly apply full lock at 2mph you just turn quickly. If you could do the same at 30mph you'd probably be going to the 1st aid station. Having to fight it slows the input down to a rate the machine can tolerate.

 

[stormbird]

I did briefly drive one like this :-

The steering was so ' quick ' if I looked over my shoulder it changed lanes !
Most unnerving , I was glad my legs were to long for it and I could say ' no thanks '

Paul

 

[undertoad]

I wonder if there was a way to adapt automotive variable ratio steering to pedal powered cars.
With rack and pinion steering, it has something to do with the spacing of the rack teeth, I think.
Otherwise, it would involve power steering ..........