117 replies to this topic

[jatwarks]

This new thread is to pull together topics that have taken over the "Lowest Race Car Ever" thread. Some of the ideas may have been discussed already in other threads, but I feel that combining them here would be useful.

http://forums.autosp...howtopic=159468

What is the concensus here about the Deltawing concept?

How are the principles different from those characteristics discussed in regard to Morgan 3-wheelers and Owen Greenwood's Mini trike?

The Morgan lacks traction from its single rear wheel; the mini trike has the advantage of the mini front end, but, consequently, front wheel drive.

The Deltawing, with rear drive and modern aerodynamics, would seem to overcome the faults of both.

The bottom line is, can the Deltawing prove that, in principle, the 3-ish wheel layout can be made to work well using modern techniques?

In solely layout terms, which of 2 front driven wheels or 2 rear driven wheels would be most effective given similar spec vehicles?

Intuitively, 2 front wheels give better braking and turning; 2 rear wheels give better traction.

For the purposes of this I'm considering fixed wheel positions only.

[cheapracer]

Problem is the car has been designed around a specific aerodynamic centre of pressure so proposing what it will handle like based on known 3 wheelers may be way off.

I find it strange how much money is being spent on the LeMans car build without running a few tests on some sort of basic mule.

Here's something interesting FWIW, 3 wheelers generally handle the opposite to what most people think, a F2R1 (tadpole or reverse trike) tends to understeer and a F1R2 tends to oversteer.

For the purposes of this I'm considering fixed wheel positions only.

Could have trouble at corners ....

Edited by cheapracer, 08 January 2012 - 16:05.

[rory57]

which of 2 front driven wheels or 2 rear driven wheels ... Intuitively, 2 front wheels give better braking and turning; 2 rear wheels give better traction [/quote]

Don't forget 3 wheel drive; (no front/rear differential required)

On another thread, moving the third wheel from one side to the other has been suggested.
Although this approach is excluded in the initial post of this thread it is in a way seen in those many fwd cars that lift their inside rear wheel when cornering



What is needed in a fast three wheeler is moveable ballast.



The third wheel could be half way down on one side. (May only be viable for Oval racing).

[24gerrard]

All very interesting.
Now imagine the last picture with no steering but electric drive and fine torque control to all three wheels.
Varying the torque through braking and steering input would result in cornering without the need for altering the front wheel angle.
In this case the vehicle would only be useable for right hand bends. (ovals as the man said)
Would it corner better than with four wheels with all the complex steering linkage etc?

This is not what I meant about moveing the rear tyre footprint and that is not allowed anyway in this thread but this is on the way to my idea.
Still not telling.

[jatwarks]

Still not telling.

A leaning wheel would move the contact patch from side to side; a longitudinal, horizontal axis of rotation through the wheel hub would move the contact patch towards the outside as the wheel leans into the corner. I hope this isn't the answer!

Initial turn-in would most likely move the rear of a lightweight vehicle inward, causing terminal understeer. Any means of moving the rear wheel from side to side, whilst in constant contact with the road surface, would do the same.

This would also require a motorcycle tyre with a contact patch limited by a curved tread. The larger the tyre cross section the less the contact patch will be offset (a ball would introduce no offset at all).

All wheel steering might be better.

[24gerrard]

A leaning wheel would move the contact patch from side to side; a longitudinal, horizontal axis of rotation through the wheel hub would move the contact patch towards the outside as the wheel leans into the corner. I hope this isn't the answer!

Initial turn-in would most likely move the rear of a lightweight vehicle inward, causing terminal understeer. Any means of moving the rear wheel from side to side, whilst in constant contact with the road surface, would do the same.

This would also require a motorcycle tyre with a contact patch limited by a curved tread. The larger the tyre cross section the less the contact patch will be offset (a ball would introduce no offset at all).

All wheel steering might be better.

OK
No steering on the front wheels at all (variable torque apply), no brakes only re-gen braking.
No rear brakes or rear drive and a steering hub center rear wheel with lean after turn in.
That do.
Oh and it has to be twin motor electric.
Fine torque control over each front wheel allows compensation for any understeer/oversteer changes during lean.
And before you say anything, who said anything about a road vehicle at this stage.
And no the American delta joke will not work.

Edited by 24gerrard, 08 January 2012 - 22:27.

[saudoso]

And no the American delta joke will not work.

In this I'll agree with you, Mr. Gerrard.

[bigleagueslider]

........And no the American delta joke will not work.

24gerrard,

When you say "American delta joke", are you referring to the DeltaWing car designed by a Brit (Ben Bowlby)?

slider

[cheapracer]

24gerrard,

When you say "American delta joke", are you referring to the DeltaWing car designed by a Brit (Ben Bowlby)?

Indeed he is and it will work just no one knows how well.

Even if it is successful I don't know where they can go with it from there though, can't see people buying either race cars or road cars. I do expect some cash to be generated through model and toy sales to children though.

Wish they would get rid of the stupid looking tail rudder and I expect front spoilers (those little multiple curved ones on the front sides that are common these days) to be added by race time and then they will complain about the extra drag ruining their performance on the straights ....

[24gerrard]

24gerrard,

When you say "American delta joke", are you referring to the DeltaWing car designed by a Brit (Ben Bowlby)?

slider

Hahah yes thats the one, you can have him slider.
Mind you it is the Americans who have bought into the idea.
We were happy just having the Reliant Robin for Delboy.

[Kelpiecross]

[quote name='cheapracer' date='Jan 9 2012, 03:02' post='5472557']


Here's something interesting FWIW, 3 wheelers generally handle the opposite to what most people think, a F2R1 (tadpole or reverse trike) tends to understeer and a F1R2 tends to oversteer.

Are sure abiut this Cheapy? - I wouldn't have thought so. Surely the F2R1 would oversteer especially if the rear was the driven wheel.

From what I have seen F2R1 is quite a reasonable idea (I would prefer the fronts being driven).

F1R2 seems to be verging on the suicidal. After seeing Clarkson in the Reliant which kept lying down on its side - and didn't they ban F1R2 agricultural trikes in Oz because they were too dangerous?

I can't imagine any F1R2 racer being successful.

[jatwarks]

I would expect the following on track; say the elbow past the pits at Mallory Park:

F2R1 (rear drive Morgan) - Initial understeer followed by oversteer as the driven rear wheel drifts out.

F1R2 (rear drive Reliant) - Understeer as the contraption fails to respond to any driver input !

F1R2 (front drive Bond Equipe) - Who knows !! Probably understeer. Makes the Reliant seem like a supercar.

F2R1 (front drive Greenwood Mini) - Understeer, just like its Mini parent.

[24gerrard]

The secret to mini handling was to add negative camber and toe out on the rear.

[Greg Locock]

Are sure abiut this Cheapy? - I wouldn't have thought so. Surely the F2R1 would oversteer especially if the rear was the driven wheel.

From what I have seen F2R1 is quite a reasonable idea (I would prefer the fronts being driven).

F1R2 seems to be verging on the suicidal. After seeing Clarkson in the Reliant which kept lying down on its side - and didn't they ban F1R2 agricultural trikes in Oz because they were too dangerous?

I can't imagine any F1R2 racer being successful.

F2R1 only oversteers when traction forces are applied to the rear wheel. The reason it is understeer in cornering is that you don't get any lateral load transfer on the rear wheel, so it just keeps on gripping. Obviously it is possible to screw this up, but as a general trend cheapy is right.

F1R2 is fairly spinny, by exactly the same argument. The real world problem is the tendency to roll over under combined braking and steering.

Off road trikes have been banned just about everywhere, that's why the world rides quad bikes.

[24gerrard]

F2R1 only oversteers when traction forces are applied to the rear wheel. The reason it is understeer in cornering is that you don't get any lateral load transfer on the rear wheel, so it just keeps on gripping. Obviously it is possible to screw this up, but as a general trend cheapy is right.

F1R2 is fairly spinny, by exactly the same argument. The real world problem is the tendency to roll over under combined braking and steering.

Off road trikes have been banned just about everywhere, that's why the world rides quad bikes.

With a steering rear wheel and variable torque applied to the front two, it becomes possible to control over/under steer.
If you also control the leen on the rear wheel, you can control weight transfer as well.
With no steering on the front two wheels, the design of front suspension, aero and packaging becomes much better and far lighter.
It allows a super downforce undertray with twin diffusers and the electric power gives a far better design and control on powertrain cooling.
Using re-generating on the two front wheel motors gives brakes which does away with the need for conventional wheel brakes.
making the design even lighter and simpler.

By comparison quads are a joke, a bit like placing the Eiffel tower on a penny farthing.
OK if you corner slow and carefuly enough but not serious performance vehicles.

Edited by 24gerrard, 09 January 2012 - 22:20.

[Catalina Park]

Off road trikes have been banned just about everywhere, that's why the world rides quad bikes.

I used to love flogging around a farm on a Honda trike, the best way to ride one was to steer with your feet! They had no diff so they would just push straight into a tree. If you put all your weight on the outer foot peg and pull up with the opposite hand to lean the trike outwards the inner wheel would slip and then the trike would turn. You could get oversteer or understeer just from changing weight with your feet.

Quads used to be similar till they started fitting diffs. I used to like to lean it onto two wheels when cornering at least you knew what it was doing!
Modern ones are much safer and you don't have to resort to stupidity to get around a corner.

[GeoffR]

By comparison quads are a joke, a bit like placing the Eiffel tower on a penny farthing.
OK if you corner slow and carefuly enough but not serious performance vehicles.

Hmmmm .......

[Kelpiecross]

[quote name='Greg Locock' date='Jan 10 2012, 08:39' post='5474004']
F2R1 only oversteers when traction forces are applied to the rear wheel. The reason it is understeer in cornering is that you don't get any lateral load transfer on the rear wheel, so it just keeps on gripping. Obviously it is possible to screw this up, but as a general trend cheapy is right.

This line of reasoning seems quite logical - so presumably a racing Mini with one central wheel at the back would actually be able to generate more cornering force than a normal four-wheeled Mini?

As Cheapy suggests (I think) a basic bare frame "mule" that could be simply converted from F2R1 to F2R2 and maybe with the F2R1 that could be tested with FWD or rear drive would be interesting.

I don't think I would bother testing F1R2.

[jatwarks]

This line of reasoning seems quite logical - so presumably a racing Mini with one central wheel at the back would actually be able to generate more cornering force than a normal four-wheeled Mini?

Does anyone have access to circuit lap records from the 60s & 70s?

I'm certain Owen Greenwood held many motorcycle 3-wheeler records in his mini trike. A comparison with period car records held by Minis would go some way to providing factual evidence, one way or another.

[Magoo]

his line of reasoning seems quite logical - so presumably a racing Mini with one central wheel at the back would actually be able to generate more cornering force than a normal four-wheeled Mini?

Well played.

[24gerrard]

Hmmmm .......

Hmmm what?
Just because it looks good and is fun, does not make it fast.
Top heavy is what it is.

One problem with any three wheeler off road is the three ply tracks with a high rough center.
It is not possible to compare three to four or two wheels on such surfaces.

[cheapracer]

If you can stop laughing long enough notice they oversteer severely ..

[rory57]

If you can stop laughing long enough notice they oversteer severely ..

I like the stabilisers on the "convertible".

Many will have driven 1F 2R with front wheel drive (and electric drive).
Fairground dodgems. About the useful limit for that layout I think ( I never tried a Fwd Bond, I hope it stays that way)

[Greg Locock]

"This line of reasoning seems quite logical - so presumably a racing Mini with one central wheel at the back would actually be able to generate more cornering force than a normal four-wheeled Mini?"

Doesn't seem likely to me, on one set of assumptions, but yes, on another set. Define your experiment exactly and the answer will fall out. Or leave it all woolly and then you can start another interminable 'power or torque' thread.

What is the weight distribution for your cars?

what are you assuming about roll stiffness distribution?

Critically, are you assuming a typical tire load sensitivity curve, or are you ignoring it? if you ignore it the answer is very boring.

[Kelpiecross]

"This line of reasoning seems quite logical - so presumably a racing Mini with one central wheel at the back would actually be able to generate more cornering force than a normal four-wheeled Mini?"

Doesn't seem likely to me, on one set of assumptions, but yes, on another set. Define your experiment exactly and the answer will fall out. Or leave it all woolly and then you can start another interminable 'power or torque' thread.

What is the weight distribution for your cars?

what are you assuming about roll stiffness distribution?

Critically, are you assuming a typical tire load sensitivity curve, or are you ignoring it? if you ignore it the answer is very boring.

I certainly wasn't advocationg one-wheel-at-the-back - I just wondered if (against apparent common sense) that it might be better.
I didn't consider before that F2R1 would have no roll stiffness at all at the back - leaving a very big job for the front suspension to control roll.
I think I will stick with four wheels.

[Greg Locock]

I certainly wasn't advocationg one-wheel-at-the-back - I just wondered if (against apparent common sense) that it might be better.
I didn't consider before that F2R1 would have no roll stiffness at all at the back - leaving a very big job for the front suspension to control roll.
I think I will stick with four wheels.

I don't think you are missing anything, the only exception would be if the CG was very far forward. If you think about it one of the main objectives of a designer is to maximise track/cgz (up to a point), the effective track of a 3 wheeler is less than the lateral wheel spacing.

I'm not opposed to F2R1 3 wheelers in their place, but for belting round corners, nah. I was always a bit unhappy that we ended with 1F2R on two of our solar cars, but handling is not a priority in that race. Aerodynamically there is no doubt it is a better solution, for that sort of shape.

[24gerrard]

I don't think you are missing anything, the only exception would be if the CG was very far forward. If you think about it one of the main objectives of a designer is to maximise track/cgz (up to a point), the effective track of a 3 wheeler is less than the lateral wheel spacing.

I'm not opposed to F2R1 3 wheelers in their place, but for belting round corners, nah. I was always a bit unhappy that we ended with 1F2R on two of our solar cars, but handling is not a priority in that race. Aerodynamically there is no doubt it is a better solution, for that sort of shape.

Not sure about aero.
Yes 1f2r for streamlining only but that is all.
High speed with downforce I think 2f 1r, less in the way of usable airflow at the back.

Leaning the rear wheel and steering it controls weight transfer and rear roll.
independent motors on the front negate the need for any conventional brakes and allow control of over and understear and front weight transfer.
Using front suspension only for controlling roll etc would be a benefit not a negative.
With no need for front steering the design would be optimum as would front aero and cooling.
IMO it is the way to go for solely electric so as to match and beat ic performance.

[cheapracer]

Not sure about aero.
Yes 1f2r for streamlining only but that is all.
High speed with downforce I think 2f 1r, less in the way of usable airflow at the back.

Leaning the rear wheel and steering it controls weight transfer and rear roll.
independent motors on the front negate the need for any conventional brakes and allow control of over and understear and front weight transfer.
Using front suspension only for controlling roll etc would be a benefit not a negative.
With no need for front steering the design would be optimum as would front aero and cooling.
IMO it is the way to go for solely electric so as to match and beat ic performance.

Google Corbin Sparrow and Corbin Raven.

http://www.corbin.co...ws/053107a.html

Edited by cheapracer, 11 January 2012 - 19:48.

[saudoso]

The two things I've 'driven' that had rear wheel steering - shopping carts backwards and an Aerobuero - weren't fond of moving in a straight line once their straight movement was disturbed...

I guess rear steeirng goes the same path 1F2R, unstable.

Edited by saudoso, 11 January 2012 - 20:49.

[cheapracer]

I guess rear steeirng goes the same path 1F2R, unstable.

Well I think we all base that on our experiences of driving vehicles in reverse that are not built specifically to do that and I think it's a hard bias to break.

Having driven a few forklifts tells me it would certainly be ideal for a city car and I'm sure today's stability systems could make it safe enough for open road use.

[saudoso]

Well I think we all base that on our experiences of driving vehicles in reverse that are not built specifically to do that and I think it's a hard bias to break.

Having driven a few forklifts tells me it would certainly be ideal for a city car and I'm sure today's stability systems could make it safe enough for open road use.

So we agree they are on the unstable side, right? Like the A Class or a F16.

Edited by saudoso, 11 January 2012 - 21:26.

[24gerrard]

So we agree they are on the unstable side, right? Like the A Class or a F16.

Yesterdays unstable is todays fly by wire quick reaction vehicle.

[saudoso]

Yesterdays unstable is todays fly by wire quick reaction vehicle.

That's true for the F16.

The A Class is more the case of patching a huge **** up. There is nothing to gain for a road car to behave like that.

Edited by saudoso, 12 January 2012 - 01:00.

[Greg Locock]

Shrugs, build a proto, find out. I'm sure it can be made stable and controllable (rear wheel steer is very effective for stability), the question is whether it is acceptable for the target market. Whatever that is.

[cheapracer]

So we agree they are on the unstable side, right? Like the A Class or a F16.

No you missed my point, we believe it will be unstable because our brains have been trained to that, as Greg says you would have to build a specific rear steered proto to work out what to do differently.

Example is you would have positive caster whereas now when you reverse your street car, you have negative caster which would account for 90% of the instability. Positive Ackerman steering wouldn't be helping either.

There is no doubt that high speed sudden direction changes would be an issue as you are swinging the rear of the car outwards in the direction that centrifugal force wants to take it, that's why I suggested modern stability control to help contain that loss of control - otherwise for city use with modern tyres should be fine (the usual suspects will have car control issues regardless of what they were driving).

FWIW anyone who ha been in big warehouses know what forklift drivers get up to at quite decent speeds and they have quite good stability

Edited by cheapracer, 12 January 2012 - 05:38.

[Catalina Park]

Forklifts are not a real good example of rear steer even though it is what most people have seen and maybe driven that is rear steer, the suspension angles are all wrong to what you would want to road travel, plus the counterweight on the rear will not help any comparison. They are not very stable if you try a swerve and recover!

The last forklift I drove had a form of stability control, when you got it to a certain lean it would try to weight jack the steer axle to avoid it tipping over!

[cheapracer]

Forklifts are not a real good example of rear steer even though it is what most people have seen and maybe driven that is rear steer, the suspension angles are all wrong to what you would want to road travel,

Sure, but a much better example than driving a street car in reverse and you're right, the weight bob isn't much of a help swinging the ass around.

When pulling engines out of a container on the back of a truck with a 25 foot boom, my brother got to a point where he would reverse out then go forward turning and 2 wheeling the fork (from the very high CoG) while controlling it by lowering the boom - don't try this at home

[jatwarks]

In my expeerience fork lift drivers tend to drive in reverse when they are not positioning loads; more familiar, and habit, having the steering leading.

Some consider driving backwards with loaded forks to be safer in a busy environment.

Anyway, back to the topic. A mixture of front & rear steer vehicles on public roads would probably lead to more bumps & scrapes between them.

A rear steer vehicle, with modern stability levels, might re-introduce the art of control at the limits of grip, as rotation about the front wheels gives early feedback to the drivers backside!

Edited by jatwarks, 12 January 2012 - 08:14.

[Slumberer]

Thrust SSC was RWS. When it was first suggested people thought they were bonkers.
As I remember it they used a mini and extended the rear chassis out to make a scale version of the SSC wheelbase to see whether it would work.
They said it was fantastic fun to drive and very stable, BUT only when there was absolutely no slack in any of the linkages at all, else it was dreadful.

I wonder how a RWS car would react to a skid?

[jatwarks]

Thrust SSC was RWS. When it was first suggested people thought they were bonkers.
As I remember it they used a mini and extended the rear chassis out to make a scale version of the SSC wheelbase to see whether it would work.
They said it was fantastic fun to drive and very stable, BUT only when there was absolutely no slack in any of the linkages at all, else it was dreadful.

The long wheelbase would have helped. Not necessarily suited to road use.

What was the turning circle of SSC ? How many miles ?

[kikiturbo2]

for a normal road car, pure rear wheel steer would be a disaster.... in a corner, you need the rear wheels to have some toe in, in order to have any traction from the rear wheels, not massive toe out..

[BRG]

A three wheel car with rear wheel steering? Try this for size.. Not a sucess with some suggestion that the steering was a problem.

[saudoso]

A three wheel car with rear wheel steering? Try this for size.. Not a sucess with some suggestion that the steering was a problem.

In his 1988 book The Age of Heretics, author Art Kleiner maintained the real reason Chrysler refused to produce the car was because bankers had threatened to recall their loans, feeling the car would destroy sales for vehicles already in the distribution channels and second-hand cars.

Oooooh boy....

[saudoso]

No you missed my point, we believe it will be unstable because our brains have been trained to that, as Greg says you would have to build a specific rear steered proto to work out what to do differently.
...
There is no doubt that high speed sudden direction changes would be an issue as you are swinging the rear of the car outwards in the direction that centrifugal force wants to take it, that's why I suggested modern stability control to help contain that loss of control - otherwise for city use with modern tyres should be fine (the usual suspects will have car control issues regardless of what they were driving).

FWIW anyone who ha been in big warehouses know what forklift drivers get up to at quite decent speeds and they have quite good stability

I guess I didn't. It would need electronic aid to be road viable.

Example is you would have positive caster whereas now when you reverse your street car, you have negative caster which would account for 90% of the instability. Positive Ackerman steering wouldn't be helping either.

I get your point here, a reverse 180 is among the biggest joys cheapest thrills of reckless driving.

But anyway, even if you had positive caster in the rear wheel steering car, wouldn't it's expected behaviour to be keep going as it is instead of realigning the wheels like in a front steering one? And since it's spinning already, to keep spinning? That's the case with the shopping cart.

EDIT:
FS, positive caster = Positive directional stability - tries to get back moving straight
FS, negative caster = Negative directional stability - goes berserk
RS, negative caster = Negative directional stability - goes berserk
RS, positive caster = Neutral directional stability - stay as you where

Edited by saudoso, 12 January 2012 - 18:06.

[24gerrard]

I guess I didn't. It would need electronic aid to be road viable.



I get your point here, a reverse 180 is among the biggest joys cheapest thrills of reckless driving.

But anyway, even if you had positive caster in the rear wheel steering car, wouldn't it's expected behaviour to be keep going as it is instead of realigning the wheels like in a front steering one? And since it's spinning already, to keep spinning? That's the case with the shopping cart.

EDIT:
FS, positive caster = Positive directional stability - tries to get back moving straight
FS, negative caster = Negative directional stability - goes berserk
RS, negative caster = Negative directional stability - goes berserk
RS, positive caster = Neutral directional stability - stay as you where

Not if the weight is mainly over the front two wheels and the drive is split to the front two drive wheels
and the torque split is electronicaly controlled to assist with lateral G varying through cornering.
Just like a McLaren F1 braked (four foot pedals remember Gordon?) rear axle but on the front but fully electronic including electric re-gen front baking.
Electronic over/under steer in effect.
Full electricly controled handling if you wish.
Would be an interesting project.

[saudoso]

Not if the weight is mainly over the front two wheels and the drive is split to the front two drive wheels
and the torque split is electronicaly controlled to assist with lateral G varying through cornering.
Just like a McLaren F1 braked (four foot pedals remember Gordon?) rear axle but on the front but fully electronic including electric re-gen front baking.
Electronic over/under steer in effect.
Full electricly controled handling if you wish.
Would be an interesting project.

Now we are back to the point of a fly by wire vehicle. Which was the begining of this. The setup is unstable and needs electronic assistance.

[24gerrard]

Now we are back to the point of a fly by wire vehicle. Which was the begining of this. The setup is unstable and needs electronic assistance.

Why would it be unstable?
Stability is not the issue.
Control is.

[saudoso]

Why would it be unstable?
Stability is not the issue.
Control is.

Directional stability. I guess it is an issue. And unless you are planning to go dogfighting with your trike, it counts more than extreme maneuverability.

Edited by saudoso, 12 January 2012 - 22:47.

[Greg Locock]

If anyone were serious about this, as opposed to blowing hot air, there are several SAE papers on the subject. The only one I have to hand is by the hairy man and my ex supervisor, 930266. One interesting plot is where they move the centre of steering around using front and rear steer, generally a more forward rotation point is perceived as less stable by (experienced, I suspect) drivers.

Also relevant would be the results from an experiment with an oversteering chair. This is a compliantly mounted chair that swivels under lateral g.
Guess what, it really unsettles drivers when it is more compliant at the back, and vice versa.

There's also a Japanese SAE paper on novice drivers with rear wheel steer. haven't read it.

[saudoso]

I guess the point here is blowing hot air, it sure seems so ;)

In a serious note: I'd like to read it, but won't spare the money for the sake of proving a point (or not) to 24gerrard.