43 replies to this topic

[mariner]

I have critizised the weight of bike engined cars in an earlier thread because I can't see why "adding two wheels and a body" to a 190kg superbike results in a 400kg car. Just critisizing without suggesting solutions is pretty lame so I gaive you the "kneel-er-car". No claims it is new in any way but it is an attempt to bridge the gap between a bike and a car still using the high power bike engine.

I have done a very crude sketch in the imageshack link later on but first some logic.

A 1200c superbike has up to 150bhp ( road trim) and weighs 190kg or less. It can carry two people so why is the equivalent car at 400kg+? I think it is a question of platform size, bike-engined cars are just the same size as similar car engined cars ( compare a Radical to a Lotus 23). So the large plan area drives up weight.

The large plan area is , I think, the result of driver length and pursuit of high lateral G. A semi reclining driver uses up 60ins/1.5m and if the car is rear engined, you can add at least 20" for the engine and 10" for the bell housing and half a diff. so the wheelbase arives at 90"/2.25m.You can do better on front engined cars by overlapping the drivers leg and engine ( like a U2 ) but the need for rearward weight means the engine has to lie well behind the front wheels so back tot he magic 90"/2.25m again. A sensible track/wheelbase ratio and the desire for wider and wider tyres leads to tracks of 60"/1.m+ and this gives a width of 68"/1.7m or more.

I will agree that most successful sports cars are between 90" and 104" wheelbase and widths have grown to boost lateral G but there ought to be some sort of alternative to conventional wisdom that is at least worth looking at.

So the Kneel-er-car is just what is says. The driver and passenger do not sit or lie in the car they kneel down in it. this reduces wheelbase as a kneeling driver needs only 45" of car length not 60". Kneeling is not new all modern racing sidecar bikes are kneelers and they go very fast, including on road tracks like the IoM TT.

http://www.lcr-sidec...ae02/index.html

Kneeling requires the use of handlebar steering not a steering wheel which again has been developed on sidecars.

http://www.lcr-sidec...es/racing3a.jpg

By now you may be getting the argument! By using a kneeling position the wheelbase can be cut to 60"/1.5m. That allows the width to be reduced to 46"/1.17m. The wheels are reduced to a 10" or 12" rim with a maximum section or 175mm. That further cuts weight and maintains the sprung/unsprung ratio with the lower chsasis weight. The chassis is simply a backbone with a spaceframe around the engine. The bodywork is just a front nosecone and a rear engine cover with pasengers exposed.

The final layout is sketched here with some dimensions and chassis detail. ( can anyone tell me how to make it a bigger image !!). Cheapy do you want it emailed?



Hopefully you can see the sketch and the basic dimensions of the car and chassis. I think 300kg is within reach based on two reference points. Firstly the kneeler sidecars by LCR weigh only 220kg and I am adding only one extra wheel and road equipment for 300kg. The sidecars use a superbike engine and have full bodywork. Secondly if you take the "typical" 400kg bike powered car and say 70kg is the powerpack and 30kg for non scalable items then there is 300kg left to scale down. The Kneel-er-car is 33% smaller in length and width so 200kg should be Ok. Add back the 70kg and the 30kg yields 300kg weight target.

The 33% weight cut means that the tyre width to weight ratio ie loading is not too much above a conventional car with 200mm+ tyre sizes and 400kg.

So I think it is posible to build a four wheel car at only 300kg or less by going to the kneeling layout. Frontal area is cut by 33% due to the 46"/1.17m width versus 68-70" so actual acceleration ( i.e torque less drag at each speed) should go up by 33% versus a conventional car. Obviously the passengers dont get lighter so that will be more like 25-28% in reality but still a big gain.

What are the problems, basically steering,lateral G and safety I think. The driver has to get used to a very different and more immediate driving experience via the handlebars but sidecars manage. Lateral G is going to be less due to narrower track and higher CG as the passengers bums are up in the air. However there is a hidden benfit of the very narrow width in that real road driving is limited to one side of the road and a narrower car can take a gentler line through most typical corners, not a huge gain but not insignificant on small radii curves either.

Safety is the big issue, it will ot be as safe as a conventional car but safer than a big bike. Itt hink it might be possible to met the letter of the safety belt laws ( in the UK anway) but impact proterction is poor.

So there it is offered for comment and critique ( hopefully). if anything is unclear I will try to expalin or add extra sketches.

[Canuck]

As I lie here with aching knees, looking at the drawing I think only one thing - I'd happily take the 100kg in exchange for more comfort. That looks like a more uncomfortable position than 6-foot me on a small race bike. I'm mind of a fan of the car fitting the driver, not the driver being jammed and crammed into some technical solution.

[cheapracer]

Cheapy do you want it emailed?


Safety is the big issue, it will ot be as safe as a conventional car but safer than a big bike. Itt hink it might be possible to met the letter of the safety belt laws

Thanks for your kind thought - I got a proxy working the last few days until it's blocked so I was able to download it just now. I had forgotten just how much time you can waste on Youtube so I will be glad when they block this proxy!

Will have a gander tomorrow but the immediate obvious safety issue is spinal compression if you use seatbelts, would be better with an airbag.

Then it needs to be a 3 wheeler to be a motorcycle for most countries for licencing considerations if no seatbelts - there is a law that you can have 2 rear wheels with a certain spacing in the UK that still makes it a 3 wheeler hence motorcycle, check it out. I know that because of a kit car that's sold in the UK in that 'narrow rear' 4 wheel guise but I can't remember it's name.

Peugeot had a 4 wheel concept car that may have fitted into that law come to think of it, it was before the CUP20 3 wheeler.

Found it and their Quad concept ...

http://www.conceptca...te-Concept.aspx

http://www.conceptca...rk-Concept.aspx

Edited by cheapracer, 26 June 2011 - 14:44.

[mariner]

I have thought about the kneeling postion a lot. it is used by all the sidecar racers and was first developed on BMW sidecar outfits many years ago. They race around the IoM TT course for one hour so the driving/riding postion can't be that bad.

http://www.iomtt.com...76-124c3f31b355

The design inlcudes a small seat mounted on a cross tube so as to provide support beyond just the knees.

In terms of seat belts a pure lap strap would not, I think create any dangers as it working at the body's CG and lap straps were accepted as Ok on cars for many years even if diagonals are safer. I envisage the central pyramid as being the anchor point for the shoulder straps and the driver sitting up for the legal test. On a conventional car a passenger can lean right forward if they wish with a diagonal belt and that is about the same as the kneeling postion.

Don't get me wrong my real logic is that plenty of people choose to ride a superbike which is more dangerous than this device with no belts etc. My point is purely to make it legal as a four wheeler without requiring the pasengers to be put to risk if they wear the belts. ( to put it bluntly they would have seperate lap and diagonal belts to do up and choose to leave off one or both as they felt happy with)

BTW to keep things simple it would be best if the brakes were foot operated along with the gearchange ( pure bike rocker) bu the throtle was twistgrip with hand clutch. so the contols are bike like .for simplicity and ease of use.

I do appreciate that a three wheeler can get round all these probelms but the track on a three wheeler will always be only half of the same size four wheeler and I don't see the stabilty trade off to save one wheel as a very good one.

The thing is intended as a sunny day toy not for regular commuting so ( I hope) the novelties would be fine for an hour between coffee stops. The idea is something that is very fast on a bike engine and does require helmet/leathers etc.to give a thrill ride as and when you feel like it.

[jatwarks]

So there it is offered for comment and critique ( hopefully). if anything is unclear I will try to expalin or add extra sketches.

Why not have the two sides of the chassis lean into the corners? The four wheels can stay upright like a car but allowing the seats and handlebars to lean would make the ride much more comfortable for the driver and passenger. The upright wheels will allow greater lateral grip.

Trouble is, your aim of reducing weight would be compromised by the extra complexity.

How about a four wheel version of Freddie Dixons leaning sidecar outfit, in which the passenger controlled the angle of lean through the corners?

[cheapracer]

I rikey ....

http://thekneeslider...pension-system/



In a much lowered, road orientated form of course.

On thing that worries me is high siding and how to prevent it, maybe dampers based around the tilt process.

Edited by cheapracer, 27 June 2011 - 14:07.

[Tony Matthews]

On thing that worries me is high siding and how to prevent it, maybe dampers based around the tilt process.

Just a thought...

[Kelpiecross]

[quote name='mariner' date='Jun 26 2011, 21:34' post='5129878']

Mariner- I also tend to think like you in that a bike-engined car need only weigh 300Kg or less.
But I don't think you need to go to extremes like your kneeling position - which I suspect would suit only ex-sidecar racers. (I get a near-fatal "hammy" cramp just thinking about it).
I have been building a small (64 inch wheelbase) 2-seat car for many (too many) years. It is now about 90% done (but still plenty of work left).
My general solution has the driver (and passenger) sitting in the normal semi-reclining sportscar-type position but basically occupying the entire wheelbase. To save weight etc. the car is mainly a one-piece fibreglass "tub" incorporating chassis and body. The bike engine sits transversely ahead of and driving the front wheels. Before you get horrified by this - I grew up driving Morris Minis for many years and I am happiest with front wheel drive handling.
The original idea was to make (and sell) something like Cheapy's "Cheapracer" concept.
If you are interested I will attempt to work out how to post sketches and photos etc. of the car.

Edited by Kelpiecross, 13 July 2011 - 03:30.

[Johan Lekas]

As a reference the (single seater) 1100 cc hillclimber PCD Saxon built in 2001 had a wet weight of 208kg. http://www.sbdev.co....peedofLight.htm

[Kelpiecross]

As a reference the (single seater) 1100 cc hillclimber PCD Saxon built in 2001 had a wet weight of 208kg. http://www.sbdev.co....peedofLight.htm

Amazingly light. It is hard to imagine a motorcycle-engined car that essentially weighs the same as the motorcycle the engine came out of.

[Powersteer]

Nothing wrong with weight and four wheels, I mean, just buy a go-kart, add a few trellis stainless steel structure, increase wheelbase slightly and then put a big block neanderthal like 572 cubic inches vee eight that has a carburetor that can take four tennis balls at once on full throttle. Power to weight ratio would be 'Veyron' beating while the vee eights torque would not require muliple gear ratios in pure go-kart fashion haha! I mean, kneel car is fine and all, on a flat surface but when the going gets tough I might look slightly perverse going up and down while kneeling.

[mariner]

Powersteer, they were called CanAm cars!

[Powersteer]

To be honest, your kneel car would be fun in a jet ski to speed boat kind of way.

[mariner]

OK guys I guess nobody really liked by kneeler car idea as it sounds too uncomfortable/unsafe.

However I still think the secret is a small plan area car with some ultimate lateral G sacrificed to enable it to be narrower/lighter/more agile. I really don't think you can use 1.2G plus very often on public roads unless you live in an area with wide open views and not too much traffic. They exist but usually not where people with disposable income live in large quantities.

Anyway while I was at the Goodwood FoS I met a guy from "Phil Irving Vincent/HRD" in Australia. He described the big V twin bike they used to win a competiton at Daytona in 2008.

http://www.irvingvincent.com/bikes

Phil Irving, of course , helped design the 1966 championship winning Repco engine for Jack Brabham and the guy I talked to was an apprentice at Repco at that time.

What interested me is that they claim 165 bhp from a two valve V twin of 1.6 litres but at only 6,500 rpm. That equates to a 384 cubic ins. V-8 doing 660 bhp at 6,500 rpm which is pretty impressive.

So I am thinking of "building" a car with conventional seats but one of these V - twins at the rear just behind the rear axle centre line driving a VW type box. With only 6,500 rpm the gearing would be easier/lighter than a 4 cylinder Jap screamer. That would mean no space needed inside the wheelbase for the engine/trans and "my" ultra short wheelbase would still be viable with a very simple tubular backbone.

Does anybody know if these 165 bhp V twins really put out that much power at such low rpm and how much do they weigh without a gearbox?

[cheapracer]

Does anybody know if these 165 bhp V twins really put out that much power at such low rpm and how much do they weigh without a gearbox?

Why on earth would you use an obscure, unproven and very expensive engine when there are so many other choices?

Honda VTR 1000, Ducati 1200 and any of the 1600 to 1800 Japanese V Twins without mentioning all the Harley tryhards like S&S would be well ahead on my list before that antiquated back to the future abortion.

And that's if you want a twin, for 4's a Honda ST1100/1300 would probably be your ideal choice or Yam FJ1300 if you want air cooled and 20 years of fun rather than 20 minutes.

I'm sure I could send you a couple of those 50+hp 600 singles that have reverse included for a fraction the price of that "thing".

[mariner]

Cheapy , I don't know much about big bike V- twins!!

The V twin idea appeals because you could keep the C of G real close to the rear axle line. Revs below 10K helps with gearing so another score to a big twin.

I know enough to not think of a Harley due to low output but I didn't realise that the Japanese big twins over 1200cc. Are any of them water cooled by any chance ( and give 160 bhp)?

[Canuck]

http://www.irvingvincent.com/bikes

Phil Irving, of course , helped design the 1966 championship winning Repco engine for Jack Brabham and the guy I talked to was an apprentice at Repco at that time.

What interested me is that they claim 165 bhp from a two valve V twin of 1.6 litres but at only 6,500 rpm. That equates to a 384 cubic ins. V-8 doing 660 bhp at 6,500 rpm which is pretty impressive.
<snip>
Does anybody know if these 165 bhp V twins really put out that much power at such low rpm and how much do they weigh without a gearbox?

NASCAR BMEP level so clearly not impossible but high-maintenance comes to mind. Strangely, most of the data I have is for 4 cylinder motorcycles however the notes I have on the litre-class Ducati twins suggest 140-ish hp/l @ 9,750 rpm on the showroom floor. There's not a lot of 100" v-twin engines making those kind of naturally-aspirated numbers outside of captivity that I'm aware of. In fact, I'm not aware of any "sport" v-twins in the 1.6L range. The 1.6l realm is dominated by the Harley/Victory/Indian/other-large-cruiser market, not sport bikes. 99% of that market is tuned around the big-block v-8 feel with gobs and gobs of low-end torque, pushrods and breathing that falls on it's face at 5000 rpm.

Buy a 160hp (claimed) Ducati 1098S v-twin and build around that - there's bound to be pristine no-milage examples in some fancy-pants garages (or bent ones at the insurance auctions).

[cheapracer]

Cheapy , I don't know much about big bike V- twins!!

Clear your mind and go buy a junked TL1000R Suzuki, it wins hands down for power/cost/weight/lifespan for your project (Honda VTR1000 a close 2nd). Forget it's got 'only' 135hp (pipes and jetting = 150hp), they weigh nothing and haul ass.

As Cunuck says, the big twins have no rev range as well as bad vibes.

http://en.wikipedia..../Suzuki_TL1000R

[Kelpiecross]

[quote name='mariner' date='Jul 17 2011, 01:59' post='5173706']
OK guys I guess nobody really liked by kneeler car idea as it sounds too uncomfortable/unsafe.

Mariner - to get back to your overall car design and not just the engine.
If you are still thinking about a small car with the wheelbase basically set by the length needed by the driver (and maybe passenger) - this would be a WB somewhere in the 60 inch range. I don't think you can really have an engine behind the rear axle line no matter how light it is. This is just a personal view on handling preferences but with a bum-heavy car and a very short WB the handling would be tricky.

If you don't like the FWD option (as I prefer) you could have the motorbike engine/gearbox next to the driver where the passenger would normally be. This would make the car nicely balanced but only a single-seater.

If you were going to use the behind-the-rear-axle layout with the VW transaxle you might as well use the VW engine - which is notably light for its capacity and potential (when modified) power.

My basic idea for a very small bike-engined car would be something akin to a much-modernised, smaller and lighter redesigned Berkeley of the late 1950s.

The Berkeley weighed about 320Kg.

Edited by Kelpiecross, 19 July 2011 - 04:36.

[cheapracer]

mariner, of interest ...

http://www.gizmag.com/go/8234/

[mariner]

Thanks, Cheapy.

How is your car coming along please?

[Tony Matthews]

Ah, gizmag. I keep quietly pushing this, well worth signing up for, several updates a month covering every aspect of science, engineering... cool.

[J. Edlund]

Making the car a bit longer isn't going to cost much in terms of weight, so I think this is a solution to a non existing problem. Using regular car wheels, brakes and uprights on the other hand can easily add more than 100 kg to the weight of the car.

I also think that it is best to place the driver, the fuel tank and the engine after each other in the center of the car, this gives a good weight distribution and a low moment of inertia.

[Kelpiecross]

I also think that it is best to place the driver, the fuel tank and the engine after each other in the center of the car, this gives a good weight distribution and a low moment of inertia.

I don't doubt that this is perfectly true for a lot of competition-type cars. However in the real world with with less-than-ideal road conditions and maybe non-Webber skill levels a car with the weight biased towards the front and a not-so-low momemt of inertia is a lot more controllable and less frightening.

It is notable that Rowan Atkinson, who was very fast on Top Gear (so is clearly a very good driver) still managed to crash his Mclaren. I would imagine that the Mclaren with its low polar moment, excessive power etc. would be a real bastard of a thing on a greasy wet road.

[cheapracer]

with its low polar moment,

Yup, not for average drivers in variable conditions.

My car will have a very low polar moment, wasn't a primary design factor but ended up that way through clever packaging and I actually lengthened the wheelbase a bit to slow things down (96") but can go longer if need be.

[J. Edlund]

I don't doubt that this is perfectly true for a lot of competition-type cars. However in the real world with with less-than-ideal road conditions and maybe non-Webber skill levels a car with the weight biased towards the front and a not-so-low momemt of inertia is a lot more controllable and less frightening.

It is notable that Rowan Atkinson, who was very fast on Top Gear (so is clearly a very good driver) still managed to crash his Mclaren. I would imagine that the Mclaren with its low polar moment, excessive power etc. would be a real bastard of a thing on a greasy wet road.

Any powerful rear wheel driven car tends to be difficult to drive if the road is really slippery. I don't think you can single out one particular feature of the car as the reason behind an accident like this.

Also, being a good driver at a racetrack doesn't necessarily protect you from roadcar accidents.

[J. Edlund]

Yup, not for average drivers in variable conditions.

My car will have a very low polar moment, wasn't a primary design factor but ended up that way through clever packaging and I actually lengthened the wheelbase a bit to slow things down (96") but can go longer if need be.

Longer wheelbase means that the car will more difficult to control if it oversteers.

[cheapracer]

Longer wheelbase means that the car will more difficult to control if it oversteers.

There's a point where all the theory and math you can throw at it becomes totally irrelevant to what happens in the real world.

[Kelpiecross]

Longer wheelbase means that the car will more difficult to control if it oversteers.

This is something I do have disagree with. In my opinion (and experience) oversteer is more easily controlled in a long wheelbase car. Short wheelbase cars are more inclined to "snap" when the tail end breaks away.

[24gerrard]

It is wheelbase plus polar moment that dictates how easily a car will 'break away' and how easily this will be controlled.
It is only the starting point in design of course.

[Canuck]

I had the back end of my over-powered/nose-heavy shortbox pickup come around on me (while a passenger) at about 85mph. It happened on a dead-straight stretch of road in very slippery conditions (we were under the impression it was typical winter driving conditions but recent dips below -50C had turned things into a curling rink). It happened so quickly, and the length being short as it was, we were heading the right direction while facing the wrong one rather quickly. It continued it's rather obscene behaviour of swapping ends until we hit the left snowbank going backwards with the right rear tire hard enough it blew the tire, pivoted the truck around and once more slammed us into the snowbank blowing both front and rear tires on the left side. We were now pointing the right direction but still on the wrong side of the road and now with three flat tires in a -45C no-man's land, 2 hours from nowhere.

A long wheelbase gives you all kinds of warning and if you're not a half-wit, gives you all sorts of time to recover, at least i) in my winter-driving experience (which was 8 months of the year) and ii) in typical North American passenger vehicles.

[gruntguru]

It is wheelbase plus polar moment that dictates how easily a car will 'break away' and how easily this will be controlled.

For stability, control and steering response longer wheelbase and lower polar moment is the aim.

[24gerrard]

For stability, control and steering response longer wheelbase and lower polar moment is the aim.

I agree on stability but not on steering response.
Many loose surface vehicles are designed with a high polar moment to provoke break away with better vehicle control on the limit.
The break away is earlier but far more predictable.

This is why mid engined low polar moment sports cars are so unforgiveing on the loose or in the wet.

[cheapracer]

Bike'ish 4 wheeler here .....

http://www.google.co...A...ycle&f=true

Edited by cheapracer, 19 September 2011 - 06:53.

[MatsNorway]

Since whe are on the subject..

Thats one of the reasons why F1 cars go longer wheelbase. And thats why they are so nervous in a slide.

They got so much rotational grip that they overrun the reflexes or something. the older cars had less grip and shorter wheelbase. much easier to control in a slide... i think.

I want future F1 cars to be shorter in wheelbase so that we get better racing.

Edited by MatsNorway, 19 September 2011 - 07:41.

[cheapracer]

Thats one of the reasons why F1 cars go longer wheelbase. And thats why they are so nervous in a slide.

THE reason F1 cars are so long is aerodynamics - the bodywork has to be that long to avoid separation and smooth airflow to the rear wing. So I believe.

[JJW]

also packaging - by the time you get the drivers feet behind the front axle, put the fuel tank in the middle, pop and engine and gearbox behind, you have a wheelbase of x plus or minus say 50mm (and it is the latter that they play with for tuning)

wouldn't a fford with a bike engine be more or less 300 to 400kg dry?

[cheapracer]

Well mariner, I actually found a "kneeler car" ...

http://www.automotto...le-mark-iv4852/

[Fat Boy]

[Magoo]

[mariner]

Well mariner, I actually found a "kneeler car" ...

http://www.automotto...le-mark-iv4852/

Thank you cheapy, maybe I will keep thinking about it!

[Hoofhearted]

For those with sore knees, perhaps?


By weslake at 2010-09-15

[Tony Matthews]

There are times when a condom makes sense but that, I think, is unecessary.

[cheapracer]

For those with sore knees, perhaps?

Well solves the problem of lane splitting, just go under the suckers!