FFTS
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| posted on 5/2/10 at 08:04 PM |
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My my.. what an International melting pot of a thread is this hey 
Chris.
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Blue Devil
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| posted on 5/2/10 at 08:09 PM |
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funny all of us American pro-mid engine chaps are over here... 
(although i have had no disputes with the locostusa guys)
Mid Engine R1 build
http://www.locostusa.com/forums/viewtopic.php?f=36&t=4970&start=0
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andkilde
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| posted on 5/2/10 at 09:29 PM |
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My take on it is it's all in how you define "better". Faster around a track, better packaging, easier to source donor components,
better ride, better "handling", feel, looks, tradition? Pick your poison, Middies may well have won every F1 race since 1958, but I
daresay our cars will face slightly different conditions than your average F1 car.
Kurt has done a good job detailing the advantages of middies above but there are also weird local factors such as the registration laws in Ontario
which favour a seven (or any other repli-car) over a self designed scratch-built.
As I've just recently decided to get my finger out and actually get cracking on a car, I'm building pretty faithfully to the Haynes plans,
I don't want to innovate myself into a 5-year build
Cheers, Ted
[Edited on 5/2/10 by andkilde]
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Chet
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| posted on 7/2/10 at 07:07 PM |
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FYI -
The US LHD Fury Hayabusa's are really "mid engine" but Jeremy's new J15 has obvious benefits.
Chet
 
Rescued attachment JP-15..jpg
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Doug68
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| posted on 8/2/10 at 09:20 AM |
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If you confine yourself to "Best" meaning fastest lap times then its a tricky question to answer as so few classes have the rules to make
both viable options, as far as I can tell the Panoz LMP was the last serious attempt to build a front engined LMP car to the same rules as the mid
engined cars.
this car was not a great success, but reading what the designer had to say about it that cant really be blamed on the engine layout.
http://www.mulsannescorner.com/thorby.html
Interestingly he says: "A front-engined LMP has some advantages (e.g. inherent weight distribution, driver position)" Which is counter
intuative to what I would think, but I'm not the one being paid to design cars.
More on the car here:
http://www.mulsannescorner.com/panozlmp07.html
So in think the ultimate case the jury is still out for want of a properly funded front engine effort.
[Edited on 8/2/10 by Doug68]
Doug. 1TG
Sports Car Builders WA
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Sam_68
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| posted on 11/2/10 at 12:45 PM |
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quote:
Originally posted by Doug68
Interestingly he says: "A front-engined LMP has some advantages (e.g. inherent weight distribution, driver position)" Which is counter
intuative to what I would think, but I'm not the one being paid to design cars.
I'm second-guessing what he meant, of course, but the 'advantages' of things like weight distribution and driver position can depend
on the cars purpose.
For example, on an LMP car that is running long races (or for a road car, on topic...) stability and predictabilty can be more important than the last
10th of a second per lap.
A car with a frontal weight bias will tend (all other things being equal) to have more stability to crosswinds (CoG aheag of CoP...think dart)
Seating the driver further back (increasing the distance from the CoG to the driver's head) gives his inner ear more sensitivity to chassis yaw,
so a tired or fatigued LMP driver (or the less highly skilled driver of a road car) will be more consistent and less prone to mistakes.
The 'advantages' of a twitchy, low-polar-moment mid engine car on a short circuit race or hillclimb can suddenly become
'disadvantages' on the road or a 24 hour endurance race...
[Edited on 11/2/10 by Sam_68]
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Neville Jones
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| posted on 12/2/10 at 10:19 AM |
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Sam, now can you explain for my feeble brain, why all the top running cars at LeMans, the FIA GT's, and USA LM series, are the opposite
configuration to what you'd recommend?
Cheers,
Nev.
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Sam_68
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| posted on 12/2/10 at 12:34 PM |
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quote:
Originally posted by Neville Jones
Sam, now can you explain for my feeble brain, why all the top running cars at LeMans, the FIA GT's, and USA LM series, are the opposite
configuration to what you'd recommend?
Cheers,
Nev.
Because different designers weight the significance of different factors, erm... differently.
And I never said I'd recommend a front engine layout for an LMP car.
Like I said, I'm second guessing what the designer of the Panoz meant by his comments, but it is irrefutable that the driver feedback and
stability considerations are positives in favour of a front engine layout, clearly every other designer in recent years considers that they are
outweighed by the negatives of other considerations.
For what it's worth, I do slightly a favour front engined layot for road cars, but that's a different issue.
Car design is a complex compromise.
HTH
[Edited on 12/2/10 by Sam_68]
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Doug68
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| posted on 14/2/10 at 09:37 AM |
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quote:
Originally posted by Neville Jones
Sam, now can you explain for my feeble brain, why all the top running cars at LeMans, the FIA GT's, and USA LM series, are the opposite
configuration to what you'd recommend?
Cheers,
Nev.
I expect similar statements were made about mid engined cars before before they became the accepted norm.
After all there were plenty of front engine race cars after mid enigne was first done in 1923 so the benifits of mid-engine can't have been that
stupidly obvious at the time can it?
The answer to your question though is if you do somthing different and fail you're classed as an idiot, or at least people will point very
quickly to what you did differently as why you failed. Follow everyone else and fail then you just need more development.
Did the Panoz fail because it was front engined or because the engine wasn't up to it or for a lack of testing or funds?
No one out there has the balls - cash to find out do they?
Doug. 1TG
Sports Car Builders WA
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cheapracer
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| posted on 16/2/10 at 08:06 AM |
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I've built a lot of cars for a lot of years and its how you do it not where things are (wihin reason) and the old rule of the thumb "as
long as you get the major mass inbetween the wheels and low" still works because physics hasn't changed.
In huge favor of what we are refering to as mid engined, ie FWD unit behind the seats is mostly the exhaust - exhausts are the biggest pain in the ass
and very few people design them in early. obviously the whole unit with gearbox and driveshafts being very common and cheap make it a nice choice too.
In favor of 'front' mid engine (the engine behind the front axle but still up front) is things happening slowly and more drivers can stay
near the limit for a longer time which, yes, possibly are lower than a middy.
At the end of the day it still comes down to good tyres and springs and shocks to match the tyres and if you dont believe that go to a Historic race
meeting and see how fast 60's or 70's sedans go with their front engines and antique suspension layouts but with good tyres/shocks.
Weight distribution numbers such as 50/50 are nonsense and dont tell where the masses are, you could have 2 Chev V8's 1 meter out each end and
honestly tell me "I have 50/50" - but how does it handle? Ask Audi and their rally car with 50/50 but a huge 5 cylinder engine, hanging
mostly in front of the front axle, how they handle.
I am tired of reading/hearing F1 nonsense relating to road cars especially suspension ideas that are based on huge ground effects but find there way
to street cars/kit cars more and more - yeah right, good luck with that.
Kurt I didn't see that stuff, I find the Locost USA forum ok but then maybe saying people were using truck parts in their cars wouldn't
help lol!!
[Edited on 16/2/10 by cheapracer]
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cheapracer
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| posted on 16/2/10 at 08:18 AM |
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quote:
Originally posted by Doug68
[
Did the Panoz fail because it was front engined or because the engine wasn't up to it or for a lack of testing or funds?
No one out there has the balls - cash to find out do they?
They were a bit short of funds and i believe 2 things influenced the Front engine desision and they were gearbox at huge reduction in price and
diffuser size could be increased. theyw ere easier to drive according to the drivers and were reasonably successful but you cant beat the money that
was up against them.
It's coming....
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Neville Jones
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| posted on 16/2/10 at 10:55 AM |
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quote:
Originally posted by cheapracer
quote:
Originally posted by Doug68
[
Did the Panoz fail because it was front engined or because the engine wasn't up to it or for a lack of testing or funds?
No one out there has the balls - cash to find out do they?
They were a bit short of funds and i believe 2 things influenced the Front engine desision and they were gearbox at huge reduction in price and
diffuser size could be increased. theyw ere easier to drive according to the drivers and were reasonably successful but you cant beat the money that
was up against them.
Listers tried for a few years.
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kb58
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| posted on 16/2/10 at 04:09 PM |
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quote:
...Weight distribution numbers such as 50/50 are nonsense and dont tell where the masses are...
True, and something 50/50 believers leave out of their sermons is what happens when they bolt on different size tires on the rear, as many do. Sure,
the scales might say 50/50, but dynamically, out on-course, it'll behave very different.
quote:
Kurt I didn't see that stuff, I find the Locost USA forum ok but then maybe saying people were using truck parts in their cars wouldn't
help lol!!
Oh it's there. The irony is that it took place in their mid-engine sub-forum, where you'd expect a little more freedom of discussion.
[Edited on 2/16/10 by kb58]
Mid-engine Locost - http://www.midlana.com
And the book - http://www.lulu.com/shop/kurt-bilinski/midlana/paperback/product-21330662.html
Kimini - a tube-frame, carbon shell, Honda Prelude VTEC mid-engine Mini: http://www.kimini.com
And its book -
http://www.lulu.com/shop/kurt-bilinski/kimini-how-to-design-and-build-a-mid-engine-sports-car-from-scratch/paperback/product-4858803.html
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designer
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| posted on 17/2/10 at 10:26 AM |
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Overall mid-engine is better.
Generally lighter and better polar moments.
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cymtriks
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| posted on 10/3/10 at 12:35 AM |
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In most road applications a mid engine isn't there for the handling.
The real reason for their popularity is not handling but availability. The number of mass produced front engined RWD drivelines has shrunk to
virtually nothing over the last few decades. Anyone who wishes to design a middy to be sold in any significant numbers has to dip into the the parts
bins of front drive hatchbacks. They have no choice. That is all that's available.
All this stuff about how race cars all have mid engines is just missing the point. They are purpose designed to make use of the advantages of the
layout. They are not restricted to the limits of hatchback design.
So why does the origin of the engine matter so much? Because of modern car design, that's why. No transverse hatchback engine is ever designed
with mid mounting in mind. They are designed for crush zones and emissions. That normally forces a tall package to fit the stuff in around the block.
This raises the centre of gravity.
Now a low polar moment of inertia is a good thing but conversely a high centre of gravity is a bad thing. So using a modern transverse package as a
straight transplant is never going to give the full advantage of a mid engined layout.
However it is possible to design a modern front engined car with the engine set well back and fit it with a low sump to keep the centre of gravity
low.
However this restricts you to the parts bins of Mazda and BMW.
For anyone else a mid engine is forced on the designer, not because it is better because it may not be better at all with a higher CoG, but because
they have no choice.
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Doug68
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| posted on 10/3/10 at 04:08 AM |
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quote:
Originally posted by cymtriks
They are purpose designed to make use of the advantages of the layout.
So you're saying mid engine is better then.
Doug. 1TG
Sports Car Builders WA
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Ivan
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| posted on 10/3/10 at 07:08 AM |
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Cymtrics has raised a vital point about keeping the COG low and the problems with modern FWD drive engines where COG plays a secondary consideration
in design - so if you go transverse mid engine and handling is a priority of yours find the lightest all aluminium engine you can that provides the
power you need or go for a flat four longitudinal layout.
I think an inch downwards in COG will have a significant impact on handling.
If I recall the BT front engined cars angled the engines significantly, I presume largely for COG reasons and if your middy design allowed that it
might be worthwhile pursuing.
I guess the same could apply to front mid engined cars as well.
[Edited on 10/3/10 by Ivan]
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Doug68
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| posted on 10/3/10 at 09:16 AM |
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quote:
Originally posted by Ivan
Cymtrics has raised a vital point about keeping the COG low and the problems with modern FWD drive engines where COG plays a secondary consideration
in design
This arguement is good in theory, but then you need to explain the Lotus Elise.
Doug. 1TG
Sports Car Builders WA
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Ivan
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| posted on 10/3/10 at 09:24 AM |
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Don't really have to explain it because it is compromised compared to what it would be with a lower COG. 
It's only as good as it is because they knew what they where doing and designed for the compromises made.
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iank
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| posted on 10/3/10 at 10:07 AM |
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Indeed it's a very complex trade off. A transverse middy will (for the same number of seats) have a much shorter wheelbase than an inline
middy. A shorter wheelbase will tend (all other things being equal) to make the car more agile at the expense of high speed stability.
On angling the engine, the Onyx Mongoose had it's mid engined K series tilted over a very long way, to the level where they had to make some
modifications to the oil system to avoid it blowing out of the exhaust by the pint iirc (their description is long gone from their site sadly*).
* Just found it's been archived by the wayback machine for those that are interested.
http://web.archive.org/web/20080110065409/www.onyxsportscars.f9.co.uk/id20.htm
[Edited on 10/3/10 by iank]
--
Never argue with an idiot. They drag you down to their level, then beat you with experience.
Anonymous
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kb58
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| posted on 10/3/10 at 02:36 PM |
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I used a FWD Honda H22A1 in my last build, and am using a FWD Honda K24A2 in my latest build, both mounted transversely in a mid-engine arrangment
behind the seats.
In both cases, the bottom of the oil pan and transaxle limit how low it sits - no different than a front-engine setup. There is 4" ground
clearance below the pan and transmission, exactly what I wanted. So, while FWD engines may not be designed for mid-engine applications, that in itself
doesn't mean they won't work great. For me, the Honda K-series works very well.
Regarding shortening the sump, besides inducing oil supply issues, doing so doesn't allow the drivetrain to be lowered due to the transaxle case
hanging down just as far as the pan did. But since it can be set as low as the bottom chassis rails, there's no need to change anything.
So I don't see how a FWD setup in a mid-engine arrangment is any different from a CG point of view than a front-engine layout - at least for
modern FWD drivetrains. Perhaps you guys are refering to other FWD setups, maybe ones with the transaxle under the engine - that would certainly raise
the CG.
As was said, the transverse layout works great for shorter cars. In my mid-engine Mini it was a natural. For Midlana, a Sevenesque car, it keeps the
engine bay short, retaining some of the Seven look.
[Edited on 3/10/10 by kb58]
Mid-engine Locost - http://www.midlana.com
And the book - http://www.lulu.com/shop/kurt-bilinski/midlana/paperback/product-21330662.html
Kimini - a tube-frame, carbon shell, Honda Prelude VTEC mid-engine Mini: http://www.kimini.com
And its book -
http://www.lulu.com/shop/kurt-bilinski/kimini-how-to-design-and-build-a-mid-engine-sports-car-from-scratch/paperback/product-4858803.html
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Alan B
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| posted on 10/3/10 at 03:02 PM |
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quote:
Originally posted by Doug68
quote:
Originally posted by Ivan
Cymtrics has raised a vital point about keeping the COG low and the problems with modern FWD drive engines where COG plays a secondary consideration
in design
This arguement is good in theory, but then you need to explain the Lotus Elise.
Beat me to it Doug....I'd forgotten just how s**t the Elise was..........could it be better with lower CoG...sure, but we are taking road cars
and the Elise aint too shabby......
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Doug68
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| posted on 11/3/10 at 04:28 AM |
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Referring to Kurts post...
Looking at the picture below, it the flywheel size thats setting where the bottom of the engine is (just like a front engined car).
And clearly the motor is not on top of the transmission.
Doug. 1TG
Sports Car Builders WA
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iank
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| posted on 11/3/10 at 07:51 AM |
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I think the idea that transverse fitments have a higher cog compared to inline comes from the typical engines that are used.
i.e. 4 pot engine has a higher cog than a V8 more so for DOHC 4 pots compared to OHV V8s.
--
Never argue with an idiot. They drag you down to their level, then beat you with experience.
Anonymous
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kb58
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| posted on 11/3/10 at 02:22 PM |
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quote:
Originally posted by Doug68
Looking at the picture below, it the flywheel size thats setting where the bottom of the engine is (just like a front engined car). And clearly the
motor is not on top of the transmission.
Because a front-engine drivetrain is uncoupled from the rear axle, it can be set at any height wanted.
OTOH, a FWD drivetrain has to be at or about the same height as the wheel hub so that the axles line up. I didn't bring this up because it tends
to end up about where we want it anyway.
For example, my Honda K24's sump and transmission hang down about 7" below axle centerline. A 24" diameter tire has a 12"
radius, so with the transmission axle ports lined up with it, there's 12" - 7" = 5" ground clearance. We can get away with
shifting the drivetrain some, so I dropped it an additional inch, resulting in the final ground clearance of 4". And unlike a Locost, it's
not hanging its private parts down below the frame rails asking to be removed...
I have a big spreadsheet with nearly every component on it, with X,Y,Z location and weight. With total car and driver weight of about 1600 lbs,
raising or lowering the drivetrain 1" moves the CG of the entire car 0.3", a decent amount.
Mid-engine Locost - http://www.midlana.com
And the book - http://www.lulu.com/shop/kurt-bilinski/midlana/paperback/product-21330662.html
Kimini - a tube-frame, carbon shell, Honda Prelude VTEC mid-engine Mini: http://www.kimini.com
And its book -
http://www.lulu.com/shop/kurt-bilinski/kimini-how-to-design-and-build-a-mid-engine-sports-car-from-scratch/paperback/product-4858803.html
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