Julian B
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 posted on 15/5/03 at 07:45 AM |
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0X7
Hi all
I have been trying to locate some info on a mid engine car built by a guy called John Oxborrow of Sussex i believe. He designed and built a car called
a 0x7 based on a formula ford track racer. The only info i have managed to find is a report on it............
LINK.........here..........
If any one has any info on this car or its builder i would be very grateful, as trawling tinternet has produced nout.
Here is a picture of said car.
Cheers all
Julian Brewer
Cumbria UK
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ceebmoj
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| posted on 15/5/03 at 10:32 AM |
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looks intresting I have been thinking about something simaler but bike engined. I will finish the low cost first thow
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Mark H
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| posted on 15/5/03 at 12:18 PM |
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Look a bit like a "push me pull you" locost. Reverse has got 5 gears too?
Mark Harrison and
Q986 KCP back from the dead...
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kb58
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| posted on 15/5/03 at 04:35 PM |
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Well I guess as long as you can keep the track to wheelbase ratio from being too nuts, it should work out. It just makes construction a little bit
more difficult because there are soooo many nice FWD drivetrains out there compared to the dwindling supply of in-line units. Why not use a FWD unit
for space and availability reasons? It works out really nice especially if you use the whole thing, engine, tranny, axles, hubs, and brakes.
Practically an all-in-one solution. But, to each his own...
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Julian B
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| posted on 15/5/03 at 07:22 PM |
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Well
I know that the easy option is transverse engine and its sorely tempting but i would like to try and keep it as pure as possible. The majority of
transverse "mid engine cars" seem to me to be rear engine cars. First one to say Porsche wins a prize... The only reason to go mid engine
inline is to try and improve on weight distribution and also to try and keep the cg and roll centre as low as possible. The biggest problem as you
mention is the lack of gearboxes with the Renault un1 going for £250 second hand if you can get one! That alone could put an end to the mid engine
low-cost idea.
I still think its worth a bit more time and effort investigating though.
Thanks for the input so far
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Alan B
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| posted on 15/5/03 at 09:01 PM |
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Strongly disagree with your definitions...most transverse engined middys are MID engined...
The definition of mid engined is engine behind the driver but AHEAD of the rear wheels.
Rear is engine is BEHIND the rear wheels
Front is the engine in FRONT of the driver.
I know some front engined cars are closer to 50/50 WD but they are still front engined....I know you didn't mention this but the front/mid
bullshit terminology drives me crazy...
Mid engined is purely a placement format NOT a weight distribution claim..
And anyway.....who says 50/50 is the optimum?
Not getting at you Julian BTW, just a general rant....
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Julian B
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| posted on 15/5/03 at 09:34 PM |
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Hi Alan
Your reply is just what i was after as i don’t claim to understand what the advantages of mid engine inline are (if any) over mid engine transverse.
Or in line front engine over rear engine etc. I thought it was to do with trying to set-up an optimal weight distribution of 50/50 between the front
and rear wheels so each tyre could be loaded up to its optimum during cornering. Also i thought it was to do with the front to rear tort ional loading
on the chassis, but all of this i am still unsure of. A little learning is a dangerous thing!
I’m still very dangerous but trying hard to improve, sorry if my ignorance disturbs…
Cheers
Julian B
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Alan B
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| posted on 15/5/03 at 09:50 PM |
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No problem...as I say not a dig at you...
The main thing is many people say 50/50 when IMO a slight rearward bias may be better...say 40/60
The people who do know for sure probably have good jobs at McClaren and Ferrari I guess...
On the general topic of trans v inline I think it's swings and rounabouts...advantages to both methods.
Bottom line, whatever works for you and meets your requirements is the right way.....one of many right ways...
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kb58
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| posted on 16/5/03 at 05:17 AM |
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Regarding the advantages of 50/50 weight distribution, it's all true... But, if you put larger tires at the rear, now what? It makes up for
having more weight at the back. So the permutations on how to build a car are about, oh, limitless. My recommendation is to do something within your
ability, and get on with it. If someone says, "I would have done different," tell them, well, when they build THEIR car, they can!
Back to wiring my car... I had no idea how silly a turn signal switch is! Now I know how they get two filiment bulbs at the rear to do three things,
stop, flash, and just be tail lights. Grrrr, it's nuts I tell you.
Hey Allen, are those tail lights you got from Walmart two filament? One or two bulbs?
[Edited on 16/5/03 by kb58]
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Scouse Monkey
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| posted on 16/5/03 at 08:23 AM |
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Just take alook at the Elise, around 40/60 split (I have seen some values of 38/62). Planning on going to go have a real good look at one soon but
don't they use a transverse K-series with their own design tranny?
Anyone know where the Elise fuel tank sits? I want to get it as close to the CofG as possible to reduce weight distribution change between full and
empty (just like planes do).
Andy
[Edited on 16/5/03 by Scouse Monkey]
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Alan B
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| posted on 16/5/03 at 11:29 AM |
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KB - The lights have single bulbs with dual filaments....I'm 99% certain.....I'll let you know if not.
They have two wires... rear light, plus turn/brake light, with ground at the mounting hole
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Spyderman
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| posted on 16/5/03 at 12:47 PM |
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This may help or confuse the issue further.
50/50 weight distribution is only good when traveling in a straight line on an even surface.
The first corner you come to you no longer have 50/50 as the front takes a larger arc round the bend.
The same applies when descending or climbing (or accelerating/decelerating). The weight is no longer evenly distributed, so you are no longer getting
maximum traction or loading on all wheels.
It seems that the optimum is around 40/60 as Alan states. This is due mainly to ,
1, the need for maximum traction under varying conditions (cornering, accelerating, etc)
2, keeping largest areas of mass (ie; engine and box) away from front of vehicle due to larger arc when cornering.
3, keeping weight transfer to a controlable minimum.
My explanations for the above are;
1, Weight over driven wheels gives maximum traction when accelerating. Tyres are not steering so are not sharing a task. Forces going into wheels are
in a more controlled form.
2, When cornering the rear axle is not steering, so is taking the shortest radius. Thus is traveling slightly slower than the front axle. As compared
for comparison a front engined car, the front engined car needs to accelerate the mass more to acheive the same speed through a bend. A good analogy
is the Balerina doing a piroet. When she spins if she brings her limbs in tight she will spin faster than when extending her arms outward. More energy
is needed to to spin the balerina at the same higher speed if she has extended limbs.
3, Weight transfer is very crucial and also very dangerous. You need to minimise transfer of weight as much as possible.
As stated above you need as much weight as possible over the driven wheels in order to maximise acceleration. Just look at dragsters to see this.
However when braking or cornering having all the weight over the rear wheels on rear drive (or front wheels on front drive) can be disasterous as car
will either spin out (or plough straight on with front drive). The further out from the centre the weight is centred will increase the tendency to
transfer that weight when braking or cornering.
So overall a 50/50 weight bias is perfect for straight line stability and mimimising weight transfer when braking, but a slightly rearward weight bias
is better all round.
Hope this doesn't confuse too much!
If you can understand it then maybe you can explain it to me!
Terry
bound to start of some controversy!
Spyderman
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Alan B
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| posted on 16/5/03 at 01:39 PM |
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All seems to make sense Terry...but as you say this one will run and run..
As KB says (paraphrasing)
If you disagree, then do it differently on your own car...
We can argue theory all day, but results count....
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kb58
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| posted on 16/5/03 at 02:16 PM |
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quote:
Originally posted by Spyderman
... So overall a 50/50 weight bias is perfect for ... mimimising weight transfer when braking...Terry
I agree with everything except this part. Weight transfer happens no matter where the weight is. CG *height* is more important then where it is
front to rear. As weight transfer occurs during deceleration, weight comes off the rear tires onto the front. Say you have 40/60 static weight
split; during braking, the dynamic weight distribution is now something like 60/40 front to rear. If the car was 50/50 to start with, it would be
about 70/30. That's one reason Porsches have such good braking, the engine is "holding down" the back end of the car, allowing more
rear brake bias, which allows the rear tires to contribute far more to the braking effort.
[Edited on 16/5/03 by kb58]
[Edited on 16/5/03 by kb58]
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TheGecko
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| posted on 16/5/03 at 02:50 PM |
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quote:
Originally posted by Julian B
The majority of transverse "mid engine cars" seem to me to be rear engine cars. First one to say Porsche wins a prize
Julian,
I may be mis-reading this but are you trying to say above that Porsche's have a transverse engine? I don't believe there's ever
been a transverse engined Porsche - certainly not a road-going one.
As Alan and others have stated, transverse FWD powerplants almost all sit in front of the axle line. In a mid-engined arrangement they can make for
very compact packaging.
On the original topic (the OX7) I have an article (not the same one mentioned above) from "Which Kit" or "Kit Car
International" somewhere here in the piling system. If I can find it easily I'm happy to scan it for you. It's late now -
I'll look tomorrow.
Dominic
[Edited on 16/5/2003 by TheGecko]
[Edited on 16/5/2003 by TheGecko]
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Julian B
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| posted on 16/5/03 at 04:37 PM |
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Hi Dominic
Thanks for the reply and if you manage to find out anything about the OX7 i would be grateful.
On the Porsche bit, well i just haven't got a clue what im on about really, i thought that the engine was slung out over the rear axle that’s
all , as in the vw beetle but i guess they have moved on a bit since then.
Cheers again
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Scouse Monkey
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| posted on 16/5/03 at 06:07 PM |
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Take a look here, he has some scans of articles about the OX7:
http://locost7.info/mirror/other.php
Hope this helps
Andy
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Spyderman
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| posted on 16/5/03 at 09:51 PM |
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quote:
Originally posted by kb58
quote:
Originally posted by Spyderman
... So overall a 50/50 weight bias is perfect for ... mimimising weight transfer when braking...Terry
I agree with everything except this part. Weight transfer happens no matter where the weight is. CG *height* is more important then where it is
front to rear. As weight transfer occurs during deceleration, weight comes off the rear tires onto the front. Say you have 40/60 static weight
split; during braking, the dynamic weight distribution is now something like 60/40 front to rear. If the car was 50/50 to start with, it would be
about 70/30. That's one reason Porsches have such good braking, the engine is "holding down" the back end of the car, allowing more
rear brake bias, which allows the rear tires to contribute far more to the braking effort.
[Edited on 16/5/03 by kb58]
[Edited on 16/5/03 by kb58]
I'd agree with you entirely, but I was thinking about more varied conditions, like braking whilst cornering.
And why does a rear engined Porsche have less weight transfer (implied) when braking if it happens equally to all vehicles. The rear wheels of a
Porsche do a larger portion of the braking simply because there is a larger portion of the weight over them and it can safely accomodate much larger
tyres.
I never ventured into CG height as it would only have made it more boring and long winded.
All things being equal with CG height, a car with engine at either end will suffer more catastophic weight transfer than one with engine centalised
betwen axles. Weight transfer goes in more than one direction.
Good point though.
Terry
Spyderman
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TheGecko
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| posted on 17/5/03 at 12:35 AM |
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quote:
Thanks for the reply and if you manage to find out anything about the OX7 i would be grateful.
I've recently unpacked all of my Which Kit etc magazines (they were still in boxes from moving house 12 months ago). I'll go through them
this weekend and find the article.
quote:
On the Porsche bit, well i just haven't got a clue what im on about really, i thought that the engine was slung out over the rear axle
that’s all , as in the vw beetle but i guess they have moved on a bit since then.
OK, I suspect that you're confusing the usual meaning of transverse here. It just means that the engine's crankshaft is in line with the
axles rather than with the centreline of the car as in an inline arrangement.
All of the flat-4 and flat-6 rear engined Porsches have an inline engine mounted behind the rear axle line. Most FWD cars have a transverse engine
mounted (mostly) forward of the front axle line. If you shift one of those powerplants to the back it is in front of the rear axle line -
mid-engined.
Hope this is clearer,
Dominic
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kb58
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| posted on 17/5/03 at 03:49 PM |
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quote:
And why does a rear engined Porsche have less weight transfer (implied) when braking if it happens equally to all vehicles.
You're right, weight transfer occurs on any car, rear engine or not, but think of it this way. The Porsche starts out with a static weight
distribution of, say, 30/70 toward the rear. As the car approaches a corner, the distribution is still the same, 30/70, because the car is neither
accelerating nor decelerating. Now the driver applies the brakes and the weight distribution shifts from the static 30/70 to an actual value of
something like 60/40. See how that happened? The weight shifted forward just like always, but since it had an initial rear "offset," it
works out that the tires end up more evenly loaded than if it had started out at 50/50. In the case of an initial 50/50 split, it would have gone to
perhaps 80/20, resulting in less total braking ability.
The situation where a static 50/50 works well is only in steady-state cornering, with no acceleration nor deceleration. Keep in mind though that
track cars are always accelerating or decelerating, spending very little time at that "balance point." Of course that's where tire
size mucks up our simple theory. That is, if the rear tires are larger, then the rears can stick just as well even though they have less then 50%
weight on them.
It goes on and on. If you get hung up on this stuff, you risk my dreaded "analysis paralysis," where you're too afraid to decide
anything for fear of it being all wrong. Just read lots of stuff and get going. I say this from personal experience...
[Edited on 17/5/03 by kb58]
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TheGecko
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| posted on 18/5/03 at 11:43 AM |
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OK Julian,
I found the article in question (Which Kit June 96) and have scanned all 5 pages. ZIPped up, they total about 1.5Mb - I've put the zip file up
at this address.
Let me know if there's any problems reading them.
Dominic
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Julian B
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| posted on 19/5/03 at 07:34 AM |
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Thanks for all the info guys its all very interesting. With reference to the Porsche and its weight transfer, i absolutely agree that under breaking
the weight transfer comes back towards the optimum 50/50 split ( assuming equal tyre sizes) but ...but I thought the idea of a 50/50 split was to load
up the tyre to its optimum when cornering. During cornering the car shouldn’t be in a state of breaking. It may be in a state of deceleration or
acceleration and a car with a 30/70split would be very interesting when accelerating out of a corner... What are the front wheels doing?
This is all very interesting thanks again guys, and thanks for the 0X7 info its just what I was after
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MrFluffy
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 posted on 24/5/03 at 08:55 PM |
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un1
Is this the bit where I pop up and say "£250 for a un1, I want the whole bloody renault turbo for that much!"..
Been quiet here, feeling the pull of the dark side (my turbo motorbike)
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