Barker
|
 posted on 10/4/02 at 12:02 PM |
|
|
Chasis - Mid Engine
I am starting to build a mid engine rear wheel drive Locost with a Citreon AX GT donor.
Has anyone else done a mid engine machine?
I think gear linkage may be a problem.
|
|
|
|
|
interestedparty
|
| posted on 10/4/02 at 01:59 PM |
|
|
There is a guy in the states who has done it but he used MR2 as donor so not so many problems, especially as he could use the MR2 cable linkage. I
will post the URL if I can find it later.
I've often thought about doing the mid engined thing, using front wheel drive power unit is obvious way but as you say linkage can be a big
problem.
Usually the linkage enters the gearbox at the rear, and normally requires fore and aft motion, and twisting motion. I believe most cars have detent
mechanisms (reverse avoidance!) in the linkage, not in the gearbox, so two cables will do it. I would be tempted to use an auto box but most people
prefer manual. Also a problem with the handbrake, there might be a rear caliper in the Citroen range that would fit and provide necessary mechanical
handbrake actuation.
I think some makers have used the equivalent of a steering trackrod with the inner anchored to the chassis to prevent unwanted rear wheel steering,
alternatively you could use Sierra IRS conversion stuff from Lolocost or MK and get special driveshafts made with Citroen inboard and Ford outboard
cvs.
Like I said, I've been thinking about this myself
John
As some day it may happen that a victim must be found,
I've got a little list-- I've got a little list
Of society offenders who might well be underground,
And who never would be missed-- who never would be missed!
|
|
|
phil
|
| posted on 10/4/02 at 09:15 PM |
|
|
just a thought on the handbrake!
You could try a BX front caliper as they have the h/brake mechanism built in to them,as the h/brake works on the front wheels.
hope it helps PHIL...
|
|
|
Alan B
|
| posted on 15/5/02 at 05:47 PM |
|
|
quote:
There is a guy in the states who has done it but he used MR2 as donor so not so many problems, especially as he could use the MR2 cable linkage
Hmmm...could be me unless there is someone else doing it 
check out http://www.desicodesign.com/meerkat/
Yes, you are right, already being mid-engined, the MR2 does make a good donor. However, after seeing the cable gearchange it is easy to see how it
could be used in other applications.
Alan B
|
|
|
philgregson
|
| posted on 5/8/02 at 08:21 PM |
|
|
Is creating a 'mid engined set up with a transverse front wheel drive unit a good idea?
I woud have thought that putting the weight of the engine directly over the axle in that manner would be rear engined not mid and would have
considerably worse balance than the traditional locost design where the engine sits a long way back from the front axle.
If a mid engined approach was required would it not be better to use a longitudinal engine and a transaxle such as that used in the 2l & 2.5l renault
21s & 25s (of which there are hundreds available very cheap and in my experience the 2l at least is a lovely engine). This locates the engine forward
of the back axle and will give far better balance than a transverse engine.
|
|
|
johnston
|
| posted on 5/8/02 at 09:01 PM |
|
|
well technically if u look at most fwd cars the axle line is actually be hind the engine the drive shaft is usually behind the block
thats one of the reasons why the bigger touring cars tilt the engine back putting the weight of the engine closer to the axle line.
another thing to look at is a scooby doo g/box its longnatudinal and apparently the centre diff int the 4wd box can be welded to give u the lsd
the audi gear box is also some simalir i.e longnatudinal but fwd
and i no my spellin is shit
|
|
|
philgregson
|
| posted on 5/8/02 at 09:14 PM |
|
|
Ok you have a point about the axle location in a transverse engine but we are still talking a big diference in in engine c of g from the axle with a
normal locost location of longitudinal set back from it's axle compared with the transverse set up.
|
|
|
johnston
|
| posted on 5/8/02 at 09:24 PM |
|
|
used to be a nova on the ni rally championshipn had the 16v in the bac it went well enough ok cog and stuff changes but think of most of the sports
prototypes, ferraris lambo's and porsche's oh and the metro 6r4 ok it was 4wd but still rear engined, ford gt40, lancia stratos (prob the best
lookin italian car next too the lambo muira) ford rs200, 205t16 if u want me go on i'll get me grand turismo 2 out
|
|
|
johnston
|
| posted on 5/8/02 at 09:24 PM |
|
|
used to be a nova on the ni rally championshipn had the 16v in the bac it went well enough ok cog and stuff changes but think of most of the sports
prototypes, ferraris lambo's and porsche's oh and the metro 6r4 ok it was 4wd but still rear engined, ford gt40, lancia stratos (prob the best
lookin italian car next too the lambo muira) ford rs200, 205t16 if u want me go on i'll get me grand turismo 2 out
|
|
|
johnston
|
| posted on 5/8/02 at 09:25 PM |
|
|
used to be a nova on the ni rally championshipn had the 16v in the bac it went well enough ok cog and stuff changes but think of most of the sports
prototypes, ferraris lambo's and porsche's oh and the metro 6r4 ok it was 4wd but still rear engined, ford gt40, lancia stratos (prob the best
lookin italian car next too the lambo muira) ford rs200, 205t16 if u want me go on i'll get me grand turismo 2 out
|
|
|
interestedparty
|
| posted on 5/8/02 at 09:29 PM |
|
|
I'm contemplating a longitudinal arrangement with Renault box myself, but if the rest of the engineering, chassis design etc is up to scratch then it
really isn't a problem where the engine is put, Porsche have been putting theirs in the wrong place for years!
Also, using a transverse unit makes huge economic sense. Sportscar design has always relied on the components available from makers off more
mainstream cars.
John
As some day it may happen that a victim must be found,
I've got a little list-- I've got a little list
Of society offenders who might well be underground,
And who never would be missed-- who never would be missed!
|
|
|
interestedparty
|
| posted on 5/8/02 at 09:33 PM |
|
|
I'm contemplating a longitudinal arrangement with Renault box myself, but if the rest of the engineering, chassis design etc is up to scratch then it
really isn't a problem where the engine is put, Porsche have been putting theirs in the wrong place for years!
Also, using a transverse unit makes huge economic sense. Sportscar design has always relied on the components available from makers off more
mainstream cars.
John
As some day it may happen that a victim must be found,
I've got a little list-- I've got a little list
Of society offenders who might well be underground,
And who never would be missed-- who never would be missed!
|
|
|
johnston
|
| posted on 5/8/02 at 09:43 PM |
|
|
dont no y thatr message has been posted 3 times but sorry anyway!!!!!!!!!!!!!! 
|
|
|
philgregson
|
| posted on 5/8/02 at 09:47 PM |
|
|
Ok I accept all the points and of course it can be done and done well but my point is why?
The standard locost arrangement is very well balanced, simple, easy to cool and we certainly do not have the same aerodynamic restraints as all the
very low nosed performanmce cars that follow this lay out.
Also speaking personally I like the idea of a large lump of engine between me and anything I might hit.
|
|
|
johnston
|
| posted on 5/8/02 at 09:57 PM |
|
|
well why not at the end of the day no 2 locosts are the same and everything is down to personall preferance thats why im makin the wheelbase longer on
mine too many scary moments in short wheel base rwd drive cars
|
|
|
philgregson
|
| posted on 5/8/02 at 10:02 PM |
|
|
Well you got me there!
|
|
|
Alan B
|
| posted on 5/8/02 at 10:02 PM |
|
|
quote:
Is creating a 'mid engined set up with a transverse front wheel drive unit a good idea?
I'm sure Lotus (Elise etc.) and Toyota (MR2) would say so.
quote:
I woud have thought that putting the weight of the engine directly over the axle in that manner would be rear engined not mid and would have
considerably worse balance than the traditional locost design where the engine sits a long way back from the front axle.
No, when the c of g of the engine is between the rear axle line and the drive it is mid-engined by definition. Old Beetles and Porsche 911s are REAR
engined.
(BTW, I agree that a locost engine IS close to the centre of the car but because it's in front of the driver it will always be front engined by
definition)
Typically a mid-engined car will be 40/60 F/R weight distribution, who says 50/50 is ideal anyway? And another important factor is that the
mid-engined powertrain is compact and contributes to a low polar moment of inertia (as opposed to engine and axle separated in a typical front engine
rear drive application)
I'm not knocking the longditudinal approach, it does have some advanages, and not many disadvantages which IMO would be a)slightly harder to find
gearboxes, b)longer wheelbase, and c)slightly more difficult gearchange to engineer.
|
|
|
Alan B
|
| posted on 5/8/02 at 10:13 PM |
|
|
quote:
Ok I accept all the points and of course it can be done and done well but my point is why?
Another factor here in the US is a shortage of suitable donors for a traditional Locost. Yes, there are plenty of front engine/rear drive cars but
most are fairly wide. I spent a long time looking for a suitable donor, and every cheap car was FWD, so I got to thinking "Hey, I always fancied a
mid-engined car anyway", so that's what I did, but with Locost principles in mind
It seems like we won't agree where the engine should be ....
but we don't have to do we? .....
|
|
|
Alan B
|
| posted on 5/8/02 at 10:20 PM |
|
|
quote:
Ok I accept all the points and of course it can be done and done well but my point is why?
Sorry if this looks like pick on Phil night
The question again why?
Well, why build a car anyway? Surely there's enough already made that you can buy?
My answer would be "because I can, and I want to make something different"
|
|
|
philgregson
|
| posted on 5/8/02 at 10:44 PM |
|
|
I have thought about building something with a logitudinal mid engine and trans axle for quite some time but the more I considered the traditional
locost layout the more I thought 'why try to be too clever?' and after several years of pondering and procrastinating I have decided to go down that
route.
I'm not trying to say that the transverse route is wrong or that there is anything wrong with individualism. Just that in my humble opinion the trad
route is so straight forward and effective that there seemed, in the end, to be little point in messing around.
|
|
|
Simon
|
| posted on 5/8/02 at 11:12 PM |
|
|
Alan B
"Typically a mid-engined car will be 40/60 F/R weight distribution, who says 50/50 is ideal anyway?"
You probably haven't seen B*W's ads in the UK's press about their weight distribution and that the front wheels are for steering and the back are
for getting the power down.
Funny how it's usually these severely overpriced / overweight / overhere things are the ones usually found in a ditch facing the wrong way!!
Wonder what happens when you fill the tank, put people in the rear seats and fill the boot, bet it's got a rearward bias then heh!!
Don't seem to have seen these ads since the launch of the new "Maxi"
Have I gone off on a tangent slightly?
Just my thoughts chaps:-)
ATB
Simon
|
|
|
MW
|
| posted on 9/8/02 at 12:25 PM |
|
|
I'm planning a mid engined locost based on the mk3 GE toyota supra including the LSD, Auto box and injection system(Ive already got the donor). Am a
bit worried about the chassi design bit, thinking of using a backbone in it to make it more ridgid/safe, anyone knowing about the road legal
technicalitys for chassi design could you mail me about it?
|
|
|
Alan B
|
| posted on 9/8/02 at 09:39 PM |
|
|
quote:
anyone knowing about the road legal technicalitys for chassi design could you mail me about it?
A lot depends what country you are in, and then, quite often, what region/state etc.
Did you check out my site:
http://www.desicodesign.com/meerkat/
Might give you some ideas.
Good luck.
|
|
|
