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Learning how to build Lotus Seven replicas...together!
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PostPosted: Tue May 04, 2010 3:28 pm 
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About 5 years ago my dad decided to build him self a Lotus 11 replica using an Elan +2's engine and suspension geometry. I helped him out when I could because I was still in high school at the time but learned a ton about chassis fabrication. At the same time I also got into autocross and started racing my CSP Miata. The Miata was never quite enough and have wanted to build a car for my self since.

Now that I'm an engineering student with to much time on my hands, I've decided to full fill this need to one up my dad (who is now considering a Lotus 40 replica). The project goals are as follows: Sub 1600 pounds, all wheel drive, 2 seater, build the car for less the $8000.

Here's my purposed plan so far. I want to power the car using a Nissan SR20DET (or optimally a CA18DET if I can verify the CA trans bell housing can be mated to an RB transmission because its 50 pounds lighter) mated to a R32 Skyline AWD transmission mid mounted with the transmission in the center tunnel. The Skyline transmission's output shaft spin counter clockwise in relationship to the front of the donor car but because I want to orient the transmission in the opposite facing direction I will need clock wise rotating differentials. I'm still hung up on where I'm going to source these but I am currently thinking of using Audi A6 rear diffs. The supporting frame for everything will be a 1-1/4" tube space frame with a minimalist fiberglass body. For suspension I plan to use Civic uprights with VW Corrado G60 11" rotors with 4pot Wilwood calipers. The control arms I am designing in SusProg3D and will be double unequal length control arms with rod ends. For steering I want to go with a 2 turn lock to lock sand rail steering rack. And finally I'm planning on making my own seats using the old expanding foam/trashbag technique for the plug which the fiberglass buckets will be based on.

For this kinda of project I realize its unnecessary to have awd but its more of an engineering exercise that I think will be fun and should have the potential to be reliable and stupid fast should I choose to boost the power down the road.

Sorry for the bad writing, my mind is kind of on overload from finals. Thoughts and criticism welcome.

-Spencer


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PostPosted: Tue May 04, 2010 8:40 pm 
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An engineering student with liberal amounts of free time on his hands?!? :shock: :BS:

While variations on similar ideas have been brought up and discussed a number of times before, I don't know of any that have even been started, let alone finished. Good luck if you decide to tackle such an ambitious undertaking. :cheers:

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PostPosted: Tue May 04, 2010 9:04 pm 
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Driven5 wrote:
An engineering student with liberal amounts of free time on his hands?!? :shock: :BS:

That's exactly what I thought... or maybe you're not a very good student :wink:

Yeah the problem is the whole 4WD idea is that there's just not the appropriate bits out there to do it "right" and end up with anything looking like a Locost.

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PostPosted: Tue May 04, 2010 10:59 pm 
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I'm a second year so I'm still mostly doing prereqs, so I still have time on my hands, and summer is coming up. Come fall though, that free time will pretty much disappear. I'm also taking school a bit slower than most so I can design and work on projects that compliment what I'm working on (e.g. designing a frame in cad while taking cad classes).

I've read a lot of those threads where people have proposed there idea (much as I have so far) and then not gone through with it though. I think a major part of it is they just don't do the research they need to or they shy away when the design element gets tricky. I've already priced out almost everything with the exception of misc. switches and relays and I think I have a good idea on what it will cost which is another area I don't think people look into enough. Right now I'm waiting for finals to end and then I'm launching straight into the project. Also the body is really the only area that has not been decided really but I realize (especially because its mid engine with a wide "north-south" transmission) that it will not look anything close to a 7.


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PostPosted: Wed May 05, 2010 10:39 am 
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Location: Tecumseh, Ontario Canada
While musing on another forum about an RS200 style drivetrain (mid-engine, longitudinal, AWD) the thought of using a relocated subaru transaxle with a fairly simple transfer box (cobbled out of $20 worth of e-bay circle track quick-change gears in a machined housing) was batted around. The center differential is integrated within the Subaru box and various torque split options, 50/50, 60/40 etc are available. Similar setups could be had using Skyline, Jeep or English Sierra 4wd setups but the Jeep stuff will have funky gearing and a fairly crude center diff, the others might be challenging to source parts for in North America.

Ted
Attachment:
sketch.jpg
sketch.jpg [ 62.35 KiB | Viewed 4948 times ]


The "Tim" referenced in the bad sketch is Tim from the RallyAnarchy board who crafted a similar transfer box for his bike powered Honda 600 LeMons car.

With some careful packaging and part selection you might be able to shoehorn this into a Lotus 23ish body. You'd have some tough packaging constraints in the footwell area though, might be able to use a compact diff out of an ATV or similar.

Attachment:
lotus23s.jpg
lotus23s.jpg [ 129.32 KiB | Viewed 4951 times ]


Cheers, Ted


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PostPosted: Wed May 05, 2010 3:44 pm 
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ted andkilde wrote:
While musing on another forum about an RS200 style drivetrain (mid-engine, longitudinal, AWD) the thought of using a relocated subaru transaxle with a fairly simple transfer box (cobbled out of $20 worth of e-bay circle track quick-change gears in a machined housing) was batted around. The center differential is integrated within the Subaru box and various torque split options, 50/50, 60/40 etc are available. Similar setups could be had using Skyline, Jeep or English Sierra 4wd setups but the Jeep stuff will have funky gearing and a fairly crude center diff, the others might be challenging to source parts for in North America.

Ted
Attachment:
sketch.jpg


The "Tim" referenced in the bad sketch is Tim from the RallyAnarchy board who crafted a similar transfer box for his bike powered Honda 600 LeMons car.

With some careful packaging and part selection you might be able to shoehorn this into a Lotus 23ish body. You'd have some tough packaging constraints in the footwell area though, might be able to use a compact diff out of an ATV or similar.

Attachment:
lotus23s.jpg


Cheers, Ted


The RS200 and the Veyron are where I got the idea for having the trans in the tunnel which is why I chose the skyline drive train. I wanted to use a sierra 4wd gear box but they are very rare compared to a Skyline box, but they can be had for between 500-1000 shipped on eBay. I'll have to look into the the Subaru transfer box idea but in general Subaru drive trains are a bit more than I wish to spend but if I can do it for cheap that might be the way to go.

As far as the body goes, I drew up a KTM looking car about a month ago that I wanted to use but now I'm thinking along the lines of a 23, 30, or even something based from a Ford p68. I haven't gotten very far as far as what it will look like. The big thing is trying to figure out the packaging first because the Skyline gearbox is by no means a small box so I'm still considering other options including a awd CRV gearbox with a rotated transfer box, but I'd really like to figure out the skyline box cause its so bullet proof. Still have a lot to figure out before I start buying parts.

-Spencer


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PostPosted: Wed May 05, 2010 3:52 pm 
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center diff's. ..
2004 jeep grand cherokee (wj) had a gerotor pump controlled single speed transfer case.
capable of 100% lockup as i recall, it used speed variance between front and rear to operate a pump that pushed the discs together, it was a new venture gear model 147. it came as part of a package putting the same mechanism into the dana 44 axles.

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PostPosted: Wed May 05, 2010 4:28 pm 
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This is the best I can find now, since my googlefu is not working.
http://www.nc4x4.com/forums/showthread. ... 56&page=17

Its using the FWD drivetrain set sideways in the mid/rear of a chassis to a solid axle. Just instead of a solid use a IRS front and rear with CV's out.

This makes the most sense. you would just have to flip one diff to make it go the right way I think, but thats menial given the rest of the design work.


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PostPosted: Wed May 05, 2010 7:55 pm 
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Thinkkker wrote:
This is the best I can find now, since my googlefu is not working.
http://www.nc4x4.com/forums/showthread. ... 56&page=17

Its using the FWD drivetrain set sideways in the mid/rear of a chassis to a solid axle. Just instead of a solid use a IRS front and rear with CV's out.

This makes the most sense. you would just have to flip one diff to make it go the right way I think, but thats menial given the rest of the design work.


If I'm seeing it properly, great for a rock crawler, not so good for a sports car -- you get a double reduction effect from the diff in the fwd box which then goes through the other diffs your top speed will be around 30mph.

t


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PostPosted: Wed May 05, 2010 10:00 pm 
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Thinkkker wrote:
This is the best I can find now, since my googlefu is not working.
http://www.nc4x4.com/forums/showthread. ... 56&page=17

Its using the FWD drivetrain set sideways in the mid/rear of a chassis to a solid axle. Just instead of a solid use a IRS front and rear with CV's out.

This makes the most sense. you would just have to flip one diff to make it go the right way I think, but thats menial given the rest of the design work.

ted andkilde wrote:
If I'm seeing it properly, great for a rock crawler, not so good for a sports car -- you get a double reduction effect from the diff in the fwd box which then goes through the other diffs your top speed will be around 30mph.

t


You can't run the transaxle sideways for the reason that ted sited. I'm talking about running the transaxle in standard orientation. The CRV awd trans has a transfer box that outputs to a center drive shaft to the back that can be rotated with the use of a very thing adaptor plate. There is justr enough clearance between the in the oilpan header relief and the clutch dust sheild to run the drive shaft through which is an alternative. My concern with doing this is I don't I don't know how the transfer case will perform upside down but It looks like its housing is symetrical so lubrication shouldn't be a problem but I have to look into it more.

The CRV transfer case is interesting because in its OEM application it only sends power to the rear wheels when it loses traction up front (I'll find the link that I read this from and post it later). In theory because I would move the rear diff to the front it should operate like the R8's awd system which only sends torque top the front in loss of traction and never more than 30% (I'm pulling this off the top of my head so I might be slightly off on the R8's system)

-Spencer


Last edited by worthingtontw on Wed May 05, 2010 10:37 pm, edited 1 time in total.

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PostPosted: Wed May 05, 2010 10:36 pm 
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The CRV transfer case torque split explanation I mentioned in my previous post. I don't know how accurate it is, but his explanation makes sense.

Post #11 by Rallysol
http://www.honda-tech.com/showthread.php?t=1708933

-Spencer


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PostPosted: Thu May 06, 2010 4:01 am 
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ted andkilde wrote:

If I'm seeing it properly, great for a rock crawler, not so good for a sports car -- you get a double reduction effect from the diff in the fwd box which then goes through the other diffs your top speed will be around 30mph.

t


Not if you step it up with chains. I drew a qic pic of that in the other thread .....

viewtopic.php?f=18&t=4846

Worth - consider a Mitsubishi 4WD box and run a Starion Turbo engine. Big power, cheap and strong. You choose to add an external central diff or not.

Have you ever picked up a R32 box - neither have I cause you need about 8 guys to do so and where i come from they are known to be both weak and very expensive.


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PostPosted: Thu May 06, 2010 4:09 am 
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huh,

I changed a clutch on a mitsi evo 8 the other day and the gearbox is also a heavy bas$%#d.. AWD is best kept for powerfull rally reps.. :)

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PostPosted: Thu May 06, 2010 4:37 am 
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A gt-r trans has the front diff in the oil pan of the engine... so that may not be the best idea...


search this forum for "all wheel drive locost"...

I'm not trying to discourage you, I'd love to see it built. There isn't one in the US to my knowledge yet, would be awesome to see the first!

I've been considering using a saab b234r with a 325ix(as in all wheel drive) drive line... There are already adapters on the market for the the saab motor/bimmer trans setup... and they stuff 'em in miatas...


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PostPosted: Thu May 06, 2010 5:05 am 
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krepus wrote:
A gt-r trans has the front diff in the oil pan of the engine... so that may not be the best idea...


search this forum for "all wheel drive locost"...

I'm not trying to discourage you, I'd love to see it built. There isn't one in the US to my knowledge yet, would be awesome to see the first!

I've been considering using a saab b234r with a 325ix(as in all wheel drive) drive line... There are already adapters on the market for the the saab motor/bimmer trans setup... and they stuff 'em in miatas...


....any links or pictures to hand please/


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