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Learning how to build Lotus Seven replicas...together!
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PostPosted: September 26, 2017, 12:40 pm 
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Hi all hopefully I'm not out of line in asking this but I'm looking for some direction on a build. Here is what I'm working with/thinking...

-I want to build a weekend racer/summer day cruiser car so it needs to be road worthy.
-Racing would primarily be autoX and drag racing.
-Drag racing I want to be able to kiss 10s maybe high 9s. Car should really not be over 2000 lbs hopefully a good bit less.
-I'm 6'-2' 230lbs so I think a 442e is going to be necessary for me to fit somewhat comfortably.
-Want to build for either an LS or Coyote power plant. 450hp is the target.
-Not sure on trans yet maybe a dog box or 6 speed manual, I have thought about a 6l80 with shift kit and manual shift paddles but that may not be responsive enough I'm not sure...

Here are some of the questions I have.

1. Chassis. Is there a plan that would be good to work off that incorporates a NHRA/IHRA legal roll cage? Or at the least is there a CAD model I can start from?
2. Donor. Is a miata going to be too light duty for what I'm doing? I've thought about using a lexus sc300/400 or IS 300/350 as they are pretty easy to get cheap and all the components are already going to be super beefy for high torque use.
3. Is there enough of a benefit to going IRS to make the extra work worth while? Ford 8.8 rear diffs are super easy to find and can take a monster beating...
3. Why don't people use the factory donor suspension components? Is there something I'm missing here? For example it seems like if you're going to use a miata donor that one would want to use the whole suspension, even if you don't use the sub-frame?

I guess those are my starting questions for now. Thanks for all the patience.


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PostPosted: September 26, 2017, 1:52 pm 
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I would have a look at Car-9 for a chassis starting point (seattle toms car-9 has one of those motors with too many cylinders and not enough cams :boxing: ). It is designed for IRS, but I'm sure Marcus could do some jiggery-pokery to make a live axle work.

In regards to why using stock suspension components isn't common, they typically don't look the best on a somewhat open wheeled car. Plus, by building your own you can tailor the suspension to what ever you desire.


here's a link to Tom's car: http://www.locostusa.com/forums/viewtopic.php?f=35&t=14613


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PostPosted: September 26, 2017, 2:15 pm 
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Here are some more thoughts for you! I'm 6ft, nuthin' and 265# but I managed to get into a "book frame" car. Wouldn't want to spend the whole day there, but you get the drift. You might want to look at a 221. That's what I'm planning on building. The Miata parts you're considering should be OK, if not ideal. Look at the V8 Miatas that Flying Miata is putting together. If further on it appears that the brakes are lacking, there are big brake kits available.

One more thing that we tell many of the newbies here is to let us know what part of the world you call home. Many times you can be directed to someone in your vicinity that is building, or has built a Locost and can give you some hints, tips, and pointers.

Good luck with your project! :cheers:

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PostPosted: September 26, 2017, 3:04 pm 
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Welcome
I can say that 6'-2' & 230lbs can fit comfortably in a book chassis. I had a passenger about that size in a 16.5" wide seat area and we drove for 12+ hrs straight and then back again a few days later. For a book frame, or any variant, keep the driveshaft framework as narrow as is necessary to maximize the seat width. What may be more difficult is the shoe size that goes with the 6'-2' 230lb body. The footwell can be very tight to fit 3 pedals. This is more difficult if your starter is on the driver's side.

I'll second adding the location info. Perhaps you'll find a car that you can sit in to find the best fit. But keep in mind, even 2 seemingly identical book cars can feel very different. I know I didn't like the tight feeling of a Birkin but my book chassis (only 2 inches wider) had gobs of room.

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PostPosted: September 26, 2017, 4:21 pm 
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Let me add that if you build a book chassis then you will never want to have a passenger as elbows simply don't fit for turning the wheel or changing gears. Car 9!!

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PostPosted: September 26, 2017, 5:13 pm 
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I agree with the others, you shouldn't have any issue fitting in a book frame car. That's what I built, and I'm 6'2", about 285. It's definitely tight, but I can drive it for an hour or so before getting too uncomfortable, and have been in it for as long as 2 hours on the highway. I'd also echo the comments to look at the Car9 design that Marcus put together. I want to build another locost using that frame design, and I already have on on the road. How heavy is a ready to run Coyote? The old 302 Ford can be pretty light, and is about the most compact V8 that is commonly available in North America. 400hp isn't overly difficult either.
Kristian

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PostPosted: September 26, 2017, 10:47 pm 
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Talk to the NHRA drag guys first about cage requirements. You may find it difficult to get what they want on a locost chassis.
I'd suggest running live axle over IRS if you want to dragrace and autoX. At autoX, that car is going to be a point-and-shoot car, not a momentum car. Use the antisquat of the live axle to get your traction and put some power down. Drag racing you want a ton of antisquat which IRS will not get you.

Cheers.

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PostPosted: September 27, 2017, 9:55 am 
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ngpmike wrote:
Here are some more thoughts for you! I'm 6ft, nuthin' and 265# but I managed to get into a "book frame" car. Wouldn't want to spend the whole day there, but you get the drift. You might want to look at a 221. That's what I'm planning on building. The Miata parts you're considering should be OK, if not ideal. Look at the V8 Miatas that Flying Miata is putting together. If further on it appears that the brakes are lacking, there are big brake kits available.

One more thing that we tell many of the newbies here is to let us know what part of the world you call home. Many times you can be directed to someone in your vicinity that is building, or has built a Locost and can give you some hints, tips, and pointers.

Good luck with your project! :cheers:


Would a 221 be large enough to fit me an a v8 power train? I can see if the car is running something small like a miata power plant I could wedge into it but with a larger trans and longer v8 would it work?

Also I'm in central Manitoba, Canada

carguy123 wrote:
Let me add that if you build a book chassis then you will never want to have a passenger as elbows simply don't fit for turning the wheel or changing gears. Car 9!!


This is going to be important as I want to be able to drive it on cruise nights etc with bros or the wife...

turbo_bird wrote:
I agree with the others, you shouldn't have any issue fitting in a book frame car. That's what I built, and I'm 6'2", about 285. It's definitely tight, but I can drive it for an hour or so before getting too uncomfortable, and have been in it for as long as 2 hours on the highway. I'd also echo the comments to look at the Car9 design that Marcus put together. I want to build another locost using that frame design, and I already have on on the road. How heavy is a ready to run Coyote? The old 302 Ford can be pretty light, and is about the most compact V8 that is commonly available in North America. 400hp isn't overly difficult either.
Kristian


The Coyote is about the same weight as an aluminum LS or lightener 302. However the kind of power you get from one is [Fornicating] delightful compared to the older 302s and I think its a more racy feeling motor over an LS. The downside is the heads are big and availability is limited compared to an equal LS motor. Mostly I'm thinking Coyote because I'm more of a Ford guy That said I could easily see myself using an L92 (6.2L truck LS) as they are overall pretty compact and things like cam changes etc are quite affordable. The goal is the keep the motor at around <450 lbs.

So how does a live axle locost compare to an IRS locost in terms of handling?


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PostPosted: September 27, 2017, 11:06 am 
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Welcome to the forum. Nice to have another person from Manitoba. I've got a 221 frame up on the build table at the moment with the engine and transmission (Fiat 124) in place. You're welcome to come sit in it. I'll sit in it with you if you want so that you can look at the elbow interference. My car is in my hanger at the airport in St Andrews MB. The local locost builders are due for a garage crawl. If we can get that organized soon you'd have a chance to sit in a few frames and ride in one or two, depending on timing (snow) and whether Chris and Bob are available and have their cars licensed.

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PostPosted: September 27, 2017, 12:57 pm 
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BHRmotorsport wrote:
Welcome to the forum. Nice to have another person from Manitoba. I've got a 221 frame up on the build table at the moment with the engine and transmission (Fiat 124) in place. You're welcome to come sit in it. I'll sit in it with you if you want so that you can look at the elbow interference. My car is in my hanger at the airport in St Andrews MB. The local locost builders are due for a garage crawl. If we can get that organized soon you'd have a chance to sit in a few frames and ride in one or two, depending on timing (snow) and whether Chris and Bob are available and have their cars licensed.


Awesome offer. PM sent!


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PostPosted: September 27, 2017, 1:08 pm 
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Has a car9 been built yet?


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PostPosted: September 27, 2017, 10:11 pm 
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Location: White Rock, BC, Canada
suprathepeg wrote:
So how does a live axle locost compare to an IRS locost in terms of handling?


Depends on how bumpy it is. Smooth track or autoX pad, the live axle will likely outperform the IRS*. You will have more grip on throttle which lets you use throttle to steer much more. The only downside is less/no camber to the rear tires. With V8 power, I think grip on corner-exit will be more useful than slightly higher speed in corner-entry to mid-corner. Bumpy surface (potholes, uneven pavement, washboard, etc), the IRS is the better option by far. Over crests/humps/dips the live axle is still fine, it's the surface irregularities that that upsets it. It's pretty jarring when both my rear wheels have to pop up at the same time over a raised 3" bump.

For the drag-strip there is no question: Live axle is what you want.


*Subject to argument I am sure. But V8 power in a homebuilt car, with an amateur driver I'll bet that IRS would be slower.

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PostPosted: September 30, 2017, 1:12 am 
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The Haynes is a 221 design. If you can't find the book any more someone here probably has a PDF copy of the thing (cough). The Haynes is IRS, but I easily enough modified it for a 10 bolt Chevy out of an S10 (which fits nicely).

Strangely enough, the actual space requirements between an I4, V6 and small block V8 don't seem to be that much different in some cases. My V6 fits easily enough.

Please note -- these cars started off as an exercise in LOW WEIGHT not HIGH HP. If you bump up the HP, start running wrinkle walls... well, this stuff used to twist full-body frames, right? With increased HP comes increased headaches and weight. Unless you're running an IndyCar or something.

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PostPosted: September 30, 2017, 11:00 am 
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Location: Carlsbad, California, USA
The amount of power and torque appropriate for these little cars is a question each builder has to answer for themselves. It can seem like lecturing to bring it up to a new builder, but it is an issue. When I started out, I planned a turbo-charged 4-cylinder car, but fell in love with a Ford 5.0 Locost that a member here built. Over time, and after watching a number of YouTube videos of very high performance Caterhams (one with a Cosworth V8, for example), I came to feel the down side of a big V8 was too much, and that a lighter powerplant with less torque was a better choice for me.

In the end, I settled on a 3.8L V6 with aluminum heads that is right about the same weight as a Lima (Pinto) I4 that was so popular in the first generations of Locosts. I'm targeting 300 HP eventually. I know the car will be a challenge to drive then, but that's what I'm looking for anyway.

Here is an example of a recent video road test by a UK auto blogger of the Caterham 620R. It's fun, and brings the Power/Torque/Weight/Safety/Driveability issue right out there explicitly.

Caterham 620R video road test ==> https://www.youtube.com/watch?v=CRKu5-9q9jk

Just to let you know where my thinking is, here's my favorite "sevenesque" video. It's my idea of a fun Sunday ride in the mountains (God help me!). It's a Dutch 7-clone with a S2000 engine, driven by an Italian :roll: . Make sure the auto translation is on and you'll get a conversion of the audio into English on screen.

My favorite ==> https://www.youtube.com/watch?v=wDMukessQtk&t=333s

Take a look at some of the other videos of the large-engined cars. They can be difficult to control under performance driving conditions.

Cheers,

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Build Log: viewtopic.php?f=35&t=5886


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PostPosted: September 30, 2017, 11:19 am 
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suprathepeg wrote:
The downside is the heads are big...
...Just a bit:

Attachment:
Coyote LS3.jpg
Coyote LS3.jpg [ 65.74 KiB | Viewed 348 times ]

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