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Learning how to build Lotus Seven replicas...together!
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PostPosted: April 5, 2012, 9:22 am 
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Tried to post this in FAQ.

The original Sevens place the engine well forward, usually where the flywheel is actually about 4 inches forward of the front edge of the footwell. This placed the footwell along side the narrowest part of the transmission instead of the bell housing.

The earliest Sevens have tiny engines that are very short, so access to the front of the engine without nose removal is not too bad. As the engines got bigger (and heavier), the location of the flywheel remained the same. In many cases, the valve cover is forward of the rear edge of the nose by several inches.

If reducing the polar moment by placing everything as close to the center of the car as possible, and easy access to the front of the engine without nose removal is important to you, consider:

1) Using a wider passenger compartment and rear frame, to allow the flywheel to be further aft, and the tunnel to be wider, with more taper of the engine bay frame in the overhead view.

2) A longer wheelbase by lengthening the engine bay frame, to shift the cg aft and provide better front engine access, with the flywheel in the standard position.

3) Both


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PostPosted: April 5, 2012, 11:52 am 
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How about a second 'jog' in the frame rails, one at the floorboard like the one at the back of the scuttle? That would provide...
> more taper of the engine bay frame in the overhead view
...without widening the passenger compartment and rear frame. Generally the limit on passenger compartment width is the rear track less the rear tire width. Of course, more taper in the engine bay would require (shudder) making a brand new nose.

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PostPosted: April 5, 2012, 6:16 pm 
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My suggestion is if there is no room for a joggle toward the bell housing, to have the engine no more aft than necessary for practical purposes. It is much easier to change the mounts and have a longer driveshaft made. Also, for those who base the engine position off of where the shifter mount on the transmission happens to be, the originals had a shifter buried behind the dash, with a link rod to a hinged shifter mounted to the top of the tunnel, so shifter position should not take precendent over happy feet.

An appropriate width axle of course, but also with longer control arms and tie rod adjusters for a matching track, while keep the same nose. The taper change would begin where the tubes emerge from the rear of the nose. Different offset rear wheels could be enough for clearance. I'm suggesting subtle changes.

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Miata UBJ: ES-2074R('70s maz pickup)
Ford IFS viewtopic.php?f=5&t=13225&p=134742
Simple Spring select viewtopic.php?f=5&t=11815
LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12


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PostPosted: April 5, 2012, 9:41 pm 
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Could this be the answer?

http://www.youtube.com/watch?v=3FGDnXWUCpc

:mrgreen:

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PostPosted: April 6, 2012, 12:50 pm 
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For those who have built and weighed Miata-based Locosts, some fore/aft weight info would be nice. I'll bet using the rear subframe is worth a few inches forward with the engine. 'Course, then you're losing the low polar moment of inertia benefit of the Se7en concept...

Wait a minute. Other than battery placement, it doesn't look like the Lotus 7 was designed with any concern re minimizing polar moment of inertia. Minimizing inertia, yes, but keeping the mass in the center, no. Indeed (dare I say it?) it looks like the driver and engine are spread as far apart as possible while keeping the 50/50 weight distribution.

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PostPosted: April 6, 2012, 1:15 pm 
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JackMcCornack wrote:

Wait a minute. Other than battery placement, it doesn't look like the Lotus 7 was designed with any concern re minimizing polar moment of inertia. Minimizing inertia, yes, but keeping the mass in the center, no. Indeed (dare I say it?) it looks like the driver and engine are spread as far apart as possible while keeping the 50/50 weight distribution.



That's a thought I've had several times myself. The drawings of the early models brought it to my mind again.

My first thought in that thread was just to lengthen the wheelbase a little to move your feet back past the flywheel area & add more room in the cockpit to make it more comfortable all the way around.

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PostPosted: April 6, 2012, 3:34 pm 
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Two things come to mind,
1. A BEC has all the big stuff forward of the firewall so the tunnel doesn't need the expanded area in the front on the left side. The torsional strength of the chassis will go down somewhat. In my case I was able to mount a 2" deep aluminum cooking pan to the right of the gas pedal on the inside of the tunnel to give me an additional ~3" of foot room even with an expanding tunnel in the front. By using a high offset pinion rear end the engine can be moved a little to the right as compared to a centered pinion.

2. Buy using a rear axle with a high offset pinion [towards the right side]. Perhaps the engine/xmission can be mounted off set in the chassis so the drive shaft goes [more] straight back to the pinion by the amount of pinion offset. That would help to offset the drivers weight on the left side of the car. This might make it possible to get closer to a 50%:50% side to side balance.

A WAG would be a driver at 160# with his C/G 11" to the left vs the weight of the heavy stuff ~450# offset to the right,
Offset = (160 x 11) / 450 = ~4" (the offset pinion/gears etc come into play also)

To get the actual number you have to figure in the weights of the steering column, battery, exhaust system and what ever else is heavy. Luckily the passenger doesn't need as much foot room.

About lengthening the W/B. The book chassis is ~4" more W/B than the original car.

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PostPosted: April 6, 2012, 9:03 pm 
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JackMcCornack wrote:
Wait a minute. Other than battery placement, it doesn't look like the Lotus 7 was designed with any concern re minimizing polar moment of inertia. Minimizing inertia, yes, but keeping the mass in the center, no. Indeed (dare I say it?) it looks like the driver and engine are spread as far apart as possible while keeping the 50/50 weight distribution.


That's the thing that I find amusing.

According to Locost logic, the original Lotus 7 did it all wrong. Weak engine, out front. Skinny tires. And look at that frame -- no tunnel tubes?!?!?!

I tried on an original 7 at a vintage event at Road America. IF memory serves, it was a series 2. First thing I noticed when I finally got my legs slid under the wheel was that my right hand (it was a right-hand drive) was on the ground. The other thing was that, to my amazement, my 6'1" American-sized body actually fit, and I could work the pedals with my size 11 1/2 shoes on.

Oh, and the car had been driven once by Dickie Smothers, and Dickie had autographed the thing. "Drive this car and stay young" or something. Anyone know this car?

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PostPosted: April 6, 2012, 9:14 pm 
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Is this it?

They got some things sooo right, it made up for the wrongs. Also look at what they were running against in the handling department.


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Ford IFS viewtopic.php?f=5&t=13225&p=134742
Simple Spring select viewtopic.php?f=5&t=11815
LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12


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PostPosted: April 6, 2012, 10:39 pm 
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Miatav8,MstrASE,A&P,F wrote:
Is this it?


Don't think that's the one... that's a S4, isn't it? But my memory is fading, or maybe it's just cluttered now?

The story went that the owner of said Lotus 7 knew that Dickie used to race a 7, and used that car to pick Dickie up from the airport. Needless to say, Dickie was late to rehearsal for the gig that night.

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PostPosted: April 6, 2012, 10:43 pm 
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geek49203 wrote:
I tried on an original 7 at a vintage event at Road America. IF memory serves, it was a series 2. First thing I noticed when I finally got my legs slid under the wheel was that my right hand (it was a right-hand drive) was on the ground. The other thing was that, to my amazement, my 6'1" American-sized body actually fit, and I could work the pedals with my size 11 1/2 shoes on.
Unfortunately I don't know my history well enough to say for certain exactly what car I tried on, but while I technically "fit" and could physically operate the pedals...My 6'0" American sized body was literally wedged into the car. My first attempt at sitting ended with my posterior squished between the upper rails and the edges of my hip bone resting not-so-comfortably on the upper rails. About this time a small crowed started to form much as they would if watching an elephant try to ride a donkey. After lifting myself out enough to make a second go at it, this time I tilted my hips about 30* to the side and barely squeezed them past the top rails with a bit of a 'pop' as I suddenly came to rest on the small cushion beneath me. Admittedly once my hips got past the point of no return, the extra inch or so of width that my body was allowed to fill out against the side panels created what would have been fantastic 'racing seat side bolsters' had I been going for a drive. While I was unable to adjust my body in any way, sitting in the car was not terribly uncomfortably...But I wouldn't want to do it for extended periods of time. While my feet could actuate the pedals (all three at once if I wasn't careful) my legs would have been far more comfortable if my feet could have been moved behind the pedals. After enjoying a minute or two of sitting in the car, I had to figure out just how to extract myself. Unfortunately once wedged in, its noticeably harder to rock your hips to the side...Which provided another round of amusement for the gathered crowed, who were treated to everything they were waiting for.

So from my point of view, there were a few things about the car that certainly could have been improved upon somewhat...With the footwell definitely being one of them.

Here is a pic of the car in question, if anybody can positively identify it.


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PostPosted: April 7, 2012, 6:25 am 
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Geek,

that is an S2. I think the one Driven posted is an S3 with most of the rear fender lip cut away for tire clearance. The easiest way to tell the difference is by the shape of the outer flange of the rear fenders. S3 is slab/flat-sided, where the S2 has beaded and radiused /compound curved flange.

The S4 front fenders touch the rear fenders. It looks much more like a 70s kitcar inside and out, but was also more practical for everyday use than the others. The entire body was fiberglass, and the nose and bonnet are one piece, tilting forward for access. Lots of flat panels with short radius curves in the corners, so it is "boxy".


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Miata UBJ: ES-2074R('70s maz pickup)
Ford IFS viewtopic.php?f=5&t=13225&p=134742
Simple Spring select viewtopic.php?f=5&t=11815
LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12


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PostPosted: April 7, 2012, 1:07 pm 
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Thanks for the clarification on identifying an S2 vs S3...Yeah those S4's were definitely the black sheep of the family.

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