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Learning how to build Lotus Seven replicas...together!
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PostPosted: January 16, 2016, 11:01 am 
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Location: Brandenburg, KY
As I begin my homework on building a Locost (see Leaning Locost in this section) I need to determine if my engine choice will fit the standard "book" frame without modification.

My fabrication skills are very novice and my brain does not comprehend Geometry well at all, so I will need to "follow a plan" as much as possible.

I saw a post where someone proposed moving the transverse tubes back (along with everything that lines up with them, such as the scuttle/ dash) to shrink the cockpit opening and lengthen the nose a little bit. Using an inline 6 cylinder engine (Chrysler Slant 6) may require lengthening the nose and I am not too concerned with a large cockpit (I'm 5' 11"). I plan for this car to be as small and light as possible for track use only. I will likely leave the engine uncovered initially, so the bonnet is not as much of a consideration.

Here are the engine/trans dimensions:

Slant 6 engine measurements:
Length: 32 ½” with the fan
Height: 24” at the valve cover. (Carb will be higher)
Width: 17” w/stock manifolds (HyperPak will stick out considerably)
Weight: 450 lbs fully dressed

A904 trans measurements:
Width: 18” at the bellhousing
Taper: ??? I need to get a good measurement on where it tapers down
Length: 30” to output shaft (34.12” to yoke/23.5” to trans mount

Some sage advice would be greatly appreciated. Thanks!


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PostPosted: January 16, 2016, 6:44 pm 
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The A904 along the pan is nearly as wide as the bell.

A book chassis is only 42 inches wide. Subtract the outboard rails, inboard rails, clearance to the trans, and the trans width leaves way less than you need for two people to sit. Set up a few boards around you to determine how much space you need in length for pedal travel and seat back and width with a little padding on the sides.

A 442 is probably your best bet for popular sizing. Then you can fit a 273 if you want later on.

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PostPosted: January 17, 2016, 1:20 am 
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There actually was a Slant 6 Lotus 11, built by some Chrysler engineers in the '60s.
http://www.valiant.org/lotus.html


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PostPosted: January 17, 2016, 9:26 am 
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Location: Brandenburg, KY
Thanks again Miatav8. More great advice. Has anyone done a comparison on the weight difference between the Book and 442 chassis? It is probably negligible considering I will likely want to give someone a ride around the autocross from time to time.

Thanks TRX. Miatav8 had shared that link as well. Way more intense than what I am planning, but I do have a HyperPak to go on it. :wink:


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PostPosted: January 17, 2016, 5:13 pm 
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I spent some time going through and printing pages from the various chassis designs on the Sevenesque site today.

I like the 442E design for the extra 4" length in the engine bay for my 32" long engine! :shock: I would prefer the original narrower nosecone, but that may not be possible with a 17+" wide engine...

The 442 gives you an extra length of 2" in the engine and 2" in the cockpit, but with the original width of the Book chassis in the engine bay. The extra width is only in the rear and cockpit.

I'll look around at more build threads and play around with my engine/trans measurements... I really prefer the narrower look... Hmm... More to follow... :D


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PostPosted: January 20, 2016, 5:32 am 
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I assumed you wanted plans. Ideally, you build to fit the equipment and driver, then scale up the rest as required to keep the proportions.

Draw all you want to get an idea on the scale, but jig the fully assembled drivetrain (including alternator) into the build table and maintain the passenger compartment size. Leave room for access when the chassis is skinned.

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PostPosted: January 20, 2016, 8:42 am 
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Thank you. All good points again. It kinda sounds like you may have built one or two of these things... :wink:

I would prefer to follow a ready made plan given my limited fabrication skills and inability to comprehend simple geometry. :oops:

I've got some friends doing some specific measuring of their Slant 6 and A904 set ups to help me out. I will add the accessories like alternator into my measurement request. Several of the racers have moved the alternator (typically it sticks WAY out there) to a lower, more tucked in position.

I have seen a couple of the track only Locosts running without any body work (skin) around the engine. That would be my initial plan, but that certainly is a consideration. Especially if I do wind up making it street legal at some point in the future.

I appreciate the replies to help steer me in the right direction.

Rob


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PostPosted: January 20, 2016, 6:33 pm 
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This should explain the process if you decide to tweak your plans. IMHO, 5 inches would be applied to a book chassis, with similar height to the scuttle. It would also be a good idea to have the nose on hand and jigged prior to building.

No, I have not built a traditional locost but it seems like I've built everything but that.


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Chassis Stretching.jpg
Chassis Stretching.jpg [ 454.2 KiB | Viewed 3067 times ]

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PostPosted: January 22, 2016, 7:56 am 
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You Sir, are very helpful indeed! Thank you for that illustration!

I definitely see the need for the engine bay stretch lengthwise.

A 5" stretch in width would require a custom (reworked) nose cone...

Several folks have mated a T5 to the Slant 6. I'm doing some comparisons to see how much, if any, that would help the "dimensional dilema".

I've also been following some of your other posts regarding suspension design. The 3 link reference you just posted looks like a very "simple" design in concept. I'm sure it's much more difficult to execute.

Has the 3 link design been used with success for autocross type driving? I wonder how effective it would be for drag strip type launches... :?

I may need to factor in a set of wheelie bars for this thing! :shock: :lol:

Thanks again for your very helpful replies to my newbie questions.


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PostPosted: January 22, 2016, 5:21 pm 
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There are several nose cones and frequently, they are split down the middle to widen as required. I also determined that a 555 adds approximately 20 lbs or less to a tiny book chassis.

A 3 link is an option with factory five cobras, and would be much easier to install than a suitable irs. Much better traction can be had with a 3 link or 4 link.

I’d keep the 904. You can always put in a manual later. Take a look at the Dodge Dakota manual trans instead of the T5 if your serious about a manual. Also remember the footwell will need to be wide enough to accommodate a clutch pedal.

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PostPosted: January 23, 2016, 4:34 am 
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Awesome! Thanks again. I'm liking the simplicity of the 3 link.
Many say the über low 1st gear in the Dakota trans makes it not so great for racing (?)
I've actually been exchanging emails with Jack about the possibility of him getting me started with the frame while I'm still here so I can jump into assembly when I get back.
Trying to start one here and hassle with customs to bring it back may not be very doable. Lots more homework to do.
Thanks again!


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PostPosted: January 23, 2016, 7:14 am 
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viewtopic.php?f=4&t=12841&p=129226&hilit=dakota#p129226

The Dakota bell adapts to an AX15 trans which is available with different ratios for different applications. The photo is of a Toyota supra AX15 bolted to the Dakota bell. As for the Dakota 1st, you could always start off in second and kill some wheel spin. First is available if you want to use it, such as crawling in traffic just like 5th is available if you want to save fuel and cruise, not acceleration at normal highway speeds. That is what 4th is for. If you build just big enough for a manual, forget putting in a 904 later. (That reminds me, about a decade ago, there was this fellow who had a turbo miata and put in a ford v8 driveline. He was complaining that the turbo miata pulled really hard in 5th, but the ford v8 did not pull as hard in 5th, yet pulled harder in 4th. I did the math, and the gearing of the turbo miata in 5th was exactly the same as the v8 miata in 4th. I told him to leave it in 4th. 5th is for mpg and cruise.) :lol:

If you want it to be all dodge, all the rwd dodge spindles are rear steer which interferes with the oil pan. However, the toe arm and lbj attachment bolt on to the spindle, so new brackets could be made to adapt front steer and a different joint. It is also possible to swap sides making them front steer, but there may be other issues such as caster built into the spindles or Ackermann. It would be easier to use ford bits that are front steer. The dodge applications are mid 70s through mid 80s cars, though the trucks may work.

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PostPosted: January 23, 2016, 7:25 am 
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I'll plan for the 904. I may go ahead and install the clutch pedal (or at least plenty of room for one).

I am just dedicated to the Slant 6. The rest of the drivetrain and suspension is not as much of a concern. Although I would like to have the 5 X 4 1/2 bolt pattern so I can use the myriad of wheels I already have. It might be cool to use a pair of Mopar Rallyes or Magnums from time to time. :!:


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PostPosted: January 23, 2016, 7:33 am 
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Yeah, the slant six is plenty of power, for sure. I thought you might want to run mopar wheels which is why I mentioned the ford suspension. I used mopar ralleys on a 67 mustang in high school because magnum 500s where prohibitively expensive.

If you can't find a good deal on pinto/mustang II spindles, 80s full size ford/lincoln/mercury spindles can be used, among others.

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PostPosted: January 23, 2016, 8:06 am 
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Location: Brandenburg, KY
I have a Turismo that has been converted to RWD. Unfortunately, I was even less informed then as I am now...
The welder that volunteered his services (it was a church youth group project) was used to building rat rods and not as much with some of the other stuff. His idea was to simply turn the entire front subframe around to make it front steer and give room for the oil pan.
That car still sits next to my garage the way I picked it up from him. It will all need to be redone. Another long term project that may never get finished. It does have a shortened 8 3/4 under it... Probably too narrow for a Locost.


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