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Learning how to build Lotus Seven replicas...together!
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PostPosted: July 19, 2018, 8:45 pm 
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Hi I'm new and looking forward to my first Locost build (through KV). I've built many cars and bikes in the past. Just finished a Sheridan wide-bodied sbc 914 track car and now I'm looking to build something new.
I happen to have a 928 engine (with ECU), trans axle, front hubs and complete rear suspension. The rear track is 60.8". The engine is 575 pds (heavy I know) complete and with headers and a X pipe can get 300hp fairly easy. A drawback is the weight of course, but the other drawback is the engine size itself. Quite wide, especially from head to head (27") and front to back (also 27"). By comparison, a sbc is roughly 20X20. But the advantage is I have all these parts free.
A cursory search didn't yield anything so I wonder if I'm going down a road less traveled?
I suppose the first thing I need to determine is the engine bay framework width. It appears as if the area closest to the firewall is some 32" wide and it tapers to a mere 20" the 34" of engine bay length. I wonder what the width is 27" from the firewall?
I don't know the height dimension yet (of the engine) so that's a variable I'll need to obtain. And at this point I know nothing the dimensions of the trans axle, other than hub to hub length (60.8").
Chime in if you've either done or know of someone that's done this build. Haters are gonna hate and that's fine, I'm still intrigued the possibilities.


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PostPosted: July 20, 2018, 1:55 pm 
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FREE is a very good word around here. :mrgreen:

Are you aware of the various McSorely versions of the Book frame? They vary in width and height of the chassis, but have the same basic architecture. There are some 3D models of them available online. If you have a 3D design software, you could load each of them up and use the measuring tool (they all have one) to answer the questions you have.

With the power and torque of a 928 engine and a big transaxle (I seem to remember the 928 used hefty one), I'd count on re-enforcing the Book design in several areas, plus designing your own subframe at rear, of course.

Keep us posted.

Cheers,

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Damn! That front slip angle is way too large and the Ackerman is just a muddle.

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


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PostPosted: July 20, 2018, 4:05 pm 
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Mid-Engine build!

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PostPosted: July 20, 2018, 9:37 pm 
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Location: ontario
[/quote]

I have not heard of a porsche 928 engine in a locost. You are lucky to own such an engine.
I think that I would build a seven frame augmented (as you read above, suggestions for a larger seven are available in the Mc Sorley sevenesque files). Mc Sorley offers frame sise alternatives but as I recall does not expand on the particular requirement of a powerful V8 on a smallish car such as the seven (but I may be wrong). You may want to search for discussions of V8 powered even construction. In a nutshell the seven chassis needs to be significantly reenforced to safely accomodate a V8 and I think that the original Porsche configuration (front engine rear drive) would be your best bet :)


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PostPosted: July 21, 2018, 12:01 am 
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phil wrote:


I have not heard of a porsche 928 engine in a locost. You are lucky to own such an engine.
I think that I would build a seven frame augmented (as you read above, suggestions for a larger seven are available in the Mc Sorley sevenesque files). Mc Sorley offers frame sise alternatives but as I recall does not expand on the particular requirement of a powerful V8 on a smallish car such as the seven (but I may be wrong). You may want to search for discussions of V8 powered even construction. In a nutshell the seven chassis needs to be significantly reenforced to safely accomodate a V8 and I think that the original Porsche configuration (front engine rear drive) would be your best bet :)[/quote]

I assumed that sbc or LS engines had been done? The 928 engine (while free for me) is certainly less a monster than a well breathed sbc or LS. Heavier than a sbc for sure (by some 75 lbs) but no more powerful and definitely less torquey.
I'm researching the files to see about the McSorley wider chassis as no doubt that would be necessary to accommodate the rather huge physical size of both the engine (27"X27", some 7" wider and longer than a sbc) and trans axle (dimensions unknown at this time). That said, if I found other builds that were either sbc or LS engines, it would go a long way helping me understand the reinforcing that will be required.
Anyone know of other members that have build threads either a sbc or LS engine?


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PostPosted: July 21, 2018, 11:01 am 
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I guess if anythings going to work it'll be the McSorely 442E w/ reinforcements.


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PostPosted: July 21, 2018, 11:03 am 
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Lonnie-S wrote:
FREE is a very good word around here. :mrgreen:

Are you aware of the various McSorely versions of the Book frame? They vary in width and height of the chassis, but have the same basic architecture. There are some 3D models of them available online. If you have a 3D design software, you could load each of them up and use the measuring tool (they all have one) to answer the questions you have.

With the power and torque of a 928 engine and a big transaxle (I seem to remember the 928 used hefty one), I'd count on re-enforcing the Book design in several areas, plus designing your own subframe at rear, of course.

Keep us posted.

Cheers,


Thanks for the input! Why do you think a rear (and presumably separate) sub-frame should be used?


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PostPosted: July 22, 2018, 5:54 pm 
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That's a big motor. Nearly three times the volume of a Ford small block. The bell housing measurement is pretty important and might not be much different though. The Ford is about 19" wide without an exhaust manifold. Height is a big factor in fitting large motors too, but many modern 4 cylinder engines are quite tall.

You can look at Seattle Tom's build of a Car9. He is using an LS engine, it fits well and the frame is quite strong. http://www.locostusa.com/forums/viewtopic.php?f=35&t=14613

I think the bulk rules this choice out. It will say Porsche on the valve covers but will cost you more than Ford or Chevy to get it running. Some of the cost might be a car that is much larger or doesn't have the foot space you need etc.

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PostPosted: July 22, 2018, 6:03 pm 
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If you haven't seen it, Chris did a build with a 924 transaxle: viewtopic.php?f=35&t=13200

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PostPosted: July 23, 2018, 9:30 am 
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lunarzonker wrote:
Thanks for the input! Why do you think a rear (and presumably separate) sub-frame should be used?


The Book chassis was designed with a live rear axle in mind. Therefore, using an IRS rear suspension will require some re-engineering at the back of the chassis to accept the Porsche transaxle and whatever suspension design you use, including adapting the Porsche design.

As you're discovering, there would be significant work involved in adapting the 928 setup. I'm not one to discourage anyone from their creating their Locost dream. That said, now is the right time to really think about what's important to you in building your car. If using the 928 drive line is the motivator, then go for it. However, if your core desire is to have a car completed and running quickly, you may want to trade the 928 equipment for a donor that's been done many times before like an older Mazda Miata. You can focus on actually building, not designing, which will be required in the 928 case.

It's up to you. You get to choose. It's your vision.

Cheers,

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Damn! That front slip angle is way too large and the Ackerman is just a muddle.

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


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PostPosted: July 23, 2018, 11:48 am 
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So I'm thinking the Porsche engine is a bust.
That said, the 928 torque tube, trans axle and rear irc and front hubs are certainly use-able and adaptable. While I'm no fan of Renegade, it appears as if they have a sbc conversion to the 928 running gear and it's seems quite inexpensive. Also, I happen to have several sbc laying around....The sbc being 20X20" would be an easier fit and parts are certainly cheaper. The trans axle should be good up to 400HP I should think.
Mulling it over.
I looked at the thread using the 924 (or was it 944) trans axle and sadly the thread was short on how it was done, but it did seem do able as they are similar.


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PostPosted: July 23, 2018, 6:51 pm 
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I wonder if a Haynes frame would be better. Cursory examination of what's available online seems to indicate a frame more robust than a 442E (more triangulation and already designed for independent rear susp.).
I can't seem to find any plans online though for me to closely examine. Are their none (online?)


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PostPosted: July 23, 2018, 6:56 pm 
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I've got the book. What would you like to know?

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PostPosted: July 23, 2018, 6:59 pm 
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ngpmike wrote:
I've got the book. What would you like to know?


Engine bay dimensions?
And your opinion the robustness when it comes to a possible sbc base (using the 928 running gear)?
Thank you very much for the help :-)


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PostPosted: July 23, 2018, 9:41 pm 
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Engine bay dimensions?
And your opinion the robustness when it comes to a possible sbc base (using the 928 running gear)?
Thank you very much for the help :-)[/quote]

You may want to take a look at Sorley,s 7 +442 below
http://sevenesque.com/plans/

and this
http://www.virtualv8.com/chassis3.htm

My own view would be to follow the Australian suggestions to add more tubes, but in addition I would make the upper and lower rails 1.25 inch tuves. The suspension tube components would also be heavier :)


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