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Learning how to build Lotus Seven replicas...together!
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PostPosted: September 16, 2010, 6:41 pm 
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gtivr4 wrote:
Why not just do a bike engine based V8 as mentioned, but make it smaller and cheaper (600cc based for example). Imagine a 1.2L V8 that is light, revs to the moon and has 200hp.

Oh. Oh, yes. Yes, please. Oh, can we? Can we please? I would LOVE doing one of those! :headbang:

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PostPosted: September 16, 2010, 8:05 pm 
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I would love to see an open source motorcycle based V8 (BEE? Bike-engined engine?)

However, the big hurdle for one of those is the crankshaft. I'm not sure what to do about that besides farm it out, and low volume custom forged crankshafts wouldn't be cheap.

Thinking realistically, how about designing a DOHC 4/5 valve head for the Suzuki G10? Maybe a block as well? 1 litre 3 cylinder engine, so very very light, and it could have a decent amount of power with some work to redesign it.

I like the idea of doing something like that better than trying to out-do Toyota on the 4AGE. I'm sure you could make some improvements on the 4AGE, but the effort/cost compared to the gain over a modified 4AGE wouldn't be worth it IMHO.


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PostPosted: September 16, 2010, 8:46 pm 
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firebat45 wrote:
However, the big hurdle for one of those is the crankshaft. I'm not sure what to do about that besides farm it out, and low volume custom forged crankshafts wouldn't be cheap.

Here's a question, then, for those better acquainted with engines than I: is a forged crankshaft necessary, or is it possible to get away with machining (and then, say, shot peening) one? We'd have to do at least one like that just for fit-and-finish, and for low-speed running to prove it out.

gtivr4 wrote:
I would also check into what racing classes could benefit from your motor (1.2L might be the perfect size for a specific racing class).

If that is indeed the case, we might get enough pre-orders to help out, or at least a sponsorship to be able to afford it... maybe?

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PostPosted: September 16, 2010, 8:58 pm 
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Right now I'm not worried about orders, just design.
Using the critical dimensions of a pre-existing engine would allow us the flexibility of using it's rotating/reciprocating components.
I'm not trying to outdo Toyota. They aren't the only 81x77 1.6L. They're very common dimensions.
using a Honda b as a base would allow 84x89mm 2.0L engines using readily available parts, but I feel it'd be too heavy.

The major disadvantage I see to lightness with the 4A is that its an iron block. Yes, its compact and light and thin-cast, but its still iron.


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PostPosted: September 16, 2010, 9:29 pm 
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Would Google sketchup be the easiest way to collaborate?
I guess the first thing we need to do is model the reciprocating assembly.


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PostPosted: September 16, 2010, 10:06 pm 
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killer_siller wrote:
Would Google sketchup be the easiest way to collaborate?

No. If there is only one CAD person, using 3D PDFs would be the best way to show everyone what's going on. Assuming more than one CAD jockey, we'd need a way to share native CAD files, shock I have to assume Google does not do.

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I guess the first thing we need to do is model the reciprocating assembly.

I'd disagree - we need to choose what we're doing first, and get a CLEAR statement of intent for the project, otherwise we'll be chasing out tails and getting nowhere. 1.2L V8? Honda-derived L6? Let's get consensus on what we're doing before we do it.

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PostPosted: September 16, 2010, 10:11 pm 
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Could build a crank the same way snowmobile and motorcycle engines are done. Several machined pieces pressed together. Then you could use roller main bearings too. Maybe that would make it possible to use motorcycle cylinder banks and heads, or cast your own block to use sportbike heads and internals. Not sure how practical it would be to weld a pair of blocks together, pretty sure I remember that it cost Ford $30,000 to do the engine for the GT-90.
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PostPosted: September 16, 2010, 11:07 pm 
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Right now the goal is to base it off of the Toyota 4A-GE, as I like its bore pitch and critical dimensions such as main bearing and crankpin sizes.
From there we can make a 2.4L L6, 3.2L V8 and 4.8L V12.
Though making a tiny V8 and then stuffing it into a Alfa 33 Stradale clone would be AWESOME.
I do intend on having a separate crankcase and cylinders, as well as a full girdle and wet sleeves. I'm also toying with the idea of throughbolts: the head bolts going through the block and also being the main bolts, like the Rover K series.
I'd like to use a symmetric cam carrier group, to allow a single head casting and cam carrier casting to be turned around. This would allow the switching of port sides on right/left hand drive vehicles, and one casting that could be used on right/left banks of V type engines.
Maybe a 1.2L L3 would be good for a Lotus 7.


Last edited by killer_siller on September 16, 2010, 11:17 pm, edited 1 time in total.

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PostPosted: September 16, 2010, 11:16 pm 
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Is it going to be turbo charged?


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PostPosted: September 16, 2010, 11:19 pm 
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flat4 wrote:
Is it going to be turbo charged?

I don't see why not. To be Motorsports competitive it'd almost need to be.

I'm kinda torn, as I'd like to see it scalable up to 86mm bore and 89mm stroke to make a 2.3L, but I don't like using that kind of bore pitch on a 1.6L, as it'd make it rather large.


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PostPosted: September 17, 2010, 12:28 am 
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killer_siller wrote:
flat4 wrote:
Is it going to be turbo charged?

I don't see why not. To be Motorsports competitive it'd almost need to be.

I'm kinda torn, as I'd like to see it scalable up to 86mm bore and 89mm stroke to make a 2.3L, but I don't like using that kind of bore pitch on a 1.6L, as it'd make it rather large.


cant wait to see version .0001! a napkin sketch will do.


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PostPosted: September 17, 2010, 9:59 am 
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killer_siller wrote:
Right now the goal is to base it off of the Toyota 4A-GE, as I like its bore pitch and critical dimensions such as main bearing and crankpin sizes.

What is to be gained off of doing that? If you like the Toyota 4A-GE, use it. There is no way we're going to come anywhere close to matching (let alone exceeding) what that engine is. If you like it, use it. If you're wanting to base an L3, L6, V6, V8, L8, etc., etc., off of it, I can see doing that... but trying to replicate an existing L4 just seems redundant and futile. Perhaps I'm not understanding the spirit of what you're proposing? I'd rather put the effort into something unique (like a 1.2L V8) than simply replicating what's already out there.

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PostPosted: September 17, 2010, 10:57 am 
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killer_siller wrote:
I'd like it to be designed in such a way that the block and head can be cut on a 3d printer out of foam and lost-foam cast.

Had a thought about that last night. Instead of doing lost foam casting, why not investment casting? Produce a wax version of the block (and head, if we're not going to use an existing head off of something), which is then used to make a ceramic mold. Much cleaner. Having worked in a foundry before I just don't have fond memories of sand used for casting. I think investment casting is much nicer. Plus, many 3D printers are already set up for wax, whereas if you were making something using lost foam you'd have to first CNC cut the foam, then assemble it. Using wax eliminates an intermediate step (and thereby some time and cost).

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PostPosted: September 17, 2010, 11:01 am 
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Using an engine's critical dimensions isn't so much recreating it. The 4A-GE, for example, shares bore, stroke, and even valve sizing with the Cosworth BDA. They are still very different engines.
The Nissan SR20, Honda K20, and Toyota 3S-GTE all share bore and stroke. Are they so similar?
I'm proposing using critical dimensions of an existing engine because there are things I like about it. There are yet things I don't like: the block doesn't do much to support the main bearings, there are some oiling issues, and its cast iron.
I'd like to integrate dry-sump oiling into my design, as well as an electric water pump.
Once the ground work is laid, the flexibility can become apparent. Different combustion chambers, induction forms, drivetrain layouts, directions of rotation, and cylinder counts and orientations can all be had with simple changes to the design. The more that is done, the more that is possible.


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PostPosted: September 17, 2010, 11:30 am 
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OK, I get it now. You have a dimensional skeleton you'd like to build off, but otherwise it's a clean sheet.

Now that we've cleared that up (don't worry, I learn pretty quickly once my stupid questions are answered :wink: ), are you thinking going totally clean sheet, or re-using some existing parts available on the market (like crankshaft, con rods - all the stuff that's made using manufacturing techniques harder than just plain old machining or casting)? Do you have some goals in mind, be they power, torque, redline, or the like?

If you can put together a summary of the overall dimensional skeleton, I can whip up a model pretty quickly on Monday (not at work today, no SW at home).

This topic thread may be a good place to start, but we're going to quickly need a bigger repository for our data. I see +EM already uses Google Docs for a lot of data... maybe that would be a good place to start. Then we'd just have to figure out how to share CAD data.

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