I had a motorcycle based V8 idea...

[aspetuck]

Let me preface by noting that while I am serious and would appreciate replies, I don't really know what I'm doing from an engineering perspective. Really I'm hoping this will spark an interesting discussion although depending on how feasible and expensive (let alone possible) it is I would potentially consider trying this as a serious project.

Many of you have probably seen motorcycle derived V8 engines such as the Hartley V8 in the Ariel Atom 500. I have noticed that all of them I've seen have been designed from inline 4s, pretty much always the Hayabusa engine. Someone posted on this forum at one point asking about how difficult it would be to make one; the answer seems to be very difficult.

http://www.f1technical.net/forum/viewto ... =11&t=9264

Anyway, what I got out of it (correct me if I'm wrong) is that you would need to design and build a new crankshaft and crankcase, which would be very expensive. I then read an article about a V12 build out of a Chevy LS engine. They seemed to actually weld the blocks and crankshafts together, although it seems like you'd be better off forging them. I could be totally, horribly wrong but it seems to me that you could do the same thing with a V/Flat 4 or 6 for less than starting with an inline unit. Am I horribly wrong?

Another example would be the Aston V12, which is supposedly two Ford Duratec V6s and the SHO V8 which was rumored to be at least loosely based on the V6 also.

Aprilia makes a 1 liter V4 for the RSV4. Basically I was wondering if it would be possible to combine two of these (figuratively, perhaps) into a 2 liter V8?

[flynfrog]

with enough money and time anything is possible.

[Lycoming]

with enough money and time anything is possible.

Give a man a file, a block of aluminum and some drawings and measuring tools, lock him in a workshop and check back in 100 years. You'll find yourself a perfectly made engine block.

Anyway, what I got out of it (correct me if I'm wrong) is that you would need to design and build a new crankshaft and crankcase, which would be very expensive.

Pretty much.

They seemed to actually weld the blocks and crankshafts together, although it seems like you'd be better off forging them.

The crankshaft absolutely would be better off if you machined it from a forging. It would be very difficult and require significant modification to make it work like that. If the engine gets as far as actually running, I can just about guarantee you that if you just butt weld 2 cranks together, it will fail.

The block may be doable, but if it's aluminum, and especially if it's a heat treated aluminum (which almost all aluminum used in structural applications is), then that is also almost certain to fail.

I could be totally, horribly wrong but it seems to me that you could do the same thing with a V/Flat 4 or 6 for less than starting with an inline unit. Am I horribly wrong?

The idea with that is that you use the cylinders and cylinder heads from the inlines, and then do everything below that custom. It would probably be cheaper, yes, to just weld two V4 or V6 engines end to end, but I can't see that working without a lot of modifications. At that point, you probably haven't saved yourself any money or time.

Why do you want to make this franken-engine anyways? If you just want more power, boring/stroking + a turbo would probably by easier, cheaper and more reliable, especially if you have no engineering knowledge.

[Tommy Cookers]

electron-beam welding will do anything
make sure the workpiece is well demagmetised or the beam won't go where it is pointed

[bdr529]

Radical Performance Engines, they make a V8 out of 2 Suzuki GSX-R Hayabusa cylinder heads, and a new crankcase.
http://www.radicalperformanceengines.co ... oblock-v8/.
I think it might be easier to let someone else build the crankcase, I'm sure their not cheep, but you know it will go.

[thisisatest]

the benefit i see of using a v4 is that the valves would likely have the correct orientation. problem with the Hayabusa is that the intakes are all on one side (let's call it left) with the exhausts on the right. you would typically want the intakes facing inside the V, exhausts out. so you have to sort that out.
the one solution from starting with a v4 opens up a lot more problems, though. the heads wouldnt work, the cams would only go halfway down the block, you would basically be tossing a lot more of the parts.

[andylaurence]

Ignoring the structural issues of welding two blocks together, what you'd end up with is 4 heads, 4 cam chains, 8 cams, etc. The RPE/Hartley solution works well because the crank case is separate from the block, so a large number of original parts from the Hayabusa(s) can be used. You end up with 2 heads, 2 cam chains, 4 cams, etc. It's therefore lighter, more reliable and produces more power. The concept was to produce an engine that can rival an old F1 engine in performance terms (bear in mind that clubman drivers won't use the full revs of an F1 engine) yet with running costs of a couple of bike engines. I think Radical warranty theirs for 40 hours...

[tok-tokkie]

Using the cylinder heads & cylinders of an existing engine (which is the idea since the heads are the really intricate bit) means the pitch of the pistons is fixed. That means you can use the existing crankshaft. It also means that a new crankshaft can be very little different from the existing crankshaft. What is needed is new con rods. They need to be like those used on radial aircraft engines. Just one con rod = master rod = has a big end journal. The other rod is attached to the master rod rather like the small end. There is not much angular movement at this second joint. There is hardly any difference in the loading on the big end bearing since the power strokes of the two cylinders are about 270° apart. There is no lateral offset of the 2 banks of cylinders.

A new crankcase is required which is not complicated if the gearbox is similar to a Harley where it is a separate unit. Here is a video of an inline 4 cylinder monkey bike where you can see the very simple crankcase attached to the original gearbox. http://www.youtube.com/watch?v=_equBvpVMRo

[autogyro]

http://fr.wikipedia.org/wiki/Alfa_Romeo_16C_Bi-moteur

You could always build a car on the lines of the 1935/6 Alpha Bi Moteur.
That had two strait eight engines one in the front and one in the back, a gearbox in the middle and two drive shafts one to each rear wheel.
No need to join the engines together and perfect weight distribution.

[langwadt]

the benefit i see of using a v4 is that the valves would likely have the correct orientation. problem with the Hayabusa is that the intakes are all on one side (let's call it left) with the exhausts on the right. you would typically want the intakes facing inside the V, exhausts out. so you have to sort that out.

you just flip one of the heads, but that means you need a cam drive at both ends of the engine one of them in reverse.
I believe Radical has a patent on a way to do it

[aspetuck]

Thank you for clearing this up, all of this makes more sense now. Does anyone have the rough cost of developing either a crankcase or head?

[bdr529]

Thank you for clearing this up, all of this makes more sense now. Does anyone have the rough cost of developing either a crankcase or head?

You never mentioned what type of car you want to put this motor in ?

[aspetuck]

My goal is to design a mid engined track car, sort of like a more powerful F1000 or Formula BMW

[aspetuck]

If that doesn't materialize, perhaps a "locost 7" or mid engined classic mini

[Lycoming]

Thank you for clearing this up, all of this makes more sense now. Does anyone have the rough cost of developing either a crankcase or head?

very roughly, it will probably be at least in the low to mid thousands. And if you pay somebody to do the engineering for you, it will be much much more than that.

My goal is to design a mid engined track car, sort of like a more powerful F1000 or Formula BMW

Why not just use a 1000cc bike engine or something along those lines? What is the advantage of a franken-v8? ever heard of the western washington v8?