13 replies to this topic

[Almag]

The Hartley H1 V8 was shown at Carlisle a few weeks ago. It's a 2.8L, 400 hp, 245 lb-ft, 10,000 rpm redline-having 75-degree flat-plane V8. Sort of a latter day Cossie DFV.

Hartley integrates the cylinders and heads from two Suzuki Hayabusa engines to a custom billet crankcase and cam drive. Click here for more images / history etc.





Does a flat-plane V8 need counterweights this large though? I thought flat plane V8s were balanced in the first order but not in the second, eliminating the need for full counterweighting. The counterweights on this crank look like those on a crossplane crank... can one of the balance gurus chime in?



The large gear on the back of the crank drives a 1:1 gear which itself has an integrated 2:1 reduction sprocket to drive the cams on one bank. This accomplishes the reverse rotation required by the "backward-facing" head without the need for custom ground cams.

[Powersteer]

Again, like the AJP8 designed by Al Melling, this engine has a 75 degree V8 and flat crank instead of a 90 degree vee angle. Why is this angle preffered? Compact?

[Greg Locock]

"Does a flat-plane V8 need counterweights this large though? I thought flat plane V8s were balanced in the first order but not in the second, eliminating the need for full counterweighting. The counterweights on this crank look like those on a crossplane crank... can one of the balance gurus chime in?"

Counterweighting is designed by looking a the crank stiffness, and bearing loads, and operating speeds. Basically a faster engine, with a more flexible crank, and tighter bearing clearances, will tend to need mmore counterweights.

All cranks are balanced in the first order if you choose to make them so.

The second order inertial forces from the crank and slider arrangement is what you are referring to, they can't be cancelled on a 75 degree crank, I /think/ the crossplane V8 90 degree crank cancels them, and i'm sur ethe flatplane V8 90 degree crank does not. Could be wrong about that.

"Why is this angle preffered? " I'll take a punt on packaging.

[Almag]

From the site:

"V angles down to 60 degrees were considered, but it quickly was recognized that the separate cylinders and straight intake tracts would eliminate very narrow angles. The decision was really between 75 and 72 degrees. It was decided that 72 degrees was too narrow because the metal in the top of the case between the cylinder banks was quickly disappearing as the V got smaller, not leaving much left to hold the top of the case together. A central oil galley is the most compact way to go and it would have been problematic with a 72 deg. angle. So 75 degrees it was going to be.

This proved to be a good decision as the top of the V in the case ended up being very tight with the cylinder skirts, oil jets and crank counter weight all in very close proximity."

[pio!pio!]

Whatever happened to the Radical V8 where they did the same thing w/ Hayabusa engines

[slon001]

I think the 75deg V angle is for packaging reasons only - 90 degree is prefered in order to completely provide the possibility eliminate primary reciprocating vibrations.

The large counterweights are to achieve this complete cancelation. As there are two rods per throw, and both throws either side of the centre main bearing are aligned in a 180 deg crank, an under balanced crank sees a larger bending moment, and transmits large forces to the main bearings (especially the centre bearing). I think this crank will still be under balanced from the theoretical ideal, it gets a bit hard to actually fit enough counterweight metal in there with a small bore spacing!. Of course heavy alloys are still a possibility.

It looks like he has a US patent for the gear / chain drive of the rear of the crankshaft. As far as I can see, PowerTec have used the same design on their engine, but I'm pretty sure PowerTec had their design done before Hartley - if so how is the patent valid?

Does anyone else have any thoughts here?

[GSX-R]

All flat-planes V8s have 2nd order vibration whatever their angle. When they use 90° angle, the vibration operates only in one plan (horizontal one, right<->left) and the firing is perfectly even (max smoothness). None of 90° V8s has 1 order vibration and without any counterweight.

The counterweights have the same function as on a I4 : limiting constrainst on the bearing and the crank itself.

The choise is certainly compactness for this. They're a lot of cases of non 90° for flatplane V8s or non 72° for V10s (M5 for instance).

[desmo]

That'd be just the thing for an updated Siata 208s-type roadster.

[zac510]

I wonder how many more of these V8s the market can take?

[J. Edlund]

Originally posted by Almag
Does a flat-plane V8 need counterweights this large though? I thought flat plane V8s were balanced in the first order but not in the second, eliminating the need for full counterweighting. The counterweights on this crank look like those on a crossplane crank... can one of the balance gurus chime in?

The counterweights are there in order to reduce stress on the crankshaft and bearings. The flat plane V8 i essentially two I4's working together. If we consier the engine to be an I4, we can se that the primary inertia forces are balanced, as cylinders 1 och 4 balances out the forces generated by cylinders 2 and 3. Because of that there is no need to use counterweghts due to balancing reasons. However, in most cases there are some sort of counterweight to, at least to some degree, compensate for the rotional mass, essentially crankpin + con rod big end, of each cylinder. Yes, this mass of cylinders 1 and 4 will be compensated by the same mass at cylinders 2 and 3 but not without introducing some bending loads on the crank. In the end there is a tradeoff between crankshaft mass and the need to reduce these bending loads on the crank. Engines like the DFV was "underbalanced"; the counterweights did not compensate completely for the rotational mass, this in order to keep the mass of the crankshaft low.

[Moon Tricky]

Originally posted by J. Edlund


The counterweights are there in order to reduce stress on the crankshaft and bearings. ...

So although it's balanced according to maths, in reality all the parts are not perfectly rigid so it's better to balance each bit individually if you can. That makes sense.

Has anybody ever made a W6 engine? It would be odd firing (unless it was a two-stroke), but then so are loads of engines.

[Almag]

As far as I can surmise, this Hartley is the third such commercially available bike-based V8. There's the RST (Mountune?) V8 and the Powertec V8 besides.

No clear picture on durability for any of them, other than a 30-hr rebuild interval for the Powertec (I've heard rumors of reliability issues but no particulars) and that the RST has gone some 30,000 miles in a Caterham, for what that's worth.

This one (Hartley) appears to be the most affordable of the three.

Regarding the patent aspect of the cam drive, perhaps there is some particular, discrete difference in execution that sets the Hartley apart from the Powertec? I'm unfamiliar with Powertec's cam drive approach unfortunately...

[ralt12]

"As far as I can surmise, this Hartley is the third such commercially available bike-based V8. There's the RST (Mountune?) V8 and the Powertec V8 besides."

There's also the Ian Drysdale V8, built for a bike, but there's been little published about it since his site's startup in the late '90's...
http://werple.net.au/~iwd/index.html

It does look like a nice little package, though.

[Twister]

I would be happy to play with anyone of them.
But I am sure I could not afford them!