Alfadan conrods

[J.A.W.]

AlfaDan's "BIG SECRET" is skotch yokes replacing the con rods. (Not a new idea - its hundreds of years old.) This eliminates 2nd order imbalance which Alfadan erroneously claims is the factor which limits cylinder size in inline fours. This concept is doomed to failure.
https://patents.google.com/patent/US103 ... US10378578

Looks like a neat concept actually. Can you tell us why it's doomed? The large sliding surface area robs power/heats up/deflects? Can you please be more specific?

In this case the "idea" seems to be based on the premise that 4 cyl engine displacement is limited by secondary imbalance and Alfadan has a mechanical solution. The reality is that secondary imbalance is easily cancelled with balance shafts and the real limits are mainly inertia torque and the fact that thermal efficiency for SI engines peaks around 300 cc/cylinder (this has probably increased since Taylor's time) and falls steadily as cylinder size grows.

Many have tried to implement the Scotch Yoke in piston engines - and failed. Lots of issues with strength, lubrication etc and at the end of the day there is no real benefit.

Good investigative effort/technical summary there gg, esp' since the BMEP figures appear startling
for an N/A 4T mill of such B X S dimensions - & moderate rpm - 'Freevalve' technology notwithstanding.

Makes one wonder why Halfdone, ah sorry, I mean Alfadan, are so reticent about their 'scotch egg',
no, that's not it, 'golden egg' (yeah that's better, even if still a tad 'Eldorado/Lassiter's reef') reveal...

[Hoffman900]

A torsional damper and /or a counter balancer are way more efficient if a design to mitigate harmonics.

Really, the biggest issue, other than your engine being parked at the rpm the harmonica occur, is the valvetrain.

As gruntguru said, thermal efficiency peaks around 300cc +/ - . Secondary imbalances are not an issue in anything… it’s all about flame speed, which is why Ducati is going the other way with bore size and more cylinders, at some point you hit an efficiency wall where the lower efficiency is overcome by the increase in mechanical frictional forces, and then it’s a downhill battle.

[Jolle]

This project feels like a investment hoax. We have these from time till time with monorails or other "new old inventions".

Even is it's now possible to build a (very) large inline 4... why?