New Technology!

Porsche patents a variable-compression-ratio engine to boost power and fuel efficiency;

http://www.extremetech.com/extreme/2045 ... efficiency

We hope this report is more, um reliable than some of the other webpages linked to there !
Alien fossils in meteorites, supersonic submarines, teleportation, cold fusion, just to name a few....

As kids we had a little miniature aero diesel engine with variable compression.
Although, obviously, it had to be be set pre flight...
And patents for similar go back almost into the stone age, so it will be interesting to see what happens to this one.

I wouldn’t disagree; there have been chain operated balancers on the crankshaft on the Honda’s 250 and 400 Superdream, it remains to be seen if they work over the lifetime of an engine :shock:

Balance shafts are around in rather a lot of engines these days,
some of them through several generations now.
Someone might have noticed if there was a problem !?

There are also some reports of owners trying them with the balancers not connected.
(As you would expect from motorcycle owners.)
Since they are generally aimed at taking out the high end tingles,
removing them is not altogether an improvement.......

That Kawa DOHC 650cc twin ER6 thingy that is powering quite a number of TT bikes in that class has a pair (?) of balance shafts,
be interesting to know if they were retained for TT duties ?
Not that they are chain driven...

If the crank is out of balance enough to damage the cases at high revs, how do chain driven balance shafts stop that from happening ?

acotrel said:

If the crank is out of balance enough to damage the cases at high revs, how do chain driven balance shafts stop that from happening ?

Click to expand...

if you are referring to the Honda 250/400 Superdream; You need to study the technology of how Honda did it, the engine revved higher than the Norton twin and when the chain wore, you could take the timing cover off and adjust the tension by turning the balance weight & tighten the chain on a spline, simple :!: :shock:

acotrel said:

If the crank is out of balance enough to damage the cases at high revs, how do chain driven balance shafts stop that from happening ?

Click to expand...

If the engine is so badly built and balanced that it can 'damage the cases', the designer needs a good kick up the kyber, and a new sheet of paper.
BF in an engine is only to give the rider a smooth ride - since the many out-of-balance forces can sum to zero.
ALL OF THEM, AND EACH OF THEM are still stressing the cases though, and each needs to be designed strong enough to survive this.

You still don't seem to have twigged to this simple aspect of engine design, Alan ?

Heck, a concrete truck can survive all of the concrete lumping to one side, although the driver will sure notice this.
If it was only built to survive in smooth mode, they'd be all busted and gone out of business, centuries ago....