ESE's works engine tuner

[philou]

The document speaks of a variable balancing crankshaft

In the different holes, it is possible to insert aluminum, steel, tungsten, ... to easily vary the balancing.

By the calculation have chosen a balancing factor, and by test of the motor, can change the factor by changing the inserts

[TZ350]

By the calculation have chosen a balancing factor, and by test of the motor, can change the factor by changing the inserts

Thanks Philou, calculate then test, it is the only practical way to arrive at a balance factor that works properly with any engine, frame, suspension combination. Great to see the crank.

[wobbly]

The pic that has been identified as one of Jans Aprilias,shows the lengths gone to to increase inertia dramatically.
Where I have marked X, these two inserts appear to be identical to the others, but contribute nothing to balance .
If anything they look to be above the centerline, so in effect are partially unbalancing the assembly,but as they are opposite each other all they
are doing is increasing mass and inertia.
My take on the effect is two fold.
Firstly,the high inertia would reduce the rotational speed drop off when speedshifting at WOT using ignition cut.
Secondly the high inertia would reduce the in cycle speed variation around BDC, where gas pressure above the piston is non existent.
No force = no acceleration = less instantaneous rpm.
But this is counter intuitive , because if you allow the crank to slow down more , around BDC , then this in effect will increase the STA of the transfers as the lower rotational
speed = more open time with the same static timings.

[jbiplane]

Couple of videos of 294cc boxer engine with carburetor and new type of exhaust

[husaberg]

The pic that has been identified as one of Jans Aprilias,shows the lengths gone to to increase inertia dramatically.
Where I have marked X, these two inserts appear to be identical to the others, but contribute nothing to balance .
If anything they look to be above the centerline, so in effect are partially unbalancing the assembly,but as they are opposite each other all they
are doing is increasing mass and inertia.
My take on the effect is two fold.
Firstly,the high inertia would reduce the rotational speed drop off when speedshifting at WOT using ignition cut.
Secondly the high inertia would reduce the in cycle speed variation around BDC, where gas pressure above the piston is non existent.
No force = no acceleration = less instantaneous rpm.
But this is counter intuitive , because if you allow the crank to slow down more , around BDC , then this in effect will increase the STA of the transfers as the lower rotational
speed = more open time with the same static timings.

I only identified it as "Jans era" I have long forgotten where I found it. or if its from a twin or a single but I posted it for its clean inside profile. (Edit looking through the albulm it seems to be a single judging by the balance shaft drive gear)

I think the twins would be balanced to a higher balance factor maybe even 100% this could be one of these. Okay its not but here are some anyway.

I think the added weight allows the crank to be made cleaner on the insides whist maintaining the inertia that a porkchop design would have had.

Frits has posted and commented previously on later post Jan RSA cranks where they packed the insides to increase primary compression and noted they were never as fast.
This I think is one of them. I think it came from the frits file? Maybe Frits or Jan would like to comment seeing as they know the answers.

I believe aprilia may have later also changed the balance shaft design back to a pork chop design.

I do know this is a RSA125 crankshaft. and if you look closely its porkchoped.

Whats your take on my theory on the progressive loss of over rev as the Honda NSR500 went from four even spaced 90 degrees firing (first NSR500's spencer era)
To 180 like a twin(ie two up like a Yamaha yzr500 commonly referred to as the screamer)
To big bang firing all cylinders within 68 degrees more like a single.
Because it seems even if one accounts for engine spec difference, it seems anecdotally at least, that each time they made changes to make the firing less evenly and closer spaced, they actually lost over rev potential.

[jamathi]

The pic that has been identified as one of Jans Aprilias,shows the lengths gone to to increase inertia dramatically.
Where I have marked X, these two inserts appear to be identical to the others, but contribute nothing to balance .
If anything they look to be above the centerline, so in effect are partially unbalancing the assembly,but as they are opposite each other all they
are doing is increasing mass and inertia.
My take on the effect is two fold.
Firstly,the high inertia would reduce the rotational speed drop off when speedshifting at WOT using ignition cut.
Secondly the high inertia would reduce the in cycle speed variation around BDC, where gas pressure above the piston is non existent.
No force = no acceleration = less instantaneous rpm.
But this is counter intuitive , because if you allow the crank to slow down more , around BDC , then this in effect will increase the STA of the transfers as the lower rotational
speed = more open time with the same static timings.

This kind of thing was tested on-track.
It seemed to give more traction.

[philou]

Great stuff, I hope. But I was born on a remote island in the Pacific and it never occurrd to me that there would be any benefit to learning another language being that Europe was 60 million miles away.
Or something like that. French class I only learnt how to ask the time. Not how to understand the answer.

for me the most difficult messages to translate are those of wobbly

Thanks Philou, calculate then test, it is the only practical way to arrive at a balance factor that works properly with any engine, frame, suspension combination. Great to see the crank.

The idea of the manufacturer and sell a crankshaft with holes and inserts with to do what we want

The manufacturer also indicates :

"These interchangeable inserts have the possibility of varying the balancing at will according to the available alternative mass; or depending on the type of return the preparer wants to get.

The system of these 3 holes allows in practice to have more settings on crankshafts to develop the engine with a so-called pre-established delivery or at least to obtain a certain supply.
For example, dropping the crankshaft forward as the direction of rotation of the engine tends to favor high rotational speeds, while dropping the shaft in the opposite direction of rotation, like most engine shafts. original series from scooters low-speed delivery is favored, improving the initial thrust."

[TZ350]

.
Looks to be very useful and a clever idea, top quality.

[TZ350]

Couple of videos of 294cc boxer engine with carburetor and new type of exhaust

..... great to hear it running, sounds very quiet.

[Greg85]

Thanks everyone for all the very interesting info about crankshaft balancing 👍👍

[husaberg]

Thanks everyone for all the very interesting info about crankshaft balancing ����

I found this below on the net and it saved me having to scan it again.
whilst most of this was written perhaps 60 plus years ago some of the tricks are still relevant in the book.


the whole book is scanned here.
http://tuningforspeed.com/files/Tuning_for_Speed.pdf

[philou]

balancing factor 60% seems used for riders comfort

I find 45 to 50% on crankshaft "racing" (not balancing shaft) more vibration but less crankshaft stress ?

I am curious to anticipate or retard the balancing mass as proposed by the ialien

[Muhr]

two-wheeled vehicles tend to handle horizontal forces better then vertical. where off the cylinder position is crucial for seting up a balance factor.

[philou]

horizontal force less tiring for the pilot.

Vertical force = jackhammer

[Frits Overmars]

the high inertia would reduce the in cycle speed variation around BDC, where gas pressure above the piston is non existent. No force = no acceleration = less instantaneous rpm.
But this is counter intuitive , because if you allow the crank to slow down more , around BDC , then this in effect will increase the STA of the transfers as the lower rotational speed = more open time with the same static timings.

No force = no acceleration; right. But as the piston is approaching BDC there is as lot of force, not from the non-existent gas pressure, but from all the reciprocating parts that try to keep moving towards the centre of the earth.
Before BDC that force is accelerating the crankshaft rpm; after BDC it is slowing down the crankshaft rpm. So what is the nett gain in transfer time.area?

I think the twins would be balanced to a higher balance factor maybe even 100%. this could be one of these.

Are you referring to your first or your second picture Husa? Your first picture does not show an Aprilia V-twin (or W-twin if you like) crank; your second picture does.
The inserts give the twin-cranks a distinct asymmetrical appearance because the resultant of the inserts' forces must be at a 45° angle to the crankpin position.

I think the added weight allows the crank to be made cleaner on the insides whist maintaining the inertia that a porkchop design would have had.

Correct.

Frits has posted and commented previously on later post-Jan RSA cranks where they packed the insides to increase primary compression and noted they were never as fast.

Yes, after Jan retired, some geniuses in the racing department seized the opportunity to 'correct Jan's mistakes'. They packed the insides and then wondered why a 2008-RSA was slower than a 2006-RSA...

I believe aprilia may have later also changed the balance shaft design back to a pork chop design.

The original left-side balance mass was a full aluminium disk with mallory inserts. The geniuses changed it into a triangle, saving a tiny bit of weight and increasing its air windage losses (luckily the left-side balance mass did not run in oil).