ESE's works engine tuner

[jbiplane]

Hi folks. I saw somitimes on pictures here 3 cylinder engines where 2 cylinders oriented to the top and medium cylinder to bottom.
How looks crankshaft for this engines? Angles, firing order?

[Frits Overmars]

Hi folks. I saw somitimes on pictures here 3 cylinder engines where 2 cylinders oriented to the top and medium cylinder to bottom. How looks crankshaft for this engines? Angles, firing order?

Here you go Valery.

[jbiplane]

Here you go Valery

Thanks you very much Frits! You are real 2-stroke wikipedia
Why they move second crankpin position by 8 degree? Cylinders count from front to back and angle cylinder to cylinder 120 and 0 degree?
I saw Honda MVX250F crank in internet. They make a dit different way

Below Soviet engine from 1960
3x116cc bore 54 stroke 52

Cylinder to cylinder angle is 55 degree. On crankshaft second pin ofsetted 65 degree, third 120

By the way I saw here drawings of JBB V90 crankshaft.
I estimating my abilities to make 3cylinder star with 3 individual crakcase chamber.
May be exist picture with a bit better resolution to beter see dimensions. Could be usefull.

[Frits Overmars]

The crankshaft you posted is from the Honda three-cylinder street bike with its outer cylinders firing simultaneously. Note the fat con rod and the massive piston pin in the center cylinder, necessary for balancing.
Below is the JBB V90 crankshaft. I agree it's not very clear but it's the best I have.

[jbiplane]

Great Frits. I proceed your picture with artifical intelect software. Seems now more easy to work with.

[Frits Overmars]

That's great too, Valery

[wobbly]

When I was designing the BSL500 engine , I supervised a PhD project for one of my engineers to do a balance project for the V3 we had decided upon.

He wrote a code to analyze the probably 50 firing order and phasing/ Vee angle variations I gave him that were physically possible, to optimize both balance forces and rotational inertia.
The final version fired cylinders 1&2 together with cylinder 3 @ 120* later , phased at 120*, and included a balance shaft across 1 & 3.
This was driven of a 1:1 gear pair between 2 cylinders , and drove the clutch off one end and the ignition rotor off the other.

It had zero primary out of balance and was as smooth as a Tesla - much to KR Seniors annoyance when he grabbed the throttle off me in the pit lane
and announced to his team " why cant you dumb fuckers do balance like these guys".

Some time later a gave the App to Jimmy Steadman who had built a Tripple that vibrated your hands off the bars , and he used it with some success in reducing the out of balance with no added shaft to help.
I had the App on an old hard drive - but doubt I could find it.
I will contact Buckley Systems and see if its still on one of the servers.

[Flettner]

According to Irving, it was to avoid a single concentration of heat source. But he also points out the badly cooled area between the ports.

I liked riding the twin-port motocrossers. A couple of friends had them and I'd borrow one for "visitors races". Which are now a thing of the past.

So water cooling would be very desirable, bridge cooled right up to the cylinders edge.
With my AG, it has an unusual power spread, almost two powerbands. Low end is relitively strong up to about 6000 ish, enough to do an entire Vinduro without reving any harder. But from there to 7500 it goes very flat, after that its all on.
I thinking a powervalve will fix this early pipe wave return thats buggering everything up. The high, square exhaust port that spans about 170 degrees of the the cylinder produces a strong wave.
Its a rubbish 58 x 48
195 exhaust, 130 transfers.
No exhaust dam but the next cylinder will have.

[jato]

The crank with #2 displaced 8 degrees i believe is from an RS 500 that had a V angle of 112 degrees - giving the engine an even 120 firing interval. those MVX cranks are configured to (nearly) replicate a 90 degree V twin with the outer cylinders being (nearly again) balanced by the heavy centre cylinder. at one point i weighed all the parts and did some calculations to see it was close to being balanced, but at the cost of the engineering compromises of that heavy centre cylinder

[wobbly]

Yea , the MXV had a HUGE rod and piston mass on the center cylinder - it worked , but effin ugly engineering.
It also had the outer cylinders out of phase slightly , I thought so the the primary drive wasnt stressed on the same one pair of gear teeth, each revolution.
Honda has had some super clever dudes who seem to know alot more than the average Japanese sewing machine designer graduates , the V5 in Moto GP was absolute genius.

[Grumph]

DKW were there first in the early 50's with a 350/3 noted for it's smooth running.
75degree angle between the upright outers and prone inner cylinders

120 degree firing intervals - initially to suit the mag used at the beginning.

The outer crankpins are at 120 degrees to each other.
The middle pin is 45 degrees out of phase with the right hand side pin.

[husaberg]

Compares the MVX the NS500 and the DKW

[jato]

I guess the DKW has relatively small forces at play with 115 cc a cylinder, but it surprises me it was smooth. the 750 V3 was originally assembled with a 120 degree firing interval (no balance shaft) and while it sounded nice and went really well, as wobbly mentions the vibrations were wild, with the top triple clamp becoming a blur beyond 8 or 9 000 rpm. from memory each crankpin was transferring 12000 newtons of force at full revs. the crank was then re-arranged to have the primary forces at 120 degree and it became somewhat raceworthy with quite a decent rocking couple across the engine. during design provision was made for a partial length balance shaft (from #1 to between #2 and #3) so next that was installed and it improved things more but the lesson is that size V3 engine really needs a full length balance shaft.

[Grumph]

Vic Willougby describes the DKW as "turbine smooth" when he rode it.

He was told it was safe to 15000rpm - but peak power was 10500rpm.

[Flettner]

Wobbly, estimate, at 55 stroke would you give a 3mm exhaust dam? Or less?