Oddball engines and prototypes

[WilDun]

Same-same, 'cept the Fath crank was a built-up rolling element bearing item, like most 2Ts, Z1s, GS Suzukis & whatnot..
& a bit like the TZ 750, effectively being paired twin cranks running a jackshaft.. ( wonder why Yam didn't run the 90`option on the TZ, instead of firing in pairs?)

4T 90`inline crank configuraton "sounds interesting" - just like a 4T V4, as the Yamahas do.

I vaguely remember some guy who tried to tame one of the big British Twins with a 90deg crank - Triumph? Beeza? I dunno, - he may have managed that to some degree, (no pun intended).
Can't really Google that till I've got a name to punch in! Maybe I'll find it tonight ie if someone else hasn't already found it.
Smoko's over , back to the garage to tidy up before 'someone' get's back.

[J.A.W.]

Irving ( Vincent/Repco engineer) suggested it in his classic treatise many decades ago..

Yamaha started selling it in production big vertical twins ~20 years ago.. & both Triumph & new Norton do it in their lumps..

Cammed 4Ts require valve re-timing too, natch..

BMW however, keep their 800 vertical twin at 360`& use another 'virtual 3rd' recip element for balance control..

Funny thing is, you can manipulate XS 650 built-up rolling element cranks to ( near) that staggered configuration too,
- but the 90`V-twin & 180`flat-twin cranks run 360` pin arrangements..

[WilDun]

Irving ( Vincent/Repco engineer) suggested it in his classic treatise many decades ago..
BMW however, keep their 800 vertical twin at 360`& use another 'virtual 3rd' recip element for balance control..

Irving was a very clever man!
Didn't Doug Hele propose that idea for Triumph? - he worked for the wrong company I reckon.
Think that type of arrangement may have been discussed before in Husa's other thread, on old bikes of the sixties.

I liked the sixties road going Honda 180 deg cranks, that arrangement makes for a pleasant sound and the Hondas didn't seem to have any problems with vibration from the "rocking" motion - sort of unique sound you don't hear anymore.

[J.A.W.]

Honda made vertical twins ( & V4s) with both 180`& 360` cranks..
360' firing is much more pleasant, both for feel, & sound..
(& 'bout even for vibes, although different - in felt sensation) for 4Ts -in my experience

Current Honda vertical twins run offset cranks ( as previously mentioned),
- but Kawasaki still do the nasty busy-buzzy feeling old 180`set-up,
& the BMW solution feels/sounds best, IMO..

Although, for sure - cranks that feature 120`multiples of three, are even better..

[husaberg]

Irving ( Vincent/Repco engineer) suggested it in his classic treatise many decades ago..

Yamaha started selling it in production big vertical twins ~20 years ago.. & both Triumph & new Norton do it in their lumps..

Cammed 4Ts require valve re-timing too, natch..

BMW however, keep their 800 vertical twin at 360`& use another 'virtual 3rd' recip element for balance control..

Funny thing is, you can manipulate XS 650 built-up rolling element cranks to ( near) that staggered configuration too,
- but the 90`V-twin & 180`flat-twin cranks rum 360` pin arrangements..

Irvings pick was 76 degrees. From memory it was something to do with the other piston being at max velocity
I have posted the whys in th eese thread years ago the jury's out on whether it is better than 90 degrees, but both are far better than 360.
Quite a few bit twins have been rejigged to both.

[J.A.W.]

"Better"?

For making a cheap pseudo-V-twin, maybe..

I like the feel & aural 'blatt' of a decently crisp, well tuned/fettled old-school Commando with pea-shooters,
& it sure delivers a "better" ride - IMO ( & by the performance figures), than a current porky-type faux V-twin Bonnie..

http://www.classicbike.biz/Norton/Ma...onMC-World.pdf

To get a 12.75 @ 105mph 1/4 mile - from a current Bonnie - is a tad spendy..

[husaberg]

"Better"?

For making a cheap pseudo-V-twin, maybe..

I like the feel & aural 'blatt' of a decently crisp, well tuned/fettled old-school Commando with pea-shooters,
& it sure delivers a "better" ride - IMO ( & by the performance figures), than a current porky-type faux V-twin Bonnie..

http://www.classicbike.biz/Norton/Ma...onMC-World.pdf

To get a 12.75 @ 105mph 1/4 mile - from a current Bonnie - is a tad spendy..

Smoother less likely to shake itself to pieces and not need rubbers to isolate vibes. better drive too as well as lovely offbeat growl.
I think energy spent shaking stuff up and down could be better used to spin stuff round and round.( this is a bit of Jan and Frits paraphrased)

[Frits Overmars]

Not unique to Austrians, the anglo saxons were pretty good at it too. Butcher, Baker, Tanner, Driver, Shepherd come to mind.

You forgot Miller. How could you forget Miller?
(Müller is the most frequent family name in Germany).
"Good evening Sir. Did you make reservations?" "Yes, name of Müller"

[J.A.W.]

Smoother less likely to shake itself to pieces and not need rubbers to isolate vibes. better drive too as well as lovely offbeat growl.
I think energy spent shaking stuff up and down could be better used to spin stuff round and round.( this is a bit of Jan and Frits paraphrased)

Doesn't matter for a cruiser mate.. its the feel at that level of performance, the balance shafts & other needless pork stifles even that..

Commando is lighter & has a cammy kick out, on top of the long-stroke torque thrust.. get a go on one, you'll know then..

[husaberg]

Doesn't matter for a cruiser mate.. its the feel at that level of performance, the balance shafts & other needless pork stifles even that..

Commando is lighter & has a cammy kick out, on top of the long-stroke torque thrust.. get a go on one, you'll know then..

IF it is at 90 or 76 it won't need a balance shaft to have tolerable vibes. or prophylactic mounts

[Frits Overmars]

Does anyone remember Helmut Fath and his four cylinder engine...

Helmut did not do just the one.
After he had become sidecar world champion with a BMW, he had some difficulties in making BMW listen to his wishes, so he built the 500-4 URS engine, a four-stroke with a number of novel ideas like the 90°-cranks, the split inlet tracts and the Kugelfischer fuel injection.
Later in life he saw the light and built a 500-4 two-stroke boxer with four rotary inlet discs; two contra-rotating discs stacked above one another for each pair of cylinders, so the inlet ports would open twice as fast. And finally he built a 250-2 boxer, the HF3.

[J.A.W.]

IF it is at 90 or 76 it won't need a balance shaft to have tolerable vibes. or prophylactic mounts

Yet.. they do.. have balance shafts..& are built massively heavy around them..

A well set up Commando also derives a positive heeled over handling feel - from that resilient rubber - too, oddly enough..

[husaberg]

Yet.. they do.. have balance shafts..& are built massively heavy around them..

A well set up Commando also derives a positive heeled over handling feel - from that resilient rubber - too, oddly enough..

As long as they are shimmed right.
WHat I am saying is there has been plenty of old brits converted to 76 and 90 cranks Nourish and SRM used to sell them. plenty of others have done it DIY on all sorts of engines.

[J.A.W.]

As long as they are shimmed right.
WHat I am saying is there has been plenty of old brits converted to 76 and 90 cranks Nourish and SRM used to sell them. plenty of others have done it DIY on all sorts of engines.

Yeah, I know.. & really, it serves no useful purpose for those things.. Yamaha R1M, perhaps.. but not slow revvin' cruisers..

Commando has to be shimmed right, & really also needs rose jointed lateral chassis travel-limit links..

[eldog]

most likely
whats the benefit of having split crank bearings vs 'normal' ones

and
have you considered the Super Tenere offset 270' crank does that fit in with the current discussion?

its interesting that BMW use a Rotax designed twin as they also make racing and aero engines and maybe outboards as they are part of Bombadier group - they would have a range of design knowledge at hand

engine noob