270 degree crank

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As any of you lads ever built a 270 crank for a Commando? Phil Erving suggested this revised throw to Edward Turner in 1947, But they {triumph} dismissed it. Proberly due to Re-tooling costs.plus the little 500 twins where "fairly "smooth any way.
I have read plenty of advantage's using this design [Yam TRX 750], one being a 47% reduction in vibes,plus improved torque compaired to 360 throw.. Exhaust beat is "V" twinish....your views on this please.
 
Thanks Les,
$1000 dollars for a welding job, sounds expensive..well to Me a welder anyway...I know they are jig set up and heat treated afterwards..then ground.
But as anyone on this forum got one? and what is the differance?
 
Gday John, Ive purchased one of Geoff Collins of Offset 90 degree(270 deg firing) cranks for my featherbed 920cc project. I can't report on how they run because mine sadly isnt a goer as yet! Is there an award for the slowest or longest build? But anyway, if you give Geoff a call, he'll gladly fill you in on any details. I found him extremely helpful, we now also keep in contact weekly.
Regards Foxy
 
John,

Go to a CRMC meeting and look for Gary Thwaites, his 750 is a short stroke 90 degree crank!
 
I wonder, having never seen one, if you could use the 270º crank from the new Triumphs and modify it for a Norton...
 
john robert bould said:
.... one being a 47% reduction in vibes,...

A Commando or to be precise the Isolastic relies on vibes being in the X-Z-plane of the bike aka the absence of a rocking couple. This is the case for a 360deg crankshaft but not for any other config. I haven't read Irving's explanation in his own words yet but from the websites on this subject it becomes pretty obvious that people who do this either don't understand the correlation of mass forces and mass moments or at least fail completely to mention them in order to support their "less vibes theory". And the TRX had balance shafts. Guess why..... :wink:



Tim
 
Tintin said:
john robert bould said:
.... one being a 47% reduction in vibes,...

A Commando or to be precise the Isolastic relies on vibes being in the X-Z-plane of the bike aka the absence of a rocking couple. This is the case for a 360deg crankshaft but not for any other config. I haven't read Irving's explanation in his own words yet but from the websites on this subject it becomes pretty obvious that people who do this either don't understand the correlation of mass forces and mass moments or at least fail completely to mention them in order to support their "less vibes theory". And the TRX had balance shafts. Guess why..... :wink:



Tim

People doing this mod tend not to have Isos.

Will
 
john robert bould said:
As any of you lads ever built a 270 crank for a Commando? Phil Erving suggested this revised throw to Edward Turner in 1947, But they {triumph} dismissed it. Proberly due to Re-tooling costs.plus the little 500 twins where "fairly "smooth any way.
I have read plenty of advantage's using this design [Yam TRX 750], one being a 47% reduction in vibes,plus improved torque compaired to 360 throw.. Exhaust beat is "V" twinish....your views on this please.

1947....probably had to do with the magneto thingy...or else they would have had to come up with another ignition.
In 1947 in England right after the war, going to the store to get food or getting to work counted a lot more than how fast or how much vibration....would it start! would it go....beats walking any day.

1950 dave
 
Interesting replie's, As the commando was developed with the mighty 4 where well and truly knocking at the door, time was against the Norton..it was only the old die hards keeping up sales, and history show's that was not enough .
Combat engine's where throwing rods.frames cracking, a thing of the past, unless you are wringing the life out of them [Hobit?] To day these
twins are still shakeing bits off.
Just read hear about a main jet being found in the float bowl! ...Isolastics reduced the vibes reaching the rider..but allowing the engine to become a milk shaking machine ..Not really a good idea.
Surely the isolastic design is flawed..
1, Rubber is not only soft in summer,hard in winter but continue's to "cure" in time becomes hard.
2, As the weight of the engine /transmission press's the donuts downwards this constant state of rubber compression restricts any downward movement..but allows plenty of "upwards" movement..to me addressing the effects is silly...preventing the cause sounds better. This post is designed to find any one riding a 90 degree motor..and what do they think. As yet only links
 
john robert bould said:
Surely the isolastic design is flawed..

As are gazillions of other design which are a workaround to a certain problem under time and money constraints .... so what?


Tim
 
Tintin said:
john robert bould said:
Surely the isolastic design is flawed..

As are gazillions of other design which are a workaround to a certain problem under time and money constraints .... so what?


Tim
Tim ,So what if they where changed. kawasaki very very quickly discovered the old bsa 650 twin they copied was rubbish. i myself love modern inovation, my Merc common rail with 3000 bar injector pressure runs like a watch...i had a old ford 2.3 diesel that ran about as smooth as a Commando! 40 year old Engine's can be changed over night..but humans with 2 million year evoluation...take a bit longer!
 
Here Here Here, Ms Peel Combat/steel flywheel, small ports, one bigger carb out 2-1 loong megaphone, was not hurt by my expressiveness into new levels of performance, but accidental detune putting on dual 932's set rich with fast response race needles, first kick every time even on an almost freezing day, so well kicker out raced my kick and I stumbled and released WOT grip and by time I regained feet it had rev'd pass red zone and then got her second breath and slapped back so hard on the isolastic it slapped my adrenalized grip right back in my face to make me stumble again in horrified state to make 3rd attempt to shut her down after a couple seconds no tach needle seen d/t speed of its bouncing off peg, and lost my wits to finally snap throttle shut instead of holding WOT and pressing kill, so not to extra suck the piston up so hard crank ends ruined everything on both ends, but was still pretty spunky another 2000 miles with big upper and lower wind screen in winter to 110mph/5000rpm and pooped pooped out. Prior was good over 120 with this screen. Then the 1098's came out and decided Norton was not enough and jump ship. Got guts of that engine and will reproduce the combo someday to see if it really wasn't a fluke.

On point of subject line, a couple decades reports, horizontal vibes will be felt in offset cranks solid or isolastic mounted but nicer than 360 in solids. Same with adding more rubber area or harder compliance. I remind thee my tri-linked Ms Peel flat uncanny disappeared from pilot sensation and seemed impossible to upset no matter what I did or took on. So to me its silly, misinformed, academic waste of money and talent and materials to deviate from merely completing the ingenious potentially Unapproachable Norton Commando. The only advantage mystery to me is if the offset power pulses could hook up better on tire edges.
But on the other hand Norton ain't got no 15-20,000 pulses per minute to confuse the quantum interface of rubber and tarmac.

Geoff Collins built the welded nitrided 360 crank for big block blown Peel.
Its not his profession but deep brain infection with expensive big jigs plus cams and ignitions to suit to offset deviate crowd, all because no one but no one else yet knows what they are missing out on a full linked iso Commando with turbo jet smooth thrust and electric motor response.
 
hobot said:
Here Here Here, Ms Peel Combat/steel flywheel, small ports, one bigger carb out 2-1 loong megaphone, was not hurt by my expressiveness into new levels of performance, but accidental detune putting on dual 932's set rich with fast response race needles, first kick every time even on an almost freezing day, so well kicker out raced my kick and I stumbled and released WOT grip and by time I regained feet it had rev'd pass red zone and then got her second breath and slapped back so hard on the isolastic it slapped my adrenalized grip right back in my face to make me stumble again in horrified state to make 3rd attempt to shut her down after a couple seconds no tach needle seen d/t speed of its bouncing off peg, and lost my wits to finally snap throttle shut instead of holding WOT and pressing kill, so not to extra suck the piston up so hard crank ends ruined everything on both ends, but was still pretty spunky another 2000 miles with big upper and lower wind screen in winter to 110mph/5000rpm and pooped pooped out. Prior was good over 120 with this screen. Then the 1098's came out and decided Norton was not enough and jump ship. Got guts of that engine and will reproduce the combo someday to see if it really wasn't a fluke.

On point of subject line, a couple decades reports, horizontal vibes will be felt in offset cranks solid or isolastic mounted but nicer than 360 in solids. Same with adding more rubber area or harder compliance. I remind thee my tri-linked Ms Peel flat uncanny disappeared from pilot sensation and seemed impossible to upset no matter what I did or took on. So to me its silly, misinformed, academic waste of money and talent and materials to deviate from merely completing the ingenious potentially Unapproachable Norton Commando. The only advantage mystery to me is if the offset power pulses could hook up better on tire edges.
But on the other hand Norton ain't got no 15-20,000 pulses per minute to confuse the quantum interface of rubber and tarmac.

Doe's that mean you have ridden a 90 degree crank?

Geoff Collins built the welded nitrided 360 crank for big block blown Peel.
Its not his profession but deep brain infection with expensive big jigs plus cams and ignitions to suit to offset deviate crowd, all because no one but no one else yet knows what they are missing out on a full linked iso Commando with turbo jet smooth thrust and electric motor response.
 
john robert bould said:
Tintin said:
john robert bould said:
Surely the isolastic design is flawed..
As are gazillions of other design which are a workaround to a certain problem under time and money constraints .... so what?
Tim ,So what if they where changed.

The Commando was obviously intended to be the last and a rather short run of the old pushrod engine and this only because of a certain mix of mismanagement, lack of money etc. Norton wanted to do a new engine to replace the Hopwood twin but for several reasons they failed and had to do something that made the old mule acceptable. The Isos do this and as a design idea they are pretty good IMHO - the Commando design team analyzed the problem - the shaking engine - had a look at their resources and realized that a new engine didn't fit the time and money constraints. The fact that it is a classic case of dealing with the symptoms instead of the root cause doesn't really matter here IMHO.

Now if you enter a 270deg crankshaft and just add it to the Commando concept you basically spoil it big time. It simply doesn't make sense of you don't add a third main bearing AND a balance mechanism. The main reason for going to 270deg in the TRX, the 961 and also the current Bonnie is the fact that this layout can be brought to inline-four vibration levels just by the addition of a single balance shaft - the 360deg version would need two for that (or the very clever design idea of a balance rocker like the current BMW P-twins or the Duc supermono). And I was told by people who tried it that the 961 still shakes quite a bit so there is no guarantee that it'll work out if you don't get the maths right.

Putting a 270deg crankshaft in a rigid mount is a bit different however as the individual situation changes with the installation. The human body reacts differently to vertical and horizontal vibrations so whether the rocking couple is better or worse depends on the stiffness and thus the Eigenfrequency of the engine and chassis installation in the direction in question. However IMHO it is far more reasonable to reduce the source of the vibes - and this is the weight. Slipper pistons with reduced compression height and longer rods are far better than playing around with the crank which only redirects the forces instead of minimising them.


Tim
 
Tim, Excellent post! Just the read i wanted [proper info] But have you had one...or rode one, or got a mate that as?...where does 41% less vibes come from. There is a guy in Canada claiming and producing great things...for 90 degree crank configurations the maths add up, when one piston is a TDC the other is at max speed in the other direction...is this a good design starting point?
I agree with your comments regarding the position Norton faced , they did not have the right forward thinking team,or spare money..sound 's like our past goverment!
 
john robert bould said:
But have you had one...or rode one, or got a mate that as?...

Not a Norton, but at the university I was dealing with a TRX as a test mule. It vibrated more than the GSX-R inline four although it had a balance shaft. By far the best answer to the vibes problem is a balance rocker like BMW uses in their current parallel twin.

where does 41% less vibes come from.

Short answer? A calculation error or a severe case of self-delusion.

Long answer see above.

...for 90 degree crank configurations the maths add up, when one piston is a TDC the other is at max speed in the other direction...is this a good design starting point?

For an engine which will be relatively tame with only one balance shaft? Yes. For an engine without a balance shaft it has no real advantage that you don't have to pay with other disadvantages and it depends on the overall package which engine will be better. For a Commando its rubbish - but I think I mentioned it before .... :wink:

....they did not have the right forward thinking team...

I wouldn't subscribe to that, the Isos are a pretty good answer to the task of exposing the driver to less vibes and in the end that was what was asked by the management. Certainly cheaper than a new engine and from a manufacturer's point of view that is not a bad thing, I'd say.


Tim
 
I see the guy in Canada who converts the 360 into 90 as revised the crank to place the counter weight closer to the centre line and a reduction in overall weight, Is it early days to "write off" the work being done?

I have not first hand experiance nor equipment or time to "play" with crank revisions, My original post was the find someone mayby on this forum who as, and as yet no one as stepped forward the give the facts, and more importantly the MATHS behind them, Maths was Phil Ervings starting point and the most important, Simply cutting up cranks the See was not the guys policy.
Maths first, then experimentation next. I think Phil Erving would be shakeing the Canadian guys hand.
To bring this debate to a comparison i spent two years designing and producing the Lansdowne damper kit..complete failure at first! But against all the Poo Pooing from Die hards i continued the work. But the same old die hards still prefer the old 1953 500 twin dampers, putting up with the knocking and clunking
Now i am getting orders from recommendations, not from my claims, Claims mean nothing . Norton's Iso system was a [as you well put it] a last ditch attempt to hang onto a slipping market...but the big Z1000 with every thing except a Norton badge where poaching the Brit lads..but thats history.

I have just bought a 71 commando in big bits , a "given up" project that some one pushed into a garden shed 12 years ago. my intension was to use it as a experimental bike [90 crank etc] But it could be a Long range fastback, Much to rare to hack about, so i want to restore it back to 100% ...Ho shit!! There goe's my Old die hard brain kicking in :!: But it will have a Lansdowne damper kit :p

Chow for now.
Best regards
www.lansdowne-engineering.com
 
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