Li tapers and increasing bhp.

[carlos fandango]

Ok, not wanting to hijack ( more than has been already ) the "spanish lady" thread , heres a new one .

I bought a Lince a few years ago , i was warned by a coule of people of the problem with the tapers shearing on std motors, hence my interest. The first thing i would normally do, when building a non std engine, would be to fit a gp taper crank, but with the lince i wanted to keep it fairly std, and wanted to keep the motoplat electronic ign. which by all accounts was excellent, apart from tbe shearing issue .
Now it is often quoted that the lince/lynx flywheel is the heaviest of the flywheels available, hence the torque force imposed on the thin taper , resulting in the shearing.
So, my idea was to lighten it to releave the stress caused.
Ive got my friend who does NDT , and he xrayed it for me , to see where the best place to remove material from . The xrays proved inconclusive as he couldnt get a decent image .
I had a knackered one , so i thought id experiment on it to see how far i could go .
I weighed it before i started , and it was 3.15kgs ...out of interst i thought id compare it to a std jet ( point motoplat) a std sx200 and a std indian electronic (li taper) flywheels
Lince 3.15 kgs
Jet 3.04kgs
Sx200 3.4kgs
Indian 2.62 kgs

So the lince one isnt the heaviest , the sx200 is , not by much though.

Warkton tornado gave his account of them not shearing when he raced , but i think the clue there is in the "racing "....they would of been lightened ? Maybe no fan either , further reducing drag on the taper ??

There is another likely cause though , the machineing of the taper itself ? .....as the majority of the failures ive heard about , especially std motors, appear to be linces , maybe there is an inherent fault in the spanish cranks ? a a sharp corner on the shoulder perhaps ?? I havent one to examine atm .
Thoughts ????

[Storkfoot]

Russ, I don't know the answer but if your Lynx motoplat electronic works as well as my old one did, I'd keep it in a standard engine not being used as a high mileage rally workhorse.

The lights were something else and it always started first kick. Never had another scoot like it.

[Digger]

Russ

The one I pictured (in that other thread) was from a Jet 200 but not sporting a Motoplat flywheel.

[carlos fandango]

Russ, I don't know the answer but if your Lynx motoplat electronic works as well as my old one did, I'd keep it in a standard engine not being used as a high mileage rally workhorse.

The lights were something else and it always started first kick. Never had another scoot like it.

Paul it is std. ....but we all want a bit more

Russ

The one I pictured (in that other thread) was from a Jet 200 but not sporting a Motoplat flywheel.

Thx digger good info , that would point to a problem with spanish cranks ....but it looks like the lighter indian flywheel , so lightening the flywheel may not help ?
Was it a std motor ?

[Adam_Winstone]

Depends how light you can go. As Webster said in his tuning manual, if you use a sufficiently lightened flywheel then you can use either taper crank. I've used Ducati brass centres with nylon fan and suffered no issues and I'd have no concern about using a sufficiently light electronic.

Adam

[Warkton Tornado No.1]

As you are aware, there are two threads running on this subject now.

Both of you are to be applauded, IMHO for taking away the element of hijacking that caused any upset in another topic.

Anyway, in my own attempt to be honest & open, not to massage my ego(!) this is the PM I sent to Dickie. I'm sure he won't mind if I repeat it here & offer the same sentiment to you:

I think that is a brilliant initiative you’ve taken there.

Unquestionably, there are genuine concerns about failure that we all must surely share.

As a Mechanical Design Engineer of some considerable experience, it’s inevitable that I have a fair amount of caution when anybody, including myself, jumps to assumptions, ready to dismiss the suitability of a component without knowing all factors that led to failure.

It’s very difficult to remain open minded yet focused. I have no doubt that I was chasing my tail with blinkers on when I last attempted to compete @ any level in Group Four due to the continuous breaking of gearboxes, all of them somewhat specially made close ratio sets using the best components available.

Eventually, I ditched the preferred six/seven plate generic clutch still commonly used & built my own using components from a motorbike.

The result was that the clutch eliminated all of the gearbox failures.

As a consequence, I’m willing to confess that much further “back in the day” when two stroke oil, piston quality & carburetion was very much a hit & miss science, running in frequently would involve several full seizures.

That sudden loss of inertia inevitably involves shear forces & the components subjected to that include the crankshaft flywheel taper & the lay-shaft. Although failure of those parts may not have been immediate, it would be a fool that claimed there was no consequence that may come into play @ a later date.

So, whilst I applaud your enterprise, I hope that it is a ‘warts & all’ analysis as much as that is possible.

If I can help in any way, do not hesitate to ask. Unfortunately, as many Forum readers would no doubt begrudgingly confirm(!) I can’t help you with evidence of broken components.

Kind Regards
Mark

[missing lynx]

I did a bit of racing in the early 80's and most racers used battery dead loss ignition which meant the flywheel had all the magnets and often the fins removed so they were as light as f**k thus putting far less strain on a li tapered crank also in an average meet you were lucky to cover more than about 40 miles. I sheered the crank on my tuned lynx and also found once tuned before it went pop it had a habit of blowing rear bulds at full revs