How about a Desmo Norton?

Tintin · Mar 18, 2015

acotrel said:
And this is not 'off topic' ? Are we talking about Norton Commandos ?

I'd say that converting a Commando drivetrain to pneumatic springs is as much on or off topic as converting to Desmo in the first place. Probably air springs win in the feasibility study but both ideas will probably not survive the slightest emergence of common sense in the process... :wink:

Tim

Bernhard · Mar 18, 2015

The stipulation that there will be valve spring inertia to overcome on a Desmo is so far of the case that I’m sure some of you don’t understand exactly what it does or how it works.
There are 2 cams on the Desmo for each valve, one to open and one to close it.
The valve spring fitted is only of nominal poundage, it can be as low as 5 lbs which is there to hold the valve on the valve seat and the cams do the rest of the work. Which is why you can get away with wild cam lifts that you cannot get away with on normal valve spring engines.

http://en.wikipedia.org/wiki/Desmodromic_valve

or , you can always use vale springs that act like a Slinky :!: :shock:

http://en.wikipedia.org/wiki/Slinky

Tintin · Mar 18, 2015

Rohan said:
No idea how they settled on those particular rpms.

In F1 it was driven by the weakest engine which was the Renault at that time - and Flavio was and still is best buddy of Bernie. So Renault had to do nothing and all the others had to detune their engines.

Some of the (MotoGP) engines could reportedly rev well beyond that.

Mercedes was working on a 22krpm engine for the second generation V8 just before it was frozen.

Tim

Tintin · Mar 18, 2015

Bernhard said:
The stipulation that there will be valve spring inertia to overcome on a Desmo ....

Eh? Who said that? I don't see such a statement anywhere except for the hint that there is helper springs.

Tim

BritTwit · Mar 18, 2015

comnoz said:
Now I am going to have to finish up my Norton spintron so we can see what is really happening.

Seriously?
You're actually building a spintron for a Norton engine?

Hobot · Mar 18, 2015

There is no accounting for logic in motorcycling & motor sports but the hi of getting away with something to get ahead. The biggest disappointment I've read about Norton came from comnoz explanation and dyno demo that long stroke bore friction nullifies rpm much over 7000. Also if short stroke Norton could make more power over red line then it runs into ability to dump enough heat to avoid burning alu pistons like rocket fuel for a time. With electro solenoid valves we could eliminate cam and its drive for variable valve lift which would add some pow to our low rpm Harley like antiques but would not have charge system enough to power it for long.

Rohan · Mar 18, 2015

Bernhard said:
Although I have never owned a Ducati, I bow to your superior knowledge on the up keep of these engines, however, back when I was a teenager, I enrolled at the Kirby/ Camp racing school at Brands Hatch when they were the only motorcycle racing school in the UK at that time, and got to ride at first, a non- Desmo 250 and then a Desmo 250, so I could tell the difference between the two. The Desmo 250 was streets faster, would rev quicker and higher, so was a much superior bike and I would have loved one at the time, but I just couldn’t afford one, which was a blessing in disguise as they require a strip down around every 2,000 miles to replace the main bearings, ( Remember this was a race designed engine!) the bevel drive bearing collapses, taking the top bevel with it (

Just for the record, its the big end bearing that was a little fragile in the Duc singles and early v-twins, not the main bearings.
They were apparently fine for the 250 and 175 singles, but when stretched to 350 and 450 desmos, could have a fairly short service life - although 2000 miles sounds rather short even then. They were also a roller bearing bigend, and Duc went to some lengths to specify what oil was suitable for them - multigrade 20w/50 apparently was not on the list of suitable oils. The early desmo 750 v-twins were also a little hard on their big end bearing, and again Duc recommended only some specific oils. Later designs employed a more robust bearing all around. Dunno about that race designed bit, Duc singles started out from fairly modest little ohc singles, and the desmo bit was added to some quite later....
But we diverge, slightly, as Aco like to point out !

xbacksideslider · Mar 18, 2015

The big ends of the singles and early twins also suffered from their lack of an oil filter - just a screen.

comnoz · Mar 18, 2015

BritTwit said:
comnoz said:

Now I am going to have to finish up my Norton spintron so we can see what is really happening.

Click to expand...

Seriously?
You're actually building a spintron for a Norton engine?

Actually I built one several years ago. I have been working on refining it a bit and getting it going again. I want to work on some valve train problems. [not desmo however]

B+Bogus · Mar 19, 2015

xbacksideslider said:
The big ends of the singles and early twins also suffered from their lack of an oil filter - just a screen.

Yes, and the squarecase twins introduced a rather small paper element filter, but the big ends were still fragile.
Possibly attributed to the 'step-function' advance curve on the stone-age electronic ignition causing rough running at low end, but more likely due to Combat-esque oil starvation issues which the racers encountered - bluing of the big-ends being a symptom :shock:
Similar fix, with case mods being the way forward.

The oil stipulated was Agip F1, but SAE 50 is the only oil I'll use in mine, as the gearbox runs in the same oil.
The gearboxes were weak too... :roll:

So what was the original question? :mrgreen:

acotrel · Mar 19, 2015

A nice new DOHC 4 valve per cylinder Norton Head, chain driven off the RHS might not be all bad .

Rohan · Mar 19, 2015

With a nice new unit construction short stroke bottom end, dual clutches and cassette gearbox.
Mr Garner has been notified....

But we seem to have wandered off topic somewhat, desmo is the thread title ere.
Or has your new policy of staying on topic gone already.....

john robert bould · Mar 19, 2015

Me being old and sad, just excepts the commando for what it is, what we need is loads of torque spread from 2000 - 5000 ,i like short shift performance , deep trust at low RPM. All this banter should be in the pub...which aint bad, plenty of good beer.

Tintin · Mar 19, 2015

Your prayers have been answered! Quite some time ago, btw .... :mrgreen:

Tim

B+Bogus · Mar 19, 2015

Tintin said:
Your prayers have been answered! Quite some time ago, btw .... :mrgreen:

Tim

Now that's off topic 8)

Danno · Mar 19, 2015

john robert bould said:
Me being old and sad, just excepts the commando for what it is, what we need is loads of torque spread from 2000 - 5000 ,i like short shift performance , deep trust at low RPM. All this banter should be in the pub...which aint bad, plenty of good beer.

Ed Zachary. The beauty of the Commando is in it's functionality, simplicity and ease of maintenance. Anything that complicates that for the sake of a few measly a bhp is unnecessary.

Hobot · Mar 19, 2015

Anything that complicates that for the sake of a few measly a bhp is unnecessary.

LOL. If immature illogical enough to be a voluntary motorcycler then everything else always makes sense w/o regard to common sense - at least to the instant innovator.

Bernhard · Mar 20, 2015

Rohan said:
Tintin said:

To get slightly on-topic again: I hope nobody wants to convert a Norton to pneumatic springs by now

Click to expand...

If it could reliably run 19,000 rpms, like the MotoGP bikes do,
then it would probably be a hoot !!

That 'reliable' may be a bit of a problem though....

strange.........the Honda RC 146 125cc FIVE cylinder reputedly revved to 22,000 rpm :!: :!:

http://www.motorcycle-usa.com/289/15555 ... RC148.aspx

http://www.bing.com/images/search?q=hon ... ORM=IQFRBA

john robert bould · Mar 20, 2015

Translate please.

hobot said:
Anything that complicates that for the sake of a few measly a bhp is unnecessary.

Click to expand...

LOL. If immature illogical enough to be a voluntary motorcycler then everything else always makes sense w/o regard to common sense - at least to the instant innovator.

Rohan · Mar 20, 2015

Bernhard said:
strange.........the Honda RC 146 125cc FIVE cylinder reputedly revved to 22,000 rpm :!: :!:

No quite so difficult to do when the engine is only a tiddler, and everything is tiny - what would the valves weigh ?!
(Although it was a bit of an achievement at the time, the harmonics of high revving engines being about unknown).
Bit trickier when the engine is a full blown 1000cc, and the valves are man sized....

My little (purchased) miniature aero engine revved to 24,000 rpms on full song, some time back.
That hurts the ears, I can report.

How about a Desmo Norton?

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