How about a Desmo Norton?
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xbacksideslider said:
I think a pushrod desmo would be great. Like you said not because of the RPM potential but because you could run a much better cam profile. High lift without long duration due to slow ramps.
The Norton motor has a problem with high valvetrain inertia. Even the stock cam with stock springs tends to loft the cam over it's peak. The resulting crash is why you get the line that wears across the center of the lifter and right after peak lift is where cams show wear first. Lightening the valve train and installing better springs will eliminate that wear line and make the cam last longer. Jim
comnoz said:
You should have been on the design committee in 1947 then....
Sounds like a lot of work for not much return though. ?
What are we going to gain - 3 or 4 hp, at best, and a bit more torque throughout the rev range ??
Now, if the valve gear was safe to say 9000 rpms, and the crank and pistons likewise,
there would be 15 or 20 extra hp in the kitty straight off.
Complete redesign though, rather than tinkering with the entire valve train.
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Beautiful idea, but - because the desmo pushrod cam is grooved on the side of the lobes - the cam would have to be much larger in diameter and would not fit the Norton cases. Moving the cam with special cases would put it out of align with the pushrod tunnels and rocker arms.
Best and most economical way to cut Norton valve train weight and inertia is to go to the lightweight radiused BSA lifters with radius lobe cams and single Beehive springs with the tiny Titanium retainer. Half the reciprocating weight is gone along with the valve float, high wear and HP robbing problems you have with heavy stock items.
Best and most economical way to cut Norton valve train weight and inertia is to go to the lightweight radiused BSA lifters with radius lobe cams and single Beehive springs with the tiny Titanium retainer. Half the reciprocating weight is gone along with the valve float, high wear and HP robbing problems you have with heavy stock items.
Danno said:
So did the BRM V16's of old, now that we are reminded of that.
But as Colin Chapman once famously quipped, all the hp is going out the exhaust pipes to make that glorious sound.
And BRM V16's barely ever won a race.
Duc MotoGP haven't had too many wins lately either...
Danno said:
I think you're confusing something here: AFAIK Mercedes is working on eletro-magnetical valve springs to replace the coils but I haven't followed this topic since I left the company about eight years ago - anyway I was working on the engine with pneumatic valve springs back then ...
At least three independent pools are working on EMVs either with electro-mechanical or electro-hydraulic actuators. Electro-hydraulic actuators are not uncommon in single cylinder research engines, you can buy an of-the-shelf system from Lotus e.g. When I studied at RWTH Aachen university there was a full-spec EMV inline-4 on the dyno and IIRC also installed in a test mule but that was decades away from serial production. However all these systems are far too slow, heavy and power-consuming for racing and will not make it into F1 or Moto-GP in the near future.
A desmo pushrod Norton sound interesting but I don't think it worth the effort compared to other areas. It would only make sense in a complete redesign of the full engine. And then there's NASCAR engines which are second only to F1 engines in terms of BMEP - they run on pushrods and this close to 10k rpm and 150bhp/l. That would equal to a 110+bhp Commando. Sounds good enough to me....
Tim
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Rohan said:What is this plot actually plotting ??
Bit too cryptic for me..
Snotzo said:DUCATI's view of the desmo system
I think they're making the case for reduced mech. losses in the valvetrain?
With an SS head on the bench it takes very little effort to turn the bevel shaft and watch the valves do their thing, and being able to see the amount of valve overlap is also an education.
Ducati introduced the desmo valvetrain to their 125 GP racer back in the mid '50s, with Antoni winning it's debut race - and lapping the entire field.
No wonder it's been their trademark ever since!
Their 250 twin revved to 14,000 rpm, and was able to reliably take 17,000 rpm on the overrun. Back in the day of drum brakes it must have been quite a good thing.
My 900s run out of steam at 7,500 rpm (about the same point my 851 started picking up its skirts), so the valve float/bounce issue is hardly relevant, but must count for something in terms of overall mechanical efficiency.
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we are here again, replacing the iron horse shoes with super light alloy. Gee up neddy the milks late. :lol:
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Tintin said:Danno said:
I think you're confusing something here: AFAIK Mercedes is working on eletro-magnetical valve springs to replace the coils but I haven't followed this topic since I left the company about eight years ago - anyway I was working on the engine with pneumatic valve springs back then ...
At least three independent pools are working on EMVs either with electro-mechanical or electro-hydraulic actuators. Electro-hydraulic actuators are not uncommon in single cylinder research engines, you can buy an of-the-shelf system from Lotus e.g. When I studied at RWTH Aachen university there was a full-spec EMV inline-4 on the dyno and IIRC also installed in a test mule but that was decades away from serial production. However all these systems are far too slow, heavy and power-consuming for racing and will not make it into F1 or Moto-GP in the near future.
A desmo pushrod Norton sound interesting but I don't think it worth the effort compared to other areas. It would only make sense in a complete redesign of the full engine. And then there's NASCAR engines which are second only to F1 engines in terms of BMEP - they run on pushrods and this close to 10k rpm and 150bhp/l. That would equal to a 110+bhp Commando. Sounds good enough to me....
Tim
No confusion here. Judging by the spherical valves, rotary valves, and all the other experimental systems currently being worked on, there are probably multiple concerns thrashing each different type.
If you can build a Norton motor that will live at 9K+ rpm on 15:1 compression, you'd have it.
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'Desmodromics were invented when valve train technology was rather simple as a way to overcome valve float and increase rpm and thus horsepower. Adding Desmo valves to a Norton would only expose the next weakest link-the crankcases and crank design. Of course, these have been re-hashed repeatedly over the years.'
I haven't even lightened or polished the valve gear in my 850 motor. It is never going to rev past 7000 RPM, and even that is too much. Raising the rev limit to gain power in a long stroke motor is subject to the law of diminishing returns.
I haven't even lightened or polished the valve gear in my 850 motor. It is never going to rev past 7000 RPM, and even that is too much. Raising the rev limit to gain power in a long stroke motor is subject to the law of diminishing returns.
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'Desmodromics were invented when valve train technology was rather simple as a way to overcome valve float and increase rpm and thus horsepower. Adding Desmo valves to a Norton would only expose the next weakest link-the crankcases and crank design. Of course, these have been re-hashed repeatedly over the years.'
I haven't even lightened or polished the valve gear in my 850 motor. It is never going to rev past 7000 RPM, and even that is too much. Raising the rev limit to gain power in a long stroke motor is subject to the law of diminishing returns. 'Torque wins races'.
I haven't even lightened or polished the valve gear in my 850 motor. It is never going to rev past 7000 RPM, and even that is too much. Raising the rev limit to gain power in a long stroke motor is subject to the law of diminishing returns. 'Torque wins races'.
acotrel said:
Desmo systems were invented well before that !
Quite a number of patents appeared circa 1900 to 1910, when engine development was only just beginning.
It has oft been quoted that nearly every automotive engine invention had already been tried and tested before 1910,
before mass production of cars and engines had barely begun...
With hindsight, we might exclude electronic fuel injection from that list.
acotrel said:
NASCAR engines rev reasonably reliably to a rev-limited 9000 rpm,
and they are a big heavy-pistoned-pushrod-longstroke ohv engine.
So some folks know how to make them do it. (watercooled of course).
Nortons crank design notwithstanding...
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'So some folks know how to make them do it. '
Knowing how to do it, and being able to afford to do it are two different things. A 75mm stroke big bore Norton with a 4 valve per cyl. head might be a good thing, however why would you do it unless there was a competition class for it with big sponsorship money involved ? To get the bores big enough, the motor would need to be wider, then the transmission alignment needs to be altered. The problems compound. What we need is a 750cc Paton twin.
Knowing how to do it, and being able to afford to do it are two different things. A 75mm stroke big bore Norton with a 4 valve per cyl. head might be a good thing, however why would you do it unless there was a competition class for it with big sponsorship money involved ? To get the bores big enough, the motor would need to be wider, then the transmission alignment needs to be altered. The problems compound. What we need is a 750cc Paton twin.
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