Cool lifter design I stumbled onto...

Tintin said:

Rohan said:

And since nothing came with notes or explanations, it was unknown whether anything was a brilliant idea, or not so good.

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Let me put is this way: Finger follwers replaced tappets on all high-perforamce applications I'm aware of. Nobody would design a high-revving engine with tappets nowadays. Less friction and inertia and a more defined operation (e.g. you don't run into problems with unwanted or insufficient rotation of the tappet around its axis etc.) due to the different kinematics are the main benefits. The only real advantage of cup-type tappets is packaging, in order to get finger follwers to work nicely you have to find a good compromise between follwer length, inertia and packaging, especially if you consider rotating direct of the cam shaft. They work a little better if the are "pulled" instead of "pushed" by the cam lobes (in terms of realtive movement of the sufraces).

I'm not surprised that Hele, Heinz et all worked on this.


Tim

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Regular old lifters here :mrgreen: :

'Nobody should try to develop a high revving motor from a commando engine unless you know what you are doing or running an 80.4mm stroke or 75mm stroke and wanting to make real power.'

A 75mm stroke would be a much better way to go, but it might be easier to make a Norton type head to fit a Triumph motor and have the advantage of being able to play with the cams more easily
, and if you werre going to do that why wouldn't you use a Nourish engine unless your classic racing has silly rules which stop development of faster bikes?

acotrel said:

A 75mm stroke would be a much better way to go, but it might be easier to make a Norton type head to fit a Triumph motor and have the advantage of being able to play with the cams more easily, and if you werre going to do that why wouldn't you use a Nourish engine unless your classic racing has silly rules which stop development of faster bikes?

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Running a 75mm stroke in my F750 Norton Seeley Mk2
Running a Nourish NRE 750 race motor in another Seeley Mk2 - will premier this season.
Running a 59.6mm stroke Norton ultra short stroke in another Seeley Mk2 in Premier 500 class.

That's why I am keen on valve train options and enhancements. The only time I have seen cam lever followers was on overhead cams; fairly common practice.

Agreed the single billet cam of a Norton is a nasty bit to deal with and does not offer one the flexibility offered by two independent cams. What it forces one to do is depend more on experience and perhaps simulations calibration and benchmarking (Desktop Dyno) to shake out where you need to go and then design and order up a new cam.

I tried to nut out how to get a camshaft for a commando which is an adjustable assembly. I can't think of anything which would not fall apart and destroy itself. Your short stroke 500cc Norton sounds interesting, are you permitted to race it against the Molnar manxes with the Seeley frame ? in Australia we are not allowed to do that. A Nourish head seems essential for the 59mm stroke motor, how to you get high comp ratios, and the valve train light enough otherwise ?

The lever type followers are interesting. I haven't looked at the followers in the G45 Matchless motors, but they were the weak point. A friend of mine uses the followers from the 650CSR motor where the problem had been fixed.

If I was using a standard commando frame for racing, I would secure the ends oif the swing arm pivot with silentbloc bushes to allow the motor gearbox assembly to only vibrate vertically. I would still use the higherr balance factor so the engine did not destroy itself. If I had a road bike I would do the same thing, but avoid riding the bike in slow traffic. The balance factor is set to suit the normal rev range, Over 3000 revs the 72% BF gives a very smooth motor. The floating motor gearbox assembly gives poor handling in some situations. How can you have the handling of your bike dependent on the head steady and fiddly adjustment of a couple of screws? And how can you tolerate shagged crankcases , if you give the motor some stick ?
I think I must ride bikes a bit differently to most other people. I haven't had a road bike except for an RD250LC in the last 40 years. As a kid, I never rode long distances, but was involved in many derbys with my friends - the cops loved us. Then I raced for about 12 years on tyres where if you blinked you crashed. The sort of movement which occurs with isolastics is a big disincentive to me ever riding a standard commando. How can you feel if the rear tyre is moving around, and about to drop you onto the road when you are riding quckly ?

acotrel said:

The sort of movement which occurs with isolastics is a big disincentive to me ever riding a standard commando. How can you feel if the rear tyre is moving around, and about to drop you onto the road when you are riding quckly ?

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If you're riding that quickly on the road you're probably going too fast. Standard Commando is just fine for riding.

acotrel said:

If I was using a standard commando frame for racing, I would secure the ends oif the swing arm pivot with silentbloc bushes to allow the motor gearbox assembly to only vibrate vertically. I would still use the higherr balance factor so the engine did not destroy itself. If I had a road bike I would do the same thing, but avoid riding the bike in slow traffic. The balance factor is set to suit the normal rev range, Over 3000 revs the 72% BF gives a very smooth motor. The floating motor gearbox assembly gives poor handling in some situations. How can you have the handling of your bike dependent on the head steady and fiddly adjustment of a couple of screws? And how can you tolerate shagged crankcases , if you give the motor some stick ?
I think I must ride bikes a bit differently to most other people. I haven't had a road bike except for an RD250LC in the last 40 years. As a kid, I never rode long distances, but was involved in many derbys with my friends - the cops loved us. Then I raced for about 12 years on tyres where if you blinked you crashed. The sort of movement which occurs with isolastics is a big disincentive to me ever riding a standard commando. How can you feel if the rear tyre is moving around, and about to drop you onto the road when you are riding quckly ?

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Have you ever properly set up and/or raced (aggresively or otherwise) a Commando..............no, I did not think so. So what do you really know about it - apparently nada.

You have a knack for drifting off topic so no wonder you have difficulty with understanding let alone handling of (drifting off with) a Commando. By example your insistence on a silly higher balance factor (artifact of the solid engine mount days) for a Commando with nothing whotsoever to back it up; very retro indeed. Or suggesting above to install silent blocks to constrain the swingarm when it is already constrained; you just need to understand how it works and the fact that it does work.

So if you really forgot where you are, this thread is about the lever action cam followers, not Commando handling, and not balance factors.

swooshdave said:

Regular old lifters here :mrgreen: :

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That is the epitome of "not high revving". :mrgreen:

Which reminds me of a nice story a few years ago in a town in let's say the south of Germany. I was working on F1 engines and the test beds were on the same floor as the ones for the road car engines - just separated by two of these fancy doors with card readers to each side of the corridor. However the lock barrel had the same key and the old-timers amongst the R&D guys used the key and not the card reader. I was sitting at the control panel of a test bench which was running a Grand prix simulation together with the test engineer when one of the road car guys walked in with an intern in his wake. The engine had just reached a "pit stop" at that time and was idling under light load which means something like 7500rpm. The student looked at the monitor and expertly stated "Ah, high rev concept". The test eng smiled and answered "No, idle" and a few seconds later the simulated pit stop was over and the drivetrain went through the gears again up to 20krpm again with the appropriate fuss, roar and occasional flames which nicely illuminate the exhaust extrators. It took the guy another few seconds to realise what kind of engine he was looking at - his supervisor obviously didn't tell him beforehand.

Moral: High-revving or not is just a matter of perspective. :mrgreen:


Tim

Redline on that pushrod engine is 7100. Not bad.

Dances with Shrapnel said:

The only time I have seen cam lever followers was on overhead cams; fairly common practice.

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Oh, it is also not really uncommon practice on OHV engines, you just need to get a few years back in Norton's own history e.g.
Norton Model 18. IIRC the (in)famous Vincent-HRD engine also uses finger followers. It was even used on SV engines, e.g. Indian Scout.


Tim

Good point there Tintin. How soon we forget.

I was thinking of the early 750 Honda inline fours.

These days it is OHV levers or buckets.

I see that the new Norton 961 is a push rod engine.
When I first looked at it I thought it was an overhead cam engine like the Honda 750 with a dummy timing side to resemble a real Norton.

It seems like a lot of money for a [push rod twin. I would rather put the same amount of money into a Ducati.

Bruce MacGregor

Bruce if ya gonna jump fence and 4 decades ahead of Commandos for more fun then reminding ya that taking on balloon tire Ducad's is why I jumped skinny tire Peel up to 920 for the Drouin to make them say Not Fair its an old push rod! At least the Ducci's sounds like real twin cycles should, exhaust wise.

Bruce Mac said:

I see that the new Norton 961 is a push rod engine.
When I first looked at it I thought it was an overhead cam engine like the Honda 750 with a dummy timing side to resemble a real Norton.

It seems like a lot of money for a [push rod twin. I would rather put the same amount of money into a Ducati.

Bruce MacGregor

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So is the new Corvette... I'm sure that will slow down sales...

Older Ducatis are thunderbikes too, they have the same developmental problems as any other bike with a two valve air cooled motor. I'd be extremely happy to race my Seeley commando against them. And I am really sad that in Australia our obsession with 'periods' will never let that happen. I know I could get ahead of a lot of them, and r a cing against the would be superb. I really get annoyed when I am on the start grid (rarely) and most of the other bikes are either two strokes or boring four cylinder garbage. In our historic racing, the thunderbikes are distributed throughout four 'periods', they never end up all in one race . I hate it.

I saw this at Winton Motor Raceway, racing against the four cylinder superbikes, It is a 1000cc retro Ducati and I believe it would absolutely cream my Seeley, but I'd still love to have a go at it:

http://www.youtube.com/watch?v=sMkLu0ZNtRc

swooshdave said:

So is the new Corvette... I'm sure that will slow down sales...

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I'll try to leave the joking aside for now.... :wink:

In the end it comes all down to a very simple question: What do you want to do with your engine? Or to be more precise with that vehicle this particular engine powers? And this is where such an abstract thing as "philospohy" comes into play. An Amercian V8 certainly lacks the refinement of an Italian V8 - but that didn't stop Cobras beating the sh*t out of Ferrari a few times. Why? Mainly because a pushrod V8 is very small considering how much displacement if offers and displacement is one of only two variables which determine engine power in the end, all other things being relatively equal. A 7-litre DOHC V8 or V12 is a very big engine and gives a sh*tload of packaging problems where the OHV simply fits. Another very nice example is the Repco V8 of Buick descent. The story goes that Irving deliberatly switched to SOHC heads in the design process - because Tauranac could keep the body a little more slim and slender with the smaller heads and therefore gained an aero advantage over the overly complicated H16 and a power advantage over the smaller DOHC-V8 from Coventry Climax. Granted the DFV beat the sh't out of the Repco afterwards but only after the Repco already gained a World championship. Based on an engine that can be seen on the road still today, most likely in the form of a Range Rover. This engine serves a perfect example for KISS and JIT.

For the Corvette - as well as the "new Norton" - the OHV is more of an excerpt of their own history I'd say. There is no need for finger followers on an engine which does around 7krpm, that is for sure. It doesn't hurt thou and for an engine which goes to 20krpm the cup style tappets certainly come to their limit.


Tim

The Repco V8 was a product of an era when Australia was into technology. As a scientist I was part of it, sadly that era is now gone, never to return. The dead heads have won !

Seeing as we're there . . .







And the lexuses are as ugly as the maseratis these days . Standards are slipping . Maseratis are made buy that cheaper outfit , Ferrari .

Getting back on subject....... again.

Tintin said:

For the Corvette - as well as the "new Norton" - the OHV is more of an excerpt of their own history I'd say. There is no need for finger followers on an engine which does around 7krpm, that is for sure. It doesn't hurt thou and for an engine which goes to 20krpm the cup style tappets certainly come to their limit.
Tim

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Totally agree with a caveat here regarding pushrod engines and rpm limits as a blancket statement.

Here in the states NASCAR has pushed pushrod valve train to +10,000 rpm. Besides extraordinary engineering design and materials I believe it is the inherent advantage of the rocker ratios they use that reduces the significance of the mass of the pushrod/cam follower side of the system. I seem to recall reading where the greater ratios allow for a lower valve spring seat and nose force.

By example, with a rocker ratio of 1.6:1, the pushrod/cam follower side of the system only needs to perform at 62.5% of the valve motion (speed and acceleration); this is why the mass of these components becomes less critical when compared to say our Norton twins with a rocker ratio near parity (1.13:1). So doing some really (and I mean really) crude (call it half ass) parametric analysis here if we take your 7,000 rpm X 1.6 = 1,120 rpm. Knowing that we are only factoring the valve side of the system, arbitrarily discount it by 1,120 rpm which leaves you with 10,000 rpm which is what NASCAR has accomplished. The point being, it all makes sense when loosely attempting to scale things. But in the real world, when contemplating a big change in rocker ratio, I am sure there are some serious challenges, be it cam drive, cam/tappet interface issues, cam stiffness, cam support, pushrod stiffness etc...

On our Norton twins with a rocker ratio around 1.13:1, I doubt they ever really gave much serious thought to anywhere near those rpm. I am assuming the design of the Norton twin was driven primarily by marketing to the masses and non race applications. I suspect (wonder if) the early applications of the lever action (ex Manx single OHC engine) selected a rocker ratio simply out of spatial convenience.