Compression and Ignition

Joined
May 4, 2013
Messages
200
Dances with Shrapnel said:
Maybe at idle but far from accurate statement as the engine speed increases. To illustrate, take this to an extreme point of just at valve float; most all the energy that goes into opening the valve and is lost.
It's still not lost near valve-float.The valve spring pushes all the valvegear closed at maximum velocity.The cam slows it up for gentle valve seating.The force pushing on the cam returns that kinetic energy to the cam.

If the valvegear completely missed the closing ramp and landed on the base circle,things would be different.You could have big problems too.
 
Joined
Jun 30, 2012
Messages
9,513
Country flag
I've never thought about the energy used to open the valves. I do know that the shape of the cam's closing side is important though. The cams used in the Triumph GP were valve droppers, the E3134 was a much better race cam. The cams used in my 500cc short stroke Triumph did not have much lift, however they were very slow opening and closing, and had durations of more than 360 deg. It was often revved to over 10,000 RPM. The guy who built the original motor used to work in the Triumph factory, and the bike had some strange things about it e.g. the crankcases had no numbers. The drum front brake was similar to the Tiger 110 brake except the fins were thinner and it had an extra one outside the spoke flange. A lot of shifty things happened back in those days and I know of some guys who actually had the keys to the Norton factory. We have some interesting bikes in Australia, due to some nefarious activities of a few international riders.. There are a couple of manxes that most of us would die for, sitting in pieces distributed around one of our capital cities. Plus a couple of other bikes that were supposed to have been returned to the factory, but weren't. I hope you guys have got a sense of humour, ours is a bit unusual.
 
Joined
Jul 8, 2011
Messages
2,668
Country flag
X-file said:
Dances with Shrapnel said:
Maybe at idle but far from accurate statement as the engine speed increases. To illustrate, take this to an extreme point of just at valve float; most all the energy that goes into opening the valve and is lost.
It's still not lost near valve-float.The valve spring pushes all the valvegear closed at maximum velocity.The cam slows it up for gentle valve seating.The force pushing on the cam returns that kinetic energy to the cam.

If the valvegear completely missed the closing ramp and landed on the base circle,things would be different.You could have big problems too.
In fact the higher the speed the greater the energy is lost to accelerating the valve train open (forget about the valve spring forces for now and the lower the energy recouped from the valve train due to the valve spring forces (only) closing the valve train and acting on the ramp.

At ever increasing speed the "valve gear" starts to gradually reduce loading on the "valve gear" when closing.

It is simply a matter of force dynamics and kinematics.

The big forces are acceleration of the valve train and they go up with the square of the speed whereas the minimum forces are valve spring induced and the spring must accelerate the valve train (remember that bit about forces and the square of the speed) to close the valve train and whatever is left after that is what is available the feed back into the cam lobe upon closing. As the speed goes up there is less force available to feed back into the engine.
 
Joined
Jan 4, 2011
Messages
565
Country flag
When I got rich and decided to go to open class I bought a six speed TT box.
I probably built my bike up for the price of a TT gearbox. :lol:
My mates son Tyler Lincoln was riding the CMCRR Presidents ES 2 at the last couple of meets and was very quick, he's not even 16 yet.
 

johnm

VIP MEMBER
Joined
Feb 26, 2008
Messages
874
Country flag
Tell that young man he is very lucky. Those ES2s are amongst the best Classic race bikes in the world.

And they do cost a little more than a TT gear box :)

I had a look at the laptimes on Marktime nz. Is he riding the 500 Clubmans bike or the open class 500.
 
Joined
Jun 30, 2012
Messages
9,513
Country flag
If you don't have the gearbox, the situation can be that you must choose where you lose races - at the start or at the ends of the straights, or in the twisty bits. There is a father/son combination here who played t o the max with Matchless/AJS singles. I once looked down the inlet port on one of their motors, you could almost fit your fist down it. They own a pub, so can afford to play, and were successful. I said to them 'why don't you buy yourselves a Jawa two valve motor, and you will start where you finished with these motors ?' They bought two motors and return pumps and had them prepared by our best speedway guy. First time out, they blitzed a new Walmsley engined manx which had a good rider on board, and they have gone from their onwards and upwards. Of course the latest is that they are now attacking the Jawa motors - I think that is a futile exercise. If you look inside a fast ES2, you will probably find the internals are made of pure gold.
 
Joined
Jan 4, 2011
Messages
565
Country flag
If you look inside a fast ES2, you will probably find the internals are made of pure gold.
I would say that applies to most of the winning bikes in the classic racing here. For me the satisfaction is building and riding. I could make my BMW into a very fast machine but I like the fact its all factory components.
Young Tyler weighs in at about 50kgs, with his factory race Honda him and the bike are only 150kgs ( or there abouts).
I'm working on a 500cc BMW racer for next year, they say that will be a slow slug too... :lol:
 
Joined
Jun 30, 2012
Messages
9,513
Country flag
Combat, There is one lesson that I learned from building my Seeley 850 - never predict the outcome of your efforts. You don't have to spend a big dollar. My 850 motor is rubbish, there is nothing trick inside it, however the bike is extremely rapid and versatile. I'm lucky that I've got a bit of experience , and that sends me in certain directions, however even with that you cannot tell how good a bike will be until you test it in anger.
 
Joined
Aug 26, 2010
Messages
8,216
acotrel said:
If you look inside a fast ES2, you will probably find the internals are made of pure gold.
No more than a Manx is ??
And it doesn't have all those uber expensive bevelly bits...

One magazine report somewhere delved into what was in one of those. (Race ES2).
Steel flywheels and a Manx rod and forged piston was a big part of it.
Some alloy welding to give a seriously downdraft and offset inlet port was a big part of the performance.
 
Joined
Jan 4, 2011
Messages
565
Country flag
With Manx's it starts to get a bit murky, is a Manx that it less than 5 years old built from all new parts and a 6 speed gearbox really a classic bike?
There are guys here racing genuine Manx's who think not, trend here is shorter strokes bigger valves and methanol.
The CMCRR is pre 76 non Japanese and non Japanese components, membership is declining as guys my age and younger don't remember British bikes racing...just breaking down and leaking everywhere :lol:
 
Joined
Jun 30, 2012
Messages
9,513
Country flag
Cheaper with the same result is always better. A two valve jawa engined featherbed in good hands can defeat manxes . The motor is one tenth of the price. It is a matter of being competitive and up with the leaders. The latest Molnar or Walmsley engine might give you the much needed psychological boost, but when push comes to shove, the other is right there with them. The rider of this bike didn't need a manx Norton to help him win, and his opposition had a lot of good stuff including Read on an old MV4 and Jeremy McWilliams on Hemmings Domiracer :

 
Joined
Jun 30, 2012
Messages
9,513
Country flag
Combat, anyone who has an original manx has a museum piece , and not a racing bike. My friend is an old A grader and has an ex-Jack Ahearn 40M. His son wants to race it. Our latest discussions have been about buying a modern motor and tucking the original away. The situation will soon be that the next generation of motorcyclists will never be able to find out what Geoff Duke and Artie Bell felt in 1953. Racing an original manx is like hanging the original Mona Lisa in your toilet. It might brighten things up for a while, but really ? ? ? Demos like Goodwood, I can believe in - forget the rest with that stuff.

If you go to Goodwood Revival this year, two of our guys will probably be there with a manx. Bob Minogue is the owner, Bob Rosenthal will be the rider. Rosenbob is an old A grader who started riding a 750cc Norton twin in the sixties and progressed to sponsored TZ700s. You might enjoy watching their efforts. I just wish I could be there too, it will be interesting.
 
Joined
Aug 26, 2010
Messages
8,216
acotrel said:
Combat, anyone who has an original manx has a museum piece , and not a racing bike. .
Not only that, but the recently made manxes are so much faster than the old stuff its almost like they are not even in the same race.
More reliable too, better materials and better machining (CNC, way more accurate).
In the UK, owners of ESO engined etc things are leaving them at home, and getting into a new manx...
Barry Sheene RIP had a new Molnar Manx, and then a new G50, and loved them
What was his younger days quote about 'them slow old things' ?
 
Joined
Jun 30, 2012
Messages
9,513
Country flag
In Australia the ESO engined featherbed, is the cheapest way into historic racing, and be relatively competitive in a good class. There are other things which are much more monetarily attractive than a Molnar manx, and supply the same value e.g. an XR69.
 
Joined
Aug 26, 2010
Messages
8,216
acotrel said:
e.g. an XR69.
Is an xr69, whatever that is, eligible to race in pre 63 races ??

Classic racing is not 'cheap' racing, its classic racing.
When new, a manx cost more than a house, for most of the years they made them.
So never were 'cheap'.
 
Joined
Jan 4, 2011
Messages
565
Country flag
Rohan said:
acotrel said:
e.g. an XR69.
Is an xr69, whatever that is, eligible to race in pre 63 races ??

Classic racing is not 'cheap' racing, its classic racing.
When new, a manx cost more than a house, for most of the years they made them.
So never were 'cheap'.
there is getting less and less of the pre war stuff racing and even the 50's and 60's is in decline, due to the aging riders and the cost of ownership.
With our local track at $10K for a day, punters are required, and punters who are interested in bikes generally want to see the bikes of their 'yoof".....and they were Japanese. Classic Racing is feeling the pressure here, especially as it has a pre 76 non Jap cutoff.
When they get the Post Classic guys along the crowds are bigger, especially when they get the Aussies over. :mrgreen:
 
Joined
Jun 30, 2012
Messages
9,513
Country flag
In Australia we now have six historic periods to choose from. No racing is cheap, however we always want value for money. The best fun you can have is to be in a bunch of guys on similar bikes going for it. I mentioned the Jawa engined featherbed in Period 3 (pre62), and the XR 69 in Period 5 ('73 to '82). If you want the competitive fun ride , those two options provide the best value for money in my opinion. To me it is irrelevant which period I race in, as long as there is a fairly level playing field, and I am competitive in it. As much as I love my Seeley 850, there is no race class which really suits it, and that situation applies to most of our old bikes. I'd absolutely love to get it onto a grid full of old air cooled four stroke twins and triples - bring out your silly Ducatis !
Have you seen this guy ? :

http://www.youtube.com/watch?v=uXR65av-Qr0

http://www.youtube.com/watch?v=twk1eC0rhdc
 
Joined
Jan 4, 2011
Messages
565
Country flag
Cool clip, I have not seen a Laverda on the track here.
For the Barry Sheen in October I hear there are 24 solos and 15 sidecars coming over. Robbie Phillis and Mal Campbell.
Must get my entry in :mrgreen:
 
Top