360 Crank Sequence? I'm Confused.
- Thread starter jaydee75
- Start date
- Status
Two-stroke engines fire on every stroke, since they use the crankcase for compression. "Twingle" is a term for a two-cylinder 2-stroke with a single combustion chamber. As fa as I know, Puch is the only manufacturer that made this configuration and it was sold in the US by the Sears-Roebuck store chain under the "Allstate" name.
My first non-scooter bike was a 1960 Ariel Leader. It looked enough like a scooter to keep Mom off my case - she wouldn't let me have a "real" motorcycle. The Leader was actually a pretty good performer for a 250. I could keep up with Austin-Healey Sprites, but not the A-H 3000 or the MGB. Two-strokes are becoming extinct as road bikes, particularly in the US, because of emissions issues. My Leader had bee named "Smokey" by it's original owner, painted on the leg-shield. It certainly lived up to the name. Things improved when Ariel came out with a change from 16:1 gasoline/oil ratio to 32:1. With Bardahl oil, you could go to 48:1.
My first non-scooter bike was a 1960 Ariel Leader. It looked enough like a scooter to keep Mom off my case - she wouldn't let me have a "real" motorcycle. The Leader was actually a pretty good performer for a 250. I could keep up with Austin-Healey Sprites, but not the A-H 3000 or the MGB. Two-strokes are becoming extinct as road bikes, particularly in the US, because of emissions issues. My Leader had bee named "Smokey" by it's original owner, painted on the leg-shield. It certainly lived up to the name. Things improved when Ariel came out with a change from 16:1 gasoline/oil ratio to 32:1. With Bardahl oil, you could go to 48:1.
- Joined
- May 27, 2013
- Messages
- 1,112
acotrel said:
Not sure what any of this actually accomplishes. My Honda V-twin is 270 degree, but it still has balance shafts to reduce vibration...what does a 76 or 90 degree do? You still have the rotating mass to deal with. In my opinion the whole twin vibration issue is related to the fact that balancing was not understood back then...taking an engine design from 1937 and increasing displacement to the point of destruction due to the rotating mass.
The 270 degree Honda is smooth as silk but it sounds like a sewing machine...like most Hondas
I think balancing was understood all right, I just think sewing machine smoothness wasn't as important to riders as it is today. All bikes were generally lighter depending on cc's and much, much simpler by design. You mentioned the balancer in you Honda's engine, I'm guessing most all motorcycle engines utilize them now. The current Triumph Bonneville is a good example. Same 360 degree vertical configuration as our Norton but their balance shafts make them smooth, smooth. An inline three cylinder engine with 120, 120, 120 degree throws like that in my Speed Triple is inherently smooth but it too has balance shafts to take out or at least modify that last buzz. This smoothness costs though and until Japan showed the way with factory smoothness, it was not deemed that important so an 80% balance factor (might have that number wrong) was the perfect compromise between rocking and vertical movement. As engines got bigger the vibes that were produced got out of hand and so were born ISOLASTICS!, yeah, yeah. By the way, somewhere, someone who may still be around coined that word. "ISOLASTIC" what a legacy!
- Joined
- May 27, 2013
- Messages
- 1,112
Biscuit said:
I'm not really sure that balancing was understood. At least not in the mass produced way it is today...maybe for race engines, but like you said the new Triumph twin is 360 degree with balance shafts. If it was understood why go through the engineering of the isolastic system to reduce vibration? It certainly wasn't cheaper.
I think the isolastic method of insolating the rider and the rest of the motorcycle from engine vibration would be cheaper than re-engineering the engine to incorporate balance shafts to actually quell the vibration. As you said the engine was an old, old design and would have to had been totally re-engineered to make room for extra gears, shafts etc. There's barely room in the cases for just the crank as it is. I don't think there was money for that so simply hanging the motor from admittedly cleaver isolastic mounts was the easiest thing to do.
- Joined
- May 27, 2013
- Messages
- 1,112
Biscuit said:
Yes Norton was financially strapped and was trying to get more life out of an old engine, but if balance shafts were understood why weren't there any new engines by other manufacturer's with balance shafts?
In searching for information on when modern balance shafts were designed into engines the earliest reference is for an automotive engine built by Mitsubishi in 1975 "Silent Shaft". Motorcycle engine balance shafts came later, long after Norton was out of business. The Commando was designed in 1967.
Maybe someone else has better information on this, but it seems to me that Norton engineered the isolatics to solve a problem that at the time did not have any other known solution.
- Joined
- Oct 19, 2005
- Messages
- 18,978
Duh the English patented the majority of worlds past major mechanical and engine related innovation & inventions and balance shafts were one of them. Norton knew their engines were obsolete some decades before the Commando so decided to go the simpler cheapter path and thank goodness they did as pulbic could not afford what they came up with that didn't need no stinking balance shaft. I enjoy telling the BMW owner where their Boxer VW and mc engines got their name.
http://en.wikipedia.org/wiki/Balance_shaft
3 cylinder balanced Commando engine
http://www.andover-norton.co.uk/Jake.htm
http://en.wikipedia.org/wiki/Balance_shaft
3 cylinder balanced Commando engine
http://www.andover-norton.co.uk/Jake.htm
- Joined
- May 27, 2013
- Messages
- 1,112
hobot said:Duh the English patented the majority of worlds past major mechanical and engine related innovation & inventions and balance shafts were one of them. Norton knew their engines were obsolete some decades before the Commando so decided to go the simpler cheapter path and thank goodness they did as pulbic could not afford what they came up with that didn't need no stinking balance shaft. I enjoy telling the BMW owner where their Boxer VW and mc engines got their name.
http://en.wikipedia.org/wiki/Balance_shaft
3 cylinder balanced Commando engine
http://www.andover-norton.co.uk/Jake.htm
My comments were specific to "Modern" balance shafts as we know them today. The invention goes back to the early 1900's...but name a motorcycle engine that had balance shafts at the time the Commando was being manufactured. I think you are being too harsh on the engineers...it wasn't common practice even if they had the funds any new engine would likely not of had balance shafts in that time period. Norton had an overhead cam engine in development at the time that they shelved. No where do they mention balance shafts...and no one else was using them to smooth out the engines of the time. The only point I'm trying to make is that balance shafts were not on any manufacturer's radar at the time...let alone a company in financial trouble trying to find a way to survive.
- Joined
- May 27, 2013
- Messages
- 1,112
Hobot,
You constantly rip Norton management for the failure...but the history shows that the actual decline happened some years sooner. Sales of British motorcycles were fairly strong for a number of years after WWII. The public liked the British bikes particularly in the US. The recovery after the war comes into play as many of the motorcycle factories were destroyed. Yes they should have invested more, but there were many new bikes produced into the 60's and some big failures particularly smaller displacement engines trying to compete with the Japanese.
The biggest problem was how revolutionary the Honda 750 four was at the time. To produce a fairly technically advanced motorcycle and then sell it at a cost almost one third less than the competition was a huge accomplishment and from a competitive standpoint very difficult to overcome. Yes if the British companies had invested in more R&D they might have stood a chance, but how do you develop a completely new product and sell it for less than the competition when the competition took all of the margin and then some away. Particularly when your labor costs are significantly more. Had they done that they would have been done sooner because the return on investment would have been negative.
We can rip Norton, and the British Motorcycle Industry to death but I would not have wanted to make the decisions back then. The world was changing back then...and there are many industries that were effected. The old world order changed and no training or experience could have prepared people for it. It's easy to second guess after the fact, because we have the entire history to tell us what "should have" or "could have" been done...they didn't and the bleeding happened very fast and they couldn't stop it.
You constantly rip Norton management for the failure...but the history shows that the actual decline happened some years sooner. Sales of British motorcycles were fairly strong for a number of years after WWII. The public liked the British bikes particularly in the US. The recovery after the war comes into play as many of the motorcycle factories were destroyed. Yes they should have invested more, but there were many new bikes produced into the 60's and some big failures particularly smaller displacement engines trying to compete with the Japanese.
The biggest problem was how revolutionary the Honda 750 four was at the time. To produce a fairly technically advanced motorcycle and then sell it at a cost almost one third less than the competition was a huge accomplishment and from a competitive standpoint very difficult to overcome. Yes if the British companies had invested in more R&D they might have stood a chance, but how do you develop a completely new product and sell it for less than the competition when the competition took all of the margin and then some away. Particularly when your labor costs are significantly more. Had they done that they would have been done sooner because the return on investment would have been negative.
We can rip Norton, and the British Motorcycle Industry to death but I would not have wanted to make the decisions back then. The world was changing back then...and there are many industries that were effected. The old world order changed and no training or experience could have prepared people for it. It's easy to second guess after the fact, because we have the entire history to tell us what "should have" or "could have" been done...they didn't and the bleeding happened very fast and they couldn't stop it.
- Joined
- Dec 3, 2012
- Messages
- 3,727
dennisgb said:
Which if I recall correctly was the same year the DOHC Kawasaki Z1 idea was conceived and ready for public release in 1969 but Honda trumped them with the CB750.
Without stating the obvious there is a major difference between looking forward to the future and looking back on history.
For the folk who think vibration was a non event,may I suggest drilling a hole in each isolastic tube and pumping Devcon into the void until full,that should induce a quick dose of reality once set,then take a ride on a dead stock 1978 Honda CBX/6.
- Joined
- May 27, 2013
- Messages
- 1,112
Time Warp said:
Thanks for posting this. I looked all over for this. I saw references to a Yamaha engine but couldn't make the connection. It shows that the history is correct...the Commando already was on the market and the end was near when this "balanced" engine was designed.
Yamaha's XS750 and XS850 were very fine motorcycles. Three cylinders. Vibration problem solved. I've owned three, 3 cylinder motorcycles. A Trident, a XS 750 and a K75RT. When it comes to smooth running you can't beat a 3 cylinder. I would imagine an inline six cylinder is smooth, as well. Never had the pleasure of riding one.
Come to think of it, I once owned a 3 cylinder air compressor.
Come to think of it, I once owned a 3 cylinder air compressor.
- Status
