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+--- Thread: Design Disadvantages of the CB1100 (/showthread.php?tid=5507)
RE: Design Disadvantages of the CB1100 - thessler3_imp - 03-13-2014
All inline 4 engines have good primary balance (2 pistons up and two down simultaneously) but inherently bad secondary vibration. Secondary vibes occur at twice engine speed and create a high frequency buzz.[/size] I believe the CB1100 has a single balance shaft. Some other Hondas, like the Blackbird had two, which is a better solution. However, pistons go up and down and balance shafts rotate, so they only reduce secondary vibration, not eliminate it. By the way, most 4 cylinder bikes have cylinders that are separate from the crankcase, not cylinders bored into the block. Also, parallel twins can have several configurations, like Triumph's 360 degree crank with both pistons up and down together, Honda's earlier 350 & 450 have 180 degree cranks with one up and one down and the Yamaha Tenere with crankpins at 90 degree separation. I have studied vibration for years and the smoothest engines are straight sixes, boxer sixes and 90 degree V-twins of smaller displacement. In my opinion, any other engines would be better served with rubber motor mounts, even if it adds weight.
RE: Design Disadvantages of the CB1100 - Mick65_imp - 03-14-2014
The early Norton Commandos were indeed rubber mounted, if my memory serves me well, they were smooth, Nortons from the 60's, The Atlas were very bad for vibration.
Flat 6 Goldwing is superbly vibration free..
Vibration is always top of my list when buying a new bike...
RE: Design Disadvantages of the CB1100 - Red Mist_imp - 03-14-2014
(03-14-2014, 01:10 AM)Mick65_imp Wrote: The early Norton Commandos were indeed rubber mounted, if my memory serves me well, they were smooth, Nortons from the 60's, The Atlas were very bad for vibration.That was the "Featherbed" frame.
Flat 6 Goldwing is superbly vibration free..
Vibration is always top of my list when buying a new bike...
RE: Design Disadvantages of the CB1100 - the Ferret - 03-14-2014
Actually RM the featherbed frame came out in 52 or 53 long before the Norton Commando. It was a good handling designed frame designed for racing I believe. The isolastic frame with the rubber mounts replaced the featherbed frame and came out on the Commandos around 1967, the year before I graduated High School.
RE: Design Disadvantages of the CB1100 - Mick65_imp - 03-14-2014
You used to shim the swinging arms to adjust side play, I can remember calling them "Rubber Bands"
RE: Design Disadvantages of the CB1100 - Capo - 03-14-2014
Thessler3, great first post, and thanks for the science behind it all! Triumph also engineers in some dissonance with the 270 degree version of the vertical twin used in the Scrambler and cruiser variants of the Bonnie. Done for 'character' along the lines of Honda twisting the timing on two of the CB1100's cylinders, I suppose. As for the Atlas, I can attest to it's vibratory nature, as it powers my Norton P11, which is a Matchless Reynolds scrambler frame. It is hard to describe the level of vibration, and hard to imagine that journalists of that era described it as a 'mild and acceptable.'
And correct, the rubber mounting came with the 'Isolastic' frame of the Commando, not the Featherbed.
RE: Design Disadvantages of the CB1100 - the Ferret - 03-14-2014
Anyone who has ridden a British 500 single from the 50s can attest to the OH MY GOD THIS THING VIBRATES, as if all the motor mounts were loose, and the realization that anyone who actually raced one of those shaking beasts was a SUPER HUMAN.
The I 4 like the CB 1100 may not have perfect or secondary balance even with a counter balancer or two, but in comparison, they are silky smooth.
RE: Design Disadvantages of the CB1100 - thessler3_imp - 03-14-2014
Thanks for the compliment CAPO. Note that the new Norton has a 90 degree crankpin separation. So does the Husqvarna Nuda (now discontinued). They sound like Ducatis when running. I once owned a Norton Combat Commando with the isolastic suspension. It was a bit like a rubber mounted Harley in that the engine shook a lot at idle but was smooth at highway speed. I am thinking of buying a CB1100 and confirmed it has a single balance shaft running at twice engine speed geared off the crankshaft. It also appears to have rubber grommets on one of the rear engine mounts. Suzuki has done this before too to help quell vibration into the frame near the footpegs. I am very sensitive to vibration and have studied it quite a bit. In line fours are hard to get smooth over about 5000 RPM. I currently own a '73 Ducati 750GT and that 41 year old motor is quite smooth.
I once restored a mid-sixties BSA 441 Victor. It was indeed a paint shaker and would also kick back violently when trying to start it. The all-time vibrator I have ridden was a friend's 1956 Harley '74, which would vibrate your feet right off the floor boards at 70MPH. My '66 Triumph Bonneville would go through light bulbs every month or so when the filaments would get vibrated to an early death. Smoothest I have ridden - a CBX six, a Gold Wing six and my restored 73 Ducati 750GT on which you could balance a quarter on the crankcase when it was running - no exaggeration. It now has replacement pistons and is not quite as smooth as it was originally. My Foggy Monster with 916 engine was also pretty smooth, but not as smooth as the 750GT.
RE: Design Disadvantages of the CB1100 - flynrider - 03-14-2014
I was cruising down the freeway last Sunday when I noticed I hadn't bothered to shift into 5th (as usual). I was turning 5K rpm in 4th and that feels normal to me, since that's what the CB750 does in 5th at 75 mph. When I shifted into 5th and the rpm dropped to 4200, I noticed that I actually felt more vibes in the bars than I had at 5K. I thought it was a bit strange, so I shifted back and forth and it definitely seemed shakier at the lower rpm. Maybe that's why my brain so often forgets to shift up from 4th gear.
I used to own a lot of twins with 360 cranks, so vibration was just a normal part of motorcycling. When I took my first ride on an I-4 bike ( a Kaw Z-1) I was stunned. I never knew a motorcycle could be so smooth. In fact after I started it, I had to double check the tach to verify that the engine was running. I don't think I'll ever go back.
BTW, the shakiest bike I've ever ridden was a Yammie XS650 twin that was converted to a "twingle". The cam was modified so that both cylinders would fire simultaneously. Interesting bike, but it couldn't be kick started by anyone under 250 lbs. and the electric start would only work if you hooked a car battery to it. The guy that modified it didn't think of adding a compression release
RE: Design Disadvantages of the CB1100 - the Ferret - 03-14-2014
I've had 3 of the Yamaha 650 twins, a 73 TX, a 79 XS and an 81 XS Special. I obviously have a soft spot for them. Bought the 73 brand new. Yes they vibrate. At redline they would blow these little round instrument bulbs. Used to keep a handful of bulbs in my pocket and rerouted the sockets so I didnt have to remove the instruments to fit em. On the centerstand you could rev them up and they would walk across the floor. Still smooth as silk compared to an old British single. If you ever get the chance to ride one of the Brit bikes do it, you'll see.
Also had 3 harley Panheads 49, 56 and 57 and yes at high speed your feet would just walk off the floorboards. (and 2 harley Sportsters 59 and 94 which would make your hands itch and go numb at 55 mph and above)
Looking back at it, no wonder I think I-4s are so smooth
