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Jevans
Joined: 07 Jul 2003
Posts: 8
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 Posted: Fri Apr 23, 2004 2:57 pm Post subject: Welding a solid non-isolastic Commando frame |
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Has anyone tried to transform the rubbery commando frame into a solid frame? I'm a vintage racer, and I'm really hampered by the rubber mounted swingarm. I've considered a Seeley or featherbed frame, but I'm currently thinking of modifying my Commando frame.
Dave
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illf8ed
Joined: 30 Dec 2003
Posts: 474
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| Posted: Fri Apr 23, 2004 4:29 pm Post subject: Isolastic frame |
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Dave,
Not sure how familiar you are with Commandos and their handling. Is handling why you ask about solid mounting the engine? |
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norbsa48503
Joined: 07 Apr 2004
Posts: 1034
Location: Flint, Michigan
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| Posted: Fri Apr 23, 2004 9:50 pm Post subject: Sloppy? |
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| Jevans go here and have a very good read explains everything. http://www.vintagenet.com/phantom/wsc.html a lot of work but still going to make everything live much longer. norbsa |
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Jevans
Joined: 07 Jul 2003
Posts: 8
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| Posted: Sat Apr 24, 2004 11:27 am Post subject: sloppy versus solid for racing |
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Hi all,
Yes, handling is the issue. I run my isos tight, and I have a nice Norvil head steady. I've contacted Kenny Augustine about blueprinting the frame too. It's a lot of trouble and expense to do that ($1k-$2k). The result I am sure would be an awesome handling bike for fast street riding.
However, in racing, there are fast transitions, lean angles, throttle use, and high speed dips that are never encountered even in the fastest street riding.
At each track I go to, I find 1 or 2 corners where the forces simply overwhelm the iso mounted frame. These are typically a fast transition from full lean one side to full lean the other side. Knee on the ground to knee on the ground. Usually between 80mph and 120mph. Examples: Turn 10 esses at Buttonwillow, turn 8A/B transition at Sears Point, turn 5 at Thunderhill. If there's a dip in the road (eg. Turn 3A at Sears Point or 6 at Laguna Seca) it's even worse. What I have to do in these turns is be suuuuuper smoooooth and baby the bike and not be WFO on the gas.
Top vintage racers all seem to be running Seeley or Featherbed frames if running Commando motors.
Buying a new frame and shipping to the USA would cost a little bit more than doing the whole isolastic blueprinting job ($2500). But that's not the entire expense as there would be new tank, oiltank, rearsets, etc that would be needed. 
Thus my though of either rigid mounting the swingarm or rigid mounting the entire engine, gearbox and swingarm. This would of course require changing the balance factor of the crank, but I'm in the middle of a new engine build, so I could do that easily.
If you look at the history of Commando racers from the Norton factory, by 1973 they were running a monocoque chassis (like a modern deltabox) with fuel and oil in the frame. The swingarm was rigidly mounted, and this supposedly was a huge step forward in rigidity and handling. The engine was still isolastically mounted because Denis Poore of Norton insisted upon it to have a link to the iso-mounted Commandos that they were selling for the street.
Dave
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norbsa48503
Joined: 07 Apr 2004
Posts: 1034
Location: Flint, Michigan
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| Posted: Sat Apr 24, 2004 2:36 pm Post subject: uniso |
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| Well than seems like the fastest and easyest means to this end would be to press fit in some Half inch pieces of lathe turned 6150 into the ends of the iso tubes that have some snug clearance holes for the motor mount studs. This would be best done with the frame blue printing so as to clean up the straightness. I would think that the large tubes of the iso brackets would give in strenth what they take in wieght. You could still run the gatours for the stock look. That will keepem guessing. norbsa |
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Jevans
Joined: 07 Jul 2003
Posts: 8
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| Posted: Sun Apr 25, 2004 7:27 am Post subject: nice idea |
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| That's a nice simple approach, and probably the most affordable. I was thinking of adding lugs midway along the bottom frame so as to have a 3rd mounting point for the cradle. |
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bill
Joined: 01 Jun 2003
Posts: 135
Location: Orlando Fl/Shady Valley Tn.
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| Posted: Sun Apr 25, 2004 1:27 pm Post subject: |
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I hope that you rebalance your motor if you make it a solid mount. I have also heard that a commando frame WILL break from the vibration if you solid mount the motor. this does not sound like a very good idea to me the commando frame is made from a light weight tubing and the swing arm is also not ridged enough.
bill |
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dynodave
Joined: 28 May 2003
Posts: 139
Location: USA
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| Posted: Mon Apr 26, 2004 2:52 am Post subject: |
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Last edited by dynodave on Mon Apr 11, 2005 5:19 pm; edited 1 time in total |
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norbsa48503
Joined: 07 Apr 2004
Posts: 1034
Location: Flint, Michigan
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| Posted: Mon Apr 26, 2004 4:09 am Post subject: |
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| There are poly bushings that are real stiff. You might try adapting very stiff bushings to see if you could fix the handling and keep the 20 lb frame. I don't know how much the good frames lb out but I bet it's more. An adventure like this alwas costs but poly bushings and several days of carful assem. shouldn't be to stiff. I have no dout that this this frame would give way if soild mounted but there may be room between the pounds and handling to make you able to compete. I would think that finding a fast way around the track might be harder if useing the fast guys with ridged frames as a riding example. You may have to break that mold as well. norbsa Can't win Can't break even Can't quit |
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Jevans
Joined: 07 Jul 2003
Posts: 8
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| Posted: Mon Apr 26, 2004 4:06 pm Post subject: breaking the frame |
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My plan had been
1. rebalance the crank to 80%
2. add stronger engine mounting tabs (the current ones, esp front, are too flimsy and will break)
3. solid mount the swingarm from the frame, not the cradle
I'm still investigating sources for Seeley frames. Roger Titchmarsh never answers his phone and has not faxed me back. Has anyone dealt with Barber Engineering in Norfolk? Any other ideas for sources of Seeley frames?
- Dave |
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Norton Commando Forum by Corporate Pages Web hosting using phpbb
The Unapproachable Norton Commando
At the end of 1967 the Norton Commando was announced.
The Norton Commando was greeted with a certain amount of scepticism because on first sight the commando appeared to comprise of the old Norton Dominator twin cylinder engine mounted at an inclined angle in a set of new cylinder parts.
It was not realized that the new Norton Commando Isolastic method of engine suspension damped out all engine vibration and produced a machine which had uncanny smoothness for a vertical twin. In due course the critics were silenced and the Norton Commando had the distinction of being regarded as the first of todays so called superbikes. There can be little doubt that the original design concept of the Norton Commando has proved correct, since comparatively few modifications of any real consequence have been made since production commenced during 1968.
Now nearly 40 years later Norton Commando riders like us are a breed of our own, and as far as we are concerned its still more fun to go for a blat on the old Norton Commando, and fast. As a Norton Commando owner and enthusiast, my goal here is to promote and give credit to those who keep the Norton name going.
It is more deserving to give credit to the Commando itself, for after all these years it continues to be respected. The original Commando designers like John Favill are those who deserve the credit for developing this incredible motorcycle.
The Norton Commando Roadster and Interstate of the late seventies, never died. Although the Norton Villiers factory dispersed the tradition lived on. Today Kenny Dreer in the USA is developing the new 952 CC Norton. What a great looking bike this is, and its engineering is still based on the original layout. It will be interesting to see how the new 952CC Norton does in todays tough motorcycle market. One thing is for sure, I would own one if I could afford it.
