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1968 swinging arm

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Hi all

Has anyone had problems with early swingarm twisting?

I have a 1968 commando that I am doing a full rebuild on and have done a cotter pin conversion on the swingarmm pin and I am wondering if I should put some sort of bracing one the swingarm itself.

it has done 17000 miles and I have measured up the swingarm and it all looks good but have seen the later swingarm Is more heavily braced just aft of the pivot. Is this a weak point on early ones?

Thanks Dean

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yes the early ones do flex i clamped my gearbox cradle in a vice with the swingarm attached and passed a bar through the wheel spindle slots i was alarmed at how easy it was to flex so i gusseted the swing arm at its pivot point as a late commando i also made some sheet metal pressings top and bottom the full length of the arm when i was done i could hang my weight off the bar without the swingarm flexing i also did the cotterpin conversion and added an extra isolastic under the gearbox i do get a bit carried away sometimes but its the best handling commando i have ever ridden regards nick

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Many riders in the early 70s noticed that when following behind a Commando, the rear wheel always seemed to lean slightly to the right of vertical. This was at first put down to power of the engine pulling the engine cradle over because of the Isolastics. However, even at slow speeds the problem seemed to persist. I remember one of my Commando owning mates actually asking a Norton dealer if the swinging arm was twisted and being firmly told 'no way'. 'can not happen....it is too strong'. So obviously there was no need for the Factory to add strengthening gusset plates from 1973 onwards.

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back in the 80s a friend of mine had an 850 interstate with a sidecar everyone said DO NOT COM a commando but she took no notice and fitted the chair anyway i think it was a monaco,but to follow that outfit and see the back wheel twist and squirm was quite interesting to say the least !! ,,,,,nick

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Hello Nick,

Have you any photographs of your swinging arm and gearbox modifications. My 1968 frame has been heavily modified at the steering head end to stop the two down tubes breaking and remove the need to add the horizontal tube but I have not touched the swinging arm apart from new isolastics. Thanks. Harry

Previously nicholas_marshall wrote:

yes the early ones do flex i clamped my gearbox cradle in a vice with the swingarm attached and passed a bar through the wheel spindle slots i was alarmed at how easy it was to flex so i gusseted the swing arm at its pivot point as a late commando i also made some sheet metal pressings top and bottom the full length of the arm when i was done i could hang my weight off the bar without the swingarm flexing i also did the cotterpin conversion and added an extra isolastic under the gearbox i do get a bit carried away sometimes but its the best handling commando i have ever ridden regards nick

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Thanks all for the info. Big thanks to Nick for the pics. Do you remember what thickness steel you used? Will be adding some gussets ot the swingarm similar to later models. I have modified the frame to have the extra tube under the main backbone after finding cracks in the top of the down tubes. Also have vernier isolastic a and I'm planning to fit a better headsteady.

On that does anyone know of a headsteady that will fit under a fastback tank? As I live in the Middle East if I have to return any parts it cost me big money. At the moment thinking of doing a Mike Tagliere style as I can get all the parts and do it myself here. Any thoughts?

Dean

 


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