Hi Jim, it broke right across the end of the left hand journal. mind you the crank was almost 40 years old it did 16000 miles as a road bike and 4 seasons as a race bike , it was no stranger to 8 - 8,500 rpm ( I dont do that anymore).Did the crank break at the PTO shaft? or at the journal?
This is a poignant photo of my Commando Production Racer , First raced in 1976 as a converted 1974 850 Mk11a road bike , this picture was taken in 2013 having been de mothballed into service whilst waiting for my race bike to be completed , the poignant part is that this photo was taken 1min 14 secs ( next lap same place) before the crank let go completely destroying the engine : crank, cases, rods, cylinders, pistons, timing gears, timing cover &, primary cases. Sorry to say that the bike is still gatering dust in a dark corner of the garage along with a spare engine waiting for my upcoming retirement to give me the time to resurect it.View attachment 16725
Hi Jim, it broke right across the end of the left hand journal. mind you the crank was almost 40 years old it did 16000 miles as a road bike and 4 seasons as a race bike , it was no stranger to 8 - 8,500 rpm ( I dont do that anymore).
Hi Jim, it broke right across the end of the left hand journal. mind you the crank was almost 40 years old it did 16000 miles as a road bike and 4 seasons as a race bike , it was no stranger to 8 - 8,500 rpm ( I dont do that anymore).
The crank in that engine had been balanced to 78-80% for use in a seeley commando, it was balanced and polished back in the 70's ,I would suppose it was stress fatigue. My race Bike last year had a fault with the clutch retaining circlip and on two occasions on one lap the clutch gave way and the Krober rev counter went off scale ( thats 10,000 rpm plus) the first time I didnt belive it, on the second time I pulled up. Had me worried but with circlip replaced it was still runing ok.had it been dynamically balanced or do you suspect simple stress fatigue?
My 500cc short stroke Triumph would rev reliably to 10,500 RPM. The valve gear was polished and lightened. The cams had very long duration, very slow lift rate and less max. lift than normal Triumph cams. It also had a very strong one-piece billet crank and the longer Triumph rods. But I would not have thought a Norton crank would cop that without leaving a piston behind. After I built the Seeley 850, it sat unraced for 25 years because I'd seen what was inside it. - YUK ! - For what they are, the Commando engine is unbelievably good.A radius on the PTO shaft reduces breakage in that area but it won't help the journal. Dynamic balancing is good but not enough in your case. You need to put your reciprocating weight on a diet. But nothing will survive at 10,000 and I also think that much RPM is hard to believe - your valves would be in the pistons.
Well, the front brake photo contest was so much funthat I'm taking Jerry up on the challenge of posting another one. This time it's for pictures of racing Commandos. I'll try to make the rules clear enough that we don't get confused (right!). Winner is the one with the most votes at the end of 31 July. That should be enough time for everyone who wants to participate to sort out a picture and post it. Enter as many time as you want, but only one picture per bike and only one picture per post.
1. Must be Commando engine and frame, modifications allowed. No Seeleys, Rickmans, etc.
2. Must have been or about to be raced. Road racers, landspeed racers, hillclimbers, ice racers, flat track, motocross, trials, etc., as long as it's racing.
3. Poster must be personally involved in some way with the bike, owner, rider, bulder, mechanic, sponsor, pit tootsie, etc. Edited to also include photos taken personally by the poster, even if no other involvement in the bike. Still no fair just posting a picture of something you saw online.
4. Vote for it on whatever basis you like, photo quality, originality of design, racing history, blingness, or just plain coolness.
Ken
Well, the front brake photo contest was so much funthat I'm taking Jerry up on the challenge of posting another one. This time it's for pictures of racing Commandos. I'll try to make the rules clear enough that we don't get confused (right!). Winner is the one with the most votes at the end of 31 July. That should be enough time for everyone who wants to participate to sort out a picture and post it. Enter as many time as you want, but only one picture per bike and only one picture per post.
1. Must be Commando engine and frame, modifications allowed. No Seeleys, Rickmans, etc.
2. Must have been or about to be raced. Road racers, landspeed racers, hillclimbers, ice racers, flat track, motocross, trials, etc., as long as it's racing.
3. Poster must be personally involved in some way with the bike, owner, rider, bulder, mechanic, sponsor, pit tootsie, etc. Edited to also include photos taken personally by the poster, even if no other involvement in the bike. Still no fair just posting a picture of something you saw online.
4. Vote for it on whatever basis you like, photo quality, originality of design, racing history, blingness, or just plain coolness.
Ken
Ian should be in the other frames competition? Your not running a Commando frame lol are you?Hi
I guess this is only open to VIP members? Pity. I have a classic racing sidecar with a Commando engine installed!
Hi
I guess this is only open to VIP members? Pity. I have a classic racing sidecar with a Commando engine installed!
Pics of Tony Smith in this thread https://www.accessnorton.com/NortonCommando/thruxton-motorcycles-commando.22906/Has anybody got a picture of Tony Smith on the Thruxton Motorcycles Commando? He and the bike deserve to be mentioned here. I watched him and Pete Davies on the Slater Bros. Laverda Jota slugging it out during the Avon production series in the 70's, but don't have any photos unfortunately.
Thanks Ken (and Chris). I missed the bit about the engine being mounted in a Norton frame! Mine obviously isn't, although it is a race engine and is raced at circuits (when the madness ceases!!!)I don't think that's the case. As I understand it, putting up a new photo contest is restricted to VIP members, but any forum member can enter the contest. Just post to the thread and include at least one picture of your bike. Jerry's software automatically picks up the first photo in your post and adds it to the contest list. If I'm wrong about this, I'm sure someone will cheerfully correct me.
But as Chris already pointed out, this is the contest for Commando racers, i.e. Commandos that are raced, not just something with a Commando engine. The other contest I started is for Commando engines in other frames.
Ken