Another cracked Peashooter!!

Last Tuesday I had another thrash up to the Scottish boarders. It was all going so well until the exhaust changed note on the overrun. When I looked down the silencer had cracked right through the radiused section where the connector pipe joins the main body. Bugger! I rode on to the next small town, where a get me home repair using a couple of jubilee clips & some steel strips was carried out.
As this is becoming a rather expensive habit I am looking for suggestions (again). I should point out that this set of Peashooters was made using a thicker wall connector tube (16 gauge/1.5mm) as a special order by Brituro.
The system is mounted perfectly with no stress or misalignment & the motor is as smooth as any Commando I've ever ridden. Short of mounting the silencers to the engine cradle I'm at a loss for what to do next.

Martyn.

W/o redisign of the mounting plane best I have come up with is not clamping the header fixed in the muffle but semi loose sliding fit and waisting the rubber mounts so they can move easier than loading the exhaust system and last longer too. I had a rusted set part apart at front of muffler but after the above looser mounting now the internal baffle tubes breaks loose in a few seasons to rattle again. Face it Commandos were only made as short lasting stop gap till Norton could come up with something more sensable none of us could afford, If exhaust too rigid mounted you may get buzzed in waves till it relieves itself cracking.

From memory i think the Brituro silencers are welded at that point

the welds are then ground off prior to heat treatment and chrome which weakens the silencer at this point

Thin steel should have a 1/2 mm gap and filled with tig weld. it's no use surface welding and then grinding off! this leaves no strength to the joint..seen it a few times ,

Had a look at that joint on the last set I got from RGM and the transition from shallow to steep taper is not weld but looks like a pressing, previous ones were Campbells and then had the weld but not dressed. None of them have suffered cracks.

I've had mufflers crack in the same place. As stated above, I no longer tighten the clamp fully. It is just snug. Once in a while I need to wipe off some tell tale leak on the pipe at the clamp, but I haven't had a cracked muffler since. hth Frank

Thanks for the replies.
I think I will try fitting the silencer using silicone sealer & just nipped up loosely. It seems to be metal fatigue rather than down to the brazing cracking. When I spoke to Andover Norton they said they had not seen this problem much. The worst place for breakages is apparently near the head where the pipe is welded to the head stub. The pipes on my bike however, are about fourteen years old & still good.

Most exhaust system failures are due to incorrect mounting; more simply stated the systems are mounted with static stress. The header/silencer should fit with no initial stress, this greatly extends the life of all the components and makes the "weak" link the rubber isolating bushings.

When I mount new exhaust systems I snug the header, but leave just enough looseness such that it can be rotated, but doesn't wobble. Next, I slide the silencer, with snug (no tight) diamond shaped mounting plate, and see if it will fit on the two rubber bushings with out adding any stress. The header can be bent slightly in any direction (unless its stainless which react to bending pressure very poorly), the silencer based diamond plate has some tolerance, as does the Z plate based mounting plate that retains the rubber bushes. Using all the tolerances and adding a bit of bend should insure that your exhaust system has zero static stress. If, however, your ISOs are original (which most are), or are tired, than you'll find it very hard to fit a stress free exhaust, same type of issue if your frame is "tweaked' (rare).

It is also possible that the source of your silencers scrimped someplace, I can't say. Try another manufacturer or source and see if that makes a difference, especially if you mounted the system with no static stress.

Far from rocket science...

That is exactly how I fit my systems. The only stress involved is with my wallet. Also my ISOs are new A.N. types.