Engineering compromises leading to exhaust threads stripped (2012)

Re: Engineering compromises leading to exhaust threads strip

Of course it was a design problem, but it was one that afflicted virtually every British bike in the post-WW2 period. I had trouble with exhaust rings on my 1953 BSA A7. In the case of the Commando, it inherited the Atlas engine, which was derived from the Dominator 600 and the 650SS. and they all had the same exhaust pipe rings.

Where the Commando suffered was from the impact of the Isolastics. The allowed the engine "pod" to move relative to frame-mounted components like the exhaust system. I think the freedom of movement was plus or minus 3/16". Since the exhaust is tied to the frame, the exhaust nuts had to absorb that movement. A good fix (but ugly) is to put a short length of flexible SS exhaust hose between the first couple of inches of the pipes out of the head and the downstream, frame-mounted components.
 
Re: Engineering compromises leading to exhaust threads strip

Hehehe the more lore I learn about Commandos the more I think it the inspiration for Spragthrope Dog Kennel innovations spoofs. Wes and I deal with rough roads so pipes are like tires and chains and oil though we get a couple weld repairs before total crumble at front. I waist the rear cushions to let them give more than headers to be sacrificed more often than the headers. I am rather familar with a number of sizes and materials of flexable exhausts marine to gen set rooms to state its still too in reasonable length to take up the iso motion with road loads ontop engine hops. When compact tiddy appearance a non issue then a expanded ball or pancake shape of rubber used. Oh yeah I quit snugging muffler clamps downs for some slippage relief and can remove pipes with muffler left on mounts and back again. Soot builds up to help seal and dampen clang.
 
Re: Engineering compromises leading to exhaust threads strip

Engineering compromises leading to exhaust threads stripped (2012)
 
Those look good. Since I opted to keep my little shorty mufflers and run them respectably loose my exhaust headers stay tight... Being painted black the soot doesn't show. When I go back to a new system your idea shall be implemented.
 
Those header clamps won't keep the threads from blowing out if the ex nuts get loose - and the nuts do loosen up from heat and vibration. Eliminate the ex pipe flange and the washers. Run the ex nut in as far and tight as you can (re torque when hot) with silicone on the threads instead of anti seize. Use silicone bronze to Braze a spring hook and a bushing to the pipe and hold the pipe in with a spring to a fin on the ex nut (add a smear of silicon to the bushing so there are no air leaks) - problem solved forever.

Engineering compromises leading to exhaust threads stripped (2012)
 
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Neat looking work you've done there, and a stellar idea... It has the appearance of being thought through....
 
Since converting my Commando to the Featherbed frame and hard mount engine I have never had any problems with lose exhaust headers since 1980, my header pipes where made for the motor and Featherbed frame with the headers and mufflers it only one mounting bolt on the muffler and flang nut and take each pipe and muffler off in one piece takes less than a few minute to take my exhaust system off.
I still have my original exhaust treads in my head and original flanges.

Ashley
 
"Since converting my Commando to the Featherbed frame and hard mount engine"
That's one way to solve the problem:cool:
 
Do you still have the fillings in your teeth? I ask because upon changing my ISO's I got them too tight at first and the bugger almost shook mine out..... More so than an old single cylinder Lister or Petter with the hand crank stuck on the crankshaft.
 
jbruney said:
Do you still have the fillings in your teeth? I ask because upon changing my ISO's I got them too tight at first and the bugger almost shook mine out..... More so than an old single cylinder Lister or Petter with the hand crank stuck on the crankshaft.
Click to expand...

I have all my teeth my motor has been balanced for the Featherbed and not many vibrations, a standard Commando motor is only balanced at 54% my motor is at balanced at 72% and runs pretty smooth, I am 61 years old and I built my Commando/Featherbed in the early 80s and it was a everyday ride till 6 years ago and I only have 3 fillings in my teeth lol.

Ashley
 
jseng1 said:
Those header clamps won't keep the threads from blowing out if the ex nuts get loose - and the nuts do loosen up from heat and vibration. Eliminate the ex pipe flange and the washers. Run the ex nut in as far and tight as you can (re torque when hot) with silicone on the threads instead of anti seize. Use silicone bronze to Braze a spring hook and a bushing to the pipe and hold the pipe in with a spring to a fin on the ex nut (add a smear of silicon to the bushing so there are no air leaks) - problem solved forever.

Engineering compromises leading to exhaust threads stripped (2012)
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Jim do you only run one spring up top or do you have two spring one on top and one down the bottom so it pulls the pipe evenly.

Ashley
 
Wonder why the idea of bronze exhaust header nuts did not come up. The coefficient of expansion of bronze is closer to aluminium than that of steel.
Any thoughts ?
 
Bronze nuts is what I run along with the final 2 torques when the engine is hot and never had an issue since.
 
Peter R said:
Wonder why the idea of bronze exhaust header nuts did not come up. The coefficient of expansion of bronze is closer to aluminium than that of steel.
Any thoughts ?
Click to expand...

They are most likely a good part to use in a stock head but not in a cylinder head with alu/bronze thread inserts. ?
 
My Bronze nuts are into a head with Mick Hemmings welded in aluminium alloy inserts.
 
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