What is a CMF Penton

[BrianTaylor]

I see that some of the posters refer to a CMF Penton can someone fill me in on what it stands for and secondly..i am in the process of restoreing a 75 125 six day and i noticed that all the welds on it (from factory ) are very sloppy with lots of splatter etc. I am grinding them smooth but am I the only one that has this "Austriansloppysplatten " thks bt

Brian Taylor

[Rocket]

CMF  Chrome Moly Frame
Rocket

 

[Frank]

Brian, You really shouldn't grind welds out, specially in a structural situation. Because production welds are done so quickly there is usually little gas coverage and the best part of the weld is the envelope or "skin" where the grain structure is not interupted by the shrinkage that takes place during cooling. Also the "tails" or welds that continue beyond the end of a gusset are very important at defusing "stress risers" (areas where stress is focused)
My '77 frame is very thin material and even a slight scratch in a stress area will cause a failure..Frank

 

[Doug Wilford]

Frank, nice answer to the posting.   It leaves no doubt that you are a professional in your trade.  Thanks, we will need your advise from time to time.

 

[Frank]

MIG and TIG welds are "filled" with the same material. usually a 70-80 K tensile material with some additives. Mig is shielded with a mixture of gasses that are not quite completely free of oxygen. TIG uses argon which is usually almost completely free of oxygen so in a direct comparison with the same amount of added material a TIG weld would be better. Specially on 4130.
The only real problem lies in removing the old weld and dealing with the contamination inclusions without further tramatizing the material. If you can remove the old weld without harming the base materials that is a good step. The second problem is the old weld may be full of porosity, slag or some sort of contaminant. TIG will not deal with this junk well. also a TIG weld is much smaller (done properly) and an area may exist outside the area of the TIG weld where the material has been effected my the trauma of the original weld but now is not covered with the new clean TIG weld. I personally do not remove welds and replace them unless they are cracked. (usually tubes fail not welds) for vanity it can be done but there is a good chance that the contaminants will reek havoc and cause the other mantioned problems. If you are committed to this procedure try perging the frame with argon and using a E-70S6 filler the "s" number is for silicon that has a fluxing property. Be shure to run the weld past the end of the stress area in the case of the gusset and be sure to remove as little weld as you can.. Frank

 

[BrianTaylor]

Bob no i didnt go wild i cleaned up all spatter.. then i ground all welds where it was a glob and above the basic weld.... of all the bikes if have restored( Rokon Hodakas Huskies) the Penton welding on this frame  (original )is truly terrible ....the structural integrity has not been changed ..it just looks a whole lot better bt

Brian Taylor

[Rocket]

I remember in the advertisements or magazine articles, all the CMF frames were stress relieved after they were welded.  If the frame is rewelded now, isn't that going to create weak spots without stress relieving again?
Rocket

 

[Frank]

stress relieving is certainly not a bad thing though it sort of went out of fashion when folks started using E70-SX wire for filler instead of 4130. Hey! Ihad a great idea..find someone with a pulse control TIG machine, clean the welds with a wire wheel and just go over them with the pulser on, you can get the texture repaired without risking the tubes.. Frank

 

[Gavin Housh]

Rob, I too was witness to the DeCoster crash at Livermore. The story we got was that Suzuki had been playing around with head tube angles and rather than making entire frames with different head angles they would grind out the welds and change the angle then reweld it. This supports Franks statement about too much trama in the frame tube adjacent to the weld. The weld is almost always stronger than the surrounding metal, and the heat affected zone adjacent to the weld is most susceptible to failure. Rewelding over an area that has been welded before only increases the chance of a failure. In DeCosters case this was almost fatal. The front end of his bike broke completly off while jumping the 10 ft. high ski jump at Carnegie motor cycle park. The riders would come down the straight away at 50 mph. and then launch off the ski jump when Rodger landed his front end broke off sending him face first into the concret hard sun baked adobe dirt. Without the full face helmets of today his face was severely lacerated and brusied. To the spectators it appeared he was dead! They flew in a helicopter to get him to the hospital. The race had to be restarted and this all took lots of time. Once the race began again some spectator decided to roll a truck wheel with tire and rim fully inflated down from the top of one of the steep hills that Carnegie is famous for. The wheel went into the crowd taking out people as it went. Again the race had to be stopped and the injured had to be transported to the hospital by ambulance. This left no ambulances for the racers and that meant no restart untill the ambulances came back. This all took more time. I remember leaving in the long shadows of late afternoon feeling what a terrible day. I still ride the blue grooved hills at Carnegie, and during the summer most of the local riders stay away untill first rain. The area of the Grand Prix track is now unrecognizable from the way it looked that day that riders like DeCoster, Wolsink, Lackey, Weinert, Smith, Semics, Howerton, Mosier, Pomeroy, Sun, Stackable, and West rode there but it seems like yesterday to me. Thanks for the memory Rob. Keep the rubber side down. Gavin

 

[Frank]

Back in the "old days" (not sure who's) 4130 tubing was first fillet brazed into airframes, racecars, bikes. The tubes were heated red hot, brazed then set by the door to cool in the breeze till they were ready to handle. Later when TIG became the rage, helium was used as an inert gas (rather than argon) and 4130 filler was used. Things started failing and folks figured that the fact that the frame was not heated red hot was leaving stress in the structure, causing the problems. Then in later years softer filler was used, the gas was switched to argon we also found that helium caused an "angular regraining" like safety glass when it fails. So with the new wire, better machines, better gas and cool things like purging and gas lenses the stress releiving just faded away. Some race car guys still do it. To answer the question annealing is in a sense stress revieving. 4130 comes in three grades, Heat treated, normalized and annealed. virtually everyone uses normalized and the need to stress relieve simply does not exist anymore. Thanks for the story on De Costers crash. I got to go to Saddleback for a race in the early 70's and got a signed card with a picture of the "man" layed flat like no man of that day..what a stud!