Forum

[Chris Tindal]

Thanks for the input, especially Norm for easing my mind!. I was secretly hoping someone had another explanation but I expected the worst. I guess its a winter strip down and investigation.

[John M]

Chris if I understand your post there is rust coming from the top of the front down tube where it is brazed into the headstock casting. If this is the case then I would be concerned that the brazed joint is starting to fail. I think your frame may need specialist help.

[Chris Tindal]

John M yes that's the joint. Not having an engineering background I don't know how the joint was originally brazed, how did they do it from the inside?

[John M]

I have seen photos of frames, not necessarily Royal Enfield, being assembled by heating them in a blacksmith's furnace. Quite how they do It I'm not sure as I've no experience of brazing.
I think that your priority should be to take this area back to bare metal and asses the condition of the joint, the rust could be a sign of a crack forming.
There must be some specialists for this type of frame as most vintage frames are assembled with cast lugs and I wouldn't think that there would be too much work involved in a repair.

[grunda 12]

good advice posted here on this thread ,although people guessing on how much work would be involved in the repair is dubious ,and i think the repair would be costly ,i saw a report on a SPECIALIST firm in a bike mag the other month and i think that its quite involved this type of work so lets not fool ourselves as there are a lot of major factors involved in metal work its not just a case of glueing and ungluing BEWARE!

[Mark M]

Chris, brazing is a process where the parent metal is heated hot enough for the braze rod (usually a mixture of brass and tin,) to melt and flow into the joint. It's effectively a high temperature solder. This process is aided by the addition of flux paste which helps keep the metal parts free of oxidization and acts as a path for the molten braze to flow along. It makes a very strong and vibration resistant join. The cast iron malleable lugs are usually pinned together before brazing to prevent movement during the process. This pin, usually tiny, must be removed to separate the joint. They are often hard to find! Your problem doesn't sound too severe, (I've seen it before,) drying and Wax-oyling will probably be ok but a strip of the forks and a look inside the headstock with a bright light and a mirror will put your mind at rest. An unusual point on these pre-1956 frames is that the front downtube is slightly tapered to the bottom and consequently will be very hard to replace! I had some repairs on my 1953 500 Bullet frame done by Percival Brothers and Webb, part of the Autocycle group in Dudley. Very slow but very good, they even had the original frame drawings! You have my email if you need more.
REgards, Mark

[Chris Tindal]

Thanks Mark, I needed some words of reassurance and I'm glad you've seen it before. I'll be striping down soon to have a good look.

[Chris Tindal]

I meant stripping the bike, not me! My erratums are getting more common (need an edit option)

[John M]

I do know that you can get crack detector sprays that are designed for testing industrial components. This type of spray may help you test the joint once it's down to bare metal. With a bit of luck it will be a flaw in the joint that has been there since it was made.

[Alan R]

Hi Guys -------------- I'm with MARK M on this one, having been trained to braze/ Bronze weld etc within a Marine environment---- then later on BR, MoD and now self-employed. I think the fire-brazing of frames that JOHN M refers to was because Oxy-Acetylene sets were not as readily available as they are to-day....I seem to remember the factories of the day having very large , town-gas fired torches used in conjunction with a hearth full of red-hot coke.... By pre-fluxing a well-fitting joint it's quite possible for the liquid braze spelter to flow, by capillary action, into parts of that joint which are not accessible directly from the outside...You can see this feature quite clearly in model steam locomotive boilers being "Silver Soldered" together.. Please take a look at this}-----http://www.mainsteam.co.uk/articles/silversoldering.htm ---and this}--- http://www.technologystudent.com/equip_flsh/acet6.html -------- note:- a)Ideal for steel/cast iron jointing and b) Flexible joint in frames..... There is a remote possibility that De-Zincification can take place in certain circumstances if the Brass filler rod has been used (most unlikely IMHO within the motorcycle environment)....However, bearing in mind that the "Redditch years" eg 1955 is coming up to nearly 60 years ago, plus you have some frame activity that under any circumstances cannot be described as -- normal --- then I would agree with those that recommend a "strip and search" procedure, if only for your own peace of mind.