Author Topic: Barrel Fin Repair  (Read 1518 times)

Offline Stu55Flash

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Barrel Fin Repair
« on: 21.07. 2010 23:29 »
There is a post on this 3 years ago.

Has anyone further experience of arc welding a new fin piece in place using high nickel rods. My barrel is pictured below. I have bought some rods and was going to have a go at welding in a piece off a car brake disk.  The plan is to heat the barrel in the oven then place it in box with vermiculite from the garden centre to keep the heat in. Then spot weld the repair piece in using the arc welder.
There's a piece about this in Classic Bike Guide (Jul) but it does not give details. It just says it was welded into place no bother it does not mention preheating.

Has anyone experience of this?

Stu

"Keep a distance from lady "L" drivers in cars. Some are not mechanically minded, are slow to acquire road sense, an are apt to panic..." The Pitman Book of the BSA Twins.
Golden Flash Plunger 1955, Francis Barnett Falcon 67 1954, Ferguson TEA Tractor 1951. Looking for another project!

Offline trevinoz

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Re: Barrel Fin Repair
« Reply #1 on: 21.07. 2010 23:35 »
Stu,
          My mate usually does these jobs for me. he makes a piece of fin from a "sacrificial" barrel and brazes it in.
If you go this way, check for bore distortion after.
Trev.

Offline bonny

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Re: Barrel Fin Repair
« Reply #2 on: 22.07. 2010 00:07 »
i worked in large engineering works before , in the fabrication area mainly and i welded all sorts of metals and without doubt i HATE welding cast iron , brazing is the way to go for you in my opinion , thats the way i repaired my own barrels and when the joint is dressed and painted , its invisible.   

Online muskrat

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Re: Barrel Fin Repair
« Reply #3 on: 22.07. 2010 10:57 »
I think to arc weld cast you need stainless rods and yes to preheat.
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
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Offline bonny

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Re: Barrel Fin Repair
« Reply #4 on: 22.07. 2010 15:26 »
I think to arc weld cast you need stainless rods and yes to preheat.
Cheers

yeah , the last time i priced rods for cast iron i had to sit down as i got dizzy and a nose bleed.

Offline A10Boy

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Re: Barrel Fin Repair
« Reply #5 on: 22.07. 2010 20:07 »
About £1.50 each off ebay
Regards

Andy

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Offline Goldy

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Re: Barrel Fin Repair
« Reply #6 on: 22.07. 2010 20:07 »
I welded a fin on the cast iron head of my A10. I purchases 5 cast iron electrodes off E bay and welded without any pre heating. That was 1 year ago and I have had not problems with it at all. I  think you will find that modern cast iron rods are much better than the ones used years ago.
56 A10 Golden Flash - Restore, ride, relive.                                          
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Offline A10Boy

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Re: Barrel Fin Repair
« Reply #7 on: 23.07. 2010 09:27 »
I got a pack of 5 off ebay, I have an old a7 barrel with missing fins and am going to cut one off and experiment fixing it back on before i try a repair on a good spare set of A10 barrels that only need a small repair to a bottom fin. I was thinking of pre heat to 200 c, then stitch welding nice and slow.
Regards

Andy

1958 Super Rocket
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1974 Kawasaki Z1a
Yam XJR 1300

Offline bonny

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Re: Barrel Fin Repair
« Reply #8 on: 23.07. 2010 11:52 »
i am amazed , the last time i priced cast iron rods they were mega-bucks , that was in a local engineers suppliers though and probabily pre-fleabay, can you use a cheapy ac plant to use these or what ?

Offline A10Boy

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Re: Barrel Fin Repair
« Reply #9 on: 23.07. 2010 13:06 »
I hope so.........
Regards

Andy

1958 Super Rocket
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1974 Kawasaki Z1a
Yam XJR 1300

Offline A10rocket

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Re: Barrel Fin Repair
« Reply #10 on: 23.07. 2010 20:10 »

I've welded quite a few "thinish" things cast iron with cast iron arc rods.
Although I never pre heated the job, only weld for 8 - 10mm at a time maximum, leaving a couple
of minutes between welds for the heat to disapate. If you try to go all the way in one go it'll start cracking.

Probably pre heating the barrell would help things, certainly wouldn't do any harm.

Ken.
1961 Super Rocket

Offline MG

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Re: Barrel Fin Repair
« Reply #11 on: 23.07. 2010 20:25 »
The cast iron rods I use are nickel based and suitable for AC and DC, never heard of any other suitable alloy.

Welding is easy enough, but it is important to pre-heat the barrels (250-250°C, kitchen oven at max. temp.) and only do stitch-welding and no continuous seam, as this would bring in too much heat into the fin, thus leading to a high temperature gradient and finally causing cracks, doing more harm than good.
It is advisable, if possible, to carefully knock on each stitch with a small hammer carefully immediately after welding to release internal stresses.
Let the barrels cool down very slowly after welding.
This way I welded two fins back on the barrels of my A10 with just a welding spot about every half inch or so. Grinding V-grooves in first makes for a good joint and less dressing work.

Brazing definitely is an alternative, but as applying much more heat is involved, I think the danger of distortion is higher, especially when working sclose to the bore. Doesn't matter if you do a rebore afterwards though.

Cheers, Markus

Ken was faster  *smile*
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Offline Stu55Flash

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Re: Barrel Fin Repair
« Reply #12 on: 23.07. 2010 22:17 »
I have 5 of the nickel rods off ebay as well. I will have a crack at it tomorrow and post a pic.

Stu
"Keep a distance from lady "L" drivers in cars. Some are not mechanically minded, are slow to acquire road sense, an are apt to panic..." The Pitman Book of the BSA Twins.
Golden Flash Plunger 1955, Francis Barnett Falcon 67 1954, Ferguson TEA Tractor 1951. Looking for another project!

Offline Stu55Flash

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Re: Barrel Fin Repair
« Reply #13 on: 01.08. 2010 14:08 »
OK finish this job today. "Spot" welded new piece off a Land Rover brake disk. Weld is not very neat but its a cosmetic repair really. It won't be noticeable once its painted and the head is in place. Process: Heat the Barrel in the oven in stages 50 deg at a time until max on oven. Ignore wife's hysterical screams about never being able to cook in the oven again and blue smoke in kitchen gassing the house out. Spot weld in places enough to hold in place not full welds. Put back in oven and cool slowly from max at 50 deg at a time each for 20minutes.

Stu.

"Keep a distance from lady "L" drivers in cars. Some are not mechanically minded, are slow to acquire road sense, an are apt to panic..." The Pitman Book of the BSA Twins.
Golden Flash Plunger 1955, Francis Barnett Falcon 67 1954, Ferguson TEA Tractor 1951. Looking for another project!