Pace RC200 F8 headtube repair
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Wold Ranger
Old School Grand Master
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Temperature
Not sure on the temperature, but I'll make enquiries, I believe it's to even up the hardness of the Alloy throughtout the whole bike, as heating just the welds, causes a gradient of temperatures reducing as you move away from the heat source. This differing degrees of temper, adjacent to each other can cause the cracking, as the metal then flexes at differing rates.
It's maybe interesting possibly to you but, I'm currently refurbing a Pace 250T, which I believe was the last of the square tubed frames and they had altered the basic design in areas where they had problems in the RC classes.
Obviously it was designed to withstand the rigours of trials and DS/Street, but it has gussets under the chainstays and top tube, ring reinforced BB shell, Oversize tapered head tube and the top and down tubes are braced behind the head tube. The "tubes" are also thicker.
Many manufacturers of Aluminium frames say it is essential that top and down tubes are joined behind the headtube, to prevent flex at the BB, as this is where the stresses are directed to over the bumps, hence the common place that they cracked.
If you look at most modern ally frames, they all now do just this.
Not sure on the temperature, but I'll make enquiries, I believe it's to even up the hardness of the Alloy throughtout the whole bike, as heating just the welds, causes a gradient of temperatures reducing as you move away from the heat source. This differing degrees of temper, adjacent to each other can cause the cracking, as the metal then flexes at differing rates.
It's maybe interesting possibly to you but, I'm currently refurbing a Pace 250T, which I believe was the last of the square tubed frames and they had altered the basic design in areas where they had problems in the RC classes.
Obviously it was designed to withstand the rigours of trials and DS/Street, but it has gussets under the chainstays and top tube, ring reinforced BB shell, Oversize tapered head tube and the top and down tubes are braced behind the head tube. The "tubes" are also thicker.
Many manufacturers of Aluminium frames say it is essential that top and down tubes are joined behind the headtube, to prevent flex at the BB, as this is where the stresses are directed to over the bumps, hence the common place that they cracked.
If you look at most modern ally frames, they all now do just this.
Well I picked up the RC39 forks from Bowsho on here last monday for my RC300 build but I couldn't wait for the 300 to be finished before I was able to use them so I've chucked them on the 200 for now and I love 'em so much they are staying on the 200 and I'm on the look out for another set for the 300 
Also, I finally got to use the Hope Head Doctor that came with the headset as it fits inside the steerer on the RC39's but not the RC36's and I've got to say I'm really impressed with it. I had heard bad things about them coming lose all the time but I went to Glyncorrwg on Saturday and didn't have one problem with it over the 20 odd miles we did, so much easier to fit than a star nut too.
Here's a few pics from Saturday too
Is that a bottle of lucozade in your pocket or are you just pleased to see me
Also, I finally got to use the Hope Head Doctor that came with the headset as it fits inside the steerer on the RC39's but not the RC36's and I've got to say I'm really impressed with it. I had heard bad things about them coming lose all the time but I went to Glyncorrwg on Saturday and didn't have one problem with it over the 20 odd miles we did, so much easier to fit than a star nut too.
Here's a few pics from Saturday too
Is that a bottle of lucozade in your pocket or are you just pleased to see me
I used an angle grinder with a solid grinding wheel to shape but couldn't fit a jubilee clip to use as a guide as the top tube is in the way. Yeah it's not perfectly straight but it'll do for me02gf74":3015miev said:
wow - that cam out surprsingly well:
did you grind that all by hand?
valve bouncer
Retro Guru
Wow mate, that turned out a treat. I've also had my bike repaired at a motorcycle shop in similar fashion with 2 plates going over the cracked section. In my case it was where the rear shock attaches to the frame. That was 14 years ago and still going strong so I'm tentatively calling it a job well done! I however haven't got it all pretty looking because I like the industrial look it gives the bike..............or I'm a lazy bastard.
fun at fiftyish
Retro Guru
Hi ,I have spent thousands of hours dressing welds,at work,and realise just how difficult it is to get it right using a grinder freehand.That is bloody fantastic!.I admire your determination and attention to detail,not easy to get it right.I love the bike and can appreciate how gutted you must have felt ,after owning it for so long to discover the crack,I can also be like a dog with a bone at times,my non bike mates tell me "It's just a bike",,But we know better...Top marks dude!
Mark.
Mark.
Thanks for the kind wordsfun at fiftyish":ocbuhmr4 said:
That first moment when I picked up the angle grinder and turned to my mate and said 'Right, I'm going in' was a heart in mouth moment I can tell you, but slowly-slowly-catchy-monkey proved to be the best plan of attack, probably took me about 4 hours all in all and many tea breaks to build up courage after each grinding session 
