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PostPosted: Mon May 13, 2013 9:09 am 
retrobike rider / Gold Trader
retrobike rider / Gold Trader
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Joined: Sat May 09, 2009 11:46 pm
Posts: 3924
Location: East Riding of Yorkshire
Given mixing the caustic soda with water is exothermic it should heat up a bit and react quite quickly with the aluminium when you add it, so most the sodium hydroxide will have reacted within a few minutes, so I found I needed to keep adding fresh.

This is a video of my first attempt at it if it helps: http://youtu.be/-dYnSVVDxrE

And there's some more info on this thread:

viewtopic.php?f=1&t=207241&start=15

Though there are other helpful threads on it too if you do a search.

In general, rack mounts are there on the lower models in the range. My Karakoram Elite has them, but they're not there in the catalogues though.

I don't really know anything about disk mounts, but I'm sure someone who does will help.


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PostPosted: Wed May 15, 2013 3:08 pm 
Dirt Disciple
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Joined: Tue Nov 20, 2012 6:41 pm
Posts: 53
Location: South West
I see, I guess the code on mine may be upside down and the year code could be 89? Or we're frames all 1" steerers back then? Mine looks to be 1.1/8" which is good as I have no 1" steerer tube forks handy.

As for the searpost, for me it gets hot for around 30 minutes then it goes cooler after that, even tho the mixture is still fizzing and bubbling a little. I'm dissolving a lot of seat post however, I've got around 1ft of seat post that needs melting.

I think I need to drain what I have in there and put some fresh in, that video is good also, the camera guy didn't expect those fumes :D

Anyway, I think I may have a go at adding some disc mount myself, a friend has offered to lend me their welder and being a steel frame things like this are easier to DIY.


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PostPosted: Wed May 15, 2013 4:01 pm 
retrobike rider / Gold Trader
retrobike rider / Gold Trader
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Joined: Sat May 09, 2009 11:46 pm
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Location: East Riding of Yorkshire
I think, as Fluffy said, that's the end of the code. Need to give it a bit of a clean up if you're desperate to work it out, or maybe try fixing a piece of paper over it with masking tape and using a soft grade of pencil to produce a rubbing out it?

I don't think it's as early as '89 or '90. Looking at the shape of the rear dropouts and double eyelets I'd definitely say '93 onwards. Plus, the head tube logo isn't right for an earlier one.


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PostPosted: Wed May 15, 2013 4:20 pm 
Gold Trader
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Joined: Tue Jun 28, 2011 4:22 pm
Posts: 1935
Location: Berlin
I have no idea, what GT frame this was. But it does have a GT-Backplate, yes? If no, it is no GT.

In any case: this seems to be a low end frame. Why not weigh it? It will probably be close to 3kg - even without paint. I would not spend too much money on this for a sandblast and respray etc. You can get much better GT frames with orginal paint for around 50 quid. Especially early 90s GT are famous for there nice paintjobs. Just browse through the 91 and 92 catalogue.

Rackmounts aren't necessarily a clue. My 92 Psyclone - GTs premier steel frame - had some. They just used the same dropouts as on the Bravado, Avalanche and Karakoram. However, the better frames usually only had one mount on each side; the cheaper ones had two.

Regarding the fork size: basically all the models from the early to mid ninties took a fork height of only 395mm.


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PostPosted: Sat May 18, 2013 3:36 am 
Dirt Disciple
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Joined: Tue Nov 20, 2012 6:41 pm
Posts: 53
Location: South West
Great info, thanks, especially concerning the forks. It does have the GT logo behind the seat post (which has finally dissolved) so it's def a GT.

I got this frame for free so I don't mind spending a little money on it as I have enough spare bits to build it up as I have recently cracked an Alu frame and this frame will be a good replacement. I'm gonna see how it rides first, then if all is good then I'll get it powder coated, I know a place locally that should do it for less than £50, otherwise as has been said I can get a better condition frame for less.

I will weigh it, it does seem pretty heavy and around 3kg or seems about right. Having the double eyelets on the rear is good as I'm planning to use this as a mile munching commuter, so having a rack and mudguards is a bonus here. Now the seat post has melted I'm gonna see how easy it will be to weld on a rear disc mount while still allowing a rack to be fitted.


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