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RADBMX.CO.UK  |  Technical & Reference Section  |  Tech and Restoration  |  loop tail ripper seat tube replacement (warning lots of pics)
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Author Topic: loop tail ripper seat tube replacement (warning lots of pics)  (Read 1100 times)

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Offline sawzall

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heres a how to guide on replacing a seat tube on a loop tail ripper

1)heres seat post before repair
2)remove most of seat post with an airsaw or hacksaw
3)then remove the remainder of the post from top tube and rear triangle, again use an airsaw or hacksaw,making sure
you dont remove to much!!!! its best to use a file to do final shaping

4)this is what it should look like once filed but keep checking new tube for fit
5)then its the bottom bracket to sort,i found the centre (inside old tube) and drilled and tapped a 5mm thread in frame then using a belt sander or grinder remove whats left of seat tube and old weld,i masked surrounding area with gaffer tape to prevent damage to frame
6)i made this jig out of junk from the garage to hold frame together,it fits on rear drop outs and headset,then by tightening nut at the front it pulls frame together,this will also keep frame together when being welded,as heat generated by welding can pull and distort frame out of shape

7) if you get tube from donker its slightly longer so it will need cutting to correct length,then i filed bottom of tube for snug fit to bottom bracket,then fit tube in frame,i tapped the 5mm thread in bottom bracket so i could use some threded bar (about 60mm longer than new seat tube)this screws in bottom bracket then using a nut and repair washer tighten on top of seat tube ,this will keep everything square
8)as said before heat can distort frame so better safe than sorry ,i made these bottom bracket jigs out of a couple of old bearing cups and some large washers,i welded washers to cups and used a large nut and bolt to hold them together,once all the hard works done you will have to find a good welder,(note... make sure tube is in the right place)
9)once welded this is what it should look like

then remove jigs from frame all being well these should keep everything in the right place
British race frames and race clothing wanted

snav69

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Re: loop tail ripper seat tube replacement (warning lots of pics)
« Reply #1 on: May 10, 2007, 07:00 PM »
 :shocked:
Awesome job  :4_17_5:
You must have balls of steel to attempt that but the result speaks for itself  :daumenhoch:

Offline dwain dibbly

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Re: loop tail ripper seat tube replacement (warning lots of pics)
« Reply #2 on: May 10, 2007, 07:09 PM »
fantastic job :4_17_5:
i know now who to send mine to
if i knacker it up :daumenhoch: :2funny:

Paulo

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Re: loop tail ripper seat tube replacement (warning lots of pics)
« Reply #3 on: May 10, 2007, 07:29 PM »

Can't believe you're to casual over a huge job like that.  :10_2_12:

Looks really clean. Nice job  ;D

Offline Waxintaxin

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Re: loop tail ripper seat tube replacement (warning lots of pics)
« Reply #4 on: May 10, 2007, 07:34 PM »
You the man  :daumenhoch:

Quote
Can't believe you're to casual over a huge job like that

or the owner trusts phill with thier baby impicitly

Rich

dj_benice

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Re: loop tail ripper seat tube replacement (warning lots of pics)
« Reply #5 on: May 10, 2007, 07:36 PM »
Top Banana that man  :4_17_5:

Offline lazychubs

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Re: loop tail ripper seat tube replacement (warning lots of pics)
« Reply #6 on: May 10, 2007, 07:48 PM »
looking good and yep takes a brave man to cut it up lol
my mate used a nice size drill .just slighty over size and drilled the top bit out
then cleaned the welds up before welding the new tube in

Offline double chevron

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Re: loop tail ripper seat tube replacement (warning lots of pics)
« Reply #7 on: May 10, 2007, 08:21 PM »
Skilled Phil !

Great thread.
Thanks.

SaMAlex

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Re: loop tail ripper seat tube replacement (warning lots of pics)
« Reply #8 on: May 10, 2007, 08:35 PM »
I have looked into getting this done a tiny bit, is that right that the seat tube isnt a standard stock size bit of tubing? Its crazy if its not, did SE custom make every seat tube for their rippers, and if so, why did they make the Inside Dia smaller than everyone else?

Offline Steve P

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Re: loop tail ripper seat tube replacement (warning lots of pics)
« Reply #9 on: May 10, 2007, 09:01 PM »
Incredible ... some nice engineering you've done there Phil. Great job  :daumenhoch:

Steve

Donker

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Re: loop tail ripper seat tube replacement (warning lots of pics)
« Reply #10 on: May 10, 2007, 09:07 PM »
Sawzall, excellent job mate it makes my day to see another saved.

S&M Alex, if you did find stock material with a 13/16" bore, it would be a poor finish inside and there would be enough variation in size (batch to batch) giving a potential poor fit with the seat post tube, this would probably lead to cracking again. do a google for stockists and if you find some please let me know as itll save a load of time drilling that stuff out. i have 2 of these tubes left if anybody needs one.
 :Great_Britain:

SaMAlex

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Re: loop tail ripper seat tube replacement (warning lots of pics)
« Reply #11 on: May 10, 2007, 09:15 PM »
I can see that a stock tube might not be as good as one made to measure, and Im sure that your tubes are way way better because you make them, but I thought that THE reason most bike, esp ones from the 80s, chose its tubing size was because it was a stock size. Its def the case for most Cro-mo frames, forks, seat posts, ect. That is partly why oversizes seatposts and headsets, and one piece fork stear tubes took so long to be avalable, cos no-one could aford to custom make tubes. Maybe PK seat tubes were an easy size to get in the 80s, in the US? and they were probably still a bit crappy too.

Can you give me the OD and ID of the tube, and the ally grade, cos I talk to tubing and metal suppliers quite a bit and it might be worth asking a few of them.

Offline lazychubs

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Re: loop tail ripper seat tube replacement (warning lots of pics)
« Reply #12 on: May 10, 2007, 09:17 PM »
i reckon they welded a seat post into em bitd
instead of a seat tube lol

Donker

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Re: loop tail ripper seat tube replacement (warning lots of pics)
« Reply #13 on: May 12, 2007, 03:17 PM »
From the ones ive measured the O.D. is usually 1" plus a few thou.  obviously its a stock 13/16" bore. 6061 spec material which can the be heat treated to t6 spec if you can! the last batch i made were a 7000 series. as im sure you will know its difficult to but in small qty for fair prices so maybe you can find some at a good price with your contacts, this will save the time/cost to drill out the 13/16. we can only try!

Offline kdw712

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Re: loop tail ripper seat tube replacement (warning lots of pics)
« Reply #14 on: May 12, 2007, 03:34 PM »
amazing job
and balls of steel to start chopping a ripper up

def worth it in the end though  :daumenhoch:
cheers Kev
{ wanted : "Red Haro Handle" brake lever link to my trade post }

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