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Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

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Old 01-03-06, 12:38 PM   #1
Jim Brantley
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Who has a jig to drill extra holes in spider to add a granny gear to a 130 double?

Don Gillies, who maintains www.vintage-trek.com, posted that it is possible to drill extra holes at a 74 bcd in a square taper 130 spider in order to mount a granny on a road double. He said there are people with jigs who will do the drilling but he did not provide any names or addresses. This sounds like an alternative to buying a TA Tripleizer at $90. Does anyone have anymore information? Jim
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Old 01-03-06, 12:50 PM   #2
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It's not something that your local machine shop could do??

Also, where are you, geographically? Maybe that'll help people give more pointed direction.

One other idea: gillies@cs.ubc.ca . That's Don (taken from r.b.t.)
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Old 01-03-06, 02:45 PM   #3
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Use your new granny ring for a drill guide.
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Old 01-03-06, 04:41 PM   #4
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I started to convert the Sugino crank on my Schwinn World Sport to a triple back in 1998. It already had blind holes cast in for the third ring. There were complications! Drilling the holes to the proper size for tapping. I was able to do this on an industrial drill press with a drill press vise at work. I consider this neccesary to keep the holes at 90 degrees to the plane of the chain ring. Finding a 8mm x.75mm tap! Had to order one through a friend who runs a machine shop. Then, had to grind the point off the tap so it would cut threads sufficiently deep in the spider. Now, to keep the threads perpendicular to the plane of the chain ring!! Back to the drill press and vise, put the tap in the chuck and TURN IT BY HAND to the proper depth, repeat four more times. Now that all the hard work was finished, I bolted the ring to the spider only to find the spacing between the middle and small ring are to close. I never did get access to the material or lathe to make spacers. In the end, I bought a Sugino triple crank arrm. It doesn't match the original, but, you only see one side of the bike at a time!!

Have a skilled machinist lay it out and do the work. The ring will be concentric with the crank and you'll have fewer grey hairs. I'd have never attempted this if the original crank did not have the blind holes cast in the spider.
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Old 01-03-06, 05:01 PM   #5
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Thank you Takara 14. I certainly do not need more grey hairs. It does not seem to be an operation that is often done.

Last edited by Jim Brantley; 01-03-06 at 05:02 PM. Reason: misspelling
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Old 01-03-06, 07:11 PM   #6
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A better alternative is to simply buy a drive side triple crank arm to fit your bottom bracket spindle (Though it's likely you'll need a longer spindle for adequate clearance on the right chain stay and/or to ensure sufficient swing from your front derailleur / it might bottom on the seat tube).

In the old days there wasn't a great selection of readily available alternatives so it was necessary to try all manner of fixes, but, from 30 years of experience I can say that I've tried most of them and few were worth the effort, either in cost or function.
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Old 01-03-06, 07:24 PM   #7
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There are so many well made triple cranks, both new, NOS and used available at every price from nearly free to absurdly expensive, there has to be something available that's better than ruining a double.

takara14's description of what it takes to do it properly should tell anyone it isn't nearly as easy as it seems.
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Old 01-08-06, 02:52 AM   #8
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this is the sort of thing that you are after

http://www.jimlangley.net/wrench/tripletool.html

but I think that it would be easier to buy a new crank
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Old 01-08-06, 06:22 AM   #9
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It's easier and cheaper to just buy a new crank. That's why it's hard to find someone to do it.
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Old 01-08-06, 08:01 AM   #10
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Quote:
Originally Posted by mentat6059
this is the sort of thing that you are after

http://www.jimlangley.net/wrench/tripletool.html

but I think that it would be easier to buy a new crank
Note that the tool is a one-of-a-kind and was made to convert Campy cranks back when Campy did not make a triple of any type. Those days are long over and triples are easily available. Buy the right thing.
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Old 01-08-06, 08:10 AM   #11
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Buy a used triple on e-Bay and sell your double. Other than shipping, it is a "break-even" financially. What you propose isn't worth the work or time.
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Old 01-08-06, 07:20 PM   #12
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Quote:
Originally Posted by mentat6059
this is the sort of thing that you are after

http://www.jimlangley.net/wrench/tripletool.html
WAY COOL! A righteous and elegant way to do it
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