Bike Forums

Bike Forums (https://www.bikeforums.net/forum.php)
-   Classic & Vintage (https://www.bikeforums.net/classic-vintage/)
-   -   A very tiny mid 1970s Motobecane - Italian Crank Swap (https://www.bikeforums.net/classic-vintage/1238346-very-tiny-mid-1970s-motobecane-italian-crank-swap.html)

CriticalThought 09-08-21 09:38 AM

A very tiny mid 1970s Motobecane - Italian Crank Swap
 
Yet another project....

I picked up this ultra-small early 1970s Motobecane Nomade for my son. I have some parts that I think would look great on it and hop it up a bit, all in keeping with the C&V spirit of course (though I have some time as he's too small to ride it at this point).

I'm hoping to use this equally tiny Gipiemme 115 crank but that means switching from cottered to square taper. That's always interesting, especially on a French bike, but in this case I think even more so given the size of the bottom bracket.

I took a quick look around online and didn't see anything off the shelf (or otherwise) that would make it easy. My current thought is maybe just have a new shaft machined to my specifications and just use the existing bottom bracket.

Curious if anyone has any other thoughts?

Or if anyone has run into this before? (ha ha.. I know, I know... but it never hurts to ask, right?)




https://cimg8.ibsrv.net/gimg/bikefor...005e03d9b5.jpg


https://cimg4.ibsrv.net/gimg/bikefor...297397298a.jpg


https://cimg1.ibsrv.net/gimg/bikefor...ffe31018eb.jpg


https://cimg0.ibsrv.net/gimg/bikefor...42b547be3a.jpg


https://cimg9.ibsrv.net/gimg/bikefor...b098b5644b.jpg


https://cimg2.ibsrv.net/gimg/bikefor...513e43d701.jpg


https://cimg3.ibsrv.net/gimg/bikefor...d41056586d.jpg

C9H13N 09-08-21 09:49 AM

Phil says they make cartridges for a 63mm wide shell. Thatís only 1mm off on either side from yours. The Phil cups are shoulderless so youíll be able to tighten it just fine.

CriticalThought 09-08-21 09:58 AM

Oh really? Thanks a ton for that info C9H13N ! I'll check those Phil ones out. That would be a really nice solution... especially if the threading matches. :)

thumpism 09-08-21 10:18 AM

Just try a new spindle with the existing cups. It'll probably work.

I had a little 500A Flandria like that but never messed with the crank.
https://cimg1.ibsrv.net/gimg/bikefor...8fcb631b6c.jpg

CriticalThought 09-08-21 11:57 AM

Very cool bike thumpism ! Thanks for sharing that pic. Mine's even smaller (450A)... I really need a picture of it with my Grand Jubile to give a sense of how small it is.

I haven't seen any 63mm or even close, cartridges online that could possibly work (threading issues aside).

I think you're right that just looking for a square taper spindle might be my best bet. I found this one for about $12... and for that price I might as well order it even if I can't get dimensions & specs in advance.

https://cimg3.ibsrv.net/gimg/bikefor...d0715913a3.jpg

CriticalThought 09-08-21 01:36 PM

Well, it turns out I have a 122mm square taper Nervar spindle kicking around from another project. Even looks like the cups are the same size and if I'm lucky, the threading is the same (though I guess I don't need the cups).

The obvious issue is that the races on the spindle are much closer together on this tiny bike. They're about 52mm apart on the tiny bike spindle vs about 60mm apart on the Nervar square taper one.

Not sure if I have enough threading and offset to play with in order to account for those 8mm.

I think I'll give mocking it up a shot, just to see how far off things are and how much room I have to play with. We shall see...


https://cimg4.ibsrv.net/gimg/bikefor...6c39a9fa0c.jpg


https://cimg9.ibsrv.net/gimg/bikefor...237b739eb1.jpg


https://cimg7.ibsrv.net/gimg/bikefor...44a2f025c9.jpg


https://cimg6.ibsrv.net/gimg/bikefor...b756f6ac16.jpg



And.... a couple of bonus pictures because why not?

https://cimg5.ibsrv.net/gimg/bikefor...a72a6c5e6e.jpg


https://cimg6.ibsrv.net/gimg/bikefor...612b68e60b.jpg

oneclick 09-09-21 08:38 AM


Originally Posted by CriticalThought (Post 22221259)
They're about 52mm apart on the tiny bike spindle vs about 60mm apart on the Nervar square taper one.

Not sure if I have enough threading and offset to play with in order to account for those 8mm.

Use a pair of (or more sufficient to add up to) 4mm freewheel spacers - metal ones.

Mr. 66 09-09-21 10:08 AM

The Nervar, I don't think that's going to work. The race spacing and tapers are closer to Stronglight and Campy thin cup spindle length.

Maybe a reagular Campy spindle would work with thin cups.


All times are GMT -6. The time now is 02:59 PM.


Copyright © 2021 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.