Cutting RGS swing arm down to fit 180 frame

mcnicol

mcnicol

Hero member
Location
Safety Harbor, Florida, USA
My crankshaft problems have appeared while I'm trying to do my wheel swap with 25mm rear axle. I was just about ready to start fitting my modified swing arm when an RGS swing arm appeared on eBay and I won it (even for not too bad a price, but shipping made it  :o. Still, RGS swing arms NEVER appear in the US, at any price).
Anyway, I took the swing arm (and the "original" one) over to my mate the machinist and asked him to cut the bearing tube down to suit a 180 frame. He said he doesn't have any way to clamp it on his mill, and is asking for suggestions for machining out the bearing housings so they're round, the right diameter, the right depth, and in line.
Anyone got anything to offer?

Ken
 
Other than clamping the workpiece up in the mill and clocking it parallel and concentric to the machine spindle, no.... maybe you got to look for a more imaginative machinist.  ::)


  Keith.
 
Ken,

I milled the ends off squarely and fitted shorter needle bearings in the remaining bore.  They hold up just as well as stock items.... need replacing every couple of years.

piet
 
I found bearings that would exactly fit in the RGS swingingarm when I fitted one to my 180, although you need the two 1mm thick spacers that live behing the bearings as standard.  Think it was 25mm depth after cutting (less the 1 mm spacer so I put 2 x 12mm needle rollers in there, but I couldn't swear to it.  Local machine shop lopped off the ends of the tube no problems, it was a straightforward conversion. 

Reggie
 
if he has a milling machine and an imagination then there is no issue
I can think of at least 3-4 different ways to mount it in my milling machine to do the job correctly
so it appears to me that one of these items above is missing  :o

find a different machine shop


 
Well, my engineer mate did manage to work out how to do it and has cut down the RGS swing arm to the same width as a 3c swing arm AND bored for original length bearings. And milled the axle holes for a 25 mm axle and welded on tabs for the brake torque stay for an underslung carrier. At a price ???...
Anyway, now he needs to know how long the combination of the middle bearing spacer and the two outer hardened bearing inner races should be, so he can cut the inner spacer down to the right length. Failing that, the internal dimension of the frame where the swingarm attaches would do. He's also going to make a set of plastic washers to go between the end of the swingarm and the frame; could somebody please rat around in the junk box and see if they can find a thickness measurement for these?

Ken
 
215mm is the total width of the two bobbins and and spacer tube, the plastic washers are around 2.5mm but it is probably safest to install you swingarm axle assembly and take a measurement as their exact size will be determined by what width he has machined your RGS swinger too.

  Keith.
 
Cosi

I have to admit, I'm a little bit concerned about what will happen with a 120 swing arm on a manly Jota. Piet has the same setup and he seems to be able to keep its behaviour under control, or maybe he just uses the "don't ask, don't tell" approach. As for me, what my swing arm does in the privacy of its own home on its own time is entirely up to it. Just as long as it's ready to blow off any 120s that come our way (that could be seen as an unfortunate choice of terminology, couldn't it :D)

Ken
 
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