sheddle

I'd rather like to try this because a 53/42 crank does not lend itself well to climbing for a relative out-of-shape guy who hasn't cycled in four years prior to the latest bike purchase.

Realistically I should probably get a different crank until I grow into the SR one. Out of curiosity, how much does the derailleur max capacity matter, is it only really an issue if you attempt to use the "bad" gears like granny/small cog?

degan

Someone hurry up and bust out their quad setup.

thook

right. small/small or big/big are the issues if you're exceeding the capacity. in either case, you could wreck and/or break parts. worst case...the world comes to end..if the gestapo doesn't admonish you into irrevocable shame first

what's the bolt circle diameter on your crank? if you don't know, then what crankset do you have?

Nemosengineer 

Looks like this, also known as a super spacer.

thook

made from a single speed crank with a doublizer so you can add a triplizer that's a quadruplizer

JohnDThompson 

Yeah, I have a few of them myself, both the triple version and double version. The triple version is drilled for three different BCDs: 144mm for the outer two rings, and 102mm or 74mm for the inner ring. I haven't seen too many ring options for the 102mm BCD, but the 74mm BCD is widely available.

Depaso

Off topic, but is it possible to know what bottom bracket size the Avocet triple / Ofmega CX triple is mounted on?

JohnDThompson 

The spindle measures 124mm.

HTH…

Depaso

Thanks man!

noglider 

I saw one in a video somewhere. I think the guy is in Finland or Scandinavia.

sheddle

It's the Campagnolo Strada Record crank with the flute arm. Velobase lists a BCD of 144mm, but I'd have to actually check myself on my frame.

The 53 ring is fun enough on tailwinds and downhill false flats that I'd like a triple over a compact if possible.

I'm also going to try to see if I can get a Suntour with a 28-cog to see if that can get me up short steep hills, but that's stretching the limit of the RD.

thook

thanks!!

thook

144 is likely accurate, then.

i've got a 7spd suntour alpha 13-28 i've hemmed and hawed on using, but decided not to. the teeth and pawls are in excellent shape. it just has some surface rust on the cogs from being in my shed that could very well be cleaned. you can have it for shipping or maybe we can trade, if you want to do that. just calculate what the capacity would be and let me know

thook

so, i really started out wanting a simple way to do this and now i've got one thanks to all the input here. this idea will eliminate potential inaccuracies or mess ups going "freehand" on it. plus, i don't need to rig up any press fixtures

i'm going to make a template on my drill press using some high density polyethanol board i got for making strut spacers. trace out the chainring onto the board marking all points to be drilled, use a larger than 74mm hole saw on the press to make the template disc, drill the 5 bolts at a pilot hole size, drill the disc center to run a bolt through to clamp the disc to the inside of the crank, and then hand drill through 5 pilot holes of the disc and into the spider. this set up will act as a guide for my bit/s and tap. i just haven't decided what the final bolt size/pitch will be as i still have to decide on fasteners. if i can easily enough find some kind of applicable stud, that'll do the trick. otherwise i'll go with the hardware in the link depaso provided

image of the backside of my crankset stolen from the web. nice area for a granny, no?

sheddle

I appreciate the offer- the local co-op is swimming in Suntour freewheels right now, and I always like supporting those guys, so I was going to hit them up. But thanks!

thook

sure thing!

sheddle

(the actual long-term project is to replace the old SR parts with a new silver Potenza 11 set but that's several hundred dollars down the line, haha)

thook

so, where does the campy strada fall into all that? iow's, you're curious about modifying an SR crank or the campy?

sheddle

It's more about getting a short-term solution to make it more suitable for steeps until I actually splurge on a new grouppo. Realistically a better solution would probably just be finding a suitable old triple at the co-op that can get put on the frame, but I do love the look of the fluted Strada.

mpetry912 

Bob Freeman has a jig to do a Campy crankarm with great precision.

He has done many - prolly 100s

Finding the adapter hardware is up to you however.

Mark Petry
Bainbridge Island, WA USA

thook

okay, i get. i hope something comes around for you, then. you'll have to get a longer BB spindle, though, when you go with a triple. so, just make sure the spindle taper and crank match

t_e_r_r_y

i didn't read through this thread with a fine tooth comb so someone may have mentioned this already, but if you're drilling on the same plane as the existing sprocket holes, just work out the difference between the stock bcd and the granny gear bcd and measure down that distance for your hole placement.

here's a high quality illustration to help show what i mean

if you do this for each hole, your granny gear should be centered with no wobble.

thook

i had thought of that. and, yes, that would enable centering the ring to the spindle. the other concern for me is getting the holes drilled straight so the hardware goes in/through straight so the bolt holes on the ring line up spot. so, i've decided to make this disc/template/guide thingy. otoh, could this be even more simple and easy? probably. hmmm...i think i'll review things once again. thanks!

t_e_r_r_y

i missed out if you have a drill press or not. if so, you can mark the holes and then use some bolts/washers/spacers/whatever in the stock sprocket holes to work as stand-offs to rest the crank arm on the drill press table to keep it level/supported while you drill the holes.

here's another terrific illustration to show what i mean. this is the side view of the crank arm with some bolts n junk spacing it off the table to work as supports/keeping everything level

Salamandrine 

I think you should use this as an excuse to get an indexed rotary table. That way after you finish drilling your new granny gear holes very precisely, you can continue on with this productive hobby by drillium-izing all your chainrings...