Fabricated an adapter to run compact chainrings on vintage 130BCD/135BCD cranksets
 

Hello Everyone,

I wanted to share a solution that I came up with to run 110BCD 50T/34T chainrings on vintage five-arm cranksets. I fabricated an outer chainring that allows the 110BCD chainrings to bolt onto 130BCD or 135BCD cranksets. For my purpose I drilled for 135BCD for my vintage 9-speed Campagnolo Record 135BCD crankset. In order to maintain the chainline I used a 105mm ISO bottom bracket from Phil Wood in place of the usual 102mm Campagnolo bottom bracket. For Shimano 130BCD cranksets (or other 130BCD brand) you would likely want to have a bottom bracket with an axle 3-4 mm longer than your current one. The outer adapter plate I fabricated weights 186 grams not including the extra chaining bolts and extends the total Q factor of my Record crankset from the usual 145.5mm to 148.35mm. My chainline is 42.86 with the 105mm Phil Wood bottom bracket which matches well with the 41.86 distance of the center of the rear hub to the middle of the 9-speed cassette. To fabricate the adapter I bought a 4mm thick 7075 Zicral aluminum plate off of eBay for $35, an entry level drill press, a $20 CNC router bit, a 10mm drill bit for the chainring holes, and a set of metal files. After fabrication I used KHatfull’s protocol of polishing through wet sanding. This took me a very long time to make. I’ve never made anything like this before but I took my time and it came out like I had hoped. Lastly I sourced a Campagnolo Racing T rear derailleur and took off its medium/long derailleur cage and put it on my short cage Record Titanium 9-speed derailleur to accommodate the 34T front chainring and the Miche 29T rear cassette cog. The drivetrain operates flawlessly. My inspiration for the adapter was a photo of a Stronglight crankset. Below are photos of the adapter with Campagnolo 110BCD 50T/34T chainrings. I encourage everyone to make a compact chainring adapter to keep our vintage groupsets intact while having easier gears. Best,
https://cimg3.ibsrv.net/gimg/bikefor...24791cde13.jpg
https://cimg1.ibsrv.net/gimg/bikefor...657a14eda7.jpg
https://cimg6.ibsrv.net/gimg/bikefor...64a449622a.jpg
https://cimg8.ibsrv.net/gimg/bikefor...3f46d586e8.jpg
https://cimg1.ibsrv.net/gimg/bikefor...ae12180e47.jpg

Nice work!:thumb:

Looks good, and likely improves the chainline a bit as well.

Looks like the perfect side hustle to me.

Very clean... Excellent work...

A word of warning to any who may wish to do the same:

Do NOT use a drill-press to do milling.

I suspect that the op may have done this and got away with it ("entry-level drill press" and "router bit").

Here's why:
Most drill press chucks are mounted on a taper, the chuck has a socket, the taper sticks down from the drill shaft. This taper is not designed to hold when side-forces are applied. Milling (other than plunge) is 100% side-force.
If it lets go - and they do - there are lot of things that can happen suddenly, none of them good.

A much better solution would be to chain-drill the outline of what you don't want, cut it out with a hacksaw, and file to your line. It'll be quicker and you should still have ten fingers.

Dear oneclick,

Thank you for your message. I completely agree with everything in your post and I too was worried about those potential catastrophes. I used a 1/4” diameter 4-flute solid carbide end mill TiALN coated CNC bit exclusively for plunge drilling. I plunged drill overlapping holes in the aluminum plate to cut out the design. I used three C-clamps to clamp the aluminum plate to the base of the drill press before plunging. I ruined my first aluminum plate because the plate was not securely clamped to the drill press base and when plunging the 4-flute bit grabbed the surface of the plate and dragged it across the bit. I would secure the aluminum plate with three C-clamps, plunge drill a hole, loosen the three clamps, move the plate a few millimeters, clamp again, and then plunge again. I just looked at my adapter and estimate that I plunged/drilled 250 times to cut out the center star of the design and another 350 times to cut the outside. As I said in my original post this whole process took me a very long time to make. The adapter after drilling/plunge looked like a mouse had nibbled away the excess aluminum of the adapter. I then took a hacksaw bade, wrapped it in electrical tape, cut a 1/2” belt sander paper, and clamped the sanding paper to the taped hacksaw blade. I did this to file the inside and outside of the adapter to smooth out the mouse-eaten edges up to the Sharpie-drawn line of my design. Lastly I used a 1/4” diameter tungsten carbide burr cutting tool die grinder bit, and with a very very light touch to avoid scalloping, went over the areas I filed to smooth out the edges of the adapter. I was very afraid of a machining bit breaking under load so that in addition to taking it slow with plunging I also always used the following safety equipment: a face shield, racquetball glasses under the face shield, a respirator, heavy gloves with armor over the fingers, and a denim apron. The machining process throws up a ton of aluminum dust and splinters. Below are photos of the items I mentioned above. Please critique my technique as I do not want to get hurt doing projects like this. Thank you, Best,

https://cimg2.ibsrv.net/gimg/bikefor...bca47a475f.jpg
1/4” diameter 4-flute solid carbide end mill TiALN coated CNC bit
https://cimg3.ibsrv.net/gimg/bikefor...f51fa19fd8.jpg
The drill press with the three C-clamps
https://cimg4.ibsrv.net/gimg/bikefor...4b2f9344bc.jpg
The belt sander paper over taped hacksaw blade
https://cimg5.ibsrv.net/gimg/bikefor...4afaef3d07.jpg
1/4” diameter tungsten carbide burr cutting tool die grinder bit
https://cimg6.ibsrv.net/gimg/bikefor...50e382891c.jpg
The safety equipment

Below is a photo of an example of overlapping plunge drilling to cut out the design that was not included in my last post.

https://cimg2.ibsrv.net/gimg/bikefor...b869eb603c.jpg

Looks fine - why not use a plain drill bit, you'd get way more than that many holes from a decent one; and if your press has any appreciable amount of runout starting the hole (close to) where you want it will be less bother.

Thank you, oneclick, for evaluating my technique and reassuring me. If I ever make another chainring adapter I will try your suggestion of using a plain drill bit.

Impressive work!

Do you know much does it weight in the end?


Best regards,

DuraAcer

Hi DuraAcer,

Thank you, and everyone above, for the compliments on the adapter. Total additional weight at the end to run compact chainrings on my 135BCD Record crankset is 236 grams:

Chainring adapter itself: 186 grams

Five sets of chainring bolts and nuts: 45 grams

Five 4mm chainring spacers: 5 grams

Best,

That's really ingenious. Try making a few paper patterns of the ring you have so far and see if you can pare away at some of the excess metal to make it seem "airier" and less massive. That's a suggestion, not a criticism. Very good work!

Thank you, jonwvara! I appreciate your suggestion. The most material I could do away with and still feel that the compact chainring would not flex the adapter under power is in the photo below. The photo below is of a Rotor NoQ Aero outer chainring in 110BCD that I bought for another project. I used orange electrical tape to show the outline of the adapter. Everything in orange is the adapter. Everything in black would be the compact chairing (that is currently champagne color mounted on my adapter). If I ever get around to making another adapter then I’ll try this pattern to save some weight.

https://cimg5.ibsrv.net/gimg/bikefor...597341e107.jpg

You can probably remove more metal than you think, as stiffness is almost never a significant factor in bicycle performance. And, in those very specific instances where it does matter, at least as many problems are caused by things being too stiff as by them being not still enough. (In fact, I'd bet a 6-pack on more problems from excess stiffness.)

Basically, if it's a bicycle part and it's made of metal, if it's strong enough, it's stiff enough. (I've never heard of someone breaking a chainring.)

Looking at triplizer rings, which are kind of doing the same thing but in the opposite direction, they don't have any extra metal beyond what's required for the chainring bolts... could your design accommodate a similar approach?

There's a lot of smart thinking in this idea... if you make it pretty, you'll probably sell a bunch of them, because old cranks are, on average, prettier than new ones.

--Shannon

I recently came across a picture in a thread about a Schwinn? That had a "ghost ring" between the large and small chainrings. I assume its purpose is to smooth out the shift between rings. It seems like if you put your adapter ring between the chain rings it would give a lot of options to adjust the chainline and Q factor as well as function as a "ghost ring"

Yes, agreed. It takes less metal than one would think to hold a chainring together. Check out the image of this IRD triplizer, for example--much more open space than metal.
https://cimg6.ibsrv.net/gimg/bikefor...0bc87c5a26.jpg

Thank you Shannon! I appreciate your sharing your knowledge of chainrings and how little material you need and still have it stable. Based on what you said in your post then if you have a vintage 130BCD crankset then you could use a Porkchop BMX chainring that is already drilled for 110BCD and 130BCD and just remove the chainring teeth. To remove the chainring teeth you could use a bench grinder, belt sander, dremel, or other device. If on a budget or limited space you could cut a regular size sanding belt in half and clamp or nail that to a board or surface and drag the the chainring across it (this is super slow but something I have done and it works great). Unfortunately no BMX, or any other type of chainring, is drilled or could be drilled for 110BCD and 135BCD. In my research the only thing that came close was a Mojo chainring. Before making my adapter I experimented on a Mojo 44T 110BCD chainring by removing the teeth and drilling for 135BCD. The 135BCD drill holes had so little aluminum material left at the bottom of the hole after drilling that I didn’t feel comfortable using it. After exhausting all possibilities of using something in production that’s when I made my adapter from scratch.

https://cimg0.ibsrv.net/gimg/bikefor...e0c3f6d917.jpg
A Porkchop BMX chainring drilled for 110BCD and 130BCD. Just take off the teeth and you have an adapter
https://cimg2.ibsrv.net/gimg/bikefor...229dbeca0a.jpg
The Mojo chainring
https://cimg3.ibsrv.net/gimg/bikefor...a2a59e50c5.jpg
The Mojo chainring with the teeth removed and drilled for 135BCD. I did no polishing on this chainring
https://cimg5.ibsrv.net/gimg/bikefor...8df388559c.jpg
The Mojo chainring with the 135BCD drilling. There's so little aluminum material at the bottom of the hole.

Thanks Shannon! My job and my family keep me extremely busy. I have very little time to train, much less do any type of side hustle project. Ideally someone else, an individual or a company such as Orange Velo, would take the design and make an upgrade kit for vintage 130/135BCD cranksets. Hopefully the kit items would be in an aluminum finish that was similar to the patina of vintage cranksets. Selling an upgrade kit could include: the chainring adapter, the 10 chainring bolts/nuts, the 110BCD chainrings in silver, and the square taper 105mm bottom bracket. I could not find any 110BCD chainrings in silver color except for some FSA ones that were super chunky. In my fabrication the chainring bolts attaching the adapter to the 135BCD alone took me hours to file down with 400 grit wet/dry sandpaper to get the them to fit the crankset since I used long Sugino chaining bolts for all the bolts for a more uniform look. The long Sugino bolts were a perfect size for the 110BCD portion of the adapter since they go through the adapter, two chainrings, and a 4mm spacer. Those same bolts needs to be filed down significantly to just go through only the adapter and the crank arm tab. That sanding down of the five chainring bolts took my hours. If there was an upgrade kit as I described above I would have spent some money to use my own vintage Campagnolo crankset and have compact gearing.

Thank you bark_eater! I did a Google image search and a Bike Forum search and couldn’t find the Schwinn ghost ring. If I see what a ghost ring looks like then I can try to see if I could somehow come up with a way to fit an adapter between the chainrings. Every design I have come up with has not been able to fit between the chainrings. One such design was using a 90s Sim triplizer 135BCD/74BCD chainring I found on Ebay. I cut out the spider of the triplizer and clamped it to the position of where the outer chainring would sit on the crankset. I then ran the 48T outer chainring in the space/position where the inner chainring would normally sit on the crankset. I ran long Sugino bolts through 12mm chainring spacers that I found from a fabricator in the UK (the spacers are not for cycling but they were the exact dimensions of chairing spacers). These long bolts connected the 74BCD holes on the spider to a 32T 74BCD chainring through the 12mm spacers. This system required a 108mm ISO Phil Wood Bottom Bracket and pushed the Q Factor to 151.78mm. I rode my bike with this setup for a few hundred miles and it worked. Ultimately I wanted another solution with a shorter Q Factor and better aesthetics. I tried every possible way to run this triplizer spider between the chainring but was unsuccessful.

https://cimg5.ibsrv.net/gimg/bikefor...bf01a588a9.jpg
The Sim 135BCD/74BCD triplizer chainring
https://cimg7.ibsrv.net/gimg/bikefor...d9835f157d.jpg
The spider cutout of the Sim triplizer
https://cimg9.ibsrv.net/gimg/bikefor...fc92b05ba5.jpg
135BD Crankset running 48T/32T using the Sim triplizer spider sans chainring bolts
https://cimg5.ibsrv.net/gimg/bikefor...f14d5f58b7.jpg
The triplizer spider setup in action. I prefer the aesthetics of my most recent adapter.

Ah-Ha!
https://cimg1.ibsrv.net/gimg/bikefor...79852c0b68.jpg
All marbles accounted for...