Finally made my first chainring

[icantdrive65]

I have been riding my Raleigh XXIX for 5 years and have wanting to make a chainring for it. I have all of the tools, but it has been hard to get around to it while keeping up with the regular jobs. I finally got one done this week. Took it for a spin this morning.

It's a 33T to replace the one Truvativ ring that came on the bike originally.

[phsycle]

Details, man, details. I'm all for custom ring makers. Looks heavy, though.

[NEPMTBA]

Always a +1 for cobblers...
...who make their own stuff!

[CB2]

Looks great!

Word of advise: only make them for personal use / close friends.

[Mr.Magura]

I have been riding my Raleigh XXIX for 5 years and have wanting to make a chainring for it. I have all of the tools, but it has been hard to get around to it while keeping up with the regular jobs. I finally got one done this week. Took it for a spin this morning.

It's a 33T to replace the one Truvativ ring that came on the bike originally.

That's looking good right there

Did you CNC or use a rotary table?


Magura

[zaskaranddriver]

How'd the first ride go?

[icantdrive65]

I don't have a gram scale. I put it on my postal scale and it weighs somewhere between 40-50 grams. I didn't put much effort into making it light. Just wanted to try out the tooth profile. It worked fine on a quick 6-mile ride this morning.

This one is machined out of 1/8" thick (3mm) 6061 material that I had on the shelf. I did it in two setups on my Fadal CNC mill. I ran the mounting holes, teeth and center bore in one operation and flipped it over to cut the step and ramp on the teeth on the other side. So it is very concentric: no runout. The teeth are machined to 2mm thickness. I will probably redo it with thicker teeth for the wider chain on my SS.

What I learned so far: I need more clearance to mount the ring easily without removing the crank arm. I was barely able to get it over the spider. So cutouts are necessary.

[phsycle]

If you decide to sell, please let me know. I like collecting various chainrings...

[Mr.Magura]

I don't have a gram scale. I put it on my postal scale and it weighs somewhere between 40-50 grams. I didn't put much effort into making it light. Just wanted to try out the tooth profile. It worked fine on a quick 6-mile ride this morning.

This one is machined out of 1/8" thick (3mm) 6061 material that I had on the shelf. I did it in two setups on my Fadal CNC mill. I ran the mounting holes, teeth and center bore in one operation and flipped it over to cut the step and ramp on the teeth on the other side. So it is very concentric: no runout. The teeth are machined to 2mm thickness. I will probably redo it with thicker teeth for the wider chain on my SS.

What I learned so far: I need more clearance to mount the ring easily without removing the crank arm. I was barely able to get it over the spider. So cutouts are necessary.

How did you design it?


Magura

[ALBM]

Good for you, nice job! Are you going to have that hard anodized for wear purposes?

[icantdrive65]

If you decide to sell, please let me know. I like collecting various chainrings...

I intend to get there before too long. I will not sell anything that I don't already have made. I know how that turns out. I need to get some 7075 material for strength and longevity.

How did you design it?


Magura

Math and CAD. I used my old standby BobCAD V17. The software is 15 years old, but it's quick and efficient. For more complex stuff like fork crowns and 3D hot rod parts, I use a newer version of BobCAD.

[icantdrive65]

Good for you, nice job! Are you going to have that hard anodized for wear purposes?

I will check into coatings that will hold up once I get some 7075. This piece is just a test mule to check geometry and function. I really want to see how long 6061 will last, just for fun.

[Mr.Magura]

Math and CAD. I used my old standby BobCAD V17. The software is 15 years old, but it's quick and efficient. For more complex stuff like fork crowns and 3D hot rod parts, I use a newer version of BobCAD.

So, the hard way just like me


Magura

[icantdrive65]

So, the hard way just like me


Magura

Yeah, but I cheated in the execution. I have CNC mills. Your rotary table chainring is impressive.

I honestly was a little lost at first, but I found some very helpful info on drawing sprockets that got me rolling.

[Mr.Magura]

Yeah, but I cheated in the execution. I have CNC mills. Your rotary table chainring is impressive.

I honestly was a little lost at first, but I found some very helpful info on drawing sprockets that got me rolling.

It's rotary table + file

I'll ask my drawing guy if there is a shortcut, and post it if he has something up the sleeve.
I couldn't make a CAD drawing if my life depended on it. He is on the other hand quite good.
When I made mine, I just had the numbers on a Post-It. Not the way it's going to be in the future. Made like 3 or 4 that way.


Magura

[ask]

Nice job... Looks great.

I've been talking to a friend that makes parts to see about getting some custom chainrings made. Let us know when you get around to selling these... I'd be up for buying one for my SS.

[fishcreek]

Looks great!

Word of advise: only make them for personal use / close friends.

I agree, but just in case you decide to go full production, put me on #1.

[icantdrive65]

While the machine was set up, I ran a revised version of the bash guard I have had on my Blur.

[wyatt79m]

That looks really nice

[phsycle]

While the machine was set up, I ran a revised version of the bash guard I have had on my Blur.
]

Wow, I'd like one of those. Current bash guard is a porker.

[icantdrive65]

This one is ridiculously light. It looks like it barely tips the scale over to .03 kg, so I'm guessing low 30s until I weigh it on an accurate scale.

[Mr.Magura]

You really got the itch

I did a similar design years ago. It turned out to be too weak, and collapsed under heavy load.

I did a revised version later where I did the cutouts pretty much the same, but with an end mill with a radius from both sides, and left a thin wall in the center. That one worked well.

Later I started using a mix of aluminum and composites, as that seems to offer a better weight to strength ratio.

Soon I'll have to make some more, as I'm about to be out of rings. I guess I'll look in the direction of the Hope design, but with carbon in the mix.

Magura

[icantdrive65]

You really got the itch

I did a similar design years ago. It turned out to be too weak, and collapsed under heavy load.

I did a revised version later where I did the cutouts pretty much the same, but with an end mill with a radius from both sides, and left a thin wall in the center. That one worked well.

Were the cutouts triangular like mine? How long did it take for the chainring to fail?

I made the lightweight one a 32T and put it on my Blur. I am itching to get out and ride it, but the rain is hitting us pretty hard here.

[fishcreek]

Shame to hide that chainring..

[icantdrive65]

Shame to hide that chainring..

Yeah. I should get some new bolts so I can run it without the bash guard.