Login required to started new threads

Login required to post replies

Prev Next
My $65 attempt at the $2000 Cratus crankset/rings: fun with carbon fiber and Dremels
Quote | Reply
Total spend $65. No tape or stickers. There's a Quarq under there. Ring is removable to access the Quarq.
How did I do?

Mine at $65, with power:




Cratus at estimated $2000:



Quote Reply
Re: My $65 attempt at the $2000 Cratus crankset/rings: fun with carbon fiber and Dremels [burnthesheep] [ In reply to ]
Quote | Reply

Quote Reply
Re: My $65 attempt at the $2000 Cratus crankset/rings: fun with carbon fiber and Dremels [burnthesheep] [ In reply to ]
Quote | Reply
Wow... very cool.
Quote Reply
Re: My $65 attempt at the $2000 Cratus crankset/rings: fun with carbon fiber and Dremels [burnthesheep] [ In reply to ]
Quote | Reply
Did you buy the carbon or form it yourself? I can kind of imagine using something like a Bosu ball and slathering a layer of carbon on it.
Quote Reply
Re: My $65 attempt at the $2000 Cratus crankset/rings: fun with carbon fiber and Dremels [burnthesheep] [ In reply to ]
Quote | Reply
Amazing. I think we were separated at birth. 😂. The more of your posts I see the more I see myself in them. Always tinkering, always TT stuff.
Quote Reply
Re: My $65 attempt at the $2000 Cratus crankset/rings: fun with carbon fiber and Dremels [grumpier.mike] [ In reply to ]
Quote | Reply
grumpier.mike wrote:
Did you buy the carbon or form it yourself? I can kind of imagine using something like a Bosu ball and slathering a layer of carbon on it.

Ebay. I had to trim it. I did not form it. Barely cost more than the bag of special chainring bolts.

Secret source on the perfect carbon shape. Seek and ye shall find. Wink nod.

Most time is in using dial calipers to dremel the crankarm window. You get it cut then have to slowly open it up and test fit it 10x to get that “just right†tolerance.
Quote Reply
Re: My $65 attempt at the $2000 Cratus crankset/rings: fun with carbon fiber and Dremels [burnthesheep] [ In reply to ]
Quote | Reply
The interesting thing on the Cratus is the q-factor and not the shape.
Quote Reply
Re: My $65 attempt at the $2000 Cratus crankset/rings: fun with carbon fiber and Dremels [burnthesheep] [ In reply to ]
Quote | Reply
burnthesheep wrote:
grumpier.mike wrote:
Did you buy the carbon or form it yourself? I can kind of imagine using something like a Bosu ball and slathering a layer of carbon on it.

Ebay. I had to trim it. I did not form it. Barely cost more than the bag of special chainring bolts.

Secret source on the perfect carbon shape. Seek and ye shall find. Wink nod.

Most time is in using dial calipers to dremel the crankarm window. You get it cut then have to slowly open it up and test fit it 10x to get that “just right†tolerance.

What's with the secret squirrel, can you share where u got it from?
Quote Reply
Re: My $65 attempt at the $2000 Cratus crankset/rings: fun with carbon fiber and Dremels [burnthesheep] [ In reply to ]
Quote | Reply
Hello burnthesheep and All,

Very cool! I want one .... Oh ... I have one out in the garage I bought several years ago .... forget who it was selling them.

Looking at yours .... are they legal for Ironman races? Or is it considered a fairing? Does it make any difference if it is functionally one piece?

... (like printed?)

Would it be a more aero if it bulged out a bit to cover the crank? Would surface texture or dimples or vanes make it more aero?

What about adding an aero leading and trailing edge to the crank?

Cheers, Neal

+1 mph Faster
Quote Reply
Re: My $65 attempt at the $2000 Cratus crankset/rings: fun with carbon fiber and Dremels [BergHugi] [ In reply to ]
Quote | Reply
BergHugi wrote:
The interesting thing on the Cratus is the q-factor and not the shape.

If you want the narrow Q factor maybe use an older Dura Ace crank or Campy Pista track crank. I think they are even narrower than the wattshop crank

Then do what the OP did
Quote Reply
Re: My $65 attempt at the $2000 Cratus crankset/rings: fun with carbon fiber and Dremels [grumpier.mike] [ In reply to ]
Quote | Reply
grumpier.mike wrote:
Did you buy the carbon or form it yourself? I can kind of imagine using something like a Bosu ball and slathering a layer of carbon on it.

when I was making them, I would just lay the crank down (DS facing up) with the rings installed... place a piece of plastic as a buffer between crank and carbon... then just lay carbon down on top of it. You get the perfect shape for "your" crank and ring size.


Look good, nice bit of diy.

My Blog - http://leegoocrap.blogspot.com
Quote Reply
Re: My $65 attempt at the $2000 Cratus crankset/rings: fun with carbon fiber and Dremels [MrTri123] [ In reply to ]
Quote | Reply
nealhe wrote:
Hello burnthesheep and All,

Very cool! I want one .... Oh ... I have one out in the garage I bought several years ago .... forget who it was selling them.

Looking at yours .... are they legal for Ironman races? Or is it considered a fairing? Does it make any difference if it is functionally one piece?

... (like printed?)

Would it be a more aero if it bulged out a bit to cover the crank? Would surface texture or dimples or vanes make it more aero?

What about adding an aero leading and trailing edge to the crank?

-Maybe Glen Alden? I almost got one but it's a fairing, it's taped on temporary. A quality piece he made for sure, but if your battery goes you have to un-tape them and re-tape. Typically the "fairing test" is if you remove the part, will the bicycle still function. Remove my chainring, bike won't go. It's integral. You cannot separate them. But you can unbolt the chainring and access the Quarq without ruining or removing "tape or something".

-The Wattshop appears to have it built into the crankset instead so that it an integral function of the bike. So, not a fairing.

-The Alden ones being taped and removable, aren't an original bike function. So fairing. A plastic bolt on brake cover........is a fairing. An aero shaped stack spacer like all nice bikes have now.......not a fairing, integral. Mavic aero rim strips, bike still goes with them removed........a fairing. Not sure how the Tririg magnetic brake covers aren't fairings. Nor the P5 brake covers.

-Cranks spin, I can't imagine texture would work.

-Next up, I don't care to sand and bond carbon on my Quarq cranks and risk breaking them while riding. But if you DID do that I guess it wouldn't be a fairing. You can buy ones exactly like that already. Just has to be a "forever" part. Not tape or temporary "window sealing silicone".


I can't give up the secret sauce. It's sooooo easy if you have it.
Quote Reply
Re: My $65 attempt at the $2000 Cratus crankset/rings: fun with carbon fiber and Dremels [Morelock] [ In reply to ]
Quote | Reply
Morelock wrote:
grumpier.mike wrote:
Did you buy the carbon or form it yourself? I can kind of imagine using something like a Bosu ball and slathering a layer of carbon on it.


when I was making them, I would just lay the crank down (DS facing up) with the rings installed... place a piece of plastic as a buffer between crank and carbon... then just lay carbon down on top of it. You get the perfect shape for "your" crank and ring size.


Look good, nice bit of diy.

I like to use the spray foam insulation. Just cover the area of interest with foam, let dry, and then trim and sand to the desired shape. Once you get the shape you want, you cover with carbon fiber. Unfortunately my hobo carbon skill leave a lot to be desired and the final product looks like it was done by 6 year-old.
Quote Reply
Re: My $65 attempt at the $2000 Cratus crankset/rings: fun with carbon fiber and Dremels [grumpier.mike] [ In reply to ]
Quote | Reply
Yours and mine both haha

My Blog - http://leegoocrap.blogspot.com
Quote Reply
Re: My $65 attempt at the $2000 Cratus crankset/rings: fun with carbon fiber and Dremels [burnthesheep] [ In reply to ]
Quote | Reply
I think you did a great job. Especially for the price. I appreciate your skills and diy!

I have a 4iiii on left crank, this would be an awesome set up for me! No issues with battery replacement!
Quote Reply
Re: My $65 attempt at the $2000 Cratus crankset/rings: fun with carbon fiber and Dremels [burnthesheep] [ In reply to ]
Quote | Reply
fwiw, it's still technically a fairing.

David Millar got nailed trying to use the old "it's part of the crank" years ago :D (albeit in UCI racing... nobody is really going to care in tri or tt's for us mortals)



My Blog - http://leegoocrap.blogspot.com
Quote Reply
Re: My $65 attempt at the $2000 Cratus crankset/rings: fun with carbon fiber and Dremels [burnthesheep] [ In reply to ]
Quote | Reply
burnthesheep wrote:
grumpier.mike wrote:
Did you buy the carbon or form it yourself? I can kind of imagine using something like a Bosu ball and slathering a layer of carbon on it.


Ebay. I had to trim it. I did not form it. Barely cost more than the bag of special chainring bolts.

Secret source on the perfect carbon shape. Seek and ye shall find. Wink nod.

Most time is in using dial calipers to dremel the crankarm window. You get it cut then have to slowly open it up and test fit it 10x to get that “just right†tolerance.

Could you send a link to the ebay listing you got the cover from?
Quote Reply
Re: My $65 attempt at the $2000 Cratus crankset/rings: fun with carbon fiber and Dremels [lastlap] [ In reply to ]
Quote | Reply
lastlap wrote:
burnthesheep wrote:
grumpier.mike wrote:
Did you buy the carbon or form it yourself? I can kind of imagine using something like a Bosu ball and slathering a layer of carbon on it.


Ebay. I had to trim it. I did not form it. Barely cost more than the bag of special chainring bolts.

Secret source on the perfect carbon shape. Seek and ye shall find. Wink nod.

Most time is in using dial calipers to dremel the crankarm window. You get it cut then have to slowly open it up and test fit it 10x to get that “just right†tolerance.


What's with the secret squirrel, can you share where u got it from?

Ideally you can find one with a flat and minimal flange in a diameter that requires no trimming, just cutting out the crank slot.



ECMGN Therapy Silicon Valley:
Depression, Neurocognitive problems, Dementias (Testing and Evaluation), Trauma and PTSD, Traumatic Brain Injury (TBI)
Quote Reply
Re: My $65 attempt at the $2000 Cratus crankset/rings: fun with carbon fiber and Dremels [burnthesheep] [ In reply to ]
Quote | Reply
Very nicely done!
Quote Reply
Re: My $65 attempt at the $2000 Cratus crankset/rings: fun with carbon fiber and Dremels [lastlap] [ In reply to ]
Quote | Reply
Use Google Image search.......
Quote Reply
Re: My $65 attempt at the $2000 Cratus crankset/rings: fun with carbon fiber and Dremels [Cajer] [ In reply to ]
Quote | Reply
Cajer wrote:
Could you send a link to the ebay listing you got the cover from?


Search 'Carbon Fiber Speaker Dust Cover'

https://www.google.com/search?q=carbon+fiber+speaker+dust+cap&sxsrf=APq-WBsBgkNXTY7g9jO8urqoBrPpbVPEhQ:1649972090186&source=lnms&tbm=shop&sa=X&ved=2ahUKEwjuo8yCwZT3AhXklGoFHUAaDnYQ_AUoAXoECAEQAw&biw=1920&bih=937&dpr=1
Quote Reply
Re: My $65 attempt at the $2000 Cratus crankset/rings: fun with carbon fiber and Dremels [burnthesheep] [ In reply to ]
Quote | Reply
Love it! How did you bond the cover? 3M double sided tape or something like that?

EZ-Disc in UK sell a cover for £90. The tested it at the Silverstone wind tunnel in this video and found an average saving of:
  • 30km/h = 1.37W
  • 40km/h = 3.09W
  • 50km/h = 5.19W

I'm pretty interested now, partly because they are unique and look awesome, and I would like to make my own out of the carbon fibre speaker dust cover too!

Dayoutsports.com.au| Australia's Newest Cycling and Tri Apparel Brand
Quote Reply
Re: My $65 attempt at the $2000 Cratus crankset/rings: fun with carbon fiber and Dremels [PattoDayOut] [ In reply to ]
Quote | Reply
PattoDayOut wrote:
Love it! How did you bond the cover? 3M double sided tape or something like that?

It's same epoxy as you makeup carbon fiber. I did not want issues with it coming off. I race that ring briefly each year then swap back over the normal 2x chainring setup without any fancy stuff. I'd make another if I wore the ring out. Or carefully dremel it off the old one and sand/bond it to the new ring.
Quote Reply
Re: My $65 attempt at the $2000 Cratus crankset/rings: fun with carbon fiber and Dremels [ In reply to ]
Quote | Reply
Ok, I just got the 7 inch carbon speaker dust cover. I like a little project like this. Let's see.
Quote Reply
Re: My $65 attempt at the $2000 Cratus crankset/rings: fun with carbon fiber and Dremels [burnthesheep] [ In reply to ]
Quote | Reply
Hey BurnTheSheep

Very nice project, I'm looking forward to having something cleaner than ducttape.
3 quick questions :
- Sram arm at spindle to Chainring seems to be 19mm, the 5.9" cover has a height of 21mm so going with that one (inner height accounting for the 1mm thickness should still work), what size did you go with?
- I can't see from the pictures, did you cut a slit (3 sided) or did you cut an opening (4 sided) + slip in the crank sans pedal? An opening would be very neat but eyeballing the cut must be dicey.
- Are you using 5 rivet nuts (the type sram uses for their Hidden Bolt stuff)?

TIA
Quote Reply

Prev Next