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Old 10-22-09, 04:41 PM   #1
Charles Ramsey
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a homemade microadaptor

Here http://share.ovi.com/media/currentre...resident.10101 is a homemade adaptor shown with homemade countersinking tool that lets me usa a 58mm bolt circle on a 74mm bolt circle crank. Here http://share.ovi.com/media/currentre...resident.10100 it is shown mounted on the crank with spacer made out of an old gear. Here http://share.ovi.com/media/currentre...resident.10075 it is shown set up as a quad. It works but the 36 tooth chainring is 1mm from the chainstays. The 20 36 jump works fine but is too much ergonomically.
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Old 10-22-09, 05:15 PM   #2
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thats the craziest thing I have ever seen, you must be in a seriously hilly area if you need a quad up front.
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Old 10-22-09, 08:54 PM   #3
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Nice job on the fabrication. It's cool that you can set it up as a quad. I have an adapter on my MB-3 thats somewhat similar. I got it so long ago that I can't even remember who made it. Ringle maybe? It allows me to run a 58mmBCD 20 tooth grannie on a 74mmBCD crank. I don't think they're in production anymore.
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Old 10-23-09, 04:15 AM   #4
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I used to get a British mountain bike mag. There was a writer in it that was doing some experimentation with drivetrains.
think he got a similar disc to mount other cogs on his cranks.

A British company called Highpath engineering did that sort of thing
http://www.highpath.co.uk/index.html

I heard of an adaptor to use cassette sprockets on cranks
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Old 10-23-09, 04:40 AM   #5
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I heard of an adaptor to use cassette sprockets on cranks
http://abundantadventures.com/quads.html

Unfortunately, uses Suntour cassette sprockets. Suntour's cassette hub had a wider freehub body that stepped down to threads to screw on the last two cogs. The Shimano and Campy cassettes have smaller diameter to the freehub body and are small enough that it would interfere with the BB shell if you tried to make an adapter to fit.

I saw one of those Ringle adapters in the used parts bin at the LBS last month, shoulda snagged it
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Old 10-23-09, 05:00 AM   #6
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You can also make a quad crankset by using extra long chainring bolts and putting two chainrings in the small ring position, with spacers in between. Obviously, you are still then limited by the BCD of the inner ring. Using this technique, we have a 24-32-42-53 crankset on our tandem (BCD = 74mm / 130mm). The Shimano Ultegra triple front derailleur JUST has enough lateral movement to handle the shifting, operated by a bar end shifter. A MTB rear derailleur handles the chain wrap fine.

Things would be simpler if we left out the 32 tooth ring, but then the cadence jump from 24 to 42 would be much bigger than what is ideal, especially on a tandem. We tried using a 38 or 39 tooth middle ring to avoid this, but then we ran out of gears on the top end of that ring too easily, and in gently rolling terrain had to switch between the middle and big rings too often. We use a tightly-spaced cassette (11-26, 10-speed), so we could instead use a larger range cassette (e.g., 11-32) and a larger small chainring (e.g., 30 tooth) to achieve the same lowest gear, but then the cadence changes when shifting on the back are a bit large. With our current setup, we have as low of a gear as we've ever needed (24 / 26 gearing and 700c wheels = about a 25" gear), we have a gear range of 522%, and have gear changes on the rear never exceeding 13% and changes on the front never exceeding 33%. We're really happy with the setup now. Smoother front shifting might be nice to have (getting into the extreme chainrings is not straightforward), but the gear combinations that we have are ideal.

(BTW, I love playing around with custom gearing.)

Last edited by Chris_W; 10-23-09 at 07:35 AM.
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Old 10-23-09, 05:51 AM   #7
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I was expecting to see pictures of some Dremel'ed and hacksaw'ed piece of metal, not a nicely machined part. The quad setup is certainly intriguing for use on a tandem. I'll have to keep that in mind if I can ever persuade my wife to ride one with me.
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Old 10-23-09, 06:11 AM   #8
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One bolt circle triple cranks used to be relatively common. A 110 BCD crank with long chainring bolts and spacers was usually geared 34/42/52 and I had an old Suguino crank that came that way.

I suppose you could make a quad by starting with a 110/74 bcd crank and using a 24T granny and the above three larger rings on the 110 bolt circle as a variation of what Chris W has done.
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Old 10-23-09, 08:17 AM   #9
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This is simply an expiriment it would be possible to put 4 gears up front in the same spacing 3 occupy now. A reasonable setup would be a 58mm bolt circle for the smallest gear a 94mm bolt circle for the next smallest this will take a 30 tooth gear and be very stiff and either a 110mm or a 130mm for the 2 largest cogs. A half step makes the most sense for the 2 largest cogs say a 20 30 39 42
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Old 10-23-09, 08:31 AM   #10
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Originally Posted by zzyzx_xyzzy View Post
http://abundantadventures.com/quads.html

Unfortunately, uses Suntour cassette sprockets. Suntour's cassette hub had a wider freehub body that stepped down to threads to screw on the last two cogs. The Shimano and Campy cassettes have smaller diameter to the freehub body and are small enough that it would interfere with the BB shell if you tried to make an adapter to fit.

I saw one of those Ringle adapters in the used parts bin at the LBS last month, shoulda snagged it
From the looks of the pictures, those are actually Suntour Freewheel cogs. Lots of older shops will probably have a giant box of these somewhere, unlike the near-impossible to find cassette cogs. Cool find!
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Old 10-23-09, 01:21 PM   #11
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Those quad adapters are still being made by a company called mountain tamer or something like that.
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Old 10-23-09, 03:16 PM   #12
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Charles, watch out for getting the rings spaced too close or you'll get cross chain rubbing when the chain angles to the outside in a lot of combos. A few thou less than standard won't be an issue but if you get too greedy then it'll act up. Use all the travel the derrailleur and friction shifter provides and space the jumps equally within that amount.

A very interesting mod. Not something I can see being needed for a single but on a tandem it would be aces.
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Old 10-23-09, 03:36 PM   #13
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Abt. 20 years ago I made a similar adaptor for our recumbent tandem. We were much younger then so the rings were 20-32-44-56. Now we're geezers and run 20-28-36-46. All but the 20t are BioPace. While Bios are of questionable value on a non-bent, on a 'bent BioPace or Q-rings are sweetness personified. So smooth.

BTW It took a little tweaking of the derailleurs to handle 20-32-44-56 and to wrap up all that chain.


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Old 10-23-09, 04:29 PM   #14
Charles Ramsey
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you be very careful with that setup tandem racers have been known to shear the bolts on campagnolo record cranks. The longer the bolts are and the smaller the bolt circle is the easier it will be to do that.
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You can also make a quad crankset by using extra long chainring bolts and putting two chainrings in the small ring position, with spacers in between. Obviously, you are still then limited by the BCD of the inner ring. Using this technique, we have a 24-32-42-53 crankset on our tandem (BCD = 74mm / 130mm). The Shimano Ultegra triple front derailleur JUST has enough lateral movement to handle the shifting, operated by a bar end shifter. A MTB rear derailleur handles the chain wrap fine.

Things would be simpler if we left out the 32 tooth ring, but then the cadence jump from 24 to 42 would be much bigger than what is ideal, especially on a tandem. We tried using a 38 or 39 tooth middle ring to avoid this, but then we ran out of gears on the top end of that ring too easily, and in gently rolling terrain had to switch between the middle and big rings too often. We use a tightly-spaced cassette (11-26, 10-speed), so we could instead use a larger range cassette (e.g., 11-32) and a larger small chainring (e.g., 30 tooth) to achieve the same lowest gear, but then the cadence changes when shifting on the back are a bit large. With our current setup, we have as low of a gear as we've ever needed (24 / 26 gearing and 700c wheels = about a 25" gear), we have a gear range of 522%, and have gear changes on the rear never exceeding 13% and changes on the front never exceeding 33%. We're really happy with the setup now. Smoother front shifting might be nice to have (getting into the extreme chainrings is not straightforward), but the gear combinations that we have are ideal.

(BTW, I love playing around with custom gearing.)
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Old 10-23-09, 04:37 PM   #15
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Abt. 20 years ago I made a similar adaptor for our recumbent tandem. We were much younger then so the rings were 20-32-44-56. Now we're geezers and run 20-28-36-46. All but the 20t are BioPace. While Bios are of questionable value on a non-bent, on a 'bent BioPace or Q-rings are sweetness personified. So smooth.

BTW It took a little tweaking of the derailleurs to handle 20-32-44-56 and to wrap up all that chain.

The Romp family http://web.archive.org/web/200304150...com/page5.html used a 20 34 44 54 on their quad. It had standard XTR derailers and used a QPB travel agent to shift them. I had a crank with 46 outer and 38 biopace and 24 rings. My body automatically adjusted between the rings.
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Old 10-24-09, 12:36 AM   #16
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you be very careful with that setup tandem racers have been known to shear the bolts on campagnolo record cranks. The longer the bolts are and the smaller the bolt circle is the easier it will be to do that.
Thanks for the warning, I'll keep an eye on it. We can get up a lot of climbs in our 32-tooth, so the 24 tooth doesn't get used a much as a regular granny would. However, when we are using it then their can be a significant amount of force going through the tandem drivetrain, so it could be a concern.
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Old 10-24-09, 06:46 AM   #17
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When I was working at a bike shop I would take off broken parts from bikes and keep them, in case they were needed on other bikes. For instance if a screw went pinging away from a bike that was getting built for display. Could get a replacement from the box of bits. But the boss was keen to clear out all the stuff that wasnt new parts. Fair enough.
I have loads of bits in my garage. a box full of old freewheels. Used to run Suntour Winner freewheels on 3 of my bikes. They were ok. I suppose they would fit that adaptor.
I got a set of Stronglight 49d crank arms with rings from ebay last year. I then got another pair of rings for them. So now Ive got a 34t and 42t inner rings and 48t and 58t outer rings. I had a plan to make a triple chainset with the 34,48,58 rings, for my Raleigh 20. But havent got round to it. The cranks have a very small bolt circle. So geuss they wouldnt be good for a strong rider.
Will put them back on ebay sometime. The cranks and rings cost me about 10. Seen those cranks go for 5 times that easily.
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Old 10-24-09, 09:06 AM   #18
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those "homemade" adaptors look real nice. after I buy the Aluminum stock and the countersink bit and the drillpress how much did I invest to run a 20 instead of a 28?

also are these truly homemade or made at work when no one was looking?
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Old 10-24-09, 01:16 PM   #19
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those "homemade" adaptors look real nice. after I buy the Aluminum stock and the countersink bit and the drillpress how much did I invest to run a 20 instead of a 28?

also are these truly homemade or made at work when no one was looking?
I pulled the aluminium stock out of a recycle bin it is 5.5 mm thick you need a thinner one consider using 2mm thick steel. The one I'm working on now uses alumimum discs from a computer hard drive. http://share.ovi.com/media/currentre...resident.10122 these come in thicknesses of 1mm to 2mm and are much easier to work with they will let me play the spacing then they will be epoxied or red locktited together. The countersink tool was made out of a chainring bolt cut with a round chainsaw file. A 20 tooth stainless steel chainring cost $20 but they will last forever. All of this was done by hand and took hundreds of hours. The spacer was made out of a gear made of 7075 T6 aluminum and was very hard to file. Oh and lets not forget this http://share.ovi.com/media/currentre...resident.10073

Last edited by Charles Ramsey; 10-24-09 at 02:16 PM.
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