# Anti-chain drop thingee



## Forrest Root (Dec 22, 2006)

So, has anyone found an anti-chain drop device that would fit a 595? Given the tolerances of Campu UT cranks, a device that sits between the rt. BB cup and the frame won't work. It doesn't seem, either, as if any of the seat tube clamp devices will work either. Is anyone selling one that attaches via the braze on? I've looked and can't find anything.

Chas, what's the Look position here? I don't particularly like the idea of a chain being dropped on the BB shell. Do you or Look have any pics of what, maybe Crédit Agricole or other teams have fashioned?

It sure seems that these things are something that manufacturers of CF frames, at least the ones that make seat tubes of the non-round flavored, would want to make or consider making.


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## C-40 (Feb 4, 2004)

*info...*

Here's a link to a discussion on the topic. On page 2 is a picture of a home made chain watcher that fastens under the FD clamp bolt.

http://weightweenies.starbike.com/forum/viewtopic.php?t=15463&postdays=0&postorder=asc&start=15

A 585 has the same problem (and so do many other brands) if a triple crank or 50/34 compact is used. A standard chainwatcher hits the BB lug before it can get low enough.

Edit: After posting, I took one of my old chain watchers and found that I could grind down the width of the clamping band on the back side and get it low enough for a 34T ring on my 585.


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## nealrab (Aug 6, 2002)

*Possibility here guys...*

C40/Forrest -- you guys will know waaay more than me on this, but I had this same dilemma on my '05 585 which I had built up with Ultegra triple (DO NOT FLAME ME Forrest, I will track you down and throw thumbtacks in front of your ride). Now, maybe the bottom bracket is different now, but it was a problem for me to figure it out with my frame...I ultimately contacted Nick (a supremely knowledgeable and patient guy, not unlike you 2 gentlemen, but I only include Forrest on a GOOD day) who fabricates the N-Gear JumpStop. It is by far the best unit out there, nothing else comes close IMHO. He worked with me over a few trials and finally came up with a good-fitting clamp for the 585 bottom bracket. I can reexamine the specifics if you're interested Forrest, but as I remember it did require a deepened socket and a clamp length that was clearly different from any "stock" version. Nick also can provide varying degrees of curvature to the clamp thus allowing for a easier fit around the top of the bottom bracket area. I also had to devise a cushioning Neoprene skirt piece to act as a shim along a given section of the bracket. It actually fits around the TOP of the bottom bracket and permits efficient mounting and positioning of the clamp and metal guide. Since the metal guide can be slid along the horizontal axis to arrive at a precise distance from the chainline when in the lowest cog (25 in my case) and the 30 chainring, there is some margin for adjustability also. I'm not sure if your situation is very much different from mine, but I might be able to dig up the exact measurements for my clamp. I do remember it took a few incarnations to get it exactly correct. It's done a fab job for me, and cosmetically looks quite nice (taking into account the fact that it is simply a chain guard). Nick will work on it as many times as it takes to get it right, with no hassle or agenda. He worked with me on fitting a problematic Giant OCR Zero and a C'dale Synapse as well. Can't say enough good things about him. Best on-line/phone contact bike guy I ever dealt with. NR


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## scslite (Nov 11, 2006)

Great info! I posted a similar question for my 555 at one point but now would be highly interested to get this for my 585 using compact cranks. I'll definitely contact him to see what can be done.


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## nealrab (Aug 6, 2002)

*let me know if you need more info...*

scs, I can probably dig up the length of the fabricated clamp if you need it (or at least a more specific description to help Nick remember) for your cuurent situation. Let him know you spoke to Neal (from Montana)...he may remember what we did. At any rate let me know if you need more specific info on my assembly. I can provide specifics if desired. NR


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## Forrest Root (Dec 22, 2006)

nealrab said:


> C40/Forrest -- you guys will know waaay more than me on this, but I had this same dilemma on my '05 585 which I had built up with Ultegra triple (DO NOT FLAME ME Forrest, I will track you down and throw thumbtacks in front of your ride). Now, maybe the bottom bracket is different now, but it was a problem for me to figure it out with my frame...I ultimately contacted Nick (a supremely knowledgeable and patient guy, not unlike you 2 gentlemen, but I only include Forrest on a GOOD day) who fabricates the N-Gear JumpStop. It is by far the best unit out there, nothing else comes close IMHO. He worked with me over a few trials and finally came up with a good-fitting clamp for the 585 bottom bracket. I can reexamine the specifics if you're interested Forrest, but as I remember it did require a deepened socket and a clamp length that was clearly different from any "stock" version. Nick also can provide varying degrees of curvature to the clamp thus allowing for a easier fit around the top of the bottom bracket area. I also had to devise a cushioning Neoprene skirt piece to act as a shim along a given section of the bracket. It actually fits around the TOP of the bottom bracket and permits efficient mounting and positioning of the clamp and metal guide. Since the metal guide can be slid along the horizontal axis to arrive at a precise distance from the chainline when in the lowest cog (25 in my case) and the 30 chainring, there is some margin for adjustability also. I'm not sure if your situation is very much different from mine, but I might be able to dig up the exact measurements for my clamp. I do remember it took a few incarnations to get it exactly correct. It's done a fab job for me, and cosmetically looks quite nice (taking into account the fact that it is simply a chain guard). Nick will work on it as many times as it takes to get it right, with no hassle or agenda. He worked with me on fitting a problematic Giant OCR Zero and a C'dale Synapse as well. Can't say enough good things about him. Best on-line/phone contact bike guy I ever dealt with. NR


Well ignoring your curious comments about me (why would I flame you about Ultegra triples? Where have I flamed anyone for the kit they've chosen?), does your N-Gear anti drop device fasten to the BB shell? Do you have a picture or two? I can't mount a device between the cups and the BB shell as that will make the distance between cups too large. The ideal situation would be a custom shaped clamp to fit the seat tube. Chas, if needed would it be possible to get the cross sectional dimensions and radii for a custom fabrication? I don't know if mounting a custom device to the braze on is a good idea or not, as I'm not sure what sort of load the braze on can take.

Chas?


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## nealrab (Aug 6, 2002)

*No offense intended, FR*

I was thinking more about your feelings toward Shimano in general...like shifters for example (we won't mention the "tumor"-looking thingies) ...and your leanings toward that other manufacturer. Just a mild ribbing, nothing more intended. Your responses are always most entertaining to me as I scan through the forums. As to the chain guard issue at hand...my clamp is mounted around the very top of the lugged bottom bracket. As I remember, when I tried to wrap the clamp around the seat tube above the lug of the BB it raised the metal guide above the desired axis for the chainline. I also had to use a neoprene shim about 2 inches long and matching the width of the clamp to wrap around the front of the BB to "even out" the clamping surface around the whole circumference of the BB. The width of the Zytel clamp is 15mm and does wrap around the top of the BB shell, but this may present a problem for your set-up based on the BB cup situation you describe. Since I'm not reaIly sharp on the BB assembly you've got, I don't want to lead you astray, but I think Nick could probably help you out more than I, since he is also working on some prototypes that he showed me a year ago or so. As I stated earlier, he's absolutely great to work with, technically very knowlegeable and inclined to work through problems carefully and completely. At least he did with me...and my Giant OCR problem was tough, as was the 585 with the lugged BB. For general overview, www.gvtc.com but really I think you'd be better served to contact Nick directly via e-mail at [email protected]... He is definitely the MAN when it comes to chain guards! Sorry I can't post photos, as I'm stuck in the paleolithic age here without a digital camera...all my $ goes to bike crap. Let me know if I can provide any more helpful info...I wish I knew more and could visualize your BB cup problem, then I could compare it to my specific set-up and tell whether it would work or not. My apologies there.


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## MIN in PDX (Nov 29, 2007)

I use N-Gear (via universalcycles.com) and I don't see why it wouldn't fit your bike. They offer them in multiple seat tube sizes.


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## Forrest Root (Dec 22, 2006)

nealrab said:


> I was thinking more about your feelings toward Shimano in general...like shifters for example (we won't mention the "tumor"-looking thingies) ...and your leanings toward that other manufacturer. Just a mild ribbing, nothing more intended. Your responses are always most entertaining to me as I scan through the forums. As to the chain guard issue at hand...my clamp is mounted around the very top of the lugged bottom bracket. As I remember, when I tried to wrap the clamp around the seat tube above the lug of the BB it raised the metal guide above the desired axis for the chainline. I also had to use a neoprene shim about 2 inches long and matching the width of the clamp to wrap around the front of the BB to "even out" the clamping surface around the whole circumference of the BB. The width of the Zytel clamp is 15mm and does wrap around the top of the BB shell, but this may present a problem for your set-up based on the BB cup situation you describe. Since I'm not reaIly sharp on the BB assembly you've got, I don't want to lead you astray, but I think Nick could probably help you out more than I, since he is also working on some prototypes that he showed me a year ago or so. As I stated earlier, he's absolutely great to work with, technically very knowlegeable and inclined to work through problems carefully and completely. At least he did with me...and my Giant OCR problem was tough, as was the 585 with the lugged BB. For general overview, www.gvtc.com but really I think you'd be better served to contact Nick directly via e-mail at [email protected]... He is definitely the MAN when it comes to chain guards! Sorry I can't post photos, as I'm stuck in the paleolithic age here without a digital camera...all my $ goes to bike crap. Let me know if I can provide any more helpful info...I wish I knew more and could visualize your BB cup problem, then I could compare it to my specific set-up and tell whether it would work or not. My apologies there.


No apologies needed.

I emailed Nick, and this is what he said:

_I've looked at mounting from the braze-on (glue-on, whatever), and I know
other companies have as well (there was at least one failed attempt along
those lines about seven years ago). My conclusion was that it has more
serious technical problems than tube mounting, and it did not appear to be
commercially feasible for my situation. I presume other companies have
reached similar conclusions.

The biggest disadvantage of the braze-on mount is structural. It is much
better to conduct the chain impact load to the frame through a short-beam
compression element than through a long-arm cantilever element. There are
other technical problems, but that one alone is serious enough to make it
worth exhausting all tube-mount options first.

Unfortunately, I don't have a tube profile for the 595, and I can't tell
what shape it is from the photographs I can find. Basically, the
tube-mount options boil down to clamp-on, stick-on, or both.

If the tube can be made round (like with a shim) the clamp on approach
using the standard Zytel clamp is the easiest and cleanest option. If you
would like to try this, I will need some more information about the tube
shape.

If the standard clamp cannot be adapted, I have an experimental bendable
mounting bracket (image attached) which can conform to a variety of shapes,
and it would probably need to be mounted to the frame using a combination
of VHB adhesive and plastic ties. (VHB alone might work, but the ties
would give added security. In some cases, the bracket can be held on by a
steel band clamp without adhesive, but I don't recommend that for carbon
tubes.) I've been looking for some externally-ratcheted, tangent-pass ties
so the tail doesn't stick out from the tube at right angles, but haven't
located any yet. Standard ties should work, but for removal, they would
need to be cut where they cross the metal tabs to avoid scratching the frame.

I'm not sure how much work would be involved with either option, but I
expect the total cost would be no more than $15.

And I would suggest either of those options before the braze-on mount
approach, but if you do decide to go that route, it would probably be best
to take your bike to a local machine shop and have them fabricate a guide
for your bike's exact dimensions. It would be much simpler than having to
include means for vertical and lateral adjustments.

Let me know if you have questions, and we'll go from there._

Given my pickyness and affinity for all things black (I just love a good black hole, but doesn't everyone? I think the one at the center of our galaxy is awesome. Jeez, what were _you_ guys thinking I meant?), I wish the metal on the N-stop was black. Nick's concerns re: mounting to the braze on are the same that I had. I think that's a potential way to pop one of the rivets holding the braze on to the ST, thus setting up the potential for cracks to start forming at that rivet hole.

I guess what I need is for Sir Chas to say what the ST dimensions are at or just below the braze on for an XL 595.

Sir Chas? Sir Chas? Bueller? Bueller? Yes, Simone.....?


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## nealrab (Aug 6, 2002)

*FR, I think it'll work...*

without too much complex fabrication by Nick. He can look at the BB and see exactly what your constraints are, tho' I can't imagine how they'd be very much different from the 585 lugged BB from '05. Unless, of course, the dimensions are all changed...my frame is a Large. I'll try and find a newer 595 photo, but then I won't see the Campy drivetrain and BB you have mounted either. I think it can be done rather simply, with the Zytel clamp and a few modifications. If you can mention to Nick that we did base the length of my clamp on a 1 and 7/16 inch diameter (if I remember correctly) which he described as MOST CURLED, MOST ELONGATED with a DEEPENED SOCKET it would be a "starting point" for a trial application to your BB. He can also fabricate all kinds of variations based on your desires and, of course, cosmetic appeal. That's the beauty in dealing with Nick. He's so accommodating that it's an absolute pleasure working with him. We tried 3 or 4 clamps before I came up with a winner for all my steeds, which all had differing degrees of difficulty and complications.
You could probably paint the metal guide BLACK, tho it would scratch off with any chain drop episode, but it should be repaintable (reachable) without disassembly. Like I said it was doable for my 585 and actually looks great (the part you can actually see anyway--which isn't much). It took me a while to set it up, add the neoprene shim to the front of the BB and all, but it's a tight little assembly. Hardly noticeable, eminently functional, and that's the bottom line isn't it? I would steer clear of the braze-on assembly or anything like that...it should be doable without risking any componentry.
Let me know if you need any other info...good luck and godspeed little grasshopper. NR


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## Forrest Root (Dec 22, 2006)

nealrab said:


> without too much complex fabrication by Nick. He can look at the BB and see exactly what your constraints are, tho' I can't imagine how they'd be very much different from the 585 lugged BB from '05. Unless, of course, the dimensions are all changed...my frame is a Large. I'll try and find a newer 595 photo, but then I won't see the Campy drivetrain and BB you have mounted either. I think it can be done rather simply, with the Zytel clamp and a few modifications. If you can mention to Nick that we did base the length of my clamp on a 1 and 7/16 inch diameter (if I remember correctly) which he described as MOST CURLED, MOST ELONGATED with a DEEPENED SOCKET it would be a "starting point" for a trial application to your BB. He can also fabricate all kinds of variations based on your desires and, of course, cosmetic appeal. That's the beauty in dealing with Nick. He's so accommodating that it's an absolute pleasure working with him. We tried 3 or 4 clamps before I came up with a winner for all my steeds, which all had differing degrees of difficulty and complications.
> You could probably paint the metal guide BLACK, tho it would scratch off with any chain drop episode, but it should be repaintable (reachable) without disassembly. Like I said it was doable for my 585 and actually looks great (the part you can actually see anyway--which isn't much). It took me a while to set it up, add the neoprene shim to the front of the BB and all, but it's a tight little assembly. Hardly noticeable, eminently functional, and that's the bottom line isn't it? I would steer clear of the braze-on assembly or anything like that...it should be doable without risking any componentry.
> Let me know if you need any other info...good luck and godspeed little grasshopper. NR


I just looked at high res photos of the 585 and 595, and the tube shapes at the BB are completely different. The 585 SP and DT are round down there. That's why a clamp on FD can be used. On the 595 the tubes are (ok, seeing how can't come up with a good discription I'm going to use a word that the Cervelo marketing heads came up with at one of their bong parties. I apologize in advance.) "squoval" at the BB, and the ST actually has cut out flat section from the top of the braze on to a little ways down the ST.

As for the black, I can always anodize at home or have it anodized at a place the does such things. Black ano is popular so it shouldn't cost more than a non-vital organ to get such a place to chuck a small piece of aluminum into the soup.

Do you have a piccie of your Jump Stop in place?


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## nealrab (Aug 6, 2002)

*Now that's an interesting twist...*

I must say. Now, one might be able to "ovalize" or "circularize" the ST/lugged BB area (top section) with that neoprene shim "filler" to present the clamp onto the appropriate surface area. But I'm nonplussed about the "squoval" shape cf. the older 585 ST/BB shape. Mine is completely circular (or nearly so), so the clamp fits nicely (with a bit of that shim piece for "filling in" the gap created by the lug of the BB. I have a clamp-on FD also, not a braze-on. I don't really think that's a huge problem tho'. I think, if it were me, I would try my best to create the proper "shaping" of the BB top (just below the junction with the ST) to create as close to a circular or even oval shaped surface as is possible with the neoprene material. I think it could be done and remain "hidden" and out-of-sight because the Zytel clamp would completely cover the neoprene strip(s) which would be cut to match the 15mm width (or slightly less) of the clamp. That's essentially what I had to do -- to smoothe out the uneveness created by the lugged BB. With the 595 it may be more exaggerated or pronounced, but I think it may be able to be done without creating an eyesore. Where did you go to see a true view of the 595 BB/ST (besides your bike)? On Look site somewhere I expect? 
I'd expect that Nick could even fabricate a clamp that was more "ovalized" than "circular" to also help with the squoval circumference. That is a tricky problem, I must admit. If you follow-up with him, I'd guess he could come up with an aesthetically acceptable fabrication that does what the JumpStop is supposed to do. I can't think of any better solution, except maybe that photo that C40 linked you to -- with the Wilier bike. That looked pretty decent too, but more noticeable to me than the JumpStop would be. Sorry again Forrest, no pics of mine...but all that is evident on the BB area is a black band against a black carbon frame across the very top edge of the BB just below the ST junction. You can't even really see the steel guide as it "hides" nicely behind the 30 chainring and is virtually not noticeable (kinda like a black hole in space). Keep me posted, I'm curious now as to what happens next... NR


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## nealrab (Aug 6, 2002)

FR, Follow-up to previous post...I just went to the Look site and got a good look at the 595 BB area. I see the shaping of both the ST and BB...I believe it DEFINITELY can be done with the JumpStop Zytel clamp. Yes, the 585 BB/ST shape is more circular, but even with that, I still had to shim out the BB area before setting the clamp in place. The neoprene shim material (Nick actually was nice enough to ship me a piece) worked great for filling in gaps, depressions, uneven surfaces and the lugs themselves. I would set the neoprene strip(s) --having cut them down to 10-12mm in width --in place (maybe holding it together with tiny strips of electrical tape-black of course) and then setting the clamp over it before tightening/adjusting everything. I think if it is set up at the very TOP of the bottom bracket and BELOW the seat tube entry point, it should clamp down nicely and allow for adjustments to the metal guide. Now, I must admit I was very patient in doing this, since I am a nut case about aesthetics, and wanted it all to look clean and streamlined (and, of course, barely noticeable to an untrained eye--a trained eye will still notice it right away regardless of the assembly). I may have spent a couple of hours getting it all exactly right, but it looks pretty tight now. Maybe direct Nick to the Look site, ask him to check the correct 595 version and ZOOM on the BB area, he can scout out the "squoval"-shaped ST and BB area. He may then be able to 
adjust the curvature and length of the clamp to provide a more accurate fit. Both curvature and length are easily modified from his end. I'm saying it's a DOABLE deal, based on my assembly and what I see of the BB area on the 595.


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## chas (Aug 10, 2006)

Forrest Root said:


> Chas, what's the Look position here?


Make sure your front derailleur is adjusted properly :thumbsup: .

If that doesn't work, I like this solution (stolen from the weightweenies thread C-40 posted):

















I'm not sure if this part is available aftermarket, but it doesn't seem too difficult to make something similar at home. This seems to be a much simpler option than trying to custom fabricate a clamp in the exact dimension of the seat tube.

*[email protected]*


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