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Thread: Deraileur Guard

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    Senior Member hotbike's Avatar
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    Deraileur Guard

    A beloved mentor of mine has always been asking me to see if I could come up with a deraileur guard, to keep objects, weeds and sticks, out of a rear deraileur.

    Last night, I had an idea. So I put this prototype of the new deraileur guard on the Type 11. Actually, it's a Trek 720 that I added coroplast panniers to, and rebranded it as the NFA Vehicles Type 11.

    The deraileur guard is not made of coroplast, it's something else.

    Here are the pictures, straight from my Canon camera:







    This has not been test ridden yet, but it clears the chain in all gears, including high, and I don't think it will hit my right heel or ankle when I pedal.
    http://www.flickr.com/photos/11629987@N02/sets/72157639939606343/

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    You're guarding against...what?

    Taped-on cardboard won't do much at any kind of speed; heck, some Wally bikes come with looped steel derailleur guards, and THEY don't work well (bend too easily).

    Good luck with it, hope it works, but I'm dubious.......

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    Senior Member sonnetg's Avatar
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    Great concept, but it wont help if you hit a pavement, like I did a while back. I wish the damn cages weren't so long.. *sigh*



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    Time for a change. stapfam's Avatar
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    Don't really have a problem with deraillers being damaged but I can see that guard damaging the bike if is strong enough to withstand hits. And if it won't stand a hit- it will still cause a problem.



    Why develop something for a use that is not needed? In 20 years of riding I have only ever damaged one derailler by it getting a hit. That puts it about 60,000miles and most of that is offroad.
    How long was I in the army? Five foot seven.


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    Senior Member hotbike's Avatar
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    Well, this is only a prototype... maybe it's only a mock-up. I'm testing it for clearance, to see if it gets in the way of anything. I could make it out of Fiberglass, or maybe it could be Steel welded to the chainstay.

    Myself, with 140,000 miles of riding over 40 years, I have destroyed two deraileurs, and spent many hours skinning my knuckles, to remove stuff that got wrapped between sprockets. And as I said in the introduction, someone (a Professor of Mechanical Engineering) asked me to work on building a deraileur guard. I should have done this twenty years ago, but I was busy building fairings.

    This piece is actually TWO layers of foam board, so it is about half an inch thick. It is weak enough that it will sacrifice itself and be destroyed before it can damage the frame of the bike, which should resolve the concerns you all have expressed. I think it will brush weeds and tall grass aside, and if I hit a piece of baling wire, hopefully it will embed itself in the foam before it reaches the deraileur.
    http://www.flickr.com/photos/11629987@N02/sets/72157639939606343/

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    You might consider having them switch over to an internal-gear-hub.

    Avoids the hanging-derailler problem entirely, and is a lot more convenient to shift anyways (shifts while standing still). Only downside is the higher cost.

  7. #7
    Life is good RonH's Avatar
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    Most Xmart bikes come with some kind of derailleur guard.

    My bikes: 2001 Litespeed Tuscany---2015 Cannondale Supersix EVO carbon

    I thought of that while riding my bicycle -- Albert Einstein

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    Senior Member hotbike's Avatar
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    Quote Originally Posted by Doug5150 View Post
    You might consider having them switch over to an internal-gear-hub.

    Avoids the hanging-derailler problem entirely, and is a lot more convenient to shift anyways (shifts while standing still). Only downside is the higher cost.
    Yes, an Internal-Gear-Hub would not have the problem deraileurs have. But what about the front deraileur?-The front deraileur relies upon the slack in the chain, and the tension idlers on the rear deraileur, does it not? So Internal-Gear-Hubs are limited to seven or eight speeds, with no front deraileur.
    http://www.flickr.com/photos/11629987@N02/sets/72157639939606343/

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    Senior Member dougmc's Avatar
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    Quote Originally Posted by Doug5150 View Post
    You might consider having them switch over to an internal-gear-hub.

    Avoids the hanging-derailler problem entirely, and is a lot more convenient to shift anyways (shifts while standing still). Only downside is the higher cost.
    Really? That's the only downside you can think of?

    Often you get fewer gears or a limited range of gears.
    If you do get a similar number of gears, the hub is likely really expensive (you did cover that.)
    Many hubs are quite heavy.
    Hubs are somewhat less efficient than a derailer setup.
    Some hubs have a thing sticking out the side that's just as fragile as a derailer.

    I do think that your advice is sound -- internal hubs are great -- but there's more downsides than you mentioned.

    (Of course, the advantages are there too -- less maintenance required, fewer exposed parts to break, some give you an infinite numbers of gears.)
    Last edited by dougmc; 02-10-11 at 12:00 PM. Reason: fixed a typo

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    Senior Member hotbike's Avatar
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    Quote Originally Posted by dougmc View Post
    ..., some give you infinite numbers of gears.)
    I wasn't aware of any hub with "[an] infinite number of gears". Please be more specific, give a link to the manufacturers site?
    http://www.flickr.com/photos/11629987@N02/sets/72157639939606343/

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    Senior Member dougmc's Avatar
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    Quote Originally Posted by hotbike View Post
    I wasn't aware of any hub with "[an] infinite number of gears". Please be more specific, give a link to the manufacturers site?
    http://www.sheldonbrown.com/harris/nuvinci.html
    http://www.fallbrooktech.com/nuvinci.asp
    http://www.bikecommuters.com/2008/02...hat-a-feeling/

    People seem to really like them, though they're quite heavy (six pounds or so, order ones were more.)

  12. #12
    coprolite fietsbob's Avatar
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    Rohloff duplicates an MTB drive train in 14 ratios. range is wider than the NuVinci.

    Im running a Sturmey AW3 + a Schlumpf mountain drive planetary
    2 speed reduction gear crank in my folding bike.
    Mr Schlumpf as 2 over drive hubs 1.6x and 2.5x

    Not stepless like the other , but has 6 useful ratios over a wide range.

    no front or rear derailleurs needed.
    Last edited by fietsbob; 02-10-11 at 12:50 PM.

  13. #13
    Senior Member hotbike's Avatar
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    Anyway, I took the bike for a half mile test ride yesterday, and the Deraileur Guard clears my ankle. It does NOT interfere with pedaling . It clears the chain in all gears on the rear cluster. However, I did not try it with the chain on the largest Chain Ring. Again , the guard is a half inch thick, so it looks like it will clear, from the outside, but I'm not sure about the inside. I have to test ride it again in the big ring. I may have to cut, grind, or file a groove into the material, if it rubs the chain.

    Those NuVinci Hubs look interesting, but they must weigh a lot with those huge ball bearings.
    http://www.flickr.com/photos/11629987@N02/sets/72157639939606343/

  14. #14
    Humvee of bikes =Worksman Nightshade's Avatar
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    Quote Originally Posted by RonH View Post
    Most Xmart bikes come with some kind of derailleur guard.

    I installed this type of guard on both my derailleur equipped bikes saving one of them from a bad fall when I crashed hitting a stone.
    My preferred bicycle brand is.......WORKSMAN CYCLES
    I dislike clipless pedals on any city bike since I feel they are unsafe.

    Originally Posted by krazygluon
    Steel: nearly a thousand years of metallurgical development
    Aluminum: barely a hundred, which one would you rather have under your butt at 30mph?

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    Senior Member zonatandem's Avatar
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    A solution for a problem . . .
    Twice a problem in 140,000 miles? Not like a daily occurence, but once every 20 years?!
    Have in over 300,000 miles cyling. Only once had a piece of wire wrap into the cog . . .

  16. #16
    Senior Member hotbike's Avatar
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    Quote Originally Posted by zonatandem View Post
    A solution for a problem . . .
    Twice a problem in 140,000 miles? Not like a daily occurence, but once every 20 years?!
    Have in over 300,000 miles cyling. Only once had a piece of wire wrap into the cog . . .
    As I said, Someone else told me I should "Invent" a better deraileur guard. I was only fulfilling a request. I built lots of fairings, and someone said I should make a deraileur gaurd, in addition to the fairings. It is kind of a fairing, if you define a fairing as a "protective shield" .
    I'm also thinking about chain-guards. Maybe a full length chain guard could be attached to the top of the deraileur guard, perhaps with two screws?
    Maybe if I take my rear wheel off, to change a tube, and the bike falls off the park-bench, the deraileur guard will protect the deraileur from the ground?
    Maybe I could be running a full-service LBS someday, and someone will walk in , lay $7.00 on the counter, and buy a deraileur guard?
    http://www.flickr.com/photos/11629987@N02/sets/72157639939606343/

  17. #17
    Senior Member cyclist2000's Avatar
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    Quote Originally Posted by hotbike View Post
    Yes, an Internal-Gear-Hub would not have the problem deraileurs have. But what about the front deraileur?-The front deraileur relies upon the slack in the chain, and the tension idlers on the rear deraileur, does it not? So Internal-Gear-Hubs are limited to seven or eight speeds, with no front deraileur.
    rohloff speedhub IGH has 14 speeds and 500% increase in gearing. No need for a front derailleur.

    I'm like the other folks. I have one damaged derailleur in 45 years of riding derailleur equipped bikes and it was caused by a bad adjustment not impact to anything. I also wouldn't be interested in such a device since I don't encounter much that will damage a derailleur as I ride a road bike, maybe mountain bikers would be interested in such a device. As for your scenario of my bike fallingover when fixing a flat, I always lay by bike down on the NDS so the deraileur hangar won't be bent. I have noticed that typically my derailleur hangar will bend before my derailleur is damaged and it is easy to bend back the hangar with the proper tool.
    Last edited by cyclist2000; 02-13-11 at 09:53 PM.
    I don't do vintage, I bought them new, rode them, kept them. Now they are just old bikes
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    Senior Member iforgotmename's Avatar
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    Come on guys

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    Senior Member sonnetg's Avatar
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    Believe it or not, but a cheapo walmart bike i bought came came with a derailleur guard. I dont know what to make of it, because i will most likely convert it to a single speed.

  20. #20
    Senior Member BlazingPedals's Avatar
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    The more I look at the homemade 'derailleur guard,' the more I realize I have no idea whatsoever what it's supposed to protect against.

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