Could I get some ideas?

[Iron Yeti]

I need to get rid of my dérailleur hanger mounted chain tensioner so I can mount the Nuvinci hub's torque arms. I am going to go with a chainstay mounted chain tensioner, problem is my chain stay is rectangular shaped! Can anyone help me out with ideas whether it be a custom bracket to mount a spring loaded chain tensioner to or chain tensioner with a rectangle shaped bracket?

 

[Zoot Katz]

How about a tab welded to the chainstay?

If the stay is steel you could hack it off any deraileur hanger and weld it on.

Check to see that it would be in position to be effective.
Sometimes you can change the spring in a chain tensioner so it either pulls up or pushes down.

 

[etard]

Since your chainstay is rectangular, maybe you could use a tap and die set to screw your mounting screws directly onto the chainstay. I dont know whether or not this would weaken the chainstay or not, but it would seem the screws fills in the metal, so maybe not. Also, why do you need a chain tensioner with a nuvinci in the first place? If you do need a tensioner, I would look into the motorized (ICE) bike parts vendors for possible solutions. I might try to mount a roller wheel on a flat piece of metal bent downward from the chainstay in the same fashion a leaf spring works, with the tension of a flat piece of metal not wanting to bend. Does this sound feasable?

 

[Rassy]

I Y, since your chainstays are recangular, just use two short pieces of steel or aluminum and drill two holes in each piece, that just clear the height of the chainstay, so you can bolt them right to the chainstay, and you have your bracket. you can either mount your tensioner using one of the bolts that holds the bracket on, or have one of the pieces longer so you can position the tensioner wherever you want it.

 

[Iron Yeti]

How about a tab welded to the chainstay?

If the stay is steel you could hack it off any deraileur hanger and weld it on.

Check to see that it would be in position to be effective.
Sometimes you can change the spring in a chain tensioner so it either pulls up or pushes down.

My chainstay is aluminum. I never thought of a tab welded on it. I don't even know of any body/metal works shops in my area that would do that or how much it'd cost though. A nicely welded aluminum tab would be fairly strong, right?

Since your chainstay is rectangular, maybe you could use a tap and die set to screw your mounting screws directly onto the chainstay. I dont know whether or not this would weaken the chainstay or not, but it would seem the screws fills in the metal, so maybe not. Also, why do you need a chain tensioner with a nuvinci in the first place? If you do need a tensioner, I would look into the motorized (ICE) bike parts vendors for possible solutions. I might try to mount a roller wheel on a flat piece of metal bent downward from the chainstay in the same fashion a leaf spring works, with the tension of a flat piece of metal not wanting to bend. Does this sound feasable?

Hm, I am not too keen with any possibility of compromising the structural integrity of my chainstay. I need a chain tensioner because I have vertical dropouts, it's a mountain bike. The fella at the bike shop said he could probably get my chain to fit snug without a tensioner, lies.

That last option sounds pretty good. Another piece of information worth noting is that while the chainstay is rectangle, the front and rear are not flat, they are slightly bowed. My fear is the clamp might slip during use...

I Y, since your chainstays are recangular, just use two short pieces of steel or aluminum and drill two holes in each piece, that just clear the height of the chainstay, so you can bolt them right to the chainstay, and you have your bracket. you can either mount your tensioner using one of the bolts that holds the bracket on, or have one of the pieces longer so you can position the tensioner wherever you want it.

This sounds like a fairly feasible option. However, again my chainstay is slightly rounded on the front and back sides leading me to fear slippage.

 

[Zoot Katz]

How about a tab welded to the chainstay?

If the stay is steel you could hack it off any deraileur hanger and weld it on.

Check to see that it would be in position to be effective.
Sometimes you can change the spring in a chain tensioner so it either pulls up or pushes down.

My chainstay is aluminum. I never thought of a tab welded on it. I don't even know of any body/metal works shops in my area that would do that or how much it'd cost though. A nicely welded aluminum tab would be fairly strong, right?

There's not a lot of stress on a chain tensioner. The derailleur hangers for aluminium bikes are made of steel and bolt on so as to be replaceable when they bend. A threaded chunk of compatible aluminium would work when welded on. That's the same way the dropouts are attached.
Since the tensioner's spring takes the load a clamping arrangement might work too.

Hm, I am not too keen with any possibility of compromising the structural integrity of my chainstay. I need a chain tensioner because I have vertical dropouts, it's a mountain bike. The fella at the bike shop said he could probably get my chain to fit snug without a tensioner, lies.

By changing tooth counts counts on chainrings and cogs and employing a half-link in the chain you can sometimes do it close enough but chain wear will eventually throw off the tension. Half-links are usually only available for 1/8" chain.

 

[Iron Yeti]

How about a tab welded to the chainstay?

If the stay is steel you could hack it off any deraileur hanger and weld it on.

Check to see that it would be in position to be effective.
Sometimes you can change the spring in a chain tensioner so it either pulls up or pushes down.

My chainstay is aluminum. I never thought of a tab welded on it. I don't even know of any body/metal works shops in my area that would do that or how much it'd cost though. A nicely welded aluminum tab would be fairly strong, right?

There's not a lot of stress on a chain tensioner. The derailleur hangers for aluminium bikes are made of steel and bolt on so as to be replaceable when they bend. A threaded chunk of compatible aluminium would work when welded on. That's the same way the dropouts are attached.
Since the tensioner's spring takes the load a clamping arrangement might work too.

Hm, I am not too keen with any possibility of compromising the structural integrity of my chainstay. I need a chain tensioner because I have vertical dropouts, it's a mountain bike. The fella at the bike shop said he could probably get my chain to fit snug without a tensioner, lies.

By changing tooth counts counts on chainrings and cogs and employing a half-link in the chain you can sometimes do it close enough but chain wear will eventually throw off the tension. Half-links are usually only available for 1/8" chain.

I'm leaning towards a clamp on chain tensioner. Only because I don't have the skills and/or money to have a tab made up for a tensioner. I'm kinda iffy on it though.

What type of directional force would be put on my chainstay? I am thinking having a rectangular chainstay might work to my advantage because of the angles there is less chance of slippage on the bracket.

I could use two lumps of metal with rubber footie pads to protect the frame, drill two holes in them with an extra bit of length on the outside one to mount the tensioner to. Rough em up and paint them black and voila. I'd need to bend the pieces of metal slightly to create a snug fit on the curved parts of the rectangle shape.

 

[64ragtop]

I'm leaning towards a clamp on chain tensioner. Only because I don't have the skills and/or money to have a tab made up for a tensioner. I'm kinda iffy on it though.

What type of directional force would be put on my chainstay? I am thinking having a rectangular chainstay might work to my advantage because of the angles there is less chance of slippage on the bracket.

I could use two lumps of metal with rubber footie pads to protect the frame, drill two holes in them with an extra bit of length on the outside one to mount the tensioner to. Rough em up and paint them black and voila. I'd need to bend the pieces of metal slightly to create a snug fit on the curved parts of the rectangle shape.

I think you're grasping the true spirit of the tinkerer, I.Y. Looking over the pieces you have and imagining what you want, then Imagineering the pieces needed to get from A to B. Sometimes just wandering the aisles of a well-stocked hardware or variety store looking for things shaped like the pieces needed will get ya there! Of course there are considerations of strengths of materials and other factors, not to mention the embarrassment of having someone realize that your elegant solution started its' life as a piece of "feminine hygiene" equipment, or an "erectile dysfunction" aid :lol: :lol:

ATB

BC

 

[dogman dan]

That is exactly how I McGuyver stuff all the time. Browse till you see things that will solve the problem. Flea markets, garage sales, and junk stores can also be good sources of wierd bits of metal that can do just what you need. Estate sales rock, since the old boy never threw out any metal in 70 years. If one clamp might slip, how about two clamps holding a bar that the tensioner bolts to?

 

[TylerDurden]

GarageSales rule: Cornerbraces, mending plates, turnbuckle, rollerblade wheel:

(I use 'Blender', which ain't CAD, but it helps me visualize. A hand-sketch would be just as useful, but I need the practice/learning opportunity.)

 

[Sturdly]

Nice simple and easy to execute design TD. Maybe a spring rather than the turnbuckle?

 

[TylerDurden]

Nice simple and easy to execute design TD. Maybe a spring rather than the turnbuckle?

Or both... the turnbuckle to establish primary tension, the spring to manage the slop/stretch.

 

[Iron Yeti]

Some great ideas here. Tomorrow I am going to cruise the local hardware stores looking for solutions.

 

[Rassy]

Okay I Y, now I can't wait to see what you devise and how it works. Remember, if your first try doesn't work just like you want it to, it gives you better ideas for the next version. Good luck.

 

[Iron Yeti]

Hey guys, look what I found.
http://www.ebikestop.com/kore_chain_reactor_tensioner___black-21023.php

I am almost positive that mounting bracket won't be suitable, but all I need to do is remove it, whip up a custom bracket and bolt on the tensioner arm!

 

[64ragtop]

It kinda looks like they tried to make the bracket a universal fit - difficult to tell from that angle, but you might get lucky and not have to work up a new bracket. Maybe just carve up some rubber bits from a discarded bike tire to fill in any angles that don't work with your stays. Looks like you're almost there!

ATB

BC

 

[Iron Yeti]

Hey dudes. Just got off the phone with the bike store fella. I am happy to have a guy like him in my area to work on my ride. He wasn't trying to screw me or doing a sloppy job. Absolutely everything he did to make sure my bike got finished and was working correctly.

-Issue one: The Nuvinci uses two shifter cables and they need to be the EXACT same length or it compromises shifting, also, they cannot be exposed at all, the friction impairs shifting. So he ran them on the bottom side of my front triangle because running them through my old brackets would have meant the cables would need to be two lengths.

The fix: My old shifter cable housings were saved. The first two running from the shifters to the first clamp on the top of my frame measure 17 inches exactly each, then between the two clamps on the top of my frame there is a 13 in gap were the cable were left bare. Running from the last bracket the cables split their separate ways, one goes down the rear triangle to another bracket and then the bare cable goes to the dérailleur, one goes down the seat stay to a clamp and then the bare cable goes to a front dérailleur. Coincidently these two sections are 11 inches each, but I won't be using them because I am just going with one jumbo 22 inch cable down the rear to the housing.

So I called the bike store fella (Matt, it feels so impersonal calling him a fella) And said, will you help me? He said absolutely. So I asked him to make me some custom outer housings. 2x 13 in cables to go between that gap on the top of the frame, 2x 22 in cables to go from the last bracket on the top of the frame down to the housing (Which I turned to point upwards to facilitate the cables)

How am I going to secure the cables to the frame where there is nothing to hold them in place? Well, on the top of my frame in the center there are two lumps with slots in them that two little brackets click onto. Coincidently the nifty adjustable removable zip ties I found at the hardware store fit perfectly in these brackets and will be most suitable for holding the two extra lengths of cable down on the topside, they look exactly like the old clamps too. On the rear triangle I plan on using 2x of these nifty zip ties because they are flat, and their zip tie head thingies are not pronounced so I can just hide them on the backside. Problem fixed!!

Next issue: The tensioner. Well I've already figured that out. But it will have to wait until I get more money. For now I will just poke around looking at clamping options.

And lastly. The color of the rim. In the spring I am going to take the rear wheel off and rough it up and spray paint it. The problem is he was worried any other rim would be too weak to hold this big hub. So the only beefy one he could find had was reinforced with stainless steel that were meant to be used as gripping surfaces for frame mounted v-brakes. He said he'd restring it if I really wanted but he cautioned me about the weight. So my solution is just gonna be to paint it in the spring along with the two arms on my cargo rack.

And that's that. I will have the two 25 in and two 13 in cables in hand Wednesday, and hopefully Nuvinci will send me the two extra cable lengths I ordered in a week before I go camping.

 

[Iron Yeti]

Sorry for the double post. I almost shat out my heart. I was reading about Kore's chain tensioner and look what I found.
http://www.kore-usa.com/old_site/dreactor.htm

Universal Clamp
The Chain Reactor has a special clamp design that allows the Chain Reactor to fit all round, square, and oval chain stays. The clamp also features a slot cut on the inside to allow your rear derailleur inner cable to pass through. The clamp has two double bolts angled outward for easy installation and adjustment.

Woohoo! I lucked out!

 

[TylerDurden]

Not exactly hose clamps and angle iron, but it might just work!

 

[Iron Yeti]

Not exactly hose clamps and angle iron, but it might just work!

Haha, don't worry buddy, there will be some modding. According to reviews the hardware sucks. So I will replacing the bolts with nylon bolts, and on the clamp I will most likely need to use a longer bolt. It's also been suggested I replace the brass bushings with some mini ball bearings.

I'll also be using, *gasp* a piece of old inner tube to protect the frame and create a less slip resistant surface.

There's your stinkin' mods!