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Thread: Spring Return Chain Tensioner
04-29-2011 #71Motorized Bicycle Member
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Spring loaded idler [ tensionizer ]
The idler looks OK, a bit heavy I'm sure, but what troubles me is the concept of
' Any ' type Tensioniser falling into the spokes . I favor the seat post Tensioniser, which can't . Pirate Cycle showed me a built in sprocket idler, which looks very heavy duty, and light weight, as its built into frame. Trouble is, it has no adjustment, or spring bounce. When I built my " Gusseted Idler " I designed it so it can't fall into spokes, should it break. At the time, I had no knowledge of seat post tensionisers, and feared the stock offering.
The instructions that came with my grubee kit showed the stock idler in illustrations, mounted to either the chain stay, or the seat tube. My bike has much too fat a seat tube for that but it might work on skinny 10 speed frames. Tension is regulated by the placement of the tensioner on the seat tube, and position of the idler bolt in the slot.What works: stick to friction drives and single speeds, get some real brakes and wheels. Don't try to go 50mph on a bicycle.
Old topic but interesting idler.
I was actually just looking for a comparison of 410, 41, and 415 chain but what the heck.
I am just curious as to why a spring tension with play?
If it's just to take up slack as the chain and sprockets wear so you don't have to adjust it? that's pretty cool.
If it's just a work around for not getting the rear sprocket mounted true (chain get tight then loose when you roll it) it seems like an expensive way to get out of just mounting the rear sprocket true.
Heck, on 7-speed builds with horizontal dropouts and it's own tensioner I don't use any drive chain tensioner most of the time, I just size the chain right and let moving the back wheel adjust the drive chain tension.
For that matter some bikes like this Phat motorize so nice I didn't need a drive side tensioner at all, after 5 miles of easy breakin miles with the pedal chain a little loose and plenty of room to move the wheel back I got both chains to match up very well.
I'm not dissing this clever tensioner, it's a very clever design especially if you can't get a stock tensioner to stay on the chain stay.
For the bikes (or customers) that need an adjustable drive chain tensioner I always keep it coming loose and going into the spokes in mind.
I like to size the chain to put the idler forward just past the rim so if it does come loose it hits the rim and doesn't go into the spokes like this.
With a little paint the thing pretty much disappears too.
Anywho, just a different perspective on an old topic.KC's Builds
It's all how you look at things ©¿©¬
huh? im trying to look for a spring tensioner but the pic keeps changing!
all i see is the chain guard, the stay for the rear brakes, and thats it...no tensioner...
and the blacks just a stock one...
problem with spring tensioners is getting the pivot right to actually take up slack effectively, as well as have enough pressure to withstand starting(always having the sprung side on the "return" side of the chain) whilst not having so much pressure it destroys the chain or makes a horrid wirring sound...
been there, done that, welded the thing onto the stay eventually...
The tensioner does a lot to dampen vibration. It can also compensate for slight chain wear. It can make tire changes easier.
If you only use a tensioner to take up 1/2 to 1 link, it can be a much more stable system, especially when starting. If you have the heavy chain, it will be much less prone to jump off.
Last edited by happycheapskate; 04-30-2012 at 08:25 PM.What works: stick to friction drives and single speeds, get some real brakes and wheels. Don't try to go 50mph on a bicycle.
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