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Chain Tensioner


zoo p

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looks good!

wouldn't put "zoo" on it though..... may get done by copyrighting people :-

looks like the dmr one though, will this one work??

B)

ok if anyone asks it says zdd ok?!

and it will because it attaches in a similar way to the fresh products tensioner.

i haven't decided what colour to anodize it yet so purple is a possibility

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It looks like you've already spent some time on thinking it out :-

The concept works well as time proven by the original Rennen designs tensioner, not so common in the UK, but becoming the robust tensioner of choice in the USA and Canada.

If you haven't already, I'd suggest printing the design out 1:1 and cutting it out when double sided sticky taped mounted on some card to double check the mounting positions for the axle hole & mech bolt slot, make sure the arm is a good length, the post the right length etc.

One design suggestion: Should the underside of the frame take a knock, it may make sense to protect the chain from being damaged. You could extend the underside form of the arm to form a large enough semi-circle concentric with the roller, or you could ensure that the roller has high enough sides. In terms of making the tensioner as robust as possible It would make sense to go for the first option, because landing on the cantilevered roller would cause more damage to the tensioner than if you designed it so the underside of the arm got hit instead.

The floating roller idea works fine. I notice you've not shown the mounting bolt for the lower mech (the one that runs in the slot) If you don't have one from a previous tensioner then you'll have to work out how you'll tackle this. If you wanted a pukka job, then ideally it would be a custom bolt with a M10x1mm pitch thread, flange and 5mm allen key head. This may or may not be straight forward using the equipment available to you, and you may have to go for a hex head instead for simplicity. Alternatively, and less attractively you could use an M8 and nut, fiddlier to set up and which would run the risk of ripping up the mech hanger threads if the slot was incorrectly placed allowing interference.

If this is intended for your own bike, then this simple design is efficient and all you need. If it was a commercial product however there are some additional issues to be aware of to potentially tweak the design. Firstly, incompatibility across some frames since it's come to my attention that the positioning of the hole and slot will require some riders to have to bodge to allow fitment. Also, looking at the context of trials riding, where realignment following regular knocks should be made as straight forward as possible, I'd argue that this would be easier if you split the arm into 2 parts so that one is permanently attached to the axle, and the other can be moved relative to this part. This is the way the rigid DMR tensioner is designed, argueably let down by a weak sacrificial Alu mech bolt.

When I'm setting up the rigid tensioner I made myself, I find it awkward to simultaneously get the wheel sat right (the drop outs allow the wheel to be at an angle unless you put your weight on the frame), and simultaneously get the tensioner spot on. I just don't have enough hands, and also I need to be in two different positions at once to get each sorted properly. I find that I'm pushing down on the seat as I tighten the QR, above the frame rather than side on and close up to check the tension is spot on. As a result, it takes me a few goes to get it all set-up satisfactorily, even though I've got more slack than I'd like in the chain since it's hard to fine tune juggling both things. The thought of having to repeat this awkward and iterative procedure if the tensioner gets knocked, isn't very attractive. If I had King Fun Bolts, then it would carry the added inconvenience of requiring me to carry a cumbersome 8mm allen key with me when out riding.

I like the DMR rigid concept where all I need is a 5mm allen key with me, and no need to loosen and tighten the axle at all. Simple to get the tension spot on, and with the addition of a replacement steel bolt, the tensioner is spot on in my opinion.

Good luck!

Steve

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Erm...pretty colours aside , well done . My concern is with the wheel , these are often worn down , especially by very tight chains , leaving a groove in which the chain becomes trapped . Replace the guide with a conventional jockey wheel . That said , I doubt your product design examiner will have overly insightful critiques from a rider's perspective .

The Zoo ! logo ? That falls somewhere between corporate a**e kissing , and overly wishful thinking . Hope you get decent grades .

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i have heard a lot of talk about this chain tensioner from you but this is the first time i have seen a pro D image of it and it looks pretty damn nice!!

gotta agree with dan that having it anodized gold would make it go with the rest of your bike!!

if your cnc'ing it you should make a couple of them

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phantom_of _the _trialser should have a seven day suspension for posting random crap on this forum, it takes up too much space and there is no need at all, and like i told you today if your cnc'ing it u should definatly make a couple cos it would be easy. (Y)

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