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Single Speed Tensioners


scott-mad

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dmr tension seeker - purely shit, bad design chain slips off, just crap

surly tension device - same as above, spring is wank

fresh-products - great design, works well, for those who just want simple but effective

rolhoff tensioner - like a mech, spring is truly awesom, very strong but expensive

but the winner is

locked out rear mech - perfect, works well, can still change gears with a screwdriver, lightweight, and cheap, as you could use a £5 mech and it would still be good.

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I've been running a Rohloff. It works well but stupidly expensive and is fiddly to fit.

Out of curiousity I've just put on one of the springless DMR ones which looks like below (but with a different logo on it & with less chain length and slack)

dmr-c.jpg

It works on the same principle as the Rennen, which the Fresh tensioner is based on:

rennenTensioner.jpg

This method is well received in the Trials community, with increasing numbers of UK riders running the Fresh one and I read that the Rennen is a firm favourite over in the US where it's easier to get hold of. I haven't had time to ride the DMR yet, but it certainly looks smart tucked away, and was very simple to fit. It was cool to be able to remove a couple of extra links from my chain and now it looks very short and efficient. From feedback I've read on TF I think that it may be some of the finer details with which have caused frustration with the DMR version, because the principle seems to be sound.

These are namely that the lower bolt snaps easily (it's made in Alu so is no doubt meant to break rather than transfer the knock to the frame) and I've also heard (rumour and hearsay!) that the roller wears quickly. Another point is that for some reason DMR have used a seperate part to join the axle to the tensioner (see the third bolt which is attached to a black Alu part that fits onto the axle), which seems an example of over complicating things. The sprung DMR tensioner I also have gathering dust is overcomplicated with loads more parts than needed, and it also requires a large number of different sized Allen keys including all the small ones that are lost somewhere down the back of the sofa. Maybe this 2 part design is less robust than the Rennen/Fresh one-piece design for those side hopping accidents. I'll soon find out it if can take the knocks because my sidehops are pretty rubbish!

I was thinking that the bolt and roller can be sorted out by fitting other parts, which admittedly does involve some hassle and cost, but basically may allow the DMR to be used reliably. For example instead of the Alu bolt I've used the Rohloff's steel one, and I've paid close attention to not over tension the chain which may accelerate the roller wear. It will certainly be very simple to get some replacement rollers made up and try a variety of materials should the durability be an issue.

I'm going to see how it performs over time.

Steve

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I had a design completed based on an easier to fit Rohloff type tensioner. The problem was that it cost more than 2x to make compare to the RRP that I had in mind! Also there are some spring retention problems if the two sprockets can be adjusted.

Here's a sneak peek of some CAD - the off the shelf parts are missing since this was for a machining quote:

If springless designs are the way to go, then this is good news for bringing the price down to around the cost of a mech, which is what I had in mind originally.

But I'm not sure if I want to make another tensioner that works on the Rennen concept when Aaron has already put so much work into his, so I have no immediate plans especially since I already have my hands full working on new booster variations, pad testing and moulding plus Alu Magura backings.

Thanks for your interest though!

Steve

When is Heatsink tensioner coming out? got any proto picutres of it?

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I had a DMR tension seeker and EVERTHING went wrong with it and it bwoke :P I have now just got a tiagra mech and it works looooovley :P (I'm using a cable tie to stop it "clanking" against the frame) :) :)

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I had a DMR tension seeker and EVERTHING went wrong with it and it bwoke :P I have now just got a tiagra mech and it works looooovley :P (I'm using a cable tie to stop it "clanking" against the frame) :) :)

but why are you using a zip tie. this reduces any chance whatsoever of using gears, if you want to be able to use the mech properly (i.e easy adjust chainline, can change ratio's easier) then take mech off, remove 'c' clip spring will pop out, put plate back on (leaving spring away) tighten up in desired position, stops clanking, alows use of rear deraillier.

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How does the Leeson tensioner work?

This photo shows how: I can't see a spring there, and interesting to see no channel on the roller. Simple is indeed good (Y) You can see that it mounts onto 2 Leeson specific mounts on their frames and one bolt is used to hold the roller in the desired position either above or below the chain.

Steve

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How does the Leeson tensioner work?
What Steve said, although mine has a groove in the roller. Not sure that a groove in the roller is a good thing - If it gets slightly bent, the chain tries to roll out of the groove and obviously that makes the chain tighter, so the chain ends up being too tight. If I was making one, I would not have a groove in the roller, so even if the tensioner is knocked and bent slightly it will still work fine. Anyway, the Leeson KISSS basically works like the Rennen/Fresh ones in that there is no spring, but because of the Leeson mech hanger situation (see pic) it obviously bolts on in a different way. As there is no spring, the key is in making it sturdy enough that you can tighten it hard and that it stays tight. Also, get a roller with a bit of "give" in it and it will take up the bumps etc. It seems to work well, anyway.

It's the best tensioner I've used, but it's not perfect - it still needs tightening every now and again, and when you knock it, it loses all tension, so you need to take an 8mm spanner out on rides. No big deal but it's an extra something to remember. Unfortunately you can't get one unless you've got a Leeson (Y)

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What Steve said, although mine has a groove in the roller. Not sure that a groove in the roller is a good thing - If it gets slightly bent, the chain tries to roll out of the groove and obviously that makes the chain tighter, so the chain ends up being too tight. If I was making one, I would not have a groove in the roller, so even if the tensioner is knocked and bent slightly it will still work fine. Anyway, the Leeson KISSS basically works like the Rennen/Fresh ones in that there is no spring, but because of the Leeson mech hanger situation (see pic) it obviously bolts on in a different way. As there is no spring, the key is in making it sturdy enough that you can tighten it hard and that it stays tight. Also, get a roller with a bit of "give" in it and it will take up the bumps etc. It seems to work well, anyway.

It's the best tensioner I've used, but it's not perfect - it still needs tightening every now and again, and when you knock it, it loses all tension, so you need to take an 8mm spanner out on rides. No big deal but it's an extra something to remember. Unfortunately you can't get one unless you've got a Leeson :P

the leeson tensioner works put better when it is uptensioned - thats what i have found. Because mine is down tensioned at the moment and keeps coming loose on big kicks and if i do the tensioner up really tight, it still moves, but slower and is then too tight to move by hand.

so i have mine loose-ish now and just have to push it down by hand, but requires no tools and takes about 2 seconds :- - it probably does help i have stripped the metal hander plate and my tensioner is held on by zip ties (Y)

anyhow will be getting a new chain in a couple of months and will go back to up tensioning, which is better.

mike

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