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Tern link D7I chain tensioner

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Old 02-02-18, 05:43 AM
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JohanNeeda
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Tern link D7I chain tensioner

I have a Dahon link D7i and I wonder if somebody has attempted to fit a chain tensioner (kind of it makes sense for an IGH). The real problem is that on the inside there is no space (the hub fills all the space between the dropouts) and on the outside there are the non-turn washers.
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Old 02-02-18, 11:12 AM
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Originally Posted by JohanNeeda View Post
I have a Dahon link D7i and I wonder if somebody has attempted to fit a chain tensioner (kind of it makes sense for an IGH). The real problem is that on the inside there is no space (the hub fills all the space between the dropouts) and on the outside there are the non-turn washers.
Two questions:
1) Is it a Tern or a Dahon?
2) Why would you need a chain tensioner on a frame designed for an internally-geared hub? Just re-position the wheel.
Steve
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Old 02-02-18, 11:41 AM
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JohanNeeda
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Hi Sweeks,
I'm used with my Gazelle bike IGH and that one has a chain tensioner(s) more like the BMX type. Apart of the "use" part they will not allow the back wheel to go forward while climbing heels which happened to me already as I was not used to really tide up the nuts. Very embarrassing...


BTW it is a Tern.
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Old 02-02-18, 11:49 AM
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Originally Posted by JohanNeeda View Post
BTW it is a Tern.
The nuts definitely need to be tight. If the chain is too long, it can be shortened. A chain tensioner would be an unnecessary complication; these are usually used on bikes with internally-geared hubs whose frames have vertical rear drop-outs. Re-positioning the wheel doesn't affect chain tension much, if at all, with vertical drop-outs. Your Tern has horizontal drop-outs.
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Old 02-02-18, 12:00 PM
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Originally Posted by sweeks View Post
The nuts definitely need to be tight. If the chain is too long, it can be shortened. A chain tensioner would be an unnecessary complication; these are usually used on bikes with internally-geared hubs whose frames have vertical rear drop-outs. Re-positioning the wheel doesn't affect chain tension much, if at all, with vertical drop-outs. Your Tern has horizontal drop-outs.
Steve
OP is probably talking about something like THIS, a chain tug..

For the OP, faced with the same issue, I've also run the anti-turn washers in front of the hub if there is room .. or, just one on the non-drive side and the chain tug on the drive side.. sometimes you have to modify things to reach your objective..
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Old 02-02-18, 12:14 PM
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If this is what the OP has, there are chain tugs that can be found to replace the yellow anti-turn washer..

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Old 02-02-18, 12:46 PM
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Originally Posted by BruceMetras View Post
OP is probably talking about something like THIS, a chain tug..
Yeah, I thought of that but figured I'd just take the OP at his word.
Steve
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Old 02-02-18, 12:49 PM
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JohanNeeda
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Originally Posted by BruceMetras View Post
OP is probably talking about something like this a chain tug..

For the OP, faced with the same issue, I've also run the anti-turn washers in front of the hub if there is room .. or, just one on the non-drive side and the chain tug on the drive side.. sometimes you have to modify things to reach your objective..


brr... it's a tug indeed. There is no room in front of the hub. I have seen someone modifying one with a file (which seems a good idea) but it seems I'm not able to find one already made. It seems non-turning washers take some tension due to the hub and they can brake (ha!).
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Old 02-02-18, 01:12 PM
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Originally Posted by JohanNeeda View Post
brr... it's a tug indeed. There is no room in front of the hub. I have seen someone modifying one with a file (which seems a good idea) but it seems I'm not able to find one already made. It seems non-turning washers take some tension due to the hub and they can brake (ha!).
You should be able to tighten the wheel nuts enough that the wheel doesn't slip. However, using a tug-nut on the drive side is fine *as long as* there is adequate "non-turn" function. If non-turn function is limited to one side (most likely the non-drive side in this scenario), the non-turn washer can rip out the drop-out (see attached image, from Aaron's Bicycle Repair). This is a bad thing; for one thing, the axle may not rotate or the gears will not shift. It's possible that the hub can be damaged (see the other attached image).
Steve

EDIT: Looks like some of those chain tugs have non-rotation features. That's good. Also, you don't really need one on the non-drive side unless you really want it.
Attached Images
File Type: jpg
nonturnwasherdamage.jpg (96.5 KB, 58 views)
File Type: jpg
brokenaxletab.jpg (200.7 KB, 56 views)

Last edited by sweeks; 02-02-18 at 01:18 PM.
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Old 02-02-18, 06:12 PM
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We sell these bikes (awesome bikes BTW. My favorite Tern model and configuration) and haven't had any problems with the chain loosing tension just pulling the wheel back and tightening down the nuts. I don't think anything else is necessary.
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Old 02-02-18, 09:02 PM
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Originally Posted by odiolalluvia View Post
We sell these bikes (awesome bikes BTW. My favorite Tern model and configuration) and haven't had any problems with the chain loosing tension just pulling the wheel back and tightening down the nuts. I don't think anything else is necessary.
This has been my experience as well with a Verge S11i over about 4 years and 5,000+ miles.
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Old 02-06-18, 04:03 PM
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Originally Posted by sweeks View Post
This has been my experience as well with a Verge S11i over about 4 years and 5,000+ miles.
Steve
Thank you all for the time spent to answer my question. So shall I understand that nobody actually attempted to have tugnut on a Tern D7i? This seems to be the answer. About the needed/not needed, “it works fine on my folding bike”. I will tell you a story:

Ones upon time was a biker that really loved bikes. Not a bike mechanic but still reasonable, mechanically aware biker tinker. To pick up kids from school he needs 25 minutes. He left most of the time 30 minutes in advance ... just in case. Ones that “in case” arrived when he got a flat tire on his brand new, on maiden voyage Tern Link D7I bike. No problem: he uses one of the 2 co2 canister to inflate the tyre. Unfortunately it will not hold, so changing the tire is required. No problem either. With an IGH is not easy but the tyre is changed and inflated with the second Co2 cartridge in 3 minutes flat (being a owner of another bike with IGH obviously helps). Hurray! Good for him! But wait a minute... the inflated wheel will not pass the brake pads! (that’s on him as this is the first bike with v-brakes, so he should have check this first). So he deflates the wheel, passes the brake pads, attaches the non turning washers and nuts . Now it comes the tedious task to centre the wheel in the fork, while pulling it back to tension the chain and tide the nuts with a bicycle mini wrench. That takes him about 15 minutes. Deflated tire need to be inflated as well this time with the mini pump. The alignment is not perfect (with the bike upside down, in the twilight and rain is a real black art) and the nuts are not hyper tight either. He is quite late to pick up the kids so ... high gear and up in the saddle for up-hill. Poor guy... poor mechanics never forgive: the wheel slips forward and the 4th gear of the IGH gets damaged. No time to readjust the wheel so ... he locks the bike starts running. He got there 15 minutes later that it should have been and, of course, a lot of angry looks from the school personnel which were about to call the police (standard procedure when parents do not show up).

Lessons learned: 1) inflate the wheel after passing the brake pads and 2) get the tugnuts (aka chain tensioner).

I found it a lot easier adjusting the wheel for both chain tension and position one small step at the time. The only thing I find amazing is that on the D7i the front wheel has some kind of markings where to put the washers so the wheel will fall always in the correct position. Why the back wheel has no such thing (e.g. tugnuts :-)) is beyond me.
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Old 02-06-18, 04:16 PM
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Originally Posted by JohanNeeda View Post
Lessons learned: 1) inflate the wheel after passing the brake pads and 2) get the tugnuts (aka chain tensioner).

Why the back wheel has no such thing (e.g. tugnuts :-)) is beyond me.
1) Depending on the tire's width, releasing the brake noodle usually provides enough clearance. I hear you, though. I've occasionally had to partially deflate a tire to get past even a released brake... that's why I carry a pump.

2) I've got 3 folders (2 Dahons and a Tern) with IGH, and after a combined ~20,000 miles have never had a problem with wheel slippage. However, different riders will have different requirements... "Different strokes for different folks".
There's no shame in adding a tugnut, but I think they *would* be standard equipment if this were a common problem.
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Old 02-07-18, 02:59 AM
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Hello,
thank jou Johan this tugnut thing seems worth a look... I haven't tried dismounting the rear wheel fro my C7i yet.
I just came to think it would be a good idea trying the procedure in a warm and well lit room for the first time :-)
Johan, maybe e telephone call to those keeping the kids was an option? My doughters are 18 and 20 now, but I understand your feelings, I have gone through similar situations in the past. Comunicating is very very easy these days. Bye, Marco
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