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Streetmachine GT idler pulley

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Kim View Drop Down
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    Posted: 10 September 2020 at 5:11pm
The drive-side idler on my SMGT has died, more specifically the smooth elastomer-ish bit that the chain runs against has disintegrated from wear - the bearings themselves are fine.

Does anyone have any ideas where I might source a replacement that doesn't involve selling my soul to HPVelotechnik?

(Note that this is the older GT model - they changed the idler in the GTE, and the Terracycle offering doesn't fit.)

It looks an awfully lot like a section of large-diameter hose.  I could probably get a metre of that and a hacksaw...


Edited by Kim - 10 September 2020 at 5:18pm
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AlanGoodman View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote AlanGoodman Quote  Post ReplyReply Direct Link To This Post Posted: 10 September 2020 at 8:32pm
May be worth giving Mike Burrows a shout... May have something lying around or be able to make something suitable.

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Kim View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Kim Quote  Post ReplyReply Direct Link To This Post Posted: 10 September 2020 at 9:46pm
I found a source of fuel hose (which I assume shouldn't get too upset about chain oil) of almost exactly the right dimensions, so I'm going to give that a try in the first instance.  Even if doesn't stand up to the wear very well, you'd get a lot of replacements from a metre of hose.
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Kim View Drop Down
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Kim Quote  Post ReplyReply Direct Link To This Post Posted: 12 September 2020 at 6:01pm
The size is good, but the steel reinforcement makes it a bit lumpy at the edges.  Not sure how much of a problem that's going to be in practice.  Will find out when I ride it...






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Post Options Post Options   Thanks (0) Thanks(0)   Quote antonin_d Quote  Post ReplyReply Direct Link To This Post Posted: 26 November 2020 at 9:04pm
Hi Kim,

I am late on the ball, but I have replaced the original idler on my SMGT by a much simpler idler. I got the one I currently use from ICE at the WC 2019 (many thanks to them!).

I never really understood the point of the foamy original idler to be honest. Why does it have to be soft? Isn't it the goal to have something stiff that actually transmits the force without compressing any soft part?

Cheers from Germany
Antonin
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Kim View Drop Down
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Kim Quote  Post ReplyReply Direct Link To This Post Posted: 26 November 2020 at 10:21pm
I've always assumed the reasoning is that with this the chain is free to move side to side and not-really-engage if the chainline (gear and boom length depending) permits it.  It does seem like an inferior approach to a toothed idler, which seems to be how most recumbents do it today (including HPVelotechnik's current models).  Possibly an attempt to reduce noise?

Anyway, the bit of hose is doing well after about 2100km.  I found that if you pulled the steel reinforcement out with pliers it maintained a much better shape.
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