Author Topic: Idler question  (Read 525 times)

Blodwyn Pig

  • what a nice chap
Idler question
« on: January 29, 2021, 08:24:24 pm »
The plastic chain idler on Grunhilda  (Streetmachine GTE) has 'lumps' worn in the center bit. Are these teeth that have worn away, or just the plastic getting chewed up by the chain?

LMT

Re: Idler question
« Reply #1 on: January 29, 2021, 10:13:25 pm »
Usually idlers that are the drive part of the drivetrain have teeth and return/guide idlers are usually smooth plastic/rubber.

Kim

  • Timelord
Re: Idler question
« Reply #2 on: January 30, 2021, 12:30:13 am »
The Streetmachine GT is an exception, using a smooth drive-side idler for reasons that probably made sense to whoever was designing it (my guess is to allow for horizontal chain movement).  The plastic part of mine recently disintegrated, after about 32k miles.  On the basis that the bearings were fine and it looked for all the world like a section of PVC hose, I tracked down a source of high-pressure marine fuel hose of the appropriate dimensions, and molished a replacement from that.  It's survived about 1000 miles so far, and I've got nearly a metre of hose left, so I'm quids-in.

I know the GTE uses a different idler design, for which a toothed idler replacement is available from Terracycle (not sure if the original is toothed).  The GT one is unobtanium.
Careful, Kim. Your sarcasm's showing...

Blodwyn Pig

  • what a nice chap
Re: Idler question
« Reply #3 on: January 30, 2021, 07:56:58 am »
I did some googling. The purpose of the idler , in this instance is to reduce / eliminate the pogo effect of the rear suspension. When you look at the idler, it doesn't look like it's doing anything, but when you sit on the machine, things change, and you can't see. As the rear settles with your weight on it, or a load, the idler then keeps the chain down close to the pivot point of the rear swinging arm. One chap ( bentrider online) removed the idler due to the noise, and noted that the bike was almost silent. Then another reader, said that he had removed the one thing that stops the pogo.  Ah! Said the first, I had noticed it bobbing up and down more, but thought the rear shock was on its way out. The plastic idler should be smooth, but Terracycle do a 23 t idler in alloy, about¬£70 , but ¬£18 shipping outside Europe from Germany. ( if they will even ship to UK, now ) . I might try and wrap the surface in tape, of 'rings'of MTB inner tube, it really is quite chewed up.

Blodwyn Pig

  • what a nice chap
Re: Idler question
« Reply #4 on: January 30, 2021, 10:05:28 am »
IMG_1537 by mark tilley, on Flickr

IMG_1538 by mark tilley, on Flickr


Ok, fettling time,this is what it looks like.Hmmmmmmmmmmmmmmm! what can I do???  I know!

IMG_1539 by mark tilley, on Flickr

Take one ' biggest old tube, what I have got in my cupboard' type thing

IMG_1540 by mark tilley, on Flickr

Cut some strips wider than the width of the pulley

IMG_1541 by mark tilley, on Flickr

Strech over the outer sides and plop in the middle. Ah! problem....It doesn't fall in square, but rolls over....Hmmmmmmm.  Ah!

IMG_1542 by mark tilley, on Flickr

yes! works a treat. 4 layers of tube .....

IMG_1544 by mark tilley, on Flickr

seems to be much quieter now. But too wet to try in anger.   Laters!

PS This is my ''Terrorcycle' modificaton.

Kim

  • Timelord
Re: Idler question
« Reply #5 on: January 30, 2021, 12:22:54 pm »
I did some googling. The purpose of the idler , in this instance is to reduce / eliminate the pogo effect of the rear suspension. When you look at the idler, it doesn't look like it's doing anything, but when you sit on the machine, things change, and you can't see.

This is what the 'no squat' business is about - keeping the chain in the right line with respect to the rear suspension pivot.  AIUI the Streetmachine was the first recumbent to get it right, though they pretty much all do it these days.

How much the idler engages depends on suspension travel, boom extension and what gear you're in.  It's a lot quieter than it has any right to be.
Careful, Kim. Your sarcasm's showing...

Kim

  • Timelord
Re: Idler question
« Reply #6 on: January 30, 2021, 12:32:44 pm »
IMG_1538 by mark tilley, on Flickr

That looks like the (non-toothed) idlers that ICE use after they've been worn in.


Quote
IMG_1544 by mark tilley, on Flickr

seems to be much quieter now. But too wet to try in anger.   Laters!

PS This is my ''Terrorcycle' modificaton.

Not dissimilar from the non-drive-side idlers that use a simple O-ring as a sacrificial surface.  Of the two on the Baron, I find the foremost one (at the fork crown) gets chewed up at a higher rate, due to the chain slapping about with every bump in a way that doesn't really happen on a Streetmachine, and occasionally taking chunks out of it.

I suspect the limiting factor will be how well the rubber stands up to chain oil.  I use bands of inner tube like that to stop my cycle computers going flying, and find they disintegrate after a year or so, presumably from the UV exposure.
Careful, Kim. Your sarcasm's showing...

Blodwyn Pig

  • what a nice chap
Re: Idler question
« Reply #7 on: January 31, 2021, 12:54:21 pm »
50km ride update.......it was ...as you say in England,  ''well quiet, innit''

Re: Idler question
« Reply #8 on: January 31, 2021, 01:21:26 pm »
Nice bodge to extend the idler lifespan