Author Topic: thorn chainguards  (Read 3856 times)

anweald

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thorn chainguards
« on: August 20, 2009, 10:25:53 PM »
Anyone know the exact dimensions of the Thorn chainguards esp the one for PCD 104mm for 44t rings? Also its weight and how it manages to not get in the way of the chain.

I'm really only wanting a trouser-hem-saver but those plastic chainring attachments don't seem available to buy separately. maybe they're not as light as they look anyway.

pyjamas

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Re: thorn chainguards
« Reply #1 on: November 17, 2014, 10:17:28 PM »
I saw an elderly lady with one of those very upright bicycles: when she was holding the bike, the handlebars were up near her chest.  She had hub gears, obviously, and a fully enclosed chainguard.  What struck me was that a Rohloff hub gear should also be suitable for a chainguard, which should go a long way to protecting the chain from wear.  Has Thorn ever considered this, or ever fitted Rohloff bikes with chainguards?
 

JimK

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Re: thorn chainguards
« Reply #2 on: November 17, 2014, 10:21:40 PM »
Here is my big clever idea:

I think a big problem with chain guards is that fitting them is very tricky. They need to hook onto or clear so many surfaces... maybe a perfect application for 3-d printing!?

il padrone

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Re: thorn chainguards
« Reply #3 on: November 17, 2014, 11:04:27 PM »
A number of people on here use and recommend the Hebie Chainglider. There is one made specifically for the Rohloff hub. These are lighter plastic guards that do not need frame fittings. I have one that will go on the bike when the current drivetrain wears out. Note: the Thorn double-sided chainring does not run with the Hebie, it's too wide and causes friction. Use a thinner alloy or steel ring.
« Last Edit: November 17, 2014, 11:06:02 PM by il padrone »

John Saxby

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Re: thorn chainguards
« Reply #4 on: November 17, 2014, 11:22:38 PM »
+1 for the Hebie Chainglider, in my case fitted to my Raven with a 38 x 17 ratio.

Beyond the various Hebie products, however, there's a huge range of possibilities here:  http://www.dutchbikebits.com/index.php?route=product/category&path=43

Andre Jute

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Re: thorn chainguards
« Reply #5 on: November 18, 2014, 03:53:33 AM »
I saw an elderly lady with one of those very upright bicycles: when she was holding the bike, the handlebars were up near her chest.  She had hub gears, obviously, and a fully enclosed chainguard.  What struck me was that a Rohloff hub gear should also be suitable for a chainguard, which should go a long way to protecting the chain from wear.  Has Thorn ever considered this, or ever fitted Rohloff bikes with chainguards?

Try these threads:
http://www.thorncycles.co.uk/forums/index.php?topic=2233.0
http://www.thorncycles.co.uk/forums/index.php?topic=3561.msg15501#msg15501
http://www.thorncycles.co.uk/forums/index.php?topic=6813.0
http://www.thorncycles.co.uk/forums/index.php?topic=2480.0

pyjamas

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Re: thorn chainguards
« Reply #6 on: November 26, 2014, 09:46:59 PM »
Many thanks for all these responses: a lot for me to work on.
 

Matt2matt2002

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Re: thorn chainguards
« Reply #7 on: November 26, 2014, 11:11:22 PM »
I'll second the Chain glider.
I've had it on a month, done 100 miles, so still braking it in so to speak.
But being early days I have paid extra attention for new noise and can hear none at all.
It may be a rash statement but I feel the Raven glides along even quieter than before fitting it.
Never drink and drive. You may hit a bump  and spill your drink

phopwood

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Re: thorn chainguards
« Reply #8 on: November 27, 2014, 10:19:16 AM »
I fitted one about a month ago it needed trimming to fit my RST, but I have a thorn alloy ring which is very wide and it took a lot trimming around the edge where it was touching the ring.

I should have brought a thinner ring.  It still rubs in places as I can hear it, but I am sure it will break in eventually, or I will take it apart and adjust it's expectations with a stanley knife  ;D  That said I don't feel like it drags or adds much friction.

All the best.

Peter

in4

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Re: thorn chainguards
« Reply #9 on: November 27, 2014, 10:44:05 AM »
Anyone have a preference re bashguards?

John Saxby

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Re: thorn chainguards
« Reply #10 on: November 27, 2014, 05:59:44 PM »
Quote
I feel the Raven glides along even quieter than before fitting it.

Matt, glad to know you've had such good luck with the 'glider.  Last week, I took mine apart after this first season (May to November, about 3,000 kms) and the chain is quite clean -- some dust, no grit at all.  I cleaned it anyway, as much out of habit as anything.

I'm going to try fitting the 'glider a fraction looser next spring -- mating the front and rear parts one more marker-notch apart, assuming I have enough fore-and-aft clearance around the front sprocket to do so.  Like you, I hear no noise, or very little. Wiggling the front end, I'd like a bit more play there. This may be just fussing though, enforced winter idleness.

Danneaux

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Re: thorn chainguards
« Reply #11 on: November 27, 2014, 07:08:05 PM »
Quote
Anyone have a preference re bashguards?
Hi Ian!

In the past, I made my own bashguards out of aluminum plate (complicated!) or (much easier!) by milling the teeth off a chainring 6T larger than the one I wanted to cover, then mounting using longer chainring spacers, bolts, and sleeve nuts (pegs). Now they're widely available for purchase (easiest of all!), but you still have to come up with the specifics for mounting.

[Same setup works for quad chainrings -- I managed five, once, back in the day -- provided you're willing to modify the front derailleur parallelogram and build up the shift lever's cable windup barrel so it'll span the gap and shift the range. The resulting bad chainlines limited the usable combinations and made it not worth the trouble. 'Turned out if you wanted really low gears, it was better to repurpose chainrings as freewheel cogs and mill a new cage for the rear mech, then combine that with a small chainring made from a cog. I found an 11 gear-inch low was about my limit before spin-out on 24% grades.]

I used a BBG (Bicycle Bash Guard) on Sherpa, pictured here: http://www.thorncycles.co.uk/forums/index.php?action=dlattach;topic=3896.0;attach=1036;image
Available here: http://www.bbgbashguard.com/Mountainbike.html
Fitting details here: http://www.thorncycles.co.uk/forums/index.php?topic=3821.msg16591#msg16591
Sherpa's was fitted primarily to protect *me*...the wounds caused by an "open" large ramped chainring can be brutal. For those with a strong stomach, see: https://www.google.com/search?q=chainring+injury&biw=1280&bih=713&source=lnms&tbm=isch&sa=X&ei=s2V3VLuKFsblau7zgqgO&ved=0CAcQ_AUoAg

For Seymour the Nomad, I've been very pleased with Thorn's offerings. Versions are available for 5-arm and 4-arm cranks and different BCDs and sized for a range of 'ring diameters.

The bash guard fitted to the Nomad was primarily to prevent chain oil transferring to my calf. Nothing removes chain oil deposits from cycle-tourists' legs better than the interior of a nice down sleeping bag or silk liner! Best to prevent them happening in the first place.

Thorn's 4-arm bash guard shown installed here: http://www.thorncycles.co.uk/forums/index.php?action=dlattach;topic=4523.0;attach=4421;image
Available here: http://www.sjscycles.co.uk/find.asp?site=&name=thorn&page=1&geoc=US#filterkey=cat&cat=504&page=1

Please be aware, fitting a bash guard to a derailleur drivetrain's triple chainset will require spacers and longer chainring bolts/pegs, as detailed in the third link above. If fitted to a Rohloff-equipped bike, the bash guard can be spaced outside a chainring mounted in the outer position on the crank spider, or the chainring may be moved to the inner position and the bash guard fitted like an outer chainring with longer bolts and sleeve nuts after adjusting the chainline (what I did).

Please note: I would fit a Hebie Chainglider, but they are not currently made to accommodate my 36x17 gearing, which I prefer.

Best,

Dan. (...who is usually "on guard" against mishaps)
« Last Edit: November 27, 2014, 10:25:24 PM by Danneaux »

Andre Jute

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Re: thorn chainguards
« Reply #12 on: November 27, 2014, 10:46:24 PM »
I'm going to try fitting the 'glider a fraction looser next spring -- mating the front and rear parts one more marker-notch apart, assuming I have enough fore-and-aft clearance around the front sprocket to do so.  .... Wiggling the front end, I'd like a bit more play there. This may be just fussing though, enforced winter idleness.

My granny used to say, "Idle hands are the devil's ear cushion." Don't ask me; I just report the facts accurately.

But in this case, perhaps not so idle. If a Chainglider is fitted so tightly that there is no movement, I definitely think it is too tight. I have a moment of pause for thought here, because you say it isn't noisy. In my experience, a correctly fitted Chainglider can be easily selected because it is the least noisy fitment, but mine is so silent at all points of adjustment that it is a very subtle judgement. I think there should be between 3mm and 6mm of movement. But the adjustment is pretty crude, so that depending on your chain length adjustment (EBB, sliders, whatever), you could end up with 2-7mm of play and that will be still be good. I tried the Chainglider loose enough to show more than half an inch of movement, and that was definitely audible, more as banging and wind noise than as rubbing though.

I wasn't happy with Chainglider adjusted down to about 1mm and less of movement, ie tight. It was almost imperceptibly noisier, possibly (I'm tempted to say probably) a fraction draggier, just didn't feel right in the ride.

There is so much anecdotal evidence now about clean insides on Chaingliders with 3K+ of use, I'm starting to wonder what magic plastic the thing is made from. And whether it actually "glides" on the chain, or on some thin layer of air.
« Last Edit: November 28, 2014, 06:12:28 AM by Andre Jute »

mickeg

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Re: thorn chainguards
« Reply #13 on: November 28, 2014, 12:49:34 AM »
Anyone have a preference re bashguards?

Yes.  I did something similar to Dan, I bought a cheap 52T chainring on sale.  Cut the teeth off of it with a saber saw.  It ruined the saw blade, the Aluminum clogged up the teeth on the blade.  Then I installed it in the outer position on my double crankarms, I use the inner position for my 44t chainring.  I used a file to file off the cut marks, held the file against the chainring while I turned the pedal by hand.  See photo.

Since I have a Rohloff, I only need one chainring.  Around home I only have one chainring on the bike, but if I take the bike on a tour I expect to have two chainrings on the bike so I can add or subract a few chain links to switch to the other chainring if I need higher or lower gearing, for that I would not bother with a bashguard.

Danneaux

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Re: thorn chainguards
« Reply #14 on: November 28, 2014, 03:23:17 AM »
Quote
It ruined the saw blade, the Aluminum clogged up the teeth on the blade.
Careful selection of tooth count, a slow cutting speed and slow feed speed with kneaded beeswax as a cutting lubricant rubbed into the teeth helps tremendously to prevent blade clogging.

Alternatively, the teeth can be nipped off with an end-cutter or chop-saw, then smoothed down against a grinder before edge-milling.

Yours looks really nice, Mickeg!

Best,

Dan.
« Last Edit: November 28, 2014, 04:09:38 AM by Danneaux »