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Belt twisted twice

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Belt twisted twice

Postby stridahd on Wed May 09, 2012 3:56 pm

Hello,

After approx. 2 years and 3.000 km the belt of my Strida suddenly twisted and got torn:

Image

At the first glance it appeared that the belt was worn, so I ordered and mounted a new one. However after a few days the force for pedalling suddenly became a bit stronger for two or three brief moments and then the new belt twisted again before I could stop (due to traffic):

Image

Therefore the belt cannot be the origin for this rather odd problem and as there is no Strida-shop within the next 100 km I'd like to ask for your advice.

Another issue with my Strida, is kind of a vaque cracking sound ("knacksen" in German) when pedalling uphill with strong force. This sound has been around for a while and it appears to be related to the pedals as it was almost gone after adding some lube.

all the best,

Strida@HD

PS: I just registered an/this account.
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Re: Belt twisted twice

Postby Blackstridaaustria on Wed May 09, 2012 4:13 pm

Image stridahd!

That' s weird, no idea how comes that!

I've transferred your post to the Hong Kong Strida forum, hopefully the Asian experts are able to help.

stridahd wrote:Another issue with my Strida, is kind of a vaque cracking sound ("knacksen" in German) when pedalling uphill with strong force.


Maybe the answer is here:

http://www.stridaforum.com/forum/viewtopic.php?f=4&t=2317&start=0&st=0&sk=t&sd=a
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Re: Belt twisted twice

Postby one_half_3544 on Wed May 09, 2012 9:50 pm

stridahd wrote:After approx. 2 years and 3.000 km the belt of my Strida suddenly twisted and got torn:

At the first glance it appeared that the belt was worn, so I ordered and mounted a new one. However after a few days the force for pedalling suddenly became a bit stronger for two or three brief moments and then the new belt twisted again before I could stop (due to traffic):


Could you check snubber bearing? Does it rotate freely?
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Re: Belt twisted twice

Postby StridaD on Thu May 10, 2012 11:03 am

Just guessing ... Misalignment between front and rear sprockets causing belt to slip into a gap and get stuck?
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Re: Belt twisted twice

Postby Genuine_S on Thu May 10, 2012 3:20 pm

As for Belt twisted issue, I have not seen issue like that. But one thing I would like you to check is if freewheel is properly "free" or not. If freewheel sometime does not work well, the belt will have unbalanced tention between top and bottom, although this is just my assumption.

I have had a kind of cracking sound issue in the past after riding my Strida under rain few times. My recommendation for this issue is to loosen screws from where the sound is produced, and tighten with proper torque, on top of rubing proper position(s). Using torque wrench is best.
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Re: Belt twisted twice

Postby Blackstridaaustria on Thu May 10, 2012 5:07 pm

That fault could happen only because the belt tension was too low, I believe.
Could you try to mount the belt again, but with a little more tension as before?

Seems that the Hong Kong Strida fans also have never seen that, there was no problem solution posted.
Now I've posted above at Thailand Strida forum, will see...
If the friendly fans there also have no idea, we should ask Ming cycles directly I mean.
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Re: Belt twisted twice

Postby TomT on Fri May 11, 2012 9:10 am

Agrees - low belt tension.
But also check for alignment, pulley flange damage / bent ?
Loose rear joint (bolt from RHS / nylon washer between bottom tube and rear 'part' ? .. causing poor rear pulley alignment (but I'm sure you notice this amount of 'looseness').
Problem with Front bottom bracket bearing - loose ?
F pulley not aligned on crank
F Pulley cracked or warped in heat ???

Now I'm stuggling to guess any more :lol:
good luck and please let us know what is the cause of this very weird happening.
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Re: Belt twisted twice

Postby Blackstridaaustria on Fri May 11, 2012 4:03 pm

Posted at Thailand Strida Club:
hisoft wrote:So sorry but I can't imagine how it occur without human being. :shock:

I think you found it first time. Put screwdriver between belt and chainring teeth and moving the crank arm. Then the belt put out from crank. Twist it back and reverse the step to put the belt back.

If it happen again then... :? Come back and I will try to find another solution.


The Hong Kong Strida fans also have no explanation, it seems...

Maybe you are the first with that problem - any news?
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Re: Belt twisted twice

Postby one_half_3544 on Fri May 11, 2012 8:43 pm

Blackstridaaustria wrote:Maybe you are the first with that problem


Definitely not. Same problem is described (automatic translation):

Image
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Re: Belt twisted twice

Postby Blackstridaaustria on Fri May 11, 2012 9:58 pm

Due to the automatic translation it is hard to understand fully, but the last comment seems interesting:

thonik wrote:The problem was found easily, is necessary to adjust the belt tension by turning the carriage around their offset axis.
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Re: Belt twisted twice

Postby one_half_3544 on Mon May 14, 2012 12:13 pm

Blackstridaaustria wrote:Due to the automatic translation it is hard to understand fully, but the last comment seems interesting:

thonik wrote:The problem was found easily, is necessary to adjust the belt tension by turning the carriage around their offset axis.


Yes, he writes that the problem should be solved by tensioning the belt, but that he was unable to do it due to excessive amount of dirt near the bottom bracket.
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Re: Belt twisted twice

Postby Blackstridaaustria on Mon May 14, 2012 1:08 pm

I would understand if the big groove nut was tightened too hard.
But too much dirt?
Or does that mean he had overlooked the Allen bolt at the bottom?

Sorry for asking again, but I think this problem is very interesting, I do not want to experience that on my bikes.
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Re: Belt twisted twice

Postby one_half_3544 on Tue May 15, 2012 8:57 am

Blackstridaaustria wrote:I would understand if the big groove nut was tightened too hard.
But too much dirt?
Or does that mean he had overlooked the Allen bolt at the bottom?

Or he could have overlooked the big groove nut =). It is not clear from his post.

Sorry for asking again, but I think this problem is very interesting, I do not want to experience that on my bikes.


In any case you should either have strida bag with you (to be prepared to use public transport) or have a spare belt plus tools to replace it. Here is a report of sudden snapping of the belt (again automatic translation):
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Re: Belt twisted twice

Postby Bietrume on Tue May 15, 2012 12:28 pm

Here is what I found on another forum (http://www.lawnmowerforum.com/troy-bilt-forum/5880-twisted-drive-belt-troy-bilt-bronco.html)
If a pulley is bent or out of round, the belt has a broken cord in it or is in any way damaged, If the pulleys are out of alignment or a bearing is rough.... the belt will start bouncing in the open spans between the pulleys, when they bounce at the proper rate they can actually grab better on one side of the pulley... that is what causes them to flip or twist...
The point that starts the twist can easily be damaged and may continue to twist, even after the original problem is corrected..


On the Strida, the front pulley is not foreseen with full flanges, certainly not on the inside. So, if the belt is too lose and there is a slight misalignment between the pulleys, the belt could start bouncing, move sideways on the front pulley where there is no flenge and then get grabbed by one of the flenge portions and finally twist.
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Re: Belt twisted twice

Postby Blackstridaaustria on Tue May 15, 2012 8:02 pm

one_half_3544 wrote:In any case you should either have strida bag with you (to be prepared to use public transport) or have a spare belt plus tools to replace it.


I think instead of the Strida bag and/or tools+belt I will choose an additional 20 Euro note in my purse for a taxi. :)
Hopefully the snapping belt is a rarity...

Bietrume's explanation and the mowerforum post are meeting the point most exactly, I think.
Just the last phrase of the post I don't understand:
"The point that starts the twist can easily be damaged and may continue to twist, even after the original problem is corrected.."


From HK Strida Club:

fatman wrote:I think it is because the snubber is too far from the freewheel, normally the belt should not able to reverse.


BSA wrote:Thank you!

You're right for sure, but what circumstance could be the initial cause for the belt to turn around?

The snubber itself could not twist the belt, I believe.
I think there must be an additional component.
The last comment of the Russian post said: "The problem was found easily, is necessary to adjust the belt tension by turning the carriage around their offset axis."
I do also believe that something like that could happen only, because (first) the belt tension was too low.

What do you think about that?


fatman wrote:Yes, when the belt tension is too low and without the snubber hold it, it will very easy to bounce. So it may be twist if the belt bounce to the edge of the freewheel that cause the belt cannot "landing" to freewheel in horizontal position.


BSA wrote:The belt "climbs" up the edge of the freewheel, due to low tension, then it "lands" half turned, and the next step would be a full turn.
And the snubber bearing could not prevent that because it was too far away from the belt.
We think in equal direction, if I understood correct, thanks again for the affirmation.

Hopefully the German Strida fan will come back to the forum soon, I'm very curious what he could find out.
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