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Sideway movement of the rear wheel

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Re: Sideway movement of the rear wheel

Postby Blackstridaaustria on Mon Jun 03, 2013 5:14 pm

It's a bit tricky to measure the inside diameters exactly with a usual sliding caliper, I mean.
So, I'd say the bolt side is minimally oval (~ 0,05 mm).
Image

The axle side is definitely oval, in the same direction (red arrow) like yours for ~ 0,1 mm.
Image

I'm sure the plastic part is in fact sliding in the tube, it was hard to pull out, yes, but the high forces inside of the joint will be able to move the plastic part easily - the "levers" (seat and bottom tube) are 75 cm, respectively 90 cm long!
Btw, didn't measure the inside diameter of the plastic part, it's looking as good as new:
Image

Image

I was also thinking of to put something below the cup spring, but a matching washer, or shim, has to be strong (and of a certain thickness).
Doing that will increase the force of the cup spring, don't you think so?
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Re: Sideway movement of the rear wheel

Postby Bietrume on Mon Jun 03, 2013 8:50 pm

So you have similar holes and axle dimensions as on mine!

I see that your bottom tube is as damaged by the cup spring as on my Strida :(

Blackstridaaustria wrote:I was also thinking of to put something below the cup spring, but a matching washer, or shim, has to be strong (and of a certain thickness).
Doing that will increase the force of the cup spring, don't you think so?

I was thinking to a washer of 0.5mm thick, made out of spring steel. These parts are used as valve shims in shock absorbers and are quite hard (harder than aluminium anyway). The shim being not coated, I will paint it.
As the bolt 373 is tightened to torque, the force should not be higher than without washer, the bolt will only extend with 0.5mm more to the outside.
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Re: Sideway movement of the rear wheel

Postby Blackstridaaustria on Mon Jun 03, 2013 8:54 pm

Bietrume wrote:As the bolt 373 is tightened to torque,


Oh, f..., yes, I didn't recognize the torque, thank you :oops:
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Re: Sideway movement of the rear wheel

Postby Bietrume on Tue Sep 17, 2013 9:55 am

Hi BSA,

I was actually wrong in my statement about the torque :oops: . And you were right when you wrote that adding a washer would increase the spring preload. The sketch below shows that bolt 373 is actually torqued against axle 340 end. So the cupped spring preload is purely dependant on distance X (spring built-in length).
Image

I think I now have an explanation for the angular movement of the wheel on my bike: the sharp edges of cupped spring 367 eat the surface of the bottom tube and of washer 364 away (as can be seen here), which increases the cupped spring built-in length. These springs are very stiff, which means that a small variation of their built-in length greatly affects their preload.

I have not checked the dimensions of the cupped spring 367, buit I think they are close to these ones: inner diameter: 12.2mm, outer diameter: 28 mm, thickness: 1.25mm, total height: 2.1mm

In a catalogue (http://www.bellevillesprings.com/disc-springs-din-2093.html) you find out that when you compress such a spring by 0.64mm, you achieve a force of 2083 N. If you now compress it by only 0.38mm, the force drops to 1395 N.

So, the wear/deformation that can be stated on both bottom tube and washer 364 will make the preload of the cupped spring drop sensibly.

Looking now to the exploded view of the Strida in the manual, you can see a washer 363 between cupped spring 367 and the bottom tube. According to me, this is a flat washer that prevents the wear of the tube and also increases the preload of the spring. I wonder why they have removed it.

I get mad when I see that such cheap parts and poor design can affect the functioning of this otherwise nice bike. :evil: :evil: :evil:

This poor design has following consequences:
- Irreversible damage of the aluminium bottom tube.
- Clicking noise
- Angular movement of the rear axle + wheel : this can trigger the belt to jump on the flanges of the freewheel and definitively damage the belt.
- Bad guidance of the rear wheel: it accelerates the wear of the rear tire and causes bike instability.

I sincerely hope that these problems have been solved on the EVO3, as its high price should go together with a high quality level.
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Re: Sideway movement of the rear wheel

Postby Blackstridaaustria on Tue Sep 17, 2013 7:52 pm

Dear Bietrume,

thank you so much for research, explanation and the excellent drawing!

Image

Your conclusions are indeed coherent and comprehensible and they also explain the different part numbers of the exploded drawing.
(I was totally wrong to think that there could be two cup springs in that place - as stated erroneously in the post here)

This is anyway a highly important discovery - which should be definitely reported to Ming - and it should be investigated why the washer is missing.

For the cup spring:
Recently we've reordered a few springs, therefore it was easy to measure the real dimensions of 5 unused original springs;
inner diameter 12,3 mm, outer diameter 23 mm, thickness 1,7 mm, total height 2,9 mm
So - due to more thickness - the force of the original cup springs might be much higher than the amounts of the example from the catalogue...
(Interesting detail at the "Group2; 1,25 up to..." - radiused edges - aha!!)

According to Bill there are only two "washers" below the rear wheel bolt of the EVO...
Last week arrived finally a few EVOs Vienna, I'll check their rear bolts asap.

Anyway we should tell Ming our opinion about the cup spring!
Honestly, I don't have much hope, but maybe Ming cycle has learned meanwhile to respect and follow the advice of experienced customers.

I want to beg here also for assistance of technically versed Strida users and dealers!
Ask the Ming cycle technical support about the frame damage, clicking noises, movement of the rear wheel and the missing washer 363 of your Strida.

contact@strida.com

Please report here in the forum if your Strida does have the big washer 363,
I would really like to know if the washer was mounted on older versions...Image
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Re: Sideway movement of the rear wheel

Postby Bietrume on Wed Sep 18, 2013 6:58 am

Hi BSA,

I'm glad you agree with my findings. :D

So the cupped spring of the Strida does not have standard dimensions, this is really strange. It is maybe made according to Chinese standards :?:

Coming back to the contact surfaces of the cupped spring, here is what you can find on the same website as the one of the catalogue:

....it is also necessary to pay some attention to the nature of the guidance and seating surfaces.
Much depends upon the severity of duty in the application, e.g. if the disc is to be used as a means of providing a static clamping force on 'mild steel' or cast/forged steel surfaces, this is probably satisfactory. However, if the seating faces are in aluminium, copper, brass etc; then it is preferable to provide a hardened thrust washer to alleviate face damage/indentation. Dynamic applications, involving large numbers of deflection cycles, will require that in addition to hardened seating faces the guidance surfaces must also be sufficiently hard to prevent excessive wear or 'stepping'...


I wonder also why washer 364 has a stange shape when used. Is it a flat washer when new or is it also a kind of cupped spring? In the first option, it looks like the steel is much too soft for the loads it has to stand...
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Re: Sideway movement of the rear wheel

Postby Blackstridaaustria on Wed Sep 18, 2013 8:59 pm

Hello Bietrume,

"agree" is not the fully correct expression, it was more like an enlightenment...

Unfortunately I'm really busy at the moment - the heating equipment in one half of my apartment is out of order and it's getting cold here Image - therefore just a short interim report:

Bietrume wrote:It is maybe made according to Chinese standards :?:


Should be possible to find out, but will take some time...

For the catalogue citation:
Thanks again, didn't see that!
Hmmm, if we would now simply put hardened steel washers above and below the belleville (cup) spring then would the spring load raise...
...maybe too much for the bolt 373?
What do you think?

Today I could take a quick look at three original brandnew Stridas, EVO, SX and LT:
All of them equipped with the new EU-conform frame, the EVO was taken out from the original box.
Guess what?
NONE of the three was equipped with more than TWO "washers" below the bolt 373 :roll:
(At the weekend it will be time to check two more EVOs and look at the washer 364.)

Btw, could you please tell us your meaning to this post?
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Re: Sideway movement of the rear wheel

Postby Bietrume on Thu Sep 19, 2013 9:01 am

Hmmm, if we would now simply put hardened steel washers above and below the belleville (cup) spring then would the spring load raise...
...maybe too much for the bolt 373?
What do you think?

Yes, that is a solution I was thinking about. If you want to keep the same preload, then you have to put a small washer of the same thickness as all the hardened washers you are adding, between bolt 373 and axle 340. Then the spring built-in length will not change. You just have to make sure that bolt 373 is screwed far enough into axle 340. If it is too short, use a longer one.
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Re: Sideway movement of the rear wheel

Postby Bietrume on Thu Sep 19, 2013 2:16 pm

I now see that my sketch was wrong :evil:

I thought washer 364 was centered on axle 340, but it is actually clamped between nut 373 and axle 340. So if you add a washer under the cup spring you need to add another washer 364 but of the same thickness to keep the same spring preload.

In my case, I want a higher preload, so I will not add an extra washer 364.
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Re: Sideway movement of the rear wheel

Postby Blackstridaaustria on Thu Sep 19, 2013 2:35 pm

Calm down, most of us will not have realized that :D
The drawing is still very good, I was quite unsure about this detail and therefore I wanted to disassemble a few bolts at the weekend.
Seems that we need in sum three washers to reach the target of a fully functional rear joint...

I'm also quite unsure how to proceed with this post because it will belong to several known issues of the rear Strida region. To merge the posts is not that good, I think...maybe pin this post and edit with links to the other posted problems...
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Re: Sideway movement of the rear wheel

Postby Bietrume on Mon Sep 23, 2013 11:50 am

Well the proposed solution is less simple than I thought: the distance 'X' is only 2mm. The cup spring thickness is 1.7mm, so it can only be compressed by another 0.3mm before being completely flat. It is not advised to push a cup spring until it is flat as the stresses in the spring become too high.
Image

Adding a washer under the cup spring is therefore not advised, if the washer is about 2 mm thick (like the stainless steel one I found in a DIY shop), the cup spring will not be centered anymore and bolt 373 will not be screwed against axle 340.
Overtightening the bolt will damage the cup spring.
Adding a third washer between axle 340 and washer 364 is not ideal because it will not center perfectly and the inner edge of cup spring 367 will not be well guided.

On my bike, I replaced the soft steel washer 364 by a stainless steel one, which seems to be a much harder material. The original washer was quite deformed/worn out, and my first impression today is that the rear wheel swing movement has been reduced by almost 50% by bringing the preload of the cup spring almost back to its inital value.
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Re: Sideway movement of the rear wheel

Postby Blackstridaaustria on Mon Sep 23, 2013 8:43 pm

Had no chance to examine more Evos, sorry for the delay :oops:
But I've found a good pic of a 3.0 Strida's rear area- there is an additional washer below the cup spring!

For this pic I'd like to get the permission to use it from florian - are you still here?
Please look at your mailbox...

Bietrume wrote:Adding a third washer between axle 340 and washer 364 is not ideal because it will not center perfectly and the inner edge of cup spring 367 will not be well guided.


Yes, perhaps not ideal...but if the thickness of the third washer is below that of the cup spring and the outer diameter very close to that of the axle it should work, I believe.
The third washer should fit inside of the cupspring; imaginable as some kind of axle elongation - shown in red color below.
(I'm here also thinking about a method for easy retrofit - a longer axle, like mentioned by Xentrax here, would be the better solution, but it would also need much more effort for exchange.)
Hope you don't mind that I've used your image for illustration:

Image
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Re: Sideway movement of the rear wheel

Postby Bietrume on Wed Sep 25, 2013 10:03 am

I agree with your '3 washers' solution. However, for a retrofitting solution, the difficulty will be to find standard stainless steel washers with the proper dimensions (diameters and thickness).
You can of course order custom washers made by laser cutting or etching but it could be quite expensive, especially if you have to buy the raw material in large quantity :?
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Re: Sideway movement of the rear wheel

Postby Blackstridaaustria on Tue Nov 12, 2013 9:37 am

This thread was "pinned" by the admin due to the importance of Bietrume's discovery ten posts above.

Bietrume's explanation does belong to several known Strida issues;

Belt twisted twice

Strida 5.0 "clicking" noise

Broken 373 Bolt

to name a few...



Bietrume wrote:Looking now to the exploded view of the Strida in the manual, you can see a washer 363 between cupped spring 367 and the bottom tube.

Here we have to be careful, several readers will not be able to verify what we are talking about:

Below are detailed screenshots of the exploded 5.0 drawings, this one from the owner manual 2008.pdf, identical to the drawing at this link:
http://www.strida.com/upload/Image/FAQ/exploded%20drawing%20strida%205.pdf
Image

and that one's from the nowadays on CD supplied Strida manual pdf or the link below:
http://www.strida.com/upload/Image/catalogue/STRIDA%20manual-0617%20revised.pdf
Image

Bietrume wrote:I sincerely hope that these problems have been solved on the EVO3, as its high price should go together with a high quality level.


Well, the drawing was "enhanced"... :roll:
(Just amazing that the recessed (!) snubber bolt 386 with its nut (!) 387 was not updated...)

For approval are here a few pics of a brandnew Strida EVO's rear joint parts - exactly like the newer drawing - the cup spring (now 367-3) and the washer 364, there is no third "washer".

Image

Image

Red arrow: Inner edge mark of the cup spring in the brushed aluminium surface of the frame.
Green arrow: Border of the silver paint, obviously was this area masked before the painting process.

Image

The washer 364 is already deformed, outer edge marks of the cup spring are visible (red arrow).

Image

Below, - sorry to use your pics without permission, florian - the rear area of a 3.0 Strida:

Image

There ARE three washers!!

Could any 3.0 Strida owner please supply more info about dimensions and material of the "missing" washer 363?
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Re: Sideway movement of the rear wheel

Postby ImpairedVisions on Tue Mar 11, 2014 4:51 pm

My rear wheel developed some wiggle room last year. I took it out to ride last Saturday, after being stored since December, and the frame broke while riding. I've emailed photos to the admin to have them posted. I think the Strida is unreliable after being ridden for many years.

I purchased my Strida 5.0 in March 2008.
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