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rear wiper blade - not fully engaged
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ragnarhairybreeks
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PostPosted: Mon Apr 25, 2016 9:24 pm    Post subject: Re: rear wiper blade - not fully engaged Reply with quote

dsdunbar wrote:
Alistair,
Clever. So you modified the spring, not necessarily the number of coils, but reduced the length of the attachment point of the spring, (thus changing distance X in the equation f=kX).

I didn't take my wiper apart, but thought I looked at the spring and couldn't find enough length to modify at the end, but I'll take a second look.

Thanks for all the suggestions.


I noticed I had made a typo in my previous message. I meant to say I shortened the c clip by a couple of millimetres , not the spring. Sorry about that.

Yes, pretty well it. I wasn't completely convinced that bending the arm really applied that much more pressure on the blade. Maybe it does, but it didn't do it for me.

I guess you could say that squishing the c clip a bit added more preload to the spring. But then again the spring I think has a constant rate and it is preloaded when you attach it to the c clip.

So what difference would shortening the effective length make? It's one of those things that might not make sense when talking about it but for what ever reason it worked.

Alistair
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bluebus86
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PostPosted: Mon Apr 25, 2016 8:53 pm    Post subject: Re: rear wiper blade - not fully engaged Reply with quote

chase4food wrote:
bluebus86 wrote:
chase4food wrote:
Sir Bentley is always right, at least when it comes to direction wise. Bending the arm will increase the spring force F = xC where x is displacement, and C is spring constant. What is C is the key.

Risking prematurely wearing out my binary brain, I went and make some measurements. The scale wanting to do peak hold makes it more challenging, but I succeeded.

Lifting the blade just a bit but make sure no point of the blade make contact with the glass = 25 oz

Lifting the blade an inch higher = 26 oz

A whopping 4% increase if you willing to bend that much.


14.8 to 25 oz force on the rear blade is not too bad. after all you did at first report 14.8 oz for it.

no study of the over action design was required.

I am glad you came around and tried it rather than study the design. see it pays off to not ignore me.


I only read your posts here because you will try to poke any holes you can find. The last set of measurement is to just to prove a point and I use the front wiper for expedience. The rear wiper is inaccessible unless I open the garage. A good technician know what make and not make a difference when it comes to designing an experiment. Please don't overthink this if your eyes begin to glaze over...

Let me repeat. The baseline vs additional 1" lift force difference is conducted on the right front wiper. It gives only 4% increase in spring force.

I promise to return you back to my ignore list.


Well I dont really need to be not ignored by a person that twice calls me a racist. Anyone that plays that card is free to ignore me.

As far as the one inch of lift, a good technician would not be measuring the force on a completley different arm and publish that result when all it would take to get more applicable data would be to open a door to gain access to the closer matching thing to measure. much as a good person would not accuse a person of racism twice. that is a damn nasty thing to do.

the force reading wont help fix the arm. talk about the mud.

I wonder why Bentley recommends that same fix I do, to bend the arm? Must be at least one damn good technician at Bentley I suppose.
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dsdunbar
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PostPosted: Mon Apr 25, 2016 8:49 pm    Post subject: Re: rear wiper blade - not fully engaged Reply with quote

Alistair,
Clever. So you modified the spring, not necessarily the number of coils, but reduced the length of the attachment point of the spring, (thus changing distance X in the equation f=kX).

I didn't take my wiper apart, but thought I looked at the spring and couldn't find enough length to modify at the end, but I'll take a second look.

Thanks for all the suggestions.
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chase4food
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PostPosted: Mon Apr 25, 2016 7:45 pm    Post subject: Re: rear wiper blade - not fully engaged Reply with quote

Very appropriate term - signal to noise ratio of a thread denotes the usefulness and the readers' varied ability to extract the useful signals out of the mud floor. Laughing
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ragnarhairybreeks
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PostPosted: Mon Apr 25, 2016 7:28 pm    Post subject: Re: rear wiper blade - not fully engaged Reply with quote

Edit I have a typo in my message. What I meant to say is that I shortened the c clip, not the spring



I was hesitant to post to their thread, the signal to noise ratio seems awry Smile

But for what it's worth here is my experience with fixing one of my front wipers.

Over the last few years I have been using beam type ( Michelin and Bosch brands) wipers up front. The passenger side wiper never made good contact in the middle of the wiping area with either brand.

Oh I bent the arms, cleaned the glass and wiper blades. More than you can imagine. But I'd still get a small un wiped patch with the passenger wiper.

But what fixed the issue was taking the spring out of the arm, and then the "C" shaped wire bail that connects the spring to the hub of the arm. I compressed that spring about 2-3 mm ( sorry I can't be precise, I'm writing from memory).

It's a little bit of a pain to get the spring and bail out from the arm, but it's not that difficult. To be clear, I closed the c shaped bail just a little (in the vise).

That little amount translated to enough additional down pressure that it solved my problem.

So for what it's worth, there's another suggestion.

Cheers

Alistair
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Last edited by ragnarhairybreeks on Mon Apr 25, 2016 9:26 pm; edited 1 time in total
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PostPosted: Mon Apr 25, 2016 6:39 pm    Post subject: Re: rear wiper blade - not fully engaged Reply with quote

OP, you might also consider trying a wiper blade that is a "beam style" type. So instead of the traditional blade with individual points of pressure, this type of blade uses a wider spring over the entire length of the blade. One that looks like this:

http://www.amazon.com/Anco--22-M-Profile-Wiper-Bla...beam+style

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chase4food
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PostPosted: Mon Apr 25, 2016 2:35 pm    Post subject: Re: rear wiper blade - not fully engaged Reply with quote

bluebus86 wrote:
chase4food wrote:
Sir Bentley is always right, at least when it comes to direction wise. Bending the arm will increase the spring force F = xC where x is displacement, and C is spring constant. What is C is the key.

Risking prematurely wearing out my binary brain, I went and make some measurements. The scale wanting to do peak hold makes it more challenging, but I succeeded.

Lifting the blade just a bit but make sure no point of the blade make contact with the glass = 25 oz

Lifting the blade an inch higher = 26 oz

A whopping 4% increase if you willing to bend that much.


14.8 to 25 oz force on the rear blade is not too bad. after all you did at first report 14.8 oz for it.

no study of the over action design was required.

I am glad you came around and tried it rather than study the design. see it pays off to not ignore me.


I only read your posts here because you will try to poke any holes you can find. The last set of measurement is to just to prove a point and I use the front wiper for expedience. The rear wiper is inaccessible unless I open the garage. A good technician know what make and not make a difference when it comes to designing an experiment. Please don't overthink this if your eyes begin to glaze over...

Let me repeat. The baseline vs additional 1" lift force difference is conducted on the right front wiper. It gives only 4% increase in spring force.

I promise to return you back to my ignore list.
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PostPosted: Mon Apr 25, 2016 2:28 pm    Post subject: Re: rear wiper blade - not fully engaged Reply with quote

chase4food wrote:
Sir Bentley is always right, at least when it comes to direction wise. Bending the arm will increase the spring force F = xC where x is displacement, and C is spring constant. What is C is the key.

Risking prematurely wearing out my binary brain, I went and make some measurements. The scale wanting to do peak hold makes it more challenging, but I succeeded.

Lifting the blade just a bit but make sure no point of the blade make contact with the glass = 25 oz

Lifting the blade an inch higher = 26 oz

A whopping 4% increase if you willing to bend that much.


14.8 to 25 oz force on the rear blade is not too bad. after all you did at first report 14.8 oz for it.

no study of the over action design was required.

I am glad you came around and tried it rather than study the design. see it pays off to not ignore me.
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PostPosted: Mon Apr 25, 2016 2:24 pm    Post subject: Re: rear wiper blade - not fully engaged Reply with quote

The posted excerpt from the Bentley is correcting the till (or perpendicularity) of the blade squeegee, not to increase the downward force and mentioned numerous times in this thread. The perpendicularity is very important.
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bluebus86
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PostPosted: Mon Apr 25, 2016 2:24 pm    Post subject: Re: rear wiper blade - not fully engaged Reply with quote

DwarfVader wrote:
bluebus86 wrote:
...study of irrelevent stuff is a waste.


One often finds what is irrelevant today is important tomorrow.

not learning something because one finds it irrelevant is only doing ones self injustice.


*edit:* more on topic... I think the OP should try bending it, as stated he already bought new blades and that didn't have the desired result. If bending it doesn't work, replace the arm and spring with new digs.


not attempting the obvious fix and instead measuring the spring force on other cars is a waste of time, not all knowlegde is useful, specaily at the expense of learning something that is useful.
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PostPosted: Mon Apr 25, 2016 2:22 pm    Post subject: Re: rear wiper blade - not fully engaged Reply with quote

dsdunbar wrote:
My concern with bending the wiper arm is not knowing how brittle the material might be.  


It's pretty stout.  Bend it in small increments; a small bend can make a big difference.

chase4food wrote:
What happen to the aerodynamic spoiler on your arm?


It's on the front left wiper arm, where it's always been. Popcorn
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PostPosted: Mon Apr 25, 2016 2:21 pm    Post subject: Re: rear wiper blade - not fully engaged Reply with quote

dsdunbar wrote:
Thanks all for the insight. I am appreciative of the very technical and the more "try this" approach. My concern with bending the wiper arm is not knowing how brittle the material might be.

I didn't even consider to check the Bentley.

Thanks.


the arm is not brittle, probably could bend it into a pretzel.
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PostPosted: Mon Apr 25, 2016 2:17 pm    Post subject: Re: rear wiper blade - not fully engaged Reply with quote

Sir Bentley is always right, at least when it comes to direction wise. Bending the arm will increase the spring force F = xC where x is displacement, and C is spring constant. What is C is the key.

Risking prematurely wearing out my binary brain, I went and make some measurements. The scale wanting to do peak hold makes it more challenging, but I succeeded.

Lifting the blade just a bit but make sure no point of the blade make contact with the glass = 25 oz

Lifting the blade an inch higher = 26 oz

A whopping 4% increase if you willing to bend that much.
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PostPosted: Mon Apr 25, 2016 2:07 pm    Post subject: Re: rear wiper blade - not fully engaged Reply with quote

Thanks all for the insight. I am appreciative of the very technical and the more "try this" approach. My concern with bending the wiper arm is not knowing how brittle the material might be.

I didn't even consider to check the Bentley.

Thanks.
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PostPosted: Mon Apr 25, 2016 2:05 pm    Post subject: Re: rear wiper blade - not fully engaged Reply with quote

Image may have been reduced in size. Click image to view fullscreen.
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PostPosted: Mon Apr 25, 2016 1:54 pm    Post subject: Re: rear wiper blade - not fully engaged Reply with quote

Even Sir Bentley tells you to bend the arms if you're having contact issues.

For the record, here's my '90's rear wiper arm and it makes 100% blade contact:

Image may have been reduced in size. Click image to view fullscreen.

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PostPosted: Mon Apr 25, 2016 1:27 pm    Post subject: Re: rear wiper blade - not fully engaged Reply with quote

I have no idea how much attention the OP paid to the wiper blade designs. Most European auto utilize the traditional blade design similar to that in the illustration here:

Image may have been reduced in size. Click image to view fullscreen.


I am the first to admit when I first encounter wiper blade problem, it took a bit of careful study to realize how it all work. On this design only one end of the blade is held fixed - the side that has a locking barb (left hand side end). The rest of the blade floats in the remaining five fingers of the metal frame. There are two SS spines (only one shown here) that supports the rubber squeegee blade. It help support the span of the squeegee between the fingers to spread the force evenly. In some cheap blade a plastic stripe is used that eliminates the two SS spines altogether. These are shit blades to avoid.

Even with the typical ones you can buy like in the illustration above, some are worst than others. I always prefer to keep the factory frame unless they are worn or damaged.

While you can bend the arm to gain a bit of spring force, you have to bend it a lot to make a material difference, and it will be very unsightly. The right solution is to get to the bottom true cause(s) of the problem.
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PostPosted: Mon Apr 25, 2016 1:06 pm    Post subject: Re: rear wiper blade - not fully engaged Reply with quote

bluebus86 wrote:
...study of irrelevent stuff is a waste.


One often finds what is irrelevant today is important tomorrow.

not learning something because one finds it irrelevant is only doing ones self injustice.


*edit:* more on topic... I think the OP should try bending it, as stated he already bought new blades and that didn't have the desired result. If bending it doesn't work, replace the arm and spring with new digs.
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PostPosted: Mon Apr 25, 2016 12:59 pm    Post subject: Re: rear wiper blade - not fully engaged Reply with quote

chase4food wrote:
Right! No need to work your brain too hard is definitely a word of wisdom. Shocked


back to not ignoring me again, good for you, welcome back!

the original poster can simply try bending the arm. It helps to "study" the right thing, study of irrelevent stuff is a waste. Study what happens when the arm is bent rather than study the fish scale tension on a MiniCooper blade. It takes wisdom to determine what is, and what is not useful to "study" to fix the problem.
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PostPosted: Mon Apr 25, 2016 12:40 pm    Post subject: Re: rear wiper blade - not fully engaged Reply with quote

Right! No need to work your brain too hard is definitely a word of wisdom. Shocked
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