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Modifying Sierra Wiper Mechanism


Sparepart

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At last I have the windscreen fitted on the Exmo, and have just managed to mount the Sierra wiper mechanism which I have modified as per the build video. I have made shorted arms and blades, so far so good. I put it all together and set the motor going. No bangs or crashes, so the clearences are okay. However, it's obvious that the sweep is not good enough. On the driver's side it is just about 90 degrees, i.e just 45 degrees each side of vertical, this might just be ok to see through on a wet day, but then the park position leaves the wiper well up the screen. I have searched through the forums and unsurprisingly this topic has already come up before. I quote the ones that I found below. It seems that the perceived wisdom is to add 10mm to the short arm that is attached to the motor spindle. Before I do this i am wondering if anyone has anything further to add to the wisdom on this subject, apart from telling me to fit Mini/old BMC type wiper mechanism.

https://www.rhocar.org/index.php?/forums/topic/4337-sierra-wiper-motor/&tab=comments#comment-31292

https://www.rhocar.org/index.php?/forums/topic/5338-sva-with-windscreen/&tab=comments#comment-40054

 

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I dismantled the wiper mechanism from under the scuttle and set about making the mod. There is a major problem. The arm that is to be lengthened already comes very close to the "backplate" to which everything is bolted, i.e. the linkages and the motor/gearbox etc. G. Cash gave me a spare wiper assembly, but this is the same, the arm comes close to the backplate. Obviously, I am missing something here ( yes I know, use Mini wipers etc.) ... as I see it the only way to extend the arm is to move the drive shaft by re-mounting the motor and gearbox further away from the potential contact point. I can see that this is possible, but no one has mentioned this. Its all puzzling.

Wiper-crank-clearance.jpg.9f561cbbcec5c5dd9afff3eb2473e14a.jpg

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I dont know the Sierra wiper system. Is the aim to increase the sweep of the wiper blades?

Can you shorten the slave operating arms that move the spindle at the outer ends? Or just drill extra holes nearer the wiper spindle, and mount the operating (ball?) joint there instead.

That will have the same affect as lengthening the arrowed arm.

Edited by Bob Tucker
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Just been scrutinising some images of the Sierra mechanism (using 2 pairs of glasses...4x !)

There maybe no need to modify the arms. Moving the pivot where the motorised arm joins the slave arm nearer to the wiper spindle may do the trick, just one hole to drill. I just wish I could draw pics like Longboarder. 😃

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Have you considered replacing the whole thing with the setup GBS (and CBS) sell (Lucas?) ?

Not sure if it's possible on your car and costs about £150 but has the wire that just runs backwards and forwards through the gearboxes - works really well. 

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I upgraded my wiper mechanism to the Lucas one as so much easier (as nelmo suggested). I managed to pick up a 2nd hand setup for about £50, they were fitted into loads of cars Mini,MG and many other classics and the good thing is you can change the sweep by replacing the gear on the motor. I think i went for a 110 degree sweep

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I knew someone would advise using the Mini/BMC type mechanism, it's just so obvious, the problem is with my attitude not to let the bone go, it's a case of "I've started so I'll finish syndrome" ISSIF.  I have now extended the arm by 10mm and remounted the motor. The added sweep is not great but welcome. As Bob says I can see that if the slave arms are shortened then this gives a better "bang for the buck", also this has the advantage of choosing a different sweep for each wiper AND only one cut and weld on each arm AND the effect can be trialled by temporarily overlapping the cut arm to set the added sweep to exactly that needed. Thanks for the suggestion, I'll keep you posted.

  • Haha 1
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On Florin we fitted the 2speed mini set --- ( kept quite 'til now )  this removes the hazard of mechanical scissor action which could interfere ( one day ) with behind dash wiring. The biggest gain is a large space for a glove box, which in our case is a Henry Hoover dust bag fitted to the rear of the g/b door.

No Help if you're ploughing on with the ford unit which is more efficient in action. 

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  • 2 weeks later...

After a lot of trial and error ( I think it's called an heuristic approach) I have modified the Sierra wiper mechanism to give a better sweep of the blades, the drivers side now has just over 130 degrees and the passenger side (which was never a problem) has around 100 degrees. The photo below shows the hacked end product. Adding length to the crank arm only gives a marginal gain in sweep because it soon fouls the bracket and also means changing the length of the attached arm to a point where the mechanism becomes "unstable" and can easily lock up as the joint flexes in the wrong direction from the nearly straight position, a bit like your knee suddenly bending the wrong way when you try to kneel. Now I can move on and try to get a decent weather seal around the turning shafts that are coming through the scuttle.

Wiper-Sweep-Mods.thumb.jpg.c5983f0f78bfbff2b1e40f2af94618d1.jpg

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