Tony Posted August 8, 2006 Report Share Posted August 8, 2006 A prolific design flaw with this model is the attitude of the damper, mechanical engineers this one is for you. As you can see the stresses on the damper over time weaken the shaft to the extent it snaps.. Major, major flaw by design. What is interesting is the type of brake? It appears clean, no sign of fatigue or contamination. The construction is a Torsion cross member with longitudinal dampening, i feel the attitude of the damper is some 20d or so to low. Bad mistake to make in development i feel, and this condition is becoming a daily event by the customer...... Time for a re-call? What do you think? Quote Link to comment Share on other sites More sharing options...
discount tyres dan Posted August 8, 2006 Report Share Posted August 8, 2006 i agree, we keep most rear shocks for renaults in stock, i think the shock angle looks totaly wrong, we have had a customer say that they could push the car along with the handbrake on.. was just the car squatting. thats french for ya Quote Link to comment Share on other sites More sharing options...
Tony Posted August 8, 2006 Author Report Share Posted August 8, 2006 i agree, we keep most rear shocks for renaults in stock, i think the shock angle looks totaly wrong, we have had a customer say that they could push the car along with the handbrake on.. was just the car squatting. thats french for ya Reads like a 'bird in the bush' Quote Link to comment Share on other sites More sharing options...
Roger440 Posted August 9, 2006 Report Share Posted August 9, 2006 Certainly don't look to clever! Out of interest, is the top eye bolt in the same plane as the lower one or 90o to it? Quote Link to comment Share on other sites More sharing options...
Tony Posted August 9, 2006 Author Report Share Posted August 9, 2006 Certainly don't look to clever! Out of interest, is the top eye bolt in the same plane as the lower one or 90o to it? I would say 70o with a damper stroke of 11" total Quote Link to comment Share on other sites More sharing options...
Roger440 Posted August 9, 2006 Report Share Posted August 9, 2006 Not that much of a surprise it breaks then really. If the top mount is in a very different plane, then the damper will be trying to pivot around the top mount, but it will be resisting it owing to the way its mounted. The forces have to go somewhere, and it seems, straight into the damper rod. Quote Link to comment Share on other sites More sharing options...
Tony Posted August 9, 2006 Author Report Share Posted August 9, 2006 Not that much of a surprise it breaks then really. If the top mount is in a very different plane, then the damper will be trying to pivot around the top mount, but it will be resisting it owing to the way its mounted. The forces have to go somewhere, and it seems, straight into the damper rod. Agreed, i think the pivotal plan is -20o hence the clean brake, bad mistake by the engineers don't you think! Quote Link to comment Share on other sites More sharing options...
Roger440 Posted August 9, 2006 Report Share Posted August 9, 2006 Serious mistake, but as i'm finding, not that uncommon. In my previous life such fundamental design errors were generally not so easily tolerated, or if they were, then additional maintenance activities were in place to prevent failure. I should have another damper story to relate by the end of the week. More design errors!! Quote Link to comment Share on other sites More sharing options...
Tony Posted August 9, 2006 Author Report Share Posted August 9, 2006 Serious mistake, but as i'm finding, not that uncommon. In my previous life such fundamental design errors were generally not so easily tolerated, or if they were, then additional maintenance activities were in place to prevent failure. I should have another damper story to relate by the end of the week. More design errors!! We eagerly await... wim's provenance is excellence by desire, crash and burn by design. Any examples you have are very welcome! Quote Link to comment Share on other sites More sharing options...
scorps Posted August 9, 2006 Report Share Posted August 9, 2006 My brothers wifes got the Scenic and ferries the kids in em all day, whats the consequence of this at 60/70 mph? Quote Link to comment Share on other sites More sharing options...
Tony Posted August 10, 2006 Author Report Share Posted August 10, 2006 My brothers wifes got the Scenic and ferries the kids in em all day, whats the consequence of this at 60/70 mph? Minimal.... even after the brake the vehicle is still stable, the common complaint is the knocking at the rear as the two sections collide during compression. Quote Link to comment Share on other sites More sharing options...
IanF Posted August 11, 2006 Report Share Posted August 11, 2006 Curious... has the inner rod actually broken or has it 'just' fallen out of a socket in the top cover? have to cut open the top cover to see how the inner rod is connected to the top bit (LOL there's a song in there somewhere #The damper rods connected to the knuckle joint....#) The damper supresses the inherent resonance in the spring mass system. So as long as you avoid driving at just the right speed over a bumpy road the wheels ought to stay in contact with the road. Could be fun, in an old banger that is. Theoretically even small bumps will get a damperless car airborn if you get the speed and bump pitch just right, I say theoretically because I have no personal experience but some mad fool must have tried it. Quote Link to comment Share on other sites More sharing options...
Tony Posted August 11, 2006 Author Report Share Posted August 11, 2006 Curious... has the inner rod actually broken or has it 'just' fallen out of a socket in the top cover? have to cut open the top cover to see how the inner rod is connected to the top bit (LOL there's a song in there somewhere #The damper rods connected to the knuckle joint....#) The damper supresses the inherent resonance in the spring mass system. So as long as you avoid driving at just the right speed over a bumpy road the wheels ought to stay in contact with the road. Could be fun, in an old banger that is. Theoretically even small bumps will get a damperless car airborn if you get the speed and bump pitch just right, I say theoretically because I have no personal experience but some mad fool must have tried it. Deffo snapped, albeit clean.... Umm that fool has been me actually With this particular car the replacement dampers were coming late in the day so i removed them both ready for the new units.... but i needed to remove the car from the ramp and drove it a short distance....... it was, up ,down, up, down after 40ft i looked like this... Slightly less fluffy though The one to get airborne is the old Citroen CN? or CX?.... Raise the Hydroelastic suspension to high (wheel removal) then drive it!!!! With the smallest bump the whole front end will leave the ground 'for real' Quote Link to comment Share on other sites More sharing options...
discount tyres dan Posted August 11, 2006 Report Share Posted August 11, 2006 another fun one is in a xantia.. when you are sitting at lights put the handbrake on so the front wheels cant move.. then pump the brake pedel realy hard and fast for about 30 seconds.. when you stop pumping the back end will shoot up to max height until it settles again on its own Quote Link to comment Share on other sites More sharing options...
Tony Posted August 12, 2006 Author Report Share Posted August 12, 2006 another fun one is in a xantia.. when you are sitting at lights put the handbrake on so the front wheels cant move.. then pump the brake pedel realy hard and fast for about 30 seconds.. when you stop pumping the back end will shoot up to max height until it settles again on its own How did you find this out dan Quote Link to comment Share on other sites More sharing options...
discount tyres dan Posted August 12, 2006 Report Share Posted August 12, 2006 bored at the lights one day in stanmore.. there realy was nothing else to do Quote Link to comment Share on other sites More sharing options...
Tony Posted August 12, 2006 Author Report Share Posted August 12, 2006 bored at the lights one day in stanmore.. there realy was nothing else to do Little research then....... I like it .... an Exantia nose wheelie.... Good work mate. Quote Link to comment Share on other sites More sharing options...
Rich Posted March 19, 2007 Report Share Posted March 19, 2007 Me girlfriends old man needs to replace another shock on his scenic!! Makes one hellava bang when going over bumps!! It's been like this for a good few months though, could he be causing anymore damage by not changing it immediately? Quote Link to comment Share on other sites More sharing options...
Tony Posted March 19, 2007 Author Report Share Posted March 19, 2007 Me girlfriends old man needs to replace another shock on his scenic!! Makes one hellava bang when going over bumps!! It's been like this for a good few months though, could he be causing anymore damage by not changing it immediately? Yes. The radius arm is surpassing designed curves... And the handling is very impaired, tell him to get it changed! Quote Link to comment Share on other sites More sharing options...
Rich Posted March 19, 2007 Report Share Posted March 19, 2007 Reason I asked is that he hasn't noticed any difference in tyre wear or handling! He's changing it next week I think as the banging is getting on his nerves. I was surprised at how easy they snap though. It happened when he was driving onto a ferry and went down with a bang. He'd only replaced it a few months beforehand aswell... Quote Link to comment Share on other sites More sharing options...
Tony Posted March 19, 2007 Author Report Share Posted March 19, 2007 Reason I asked is that he hasn't noticed any difference in tyre wear or handling! He's changing it next week I think as the banging is getting on his nerves. I was surprised at how easy they snap though. It happened when he was driving onto a ferry and went down with a bang. He'd only replaced it a few months beforehand aswell... When needed the handling will be impaired... In addition the unit must still be under guarantee. Take it back!!!! Quote Link to comment Share on other sites More sharing options...
don Posted December 30, 2007 Report Share Posted December 30, 2007 Just to let you know My Renault Megane Scenic has just had the rear shock fail in the same way as the pics. To be honest I hit a road repair ramp near me and that was it "bang bang". They are not very hard units to replace; I have the car up on axles stands ready (for the new shocks it should not take more than 20mins to fit. However I have been quoted very odd prices for the all in repair cost. Formula 1 centres £239 (are they taking the P***) Kwick Fitt £139 (Fair for them) PTS £113 (they are a local good Exhaust centre) Me £70 (engineer that just don’t trust Quick fit centres) To be honest I normally shop around for a repair cost and then always seem to find my self on my back doing the repair for myself. But I am an Engineer and probably have saved thousands in garages costs. TA Don PS I will be keeping the old good shock for my trips to France just in case it fails again and will be taking care on all those speed ramps. Quote Link to comment Share on other sites More sharing options...
Tony Posted December 30, 2007 Author Report Share Posted December 30, 2007 Hi Don.... Yourself as an engineer i think we can agree Renault has some real design issues with the stress/material load properties for the Megan/Scenic As you have probably observed the brake is clean, almost surgical and obviously due to the compressive radii of the damper, what puzzles me is that the shaft is not bent? Quote Link to comment Share on other sites More sharing options...
Rich Posted December 30, 2007 Report Share Posted December 30, 2007 Yeah they're very easy, other half's dad did it in half hour. He then got rid of the car for the newer scenic and the shock went on that soon after getting it. Luckily they replaced it on warranty though, he only went over a speed bump. Does seem to be a weak spot... Quote Link to comment Share on other sites More sharing options...
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