420R (S3) Radiator design issue, regular failures???

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CtrMint
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420R (S3) Radiator design issue, regular failures???

Hi All, 

As per my post on 7Up's thread my radiator has also failed, this is the 2nd in a total of 4500 miles, they seem to be doing approximately 2000 miles between failures.  Although that's a sample of 2, my original replacement rad from the build was also dodgy, so possibly 3.

I've checked the radiator this morning and it's failed in the same position very top passenger side vane in against the end tank. There is a pattern here, and I'm wondering if there is a design flaw which goes back to my original kit etc.

When I was sent my kit what I understand is the revised radiator wouldn't fit under my nose cone, not by millimeters, but by centimeters.  Caterham eventually stated they'd switched radiator designs and sent me a new rad and additional hanger (see image).  The new radiator design is still mounted using bobbins, but the hanger for the top bobbin is solidly mounted, and well look at the images for proximity to the top hose and the point of failure.  There is actual contact between the hanger and top hose.

Based on comments from the 7Up's thread, I checked for vibration, and yes there's a notable resonance in the rad at tick over which disappears once the engine spins up.  So I'm left considering if CC inadvertently missed something with the new hangers?  I'm no mechanical engineer, but surely this is a smoking gun?  The point of the solid mount, is the point of repeated failures.

Has anyone else got a 420R S3 late 2018, which has similar hangers? 

I'm trying to attend the Taffia so will need to source a replacement radiator, but at £600 (CC Parts) per 2000 miles this is just silly.  I need to come up with a solution/improvement to resolve this interference while maintaining fitment under the nose.  The club has always been an invaluable source of information and support, hope you can all assist.

Thanks

Mark

Jonathan Kay
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Can you see a reason why the end of the hanger bends up (and contacts the radiator) rather than down to the bobbin? Was that design introduced for a different type of radiator, and then for your type they added the extra piece that connects the hanger to the bobbin?

And regardless of the history and what the factory offers how about cutting off the upturned end of the hanger, inverting it and welding or bolting it back so that it engages the bobbin directly?

Jonathan

CtrMint
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I understand the design is used to pull the rad closer to the chassis or rather further up the nose cone, given the nose cone narrows the closer it gets to the grill.  If I were to rotate the hanger, I'd be pushing the radiator further down the nose cone, I guess by the length of the horizontal offset in the hanger.

Caterham 420R S3 Lotus Toxic Green,  Caterham 620R S3 Exocet Red. Blog: https://www.caterham7diaries.com
Jonathan Kay
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I was thinking of keeping the position of the radiator constant...

Jonathan

ScottR400D
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I think there's more to it than that, JK. I've never seen a rational explanation of why CC changed the design of the rad/cooler from that which had been fine (quality issues excepted) for years, to one that didn't fit at all well and needed the sort of cobbling together we see above. 

The most likely explanation I've heard is that they had a supply issue with one or more of the earlier design parts so started to put parts designed for something else (race cars) into kits.

I wonder if more recent models have been redesigned to avoid the issues Mark had and perhaps now include the suggestion you offer?

If that mount is a solid connection to the radiator, it could well be the source of Marks problem; but what's the bobbin doing there? At first I thought it was just and odd arrangement to connect the bobbin to the chassis but now see it's a solid connection.

Jonathan Kay
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"If that mount is a solid connection to the radiator, it could well be the source of Marks problem; but what's the bobbin doing there? At first I thought it was just and odd arrangement to connect the bobbin to the chassis but now see it's a solid connection."

I'm suggesting losing the solid connection and only having the connection through the bobbin...

Jonathan

CtrMint
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The solid connection is the hanger for the bobbin, I'l post a video to help.

Caterham 420R S3 Lotus Toxic Green,  Caterham 620R S3 Exocet Red. Blog: https://www.caterham7diaries.com
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Caterham 420R S3 Lotus Toxic Green,  Caterham 620R S3 Exocet Red. Blog: https://www.caterham7diaries.com
ChrisC
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I can't understand why your chassis mounting bracket is touching the radiator inlet.  I had no issues with that mounting.  The original top hose was to inflexible and put a lot of strain on the radiator inlet, thankfully I found that out when I cut it to short, ordered a replacement which was much more flexible and removed strain on the rad.

ChrisC
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The replacement hose was Caterham parts, just ordered off the website.

ScottR400D
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So it's not a solid connection, just looks so in the early image.