I’ve recently acquired a high-performance crankshaft damper (C5809, Metalastic 51/211) which has the steel outer ring, rather than the malleable cast iron one. The rubber is shot, and I was wondering if there is anywhere in the UK that rebuilds them? I can only find Damper Doctor in the US, and a place in NZ. If it can’t be done here I may end up sending it to NZ, as I’m sure the carriage cost will be less than the now exorbitant US postal charges. I’ve been thinking about replacing the one currently on the car, as I can see a bit of run-out when it’s turning.
I tried that route . I found Guy Broad would include your own damper when they get a batch done . Turnover was very low on them and it would take ages , so I didn’t bother . Might be worth a try .
Jim
Chris,
Until recently some of the “usual UK parts suppliers” offered the choice between a new one or reconditioning of your own original damper.
Now they only offer new dampers with a clear warning that reconditioned dampers may fail with catastrophic consequences under the bonnet.
I also remember that in the UK reconditioned versions were (even) more expensive than new ones. Just for info.
Bob K.
Received the damper today, and am glad to say it doesn’t need a rebuild! The rubber is still quite flexible, and nothing seems to have moved (they used a different rubber compound on the C5809 COMP dampers, I’ve read). The steel floating ring is thinner at 3/8"in. compared to 1/2"in. on the malleable iron standard dampers - this is due to the difference in weight of the two materials. I’ll just get it blasted, etch-primed and spray it black myself.
I think you’ll find the difference in density between iron and steel to be negligible. What is quite different is its fatigue and impact resistance. Iron is very strong in compression, but not so good in tension. Malleable and ductile iron can be alloyed to have similar allowable tensile stress properties as low grade carbon steel, but it is still more brittle.
I’m sure you’re right, Mike. Apparently, the weight of the COMP damper is about 3.3 kilos, but I don’t know what the standard one weighs. I would think a little bit more, as the physical size of the floating ring is a bit greater. It’s thicker, but only on the rim (1/2") which quickly reduces to what is almost certainly the 3/8" thickness of the COMP one. The steel ring is safer to higher revs - 5800rpm, I’ve read.
Actually, changing the amount of energy storage (or resistance) is most effectively done by increasing the diameter, not the weight. Therefore, it would be more critical to closely compare the diameter of the two units. The inertia increases linearly with increases in thickness, 10% thicker is 10% more storage. Changing the diameter increases the capacity proportional to the fourth power of the radius. In simple numbers, doubling the radius increases the MOI by factor of 16, while doubling the thickness only doubles it. The applicable design limitation here is hoop stress. The hoop stress increases proportional to the square of the angular velocity, so the stress at the rim is 4 times higher at 5,000 rpm than it is at 2,500 rpm. Making the disc thicker doesn’t change that, and making it larger makes hoop stress higher. The only remedy is to use a material with a higher allowable working stress, hence, steel over iron.
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Boy, you certainly know your stuff, Mike! I sort of understand it!! Actually, a COMP damper is a complete indulgence, as I don’t think I’ve ever had the car over 4000rpm! 