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| Lightening crank damper? https://www.ausmini.com/forums/viewtopic.php?f=5&t=60287 |
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| Author: | Asphalt [ Thu Jan 14, 2010 12:23 am ] |
| Post subject: | Lightening crank damper? |
Hi! I weighted an 1275 A+ crank pulley today. I was surprised at the weight: 1.3kg!  (the undamped 998 pulley weights only 505g!)
Since I wan to reduce the rotating masses but not set a damper aside (aiming for high revs) - can those pullies be lightened? Or does this dramaticaly reduce the pulley's ability to damp? I guess it does - but I though I'd better ask the experts 
Cheers, Jan |
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| Author: | lmbm [ Thu Jan 14, 2010 5:09 am ] |
| Post subject: | Lightening crank damper |
I'ts a common mod here for the racers, not sure what happens to damping ability. I woudn't do it to save a few grams. Cheers Luis |
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| Author: | GT mowog [ Thu Jan 14, 2010 6:33 am ] |
| Post subject: | |
Probably Dave Rosenthal would be one here guy to know if it would still be effective as a damper (I tend to think that it would reduce it damping ability), however as for gains, they would be very minimal and possibly un-noticable. The amount of rotating mass at such a small radius won't make much difference at all. I'd tend to leave it. If your looking for gains here, wedge the crank, lighten the rods (there are some really good after market ones about) and get the lightest flywheel assembly, including the backing plate, you can afford. |
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| Author: | awdmoke [ Thu Jan 14, 2010 9:16 am ] |
| Post subject: | |
There are various kits to lighten the Cooper S style damper. Mine was totally shagged, so I got a complete aftermarket unit New Vs old 
New ROMAC Part # 239SA 840g Original 1,440g That's a 42% weight saving, most of it at the outer edge. |
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| Author: | drmini in aust [ Thu Jan 14, 2010 10:16 am ] |
| Post subject: | |
I got this one from Minis Plus, it's an MED. http://www.minis.com.au/minis/catalog/p ... 23ed3dbaaf |
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| Author: | Asphalt [ Thu Jan 14, 2010 10:35 am ] |
| Post subject: | |
Oh - they look both very good! Thanks!
Excuse my ignorance; they both are a two piece design, right? So the damper bolts onto the carrier which bolts onto the crank (unlike the single piece A+ pulleys)? Cheers, Jan PS: We don't see old Mini that often - for you this might be an odd question
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| Author: | drmini in aust [ Thu Jan 14, 2010 11:00 am ] |
| Post subject: | |
The Romac is a 1 piece but press assembled with a rubber strip then a circlip, it's not vulcanised. The MED is a 2 piece bolted together, like all the Cooper S were. The link I gave does not show the hub, it's available separately. |
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| Author: | Asphalt [ Thu Jan 14, 2010 10:09 pm ] |
| Post subject: | |
Thanks Kevin!
Looks like I might support my country with some nice, exorbitant import taxes soon  (or go for the MED kit)
Cheers, Jan |
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| Author: | mini7boy [ Sun Jan 17, 2010 12:37 pm ] |
| Post subject: | |
not a good idea at all. The gain from lightening the damper is minimal and the downside is that the damper will no longer work as designed since you have changed the mass of one of the two large metal bits. You would gain much more by making sure that you have lightened, or purchased the lightest parts available for flywheel, backing plate, crankshaft, rods, pistons, etc. Even if you have lightened everything else, you would be wasting your time/money lightening the damper and may actually do harm in the process. Dampers are, or should be, designed with great care paid to the weights of the metal bits and the properties of the elastomer that is used between the two large metal bits. The components determine the damping behavior of the damper as it interacts with the crankshaft to dampen torsional vibrations in the crank. If you lighten these pieces, you throw off the careful design that should have gone into the damper design. |
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| Author: | 74snail [ Sun Jan 17, 2010 1:05 pm ] |
| Post subject: | |
With single/ double row timing chains as they stretch and wear they produce their own harmonics which has the possibility over time to counter-act the lighter damper and put more harmonic stress on the crank and other internals than if you were using a standard damper. With a lighter damper it would be better combined with a belt drive timing kit ( as my Cousin recommended ) , the rubber belt acts like another damper. . |
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| Author: | GT mowog [ Sun Jan 17, 2010 2:11 pm ] |
| Post subject: | |
mini7boy wrote: not a good idea at all. The gain from lightening the damper is minimal and the downside is that the damper will no longer work as designed since you have changed the mass of one of the two large metal bits. You would gain much more by making sure that you have lightened, or purchased the lightest parts available for flywheel, backing plate, crankshaft, rods, pistons, etc.
Even if you have lightened everything else, you would be wasting your time/money lightening the damper and may actually do harm in the process. Dampers are, or should be, designed with great care paid to the weights of the metal bits and the properties of the elastomer that is used between the two large metal bits. The components determine the damping behavior of the damper as it interacts with the crankshaft to dampen torsional vibrations in the crank. If you lighten these pieces, you throw off the careful design that should have gone into the damper design. All the points raised here by mini7boy are also my thoughts on this. |
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| Author: | Asphalt [ Sun Jan 17, 2010 9:20 pm ] |
| Post subject: | |
@mini7boy: Thanks for the confirmation! I think I go for the MED damper kit.
@74snail: A double row chain is too heavy anyway 
We made a little comparison: Part: weight big/smal sprocket: Double row: 800/275g Spares Belt: 857/281g A+ single row: 405/198g Pulleys: A+ 998 (undamped): 505g A+ 1275 (damped): 1300g Cheers, Jan |
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