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Aug 11, 2011 12:05 pm
Aug 11, 2011 12:05 pm
Subject: Re: G9 gearbox
Hi Collin and Laurence,
We have a very good "Fix" for the original type harmonic damper fitted to Lagondas,
1. Remove it from the engine,
2. Practice Discuss throwing and see how far you can get it.
3. Leave it there!
The reason for this.
M45s and LG45s and especially the early M45s all have a "harmonic period" at about 2500 rpm, this is where you really feel the engine being quite "harsh" and if kept here can damage the bearings etc. Some engines suffer worse than others for many reasons but all have it to some degree.
When we looked into a remedy for this we obviously looked at the damper. Making it tighter or looser did have an effect but it only seemed change the frequency range up or down by about 100 rpm or so, therefore sometimes taking it away from our regular cruising speed and so making it feel less of a problem. But not getting rid of the problem.
So, we made and fitted some modern dampers and after experimenting with diameters etc we had great success! When fitting a modern Rubber bonded damper we found that the problem was completely gone up to 3500 rpm and never surfaced again! We found that the engine would seem to have it back again a little at about 3750 on a standard M45 engine and about 4000 on an LG, but as these are speeds that we should not be using on standard cranks and rods then it's immaterial.
On the big performance type engines we build we use a more expensive "Fluid filled" damper and then all is well for any rpm you care to imagine!
This is what we do with every engine we build now without fail and even do it on the V12s as the standard damper on those is a joke and although you don't feel it through the car much due to better mounts etc, has more of a problem then the 4.5s!
Modern measuring equipment picks it up easily!
Regards,
Julian
Hi Collin and Laurence,
We have a very good "Fix" for the original type harmonic damper fitted to Lagondas,
1. Remove it from the engine,
2. Practice Discuss throwing and see how far you can get it.
3. Leave it there!
The reason for this.
M45s and LG45s and especially the early M45s all have a "harmonic period" at about 2500 rpm, this is where you really feel the engine being quite "harsh" and if kept here can damage the bearings etc. Some engines suffer worse than others for many reasons but all have it to some degree.
When we looked into a remedy for this we obviously looked at the damper. Making it tighter or looser did have an effect but it only seemed change the frequency range up or down by about 100 rpm or so, therefore sometimes taking it away from our regular cruising speed and so making it feel less of a problem. But not getting rid of the problem.
So, we made and fitted some modern dampers and after experimenting with diameters etc we had great success! When fitting a modern Rubber bonded damper we found that the problem was completely gone up to 3500 rpm and never surfaced again! We found that the engine would seem to have it back again a little at about 3750 on a standard M45 engine and about 4000 on an LG, but as these are speeds that we should not be using on standard cranks and rods then it's immaterial.
On the big performance type engines we build we use a more expensive "Fluid filled" damper and then all is well for any rpm you care to imagine!
This is what we do with every engine we build now without fail and even do it on the V12s as the standard damper on those is a joke and although you don't feel it through the car much due to better mounts etc, has more of a problem then the 4.5s!
Modern measuring equipment picks it up easily!
Regards,
Julian