Master Thread - Weight Savings Tips
05-10-2011, 11:38 AM
#212
4th Gear
Join Date: May 2010
Location: Paris, France
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Hi,
I never seen that somebody tried to remove the engine vibration damper ?
It weigth approx. 10 lbs
I have a 928S euro 1980 and when I purchased it, the previous owner had removed it. I did few thousand km with that configuration with no problem. Per report to the S2 I have also, the motor seems to me more nervous.
What can be the risk ?
Does anybody else tried that ?
I never seen that somebody tried to remove the engine vibration damper ?
It weigth approx. 10 lbs
I have a 928S euro 1980 and when I purchased it, the previous owner had removed it. I did few thousand km with that configuration with no problem. Per report to the S2 I have also, the motor seems to me more nervous.
What can be the risk ?
Does anybody else tried that ?
05-10-2011, 01:37 PM
#213
Rennlist Member
yeah, what the heck is it really doing up there? 10 lbs that could be just removed and its rotating! heck, the S4 has a 40 lb clutch assembly bolted on the other end of the crank, so why do you even need a damper? people dont think twice about using the double disc clutch to drop 25lbs off what is attached to the rear of the crank, so what is the diference if it comes off the damper? is it because the 10lbs is rubber mounted?
just curious. I suspect the main objective is for the rubber assembled vibration damper, is to absorb harmonic vibrations during all the RPM ranges.
i know in step motors (electric motors that are pulsed, so they act like little engines as far as vibration), a damper will make the motor run silky smooth, and without it, it will vibrate and lose torque in the resonance rpm ranges.
but, any load on them, has the same effect, so im wondering if we really need the damper, given we have a 25lb min, clutch, alternator, powersteering pump, attached, as well as when in gear, the drive wheels, all the way through the torque tube! thats a lot of mass attached to the engine in gear, and even out of gear.
just curious. I suspect the main objective is for the rubber assembled vibration damper, is to absorb harmonic vibrations during all the RPM ranges.
i know in step motors (electric motors that are pulsed, so they act like little engines as far as vibration), a damper will make the motor run silky smooth, and without it, it will vibrate and lose torque in the resonance rpm ranges.
but, any load on them, has the same effect, so im wondering if we really need the damper, given we have a 25lb min, clutch, alternator, powersteering pump, attached, as well as when in gear, the drive wheels, all the way through the torque tube! thats a lot of mass attached to the engine in gear, and even out of gear.
Hi,
I never seen that somebody tried to remove the engine vibration damper ?
It weigth approx. 10 lbs
I have a 928S euro 1980 and when I purchased it, the previous owner had removed it. I did few thousand km with that configuration with no problem. Per report to the S2 I have also, the motor seems to me more nervous.
What can be the risk ?
Does anybody else tried that ?
I never seen that somebody tried to remove the engine vibration damper ?
It weigth approx. 10 lbs
I have a 928S euro 1980 and when I purchased it, the previous owner had removed it. I did few thousand km with that configuration with no problem. Per report to the S2 I have also, the motor seems to me more nervous.
What can be the risk ?
Does anybody else tried that ?
05-10-2011, 02:25 PM
#214
Developer
Thread Starter
Indi-928 - do some reading before you go in that direction. The harmonic balancer is just what it says, it seeks to nulify the harmonics in the crank caused by the hammering of the pistons and rods during the cycle. Do NOT run an Ott-cycle engine without one!
A brief internet search will provide you many expanations why and a few interesting photos and stories.
A brief internet search will provide you many expanations why and a few interesting photos and stories.
05-10-2011, 02:31 PM
#215
Chronic Tool Dropper
Lifetime Rennlist
Member
Lifetime Rennlist
Member
The front dampener prevents 'ringing' in the crankshaft. The crank is twisted from eight different points on its length every two revolutions, so the amount of twist changes depending on how much of the crank is between the firing piston and its load at the rear. Meanwhile, forward of the firing piston, there's virtually no load and the front of the crank 'rings' like a bell with every ignition pulse. The observation on using load to damapen the ringing is a great one, and that's what keeps the back of the crank from ringing. The damper offers a way to kill the ringing on the unloaded front end of the crank.
The effects of resonant ringing are well documented. Perhaps the most immediate is the effect it has on oil flow patterns in main bearings. The oil moves with the moving crank bearing surfaces, and will tend to ebb and flow to the point where the film needed to support the crank is compromised. If the bearings and oil film are OK, there is the issue of longer-term cyclic stress damage to the crankshaft itself. The metal can stand a certain number of flex cycles before it starts to fatigue and eventually crack/fail. Point is that operating without the dampener may seem to be OK, but the damage you do is often invisible to you until the cracks and fractures expand and the eventually crank breaks.
Interesting experiment: Suspend a bare crank vertically, and tap it with a hammer. Support it at different places with your hand as you tap, and feel where the vibration moves. Note how your hand dampens the vibrations, and imagine that the rubber-isolated ring on the crank damper will do the same. The dampener on the engine is designed to eliminate oscillations in the rotating speed of the crank, so putting the dampener on the crnk won't kill some of the vibrations from tapping it. Notice how a somewhat lateral tap on a crank throw won't cause the same ringing when the dampener is installed; it's doing its job.
The effects of resonant ringing are well documented. Perhaps the most immediate is the effect it has on oil flow patterns in main bearings. The oil moves with the moving crank bearing surfaces, and will tend to ebb and flow to the point where the film needed to support the crank is compromised. If the bearings and oil film are OK, there is the issue of longer-term cyclic stress damage to the crankshaft itself. The metal can stand a certain number of flex cycles before it starts to fatigue and eventually crack/fail. Point is that operating without the dampener may seem to be OK, but the damage you do is often invisible to you until the cracks and fractures expand and the eventually crank breaks.
Interesting experiment: Suspend a bare crank vertically, and tap it with a hammer. Support it at different places with your hand as you tap, and feel where the vibration moves. Note how your hand dampens the vibrations, and imagine that the rubber-isolated ring on the crank damper will do the same. The dampener on the engine is designed to eliminate oscillations in the rotating speed of the crank, so putting the dampener on the crnk won't kill some of the vibrations from tapping it. Notice how a somewhat lateral tap on a crank throw won't cause the same ringing when the dampener is installed; it's doing its job.
05-10-2011, 02:42 PM
#216
Rennlist Member
excellent description !
bottomline, you need it! whats 10lbs anyway! take 14 out of the car somewhere and call it a day!
mk
bottomline, you need it! whats 10lbs anyway! take 14 out of the car somewhere and call it a day!
mk
The front dampener prevents 'ringing' in the crankshaft. The crank is twisted from eight different points on its length every two revolutions, so the amount of twist changes depending on how much of the crank is between the firing piston and its load at the rear. Meanwhile, forward of the firing piston, there's virtually no load and the front of the crank 'rings' like a bell with every ignition pulse. The observation on using load to damapen the ringing is a great one, and that's what keeps the back of the crank from ringing. The damper offers a way to kill the ringing on the unloaded front end of the crank.
The effects of resonant ringing are well documented. Perhaps the most immediate is the effect it has on oil flow patterns in main bearings. The oil moves with the moving crank bearing surfaces, and will tend to ebb and flow to the point where the film needed to support the crank is compromised. If the bearings and oil film are OK, there is the issue of longer-term cyclic stress damage to the crankshaft itself. The metal can stand a certain number of flex cycles before it starts to fatigue and eventually crack/fail. Point is that operating without the dampener may seem to be OK, but the damage you do is often invisible to you until the cracks and fractures expand and the eventually crank breaks.
Interesting experiment: Suspend a bare crank vertically, and tap it with a hammer. Support it at different places with your hand as you tap, and feel where the vibration moves. Note how your hand dampens the vibrations, and imagine that the rubber-isolated ring on the crank damper will do the same. The dampener on the engine is designed to eliminate oscillations in the rotating speed of the crank, so putting the dampener on the crnk won't kill some of the vibrations from tapping it. Notice how a somewhat lateral tap on a crank throw won't cause the same ringing when the dampener is installed; it's doing its job.
The effects of resonant ringing are well documented. Perhaps the most immediate is the effect it has on oil flow patterns in main bearings. The oil moves with the moving crank bearing surfaces, and will tend to ebb and flow to the point where the film needed to support the crank is compromised. If the bearings and oil film are OK, there is the issue of longer-term cyclic stress damage to the crankshaft itself. The metal can stand a certain number of flex cycles before it starts to fatigue and eventually crack/fail. Point is that operating without the dampener may seem to be OK, but the damage you do is often invisible to you until the cracks and fractures expand and the eventually crank breaks.
Interesting experiment: Suspend a bare crank vertically, and tap it with a hammer. Support it at different places with your hand as you tap, and feel where the vibration moves. Note how your hand dampens the vibrations, and imagine that the rubber-isolated ring on the crank damper will do the same. The dampener on the engine is designed to eliminate oscillations in the rotating speed of the crank, so putting the dampener on the crnk won't kill some of the vibrations from tapping it. Notice how a somewhat lateral tap on a crank throw won't cause the same ringing when the dampener is installed; it's doing its job.
05-10-2011, 04:49 PM
#217
4th Gear
Join Date: May 2010
Location: Paris, France
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Thanks,
If I well understand, the risk is to fatigue and eventually crack/fail the crankshaft for an hypothetic small advantage.
I have in stock (not from that car) a very old damper full metal for 928. Is it ok or may be better to install a newer rubber one ?
My 928 is an S euro model, 5 speed, 300 HP year 1980.
To stay in the subject, we removed the 4 seats replaced by 2 Sparco, replaced the wheel by a Momo, removed the rear shock absorber, replaced the rear window with a macrolon one, removed all the AC, replaced the fan with an electric one, replaced the door interior by a very light one. The wheel are CUP 2 -8” front and CUP2-9” rear…
I still have the front light, I like too much them,
Sorry, I didn't found how to upload photo.
If I well understand, the risk is to fatigue and eventually crack/fail the crankshaft for an hypothetic small advantage.
I have in stock (not from that car) a very old damper full metal for 928. Is it ok or may be better to install a newer rubber one ?
My 928 is an S euro model, 5 speed, 300 HP year 1980.
To stay in the subject, we removed the 4 seats replaced by 2 Sparco, replaced the wheel by a Momo, removed the rear shock absorber, replaced the rear window with a macrolon one, removed all the AC, replaced the fan with an electric one, replaced the door interior by a very light one. The wheel are CUP 2 -8” front and CUP2-9” rear…
I still have the front light, I like too much them,
Sorry, I didn't found how to upload photo.
Hi,
I never seen that somebody tried to remove the engine vibration damper ?
It weigth approx. 10 lbs
I have a 928S euro 1980 and when I purchased it, the previous owner had removed it. I did few thousand km with that configuration with no problem. Per report to the S2 I have also, the motor seems to me more nervous.
What can be the risk ?
Does anybody else tried that ?
I never seen that somebody tried to remove the engine vibration damper ?
It weigth approx. 10 lbs
I have a 928S euro 1980 and when I purchased it, the previous owner had removed it. I did few thousand km with that configuration with no problem. Per report to the S2 I have also, the motor seems to me more nervous.
What can be the risk ?
Does anybody else tried that ?
02-26-2012, 06:40 PM
#218
Developer
Thread Starter
We already knew that we could save 14 pounds from just replacing the rear hatch glass with clear polycarbonate. That is shown on this thread in post #114.
But we didn't know how much weight we could get out of the steel hatch. Answer: 5.6 pounds. We have completely removed the hinges and will be just using hood pins at the top instead. We had already removed the latch and were using hood pins at the bottom anyway.
As the pictures show we removed the weight at each end of the hatch and along the sides.
Happy with 5.6 pounds - especially because it was relatively high.
But we didn't know how much weight we could get out of the steel hatch. Answer: 5.6 pounds. We have completely removed the hinges and will be just using hood pins at the top instead. We had already removed the latch and were using hood pins at the bottom anyway.
As the pictures show we removed the weight at each end of the hatch and along the sides.
Happy with 5.6 pounds - especially because it was relatively high.
02-27-2012, 05:50 PM
#222
Rennlist Member
all of them??? 64 of them? (looks like 32 per side)
no you didnt, you raised it and put stillts under each side. and then a sheet of aluminum as the moonroof.
no you didnt, you raised it and put stillts under each side. and then a sheet of aluminum as the moonroof.
02-27-2012, 09:28 PM
#223
Rennlist Member
Aero-wise, what's happening for pressure on the hatch glass surface. I replaced my rear glass with poly-c, and when I got over 100mph down the front straight I heard thunderous "whump!!" It was so loud I almost jumped out of my skin. Turned out it was the rear "window" flexing. I don't know if it was flexing in or out. I'm presuming inside the cab is a high pressure area (since there are no door windows) so the poly was bending out. I don't think the short little braces you have Carl would work on what I 've got, I think I need the supports that go all the way across the glass.
Is it a concern to just have hood pins holding this thing on? If they fail you're going to have one heck of a frisbee flying off the back of your 928.
I like the idea, a great way to shed some more pounds without having to find the holy grail of 928 race car parts - the coveted fiberglass hatch.
Is it a concern to just have hood pins holding this thing on? If they fail you're going to have one heck of a frisbee flying off the back of your 928.
I like the idea, a great way to shed some more pounds without having to find the holy grail of 928 race car parts - the coveted fiberglass hatch.
02-28-2012, 12:01 PM
#224
Developer
Thread Starter
Adam.
those are not "short little braces" They are required window tabs.
YES - if you replace the glass with plastic, it is very important that you support the center of the plexi from flexing some how. Properly venting the hatch so it does not build up pressure with the windows open also helps, I have found. Thats why the NACA ducts are mounted backwards and in the bottom of the plexi.
I have seen many nice designs for the braces. Here is what I did:
those are not "short little braces" They are required window tabs.
YES - if you replace the glass with plastic, it is very important that you support the center of the plexi from flexing some how. Properly venting the hatch so it does not build up pressure with the windows open also helps, I have found. Thats why the NACA ducts are mounted backwards and in the bottom of the plexi.
I have seen many nice designs for the braces. Here is what I did:
02-28-2012, 12:04 PM
#225
Developer
Thread Starter
Hi,
I never seen that somebody tried to remove the engine vibration damper ?
It weigth approx. 10 lbs
I have a 928S euro 1980 and when I purchased it, the previous owner had removed it. I did few thousand km with that configuration with no problem. Per report to the S2 I have also, the motor seems to me more nervous.
What can be the risk ?
Does anybody else tried that ?
I never seen that somebody tried to remove the engine vibration damper ?
It weigth approx. 10 lbs
I have a 928S euro 1980 and when I purchased it, the previous owner had removed it. I did few thousand km with that configuration with no problem. Per report to the S2 I have also, the motor seems to me more nervous.
What can be the risk ?
Does anybody else tried that ?