ideas on crank damper's...

[sasquatch]

ok im looking in to all the parts to build up my motor and i hear about all the miata guys blowing up oil pumps when they pass the 250hp range... so fordged oil pump gears are a must for my motor but i also want to stick a damper on the end... but there is no way in heck im paying 550 bucks for one.... and i have been doing some reading but ati is not saying "how it works..."

but from what i am seeing in the cutout, all it is, is a center hub thats bolted to the crank, then a layer of rubber so there is some flex, then a ring/weight around it all with your belt grove carved in to it...

so when it spins, the center hub will take the vibrations from the crank and transfer them in to the rubber and get dampend by the mass of the outside ring... right?

So.... what if i made my own... FOR FREE!!!! all i need is a center hub and an outside ring (cam be made easy with a bit of help from a lathe or something... then center them and lay in some rubber and let it harden... (maybe some "window weld" like they use in the motor mount mods...)

any ideas?
will it work?

[NicholasJackson]

Id say go for it!

You'd wanna make sure you have the weight balanced correctly.

I was driving along the motorway the other day and one of my tyres had slightly more rubber on one side and it ripped itself to shreds. It had about 80% tread.

[Brayy]

What tyre did you destroy ? If you build your own and it goes downhill what's the damage it can cause ? Anything super serious and I wouldn't bother.. if not then defenatly go for it.

[Safety Guy]

So you're going to use window weld or other DIY rubber filling to attach two steel parts together that will attach to the crank nose area, carrying power to the alt belt and turning at up to 6000 or so rpm?

All I'll say is you better know what you're doing!

Karl

[Rocketman]

That's all great, I've thought about that too.

It's my understanding that the dampers are "tuned"
Proportion of weight on the outer edge vs. mass of rubber & its hardness/shore rating = its damping ability = tuned to take out harmful crank harmonics at x x and x RPM's??

Just throwing a bunch of stuff together with a random urethane might work, but could also be far from optimal or even useless altogether.

http://en.wikipedia.org/wiki/Harmonic_balancer

I had read an excellent article regarding harmonic balancers & their effect on the engine, with or without (it was tailored towards those considering running billet aluminum UDP's). I'll try to dig it up, it's some very useful info.

[FB71]

Rocketman is pretty spot-on. Its not just the shore rating of the rubber; it has to have a specific shear strength. I would NOT use urethane. My suspicion is that it would be too hard, and shear apart before it offered any torsional flexibility.

I'm running the stock 90-94 B6 damped crank pulley, with the ribbed pulley cut off, and the inner diameter ground slightey larger with a Dremel, to accomodate a Festiva A/C pulley.

[Hot_Wheels]

ask Nerd he adapted a 4g63? to a festiva one. but as stated it seems like there is a lot of science and tuning so what works for one motor maybe different for another motor. Its on my list too buy as well but 500 is alot to for out, i keep my eye on the miata forums.

[Nerd Racing]

:cracks knuckles:

If you just try and pour rubber in between the two metal pieces you will have something that is probably too stiff or off frequency for the engine's main torsional peaks. Then there is the durability aspect... the rubber is not only poured in there, but it is also bonded when injection molded, for increased life. Crankshaft vibrations are a tricky thing... if you change your rotating masses along the engine system (aka lightweight flywheel, knife edging, stroked cranks...etc) you will change the torsional vibration frequencies that are present in the system. Another thing that can change torsional vibrations is the cylinder pressure, power levels, cast vs. forged cranks, addition of superchargers, turbo pulses, injection pressures in diesels...etc. Sometimes at work it makes my head want to explode! If you want a damper that will be effective to just about every variation of your system you should consider a viscous damper. I actually design them for a living with the company that manufacturers Fluidampr and Vibratech TVD large industrial viscous dampers. They are effective at any frequency because the damping mass is not bonded to the crank hub. They also have an advantage that comes with not being bonded, the crank does not feel the full weight of the damper when the engine is operating. The vibration energy with self center and suspend the damping mass so the crank will feel only half the weight of the damping mass, which usually equates to 2/3's the weight of the damper (depending on model and design).


I did adapt a 4G63 Fluidampr to fit my BP. Unfortunately the revision I used was older and had more material to trim off, the more recent ones will not work. It is much larger in diameter so it does not allow the use of the timing pointer and spins accessories faster. I swear the car revs faster with a 10ish lb damper than it did with the 2 pound stamped steel aspire pulley. I also had a nasty exhaust resonance between 3 and 4k rpm with the aspire pulley, with the fluidampr it was decreased and shifted down to 2-3k rpms where I spend much less time and can rev through it faster. The car also smoothed out at idle so much that I can idle it at 500 rpm where I had to hit 800 to be almost as smooth before.

I am working on gaining support to produce a Large nose B-series one, but it is an older engine and does not do well at endearing marketing/sales.

I planned on seeing how to adapt the Honda B-series damper, if there is enough interest I can look into it. This would be a dual 4 rib belt setup and you would not be able to trim it up to clear the frame rail without getting into the damper internals. The frame would have to be boxed/bashed to work in a festiva.

If you guys are interested I can post up the pics of what I have right now on my protege. (adapted 4G63 Fluidampr)

[IdealSociety]

Just FYI, the factory BP crank pulley already has a rubber insert that holds the center and outer section together.

I know because when i put my first one on a lathe to take off the AC/PS section it spun a bit and tore loose. The second one i machined much more slowly and it held together but gave me a nice burned rubber smell as i dug into it.

[Hot_Wheels]

Nerd please post pics

[Nerd Racing]

I'll get some pics up when I get home, photobucket is blocked here at work.

[FB71]

:cracks knuckles:

If you just try and pour rubber in between the two metal pieces you will have something that is probably too stiff or off frequency for the engine's main torsional peaks. Then there is the durability aspect... the rubber is not only poured in there, but it is also bonded when injection molded, for increased life. Crankshaft vibrations are a tricky thing... if you change your rotating masses along the engine system (aka lightweight flywheel, knife edging, stroked cranks...etc) you will change the torsional vibration frequencies that are present in the system. Another thing that can change torsional vibrations is the cylinder pressure, power levels, cast vs. forged cranks, addition of superchargers, turbo pulses, injection pressures in diesels...etc. Sometimes at work it makes my head want to explode! If you want a damper that will be effective to just about every variation of your system you should consider a viscous damper. I actually design them for a living with the company that manufacturers Fluidampr and Vibratech TVD large industrial viscous dampers. They are effective at any frequency because the damping mass is not bonded to the crank hub. They also have an advantage that comes with not being bonded, the crank does not feel the full weight of the damper when the engine is operating. The vibration energy with self center and suspend the damping mass so the crank will feel only half the weight of the damping mass, which usually equates to 2/3's the weight of the damper (depending on model and design).


I did adapt a 4G63 Fluidampr to fit my BP. Unfortunately the revision I used was older and had more material to trim off, the more recent ones will not work. It is much larger in diameter so it does not allow the use of the timing pointer and spins accessories faster. I swear the car revs faster with a 10ish lb damper than it did with the 2 pound stamped steel aspire pulley. I also had a nasty exhaust resonance between 3 and 4k rpm with the aspire pulley, with the fluidampr it was decreased and shifted down to 2-3k rpms where I spend much less time and can rev through it faster. The car also smoothed out at idle so much that I can idle it at 500 rpm where I had to hit 800 to be almost as smooth before.

I am working on gaining support to produce a Large nose B-series one, but it is an older engine and does not do well at endearing marketing/sales.

I planned on seeing how to adapt the Honda B-series damper, if there is enough interest I can look into it. This would be a dual 4 rib belt setup and you would not be able to trim it up to clear the frame rail without getting into the damper internals. The frame would have to be boxed/bashed to work in a festiva.

If you guys are interested I can post up the pics of what I have right now on my protege. (adapted 4G63 Fluidampr)

nice! thank you for taking the time to explain it... I was too lazy!

[Nerd Racing]

no problem! I end up having to explain it almost 5 times a week so I'm used to it lol.

[eurotiva]

I use a trimmed EGT dampner. I lost an oil pump to a stock festiva pulley. So far mine has worked great.

[fastivaB6TG25MR]

what did your oil pump do when it started going out? cause im running a festy crank pulley on mine and im a bit above the power threshold for destroying oil pumps...