Custom Crank Pulley

[DragonCypher]

As some of you may know I'm in the process of building a supercharged 2.6, using an Eaton M90 (from a 3.8L Ford Thunderbird Supercoupe)

The m90 6-rib pulleys are easily available in a range of 2.4" to 3.8" for every 0.1".
If I have a 4.8" pulley on the crank and 3.8" on the blower that will give a 1.26:1 overdrive on the blower, which works out to 6.65 PSI (with 2555cc engine capacity)
And with a 2.4" on the blower (which can be stepped up to gradually) will be 2:1, which I worked out to be around 18.98 PSI

(min 12.5, max 28 PSI when the same setup is used on a 2L)


The standard item I pulled off my engine had 1 small V-pulley, and 2 large, the one nearest the front of the car being air con.. and who needs that

So I redesigned it so that the air con pulley is replaced by a 4.8" 6-rib PolyV

The measurements I used to make the 6-rib pulley I got from intense googling and it matches the pulley found on a truck, not the ford/gm supercharger version
So I'm doubting its accuracy.
I do have my original 3.275" that came with the blower but with only a pair of cheap verniers to measure with I'd rather factory specs to model from before any CNC-ing is done.
If anyone knows where to find them it would be much appreciated

The images are big in size but wont affect anyones downloads... they're highly compressed






-
Chris

[Rallyant]

Nice,

Id actually like a Harmonic damper for my motor one of these days, im guessing some custom work will be needed for that too.

[DragonCypher]

what does a harmonic balancer actually involve?
It may be worth incorporating into my design as long as its not too complex.

Also noone seemed to notice 1 major flaw I have.. I picked up the factory pulley from the supercharger the other day and counted 8 ribs, not 6.

I wonder if anyone has tried putting an 8-rib belt on a 6-rib pulley

[Superscan811]

I wonder if anyone has tried putting an 8-rib belt on a 6-rib pulley

Wouldn't be that difficult, as long as you had a stanley knife...

Cheers.

[amgis_obrut]

id be looking at any pulley that fits the belt, and just make an adapter to fit the astron balancer

[regor]

hey mate

dont no if ur intreasted or not.. but i have a mate in a fabrication shop... and he can laith ( don't no how to spell it).. but can make a custom harmonic ballancer...
in alloy, steel, ect...

he made mine for my super charger...
use some computer and types in the specs and the comp cuts and make it's spot on...
its cost a fair wack but i think it worth it...

or u can do wat i did first offfind a single pully bye its self (say like a water pump or something like that) and then use a spacer and bolt it to ur harmonic ballancer it worked perfect...i am pretty sure all astron engine have 4x holes in the front...

if u need more info doing or watever hit me back..
i have some good contacs that can help out and i have done stuf like this before..


cheers roger

[Rallyant]

what does a harmonic balancer actually involve?
It may be worth incorporating into my design as long as its not too complex.

Also noone seemed to notice 1 major flaw I have.. I picked up the factory pulley from the supercharger the other day and counted 8 ribs, not 6.

I wonder if anyone has tried putting an 8-rib belt on a 6-rib pulley

There actualy a Harmonic Damber, nothing to do with balance, Im guessing the supercharger might help to dampen any harmonics?
Have a read of this http://www.grapeaperacing.com/tech/dampers.pdf

Does anyone know what the resonate frequency of an average 4g54 crankshaft is?

Fallacies
The term harmonic balancer is used often to
describe a torsional damper. The truth is, it has
nothing to do with primary or secondary balance of
the rotating assembly. Some engines like the 400
Chevy are externally balanced and do have a
counterweighted damper (and flywheel), but this
weight has nothing to do with the primary function of
the damper, it is nothing more than a convenient
place to add needed weight to balance the
assembly.
A second myth is that running an aluminum
hub in place of a damper will make the engine rev
quicker from a reduction in rotating weight. This
may be true to a point, but the reduction of torsional
vibration far overshadows the extra weight. It has
been dyno proven time and time again that engines
make more power with a good damper. In the case
with stock type dampers, the biggest and heaviest
dampers usually make more power than the lighter
ones. Why? They can dampen more. The
aftermarket has developed many different types that
can do just as well or better as well as reduce
weight, which is even better.
Some say that a damper is not needed if the
engine is balanced well, which is total nonsense. As
I said above, it has nothing to do with the balance of
the rotating assembly. Others say that as long as
the valvetrain is well matched, a damper isn’t
needed. That is also false, but they are thinking a
bit more on it and there is a point to be made there.
The valvetrain harmonics have a lot to do with it, but
I’ll get into that later.
Torsional Vibrations
No matter how well a rotating assembly is
balanced there will be torsional vibrations. It is not
possible to counter act a torsional vibration through
primary or secondary balance. Torsional vibrations
must be dampened with an opposing force to resist
them. Since torsional vibrations are rotational, more
or less counterweight cannot help.
So what exactly are the cause torsional
vibrations? During each power stroke the cylinder
pressure applies a large load on the rod journal.
This load flexes the crank in the direction of rotation
(that journal speeds up in relation to the rest of the
crank). Once it flexes, it is followed by a rebound in
the opposite direction (the journal slows down in
relation to the rest of the crank). This rebound
resists crankshaft rotation. This happens with every
cylinder fire. The crankshaft actually vibrates by the
rod throws speeding up and slowing down rapidly.
Crankshaft rotation at a steady rpm is anything but
steady; the crankshaft is rapidly changing speed.
Very minute changes, but changes nonetheless.
The frequency of these vibrations is
determined by the power strokes of the engine. At
some point, higher in the rpm range, the frequency
of the power strokes will match the crankshafts
natural resonate frequency. This is when the
vibrations skyrocket and can kill a crank in short
order. Just like when you tune a guitar, if the
frequency is right, it will vibrate the tuning fork. The
impulses on the crank will do the same thing to the
crank when the frequencies match. This is a very
bad situation to get in.
The natural resonate frequency of a crank
depends on many factors. They are all broken down
to stiffness and mass. The larger the mass, the
lower its resonate frequency will be and the stiffer
the material the higher it will be. Anything you do to
the crank or anything that you bolt to it will change
these 2 things.
A flywheel and the damper itself add mass
to the crank. If you’ve done any lightening, you’ve
reduced mass and changed the resonate frequency.
The material the crank is made from has an effect as
well. A cast crank is not able to sustain as much
torsional vibration as a steel crank, but that does not
make a damper any less important, it also takes less
vibrations to fatigue a cast crank. Crank treatments
also change the resonate frequency.
With all the things that can effect the
resonate frequency of a crankshaft, you should be
able to see that a crankshaft that works over a
relatively wide rpm range is important. Most stock
dampers work well over a wide rpm range, however,
they do have a limit. If you build an engine that will
rev out of this range, you risk excessive torsional
vibrations that could rob power and cause premature
crank failure.

[regor]

^^^^ my head hurts now.... lol...^^^^^

[DragonCypher]

If I had my car here I could possibly have a look at it, but for the moment I only have random pieces of my old engine
Also conveniently I dont have my old laptop either which has the sapporo service manual.

Basically I just wanted to have an 8-rib belt pulley as close to the front of the car as possible, and the one which i modified in CAD was just that, and didn't appear to have any easy way of attaching a standard pulley onto the stock unit
Also does a 4g54 even come with a damper from factory? the pulley I modelled is completely solid and I dont recall pulling anything off the motor that resembled a damper



Regor: CNC lathing was what I was originally thinkin of, but I'm still open to trying another method
Where abouts are these 4 holes you mentioned?

[regor]

hey man

on the front of ur harmonic balancer.. where the big bolt is that holds the hb to the crank...
mine has 4 around it so does my scorp and so does my mate triton...

i would go to a wrecking yard ( somthing like pic a part) and have a wonder around and seeif u can see a 8 rib water pump pully... or u might need to go to the truck wreckers.. i am pretty sure i have seen them around....
then just re drill hole ( if u have to) then use a spacer and bolt it to the hb...
u may have to get it rebalanced... i never did mine but my pully isnt as big as your will be...

and just curiouse how big is ur super charger...
where u mounting it....
cause with mine i had to move alternator to the other side...
and put my super where the alt use to live...

cheers roger

[DragonCypher]

Its an Eaton M90 supercharger.. ~1.4L/rev
Since I plan to mount a 45DCOE weber directly on the back (facing the firewall) it will need to be positioned over the exhaust headers, going to support it on a bracket attached to the exhaust studs, and power steering mounts. They should be strong enough to hold it.
The outlet is ontop, and will go at a right angle over the engine into a sigma turbo style inlet manifold

Also I was able to have a look in my engine bay today, there are 4 bolt holes where the fan attaches to.. is that the HB you're referring to?

The pulley directly on the crank is just the single keyway inside and the rest hollowed out


I plan to use something around 4.8-5" diametre, not 100% important as I've found many different sizes of pulleys to go on the supercharger, so as long as I can match up the PSI to +/- 1 it should be fine.


I was also hoping to keep the standard viscous fan in place, but this means there isnt much room to play with on the standard crank pulley, and an 8rib will not fit on the end without making it smaller
Just had another idea..... what if I used a lathe to remove the 'air con' part of the crank pulley and then kept a flat surface to drill and tap some holes which I can mount a large pulley onto?


-
Chris


PS: (the overall shape of the head was just a dummy up, and will be altered to properly align inlet vs exhaust studs

[regor]

nar i mean on ur main pully...
the on that bolts to ur crank...
hear i drew a pic
i am very sure the there are 4 holes in it with thread in them.. i think they a 10 or 12 ml bolts...

http://i290.photobucket.com/albums/ll26 ... titled.jpg
cheers roger

[amgis_obrut]

that thing is going to get massive amounts of heat soak with the blower over the headers

[DragonCypher]

that thing is going to get massive amounts of heat soak with the blower over the headers

I was hoping to incorporate some sort of heat shield into the mounting bracket to keep the radiating exhaust temp away. Also the fuel flowing through the charger I've heard acts as cooling too, especially compared to compression just air alone.

nar i mean on ur main pully...
the on that bolts to ur crank...
hear i drew a pic
i am very sure the there are 4 holes in it with thread in them.. i think they a 10 or 12 ml bolts...

http://i290.photobucket.com/albums/ll26 ... titled.jpg
cheers roger

You mean this one?


Also as I said theres no room between the end of it and the fan to put something in, but if i took off the air con section and drilled/tapped some holes where necessary it could probably work quite easily
Does yours have a different material for the inside and outside of the pulley as opposed to being completely solid?

[shuggy]

Also the fuel flowing through the charger I've heard acts as cooling too,

untill it boils n causes a vapour build up on idle, like my shitty fuel pump does haha

[amgis_obrut]

that thing is going to get massive amounts of heat soak with the blower over the headers

I was hoping to incorporate some sort of heat shield into the mounting bracket to keep the radiating exhaust temp away. Also the fuel flowing through the charger I've heard acts as cooling too, especially compared to compression just air alone.

nar i mean on ur main pully...
the on that bolts to ur crank...
hear i drew a pic
i am very sure the there are 4 holes in it with thread in them.. i think they a 10 or 12 ml bolts...

http://i290.photobucket.com/albums/ll26 ... titled.jpg
cheers roger

You mean this one?


Also as I said theres no room between the end of it and the fan to put something in, but if i took off the air con section and drilled/tapped some holes where necessary it could probably work quite easily
Does yours have a different material for the inside and outside of the pulley as opposed to being completely solid?

you will need to give the fan the flick


here is the pulley on my sc set up