# [EVDL] How thin can a flywheel be?



## EVDL List (Jul 27, 2007)

G'day All

Helping a bloke with a Datsun ute conversion (1977 1200).

We've a 9" ex-forklift (hydraulics) motor for him, and are going to 
fabricate a new flywheel by welding a disk to a taperlock centre.

When I did mine, I went and scrounged a piece of 5/8 material, that gave 
me plenty to skim off both sides (but I needed the thickness to be able 
to put he steps in to emulate the Honda flywheel).

His Datsun flywheel has no steps, until it reaches the centre recess. 
He's got some 10mm (3/8") plate that could be used for the new flywheel, 
but will that be thick enough?

Thanks

Regards

[Technik] James

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## EVDL List (Jul 27, 2007)

> James Massey wrote:
> >
> > Helping a bloke with a Datsun ute conversion (1977 1200).
> >
> ...


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## EVDL List (Jul 27, 2007)

G'day Martin, Dennis, All

On 13/10/2010 8:02 PM, Martin WINLOW wrote:
>
>


> James Massey wrote:
> >>
> >> Helping a bloke with a Datsun ute conversion (1977 1200).
> >>
> ...


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## EVDL List (Jul 27, 2007)

Since you said fully functional clutch it should be thick enough to not warp under pressure from the throwing bearing

Are you using a stock pressure plate or a performance one?

How are the bearings in the motor?

Can they handle the side load?

Sent from my iPhone



> Martin WINLOW <[email protected]> wrote:
> 
> >
> > On 13 Oct 2010, at 08:17, James Massey wrote:
> ...


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## EVDL List (Jul 27, 2007)

I would not make a flywheel thinner but if you insist ask an automotive
machine shop, they would know better than us. If you are looking to lose
weight I would spend money on an aluminum racing flywheel.

>How are the bearings in the motor?

>Can they handle the side load?


I think you mean end load.
Mark Grasser


>Sent from my iPhone



> Martin WINLOW <[email protected]> wrote:
> 
> >
> > On 13 Oct 2010, at 08:17, James Massey wrote:
> ...


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## EVDL List (Jul 27, 2007)

The 3/8 inch thick plate should work. It is best to use a cold roll chrome 
moly steel plate or a forge flywheel to start with. The center step in some 
flywheels are use to center the crank flange. Some use a steel pin between 
the bolt holes to center the flywheel.

My flywheel in the center was 1/2 inch thick with a centering pin, so the 
flywheel was mill down to 1/2 inch on the back and another 1/16 of a inch on 
the face. The ring gear was remove and turn down the ring gear supporting 
lip.

This was done to balance the flywheel that was design for a external balance 
engine.

Roland





> James Massey wrote:
> 
> Helping a bloke with a Datsun ute conversion (1977 1200). We've a 9"
> ex-forklift (hydraulics) motor for him, and are going to fabricate a new
> ...


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## EVDL List (Jul 27, 2007)

If its standard mild steel you can always heat treat it to harden it. 
Although you don't slip the clutch to get rolling in an EV, so there 
should be minimal wear anyways.




> Roland Wiench wrote:
> 
> >
> > The 3/8 inch thick plate should work. It is best to use a cold roll
> ...


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## EVDL List (Jul 27, 2007)

Your idea to scribe the flywheel to locate the pressure plate(PP) bolt holes
and locating dowels probably won't locate the PP accurately enough. Martin's
idea to concentrically machine the PP's OD flange (if it isn't already
machined so) to fit a step machined in the flywheel is a better option. BTW,
his idea to accurately locate the adapter plate between the motor and the
trany also has a lot of merit (see his blog). People seem to forget or
gloss over this important detail and then wonder why their setup eats
tranys, motor shafts, and couplers. 

On the topic of clutch slippage: the typical diaphragm spring PP(and other
designs too), by design, produces more pressure on the clutch disc
proportional to the RPM..Conversely, this also reduces the pedal pressure
required starting off and at low speed (saves your knee!). This works great
for ICEs where max engine torque is in the middle to upper RPM band. Most
electric motors, however, produce max torque right from the git go. A heavy
duty (racing?) PP with more initial spring pressure might be the solution.

This high RPM extra spring pressure might deform (dish) a too-thin flywheel,
causing all kinds of weirdness.

-- 
View this message in context: http://electric-vehicle-discussion-list.413529.n4.nabble.com/How-thin-can-a-flywheel-be-tp2993221p2994815.html
Sent from the Electric Vehicle Discussion List mailing list archive at Nabble.com.

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## EVDL List (Jul 27, 2007)

> James Massey wrote:
> 
> > ...
> >
> ...


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## EVDL List (Jul 27, 2007)

> EV Convert wrote:
> 
> > On the topic of clutch slippage: the typical diaphragm spring PP(and
> > other
> ...


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## EVDL List (Jul 27, 2007)

My Porsche flywheel had a lip that centered the pressure plate. I got a 
lightened, triple clamping force pressure plate from Kennedy Engineering 
Products.

I did a calculation that if my flywheel/pressure plate was 0.007" off center it 
would create 100 lbs of imbalance force! That would be a lot of vibration. You 
need to be accurate. You can also get your flywheel and pressure plate balanced 
as a unit at a racing machine shop. Mine vibrated on a test spinup, but I 
flipped the pressure plate 180 degrees and that fixed it.




________________________________
From: EV Convert <[email protected]>
To: [email protected]
Sent: Wed, October 13, 2010 11:22:09 PM
Subject: Re: [EVDL] How thin can a flywheel be?


Your idea to scribe the flywheel to locate the pressure plate(PP) bolt holes
and locating dowels probably won't locate the PP accurately enough. Martin's
idea to concentrically machine the PP's OD flange (if it isn't already
machined so) to fit a step machined in the flywheel is a better option. BTW,
his idea to accurately locate the adapter plate between the motor and the
trany also has a lot of merit (see his blog). People seem to forget or
gloss over this important detail and then wonder why their setup eats
tranys, motor shafts, and couplers. 

On the topic of clutch slippage: the typical diaphragm spring PP(and other
designs too), by design, produces more pressure on the clutch disc
proportional to the RPM..Conversely, this also reduces the pedal pressure
required starting off and at low speed (saves your knee!). This works great
for ICEs where max engine torque is in the middle to upper RPM band. Most
electric motors, however, produce max torque right from the git go. A heavy
duty (racing?) PP with more initial spring pressure might be the solution.

This high RPM extra spring pressure might deform (dish) a too-thin flywheel,
causing all kinds of weirdness.



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## EVDL List (Jul 27, 2007)

Hi Martin. The old style coil spring and lever clutches I've seen with this
feature had centrifugally activated rollers to increase the clamping force
on the disc. These were large Mopar V8s. I seem to recall a design that had
fly weights forged into the levers as well.

My memory's a little more fuzzy on the diaphragm spring design. I think,
when engaged, the shallow conical shape of the spring imparts a fly weight
function to the actuating fingers- increasing the clamping force with higher
revs. Someone with more time could probably find a better explanation on
Google. http://www.indiacar.com/infobank/theclutch.htm has some info.

Either way, this feature appears to be not much help to most of us EVers.

Glenn 



> EV Convert wrote:
> 
> > On the topic of clutch slippage: the typical diaphragm spring PP(and
> > other
> ...


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## EVDL List (Jul 27, 2007)

> EV Convert wrote:
> 
> >
> > Hi Martin. The old style coil spring and lever clutches I've seen
> ...


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## EVDL List (Jul 27, 2007)

Hi Glen, and others,
I have been working with automotive clutches since 1968. The flywheel
we always specified stone ground for surface texture and better flatness.
The clutch disk surface friction material varied according to use similar to
brake lining material, and the pressure plate could be diaphragm which had
same pressure at all rpms and was great for making a big show and were using
what I call oil can geometry so it required little pressure to hold the
clutch pedal down at intersections. Or spring and lever type with weights
which slipped more at low engine rpm and became tighter with increased rpm
so it made it hard to stall and easier to slip and save the tires at start,
a much smoother drive "Like a Limo." when combined with an organic clutch
disk facing was easy to drive smoothly and at higher driving rpm slippage
went to zero for good mileage and long clutch life. To me it seemed the
clutch facing material whether organic or metallic was more important a
decision. The last time I had a concern was 6 or 8 years ago when I was
starting 80,000 pounds rolling then double clutching thru 10 gears with
40,000 pounds of liquid in the tank right behind my seat and extending back
about 30 feet. (That was not a diaphragm pressure plate.) I drove Tankers
for a couple years.
I would be more concerned if a not "Forged Steel" would stand the stress of
daily use and localized friction heating with every start, and then stay
together at 10 or 12 th0usand rpm in a malfunction run away or a missed
shift or accidental downshift. a friend downshifted a Corvair Monza at 70
MPH into first gear and shattered the multi plate clutch luckally the
bellhousing stayed together or he would have been badly injured.
Regards,
*Dennis Lee Miles* (Director) *E.V.T.I. inc*.
*www.E-V-T-I-Inc.COM <http://www.e-v-t-i-inc.com/> *(Adviser)*
EVTI-EVAEducation Chapter
*
Phone (863) 944 - 9913
Initial demand (computed by extrapolating the reservations for GM Volt and
Nissan Leaf,) shall exceed 200,000 vehicles in 2010 and 2011. However only
50,000 vehicles will be marketed, so a LARGE demand for Nice Newer
Conversions is predicted!
============================================================



> EV Convert <[email protected]> wrote:
> 
> >
> > Hi Martin. The old style coil spring and lever clutches I've seen with this
> ...


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## EVDL List (Jul 27, 2007)

Ah there's a little bit of the steam punk in all of us. Here's a design
(centerforce ) that accentuates the centrifugal action of the fingers with
extra
flyweights:http://image.chevyhiperformance.com/f/11127549+w750+st0/0812chp_03_z+centerforce_clutch_performance_tips+pressure_plate_design.jpg

Again, this wouldn't help with low RPM slippage . I wonder if this is a
problem, say in your flywheel design, would sinking the clutch cover flange
into the flywheel increase the pressure on the clutch disc? You could easily
mess up the over centering geometry of the design-so you'd have to be
careful.
martinwinlow wrote:
> 
> 
> 
> 
>


> EV Convert wrote:
> >
> >>
> >> Hi Martin. The old style coil spring and lever clutches I've seen
> ...


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