Flywheel lightening

[John McEwan]

Anyone have any experience with flywheel lightening on ‘23 or earlier DB. Interested in results or opinions.

[franklinman]

To what purpose? Higher RPMs? (not that good an idea, starter-generator is a limiting factor), Smoother can be obtained by a comprehensive balancing. Curious where you’re going.

[Mark Gregush]

How is the starter-generator a limiting factor? Why would the chain drive be any different then a belt when it comes to RPM? Some Model T and A guys lighten the flywheels, give lower torque at take off but faster increase in RPMs. On board with the balancing. 

[Mattml430]

The theory behind Pete and Myself doing it is not so much for better engine performance but for smoother gear changes. Pete has driven a car with this done and said it was so much better changing gear. It will still be a while until I can let you know how this will go but I’ll report back on how it goes. 

[John McEwan]

14 hours ago, franklinman said:

To what purpose? Higher RPMs? (not that good an idea, starter-generator is a limiting factor), Smoother can be obtained by a comprehensive balancing. Curious where you’re going.

I already have much smoother via my rubber engine mounts. Looking at quicker acceleration and better gear changes. I am in the middle of gear ratio changes and thought while the gearbox is out I might take off a couple of kg’s.

[Pete K.]

The Ford flywheel can be lightened by shaving the driving face of the flywheel and they also need to cut the same depth for the single disc pressure plate ass'y. I'm still trying to wrap my head around a Dodge flywheel with the multiple disc clutch, which I think maybe the years you listed have the Multi-disc set up like my '25 has?

 A lightened flywheel has nothing to do with increasing the RPM's. The operation of the fuel given to the engine determines that.  Lightening will give a bit more pep, "off-the-line". The down side may be to almost stop, to down shift more often when taking corner streets and the like. Good luck with your hard work.

Edited November 12, 2020 by Pete K.
added text (see edit history)

[Minibago]

As I see it the reason for the heavy flywheel is to help with torque, the downside is that this very very heavy flywheel hangs off the end of a crankshaft that is 100 years old. The most common result is leaving the car in top gear too long because the lower gears are very low. This lugging in top gear often causes the crank pin on the main bearing to break between the two front cylinders. The recommendation from the late Ralph Provan was to machine an inch and a half off the depth of the flywheel outer ring. Not everyone agreed. It will change the driveability due to the loss of torque but the compensation is to fit the higher ration first and second gears Ralph had manufactured. (Not so easy now) My thoughts for what they are worth. Just my opinion.

[TonyAus]

With regard to easier gear changing I can see a problem of logic.  From practical experience the technique for changing up is to slow the gearbox input shaft.  This can be achieved by releasing the clutch, backing off the throttle, engaging neutral (all in one action) and re-engaging the clutch.  After the flywheel has slowed the engine and the still connected gearbox input shaft the clutch can be disengaged/re-engaged and the upward gearshift made without clashing the gears.  To change down the input shaft must be speeded up by revving the engine quickly while the gearbox is in neutral.

In theory, if the flywheel is lightened changing down should be easier as the engine will pick up revs quicker.  However it will make changing up harder as the engine and input shaft will take more time to slow down.  You win some and lose some with a net result of zero.

Please feel free to correct me on this matter.

 

        

[nearchoclatetown]

31 minutes ago, TonyAus said:

  However it will make changing up harder as the engine and input shaft will take more time to slow down. 

 

        

I am not an engineer, BUT I think this statement is backward. The heavy flywheel keeps the crank spinning. that is why the engine speeds up faster with a light flywheel. If it speeds up faster it SHOULD slow down faster. That is why a light flywheel hurts on hills. It doesn't have the momentum to keep going. If I remember right Matt removed about 2 kilos, 4.4 pounds to us USers. If you weighed a stock flywheel and did a percentage he didn't take off very much. I am much more familiar with slow four DBs then sixes, but that is the reason to use proper weight steam cylinder oil in the old transmissions. It helps slow down the shafts to shift rather then rely on syncros which hadn't been invented yet. I'm going to wait for Matt to get this sucker running and on the road. If his experiment doesn't work I think he will let us know. At the speed he is working it should be about 2 or 3 Weeks, no pun intended.

[RichBad]

Agree - there’s theory and reality, not always the same - I like to understand the theory but put my beliefs in reality and experience - you wouldn’t want to fly an aeroplane that’s never been tested;)).

 

You cant beat real world results (although need to be careful of other variables too such as oil viscosity, gear ratios, four vs 6, vehicle weight etc).

[MikeC5]

I would think the rotational inertia of the flywheel would influence how quickly the engine can accelerate (how fast can rpm rise for a given input toque).  It's been a long time since I studied this stuff but it seems to intuitively make sense to me.  Doing a little on-line searching, I found "rotational inertia has an impact when you're power limited (in terms of engine power or braking power), but becomes non-important when you're traction limited. The reason why rotational inertia is more important for acceleration is that the average street car is power limited under acceleration and traction limited under braking. And just to be clear, lighter wheels an tires and such will still help"  As for downshifting, I would think the engine would decelerate faster with a lighter flywheel which may help downshifting.  Keep in mind though, the transmission on these has the layshaft disconnected in top gear and we hope the viscosity of the trans oil 'drags it along' so downshifting can happen (main shaft and layshaft gear must match speed to downshift).  

[TonyAus]

With regard to downshifting , engaging neutral brings the main shaft and layshaft into mesh relatively easily because of the oil drag.  Revving the engine at this point raises the speed (inertia) of both shafts.  As the lower gear is selected there will be a disparity when the layshaft starts to slow.  However, the higher the layshaft inertia the less this disparity will be and the better the chance of a silent mesh of gears.  At least this is my theory as it appears to work . 

[Alan Cutler]

I was thinking gyroscopic effects and harmonization will be lost...causing both faster engine speed and slow down, along with more pronounced vibration. 

[RichBad]

Another benefit is you can fit the flywheel without over exerting yourself (or perhaps I’ve become too much of a desk jockey)

[Mattml430]

1 hour ago, RichBad said:

Another benefit is you can fit the flywheel without over exerting yourself (or perhaps I’ve become too much of a desk jockey)

Still over 20kg even after lightening it. That’s without the pressure plate. 
They are bloody heavy. 
It will be interesting to see how it goes. The problem is I have never driven the roadster so I can only compare it to the sedan. Also have done a few other engine improvements to try make it run a little better. 
 

[Mark Gregush]

I have not weighted the 1928 Chevrolet flywheel but guys take quite a bit off to install a Holden type single disk clutch. Same with Model A's. While some do reduce the Model A weight from about 63-65 LBS (28.5kg approx) by 20 LBS (9.07kg approx) or more esp. the ones that install the V8 clutch they all loose the low end lugging power but gain on faster response.  I understand that the mass was used to negate uneven inherent firing in the 4s and because of the roads and speeds these cars were driven back in the day.

Unlike the Ford or Chevrolet where the clutch pressure plate mounted to the flange on the flywheel, the multi disk clutch disk mounts/rides on the pins so the rim/flange is there for weight.

Balancing the revolving parts, including the gears in front, crankshaft, flywheel and the clutch pressure plates that ride on the pins, would help greatly along with pistons and rods being within a few grams of each other. When we balance the Model A parts, everything from the pulley in front to the pressure plate in back is balanced as a unit. 

[Alan Cutler]

6 minutes ago, Mark Gregush said:

I have not weighted the 1928 Chevrolet flywheel but guys take quite a bit off to install a Holden type single disk clutch. Same with Model A's. While some do reduce the Model A weight from about 63-65 LBS (28.5kg approx) by 20 LBS (9.07kg approx) or more esp. the ones that install the V8 clutch they all loose the low end lugging power but gain on faster response.  I understand that the mass was used to negate uneven inherent firing in the 4s and because of the roads and speeds these cars were driven back in the day.

Unlike the Ford or Chevrolet where the clutch pressure plate mounted to the flange on the flywheel, the multi disk clutch disk mounts/rides on the pins so the rim/flange is there for weight.

Balancing the revolving parts, including the gears in front, crankshaft, flywheel and the clutch pressure plates that ride on the pins, would help greatly along with pistons and rods being within a few grams of each other. When we balance the Model A parts, everything from the pulley in front to the pressure plate in back is balanced as a unit. 

 

We do the same, balance from pully to plates...however, Mattml430 did not mention a rebalance and only mentioned the weight reduction, therefore, my comment about harmonization...he will loss the original balance and may have additional vibration after the weight reduction if not rebalanced to that engines particular set up...

[Mattml430]

2 hours ago, Surf City '38 said:

 

We do the same, balance from pully to plates...however, Mattml430 did not mention a rebalance and only mentioned the weight reduction, therefore, my comment about harmonization...he will loss the original balance and may have additional vibration after the weight reduction if not rebalanced to that engines particular set up...

I’m taking the flywheels in next week to be rebalanced along with the pressure plate. We actually organised this yesterday. I will also be balancing everything else I can to get it a smooth running as possible. 
while I had the flywheel on my lathe I spun it up to 2000 rpm. It seemed to be as smooth as silk with zero vibration but I’ll still get it balanced to be sure. 

Edited November 13, 2020 by Mattml430 (see edit history)

[nearchoclatetown]

Matt, in the stuff I scanned for the DBC website there is information about how close the Victory and Senior engines were balanced. It is in the dealer bulletins.  

[Mark Gregush]

1 hour ago, Mattml430 said:

I’m taking the flywheels in next week to be rebalanced along with the pressure plate. We actually organised this yesterday. I will also be balancing everything else I can to get it a smooth running as possible. 
while I had the flywheel on my lathe I spun it up to 2000 rpm. It seemed to be as smooth as silk with zero vibration but I’ll still get it balanced to be sure. 

The whole revolving assembly should be balanced as a unit esp. with an engine that does not have a counter balanced crank. 

[MikeC5]

You must have a good sized lathe Matt!  

[Mattml430]

6 hours ago, MikeC5 said:

You must have a good sized lathe Matt!  

Yes it’s a bit of a monster. It’s a Hitachi Seiki 4D Turret lathe. 1975 Japenese built. I found it on eBay one night and bid on it and won it for $999. It’s weights about 3t. It’s extremely accurate to less than 1 thou. I use it almost everyday for something. 
It spun the flywheel with ease when going from 200 to 2000 rpm
I love it like we love our old dodge’s 😂🤣

[Mattml430]

12 hours ago, nearchoclatetown said:

Matt, in the stuff I scanned for the DBC website there is information about how close the Victory and Senior engines were balanced. It is in the dealer bulletins.  

Thanks Doug I’ll try and look it up. 

[Fossil]

On 11/12/2020 at 3:30 PM, nearchoclatetown said:

but that is the reason to use proper weight steam cylinder oil in the old transmissions.

  I've read this before but our 30 DeSoto CF-8 doesn't seem to agree. When the tranny is cold and the oil stiff it is nearly impossible to shift it without gear clash. With or without double clutching. On the other hand after driving and warming up the transmission it shifts very nicely with no gear clash. I'm seriously considering 90-140 to see how that works.

  As far as lightening the flywheel it would seem that a lighter flywheel would tend to loose RPM's faster when the throttle were closed thus making shifts smoother. On the other hand it seems like the engine wouldn't run as smooth. 

[nearchoclatetown]

If you reread the original discussion and my comment it was about slow fours. I do not know what oil is required for the much later 8 cylinder cars. I THINK they get hypoid oil which is not recommended for the straight cut gears. I wish I had one so I would have reason to find out. 

[Ron Lawson]

On 11/20/2020 at 8:04 AM, Fossil said:

  I've read this before but our 30 DeSoto CF-8 doesn't seem to agree. When the tranny is cold and the oil stiff it is nearly impossible to shift it without gear clash. With or without double clutching. On the other hand after driving and warming up the transmission it shifts very nicely with no gear clash. I'm seriously considering 90-140 to see how that works.

  As far as lightening the flywheel it would seem that a lighter flywheel would tend to loose RPM's faster when the throttle were closed thus making shifts smoother. On the other hand it seems like the engine wouldn't run as smooth. 

There is so much "overlap' on a Straight Eight engine I don't think that taking 2 or 3 pounds off the fly wheel would cause rough idling or at cruising speeds