The Ford Barn - View Single Post - The Terry Burtz 5 main bearing engine blocks are back on track.

Terry Burtz, Calif · 10-08-2020, 11:39 PM

Terry, can you give us some details on your forthcoming flywheel? Russ

You may want to look at this page for info on the flywheel.
http://www.modelaengine.com/19-other-parts.html
As I understand this is in the works and may change? 4bangerbob

Thanks Bob. Seems a bit complex. Is there a discussion somewhere that explains the "why" of its construction? It looks like all attempts are made to eliminate any press fitting- ring gear to body, and iron surface to body. Is it balanced? Russ

from the picture shown is appear the construction is such that there is a cast iron disk that is bolted to the main aluminium flywheel using socket head cap screws. I appears in the photo that the cast iron disk extends down to encompass the piolet bearing and mounting flange to the crankshaft. The ring gear is bolted onto the aluminium body, rather then shrunk on?
But the design may well have been revised since the photo was published.
would it be balanced?, I would certainly hope so, The crank and rods are all balanced at the factory from accounted published to date.
I am sure Terry can clarify. 4bangerbob

4bangerbob, you are correct in the description of the flywheel shown in the picture.

Weight of a flywheel means little. What is important is the "polar moment of inertia". The polar moment of inertia is an engineering quantity that takes weight and location into consideration. If the weight of a shaft is concentrated at the center of rotation, it has low inertia and is easy to accelerate. If the same weight is far from the center of rotation, it has high inertia and takes more effort to accelerate. 55 years ago, my job while in college was to calculate the mass properties including polar moments of inertia for the Mayall telescope on Kitt Peak, AZ.

I machined a few 22 pound flywheels like the picture and they were a lot of work. The center and friction surface were machined from a Model A flywheel, and the "bell" to support the ring gear was machined from cast 356 aluminum.
Press fits are difficult to guarantee because aluminum expands or contracts 3 times what steel or iron does during the same temperature change.
Although all parts were a press fit at room temperature, my conscience and fear of something coming loose forced me into making mechanical connections.
The cut down Model A section was bolted with 12 socket head cap screws to the aluminum bell section, and the ring gear was secured with 10-32 UNF bolts and nuts.
Drilling the hardened ring gear for the 10-32 UNF bolts was a challenge, and if I were to do it again, I would have the holes plunged EDM'd.

The new flywheel shown in the videos weighs 30 pounds without the ring gear. It was an engineering sample and machined from steel. Production flywheels will be identical, but made from grey iron.

10-08-2020, 11:39 PM	#191
Terry Burtz, Calif Senior Member Join Date: May 2010 Location: Campbell,CA, USA Posts: 319	Re: The Terry Burtz 5 main bearing engine blocks are back on track. Terry, can you give us some details on your forthcoming flywheel? Russ You may want to look at this page for info on the flywheel. http://www.modelaengine.com/19-other-parts.html As I understand this is in the works and may change? 4bangerbob Thanks Bob. Seems a bit complex. Is there a discussion somewhere that explains the "why" of its construction? It looks like all attempts are made to eliminate any press fitting- ring gear to body, and iron surface to body. Is it balanced? Russ from the picture shown is appear the construction is such that there is a cast iron disk that is bolted to the main aluminium flywheel using socket head cap screws. I appears in the photo that the cast iron disk extends down to encompass the piolet bearing and mounting flange to the crankshaft. The ring gear is bolted onto the aluminium body, rather then shrunk on? But the design may well have been revised since the photo was published. would it be balanced?, I would certainly hope so, The crank and rods are all balanced at the factory from accounted published to date. I am sure Terry can clarify. 4bangerbob 4bangerbob, you are correct in the description of the flywheel shown in the picture. Weight of a flywheel means little. What is important is the "polar moment of inertia". The polar moment of inertia is an engineering quantity that takes weight and location into consideration. If the weight of a shaft is concentrated at the center of rotation, it has low inertia and is easy to accelerate. If the same weight is far from the center of rotation, it has high inertia and takes more effort to accelerate. 55 years ago, my job while in college was to calculate the mass properties including polar moments of inertia for the Mayall telescope on Kitt Peak, AZ. I machined a few 22 pound flywheels like the picture and they were a lot of work. The center and friction surface were machined from a Model A flywheel, and the "bell" to support the ring gear was machined from cast 356 aluminum. Press fits are difficult to guarantee because aluminum expands or contracts 3 times what steel or iron does during the same temperature change. Although all parts were a press fit at room temperature, my conscience and fear of something coming loose forced me into making mechanical connections. The cut down Model A section was bolted with 12 socket head cap screws to the aluminum bell section, and the ring gear was secured with 10-32 UNF bolts and nuts. Drilling the hardened ring gear for the 10-32 UNF bolts was a challenge, and if I were to do it again, I would have the holes plunged EDM'd. The new flywheel shown in the videos weighs 30 pounds without the ring gear. It was an engineering sample and machined from steel. Production flywheels will be identical, but made from grey iron.