Different Type of Flywheel Question

MarkV

New member
The sprint track that I run at has a twist on the Box Stock Project rules - we're required to run a billet steel flywheel. This was originally done to help keep the cost of an engine build down. Our season is coming to an end this Sunday during our final race, and several of us are going to propose that we start running aluminum flywheels next season in an effort to get more aligned with the BSP rules and to make it easier for anyone with a Clone engine running BSP rules to come and race with us at our track in Katy, Texas.

I know the subject of aluminum flywheels has come up many times in the past, but my question is more around the power required to spin any of these due to the wind resistance of the machined cooling fins while confined within the flywheel tin. Is there a considerable difference in the fin design from one manufacturer to another, meaning are they all just hook shaped and designed to be pleasing to the eye, or has anyone done their homework and made a fin that doesn't rob a lot of power just beating a hole in the air. The original plastic fins may have been designed to pump the air at 3600 RPM, but I would question their efficiency of moving that air at twice the RPM. Obviously, zero fins have less resistance than some fins, which is why the Jr. Dragster guys run fin-less, but sprint engines do require the cooling breeze.

I guess some sort of simplified dyno comparison done while spinning all the competing aluminum models would be required. I can see just a simple shaft turning the wheel while it's inside a blower housing is all that would be required, and doing it that way removes all the variables that a dyno run with an engine doing the turning would cause. Differences in ignition timing alone from the location of the magnets in different wheels could cause enough power difference to throw off the results. Has anyone done this sort of simple comparison before and, if so, could you share your results?

Thanks in advance for any responses!

Mark
 

JPR57

Site Supporter
The fins on todays Billet Aluminum flywheels are designed to have much less air drag than any stock fin design. If you go to our web site www.arcracing.com an enter the blog at the top of the page we have done numerous testing with the different flywheels a while back,2008-09. True, magnet design, weight and balance will produce more power than a stock or steel wheel but the fin design plays just as much role in reducing high RPM drag. There is a reason why our fins are shaped like they are. They move enough air to cool the engine, while provideing minimal air drag which will rob power at high RPM. I will also add that taping the blower housing will reduce air drag with any flywheel and help free up power, but in some cases it could reduce power. I have seen a few people tape up the recoil starter, then put tape on every possible entrance to the blower housing so no air can get in or out. This will cause the flywheel to produce a negative pressure inside the housing causing an even greater drag on the engine. Taping up the recoil starter is fine and we do it all the time, but leave a small area somewhere for air to enter or exit.
 

DynoDon

Moderator
BSP rules do not exist anymore. It is now considered just Box Stock. Box Stock Project is the title of Jim Sims Business that he started when the clone came along. Jim played a huge role in the development of the clone as a racing entity and it was originally considered BSP. Then the rules organizers changed it to Box Stock. Now to your question. JPR57 gave you an excellent explanation as to drag at High rpm. You also need to consider this about flywheels. Heavy is a momentum wheel and light is a quick rising rpm wheel. If you race on a track that has no lifting off the throttle then a heavy wheel ( steel ) would be a good wheel to have. If you need to lift out of the throttle, then you may want a light wheel.
 

rab3rd

New member
Mark, I am a member out at Katy and its already been decided that we will be going to the aluminum flywheel next year. It was announced in the drivers meeting two races ago. They initial thought from the board is that it will be which ever flywheel ARC sells the most. The rules that GCKI follows are almost fully AKRA rules with the flywheel exception you listed.

Rob #5
 

MarkV

New member
Ah! I didn't make that race, and I don't believe the GCKI website forums reflect that proposed change (I'll have to start a thread!) Thanks for all replies!
 

Yakattack

Member
Now explain how if the housing is taped up and it induces a negative pressure it robs power?
I know in HVAC if the blower motor cannot move any air...it is not,doing any work...there for the amps go down because it is not doing any work so it is using less energy! Actually it is not doing anything except using energy to do nothing?
 

JPR57

Site Supporter
You can not totally seal off a blower housing on the engine. Even if you could the engine would have a melt down in a few minutes. You will need some air to blow across the head/block area to keep it cool, one of reasons for cooling fins. The housing will need an entrance and exit for the air. One opening can not act as both. Your HVAC blower motors have an entrance for air and an exit for air right? It does not use the same hole for intake and exhaust. Got an experiment for you. Take standard household fan, preferably a small desk top fan and remove any brackets that are attached to the cage so you have just the fan in its cage on the table. Get a medium to large trash bag and place the fan inside the bag with the face out. This will represent the flywheel in a blower housing that is "somewhat" sealed. Turn the fan on the high setting, then close and open the bag to listen to it speed up when the bag is open and some air can get to the back side and slow down when you seal off the back and sides not allowing air to inter and exit the blades like they were designed to do. Also move the bags opening around the front and side of the fans cage to listen to the different RPMs. You can also use tape but the bag trick is quicker.
 

Devil-D-Dawg

New member
What is the story with the ultralight ARC flywheels? I am thinking they would be usefull in a twisty road course? Am I correct? I don't need a momentum wheel - I turn both directions.

I understand they aren't akra legal, but I am racing in POPTOP and there isn't a flywheel rule.
 

JPR57

Site Supporter
Yes. The 6602 ultra light wheel is the lightest wheel on the market at 1.7lbs and can be used with or without the stock plastic fins. It will greatly increase acceleration. Our web site will explain more.
 

Devil-D-Dawg

New member
Yes. The 6602 ultra light wheel is the lightest wheel on the market at 1.7lbs and can be used with or without the stock plastic fins. It will greatly increase acceleration. Our web site will explain more.

What about the part suggesting a balanced crankshaft. The ARC model carries too much baggage (need to remove cam rivets / $$$ / need to use a starter) Will the 6602 work with a standard honda crank or will it vibrate you out of your seat?
 

JPR57

Site Supporter
The 6602 will fit the Honda shaft. No it will not viberate you out of the seat. It is recommended for a balanced assembly not required for one.
 

sCREamnClones

New member
You can not totally seal off a blower housing on the engine. Even if you could the engine would have a melt down in a few minutes. You will need some air to blow across the head/block area to keep it cool, one of reasons for cooling fins. The housing will need an entrance and exit for the air. One opening can not act as both. Your HVAC blower motors have an entrance for air and an exit for air right? It does not use the same hole for intake and exhaust. Got an experiment for you. Take standard household fan, preferably a small desk top fan and remove any brackets that are attached to the cage so you have just the fan in its cage on the table. Get a medium to large trash bag and place the fan inside the bag with the face out. This will represent the flywheel in a blower housing that is "somewhat" sealed. Turn the fan on the high setting, then close and open the bag to listen to it speed up when the bag is open and some air can get to the back side and slow down when you seal off the back and sides not allowing air to inter and exit the blades like they were designed to do. Also move the bags opening around the front and side of the fans cage to listen to the different RPMs. You can also use tape but the bag trick is quicker.

Very good 'picture' Jody! One thing missing in this discussion (however) and that is the 'need' for Heat and Cooling. This thread appears too address the +/- of Power, but the fins do have a more definitive purpose...obvious too most! I just choose too note 'this' so that SOMEBODY does not read this and enter into an immediate 'melt-down' with their newly aquired self-purchased hi-hp x-mas present! :)
 
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